Chromalox Technical Overview

Technical

Technical Overview  This technical section presents heat loss fundamentals along with basic problems and solutions. Data, charts and graphics are provided to aid in solving virtually any heating application using electric resistance type heaters. Most materials, whether solid, liquid or gas may be readily heated with electric resistance heaters by conduction, convection or radiation. The following are three basic requirements, which when met, leave only the selection of type and number of electric heaters best suited for the application. 1. Final Temperat Temperature ure Desired — Electric resistance heaters of the enclosed sheath type can be operated successfully over a wide range of temperatures from -300°F (cryogenic) to approximately 1500°F. For operating temperatures outside this range, contact the nearest Chromalox Application Engineering Sales office or factory. 2. Sheath Material Material Required Required — Copper is commonly used as the sheath material for water applications, steel for oils, and Stainless Steel or INCOLOY® for corrosive solutions and high temperature air heating. This catalog gives considerable help in choosing the proper sheath material for many common materials. Additional help is available from the nearest Chromalox Application Engineering Sales office or factory. 3. Watt Density Density Permitted Permitted — Watt density is the heat energy emanating from each square inch of heated surface of a heater or element. Some materials such as water, vegetable oils and salt baths can withstand a high watt density, while others such as petroleum oils or sugar syrups must use lower watt densities. These liquids do not readily absorb or conduct the heat being generated. If the watt density is too high, carbonization or overheating may damage the heating equipment or material being heated. Recommended maximum ratings for various materials and temperature conditions are included in this section. All heaters in this catalog have the watt density specified for standard heater ratings. After resolving the above requirements, choose the type of heater best suited to the application. For example, a tank of water may be heated by direct immersion heaters, by clamp-on strip, ring or tubular heaters or a side-arm circulation heater. The choice will depend on the process, considerations, available space both inside and outside, economy, maintenance, etc.

General Guidelines for Heater Type, Type, Selection & Application  Heated Media

LIQUIDS For highest efficiency and fastest response, use direct immersion ® Flange heaters ® Screw plug heaters ® Over-the-side heaters ® Circulation heaters—side-arm, in-line or booster applications

SOLIDS For dies, molds, platens, soft metals, use ® Clamp-on types—strips or tubular elements ® Cartridge heaters ® Cast-in heaters ® Radiant heaters ® Melting pots

LIQUIDS When conditions do not permit direct immersion heaters, use ® Clamp-on types—strips, tubular, tubular, cast-in, heating cable ® Radiant heaters ® Heat transfer systems ® Electric hot water or steam boilers

GASES For gases in ducts, ovens or pipelines use ® Strip or Finstrip® elements ® Tubular or Fintube® elements ® Duct heaters ® Circulation heaters ® Flange or screw plug heaters in pipeline systems

Application Design Criteria

Provide enough kW and ® Closely match connected load to application requirements for best product and process control ® Avoid installing excess capacity over the base load and required safety factor

Design for long life by ® Keeping sheath temperatures well below maximum recommendations ® Using lowest line voltage practical where choices are available

Ensure safe operating conditions by providing ® Heater equipment with suitable operating control and overheat protection devices ® Process being heated with .suitable controls ® Electrical wiring in accordance with all national and local codes ® Protection for personnel by using insulation, guards, grilles and warning labels

Protect equipment from ® Physical damage ® Terminal contamination ®  Corrosion ® Excessive wiring and terminal temperatures

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I-1

Technical

Table of Contents Heat Loss Lo ss Calculations Ca lculations & Heater Selection Se lection .......... ..................... ...................... ...................... ...................... ...................... ..............I-5–35 ...I-5–35 Determining Heat Energy Requirements ............................ ......................................... .......................... .......................... .......................... ...................... ......... I-6–9 Basic Heat Energy Equations............................. ........................................ ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... ................I-7 ......I-7 General Information ......... .................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................I-6 ........I-6 Total Energy Requirements ...................................................................................................................................I-7 Typical Steps in Heat Loss Calculations ........... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................I-8 ........I-8 Heat Loss Calculations & Examples Air & Gas Heating - Atmospheric Pressure.......... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ............. ..I-16 I-16 - Cryogenic Applications .......... .................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ............ I-20 - Oven Heating.......... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ................I-20 ......I-20 - Pressure Drop for Process Air Heaters ...................... ................................. ..................... .................... ..................... ..................... ................I-20 ......I-20 - Pressurized with Circulation Heaters .............. ........................ ..................... ..................... ..................... ..................... .................... ..................I-22 ........I-22 ® - Strip and Finstrip Heater Selection .......... .................... ..................... ..................... .................... ..................... ..................... ..................... ............. ..I-17 I-17 Determining Maximum Sheath & Chamber Temperatures ............................ ...................................... .................... ..................... ..................... ..................... ............. ..I-22 I-22 Comfort Heating .......... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ............ I-12 Heat Exchangers - Heating & Cooling .......... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ....................I-27 .........I-27 Liquid Heating - General Applications .......... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ............ I-8 Oil Heating with Circulation Heaters ............................. ....................................... ..................... ..................... .................... ..................... ..................... ..................... ..................... ................I-9 ......I-9 Pipe & Tank Tracing ............................................................................................................................................I-11 Soft Metal Heating........... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ....................I-9 ..........I-9 Solids Heating - Platens, Dies & Molds ............. ........................ ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .............. ....I-26 I-26 Steam Heating .......... .................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ...................I-23–25 ........I-23–25 Water Heating with Circulation Heaters ........................... ...................................... ..................... .................... ..................... ..................... ..................... ..................... .................... ............. ...I-9 I-9 Heat Transfer Fundamentals ............ ......................... .......................... .......................... .......................... .......................... .......................... .......................... ................ ... I-5 Heater Selection Guidelines ............ ......................... .......................... .......................... .......................... .......................... .......................... .......................... ...............I-13 ..I-13 Air Heating Applications .......... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... .............. ...I-16–22 I-16–22 Clamp-On Heating Applications.......... .................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ....................I-13 .........I-13 Liquid Heating Applications........... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .............. ....I-14 I-14 Oil Heating Applications .......... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ....................I-15 .........I-15 Radiant Infrared Heating...... Heating................... .......................... .......................... .......................... .......................... .......................... .......................... ..................... ........ I-28–35 Infrared Comfort Heating - Indoor & Outdoor ..................... ............................... .................... ..................... ..................... ..................... ..................... .................... ..................I-35 ........I-35 Infrared Source Evaluations .......... .................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .............. ....I-29 I-29 Infrared Theory ......... .................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ............. ..I-28 I-28 Process Heating Applications ......... .................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... .................I-30–34 .......I-30–34 Curing & Baking Applications........ Applications................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ................I-33 ......I-33 Drying Applications ......... .................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ....................I-32 .........I-32 Product Heating Applications .......... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .............. ....I-32 I-32 View Factors for Flat Panels .......... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ................I-34 ......I-34 Radiant Oven Example ........... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ............ I-34 Thermodynamic Properties - Terminology & Constants ............ ......................... .......................... .......................... .......................... ....................... .......... I-5 Watt Density Determination ............. .......................... .......................... .......................... .......................... .......................... .......................... .......................... ...............I-13 ..I-13

Electrical Wiring Theory .......................... ..................................... ...................... ...................... ...................... ..................... ................... ......... I-36–39 Electrical Fundamentals & Ohm’ Ohm’ss Law ............. .......................... .......................... .......................... .......................... .......................... .......................... ...............I-36 ..I-36 Field Wiring - Size & Selection ........................ ..................................... .......................... .......................... .......................... .......................... ..........................I-39 .............I-39 Three Phase Wiring & Calculations .............. ............................ ........................... .......................... .......................... .......................... ......................... ............ I-36–37 Wiring Diagrams & Methods .................................... ................................................. .......................... .......................... .......................... .......................... .................I-37 ....I-37 Wiring Practices for Electric Heaters ............ .......................... ........................... .......................... .......................... .......................... .......................... .................I-38 ....I-38

I-2

Technical

Table of Contents (cont’d.) Reference Data .......... ..................... ...................... ..................... ..................... ...................... ...................... ...................... ...................... ............. .. I-40–67 Control Systems Selection Guidelines............. .......................... .......................... .......................... .......................... .......................... ........................ ........... I-59–67 S ys tem s Co nsiderations .......... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ...................I-5 ........I-5 S ys tem C om ponent s ......... .................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... .....................I ..........I-5 -5 -6 Temperature or P rocess Con troll trollers ers ......... .................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... ..................... ........... I-6 Ov ertempe rature Co ntrols (H igh Lim it Controls) .......... .................... .................... ..................... ..................... ..................... ..................... .................... ..................... .............. ... I-6 Po we r Con trols .......... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... ..................... ........... I-6 Po we r Con trol Pa nels ........... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ............ .. I-6 Corrosion Guidelines for Sheath Materials in Various Heated Media ............................ ......................................... ........................ ........... I-48–54 Types of Co rr rrosion osion .......... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... .................I-4 .......I-4 S heath S election P rocess .......... .................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... .................I-4 .......I-4 Tables Tabl es of Com mo n Heated Media ......... .................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... .......... I-4 Engineering Constants & Conversions ................. .............................. .......................... .......................... .......................... .......................... .................... ....... I-46–47 Hazardous Locations & Chromalox Electric Heaters ............. .......................... .......................... .......................... .......................... .........................I-56 ............I-56 Hazardous Locations & Electric Heating Applications ............. .......................... .......................... .......................... .......................... .................. ..... I-57–58 Clas sifi cation & Groups ......... .................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... .....................I-5 ..........I-5 Division Loc ations .......... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... .................I-5 .......I-5 Temperature R atings for C lass I & II ......... .................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... ..................... ........... I-5 NEMA Electrical Enclosures & Chromalox Equivalents ............ ......................... .......................... .......................... .......................... .......................I-55 ..........I-55 Physical & Thermodynamic Properties of Materials ............................ ......................................... .......................... .......................... .................. ..... I-41–45  A ir - Dry ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. I-4  A ir - M ois t ...... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. I-4 Co mm on Gas es at Cry og enic Tem Tem peratures .................... .............................. ..................... ..................... ..................... ..................... .................... ..................... .....................I-4 ..........I-4 Co mm on Ga se s ......... .................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... ..................... ........... I-4 Co mm on Liquids ........... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ...................I-4 ........I-4 Me tals - Liquid .......... .................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... .............. ... I-4 Me tals - S olid ............................. ....................................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... .................I-4 .......I-4 No n-M etallic S olids ......... .................... ..................... ..................... ..................... .................... ..................... ..................... ..................... ..................... .................... ..................... ..................... .................I-4 .......I-4 Pipe Specifications ............. .......................... .......................... .......................... .......................... .......................... .......................... .......................... .........................I-40 ............I-40 Pressure Conversions ............ ......................... .......................... .......................... .......................... .......................... .......................... .......................... .......................I-46 ..........I-46 Pressure-Temperature Pressure-T emperature Ratings for Standard Catalog Heaters ................................ ............................................. .......................... .....................I-40 ........I-40 Temperature Conversions .............. ........................... .......................... .......................... .......................... .......................... .......................... .......................... ................I-46 ...I-46

Graphs .......... ..................... ...................... ...................... ..................... ..................... ...................... ...................... ...................... ...................... ............. .. I-10–26 Graph -

GA DHTB G1 S G1 S G1 0 6 S G1 0 7 S G1 0 8 S G1 S3 G1 S G1 S G1 S G1 S G1 S G1 S G1 S G1 S G1 S G1 5 1 G1 5 2 -

AD H and AD HT Ter Terminal minal Box Temperatures .......... .................... .................... ..................... ..................... ..................... ..................... ..................... ........... I-2 S tr trip ip Heater Heater (C hr hrome ome S heath) Air Heati Heating ng ... ...... ...... ...... ...... ...... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ...... ...... .....I-1 ..I-1 S tr trip ip Heater Air Heati Heating ng – S el electi ection on of W att Density Density ... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ...... ...... .....I-1 ..I-1 F in s t rip  Heater Air Heating – S election of Watt Den sity ............. ........................ ..................... .................... ..................... .....................I-1 ..........I-1 F in s t rip  ( Ir Iron on S heath) Air Heat ing ............ ...................... .................... ..................... ..................... ..................... ..................... .................... ..................... .............. ... I-1 F in s t rip  ( Ch rome S heath) Air Heating ........... ..................... ..................... ..................... .................... ..................... ..................... ..................... ...................I-1 ........I-1 Airr He Ai Heat atiing – CAB an andd Fi Finstr nstriip  Press ure Drop Drop Curv es .............................. ........................................ ..................... ..................... ............... ..... I-2 Heat Los ses fr from om W ater Surfaces .... ....... ...... ...... ...... ...... ..... ..... ..... ..... ...... ...... ...... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ... I-1 S urf urface ace Temper Temperatur atures es of Oil Immersi Immersion on Blade Blade Heater Heaterss ...... ........ ..... ...... ...... ...... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ...... ...... ...... ...... ... I-1 Heat Losses fr from om U ni ninsula nsulated ted S urf urfaces aces ....... .......... ...... ...... ...... ...... ...... ...... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ... I-1 Heat L osses fr from om Insulat nsulated ed S urf urfaces aces .... ....... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ... I-1 Heat Losses from Oil Oil & Paraffi Paraffi n Surfaces .. ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ... I-1 Heat Losses from Molten Molten Metal S urf urfaces aces ....... ......... ..... ..... ..... ...... ...... ...... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ... I-1 Clamp-On S tri tripp Heaters .... ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ......I-1 ..I-1 S tr trip ip Heater (Ir (Iron S heath heath)) Air Heating Heating ... ...... ...... ...... ..... ..... ..... ..... ...... ...... ...... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ...... ...... ...... ...... ...... ...... ..... ..... ...... ... I-1 Tubular Heater Air Heating .... ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ......I-1 ..I-1 F in t u b e  & Tubular Air Heating (1 Fps ) ........................... ...................................... ..................... .................... ..................... ..................... ..................... ........... I-1 F in t u b e  & Tubular Air Heating (4 Fps ) ........................... ...................................... ..................... .................... ..................... ..................... ..................... ........... I-1 I-3

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Technical

Table of Contents - G1 5 3 - G1 5 4 - G1 5 5 - G1 5 6 - G1 S - G1 S - G1 S1 - G2 - G2 -2 - G2 ADH - G2 A - G2 - G2

cont’d.)

Fintube  & Tubular Air Heating ( 9 Fps ) .......................................................................................... I-1 Fintube  & Tubular Air Heating (1 6 Fps ) ......................................................................................... I-1 Fintube  & Tubular Air Heating (2 5 Fps ) ......................................................................................... I-1 Fintube  & Tubular Air Heating (3 6 Fps ) ......................................................................................... I-1 Clamp-On Tubular Heaters ..............................................................................................................I-1 Air Heating.......................................................................................................................................I-1 A ir H ea tin g – F in tu be  P ress ure Drop C urves .................................................................................I-2 Cartridge - S uggested Watt Density Limits for Optimum L ife .........................................................IAir Heating - TDH Pressure Drop C urves ........................................................................................I-2 Air Heating - ADH P ressure Drop Curves ........................................................................................I-2 Cartridge - Maximum W att Density vs. Platen Temperature ............................................................I-2 Circulation - Heat R equired for Oil Heating ....................................................................................... ICirculation - S heath Temperature vs. Mass Velocity ........................................................................I-2

Tables & Charts .....................................................................................................I-9–35 - B oos ter H um idifi cation Table .......................................................................................................... I-2 Air Heating Boilers - Feed Wat er Temperature vs . k W required per Lb /S team .................................................................I-2 Circulation Heaters - Free Internal Cros s S ectional A rea .................................................................................................. I-2 - Temp erature R ise vs . W ater Flow .....................................................................................................I-9 Clamp-On Heaters - S trip H eater No mo graph .................................................................................................................I-1 Comfort Heating - Co mf ort Heating Ch art ....................................................................................................................I-1 Heat Exchangers - S team Pres sure Factor .................................................................................................................. I-2 Immersion Heating - Oil Heat ing W att Dens ity Gu ide .......................................................................................................I-1 - S ug ges ted Allowab le W att Dens ities for Liquids ............................................................................. I-1 - Typical Vis cos ities of Oils................................................................................................................I-1 - V is co sity C on v ers ion C ha rt ..... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. I-1 Infrared Heating - A bs orption Bands of Plas tics ..........................................................................................................I-3 - Approxima te Em iss ivities of V arious S urfaces ................................................................................I-2 - Ch aracteristics of Infrared S ources ................................................................................................ I-2 - Es timat ing Infrared W R equirements f or Drying ...........................................................................I-3 - Es timat ing Time/Tem perature .........................................................................................................I-3 - Estim ating Total k W for Product Heat ing ....................................................................................... I-3 - Estimating W att Density Requirements for C uring or Bak ing ..........................................................I-3 - Intens ity vs . Sp acing - Point & L ine Infrared S ources..................................................................... I-3 - Patt ern Areas for Rad iant Infrared Com fort Heating .......................................................................I-3 - P ercent Increment Ra diant Energ y Output ......................................................................................I-2 - Ra diation Intensities ....................................................................................................................... I-3 - S pectral Distribution of Black Bodies ..............................................................................................I-2 - Time/Tem perature R elationships ....................................................................................................I-3 - V iew Factor f or Two Pa rallel S ources ..............................................................................................I-3 - Heat Los ses from M etal Pipe S urfaces ...........................................................................................I-1 Pipe Tracing - Thermal Cond uctivity of P ipe Ins ulation ......................................................................................... I-1 - S aturated S team Therm ody nam ic Properties................................................................................. I-2 Steam Heating - S uperheating S team No mo graph ....................................................................................................I-2 Tank Tracing - Heat Los ses from Insulated M etal Tank s.........................................................................................I-1

Thermal Systems Glossary ...................................................................................... I-68–77 Note — The facts and recommendations made in this publication are based on data assembled from various sources, our own research and the research of others. Although every attempt has been made to ensure accuracy, neither Chromalox nor the contributors to this publication assume responsibility for any inaccuracies or omissions in the data presented. In addition, Chromalox and its representatives cannot anticipate all conditions under w hich the information contained herein, our products or our products in combination with products of other manufacturers may be used. Neither Chromalox nor its representatives accept res ponsibility for the results o btained by the application of the information contained herein or the safety or suitability of our products, either alone or in combination with other products . Us ers are advised to m ak e their own tes ts and ev aluations of the suitability and safety of each s uch product or product combination for their speci c purposes I-4

Technical

Technical Information

Heat Transfer Fundamentals & Thermodynamic Properties Heat Transfer Fundamentals  The principles of heat transfer are well understood and are briefly described below. Heat energy is transferred by three basic modes. All heating applications involve each mode to a greater or lesser degree. Conduction Convection Radiation Conduction is the transfer of heat energy

through a solid material. Metals such as copper and aluminum are good conductors of heat energy. Glass, ceramics and plastics are relatively poor conductors of heat energy and are frequently used as thermal insulators. All gases are poor conductors of heat energy. A combination of expanded glass or ceramic fiber filled with air is excellent thermal insulation. Typical conduction heating applications include platen heating (cartridge heaters), tank heating (strip and ring heaters), pipe tracing and other applications where the heater is in direct contact with the material being heated. Convection is the transfer of heat energy by

circulation and diffusion of the heated media. It is the most common method of heating fluids or gases and also the most frequent application of electric tubular elements and assemblies. Fluid or gas in direct contact with a heat source is heated by conduction causing it to expand. The expanded material is less dense or lighter than its surroundings and tends to rise. As it rises, gravity replaces it with colder, denser material which is then heated, repeating the cycle. This circulation pattern distributes the heat energy throughout the media. Forced convection uses the same principle except that pumps or fans move the liquid or gas instead of gravity.

Convection in a Liquid  Liquid

Radiation  is the transfer of heat energy by

electromagnetic (infrared) waves and is very different from conduction and convection. Conduction and convection take place when the material being heated is in direct contact with the heat source. In infrared heating, there is no direct contact with the heat source. Infrared energy travels in straight lines through space or vacuum (similar to light) and does not produce heat energy until absorbed. The converted heat energy is then transferred in the material by conduction or convection.

The specific heat of a substance is defined as the amount of heat energy required to raise one pound of the material by one degree Fahrenheit. Specific heat factors are usually defined as British thermal units per pound per degree Fahrenheit Btu/lb/°F) . The specific heat of most materials is constant at only one temperature and usually varies to some degree with temperature. Water has a specific heat of 1.0 and absorbs large quantities of heat energy. Air, with a specific heat of 0.24, absorbs considerably less heat energy per pound.

Radiant Energy (Infrared) Heating 

Hea t of Fusion or Vaporization —  Many

All objects above “absolute zero” temperature radiate infrared energy with warmer objects radiating more energy than cooler objects. Infrared energy radiating from a hot object (heating element) strikes the surface of a cooler object (work piece), is absorbed and converted to heat energy. Paint drying by radiant heaters is a typical application of infrared heating. The most important principle in infrared heating is that infrared energy radiates from the source in straight lines and does not become hea t energy until absorbed by the  w ork produ ct

Thermodynamic Properties  All materials have basic physical constants and thermodynamic properties. These constants are used in the evaluation of the materials and in heat energy calculations. The constants and properties most often used are: Specific Heat (C p)

Electric Heater

Heat of Fusion (H fus) Heat of Vaporization (H vap) Thermal Conductivity (k) Thermal Resistivity (R) S pecifi c Heat (Quantity of Heat Energy)

Typical convection heating applications include water and oil immersion heating, air heating, gas heating and comfort air heating.

 All

materials contain or absorb heat energy in differing amounts. The quantity of heat energy or thermal capacity of a particular material is called its specifi c heat .

materials can change from a solid to a liquid to a gas. For the change of state to occur, heat energy must be added or released. Water is a prime example in that it changes from a solid (ice) to a liquid (water) to a gas (steam or vapor). If the change is from a solid to a liquid to a gas, heat energy is added. If the change is from a gas to a liquid to a solid, heat energy is released. These energy requirements are called the heat of fusion  and the heat of  v a poriz a ti on . They are expressed as Btu per pound (Btu/lb) . H e a t o f F u s io n  is the amount of energy

required to transform a material from a solid to a liquid (or the reverse) at the same temperature. Water has a heat of fusion of 143 Btu/lb. Heat of Vaporization  is the amount of

energy required to transform a material from a liquid to a gas (or the reverse) at the same temperature. Water has a high heat of vaporization, 965 Btu/lb. Water can transfer large amounts of heat energy in the form of condensing steam. Thermal Conductivity  is the ability of a mate-

rial to transmit heat energy by conduction. Thermal conductivity is identified as “k”  and is usually expressed in British thermal units per linear inch (or foot) per hour per square foot of area per degree Fahrenheit. (Btu/in/hr/ ft  /° F) or (Btu/ft/hr/ft  / ° F ) . “k”  factors are used extensively in comfort heating applications to rate the effectiveness of building construction and other materials as thermal insulation. “k”  factors are also used in the calculation of heat losses through pipe and tank insulation. Thermal Re sistivity  or “R” is the inverse of

thermal conductivity. Insulating materials are rated by “R” factors. The higher the “R” factor, the more effective the insulation.

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Technical

Technical Information

Determining Heat Energy Requirements G eneral Applicati ons

P rocess A pplications

D etermining H eat E nergy L ost 

The objective of any heating application is to raise or maintain the temperature of a solid, liquid or gas to or at a level suitable for a particular process or application. Most heating applications can be divided into two basic situations; applications which require the maintenance of a constant temperature and applications or processes which require work product to be heated to various temperatures. The principles and calculation procedures are similar for either situation.

The selection and sizing of the installed equipment in a process application is based on the larger of two calculated heat e nergy requirements . In most process applications, the start-up and operating parameters represent two distinctly different conditions in the same process. The heat energy required for start-up is usually considerably different than the energy required for operating conditions. In order to accurately assess the heat requirements for an application, each condition must be evaluated. The comparative values are defined as follows:

Objects or materials at temperatures above the surrounding ambient lose heat energy by conduction, convection and radiation. Liquid surfaces exposed to the atmosphere lose heat energy through evaporation. The calculation of total heat energy requirements must take these losses into consideration and provide sufficient energy to offset them. Heat losses are estimated for both start-up and operating conditions and are added into the appropriate calculation.

C onstan t Temperature Applicati ons Most constant temperature applications are special cases where the temperature of a solid, liquid or gas is maintained at a constant value regardless of ambient temperature. Design factors and calculations are based on steady state conditions at a fixed difference in temperature. Heat loss and energy requirements are estimated using “worst case” conditions. For this reason, determining heat energy requirements for a constant temperature application is relatively simple. Comfort heating (constant air temperature) and freeze protection for piping are typical examples of constant temperature applications. The equations and procedures for calculating heat requirements for several applications are discuss ed later in this section.

 V a ri a ble Tem per a t u re A ppl ica t ion s Variable temperature (process) applications usually involve a start-up sequence and have numerous operating variables. The total heat energy requirements for process applications are determined as the sum of these calculated variables. As a result, the heat energy calculations are usually more complex than for constant temperature applications. The variables are: Total Hea t Energy Abs orbed —  The sum of all the heat energy absorbed during start-up or operation including the work product, the latent heat of fusion (or vaporization), make up materials, containers and equipment. Total Heat Energy Lost —  The sum of the heat energy lost by conduction, convection, radiation, ventilation and evaporation during start-up or operation. Design S afety Fa ctor  A factor to compensate for unknowns in the process or application.

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• Ca lculated heat ene rgy required for process s tart-up over a specifi c time period. • Calculated heat energy required to maintain process temperatures and operating conditions ov er a s pecifi c cycle time.

D etermin ing H eat Energy Absorbed The first step in determining total heat energy requirements is to determine the heat energy absorbed. If a change of state occurs as a direct or indirect part of the process, the heat energy required for the change of state must be included in the calculations. This rule applies whether the change occurs during startup or later when the material is at operating temperature. Factors to be considered in the heat absorption calculations are shown below: S tart-Up Re quireme nts (Initial Heat-Up)

 Heat absorbed during start-up by: • Work product and materials • Equipment (tanks, racks, etc.)  Latent heat absorption at or during start-up: • Heat of fusion • Heat of vaporization  Time factor Operating Re quirements (P rocess

 Heat absorbed during operation by: • Work product in process • Equipment loading (belts, racks, etc.) • Make up materials  Latent heat absorption during operation: • Heat of fusion • Heat of vaporization Time (or cycle) factor, if applicable

Heat Losses at S tart-Up —  Initially, heat losses at start-up are zero since the materials and equipment are all at ambient temperature. Heat losses increase to a maximum at operating temperature. Consequently, start-up heat losses are usually based on an average of the loss at start-up and the loss at operating temperature. Heat Loss es at Operating Temperature — Heat losses are at a maximum at operating temperature. Heat losses at operating temperature are taken at full value and added to the total energy requirements.

Estima ting H eat L oss Fa ctors The heat losses just discussed can be estimated by using factors from the charts and graphs provided in this section. Total losses include radiation, convection and conduction from various surfaces and are expressed in watts per hour per unit of surface area per degree of temperature (W/hr/ft / ° F ) . Note — Since the values in the charts are already expressed in watts per hour, they are not influenced by the time factor “t”  in the heat energy equations.

D esign Sa fety Factors In many heating applications, the actual operating conditions, heat losses and other factors affecting the process can only be estimated. A safety factor is recommended in most calculations to compensate for unknowns such as ventilation air, thermal insulation, make up materials and voltage fluctuations. As an example, a voltage fluctuation (or drop) of 5% creates a 10% change in the wattage output of a heater. Safety factors vary from 10 to 25% depending on the level of confidence of the designer in the estimate of the unknowns. The safety factor is applied to the sum of the calculated values for heat energy absorbed and heat energy lost.

Technical

Technical Information

Determining Heat Energy Requirements Total Heat Energy Requirements  The total heat energy ( Q T ) required for a particular application is the s um o f a num ber of  v aria bles . T he ba s ic t ot al e ne rg y equa tion is

Q T  = Q M  + Q L  + Safety Factor  W here: Q T  = The total energy required in k ilowatts Q M  = The total energy in k ilowatts abs orbed by the work product including latent heat, mak e up m aterials, containers and equipment Q L  = The total energy in kilowatts lost from the surfaces by conduction, convection, radiation, v entilation and evaporation S a fe ty Fact or = % to  W hile Q T is traditionally express ed in Btu’s (British Thermal Units), it is more convenient to use watts or k ilowatts w hen applying electric heaters. Equipme nt se lection can then be bas ed directly on rated heater output. Equations and examples in this section are converted to watts.

Basic Heat Energy Equations  The following equat ions outline the calculations necessary to determine the variables in the above total energy equation. Equations 1 and 2 are used to determine the heat energy absorbed by the w ork product and the equipment. The specifi c heat and the latent heat of va rious m aterials are listed in this s ection in tables of properties of non-m etallic so lids, metals, liquids, air and gases . Equations 3 and 4 are used to determine heat energy losses. Heat energy losses from s urfaces can be estimated using v alues from the curves in charts G S , GS , GS or GS. Conduction losses are calculated using the thermal conductivity or “k”  factor listed in the tables for properties of ma terials.

q u atio n 1 — He at e r y e q u i re d to a ise the Temperat re o f t e M aterials ( o C an e f S tate).  The heat energy absorbed is determined from the weight of the materials, the specifi c heat and the change in temperature. S ome materials, such as lead, have different specifi c heats in the different states. W hen a change of state occurs, two calculations are required for thes e m aterials, one for the s olid mat erial and one for the liquid after the solid has m elted. Q  A = L bs x C p   x ∆T  2 Btu k W  

 W he re: Q  A  = W h required to raise the temperature Lbs = W eight of the material in pounds C p  = S peci c heat of the material (Btu/lb/° F) ∆T  = C hange in temperature in F T 2 (Final  - T 1 ( Start

E q u a tio n 2  —  He at e r y e q u ire d t C a n e t e S ta te o f t e M a te ri a s.  The heat energy absorbed is determined from the  w eig ht of th e m at eria ls and t he laten t h ea t o f fusion or v aporization. Q F or Q  v = L bs x H fus  or H  va p 2 B tu k W    W he re: Q F = W h required to change the material from a s olid to a liquid Q  v  = W h required to change the material from a liquid to a vapor or gas Lbs = W eight of the material in pounds Q fus  = Heat of fusion (Btu/lb/°F) Q  va p  = Heat of vaporization (Btu/lb/°F)

E q u a tio n  — He at e r y st r m r faces.  The heat energy lost from s urfaces by radiation, convection and evaporation is determined from the surface area and the loss rate in watts per square foot per hour. Q LS

A x L S 1 0 0 0 W /k W  

 W he re: Q LS = W h lost from surfaces by radiation, convection and evaporation A = A rea of the surfaces in square feet LS Loss rate in watts per square foot at nal temperature (W /ft  /hr from cha rts)

E q atio n  — Heat e r y st y C d c ti o n t r h a te ri a s r s a ti o n .  The heat energy lost by conduction is determined by the surface area, the thermal conductivity of the material, the thick ness and the tem perature difference across the m aterial Q LC

A x k  x ∆T  d  x 3 4 2 Btu k W  

 W he re: Q LC = W h lost by conduction A = Area of the surfaces in square feet k  = Thermal conductivity of the mat erial in Btu/inch/square foot/hour (Btu/in/ ft  /hr) ∆T  = Temperature difference in °F across the material [T  - T d  = Thick ness of the material in inches

Summarizing Energy Requirements  Equations 5 a and b are used to summarize the results of all the other equations desc ribed on this page. These tw o equations determine the total energy requirements for the two process conditions, start-up and operating.

E q u a tio n 5 a  — ta rt- U p. QT

He at

Q  A  + Q F [ or Q  V ] t 

e r y e q u i re d r

Q LS  + Q LC ( 1 + S F

 W he re: Q T = The total energy required in ilowatts Q  A  = W h required to raise the temperature Q F = W h required to change the material from a solid to a liquid Q  V  = W h required to change the material from a liquid to a vapor or gas Q LS = W h lost from surfaces by radiation, convection and evaporation Q LC = W h lost by conduction S F = S afety Factor (as a percentage) t  = S tart-up time in hours

E q u a tio n 5 b  — He at e r y e q u i re d t a i ta in pe ra ti n r r c e ss  . Q T  = Q  A  + Q F  [ or Q  V ]

Q LS  + Q LC ) (1 + S F

 W he re: Q T = The total energy required in ilowatts Q  A  = W h required to raise the temperature of added m aterial Q F = W h required to change added material from a solid to a liquid Q  V  = W h required to change added material from a liquid to a vapo r or gas Q LS = W h lost from surfaces by radiation, convection and evaporation Q LC  = W h lost by conduction S F = S afety Factor (as a percentage)

Equipment Sizing & Selection  The size and rating of the installed heating equipment is bas ed on the larger of calculated results of Equation 5 a or b.

o tes   1.

ss a c t rs from   charts in this section include loss es from radiation, conv ection and evaporation unless oth erwise indicated.

2. Time ( t )  is factored into the s tart-up equation since the start up of a process may vary from a period of minutes or hours to days .

pe ra ti n g R e q u i re me n t s are   normally based on a s tandard time period of one hour ( t  = ). If cycle times and heat energy requirements do not coincide with hourly intervals, they s hould be recalculated to a hourly time base. I-

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Technical

Technical Information

Determining Heat Energy Requirements - Heating Liquids Typical S teps in etermin in T ta l er g y e i reme ts  

maintain the operating temperature.

 A final rinse tank requires water at 180°F. The tank is 2 feet wide by 4 feet long by 2 feet high and is uninsulated with an open top. The tank is made of 3/8” steel and contains 100 gallons of water at 70°F at start up. Make up water with a temperature of 60°F is fed into the tank at the rate of 40 gallons per hour during the process. There is an exhaust hood over the tank and the relative humidity in the area is high. Work product is 300 lbs. of steel per hour.

Select  the number and type of heaters

Example —  Heat the water to 180°F in 3

Most heating problems involve three basic steps: Determine  required kW capacity for

bringing application up to operating temperature in the desired time. Calculate  the kW capacity required to

required to supply the kW required. Note — Some applications, such as instantaneous heating of gas or air in d ucts, comfort heating and pipe tracing only require calculation of the operating kW and selection of heaters.

esi g n C o si der ati o s   In order to calculate the initial and operating kW capacity requirements, the following factors should be considered:  Specified heat-up time  Start-up and operating temperatures  Thermal properties of material(s) being heated  Weight of material(s) being heated  Weight of container and equipment being heated  Weight of make up material (requirements per hour)  Heat carried away by products being processed or equipment passing through heated area  Heat absorbed due to a change of state  Thermal properties and thickness of insulation Heat losses from the surface of material and/or container to the surrounding environment.

i q i d H ea ti n g E a mp e   One of the most common electric heating applications is the direct immersion heating of liquids. The following example illustrates the steps in determining total energy requirements of a typical direct immersion application.

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 App li ca ti on

hours and heat 40 gallons per hour of make up water from 60°F to 180°F thereafter.

LSC = Losses from the surfaces of the tank LSW = Surface losses from water (Graph G114S, Curve 2 fps @ 60% rh) 8 ft2 x 550 W/ft 2 = 4.4kW 1000 W/kW LSC = Surface losses from uninsulated tank walls (Graph G125S) 32 ft2 x 0.6 W/ft 2 x (180 - 70°F) = 2.11 kW 1000 W/kW Heat Required for Start-Up —

(26.9 kW + 1.89 kW + 4.4 kW + 2.11 kW )x 1.2 3 hrs

2

Specific heat of steel = 0.12 Btu/lb/°F Specific heat of water = 1.00 Btu/lb/°F Weight of steel = 490 lb/ft 3 Weight of water = 8.345 lb/gal

Q S = 15.42 kW

To Find Initial (S tart-Up) Hea ting Capacity —

Q  o = Q  wo + Q

Q S = (Q A + Q C + Q LS)(1 + SF) t  2

Where: Q  wo = kW to heat additional water

Where: Q S = The total energy required in kilowatts Q A = kWh required to raise the temperature of the water Q C = kWh required to raise the temperature of the steel tank Q LS = kWh lost from surfaces by radiation, convection and evaporation SF = Safety Factor t  = Start-up time in hours (3) W to Heat Water

100 gal x 8.345 lb/gal x 1.0 Btu/lb (180 - 70°F) 3412 Btu/kW Q

A

= 26.9 kW

W to Heat Steel Tank

Lbs of steel = Area x thickness x 490 lbs/ft 3 32 ft2 x 0.375 in. x 490 lb/ft 3 = 490 lbs 12 490 lbs x 0.12 Btu/lb (180 - 70°F) 3412 Btu/kW Q C = 1.89 kW

Heat Losse s from S urfaces — Q

LS =

LSW + LSC

Where: Q LS = kWh lost from all surfaces LSW = Losses from the surface of the water

To Find Hea t Re quired for Operating — LS +

Q ws )(1 + SF)

40 gal x 8.345 lb/gal x 1.0 Btu/lb (180 - 60°F) 3412 Btu/kW Q  wo = 11.7 kW Q  ws = kW to heat steel 300 Lbs. x 0.12

x (180 - 60°F)/3412 = 1.27 kW Hea t Required for Operating — Q  o = (11.7 kW + 1.27 kW + 4.4 kW + 2.11 kW)

1.2 Q  o = 23.38 kW

Installed Ca pacity —  Since the heat required

for operating (21.85 kW) is greater than the heat required for start up (15.42 kW), the installed heating capacity should be based on the heat required for operation. With 22 kW installed, the actual initial heating time will be less than 3 hours.  Moisture resistant terminal enclosures are recommended for industrial liquid heating applications. Install two stock 12 kW MT-2120E2 or 12 kW MT-3120E2 screw plug heaters or two 12 kW KTLC-312A over-the-side heaters with an automatic temperature control. Automatic temperature control will limit the kWh consumption to actual requirements during operation. A low water level cutoff control is also recommended. S ugges ted Equipment

Technical

Technical Information 

H eatin g Soft Metal with Melting Pots or C ru cibles

Determining Heat Energy Requirements 

Most soft metal heating applications involve the use of externally heated melting pots or crucibles. The following example represents a typical soft metal application.

Flow Through Water H eating

Flow T hrough Oil Heating

Circulation heater applications frequently involve “flow through” heating with no recirculation of the heated media. These applications have virtually no start-up requirements. The equation shown below can be used to determine the kilowatts required for most “flow through” applications. The maximum flow rate of the heated medium, the minimum temperature at the heater inlet and the maximum desired outlet temperature are always used in these calculations. A 20% safety factor is recommended to allow for heat losses from jacket and piping, voltage variations and variations in flow rate.

i l He ati n g i th Ci rc u l ati o n He a te rs —  The procedure for calculating the requirements for “flow through” oil heating with circulation heaters is similar to water heating. The weight of the liquid being heated is factored by the specific gravity of oil. The specific gravity of a particular oil can be determined from the charts on properties of materials or can be calculated from the weight per cubic foot relative to water.

Q  = F x C p   x T  x SF 3412 Btu/kW

tep 1 — Determine flow rate in lb s/hr. Specific gravity = 56 lbs/ft3 ÷ 62.4 lbs/ft3 = 0.9 3 gpm x 8.35 lbs/gal x 0.9 x 60 min = 1353 lbs/hr

Where: Q  = Power in kilowatts F = Flow rate in lbs/hr C p  = Specific heat in Btu/lb/°F T  = Temperature rise in °F SF = Safety Factor

tep 2  Calculate kW: Specific heat of fuel oil is 0.42 Btu/lb/°F

ample  —  Heat 5 gpm of water from 70 - 115°F in a single pass through a circulation heater. tep 1 —  Determine flow rate in lbs/hr. (Density of water is 8.35 lbs/gal) 5 gpm x 8.35 lbs/gal x 60 min = 2505 lbs/hr

kW= 2505 lbs x 1 Btu/lb/°F x (115-70°F) x 1.2 SF 3412 Btu/kW kW= 39.6 kW

12 low rate in

1

1

2

H f r given Temperat re R ise 

20 122 184 245 306 368

490

613

30

81 122 163 204 245

327

409

40

61

92 122 153 184

245

306

50

49

73

98 122 147

196

245

60

40

61

81 102 122

163

204

70

35

52

70

87 105

140

175

80

30

46

61

76

92

122

153

90

27

40

54

68

81

109

136

100

24

36

49

61

73

98

122

110

22

33

44

55

66

89

111

120

20

30

40

51

61

81

102

130

18

28

37

47

56

75

94

1. Safety Factor and losses not included.

e q i re me n ts

Q T = (Q A + Q F + Q L + Q C + Q LS)(1 + SF) t  2

kW = 9.99

Where: Q A = kW to heat lead to melting point. [400 lbs x 0.0306 Btu/lb/°F (621 - 70°F)] ÷ 3412 Q  F = kW to melt lead (400 lbs x 10.8 Btu/lb) ÷ 3412 Q L = kW to heat lead from melting pt. to 800°F [400 lbs x 0.038 Btu/lb/°F (800 - 621°F)] ÷ 3412 Q C = kW to heat steel pot [150 lbs x 0.12 Btu/lb/°F (800 - 70°F)] ÷ 3412 Q LS = Surface losses from lead and outside shell [(1000 W x 3 ft2) + (62 W x 20 ft2)]/2 ÷ 1000 t = 1 hour Q T = 9.98 kW x 1.2 = 11.99 kW

e sti  —  Choose watt density for fuel oil and then select heater. Use a stock NWHOR05-015P, 10 kW circulation heater with an AR-215 thermostat.

H eat Required for Various Temperature Rise (Exclusive of Losses) 20 28

    H 24    t    t    a

Heater R atin g (kW) 

i n d ta rt- U p He a ti n g

kW= 1353 lbs x 0.42 Btu/lb/°F x (100 - 50°F) x 1.2 SF 3412 Btu/kW

   s    r

T emperature Rise Vs. Water Flow 1

Melting point of lead = 621°F Specific heat of solid lead = 0.0306 Btu/lb/°F Specific heat of molten lead = 0.038 Btu/lb/°F Heat of fusion/lead = 10.8 Btu/lb Specific heat of steel crucible = 0.12 Btu/lb/°F Radiation loss from molten lead surface = 1000 W/ft2 (from curve G-128S). Surface loss from outside shell of pot 62 W/ft2 (from curve G-126S). SF = Safety Factor 20% To

Gr aph G -236 — Oil H eating

tep 2 —  Calculate kW: C p  = Specific heat of water = 1 Btu/lb/°F

Temp. i se   (°F) 

ample  —  Heat 3 gpm of #4 fuel oil with a weight of approximately 56 lbs/ft 3 from 50°F to 100°F.

A steel melting pot weighing 150 lbs contains 400 lbs of lead. The pot is insulated with 2 inches of rock wool and has an outside steel shell with 20 ft2 of surface area. The top surface of the lead has 3 ft2 exposed to the air. Determine the kilo-watts required to raise the material and container from 70°F to 800°F in one hour, and heat 250 lbs of lead per hour (70°F to 800°F) thereafter.

    i 20     1

To

i n d O pe ra ti n g

e q u i re me n t s

Q T = (Q A + Q F + Q L + Q LS)(1 + SF)

   a 16    r    e pe c i fi c He at f i l

    d 120    e    t    a    e     H    s

0.60 .4 7 (Avera e P etroleum O ils) 0.40

   a

10 0

20 0 300 400 500 Temperature In rease (°F ) 

600

CA T — Consult recommendations elsewhere in this section for watt density and maximum sheath temperatures for oil heating.

Where: Q A = kW to heat added lead to melting point. (250 lbs x 0.0306 Btu/lb/°F [621 - 70°F]) ÷ 3412 Q F = kW to melt added lead (250 lbs x 10.8 Btu/lb) ÷ 3412 Q L = kW to heat lead from melting pt. to 800°F (250 lbs x 0.038 Btu/lb/°F [800 - 621°F]) ÷ 3412 Q LS = Surface losses from lead and outside shell (1000W x 3 ft2) + (62W x 20 ft2) ÷ 1000 Q T = 6.69 kW x 1.2 = 8.03 kW Since start-up requirements exceed the operating requirements, 12 kW should be installed. I-

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Technical

Technical Information Heat Loss Factors & Graphs raph 12  — Heat sses fro m Walls f O ve s, P ipes, Tan ks, E tc.

   n     i  o   a   t     l     s   u     I   n

    n     o      i      t     a       l      u     s     n       I

2200 2000   n    i  o   a   t     l    s   u

   i  c     h     T

    c      i       h       T

 c    h  i    T

 c  T  h i

200

400

600

800

1000

   r    u    o    H    r    e    P    t    o    o    F    e    r    a    u    q    S    r    e    P    s    t    t    a    W

   I  n

  i c   T  h

0

raph 12  — H ea t sses f r m i n s a ted eta l r fa c es C o m i n ed sses f r m C o vec t i n & a di ati o 2400

Curves based on combined natural convection and radiation losses a t 7 ° F In s u la t i on k = 0 .6 7 @ 2 0 0 ° F

   r    u    o    H    r    e    P    t    o    o    F    e    r    a    u    q    S    r    e    P    s    t    t    a    W

rfaces f In s lated

 n   t  i o   u  l  a  s   I n  o n  a t i   l   u  I n s

1200

1400

1800 1600 1400 1200 1000

 A -Ox idi ze d S te e l ( e = B -O xi di ze d S t e e l ( e = . 8 C - Ox id iz e d S t e e l ( e = 0 . 8  A -Ox id ize d A lum inu m (e = .2 B - Ox i di z e d A l u m in u m ( e = 0 . 2 C - O xi d iz e d A lu m i nu m ( e = 0 . 2

200

1600

300

400

12

 —

H ea t

sses f r m

i l r P a ra f n

r fa c es  

900

1000

Curve A shows heat loss from vertical surfaces of tanks, pipes, etc. and the top of a flat horizontal surface.

 A ll C urv e s  based on still air (1 fps) @ 70°F, e = emissivity.

Note — The above graph is difficult to read for surface temperatures below 250°F. To estimate heat losses for surface temperatures below 250°F, and the air is st ill, use the following formula:

0.6 W x ft2 x  ∆ T °F Where:  ∆ T is the temperature difference in °F between the heated surface and the ambient.

raph 0

100

200

300

400

500

1600

600

Temperature of Oil or Pa raf n (°F

raph G 12  — H eat sses r m faces ( ead, ab it, Tin , Type etal, 1400 1300

1500

ten etal r lder, tc.) 

Curves Based o n ° F A m b i en t  

1200 1100 1000

00

400

500

600

700

Temperature ( °F

I- 1

800

Curve C shows heat losses from only the bottom surface of flat horizontal surfaces.

   r    u    o    H    r    e    P    t    o    o    F    e    r    a    u    q    S    r    e    P    s    t    t    a    W

   r    u    o    H    r    e    P    t    o    o    F    e    r    a    u    q    S    r    e    P    s    t    t    a    W

700

Curve B shows the combined heat loss from both the top and bottom surfaces of flat horizontal surfaces.

Curves Based o n ° F A m b i en t  

1000

600

Surface Temperature (°F

Temperature Difference ( °F

raph

500

.8

800

900

   r    u    o    H    r    e    P    e    c    a     f    r    u    S    r    e    t    a    W     f    o    t    o    o    F    e    r    a    u    q    S    r    e    P    s    t    t    a    W

11

 —

Heat

Curves Based o n ° F A m b ie n t  

1400 1300

sses fro m Water S rfaces 

 2 F. P. S . 4 % R e l a ti v e Hu m id it y 1 F. P. S . 4 % R e l a ti v e Hu m id it y 2 F. P. S . 6 % R e l a ti v e Hu m id it y 1 F. P. S . 6 % R e l a ti v e Hu m id it y  

1200 1100 1000

80

100

120

140

160

Temperature of W ater (°F

180

200 210

Technical

Technical Information Determining Heat Energy Requirements P i p e & T a n k T r aci n g T ef i g ta es can e u sed to determi e th e h eat l sses fro m i su lated pipes an d tan ks fo r h eat tracin g app icatio s. To se th ese ta es, determi e t e f in g desig n fa to rs • Temperatu re differe tial ∆T = T   - T A Wh ere: T   = esired main te an e temperat re T A = i im m e pe ted am ie t  temperat re °F • Type a d t ickn ess o f i su atio • iameter o f pipe r s rfa e area o f ta k  • •

td r r i d r app i ati a imu m expe ted in d vel ity (i td rs).

Pipe Tracing Example — ai tain a 1-1/2 inc h IP S pipe at 1 °F to keep a pr ess id i . T e pipe is ated td rs a d is ins ated ith 2 inc h t ick Fib er as  in s ati . Th e min im m e pe ted amb ie t temperatu re is °F an d th e maxim m expe ted in d ve ity is 5 mp . D etermi e h eat sses per fo t f pipe. 1. Heat Loss Rate — si g Ta e 1 determin e t e h eat l ss rate in W/ft f pipe per F temperatu re differe tial. ter tab le  ith i s ati n ID r I S pipe size (1-1/2  in .) a d i su ati n th i k ess (2 i .). ate = . 8 Watts/ft/°F. 2. Heat Loss per Foot — Calcu ated h eat  ss per f t o f pipe e als t e maximu m  temperat re differen tial ( ∆T) times h eat  lo ss rate in Watts/ft/°F . ∆T =

Q Q

10 0 ° F - 0 ° F = 10 0 ° F = ( ∆T)(h eat lo ss rate per )  = (1 ° F ) ( . 8 W /f t) = 3 . 0 W/ ft  

3. Insulation Factor — Tab le 1 is b ased o ib er as   i s ati n a d a ° F ∆T. Adj st Q fo r t ermal d tivity  ( k facto r) an d temperatu re as ec essary si g ad stme t facto rs fr m Tab e 2. Adj sted Q = ( Q)(1. ) = . 0 W/ft x 1. Q = .10 W/ft  4.

Tab e 1 is b ased n 20 mph in d velo ity. Adju st Q f r i d ve ity as e essary by addi g % fo r ea h 5 mph ver 20 mp . o t add m re th an 15 % re ard ess f w in d speed. Wind Factor —

Adj sted Q = ( Q)(1.15 ) = .10 W/ft x 1.15 Design heat loss per linear foot Q  = 4.72 W/ft Note

r i do r i stalatio s, mu tiply Q b y . .

Table 1 — H eat L osses from Insulated M etal Pipes  W a t t s p er foot of pi pe per F t em per a t u re differen t ia l Insulation Thickness (In.) Pipe Size Insul. I.D. (IPS) (In.) 1/2 3/4 1 1-1/2 2 2-1/2 3 4 1/2 0.840 0.054 0.041 0.035 0.028 0.024 0.022 0.020 0.018 3/4 1.050 0.063 0.048 0.040 0.031 0.027 0.024 0.022 0.020 1 1.315 0.075 0.055 0.046 0.036 0.030 0.027 0.025 0.022 1-1/4 1.660 0.090 0.066 0.053 0.041 0.034 0.030 0.028 0.024 1-1/2 1.990 0.104 0.075 0.061 0.046 0.038 0.034 0.030 0.026 2 2.375 0.120 0.086 0.069 0.052 0.043 0.037 0.033 0.029 2-1/2 2.875 0.141 0.101 0.080 0.059 0.048 0.042 0.037 0.032 3 3.500 0.168 0.118 0.093 0.068 0.055 0.048 0.042 0.035 3-1/2 4.000 0.189 0.133 0.104 0.075 0.061 0.052 0.046 0.038 4 4.500 0.210 0.147 0.115 0.083 0.066 0.056 0.050 0.041 — 5.000 0.231 0.161 0.125 0.090 0.072 0.061 0.054 0.044 5 5.563 0.255 0.177 0.137 0.098 0.078 0.066 0.058 0.047 6 6.625 0.300 0.207 0.160 0.113 0.089 0.075 0.065 0.053 — 7.625 0.342 0.235 0.181 0.127 0.100 0.084 0.073 0.059 8 8.625 0.385 0.263 0.202 0.141 0.111 0.092 0.080 0.064 — 9.625 0.427 0.291 0.224 0.156 0.121 0.101 0.087 0.070 10 10.75 0.474 0.323 0.247 0.171 0.133 0.110 0.095 0.076 12 12.75 0.559 0.379 0.290 0.200 0.155 0.128 0.109 0.087 14 14.00 0.612 0.415 0.316 0.217 0.168 0.138 0.118 0.093 16 16.00 0.696 0.471 0.358 0.246 0.189 0.155 0.133 0.104 18 18.00 0.781 0.527 0.401 0.274 0.210 0.172 0.147 0.115 20 20.00 0.865 0.584 0.443 0.302 0.231 0.189 0.161 0.125 24 24.00 1.034 0.696 0.527 0.358 0.274 0.223 0.189 0.147 1. Values in Table 1 are based on a pipe temperature of 50°F, an ambient of 0°F, a wind velocity of 20 mph and a “k” factor of 0.25 (Fiberglas®). Values are calculated using the following formula plus a 10% safety margin: Watts/ft of pipe = 2 π k (∆ T) ÷ (Z) In (D0/D1) Where: k = Thermal conductivity (Btu/in./hr/ft2/°F) D1 = Inside dia. of insulation (in.) ∆ T = Temperature differential (°F) Z = 40.944 Btu/in/W/hr/ft D0 = Outside diameter of insulation (in.) In = Natural Log of D0/D1 Quotient

T a b le 2 — T h er m a l C on d u ct i v i t y M aterials Btu/in./hr/ft / ° F ) Insulation Type ® Fiberglas  or k  value Mineral Fiber Based Adjustment factor on ASTM C-547 Calcium Silicate2 k  value Based on ASTMC-533 Adjustment factor Foamed Glass2 k  value Based on ASTMC-552 Adjustment factor Foamed Urethane k  value Based on ASTMC-591 Adjustment factor

) F a ct or of T y pi ca l P i p e I n su l a t i on Pipe Maintenance Temperature (°F) 0 50 100 150 200 300 400 500 0.23 0.25 0.27 0.30 0.32 0.37 0.41 0.45 (0.92) (1.00) (1.08) (1.20) (1.28) (1.48) (1.64) (1.80) 0.35 (1.52) 0.38 (1.52) 0.18 (0.72)

0.37 (1.48) 0.40 (1.60) 0.17 (0.68)

0.40 (1.60) 0.43 (1.72) 0.18 (0.72)

0.43 (1.72) 0.47 (1.88) 0.21 (0.84)

0.45 (1.80) 0.51 (2.04) 0.25 (1.00)

0.50 (2.00) 0.60 (2.40)

0.55 0.60 (2.20) (2.40) 0.70 0.81 (2.8) (3.24) Not Recommended

2. When using rigid insulation, select an inside diameter one size larger than the pipe on pipe sizes through 9 in. IPS. Over 9 in. IPS, use same size insulation.

T a b le 3 —

H ea t L o sses f r om I n su l a t ed M e t a l T a n k s W / f t  / ° F ) Insulation Thickness (In.)

1/2

3/4

1

1-1/2

2

2-1/2

3

3-1/2

4

5

6

0.161 0.107 0.081 0.054 0.040 0.032 0.027 0.023 0.020 0.016 0.013 3. Values in Table 3 are based on a tank temperature of 50°F, an ambient of 0°F, a wind velocity of 20 mph and a “k” factor of 0.25 (Fiberglas®). Values are calculated using the following formula plus a 10% safety margin:   Watts/ft2 = Y k(∆ T ) ÷ X k = Thermal conductivity Where: Y = 0.293W/hr/btu X = Thickness of insulation (in.) ∆ = Temperature differential (°F)

Note — T e a ve i fo rmati n is presen ted as a ide f r s vin g typical eat tra in g app i a ti s. C tact y r L al Ch ro ma x ales ffi e f r assistan e in eater se e tio n a d f r pipes made o f materials o th er t an metal. I-11

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

Technical

Technical Information

In s ul a ti on F a ct or — Tab e 3 is ased ib er as   i s ati n a d a ° F ∆ T . Ad st fo r th ermal d tivity ( k fa to r) an d temperat re as n ecessary, u si facto rs fr m Tab le 2.

Determining Heat Energy Requirements Pi pe & Tank Tra cin g (cont’d.) Ta k tra in g re ires an additi al cal atio f th e t tal e po sed s rface area. To al ate th e s rfa e area: Cylindrical Tank s —

r

Area = 2 π  r 2  + π  D H  A  = π  D (r + H)  

ai tain a meta ta k w ith 2 i h t ic k F i b er as    in su atio n at °F. T e tan k is l ated o td rs, is 4 feet i diameter, 12 feet l g an d is e po sed at b th en ds. Th e mi im m am ie t temperatu re is F an d th e ma im m expected in d speed is 15 mp . Tank Tracing Example  —

H

Area = 2[(W x ) + (L x H) + (H x W)]

late t e su rfa e area

f t e ta k.  A  = π  D (r + H)  A  = π  4 (2 + 12)  A  = 1 .9 t 2  

D

Horizontal Tank s —

Ca

. S urfa ce A re a

Tab e 3 is ased o n 2 mph w in d vel ity. Ad st fo r in d vel ity as n e essary, b y addin g % fo r ea h 5 mph ver 20 mp . o t add mo re th an 1 % re ard ess f w i d speed. Note r i do r i stal atio s, mu tiply y . .

. W i nd F a ctor

. C a l cu la t e To ta l He a t L os s f or Ta n k —

tiply t e adj sted eat l ss per s are fo t per °F re y t e temperat re differe tial. M tiply t e l ss per s are fo t b y t e area.

. Temperature Differential ( ∆ T )  ∆ T   =

T   - T A = 5 0 ° F - 0 ° F = 5 0 ° F

= . 4 W t 2   ° F x 5 0 ° F ∆ T  = 2 W/ft 2 = Adj sted W/ft 2  x ta k s rfa e area = 2 W/ft 2  x 1 7 5 .9 t2  

tain t e eat ss per sq are fo t per deg ree fro m Tab e 3 .

. Heat Loss Per Foot  — H L  W 

Heat lo ss/ft 2  ° F =

Comfort H eati ng

H e at L os s fro m Ta nk =

. 4 W t 2  /°

. 8 W a t ts

Comfort H eati ng C hart

r co mp ete ildin g a d spa e h eatin g ap plic ati s, it is re mme ded th at a detailed a a ysis f t e i di g str ti n eat sses (w al s, ei in s, rs, in d s, et .) e perfo rmed sin g AS HR AE g idelin es. Th is is th e m st acc rate an d st effe tive estimati g pr ed re. H ever, a q ick estimate f t e kW req iremen ts fo r r m a d s pp emen tal h eati g r freeze pro tecti n a e o b tai ed si g t e c h art to t e ri t. A are se exte si n meas res 20 t g x 1 3 t ide x 9 f t i . T e i di is t in s ated. Co str tio n is are rete c k w a s a d an pen c e i i g ith a p y d de k a d b i t-u p r f. etermin e t e kW re ired to mai tain t e are se at °F en th e o tside temperat re is °F. Problem  —

5600      f    t  u     C

5200

     W

4800    t    e    e    F    c    i     b    u    C    e    c    a    p    S    r    o    m    o    o    R     f    o    e    m    u     l    o    V

   f   t     f   t    C u    C u    W     W  -  2  -  2    C     B

     A 

4400

 1

4000

  D

  C  u   W  -  4

  f  t

3600 3200 2800 2400 2000 1600 1200

Solution  — . Calculate  t e v

20 f t x 13 f t x 9 ft = 2

0 ft 

. R e fe r to t e c h art, se C r ve D

rresp ds to t e

i i di g c o str c t i .

. F i nd  t e i terse ti n

f 2 0 ft  w it rve D . T e kil atts re ired are 9 .3 kW. est si g a 10 kW it er eater.

Note —

If t e v

Estimating k ilowatts required to ma intain ° F w i t h a n ou t s id e t e m p e ra t u re o f 0 ° F

me f t e r m.

me f t e r m is ar er

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Kilowatts R equired C urv e A — ver 1 % d

ms w it h l it t e o r n o r a d i d w area.

t side ex p o s u re. N o r f o r fl

r w ith

t side ex p o s u r e; o n y 1 a l ex p o s ed w ith

C urv e B — alls an d fl

ms it h a vera e ex p o s u r e. f a d 2 r 3 a s ex p o s ed, p to r i su lated if expo sed to tside temperatu res.

C urv e C —

ms w it h r o o f , a s a d fl o r u n i s ated b u t w ith i side fac i n g

% d r a d i d w area. n

t

t it h r o o f ,

a s a d c ei i .

xpo sed ard ses, pump ses, cab ins a d p rly co struc ted roo ms ith reas ably ti t j i ts C urv e D — insu lati . Typical struc ti n f co rr ated metal r p yw d siding , sing e layer roo fs.

t

th an th e c art val es, divide b y 2, 3 , 4 , etc. u til t e trial vo me ts th e cu rve. Th en se ect h eater fr m t is vo me. M tiply h eaters se ected y t e n mb er sed to se ect th e trial vo me. I- 1

Technical

Te

i al In rmati

Watt e sity Heater e e tio n U nderstanding W att D ensity  Watt density (W/in 2) is the heat flux emanating from each square inch of the effective heating area (heated surface) of the element. 2

W/in  = Rated Watts ÷ Effective heating area The effective heating area is the surface area per linear inch of the heater multiplied by the heated length. For strip heaters which are rectangular in shape, the surface area per linear inch is: 1-1/2" wide = 3.45 in 2 per linear inch 1" wide = 2.31 in 2 per inch. The heated length (HL) of strip heaters is calculated as follows: < 30-1/2" long 30-1/2" long

HL = Overall Length less 4" HL = Overall Length less 5"

For tubular elements, watt density is determined by the following formulas. Effective heating area = π  x Dia. x Heated Length The surface area per linear inch of standard diameter tubular elements is shown below: S ize Dia

In /in.

0.246 inch (1/4) 0.315 inch (5/16) 0.375 inch (3/8) 0.430 inch (7/16) 0.475 inch 0.500 inch (1/2)

0.77 0.99 1.18 1.35 1.49 1.57

The following example illustrates the procedure for determining the watt density of a typical tubular heater. Example  —  A 12 kW screw plug heater has three 0.475" diameter elements with a “B” dimension of 32 inches and a 2 inch cold end. The watt density is: 0.475 x π  x (32 in. - 2 in.) x 3 x 2 (Hairpin) = 268 in2 12,000 Watts ÷ 268 in 2 - 45 W/in 2 For convenience in selecting equipment, all heaters in this catalog have the watt density specified for standard ratings.

H eater Selection G uidelines Once the total heat energy r equirements have been determined, the selection of the type of electric heater is based on three criteria.

ide in es 

Maximum Sheath Temperature  Sheath Material Recommended Maximum Watt Density Maximum S heath Temperature —  The sheath

temperature of an electric element should be limited to prevent damage to the heater and provide reasonable life. To a large extent, the maximum sheath temperature of the heating element is determined by the final operating temperature of the process. In direct immersion applications, the sheath temperature will approximate the temperature of the heated media. In clamp-on, air and gas heating applications, the operating sheath temperature can be estimated using factors derived from empirical charts and graphs.  Element sheath material is selected based on the maximum allowable sheath temperature, the material being heated and corrosion resistance required. Depending on the sheath material and construction, metal sheathed electric resistance elements will operate satisfactorily at temperatures from less than -300°F (cryogenic) to approximately 1500°F. Copper sheath elements are commonly used for low temperature and direct immersion water heating. Steel is used for oil immersion and strip heater applications. Stainless steel and INCOLOY ® are used for corrosive solutions, high-temperature gas or air heating and cartridge heaters. The table below lists the maximum recommended operating temperatures for common sheath materials (UL 1030): S heath Material

Copper Iron Steel MONEL®

350°F 750°F 750°F 900°F

Chrome Steel Stainless 300 INCOLOY ®  INCONEL ® 

1200°F 1200°F 1600°F1 1700°F1

Maximum Recommended W att Density

 Some materials such as water, vegetable oils and salt baths can tolerate relatively high sheath watt densities. Other materials such as petroleum oils or sugar syrups require lower watt densities. These solutions have high viscosity and poor thermal conductivity. If the watt density is too high, the material will carbonize or overheat, resulting in damage to the heating equipment or material being heated. Other sections of this catalog provide guidelines and suggestions for sheath materials and recommended watt densities for many common heating problems.

ers or with tubular or strip heaters clamped to tank walls. The final choice of heater type will involve process considerations, appearance, available space both inside and outside, economy, maintenance, etc. The following pages cover the procedures for selecting heaters for clamp-on applications, liquid immersion heating, oil immersion heating, air or gas heating and cartridge or platen heating.

C lamp-On H eater Applications The limiting factor in most clamp-on heater applications is the operating temperature of the heater sheath. Selecting heaters for clamp on applications requires an analysis of the maximum expected sheath temperature based on the estimated ambient temperature and the temperature of the material being heated. Graph G-175S provides a method of estimating the sheath temperature and allowable watt densities for tubular heaters for various ambient temperatures and wattage ratings.

G r aph G S  — Tubular Heaters

C la m p-O n

S  h e a t h 

 T e m  p 

   n    I

F  

   W

S h e a t h 

 T e m 

    h    t    a    e     h    S    m    u    m    i    x    a    M

 p  F  

S h e a t h 

 T e m  p 

S  h e a t h 

 T e m  p 

0

200

400

F  

F 

600

800

1000

1200

1400

Estimated Ambient Temp. (° F) Shea th Temp. + Material Temp.

The example on the following page illustrates the procedure. 12 kW is required to heat material in a steel tank from 70°F to 800°F. Heat is to be supplied by tubular electric elements clamped to the side of the tank. Since the material is heated to 800°F, INCOLOY ® sheath elements must be used. Note 1 — For sheath temperatures above

1500°F, contact your Local Chromalox Sales office for application assistance.

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

Using the values determined in the selection criteria, choose the type of heater best suited to the application. For instance, water can be heated by direct immersion, circulation heatI- 1

Technical

Technical Information

Allowable Watt Density & Heater Selection - Guidelines Selecting C lamp-On Tubular H eat ers cont’d.) From the chart, a maximum sheath temperature of 1200°F results in an average ambient temperature of (800°F + 1200°F) ÷ 2 = 1000°F. From the curves, the allowable watt density is 9.5 W/in2. Based on size of container, 0.475 inch diameter TRI elements 28 in. long are selected. The 0.475 TRI element has 1.49 in2 per linear inch of sheath. The heated length is the overall sheath length less 6.5 inches. The allowable wattage rating on the element is (28 - 6.5) x 1.49 x 9.5 = 305 watts. The total number of elements required is 12,000W ÷ 305W = 39 elements. Order 39 elements similar to TRI2845 except rated 305 watts. If the application requires the use of tubular elements whose overall length is not standard, each element rating would be determined as follows: Heater Watts = (A - 2CE) ( Area x 9.5W) Where: A = CE = Area = 9.5 =

Sheath length, overall Cold pin length Effective heated area (in2 /in.) recommended W/in2 from G-175S

Graph G-130S provides a method of estimating the maximum allowable watt density for strip heaters for clamp on applications based on sheath operating temperature and various ambients.

G r aph G Heaters

S  —

C la mp-O n S tri p

22  20 

1200 °F 

18 

1100 °F 

16 

r     a     t      u     r     e    

1000 °F  900 °F 

If the application uses 3 phase power, the total element count should be a multiple of 3 to permit a balanced electrical load. The nomograph below may also be used for heater selection in clamp-on strip heating applications.

Strip Heater Nomograph Strip Heate r Sele ction Clamp-on Applications 

1000  900  800     )    F    °    ( . 700    p 600    m   e 500     T    k   r   o 400     W  . 300    x   a    M 200  100  0 

20  18  16  14  12     2   n    I    / 10     W  . 8    x   a    M 6  4  2  0 

Chrome Steel Sheath  Rust-Resistant Iron Sheath 

 A

B

C 

800 °F  700 °F 

6  2 

S      h      e    a    t     h      T       e   

m      p    e   

   2

4 

From the curve, the allowable watt density is 8 W/in2. Based on the tank size, chrome steel sheathed strip heaters 24 inches long without mounting tabs were selected. To determine the number and wattage of strip heaters needed, use the formula: allowable watts per strip = (overall length minus 4" cold section) x 3.45 in2 per lineal inch of sheath x 8 watts/in2. Thus (25-1/2" - 4") x 3.45 x 8 = 593 (600) watts. The total number of strips required is 12,000W ÷ 600W = 20 strips. Order strips similar to OT-2507 in size but rated 600 watts. To avoid a special order, consider using 24 standard OT-2405, 500 watt strips. These heaters would have a watt density of: 500W ÷ ([23-3/4 - 4] x 3.45) = 7.35 W/in2

Selecting C lamp-O n Strips H eaters

   ) 14    n    I    /    W    ( 12    e 10     l    b   a   w   o 8     l    l    A

Using the previous 12 kW example, determine the number of strip heaters required. An 800°F material temperature requires chrome steel strip heaters. From Graph G-130S, a maximum sheath temperature of 1200°F results in an ambient temperature of 1000°F inside the space between the thermal insulation and the vessel, (800°F + 1200°F) ÷ 2 = 1000°F.

To Use the Graph  — 

600 °F 

1. Select  the maximum desired work

500 °F 

temperature on A.

2. Choose  either chrome steel or rust-

0  200

400

600

800

1000

Estimated Ambient Temp. (°F) (Sheath Temp. + Material Temp. ) 2 

I-14 

1200 

resistant iron sheath (points B) on the basis of operating temperatures. 3. Draw  a straight line through points A and B to C. C gives the maximum allowable watts per square inch. 4. Select  desired length heater with equivalent or less watt density.

G eneral Recommenda tions for L iquid H eating Applications Chromalox standard immersion heater ratings match the suggested watt densities for general purpose immersion heating. Extended heater life will be obtained by using the lowest watt density practical for any given application.

Standard Ratings —  Water Heaters Corrosive Solution Heaters Oil Heaters (Light Wt.) Oil Heaters (Medium Wt.) Oil Heaters (Heavy Wt.)

45 - 75 W/in2 20 - 23 W/in2 20 - 23 W/in2 15 W/in2 6 - 10 W/in2

Su ggested A llowa ble W att D ensities for L iquids Max. Temp (°F)

Max. W/In 2 

180 212 200 300 400 500 Bunker C fuel oil 160 Caustic soda 2% 210 10% 210 75% 180 Dowtherm® A 750 Dowtherm® A vaporizing 750 Dowtherm® J liquid 575 Electroplating tanks 180 Ethylene glycol 300 Freon 300 Fuel oil pre-heating 180 Gasoline, kerosene 300 Machine oil, SAE 30 250 Metal melting pot 500-900 Mineral oil 200 400 Molasses 100 Molten salt bath 800-950 Molten tin 600 Oil draw bath 400 600 Steel cast into aluminum 500-750 Steel cast into iron 750-1000 Heat transfer oils (Therminol ®, 500-650 Mobiltherm®, etc.) Vapor degreasing solutions 275 Vegetable oil (fry kettle) 400 Water (process) 212 Water (washroom) 140

40 40 10 8 7 6 10 45 25 15 23 10 23 40 30 3 9 20-23 18-20 20-27 20-23 16 4-5 25-30 20-23 20-23 16 50 55 23

Material  Acid solutions Alkaline solutions (Oakite) Asphalt, tar, and other heavy or highly viscous compounds

20-23 20-30 40-75 75-100

Note — The above watt densities are based on non-circulating liquids. The allowable watt density may be adjusted when heat transfer or flow rates are increased.

Technical

Technical Information  Heater Selection - Oil Heating 

Oil Heating Watt Density Guide

Watt D ensit y & O il V iscosit y T h e v is c o s i y o f o i s a n d h y d r o c a b o n s v a r ie s de y w v is c o

h

y p e a n d t e m p e a tu r e .

s

s rans er h eat p

a tt d e

si es a nd op eratng

cri ca l n

l ea

g ap

en de d f r he at E 1 0 to S

r ly , s h e a t h

ca

s.

oi s m ay requ zati

co nd

ns .

at w de ns

l

a lt a n d o

t

l

f

r carb

he n

y te s t s r e c o m

e a s a t is fa c t o r y w a tt r vari

s o

S AE N o . Engine il

4000

2000

att

6.5 W/In 2 

ne fol

V  i     s 

20

 s  i    t    y   a  t   1  

220

SAE 50 #2 Fuel Oil #4 Fuel Oil #5 Fuel Oil nNr &   #6 Fuel Oil

1500

V  i     s   s  i    t    y   a  t   2   1    (  

 )  

10

 )  

s.

Vis sity   90-120 SSU at 130°F 120-185 SSU at 130°F 185-255 SSU at 130°F 255 SSU-up (Drops to 80 at 210°F) 80-105 SSU at 210°F 40 SSU at 100°F (Kerosene) 45-120 SSU at 100°F 150-400 SSU at 100°F 500-2,000 SSU at 100°F 3,000 SSU at 122°F (Very Viscous)

Viscosity Conversion ec o n ds   ayb o t   i ve rsa l (S S )   31 35 40 50 60 70 80 90 100 150 200 250 500 1,000 5,000 10,000 20,000

125 115

1000

Typical Viscositi es of Vari ous O ils Wei t SAE 10 SAE 20 SAE 30 SAE 40

21

14

15

 (  

15 W/In 2 

14

10

1000

Light 

o w n g c h a r ts p r o v id e g u id a n c e a n d s u g g e s te d att en si es

16

3000

en de d to

en si y.

20 18

3150

ves

ze a t ve ry l w

4650

5000

er fl

s o f h is t y p e a r e e n c o

e r e d , a w a tt d e n s

25 A

reven

om e oi s m ay h ave ad

26 23

ediu m  

y v is c o o

7000

A A o. Lubricant 

6000

e ig h t o i

er hi

a r t c u a r ly if

ASTM

 a r e

e ig h t o i

 o r le s s

S AE N o . ea r i

1000

7000

 a r e s u g g e s te d

e 6 8 W ,

es.

e te r m

g l gh t

-15

k e r C , a r, a s p ca rbo

-23

Visco sity Eq ivalen ts  Heavy  1500

10000 9000 8000

s a g en era

E 3 0 ) . F o r m e d iu m

( g e a r o s , e tc .) ,

nc e h gh

e m p e a tu r e s a r e

r u le , r e g u a r o l e a t e rs r a te d eco

Heavy 

i n e m at i Vis sity  Cen tisto kes  (Cst)  1 2.56 4.30 7.4 10.3 13.1 15.7 18.2 20.6 32.1 43.2 54 110 220 1,100 2,200 4,400

Seconds  ayb o t   Furol (S S F )   — — — — — 12.95 13.7 14.44 15.24 19.3 23.5 28 51.6 100.7 500 1,000 2,000

& nLVRNV & nLS RLV/ VS F L F J rY L  Centipoise x 2.42 = Lbs/ft/hr

2 

15

1

215

20 23 W/In 2  2 

20

10 W 

22 

10

15

2 

10

W 

Visco sity Can e R elated H rizo tally O ly. Visco sities ase on

5 VI S ing le rade O ils.

G raph G -122S — Sur face Tempera tures of Oi l I mmersion Bla de Heater for Vari ous O il Temperat ures & Watt D ensit ies o tes —  1.

25 24 23 22  21    t 20 19    e 18    e    v 17     i    t    e 16 15 14     2 13     W12  11 10

a   i    m   m  

Cu ves based on at ralco

a  e   W    a  t    t     D e  

ach

vec

e q u iv a le n t h a v in g a n E v is c o s i y r a t

s  i    t     y   

0 (5 c en

g

ses a

2 0 0 °F ) .

    p .     m     e       T

     i

    1

    2

2.     p .     m

    e       T      i

e c t iv e L e

h of

e rs io n H e a te r = “ B ” e n s io n .

    p .     m     e

      T      i

     p .       m

    e        T

      i

.

 .    p     m    e     T

rea

e r L in e a r n c h o f

1 - 1 /2 '

de I

a d e s = 3 .7 5

         i

.

rea 1'

2  1

.

e rs io n

300 40 0 500 eath rface Temperature (°F ) 

q. n.

n N o Case, Exceed 27 at s P er

20 0

e rs io n q. n.

e r L in e a r n c h o f de I

a d e s = 2 .6 3

10 0

n

e o l r i

q. n.

600

I-15

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

Technical

Technical Information 

Determining Energy Requirements - Air &Gas Heating   A ir & G a s H ea t in g Air and gas heating applications can be divided into two conditions, air or gas at normal atmospheric pressure and air or gas under low to high pressure. Applications at atmospheric pressure include process air, re-circulation and oven heating using duct or high temperature insert air heaters. Pressurized applications include pressurized duct heating and other processes using high pressures and circulation heaters. Procedures for determining heat energy requirements for either condition are similar except the density of the compressed gas and the mass velocity of the flow must be considered in pressurized applications. Selection of equipment in both conditions is critical due to potentially high sheath temperatures that may occur.

D eterminin g H eat Requirements for  A t m ospheri c P ressu re G a s H ea t in g The following formulas can be used to determine kW required to heat air or gas: E q u a tio n A — kW = CFM x lbs/ft3 x 60 min x C p   x T x SF 3412 Btu/kW Where: CFM = Volume in cubic feet per minute Lbs/ft3 = Density of air or gas at initial temperature C p   = Specific heat of air or gas at initial temperature T  = Temperature rise in °F SF = Suggested Safety Factor

G r aph G 17

S  — A ir H ea tin g

ased n Air en sity 0 . 0 8 L b s /F t  a n d a pe c i fi c He at o f 0 . 2 3 7 tu / L b / ° F

    e     s      i

   e    e    s    s      i     i

   e    s     i

15

  e    i  s

13

  e    i  s

110

  e   i  s

Velocity (fps) =    s    t    t    a

  i s e   2

    i

 i s e

 2   i s e   F R   0   1  5  i s e  F  R  1 0 0  R i s e  7 5  F  i s e  5 0  F R

10 10 10 0

300 5 00 70 0 900 110 0 Ai r V l u m e ( C i c F e et P e r M i n u t e)  

r ess Air Heatin g Cal latio n ample  A drying process requires heating 450 ACFM of air1 from 70°F to 150°F. The existing duct- work measures 2 ft wide by 1 ft high and is insulated (negligible losses). To find heating capacity required, use Equation A: kW = 450 ACFM x 0.08 x 60 x 0.24 x 80 x 1.2 SF 3412 Btu/kW

For quick estimates of air heating requirements for inlet temperatures up to 120°F, the following formula can be used.

kW = 14.58

kW = SCFM x T  x 1.2 SF 3,000

Finstrip® (CAB heaters), Fintube® (DH heaters) or tubular elements (TDH, ADH and ADHT heaters) will all work satisfactorily in low temperature applications. Finstrips or finned tubular elements are usually the most cost effective. Tubular elements are recommended for high temperatures. Once the desired type of heating element is selected, the next step is to calculate the air velocity and estimate sheath temperatures to verify that maximum operating temperatures are not exceeded. Calculate the air velocity over the elements and refer to allowable watt density graphs for estimated operating temperature.

Where: SCFM = Volume of air in cubic feet per minute at standard conditions1 (70 F at standard atmospheric pressure) 3,000 = Conversion factor for units, time and Btu/lb/°F 1.2 SF = Suggested safety factor of 20% raph G 17 6 S  When airflow (ft3 /min) and temperature rise are known, kW requirements can be read directly from graph G-176S. o te  — Safety factors are not included. te 1 — Based on an average density of 0.08 lbs/ft3 and a specific heat of 0.24 Btu/lb/°F. For greater accuracy, use Equation A and values from the Properties of Air Chart in this section. I-16

 A w Temperat re Heater electio n ypical heater selection for the previous example might be a type CAB heater with finstrip elements. Available 15 kW stock heaters include a CAB-1511 with chrome steel elements or a CAB-152 with iron sheath elements, both rated at 26 W/in2. From the product page, the face area of a 15 kW CAB heater is 1.19 ft2:

H eater Selection

Calcu latin g Air Velo ity  Air velocity can be calculated from the following formula: Velocity (fps) =

Flow (ACFM) Area of Heater (ft2) x 60 sec.

450 ACFM = 6.3 fps 1.19 ft2 x 60 sec.

stimatin g eath peratin g Temperat re  The maximum operating sheath temperatures for finstrips are 750°F for iron and 950°F for chrome steel. Using graph G-107S for iron sheath finstrips, a 150°F outlet temperature and a watt density of 26 W/in2 requires a velocity in excess of 9 ft/sec to keep sheath temperatures below maximum permissible levels. With only 6.3 fps in the application, a CAB-152 heater with iron sheath elements is not suitable. Using graph G-108S for chrome sheath finstrips, approximately 3 ft/sec. air velocity results in a maximum of 900°F sheath temperature. Since this is lower than the actual velocity of 6.3 fps, a CAB-1511 with chrome steel finstrips is an acceptable heater selection. (Use graphs G-100S, G-105S,G106S and G-132S for air heating with regular strip and finstrip heaters.) Hi h Temperat re Heater electio n  Type TDH and ADHT heaters with tubular elements are recommended for high temperature applications. Steel sheath tubulars may be used where the sheath temperature will not exceed 750°F. Finned tubulars can be used in applications up to a maximum sheath temperature of 1050°F. INCOLOY® sheath tubulars may be used for applications with sheath temperatures up to 1600°F. Allowable watt densities for tubulars and finned tubulars can be determined by reference to graphs G-136S and G-151-1 through G-156-1. stimatin g eath peratin g Temperat re  Select a heater for a high temperature application with an inlet air temperature of 975°F and a velocity of 4 ft/sec. Since the temperature is above 750°F, an INCOLOY ® sheath must be used. Using graph G-152-1 the allowable watt density is 11 W/in2 for sheath temperatures of 1200°F or 22 W/in2 for temperatures of 1400°F. In this application, a stock ADHT heater2 with a standard watt density of 20 W/in2 can be used. o te 2  — Special ADHT duct heaters, derated to the required watt density, can be supplied when element ratings less than the standard 20 W/in2 are needed.

Technical

Technical Information  Allowable Watt Density & Heater Selection - Air Heating  A ir & G a s H ea t in g w it h S t ri p a n d Finstrip  H eaters Custom Designs — Strip and finstrip heaters are frequently mounted in banks by the end user. Graphs G-105S and G-106S on this page can be used in conjunction with other graphs to determine maximum watt density for virtually any custom design low temperature heating application. Graph G-105S — Strip Heaters To use this graph: 1. Select maximum desired outlet air temperature on line A. 2. Choose either chrome steel sheath or rust resisting iron sheath (points B) on the basis of operating conditions. 3. Select minimum anticipated air velocity on B. Note — natural circulation is equal to approximately one foot per second. 4. Draw a straight line through points A and B to a reading on C. Read maximum allowable watts per square inch from line C. 5. Select desired length heater with an equivalent watt density or less from the product page in this catalog.

G r aph G -

S  —

S t r i p H e a t er A i r H ea t i n g- S el ect i on o f W a t t D en si t y   20

700

600     )     F     °     (    e    r    u    t    a    r 500    e    p    m    e     T    r     i     A 400    t    e     l    t    u     O 300

Chrome Steel Sheath

Iron Sheath

A     i     r    V     1     l     6     e    o    i     9     c    t      y     (     4     F     . P     . S     1     .  )    

15

    2    n     I 10     /     W

A  i  r   V  e   1  6   l  o  c  i   t    y  (   9   F   .P   .S   4   . )   1  

5 200 100 0

0 A

G r aph G -

B

S  —

C

F in st rip  H eater Air H eati ng-Selection of W att D ensity 

700

Graph G-106S — Finstrip® Heaters To use this graph: 1. Select maximum desired outlet air temperature on line D. 2. Choose either chrome steel sheath or rust resisting iron sheath (points E) on the basis of operating conditions. 3. Select minimum anticipated air velocity on B. Note — natural circulation is equal to approximately one foot per second. 4. Draw a straight line through points D and E to a reading on F. Read maximum allowable watts per square inch from line F.

600

30

    ) 500     F     °     (    e    r    u    t    a    r    e    p    m    e     T    r 400     i     A    t    e     l    t    u     O

Chrome Steel Sheath

Iron Sheath

300

5. Select desired length heater with an equivalent watt density or less from the product page in this catalog. Recommendations for Custom Installations — Strip heaters should always be mounted sideways in the ductwork with the narrow edges facing the air stream. The total number of elements installed should be divisible by 3 so that the heater load will be balanced on a three phase circuit.

A     i      r     V      e    l      o     c    9     i      t      y      (      F      . P      4     . S      A    i     .  )     r    V     e    1     l     6     o    1     c    t     9     i      y     (     F     . P     . S     4     .  )    1     6     

25

20     2

   n     I     /     W 15

1    

200 10       N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

100 5

0 D

E

F

I-17

Technical

Te

i al In rmati

All a le Watt e sity Heater e e tio n - Air Heatin G raph G -100S — Strip Heater (Chrome) Air Heating All owable Watt D ensiti es for 1000°F Sheath Temp.

Graph G-132S — Stri p H eater (Iron) Air H eati ng All owable Watt D ensiti es for 700°F Sheath Temp.

F  P 

   n    I

 W a tta g e Ra tin g of S trip He at e r = W /In  x Heated Area S t r ip H e a te r s < 3 - 1 / 2 " , H e a t e d L e n g th = O v e ra l l L e n g th - 4 " S t r ip H e a t e rs - 1 / 2 " , He a t e d L e n g t h = O v e r a l l L e n g t h - 1 / 2 " W i de S t ri p H e a te r = . 4 5 i n /in. " W i d e S t ri p H e a te r = . 3 1 i n /in.

S  D  i s t r  i b 

F  P  S 

   W     h    c    n    I    e    r    a    u    q    S    r    e    P    s    t    t    a    W

F  P   S  

u t  e  d  A  i r  V  

F  P  S  F  P  S 

F  P   S  

e l  o 

D  i   s  t    r  i    b  u   t   

e   d    

 A    i    r   

c i  t  y  

V     e    l     o   c   

i     t      y   

F  P  

o r F r e  e  A i r 

S  

   n    I    W

 W he n C al cul a tin g He a te r C a pa cit y, Us e the Maximum Outlet Temperature and the Lowest Air Velocity. For Close Grouping of H e a t e rs , U s e 8 % o f t h e C a l c u la t e d V a lu e . 0

100

200

300 400 Outlet Air Temperature (°F)

500

600

700

F  P  S 

    h    c    n    I    e    r    a    u    q    S    r    e    P    s    t    t    a    W

o r   F   r e e 

 A i  r 

Graph G-107S — Fi nstri p® (Iron Sheath) Air Heating All owable Watt D ensiti es for 700°F Sheath Temp.  W a tta g e Ra tin g of F ins trip  W /In  x 3 .6 0 x H e a te d L e ng th F  P 

   n    I

F  P   S  

S 

F  P  S 

   W     h    c    n    I    e    r    a    u    q    S    r    e    P    s    t    t    a    W

F  P  S 

D  i   s  t  r   i  b u   t  e  d    A i   r  V  

 W he n C a lcu la tin g He a te r C a pa cit y, Us e the Maximum Outlet Temperature and the L owest  A ir V e loc ity . F or C los e Gro up ing of He a te rs, U s e 8 % o f th e C a lc ul a te d V a lu e .

e l  o  c  i  t    y  

o r F r  e e  A i  r 

0

200

300

400

500

600

700

800

900

1000

Outlet Air Temperature (°F)

Notes Strip Heaters < -1 /2 ", Heated Length = Overall Length - 4 S trip Heaters -1 /2 ", Heated Length = Ov erall Length -1 /2 " Wide Strip Heater = .4 5 in./in. " Wide S trip Heater = .3 1 in./in.

 W he n C a lcu la tin g He a te r Ca pa cit y, U se the Maximum Outlet Temperature a nd the Lowe st  A ir V e loc ity . F or C los e G roup ing of He a te rs, U s e o n ly 8 % o f t h e C a l c ul a t e d V a l u e 0

100

200 300 400 Outlet Air Temperature (°F)

500

600

G raph G -108S — Fi nstri p® (C hrome Steel) Ai r H eating All owable Watt D ensiti es for 900°F Sheath Temp.

G raph G-136S — Tubular H eater Ai r H eating She ath Temperature of Tubular Elements at Va rious Watt Densities in Free or Forced Air at 8 °F

 W a tta g e Ra tin g of F ins trip  W /In  x 3 . 6 0 x He a t e d L e n g th F  P  S 

F  P   S  

F  P  S 

   n    I    W

F  P  S 

    h    c    n    I    e    r    a    u    q    S    r    e    P    s    t    t    a    W

o r F r e  e  A i r 

0

100

200

   W     h    c    n    I    e    r    a    u    q    S    r    e    P    s    t    t    a    W

e l  o  c  i  t    y  

300

400

   S     i   r     S    S     S     P  A      P     P      P     l      F     l      F     F     F     i  t    S

   n    I

D i   s t r   i  b u   t  e  d     A i   r  V  

 W he n C a lcu la tin g He a te r C a pa ci ty, U se the Maximum Outlet Temperature and the L owest  A ir V e loc ity . F or C los e G roup ing of He a te rs, U s e 8 % o f t he C a l cu la t e d V a l ue .

0

200

400

600

800

1000

Shea th Temperature (° F) 500

Outlet Air Temperature (°F)

I- 1

100

600

700

1200

1400

Technical

Technical Information  Allowable Watt Density & Heater Selection - Air Heating G raph G -154-1 — Fintube® & Tubular H eaters Sheath Temperat ures wit h 16 F PS D istri buted Ai r Velocit y

G raph G -151-1 — Fi ntube® & Tubular H eaters Sheath Tempera tur es with 1 FP S D istributed Ai r Velocit y     h    t    g    n    e     L    e    v   s     i    t    t    c    i    e   n     f     f     U     E   r     f    l    o   a     2    u     b    n     I    u     /    T 80     W     d 70    n     i   e    n 60    n    y     i    t     i    s    F 50    n 40    e     D 30    t    t 20    a     W 10 0

Limit for Finned Tubular for Normal Life Expectancy

1400 F 

40 35 30

1200 F 

25    s    t     i    n 20     U    r    a     l    u 15     b    u     T 10

10 0 0  F  910  F  80 0  F 

6 00     F  4 00     F  2 00     F  

0

200

5

400 600 800 1000 Outlet Air Temperature (°F)

1200

1400

G raph G -152-1 — Fi ntube® & Tubula r H eaters Sheath Tempera tures wit h 4 F PS D istri buted Air Velocit y     h    t    g    n    e     L    e    v   s     i    t    t    c    i    e   n     f     f    U     E   r     f    l    o   a     2    u     b    n     I    u     /     T     W     d 80    n   e     i    n 70    n 60    y    i    t     i     F    s 50    n    e     D 40    t 30    t    a     W 20 10 0

1 40  0      F  

Limit for Finned Tubular for Normal Life Expectancy

12 00     F 

40 35 30    s 25    t     i    n     U 20    r    a     l    u     b 15    u     T

10 00     F 

8 40     F  8 00     F 

10

6 00     F  4 00    F   2  0  0   F  

0

200

5

400 600 800 1000 Outlet Air Temperature (°F)

1200

1400

G raph G -153-1 — Fi ntube  & Tubular H eaters Sheath Temperat ures wit h 9 F PS D istri buted Ai r Velocit y

    h    t    g    n    e 1 0  0       L 0  F      e    v     i    s    t    t    c    i    e   n     f     f     U 8  0  0       E    r F       f    l    o   a 7  0       2    u 0       b    n     I    u 80 6   F       /    T 0  0       W     d F   70    n   e     i    n 60    n    y     i    t 4       i    s    F 50 0  0  F      n 40    e     D 30 2   0    0       t    t 20 F       a 10     W 0 0 200

00

1 2 0  0  F  

1  4   0  0  

F  

Limit for Finned Tubular for Normal Life Expectancy

40 35 30

1 00    0  F  

25    s    t     i    n     U 20    r    a     l    u 15     b    u     T

8 4 0  F   8 00      F   6 00    F   4 00      F   2  0   0  

10 5

F  

200

400 600 800 1000 Outlet Air Temperature (°F)

1200

1400

F  

1    4    0    0   

F    

40

Limit for Finned Tubular for Normal Life Expectancy

35 30 25    s    t     i    n 20     U    r    a     l    u 15     b    u     T 10 5

400 600 800 1000 Outlet Air Temperature (°F)

1200

1400

G raph G -155-1 — Fintube® & Tubular H eaters Sheath Temperat ures wit h 25 F PS D istri buted Ai r Velocit y     h    t    g    n    e     L    e    v   s     i    t    t    c    i    e   n     f     f     U     E   r     f    l    o   a     2    u     b    n     I    u     /    T 80     W     d 70    n   e     i    n    n 60    y    t    i     i    s    F 50    n 40    e     D 30    t    t    a 20     W 10 0

1  2    0    0    F   

1 0  0   0   F  

40

Limit for Finned Tubular for Normal Life Expectancy

35 30    s 25     i    t    n     U 20    r    a     l    u 15     b    u     T

8 0  0   F   6  4 0   F   6  0  0   F   4 0  0   F  

10 5

2  0   

0   

F     

0

200

®

    h    t    g    n    e     L    e    v   s     i    t    t    c    i    e   n     f     f    U     E   r     f    a     l    o     2    u     b    n     I   u     /     T 80     W     d    n   e     i    n 70    n 60    y    i    t     i     F    s 50    n    e 40     D 30    t    t    a 20     W 10

1  2   0  0  

400

600 800 1000 Outlet Air Temperature (°F)

1200

1400

G raph G -156-1 — Fintube® & Tubular H eaters Sheath Temperat ures wit h 36 F PS D istri buted Ai r Velocit y     h    t    g    n    e     L    e    v   s     i    t    t    c    i    e   n     f     f     U     E   r     f    a     l    o     2    u     b    n     I    u 80     /    T     W     d 70    n   e     i    n 60    n    y    t    i     i    s    F 50    n 40    e     D 30    t 20    t    a     W 10 0 0

1  0    0    0    F   

40

Limit for Finned Tubular for Normal Life Expectancy

35 30

8  0   0   F   6  4   0   F   6  0   0  

25    s    t     i    n     U 20    r    a     l    u 15     b    u     T

4  0   0  

10

F  

F   

2    0    0   

5

F     

200

400 600 800 1000 Outlet Air Temperature (°F)

1200

1400

I-19

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

Technical

Technical Information Determining Energy Requirements - Air & Gas Heating Ai r & G as H eati ng — Cr yogenics In du strial ases are u su ally st red in a liq id state w ith eat b ei g added to vapo rize an d il ff t e g as as u sag e re ires. G e era eat e atio s app y exc ept th at pipes, tu es a d vesse s tai i g t e ry e ic fl id r as freq en tly represen t a h eat s r e rat er th an a h eat l ss. If t e size an d materials t e ta ks r vesse s are kn , t en eat al atio s f r t e temperatu re rise an e perfo rmed as in stan dard vessel h eati g r iler pro ems. T e f in g examp e is typical f a ry en ic h eatin g app icatio . Problem  —  Vap rize a d pre eat

,0 CF H o f i id itr en ( 2 ) r m - 3 ° F t o °F at atmo sp eric ditio s. T e pro per ties f N 2  fr m Cry en ic G as Tab es are: i i g p i t, - 3 2 ° F pec i fi c h eat t °F .4 4 (liq .), .2 8 (g as) ate t eat f vap r izati n = .7 t /lb Atm. de sity of N 2  at 2°F = 0 . 4 l t  . Solution  — Am t f li id 2  to e vap rized 3 0 0 0 0 CF H x 0 .0 7 8 4 b / ft   = 2 2 s/ h r   . R a is e  li

id r m - 3 4 ° F to - 3 2 0 ° F ( T  p i t) ∆  = 2 ° F .

ii

kW = Wt C   x S F  p x ∆ T  12 t kW   Wh ere Wt = Wei t o f material in s C   p = pec i fi c eat f t e i id 2   = Temperatu re rise in ∆ T  F = ested safety fa t r f 2 kW = 2

2 s x 0 . 4 x 2 5 x 1 .2 = .8 kW 12 t / kW  

. Vaporize  th e liq id

kW = 2

2 s x 8 .7 x 1.2 = 12 t / kW  

.9 kW

2 s x 0 .2 8 x 3 0 x 1 .2 = 0 kW 12 t / kW  

T tal kW r re ired = .8 +

.9 + 0 = 1 .

Equipment Recomm endations —  G en eral y

ry en ic app icatio s u ti ize b th a vap rizer it an d a as preh eater. Hig h att den sity eaters immersed in th e cry en ic fl id a e sed fo r th e vapo rizer. ta dard ir atio eaters a d w att den sities are rec mmen ded fo r g as preh eati . P ro te t t e h eater termi als fro m fro st an d mo istu re ith elemen t seals a d liq id ti t termi al vers. I- 2

Air & G as H eati ng — Batch O vens st o v en app ic a ti s c o sist o f h eati g rk pr du t i side an in su ated en su re. Heat ss al atio s in vo ve th e determin atio n t e h eat req ireme ts to eat t e e s re a d rk pr d t sin g eated air ir ated y atu ral r fo r ed ve tio . An y make p r ven ti atio n air m st also e co sidered. Th e foll i g e amp e t i es t e a ati n th e eat re ired fo r a typi al ven eati applic atio . Problem  — An ven ith i side dimensi s 2 ft H x 3 ft W x 4 ft D is mai tai ed at °F. T e o ven as sh eet steel als w ith 2 in es i s ati n a d is ve ti ated w ith 0 fh (ft /h r) f ° F air ic h ex h a sts to t e tside t rem ve fumes. T e o ven is ch ar ed w ith 2 s o f c ated steel parts n a steel tray ei i g 0 s. T e proc ess req ires th e parts to e eated r m ° F t o 3 ° F i n 3 4 r.

Wei t f steel = 2 0 s pec i fi c eat f steel — .12 t °F Wei t o f air = . 0 s f t   at ° F pec i fi c h eat f air = .24 t / l ° F Temperatu re rise = 28 r ac e l sses ith 2 i h i s ati n = 18 W ft 2 /h r at 2 °F temperat re differe e ( raph - 12 ) rfa e area f o ven = 2 ft 2  Time = 4 r ( . ) Air w rate = 0 t  /h r  Solution . Calculate  kWh re

2 

. R a is e  th e temperatu re f t e N 2  fr m i in g po in t -3 20 ° F to 7 0 ° F — ∆ T  = 3 9 0 ° F.

kW = 2

rdin ary ar n steel is su ect to ritt e fra tu re at temperat res el w -20 F an d is en er al y n t reco mmen ded. tain ess steel, h ig ickel eari g al ys r a mi m a ys may e u sed. U se Te  fo r g askets asTefl remain s pliab le at lo w temperat res. M a t e ri a l R e c om m e n da t io ns —

kW = 2 0

ired to eat metal.

s x 0 .12 t °F x 280 °F = 2. 6 kW 12 t kW 

. Total kW = 2. 6 + 0 . 7 +

. 0 =

. 3 kW  

For Oven Applications , add

% to c o ver d r l sses a d oth er co ti e ies. kW re ired (i di g safety fa to r) is  kWh = kW = t 

. 3 kW = . 5 rs  

. 7 kW x 1 .3 =

. 8 kW

Equipment Re commendations —  S evera

pr ess air eaters, in lu di g strip eaters, strips, b are t ars o r type O V o ven eaters are su itab e fo r ven eati g applicati s.

Pressure D rop for Pr ocess Ai r H eaters T e press re dr p t r h T Ha dA H pro ess air eaters ith are t ar r ed tu ar elemen ts, CAB eaters ith strip elemen ts, a d AD H a d H air eaters it ed t ar e eme ts w ill vary c sidera y depe di g n pr d t desi n a d c o str ti . Ch ro ma x sa es en in eerin g an pro vide pressu re dro p c al atio s fo r virt al y an y du t h eater ( r circu atio n eater) applicati . rap s - 112 , - 1 1, - 22 - 2, a d - 22 A H n t e f o l l i g pa e pr vide idan e f r estimatin g th e press re dr p fo r man y C ro ma x pr ess air eaters 1. raph - 1 1 c a n e sed r m st ed tu ar app icati s pro vidi g th e e emen ts are m ted in a t ree r six r w c o rati . Transitions in Ducts —  In so me air distrib ti

systems, th e d t h eater may e co sidera ly ar er r sma er th an th e ass iated d tw rk. Th e d t h eater can e adapted to differe t size du tw rk y in stal in g a sh eet metal tran siti . T e tra sitio n mu st b e desig ed so t at t e sl pe n th e u pstream side o f t e e ipme t is imited to ° (see b el ). n t e leavin g side, t e s pe s d t e m re t an ° . Note 1  —  Co ta t th e fa to ry fo r pressu re

dro p a atio s f r d t h eaters mo ted Calculate  kWh re ired to eat ven tilated air  e t ise r in series an d fo r CH as ir ati n eaters. T ese appli atio s req ire spe ia kW= 4 c f h x . 8 L b s x .2 C  p x 2 8 ∆ T x . 7 5 t = 0 . kW al atio s f r pro per app icati n an d air 12 B t kW   an d er sizi . Wh ere Recommended D imensions c f h = Air w rate ( ) for D uct Tra nsit ions s/ ft   = e sity f air ( . ) C   p = pe i c eat f air ( .2 ) 45° 30° ∆ T   = Temperatu re rise (28 ) Max. M a x . = Time in rs ( . )   . Calculate  su rface l sses. in e t e o ven is

already at temperatu re, l sses are at fu ll val e.

kW = 18 W/ft 2 /hr x 5 2 ft 2  area x 0 . 5 r  = 1 0 W/kW 

. 0 kW

 A ir F low 

30° Max.

45° Max.

Technical

Technical Information

Determining Pressure Drop - Air and Gas Heating G r aph G A D H — P r essu r e D r op V s . V el oci t y A D H a n d A D H T T u b u la r E l em en t A i r H ea t er s 2.0

ADH or ADHT Mounted Crosswise in Duct

Based on 1-5/8" spacing and 4.7 fins per linear inch

0.5

  5  =  9.   T M   H   A  D

Air    r    ) 0.7    e    t    1 0.5 Flow    a    6     3     W     f    0  .    o    0 0.3    s   x    e    r     h    t    c   e    n   a     I     W     f   —    o    p    s 0.1    o    e    r    h     D   c    e     I    r    n 0.07    u   =    s     i    s    s 0.05    e    P    r     P    ( 0.03

0.01

1.0

 5  "  8. 3  7  M =  1   H   "  A D

1.0

G r aph G S 3  — Pressure D rop V s. Velocity F instrip a n d C A B A i r H e a t er s

. 5  "  M = 9  A  D  H

Triple Row Double Row Single Row

0.3    r     )    e    t    a    1     6 0.1     3     W     f    0  .    o    0 0.07    s   x    e   r 0.05     h    t    c   e    n   a     I     W     f 0.03   —    o    p   s    o    e    r    h     D   c    n    e    I    r    u   =    s    s    i    s 0.01    e    P    r     P    ( 0.007 0.005

0 0

5 fps 10 fps 300 fpm 600 fpm

15 fps 20 fps 25 fps 30 fps 35 fps 900 fpm 1200 fpm 1500 fpm 1800 fpm 2100 fpm Air Velocity (Std. Air) Note — Contact factory for pressure drop calculations for ADH/ADHT air heaters mounted lengthwise in duct and ADHT heaters where M is greater than 9.5"

0.003

0.001

G r aph G S 1  — Pressure D rop V s. Velocity F i n t u b e  Elements and A ir H eaters

0 0

5 fps 10 fps 300 fpm 600 fpm

Air Velocity (Std. Air)

0.7

Finned Tubulars Mounted 0.5 Crosswise in Duct    r     )    e    t    a    1     6 0.3     3     W     f    0  .    o    0    s   x    e   r     h    e    c   t    n   a 0.1     I     W     f   —    o    p   s 0.07    o   e    r 0.05     D    h    c    n    e    r    I    u   = 0.03    s    s    i    s    e    r    P     P    (

G ra ph G -  — Pressure D rop V s. Velocity T D H T u b u la r E l em en t A i r H ea t er s

  "  3  7  5   1 8.   M =

  w s  R o   S  i  x

Air Flow

 e e   T  h r

  "  = 9. 5

 s  M  R o w

0.20

TDH Mounted Lengthwise in Duct

0.18

Air Flow

0.16

   r    ) 0.14    e    1    t    a    6     3     W     f    0  .    o    0 0.12    s   x    e   r 0.01     h    t    c   e    n   a 0 5 fps 10 fps 15 fps 20 fps 25 fps 30 fps 35 fps     I     W0.10     f 0 300 fpm 600 fpm 900 fpm 1200 fpm 1500 fpm 1800 fpm 2100 fpm   —    o    p    s    o Air Velocity (Std. Air)    e    r    h     D   c    n 0.08 Note — Contact factory for pressure drop calculations for finned tubular element air    e    I    r    u   = heaters mounted lengthwise in duct.    s    s    i    s    e    P    r G ra ph A D H T B  — A D H / A D H T T er m in a l B ox T em per a-     P    ( 0.06

TDH-6 TDH-12 TDH-18 TDH-24 TDH Mounted Crosswise in Duct Air Flow

    4     2    8      1        H    2     H      D    1       D  T  T     H    e     D    s  T      i    s  e     i   e     w    w   s      h    i     h     t     t    w    g     g      h    n    n    t    e    n  g       L     L  e   e

    L

    g       n      i      t

      a

      R

    y 

    n

     A

      e

    s       i

    w

   s     s    o     r  C    s     w    o  R    e

tures F ield W iring Selection G uide 600     )     F     °     ( 500    e    r    u    t    a 400    e    r    t    a   e    p    m   m     i    x    T    e    o    r    x 300    p    p   o     A    B     l    a 200    n     i    m    r 100    e     T

15 fps 20 fps 25 fps 30 fps 35 fps 900 fpm 1200 fpm 1500 fpm 1800 fpm 2100 fpm

0.04

  H - 6  e T  D   s  i  g t  h w   L e n

    e      r        h

    T   s  e  r   a  t  e   r H  A  i    H   D   A

0.02 0

 t e r s  H e a  T  A i r A D H

0 0

5 fps 10 fps 300 fpm 600 fpm

15 fps 900 fpm

20 fps 25 fps 30 fps 35 fps 1200 fpm 1500 fpm 1800 fpm 2100 fpm

Air Velocity (Std. Air)

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

Data only valid for ADH or ADHT air heaters installed in bottom or sides of duct

0 0

200

400

600

800

1000

1200

Outlet Air Temperature (°F)

I-21

Technical

Technical Information

Determining Energy Requirements - Air & Gas Heating  Air & Gas Heating with Circulation Heaters  To calculate the heat energy requirements for heating compressed air or gases, the first step is to determine the flow rate in pounds per hour. If the density of the air or gas under the actual pressure is known, the kW requirements can be calculated directly. The following example illustrates this procedure.

Chart 236  — Circulation Heaters Free Internal Cross Sectional Area 

SCFM = 45 x (35 + 14.7) x (70 + 460) 14.7 psia (50 + 460)

i pe B o dy   o m. I (S td.)  2 3 5 8 10 12 14 16 18

SFCM = 158.1 ft3 /min Using the calculated SCFM in place of ACFM in equation A, the kW required is: kW = 158.1 x 0.073 x 60 x 0.2438 x (300 - 50) x 1.2 3412 kW = 14.8 kW

ample  —  Heat 20 ACFM of air at 30 psig from Determining Maximum Sheath 60°F to 210°F. From the Properties of Air Chart, & Chamber Temperatures  the density of air at 60°F and 30 psig is 0.232 When heating air or gases in insulated pipe lb/ft3 with a specific heat of 0.24 Btu/lb/°F. The kW required can be calculated from the formula: chambers or circulation heaters, the pipe wall temperature will normally exceed the outlet kW = ACFM x lbs/ft3 x 60 min x C p   x T x SF gas temperature. Excessively high wall and/or 3412 Btu/kW sheath temperatures can create an unsafe or dangerous condition. Maximum sheath and Where: chamber temperatures can be estimated using ACFM = Actual flow in ft 3 /min at inlet the mass velocity of the gas and Graph G-237. temperature and gauge pressure (psig) In the above air heating example, assume a 3 Lbs/ft  = Actual density at inlet temperature 4.5 kW Series 3 heater rated 23 W/in 2 has and gauge pressure (psig) been selected. From Chart 236, the free cross C p   = Specific heat of air or gas at inlet sectional area of a Series 3 (3 inch) heater is temperature and gauge pressure (psig) 0.044 ft2. Calculate mass velocity from the T  = Temperature rise in °F following equation: SF = Suggested Safety Factor kW = 20 x 0.232 x 60 x 0.24 x (210 - 60°F) x 1.2 3412

Mass Velocity = Flow lbs/hr ÷ 3,600 sec (lbs/ft2 /sec) Free area ft2 hr

kW = 278.4 lbs/hr x 24 x 150 x 1.2 = 3.52 kW 3412

Mass Velocity = 278 lbs/hr  ÷ 3,600 sec 0.044 ft2 hr

When the density and specific heat of a gas at a specific temperature and pressure are unknown, the actual flow rate can be converted to a known pressure and temperature using the physical laws of gases.

(

T tal Area  (F t 2 )  0.023 0.051 0.139 0.355 0.566 0.785 0.957 1.268 1.622

re e   Area  (F t 2 )  0.018 0.044 0.124 0.303 0.481 0.696 0.847 1.091 1.357

Mass Velocity = 1.75 lbs/ft2 /sec On Graph G-237, locate the mass velocity (1.75) on the horizontal axis. From that point, locate a 23 W/in2 curve. Read across to the vertical axis (sheath temperature rise above outlet temperature) to 880°F. Adding 880°F + 210°F (outlet temp.) = 1090°F sheath temperature. Averaging the sheath and outlet temperatures (1090°F + 210°F ÷ 2), yields a maximum chamber temperature of 650°F. Since the maximum chamber wall temperature is less than 750°F, a stock GCH heater with a carbon steel vessel and INCOLOY® elements rated 23 W/in2 can be used.

)

Graph G-237  — Sheath Temperature Vs. Mass Velocity  1400

12

ample  —  Heat 45 ACFM of Nitrogen (N 2) at 35 psig from 50°F to 300°F. From the Physical and Thermodynamic Properties of Common Gases Chart, the density of Nitrogen at 70°F is 0.073 lb/ft3 with a specific heat of 0.2438 Btu/lb/°F. Convert 45 ACFM at 35 psig and 50°F to SCFM of Nitrogen at 70°F using the following formula: SCFM = ACFM x Actual psia x Standard T 14.7 psia Actual T SCFM = Std. ft3 /min at 14.7 psia and 70°F ACFM = Actual flow in ft 3 /min at inlet temperature and gauge pressure (psig) Actual psia = gauge pressure in lb/in2 + 14.7 psia 14.7 psia = absolute pressure in lb/in2 T = °Rankine (°F + 460)

W    

   e    s     i     )    e    r    ( 1 0 0 0  .    t   p    a    r   m    e   e    p     T    m    e   s    a     T    t   t    a   e    e   t

2    2   

   e    m    v    m     i    A    a

2   

W    2   

W    2    2    W    2    2    W    2    1   W    2    1   W    2   1  2   W   

    d    e     d    e    m    m    e    t

2  

W  

2  

W  

2  

W  

2  

20

0

1. 0

2. 0

3 .0

4.0

5.0

ass Vel city (Lb s/ t  e c )   2 

I-22 

. 0.475" leme ts  2 3 6 18 27 36 45 72 108

6.0

7.0

Technical

Technical Information

Determining Heat Energy Requirements - Steam Heating Steam Heating with Heat Exchange rs —  he l an d us ed

be he at exch an ge s are f eq

o he at qu ds

om

cen

al

he e steam

c e s s e s . E le c t c s t e a m

bo

Example  —  A

chem

pro-

so urce.

1 4 0 °F to 1 8 5 °F fo r a c o n

p r o c e s s . T h e e x c h a n g e r is s u p p s ig s e a m

rom

a la r g e c e n r a l

c o m p a n y w s h e s to s h u t d o n th e s u

er

ne ed ed

on hs.

he bo

n?

om

e fo l o w n g

Q  =

00

b/hr)

x 1 .2 S

50 0 =

ed n kW

o n v e rs io n 1 gp m

hr

a c to r —

x 8 .3 4 5

gp m

e c ific h e a t (

G =

u / lb / °F ) —

1

p e c ific g a v i y o f q u d —

F = F lo w o f

n = 500

qu d —

r w a te r 1

o r w a te r

gal

∆ T  = T e m e r a tu r e c h a n g e o f l u id ° 1 8 0 °F - 1 4 0 ° F = 4 5 °F ) C = C o n v e r s io n f a c to r — k W b o f s te a m 5 0 p s ig ( f o m k W b C o n v e r s io n T a b le ) H = L a te n t h e a t o f s te a m a t p e a t n g p r e s s u — u / b ( F ro m a tu r a te d S e a m T a b le ) F = a fe ty fa c to r o f 2 0

Q  =

(50 0 l

r ) ( 1 ) ( 1 ) ( 1 0 ) ( 4 5 °F ) (

83 9 kW

r fl w

he h um hu

di y.

FM

s a fe ty fa c to r is r e c o m

or un kno

n h e a t lo s s e s a n d

o n e n t o f A r ” in

s p er 1

y co .

a ta S e c t

n,

a in s 0 0 2 1 lb s o

r a t 8 0 °F a n d 7 5

0 cu

a te r v a p o r o b

c feet of ai

0 .0 9 8 b s 1 0 0

 -

8

A 20 %

om

850 C FM

s a fe ty fa c to r s re c o m bs hr x 1 2

x 60 m

hu

s o f steam

°F

R.H.

70 70 72 72 75 75

35% 40% 35% 40% 35% 40%

he rm al en ergy i

f va

h e s te a m

r iz a t i

) s tr a n s -

c o n d e n s e s to

a te r

d is c h a g e

om

ost

bo

e r s c o n a in s w a te r

ecu es o

at

as n

s is c a e d

t eva

r a te d .

“ w e t s te a m ” a n d s r a te d b y 85%

ua

o 95% .

y fa c to r s

e t s te a m h a s a

e r t e r m a l r a n s e r e ffic ie n c y a s i a b e in m a n y c o e t s te a m

To i

d is u

e-

e r c ia l a p p l c a t o n s . T h

e x c e s s v e “ c a r ry o v e r ” o f

d w a te r a n d

st

c a n c r e a te m a jo r p e r fo r m a n c e

p r o v e s te a m

qu al y,

g a ci cu at

c la v e s .

e t s te a m

a is in g

he

can b

n h e a t e r. F o r e x a

a t 9 0 p s g h a s a s a tu r a t o n

of 33 1° .

end ed

e,

e m p e a tu r e

e m p e a tu r e o f 9 0 p s

o 3 4 0 °F o r 3 5 0 °F w n i crease

lproduce 1 00 f

° o

°

F = 59 98

he

on s.

bs hr eam

sses.

equ

e-

s ta n t a i

cat on can b e deter

o o s te r H u m

FM

a b o r a to r y r o o m

s su

ne

35 %

ng

e h g h s te a m

e la t v e

e m p e r a tu r e is n o t re c o m he steam

n c r e a s in g si

fic a

em pe rat

ha

o i e r is n e e d e d

end ed.

e w

ho

he gau ge pressure do es n ot y i crea se the h ea t co

r a n s e r c h a r a c te r is t c s

o 6 0%

on

e m p e a tu r e s , in c e a s -

h e t e m p e r a tu r e m o r e th a n 2 0 ° - 3 0 ° a b o v e

n c e a s in g

pl ed

h i e m a in t a in in g a te m p e a tu r e o f 7 5 ° . s iz e s te a m

ere are o he r op eratng co nd

s a tu r a t o n

d i y . T h e c o m p a n y w a n ts to b o o s t h e d i y in a la b o r a to r y f o m

n le s s ha t eq

d ific a t o n T a b e .

o f a ir a t 7 5 °F a n d 3 5 %

g h e r e m p e r a tu r e s m a y b e n e c e s s a r y

f h e r e a re e x c e s s iv e p p e a n d e q u p m e n

f

en t

e s eam .

r

ea

e h eat

e n e r g y r e q u i e d t o s u p e r h e a t s te a m

can be

p lo t e d f o m

om og aph

sh

ster H u mi di c a ti o Initial Condition

ea t

st

s te a m

n)

n te m p e r a -

s te a m

s te a m

y in a ty p c a l c o

Example —  A

o n a ir c o n

a lc u a t i

hen

al y steam .

en s f r

o is t a ir s t e a m

a t s a tu r a t

s,

e n h ig h

n th e h e a t e x c h a n g e r o r

n f o r tu n a te ly , h e s te a m

s/

 - 4 9 . 9 8

T h e in je c t o n o f s te a m

nto a

er ed

( la t e n t

s te a m ” u s

h e p o s s ib le lo s s

d i y is a c o m

) s te a m

cati

u s u a l y m o r e th a n a d e q u a t e f o r m o s t a p p c a -

hr

o fla s h in g

a n s fe r o c c u s w

r o b e m s in s te r i z e r s a n d a u

a te r v a p o r

na

o s t e ffic ie n t h e a t

n

100 CFM

hu

.

e fe r e n c e

hu

g ap pl cat on

qu al y an d el eati g ap

e steam

b s /h r

pri ary ob ec-

su pe he at

prov e steam

a n g in g f o m

a d d e d ( ∆ V ) a r e 0 .1 1 9 b s - 0 . 0 2 1 b s o r 0 . 9 8

 =

s t s te a m

“ c a r r y o v e r ” . n s te a m

o t h e c h a r t, “ W a te r

per 10 0 f . Th e po un ds o f

Steam Humidification in General Applications —  ca

he

n g o u s id e

d i y ; o 8 0 °F a n

d i y c o n t a in s 0 1 1 9 lb s o f

h 7 50

g a

hu

a te r v a p o r p e r 1 0 0 f

e n d e d to a l o w

o f h e a te d c o n d e n s a te w a te r d u e

o in c r e a s e h u

of ncom

e fe r r n g

0 °F a ir a t 5 0 % um

Steam Super Heating —  T h e

g e e n h o u s e n e e d s to in c r e a s e

di y of 850

h

s a f e ty fa c t o r = 1 8 2 7 lb s h r

p r o c e s s . T h e m a jo r i y o f h e

n lb s / h r

n C FM

Example  —  A

n

x 2 .0 3 lb s /h r = 1 5 .2 2 5

2 5 lb s h r x 2 0

v e in

n)

Constant Air Tempe rature —  S

h r x 1 .2 S F - 1 0 0 .7 k W

rom

15

÷ 1 00 C FM

qu al y ( 00

flo w

e m p e a tu r e a p p

A 20 %

o r v a r ia b e te m p e a -

st re con en t s/ ∆ V  = I n c r e a s e in ased on a te r v a p o r c o n e n t o f a ir a t al co n an d at fi al co

1 k

91 2 B u/l

Q  =

eam

al co

h e n te rs e c t o f 6 0 %

2 . 3 lb s h r /1 0 0 C F M

s to  x 6 0 m

e i

o

u r e is c o n d e n s e d

 =

o lb s /h r

b s /g a l x 6 0

po und s of

s c a n b e c a c u a te d

h

°

h e re :

s/h r)

C p  =

cati

a ir a t 4 0 °F a n d 5 0 %

eat equ

h

100 CFM

5%

e t a b e , re a d

750 C FM

∆ V )(

-

h e re :

Q  =

a l y s iz e d b a s e - 5 p s ig

Fro m

a t 7 5 °F - 3 5 %

o r m u la :

su pp

a te r

) (F ) (∆ T ) (

s/ r at

e r h o u r re q u i e d

re app

 =

e d c a n b e c a lc u a te d

(

t n

erat re

a te r

s te a m

o r m u la :

C p)

en t s us

er ou

eed

s ta n t a ir e m

s.

n th e la r g e b o i e r

h 5 0 °F fe e d

Th e he at en ergy requ

n

e r.

a l s te a m

e q u i e m e n s c a n b e s e p a r a te d

h 50

o n d e n s a te is re tu r n e d t

er m xed

cati

h a t s iz e b o e r

o r e p la c e t h e c e n

ng shu t do

ap

of

nu ou

ed

d ific a t o n

o v a r ia b e a n d c

Variable Air Temperatures —  T h e

calcom pan y uses a shel

ub e heat exchang er o h eat10 gp m

a te r f o m

du

om

ers can be us ed as a

s u p p e m e n a l o r a l e r n a te s te a m

and

s av aiab

o i e r s o r w a s te h e a t

um

en

he S eam

u p e rh e a t

n in t h is s e c

Relative Humidity Des ired   40 0.345 — 0.368 — 0.405 —

45 0.690 0.345 0.728 0.368 0.810 0.405

50

55

60

65

70

1.03 0.69 1.10 0.73 1.22 0.81

1.38 1.03 1.46 1.10 1.62 1.22

1.72 1.38 1.83 1.46 2.03 1.62

2.07 1.72 2.20 1.83 2.43 2.03

2.42 2.07 2.57 2.20 2.84 2.43

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

Note — Lbs-vapor/hr/100 CFM required to secure desired relative humidity with no change in air temperature.

I-23 

Technical

Technical Information  Steam Superheating

Calculating kW Requirements for Superheating Steam

kW/hr = (lbs/hr) (W 2 -W 1) x 1.2 SF 1000 W/kW

The nomograph shown below can be used to determine the kilowatts required to superheat saturated steam to higher temperatures.

kW/hr = (560 lbs/hr) (82-39) x 1.2 SF 1000 W/kW

Example —  Heat 560 lbs/hr of 90% qual-

ity steam at 110 psig to 440°F at the same pressure. On line P, plot the gauge pressure (psig). Read the saturated steam temperature at operating pressure. Subtract from desired final temperature to determine degrees of superheat ( T ). ( T ) = 440°F - 344°F = 96°F Draw a straight line from P through line Q and read the intersect at line W(W 1) . Next, draw a straight line from same point on line P through S (°F of superheat) and read the intersect on line W(W 1) . Determine kW using W 1 and W 2 in the following formula.

Steam Superheat Nomograph

. . . .

Draw a line between P and Q, read W1 D ra w a l i ne b e t w e e n P a n d S , re a d W 2 S u b t ra c t W 1 f ro m W 2 Multiply difference in . by pounds of stea m per hour to obtain kW required.

Note  — A b ov e e x a m pl e s ho w s w a tt s re q ui re d t o ra i s e to 9 % q ua l it y s te a m a t 1 p s ig to °F. Degrees of superheat equal desired operating temperature minus s aturated stea m tempe rature on line T.  Ad d 2 % sa fe ty fa ct or fo r unk no wn los se s.

I- 2

kW/hr = 28.896 Determining Sheath and Chamber Temperatures for Superheated Steam — Since superheated steam is essentially a gas, the last step in the above procedure is to determine maximum sheath and chamber temperatures of the circulation heater using Chart 236 and Graph G-237 for air and gas heating. In the above example, assume Series 6 heater with a standard 23 W/in 2 rating. From the charts: Sheath Temperature = 1440°F Chamber Temperature = 940°F Select a Series 6 heater capable of the above operating conditions from the product pages in the Circulation Heater Section.

Technical

Technical Information Properties of Steam Sa turated Steam Th e t ermo dy amic pr perties o f sat rated steam are s n in t e tab e to t e ri t. atu rated steam is pu re steam in direc t tac t w ith t e i id ater r m ic h it as en erated an d at t e same temperatu re an d pressu re as th e w ater. F r e ample, satu rated steam at 5 0 psig as a temperatu re f 2 F. team press re is c mm ly ex pressed as ds per sq are i ab s te ith refere e to a perfect va m. sig is p ds per s are i h a e it refere e to atmo sp eric pressu re f 14 .7 psi psia = psig + 14 .7 psi (1 atm sp ere). psia  o r psig . sia is p

T e eat te t f liq id is t e eat en erg y i t /lb re ired to eat t e i id to t e di ti n in dicated starti g ith ater at 2°F. aten t eat is t e eat en er y in B tu /l a s r ed en a p d f i i g ater is verted to a p d o f steam at th e same temperat re. T e same amo t o f h eat is re eased w en t e steam co den ses a k t ater at th e same temperatu re. L aten t h eat varies ith temperatu re.

Boiler Feed W ater Temperature Th e temperat re f b iler feed w ater direc tly affe ts t e steam ou tp t f a i er. T e fo in ta e can e u sed to determin e t e kil att ratin f a b i er en t e steam l ad, g aug e pressure an d b iler feed ater temperat re are k . Example  —  A pr ess re

ires 4 0 s o steam per r at 7 5 psig . T e availab e feed ater temperat re is F. Fro m th e art, read t e kW/lb re ired fo r 5 °F ater a d a a e press re o f 7 5 psi . M tip y t e fa t r y t e p ds f steam: . 17 x 4 0 s 15 .8 kW.

Sat urated Steam — Gauge Press. ps ig

°F

0 1 2 3 4 5 6 7 8 9 10 15 20 25 30 35 40 45 50 55 60 65

21 2 21 6 21 9 22 2 22 4 22 7 23 0 23 2 23 5 23 7 24 0 25 0 25 9 26 7 27 4 28 1 28 7 29 2 29 8 30 3 30 7 31 2

T hermodynamic Properties nearest even digit)

Btu/lb Liquid Latent  Heat  Heat 

18 0 18 3 18 7 19 0 19 3 19 5 19 8 20 1 20 3 20 6 20 8 21 8 22 7 23 6 24 3 25 0 25 6 26 2 26 7 27 2 27 7 28 2

97 0 96 8 96 5 96 4 96 2 96 1 95 9 95 7 95 6 95 4 95 2 94 5 94 0 93 4 92 9 92 4 92 0 91 5 91 2 90 8 90 5 90 1

Steam Total

Btu/lb Sat. Gauge  V a po r Press. Temp. Liquid Latent  ft  /lb) (psig) (°F) Heat  Heat 

Steam Total

Sat.  Va po r ft  /lb)

1150 1151 1152 1154 1155 1156 1157 1158 1159 1160 1160 1163 1167 1170 1172 1174 1176 1177 1179 1180 1182 1183

27.0 25.0 24.0 22.5 21.0 20.0 19.5 18.5 18.0 17.0 16.5 14.0 12.0 10.5 9.5 8.5 8.0 7.0 6.7 6.2 5.8 5.5

1184 1185 1186 1187 1188 1189 1190 1192 1193 1193 1194 1195 1196 1197 1197 1198 1199 1199 1200 1201 1201 1204

5.2 4.9 4.7 4.4 4.2 4.0 3.9 3.6 3.3 3.2 3.1 2.9 2.7 2.6 2.5 2.3 2.2 2.1 2.0 1.8 1.75 1.48

70 75 80 85 90 95 10 0 110 12 0 12 5 13 0 14 0 15 0 16 0 17 0 18 0 19 0 20 0 22 0 24 0 25 0 30 0

31 6 32 0 32 4 32 8 33 1 33 5 33 8 34 4 35 0 35 3 35 6 36 1 36 6 37 1 37 5 38 0 38 4 38 8 39 5 40 3 40 6 42 2

28 6 29 0 29 4 29 8 30 2 30 6 30 9 31 6 32 2 32 5 32 8 33 4 33 9 34 4 34 8 35 3 35 8 36 2 37 0 37 8 38 1 39 9

89 8 89 5 89 2 88 9 88 6 88 3 88 1 87 6 87 1 86 8 86 6 86 1 85 7 85 3 84 9 84 5 84 1 83 7 83 0 82 3 82 0 80 5

Boiler Feed W ater Temperature V s. k W Required per Pound of Steam Feed  W a te r (°F)

40 50 60 70 80 90 10 0 110 12 0 13 0 14 0 15 0 16 0 17 0 18 0 19 0 20 0

Stea m Gauge Pressure (psig)

.3347 .3318 .3288 .3259 .3229 .3200 .3171 .3142 .3112 .3083 .3054 .3025 .2995 .2966 .2937 .2907 .2878

.3355 .3326 .3296 .3267 .3238 .3208 .3179 .3150 .3210 .3091 .3062 .3032 .3003 .2974 .2945 .2915 .2886

.3375 .3345 .3316 .3287 .3278 .3238 .3199 .317 .314 .3111 .3082 .3052 .3029 .2994 .2964 .2935 .2906

.3388 .3359 .3329 .3300 .3271 .3242 .3212 .3183 .3154 .3124 .3095 .3066 .3036 .3001 .2978 .2948 .2919

.3406 .3376 .3347 .3318 .3288 .3259 .3229 .3200 .3171 .3142 .3113 .3083 .3054 .3025 .2995 .2966 .2937

.3422 .3392 .3363 .3334 .3305 .3275 .3246 .3217 .3187 .3160 .3129 .3099 .3070 .3041 .3011 .2982 .2953

.3431 .3401 .3372 .3343 .3313 .3284 .3255 .3225 .3196 .3167 .3137 .3108 .3079 .3050 .3020 .2981 .2962

.3447 .3417 .3388 .3359 .3329 .3300 .3271 .3242 .3212 .3183 .3154 .3124 .3095 .3066 .3036 .3007 .2978

.3458 .3429 .3400 .3370 .3341 .3312 .3283 .3253 .3224 .3195 .3165 .3136 .3107 .3077 .3048 .3019 .2989

.3464 .3435 .3407 .3376 .3347 .3318 .3288 .3259 .3230 .3200 .3171 .3142 .3113 .3083 .3054 .3025 .2995

.3470 .3441 .3411 .3382 .3353 .3324 .3294 .3265 .3236 .3206 .3177 .3148 .3118 .3089 .3060 .3030 .3001

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

I- 2

Technical

Technical Information 

Heating Solids - Platens, Dies &Molds  The calculation of heating requirements for heating solid materials (such as platens, dies and molds) is similar to other applications. The following is a typical application problem: Example —  A plastic forming process uses 20 lbs of plastic ( C p  = 0.45 Btu/lb/°F) per hour.

The plastic is pliable at 300°F and is formed by two steel platens, each 24 in. long x 12 in. wide x 3 in. thick and weighing 245 lbs. The platens must be preheated to 300°F in the closed position within 30 minutes. The top and bottom of the platens (press side) are insulated with 1/2" of rigid insulation.

Since the heat-up requirement is greater than that for operation, install 10 kW. Heater Se lection —  While most platen and

die heating applications are accomplished with cartridge heaters, strip or tubular heaters may also be used by inserting them into grooved slots in the metal. (See clamp-on heater applications.) When selecting cartridge heaters, it is essential that the following factors be considered to ensure reasonable heater life and sufficient heat. Se lect Watt Density —  The maximum permissible sheath watt densities for INCOLOY® sheath (CIR) cartridge heaters for a given metal temperature are shown on Graph G-235A. These curves plot the recommended watt densities for various hole clearances. Graph G-201 is useful for determining watt density for optimum life when selecting type CIR heaters.

In it ia l He a t U p To heat the steel platens (C p  = 0.12 Btu/lb/°F)

kW = Lbs x Cp  x ∆ T 3412 Btu/kW x t  kW = 245 lbs x 2 x 0.12 Btu/lb/°F x (300 -70°F) 3,412 Btu/kW x 0.5 hrs. kW = 7.93 Losses from exposed edges during heat-up: (See Graph G-125S, Curve “A”, for oxidized steel.) Edge area = 2 (2 ft) + 2 (1 ft) x 0.5 ft = 3 ft2

kW = 3 ft2 x 200 W/ft 2 /hr = 0.6 kW/hr 1000 W/kW Losses by conduction from top and bottom insulated surfaces of the platen —

Protect Cartridge Heate rs from External Contamination —  Contamination can occur when moisture, oil, etc. enters the sheath through the lead wires or terminal end. (The end opposite the lead wires is protected by a seal welded end disc.) Contamination frequently causes short life and dielectric failure. Special moisture resistant terminal constructions are available and hermetic seals can be supplied when severe contamination problems are present.

Determine Proper Fit —  When cartridge heaters are installed in a machined or drilled hole, the hole should be sized to the nominal diameter of the heater. For best fit, holes should be drilled slightly undersized and reamed to the nominal heater diameter. Actual diameters of standard cartridge heaters are 0.003 to 0.005" smaller than nominal. This allows for easy installation when cold. Sheath expansion upon heating provides an interference fit and maximum heat transfer.

. Provide Mechanical Protection for the Lead W ires —  Most high temperature

lead wire electrical insulations have little resistance to mechanical abrasion. Special constructions using sleeving or conduit for mechanical protection are available.

raph 2 1 — g g ested Wa tt e si ty i mi ts f o r O pti m m i fe  

   n    I    W    y    t    i    s    n    e    D    t    t    a    W     d    e    t    s    e    g    g    u    S

C  I   R    A l   l  o   y  S   h  e  a  t   h   C 

0

kW = Area ft 2 x x ∆ T 3412 Btu/kW x d

raph G 2 A — ax im m Watt D e sity Vs. s its sin g Type CIR Cartrid e Heaters 

Where: = 0.45 Btu/hr/in/Ft 2 /°F thermal conductivity of rigid insulation (Properties of Non-metallic Solids) d  = thickness of insulation (0.5 inch) kW =2(2 ft2) x 0.45 x (300 - 70°F) = 0.24 kW/hr 3412 Btu/kW x 0.5 in. Average losses 0.6 kW + 0.24 kW ÷ 2 = 0.42 kW/hr kW for start up = 7.93 + 0.42 x 1.2 SF = 10.0 kW (Assume losses from opening and closing the platens are negligible.) To heat plastic: O pe ra t in g R e q ui re m e n ts —

kW = 20 lbs x 0.45 Btu/lb/°F x (300 - 70°F) = 0.61 kW 3412 Btu/kW

200

S  t a i  n l e s  s  S  h  e a t h 

400 600 800 Platen Temperature (°F

1000

aten Temperatu re fo r VariGraph Based on Steel Platen Temperature Measured /2 from Hea ter

F  

F  

   n    I

F  

   W    y    t    i    s    n    e    D    t    t    a    W    e     l     b    a    w    o     l     l    A    m    u    m    i    n    i    M

F   

F  

F  

F 

Losses = 0.6 kW + 0.24 kW = 0.84 kW Total kW = 0.61 kW + 0.84 kW = 1.45 kW Required kW = 1.45 kW x 1.2 SF = 1.74 kW 001

I- 2

002

.003

.0 0 4 0 0 5 0 0 6 008 010 .020 030 Fit in Hole (Ma x. Hole I.D. Minus Min. He ater O.D. in Inches)

040

050 060

080

100

Technical

Technical Information

Heating Exchangers - Heating & Cooling G eneral Informat ion

U sing H ot W ater H eating M edia 

U sing C old W ater C ooling M edia 

In addition to direct heating with electric heating elements, Chromalox can provide heat exchangers for use with circulating hot or cold water systems or with steam as the heating media. The heat exchangers are designed to heat water solutions in plating baths and other corrosive applications and are available in Stainless Steel, Titanium or Teflon ®. Check the Corrosion Guide in this section for proper sheath material selection. The procedures and calculations for using these heat exchangers are shown below: The procedures are based on closed and insulated tanks (see note below).

The heating capacity requirements for using hot water as the heating media can be determined from the following formula:

In electroplating operations, considerable heat is added to the plating solution by the plating current. Frequently it is desirable to cool the plating bath without diluting or upsetting the chemical balance by introducing cold water directly into the solution. Heat exchangers provide the ideal solution to this problem. The cooling capacity requirements for using cold water as the cooling media for a plating bath can be determined from the following formula:

U sing Steam H eating M edia  The heating capacity requirements for using steam as the heating media can be determined from the following formula:

 the proper U factor for the particular type heat exchanger selected. n e  temperature of incoming hot water supply.

 the above equation and solve for area in square feet.

5. Ap pl

 gallons in tank to be heated.

the heat exchanger from the product pages that matches the requirements.

6. S elect

 the usable steam pressure in Table 1 and determine the Steam Pressure Factor.

3. Lo cat

the Steam Pressure Factor to the above equation and solve for area in square feet.

4. A pp

5 . S e e c t  the heat exchanger from the product

pages that matches the requirements.

S t ea m P r essu r e F a ct or ea m

The above equation gives the square feet of heat exchanger needed to complete the heat up operation in one hour. If more time is available, the coil surface area (ft 2) may be reduced by dividing the square feet from the above equation by the heat up time available. The correction factor can be used for time periods up to 4 hours maximum. — When heating open tanks, the heat loss from the water surface must be added to the heating requirements (see Graph G-114S). ot

1

C alculati on P rocedure  the watts of energy from the rectifier by multiplying the volts times amps. Convert watts to Btu by dividing by 3,412.

1 . D e te r

ne

n e  the proper U factor for the particular type heat exchanger selected.

2 . D e te r

 temperature of incoming cold water supply.

3 . D e te r

ne

4 . S u b t a c t  the

temperature of the cooling water from the desired temperature of the solution to be cooled. C A T I — If the difference in temperature is less than 15°F, contact your Local Chromalox Sales office for assistance in determining proper coil size.  the above equation and solve for area in square feet.

5. Ap pl

pages that matches the requirements. e

 22

Te o

Where: VR = Voltage of rectifier AR = Amperage or current of rectifier U = Factor for coil type U factor for Metal Coils — 90 U factor for Teflon ® Coils — 40 T 1 = Final temperature of solution to be cooled T 2 = Temperature of incoming cold water media Ft2 = Square feet of heat exchanger required to provide cool down in one hour

6 . S e e c t  the heat exchanger from the product

e s s u e A v a i a b e (p s i g )

Exchangers

 t

VR x AR x 3.412 Btu/W = ft 2 /hr U x (T 1 - T 2)

ne

4 . D e te r

ac

T a b le 1 —

gallons in tank to be heated.

ac

3 . D e te r

the temperature of the solution to be heated from the desired temperature. ub

ne

the initial temperature of the solution to be heated from the desired temperature.

C alculat ion P rocedure

.

C alculati on P rocedure

2. S ub

Where: V = Gallons of liquid to be heated T  = Desired temperature rise or change in temperature °F SPF = Steam pressure factor from Table 1 Ft2 = Square feet of heat exchanger required to provide heat up in one hour

ne

Where: V = Gallons of liquid to be heated T  = Desired temperature rise or change in temperature °F U = Factor for coil type U factor for Metal Coils — 90 U factor for Teflon® Coils — 40 T 1 = Temperature of incoming hot water media T 2 = Final temperature of solution to be heated Ft2 = Square feet of heat exchanger required to provide heat up in one hour

1. De er

V x T x SPF= ft2 /hr 1000

1 . D e te r

V x T x 8.33 = ft 2 /hr U x (T 1- T 2)

 2

 2 1

 1

 1

2 11

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

t  1   t  1  

Con t act ou rL ocalChrom al ox S al es of ce forrecom m e dat ion s forst eam pressu res

   3 0 p i  -2

Technical

Technical Information Radiant Infrared Heating - Theory & Principles Infrared Theory

Em

Infrared energy is radiant energy which passes through space in the form of electromagnetic waves (Figure 1). Like light, it can be reflected and focused. Infrared energy does not depend on air for transmission and is converted to heat upon absorption by the work piece. In fact, air and gases absorb very little infrared. As a result, infrared energy provides for efficient heat transfer without contact between the heat source and the work piece.

s s iv i y a n d a n

d e a l In f a r e d

fl c t iv i ty  Materials with poor emissivity frequently make good reflectors. Polished gold with an emissivity of 0.018 is an excellent infrared reflector that does not oxidize easily. Polished aluminum with an emissivity of 0.04 is an excellent second choice. However, once the surface of any metal starts to oxidize or collect dirt, its emissivity increases and its effectiveness as an infrared reflector decreases.

ou ce

The ability of a surface to emit radiation is defined by the term emissivity. The same term is used to define the ability of a surface to absorb radiation. An ideal infrared source would radiate or absorb 100% of all radiant energy. This ideal is referred to as a “perfect” black body with an emissivity of unity or 1.0. The spectral distribution of an ideal infrared emitter is below.

Spectral D istr ibution of a Blackbody at Various Temperatures

Figure 1

! P e a k W a v e le n g t 14 00°F en

!

s p la c e m e n t C u r v e

12 00°F

Infrared heating is frequently missapplied and capacity requirements underestimated due to a lack of understanding of the basic principles of radiant heat transfer. When infrared energy from a source falls upon an object or work piece, not all the energy is absorbed. Some of the infrared energy may be reflected or transmitted. Energy that is reflected or transmitted does not directly heat the work piece and may be lost completely from the process (Figure 2).

Figure 2

10 00 °

80 0° 40 0° 1

nf ared Em

ers

o u c e T e m p e a tu r e s

The amount of radiant energy emitted from a heat source is proportional to the surface temperature and the emissivity of the material. This is described by the Stefan-Boltzmann Law which states that radiant output of an ideal black body is proportional to the fourth power of its absolute temperature. The higher the temperature, the greater the output and more efficient the source.

-28

3

4

5

a v e le n g t h (

6

7

8

9

10

c ro n s )

— As the temperature increases, the peak output of the source shifts to the left of the electromagnetic spectrum with a greater percentage of the output in the near infrared range. This is referred to as the Wien Displacement Curve and is an important factor in equipment selection. ot

In practice, most materials and surfaces are “gray bodies” having an emissivity or absorption factor of less than 1.0. For practical purposes, it can be assumed that a poor emitter is usually a poor absorber. For example, polished aluminum has an emissivity of 0.04 and is a very poor emitter. It is highly reflective and is difficult to heat with infrared energy. If the aluminum surface is painted with an enamel, emissivity increases to 0.85 - 0.91 and is easily heated with infrared energy. Table 1 lists the emissivity of some common materials and surfaces. Em

Another important factor to consider in evaluating infrared applications is t hat the amount of energy that is absorbed, reflected or transmitted varies with the wave length of the infrared energy and with different materials and surfaces. These and other important variables have a significant impact on heat energy requirements and performance.

2

s s iv i y —

 Once the infrared energy is bso pt on converted into heat at the surface, the heat travels into the work by conduction. Materials such as metals have high thermal conductivity and will quickly distribute the heat uniformly throughout. Conversely, plastics, wood and other materials have low thermal conductivity and may develop high surface temperatures long before internal temperatures increase appreciably. This can be an advantage when using infrared heating for drying paint, curing coatings or evaporating solvents on non-metal substrates.

Table 1 — Approximate Emissivities M e

R o

 mi m  0  0 4 0 0 5      003 00602   o pp   0  0 1 8  0  0 2   o ld   00180035 t  l 1 2 0  075 t i      11 057  d  0  0 5 7  0 0 7 2 8 Nickel 0450087 il   0020035 Tin 0040065 in c 0  0 4 5  0 0 5   I   22 8 Miscellaneous Materials b t   Brick    , m t Oak, Planed  p     ti      i ,   d   Q  tz , R , F  d    f to   t i    b b    W t   Paints, Lacquers, Varnishes Black/White Lacquer  m  l   c    il  i t   c     m i m P i t  

O x

 11  0  1 060 057 080095 080095 063 037048  11 2 093096 075093 . 27

.

. 24

.

0937 0895

086095  2 0932  065091 086095 0950963 08095 085091  2  2  0 

 Most materials, with the exs s io n ception of glass and some plastics, are opaque to infrared and the energy is either absorbed or reflected. Transmission losses can usually be ignored. A few materials, such as glass, clear plastic films and open fabrics, may transmit significant portions of the incident radiation and should be carefully evaluated. T ra n s m

on ol ng nf ared En ergy Lo sses  Only the energy absorbed is usable in heating the work product. In an unenclosed application, losses from reflection and re-radiation can be excessive. Enclosing the work product in an oven or a tunnel with high reflective surfaces will cause the reflected and re-radiated energy to be reflected back to the work product, eventually converting most of the original infrared energy to useful heat on the work product.

Technical

Technical Information

Radiant Infrared Heating - Source Evaluations Evaluating Infrared Sources  Commonly available infrared sources include heat lamps, quartz lamps, quartz tubes, metal sheath elements, ceramic elements and ceramic, glass or metal panels. Each of these sources has unique physical characteristics, operating temperature ranges and peak energy wavelengths. (See characteristics chart below.) rc e Te mpe ra t re & Wa ve e n th i s tri b u ti o n  All heat sources radiate infrared energy over a wide spectrum of wavelengths. As the temperature increases for any given source: 1. The total infrared energy output increases with more energy being radiated at all wavelengths. 2. A higher percentage of the infrared energy is concentrated in the peak wavelengths. . The energy output peak shifts toward the shorter (near infrared) wavelengths.

For process heating, it is recommended that the infrared source have a peak output wavelength that best matches the selective absorption band of the material being heated. When the major absorption wavelengths of the material being heated are known, the chart below provides guidance in selecting the most efficient heat source. The relative percentage of radiant energy emitted by specific source and falling in a particular wavelength range can be determined from the chart.

2.

. T e i f e re n c e  between these two values (22%) is the percentage of radiant energy emitted by the element within selected wavelengths limits. . To ta i  the maximum percentage of the energy emitted by a given element in the desired wavelength band, multiply the percentage in 3 above by the conversion efficiency for the selected element (comparison chart 56% x 22% = 12.2%).

ample  — Plastic materials are known to have high infrared absorption rates in wavelengths between 3 and 4 microns. Select a source which provides the most effective output to heat plastics in the 3 and 4 micron range. 1.

In this example, a high temperature source (quartz lamp 4000°F) with a peak in the 1.16 micron range, while more energy conversion efficient, would not be as effective as a lower temperature metal sheath or panel heaters with a peak in the 2.8 to 3.6 micron range. Quartz tubes (1600°F) would provide similar peak wavelengths.

te r tt m f C a rt at 3 and 4 microns, read up to corresponding points on selected element curve (use 1400°F metal sheath in this example). 10

The peak energy wavelength can be determined using Wien’s Displacement Law.

   t    e    e    v    a     W

Peak Energy = 5269 microns/°R (Microns) Source Temp. (°F) + 460 Source = 5269 microns/°R = 2.83 microns 1400°F 1400°F + 460

e rc e n ta g e I n c re me n t o f R a di a t E n e r y a l i n g e l w a n y Wa ve le n g t for a B lack dy at Temperature T 

A

C 

   e    y    r    e

Source = 5269 microns/°R = 5.49 microns 500°F 500°F + 460

r m T e se P i n t s move left to read the corresponding percentages (29% and 51%).

   t    a     i     d 20    a

A s rpti o n y W rk r d t a te ri a s i n r ess Appli atio s —  While most materials absorb long (far) infrared wavelengths uniformly, many materials selectively absorb short (near) infrared energy in bands. In process heating applications this selective absorption could be very critical to uniform and effective heating.

AB CD -

10

0 . 4 0 . 7 2 1. 2 1. 6 2. 0 2. 4 2. 8 3 . 2 3 . 6

40 1 1 1

°F °F °F °F

rc e Te mpe ra t rc e Te mpe ra t rce Temperat rc e Te mpe ra t

4.0 4.4 4.8 5.2 5.6 6.0 6.4

re re re re  

6.8

7.2 

Wa ve le n g th - M i c ro n s   39 00

215 0

14 0 0 10 0 0 740 Temperature (T) deg rees F =

55 0 adiati n

4 10 eaks 

31

Characteristics of Commercially Used Infrared Heat Source  Tu n g sten F i amen t I n f ra re d rc e   S o u rc e Te m p e ra tu re ° F B rig h tn e s s S LFO&Rn J rLRn T y p e o f S o u rc e N W Y OnJ K ( P LFrRnV) M a xim um P o w e r D e ns ity   W a tts p e r L ine a r In c h &RnY rVLRn  I FLnFy Infra re d E ne rg y  R e s p on s e T im e H e a t C o ol C o lo r S e n s itiv ity KrP O KRFN VLVnF M e c h a n ic a l R u g g e d n e s s C h ro m a lo x M o d e l

N i kel Ch ro me R e sistan c e Wire  

G lass B u l T3 Qu artz L amp 30 00 - 40 00 °F 30 00 - 40 00 °F In te n s e w h ite In te n s e W h it e G -3 0 Lamp P o in t

/ 8 D ia . T u b e L in e

1 N I N /A

3 .9 N

I

S e c on ds H ig h P oor P oor

S e c on ds H ig h E x c e lle n t F a ir QR

Qu artz Tu b e U p to 1 6 0 0 ° F B rig h t R e d t o D ull O ra ng e 8 or 2 Tube L in e 1 .3 - 1 .7 5 N 4 0 -

I

1 - 2 M in ute s M e d iu m E x c e lle n t G ood QRT

Wide Area P an els 

etal S h eat Cerami U p to 1 5 0 0 ° F U p to 1 6 0 0 ° F D ull to B rig ht  rN R D OO Red Red / 8 o r / 2 T u b e V a rio u s S h a p e s L in e S m a ll A re a 3 3 .6 6 N I  S R 3 .6 N I 5 N /A 5 5 -

Ceramic Co ated 20 0 -16 00 °F rN R C h e rry R e d F la t P a n e ls W id e A re a 5 3 .6 N I N /A 5 -

Qu artz F a e   U p to 1 7 0 0 ° F rN R & K rr  Red F la t P a n e ls W id e A re a   5 5 .7 6 N I   N /A  5 -

2 - 4 M in ute s M e d iu m E x c e lle n t E x c e lle n t RAD, URAD

5 - 8 M in ute s L o w to M e d iu m G ood G ood C P L , C P L I, C P H

6 - 0 M in ute s L o w to M e d iu m G ood F a ir C PHI

5 - 7 M in ute s M e d iu m G ood G ood RCH

I-29

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

Technical

Technical Information

Radiant Infrared Heating - Process Applications p p c a t o n P a r a m e te r

Eleme nt Res ponse Time — S ome applica-

Typical industrial applications of radiant heating include curing  or baking  ( powders, paints, epoxies, adhesives, etc.), drying  (w ater, solvents, ink s, adhesives, etc.) and  product heating  (preheating, s oldering, s hrink tting, forming, m olding, g elling, softe ning, and incubating) . The following are g eneral guidelines that can be used in evaluating and resolving most radiant heating problems. Unfortunately, the process is so versatile and its applications so v aried that it is not feasible to list s olutions to every problem. To determine heat energy requirements and select the bes t Chrom alox infrared equipment for your application, it is suggested the problem be defi ned using a check list s imilar to below. S everal of the k ey factors on the list are discus sed on this and following pag es:

1.  Product to be heated 2.  Phys ical dimensions and weight/piece 3.  Surface coating or s olvents, if any 4.  Infrared abs orption characteristics 5.  Production rate (lbs /hr, pieces/hr, etc.) 6.  Work handling m ethod during heating (continuous, batch or other)

7. Element respons e time ( if critical) 8.  Power level requirements in k W /ft   based on Time/Temperature relationship (if n ow n ) 9.  Starting w ork temperature 10. Final work tem perature 11. Ventilation ( if present or required) 12. Av ailable power supply 13. Space limitations

Infrare d Abs orption Characteristics —  A s previously discus sed, m any materials, particularly plastics, s electively abs orb infrared radiation. The following chart provides data on som e comm on plastic materials and the recommended source temperatures for thermoforming applications. Plastic 

 Abso rption  Ideal Source  Band(s) (microns) Temperature (°F)

LPE PE PS

     

PVC

                 

PMM  P C e llu lo s e   c e ta te

I-30 

   

                                     

tions, s uch as continuous w eb heating of paper or plastic fi lm, require quick shutdown of heaters in case of w ork stoppage. In these applications, res idual radiation from the infrared heaters and ass ociated equipment m ust be cons idered. Res idual radiation from t he element is a function of the operating tem perature and mas s. Quartz lamps and tubes have relatively low mas s a nd the infrared radiation from the resistance wire drops signifi cantly  w ithin s ec onds afte r s hu tdow n. Ho w ev er, the surrounding quartz envelope acts as a secondary source of radiation and continues to radiate cons iderable energy. M etal sheathed elements have m ore mass and s lightly slower response time. W ide area panels have the mos t mass and the slowes t response time for both heat up and cool down. The following chart show s the average cool down rate of  v ario us s ou rces af te r s hutd ow n. A ctua l co ol down of the s ource and work product will vary  w ith equipm en t d es ig n, produ ct te m perat ure , ambient tem perature and ventilation.

Sou

e T e p e ra t e V .

1600 

Source Temperature  After Shutdown 

1500 

   )    F 1400     °    ( 1300    e   r   u 1200    t   a   r   e   p 1100    m   e 1000     T   e   c 900    a    f   r   u 800     S   r   o 700     h   t   a   e 600     h    S 500 

 A. Q uartz Lamp 3/8” Dia. B. Q uartz Tube 1/2” Dia. C. Metal Sheath D. Wide Area Panel E. Ceramic Heater 

C 

 A 

Surface  Temp Time  Subs trate   (°F) W/In2   (sec)

 la s s B o t t le s   d h e s iv e s Heating C h r LQN LQ   B S F o m i g

D 

 

Pape

 

Deriving Time-Temperature Information from Empirical Tes ting — If specifi c information is not readily av ailable for a particular work product, a simple but effective tes t will usually provide enough preliminary data to proceed  w ith a d es ig n. Plac e o ne or m ore rad iant h ea ters in a pos ition w ith the radiation directed at a work product sample. The distance between the face of the heater and the sample should approximate the expected s pacing in the fi nal application. Position the sam ple so that it is totally within the radiated area. Energize the heater(s ) and record the time necessary to reach desired temperature. Calculate the W/ in falling on the w ork piece using the exposed area of the work product and the maximum k W / f t   at the face of the heater as listed in the product catalog pag e. If the data is not av ailable and a sample test can not be performed, the following table provides a few sugg ested  w at t d en s itie s as g uid ance W/In 2 on Work   Application  QW Q Me tal  Off  Themofomig F u s i  g o  E m b o s s i g ( S sWF s N 6 r eeQ r y L Q

Heat Up 

Hold    

   

C o  t a c t  o u  L o c a l C h o m a l o  S a l e s o f  e IR r I rWer LQIR rP W Q r a ss sWQ e i d e t e m i  i g t im e  te m p e  a t u e e q u i e  mets fo a paticula applicatio

E 

400 

Drying  &  He ating

B 

300  0

30

60 90 120 150 180 Elapsed Time (Sec.)

Time-Te mpe rature Re lations hip —  A crit ica l step in the ev aluation of a radiant heating application is to determine the time necessary to develop work piece temperature and the elapsed time neede d to hold temperature in order to obtain the desired results (curing or drying). The following chart shows time/ temp erature relationships for sev eral typical infrared applications and m aterials. Surface Time  Curing Subs trate   Temp (°F) W/In 2  (min) Ny QW   S te e l  E p o   P a i t     c  lic P a i t  Pode C oat 

S te e l S te e l S te e l

 

Power Level or Radiation Intensity — In most process applications, more than one radiant heater is needed to produce the des ired results. W hen heaters are m ounted together as close as poss ible, the net radiant output of the array is defi ned as the maximum power level or radiation intensity. The catalog pag es for radiant heaters indicate the maximum W /ft  at the face of each heater. Typical ranges for radiation intensity (power level) are as follows: Radiant Intens ity  or Power Level  Lo Medium igh

Heate r Output  (kW/Ft 2  )     Ov e

Technical

Technical Information

Radiant Infrared Heating - Process Applications e te rmi n i n g kW e q i re d  It is difficult to develop s imple calculations for radiant heating applications bec ause of the many variables and proc es s unknowns. Des ign data gained from previous ins tallations or  from empirical tes ts is frequently the mos t reliable way of determining ins talled kW requirements. Total energy requirements can be es timated with c onventional heat los s e quations . The res ults o f conventional equations will provide a check against data obtained from nomog raphs or empirical tes ting. As a minimum, c onventional equations s hould include the following. 1. Cal late the S en sib le Heat  required to bring work to final temperature. Bas e calculations on specific heat and pounds o f material per hour. 2.

etermin e L aten t Heat f Vap rizatio ( e n a ppl i a b e ).  Latent heat of vaporization is normally s mall for solvents in paints and is frequently ignored. Howe ver, when water is being evaporated, the kilowatt hours required may be quite s ignificant.

. Ven tilatio n Air ( en appli ab le).  The rise in air temperature for work tempe ratures , 350°F or les s , c an usually be es timated as 50% of final work temperature ris e. For higher work temperatures , ass ume air and work temperature are the s ame. . C

vey r elt r C ain Heat e q i re me n ts.  As s ume temperature ris e of conveyor to be the same as work temperature ris e.

. Wall, lo r an d Ceilin g sses fo r c l o se d ve n s.  For uninsulated metal s urfaces , refer to Graph G-125S. For ins ulated walls , refer to Graph G-126S. .

ve n E d sse s.  For enclosed ovens, this will depend on s hape of e nd area and whether or not air se als are us ed. If s ilhouette s hrouds are us ed, a safety factor of 10 is acceptable.

in 1-6   . T e S m f T e L o sse s calculated above will be the minimum total heat energy requirement based on conventional heat los s equations.

I n f ra re d He ati n g a ti o s —  Infrared energy requirements c an als o be es timated by using equations and nomog raphs developed s pecifi-  cally for infrared applications .

For drying, us e the following equation.

r d c t He ati n g  For product heating, the  following equation can be used 

Where: QWP = Btu required by work product to raise the temperature from initial to vaporization temperature s  = Btu required by s olvent to rais e the temperature from initial to vaporization temperature QLH = Btu required for the latent heat of the vaporization of the s olvent Efficiency (RE) = Combined efficiency of the s ource and refl ector VF = View Factor for enclos ed ovens , use a  factor of 0.9. For other applications, refer to the view factor table.  = Absorption (emiss ivity) factor of the work  product 

kW =

Lbs /hr x C p x T °F 3412 Btu/kW x Efficiency (RE) x VF x 

Where: Lbs/hr = Pounds of work product per hour C p  = Specific heat in Btu/lb/°F T  = Temperature rise in °F Efficiency (RE) = Combined efficiency of the s ource and refl ector VF = View Factor is the ratio of the infrared energy intercepted by the work  product to the total energy radiated by the source. For enclosed ovens, use a  factor of 0.9. For other applications, refer to the view factor table.  = Absorption (emiss ivity) factor of the work  product  ryi n g & ve n t E va p ra ti n  Remo ving s olvent or water from a product requires rais-  ing the product temperature to the vaporiza-  tion temperature of the s olvent and adding s ufficient heat to evapo rate it. To c alculate heat requirements for s olvent evaporation, the fol-  lowing information mus t be known. 1. 2. . . . . . . . 10 .

Pounds of s olvent to be evaporated per hour  Pounds of work product per hour  Initial temperature of product and s olvent  Spec ific heat of product  Spec ific heat of s olvent  Vaporization tempe rature of s olvent (ie: water = 212°F) Heat of vaporization of so lvent  Source/refl ector efficiency  View factor  Absorption factor (emiss ivity)

WA  — Ha z ard f i re .  Flammable s olvents in the atmos phere c ons titute a fire hazard. When fl ammable volatiles are release d in co ntinuous proc es s ovens, the National Fire Prevention Ass oc iation recomme nds not less than 10,000 ft 3  of air be removed from the oven per gallon of s olvent evaporated. Refer-  enc e NFPA Bulletin 86 "Ovens and Furnace s ", available from NFPA, P.O. Box 9101, Q uincy MA 02269.

kW

QWP + QS + QLH 3412 Btu/kW x Efficiency (RE) x VF x 

C tr ls  Mos t control s ys tems for infrared  proc es s heating can be divided into two categories , open loop or manual s ys tems and closed loop, fully automatic systems. pe n L ps r a n u a l yste ms  The s im-   plest and mos t cos t effective co ntrol s ys tem is an input co ntrollers (percentage timer) s uch as the Chromalox VCF Controller operating a magnetic contactor. The timer cycles the radiant heaters on and off for s hort periods of time (typically 15 - 30 s ec onds ). This c ontrol s ys tem works bes t with metal sheath heaters, which have s ufficient thermal mass to provide uniform radiation. It can be used with quartz tube or quartz lamp heaters by us ing s pec ial circuitry to s witch from full to half voltage rather than full on and full off. Closed p or A t matic S ystems —  Since infrared energy heats the work product by direct radiation, closed loop co ntrol sys tems that depend on s ens ing and maintaining air temperature are relatively ineffective (e xce pt in totally enclosed ovens). In critical applications where temperature tolerance s must be clos ely held, non-c ontact temperature s ens ors operat-  ing SCR control panels are rec ommended. Non-contact temperature s ensors can be  pos itioned to meas ure only the work product temperature. Properly pos itioned, non-contact temperature sens ors and SCR control panels can provide very accurate radiation and prod-  uct tempe rature co ntrol.

-3 1

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Technical

Technical Information

Radiant Infrared Heating - Process Applications sti ma ti n g T o t al i l

Nom ograph for Product Hea ting —  For product heating, the nomograph at the right can be used. The nomog raph does not tak e into account heat energy requirements for air ventilation. To estim ate the k W for total product heating:

250

300

a tts f o r P r o d u c t H ea ti n

350 400

100 90 80 70

Temperature R ise ° F

60

50

40

Overall Ef ciency 

. Determine  pounds of m aterial per hour to be heated (A . Read across  to the specifi c heat of the material (B)

C

D

Read up  to desired temperature rise in °F (C)

Rea d across  to overall effi ciency ( D). Overall effi ciency = Product Abs orption Factor x View Factor x Source Effi ciency. Determine Product A bsorption Factor (s urface emissivity) of the w ork product (ie:  = .8 5 for enamel sheet metal). Determine View Factor (use 0 .9 as a view factor for well designed or enclosed ovens ). Determine Source effi ciency. Typical S ource/Re ector effi ciencies are: Q ua rt z L a m ps 0 to Q ua rt z Tu be s 0 to M e ta l S h e at h 5 to

E 10 Specifi c Heat of Material

1000

.0 .8

B  A 

.4 .3 .2

2000 3000

.0.05

.1

5000 8000 10000

30

50

70 90 110 130 150 Kilowa tts of Infrared Re quired

   r    u    o    H    r    e    P     l    a    i    r    e    t    a    M     f    o    s     d    n    u    o    P

. R e a d d ow n  to K ilowatts required (E) Nom ograph for Drying —  The nomog raph to the right can be used to es timate Kilowatts required to evaporate water from the surfaces of work product. Graph is based on a n initial starting product temperature of 7 F. It does not tak e into account heat energy requirements for air circulation or v entilation.

sti ma ti n g I n ra red K i l 60

. Read across  to Work Product Absorption Factor (C). This v alue is based on the emiss ivity of the work product surface (ie:  = .8 5 for enameled sheet metal) and the view factor of the oven or space. Use .9 as a view factor for well designed or enclosed ovens . R e a d d ow n  to K ilowatts required (D) I- 3

50

40%

100 90 80 70

60

50%

40

Source/Re ector Efficiency   W ork P rodu ct Ab so rpti on F a cto r (Emissivity x View Factor)

. Determine pounds  of water (s olvent) per hour to be evaporated (A . R e a d u p to S ource/Refl ector effi ciency (B). Depending on the confi guration and cleanliness of the refl ector, typical S ource/ Refl ector effi ciencies are Q ua rt z L a mp s 0 to Q ua rt z Tu be s 0 to M e ta l S h e at h 5 to

55

a tts r D r yi n

B

C

 A  100

80 60 40 20 Pounds of Water Evaporated Per Hour

D 0

20

40 60 80 100 120 Kilowa tts of Infrared Energy R equired

140

Note — To evaporate solvents other than water, calculate the energy required to heat the solvent to vaporization tem perature using the w eight, specifi c heat and temperature rise. Calculate the latent heat of vaporization and add to the energy required to heat the solvent to v aporization temperature.

Technical

Technical Information

Radiant Infrared Heating - Process Applications Bak ing & Curing —  The nomograph to the

sti ma ti n g W a tt

right can be used to determine the watt density required on the work product for baking and curing of paints and coating. Lacquers are cured primarily by evaporation of the solvent and can be cured by infrared in 2 - 15 minutes. Enamels are cured primarily by polymerization and require a longer time (15 - 20 minutes). Varnishes, japans and house paints cure mainly by oxidation but can usually can be accelerated by infrared heating. To find approximate watt density needed for baking:

e si ty

r C r i g o r B a ki n 0.90

 Ve nt ila tio n A ir Feet P er Minute (Air at 80 °F)

0.75 0.65 0.50 0.35

C D

. L o ca t e  temperature product is to reach in

E

five minutes (A)

0

1

. R e a d a c ro s s  to line representing gauge of

2

3

4

5

6

 W at t D en si ty R e qui red on P rodu ct (W /In

the material being heated (B)

   n    i     d    e    n    i    a    t    t    A    e    s    t     b    e    o    u    n     T    i    F    M    e    v    i    e    r    F    u    t    a    r    e    p    m    e     T

2 G a u g e S h e e t S te e l

. R e a d u p to ventilation air in feet per

minute over surface of the product (C). If not known, estimate feet per minute based on cubic feet per minute of ventilation or circulating air divided by the the approximate cross sectional area of the oven. In applications with no forced ventilation, use 2 - 5 fpm.

   y    t    i    v    i    s    s    i    m    E    r    o    t    c    a    F    n    o    i    t    p    r    o    s     b    A

 W oo d

B 6 G a ug e

 A 

4 G a ug e 8 G a ug e 2 0 G a ug e

. Read right  to the absorption factor for the

work product surface or coating (ie: = 0.85 for enameled sheet metal) (D) . R e a d d ow n  to watt density required on

the product surface (E). Determining Hea ter Fixture S pacing —  Hav-

ing determined the total required kilowatts and the desired W/in 2 on the work product, the next step is to deterine the spacing and the number of heaters. In most conveyor type oven applications, a 12" spacing from the face of the heater to the work product produces uniform distribution of the radiation. The graph to the right shows centerline to centerline spacing of Chromalox radiant heaters to obtain various intensities on the work based on a spacing of 12" from the face of the heater to the work product. Specific applications may require the distance to be increased or decreased. The graph is applicable to line or point infrared sources installed in reflectors. Refer to view factor charts for ceramic heaters and flat panel infrared sources.

I n te si ty V s. pac i n g —

in t &

i n e I n rared

 A = QR T (3 /8 " Dia. Quartz Tube) B = R A D / QR T (1 /2 " Dia. Quartz Tube) C = S - R AD D = RA DD/U-RAD/QR  (3 /8 " Dia. Quartz Tube) E = U-RP

L

   t    c    u     d    o    r    P    r    o    W    n    o    n    I

rc es  

3-11/16"

E D

   W    e    g    a    r    e    v    A

C B

 A 

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

32

34

36

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Heater Center to Center Distance = L (In.)

I- 3

Technical

Technical Information

Radiant Infrared Heating - Process Applications  Wh ile t e radiatio n pattern fro m li e an d po in t in frared s r es can e co tr ed by re e t rs, t e radiatio n pattern fro m fl at pan els is diffu sed an d th e in frared en er y is emitted fro m a ar e area. Co se en tly, t e s ape o f t e so r e a d t e targ et are a sig ifi an t fa to r in determin in g th e Watt den sity fa in g n th e rk pr du t. r paral el su rfa es in applicati s s c h as t erm f o r mi g r eb eati t e i ide t e er y fa i g n t e rk produ t is determin ed y a “View acto r”. View fa to r is defi ed as t e per en tag e o r fra ti n in frared en er y leavi g th e s rfa e o f a at pa el (s r e) i h is i ter epted y t e su rfa e f t e rk pro d t (targ et). T e view fa to r fo r para el su rfa es (recta es) c an e determin ed fro m t e g raph . Example  —  F i n d th e view fa to r fo r a 12 y 2 " pan el eater m ted " r m a ti s eb i f rared dryi g app i ati . /L = 2 " ÷ " = /L = 12" ÷ " = . ead eft fr m t e in ter ept f L = 6 a d L = 3 ith a view ac t r f . .

 V ie w F a ct or f or F la t P a ne ls

View Factor for Two Parallel Sur faces  1 .0  0 .7  0 .5

S

L

 0 .4

S

 0 .3

.6

 0 .2

.4

   r  0 . 1 0    o    t    c    a    F  0 . 0 7    w    e    i    V  0 . 0 5

   L

.1

 0 . 0 4  0 . 0 3

ista c e B et w een r fac e s   L e n g th o f ec t an g e   Width f ectang e 

L

 0 . 0 2

X Y  0 . 0 1 0.1

0.2

0.3

0.5

1

2

3

4

5

10

20

/L

Heat re ired to h eat so ve t to 7 °F

Radiant Oven Hea ting Example  —  A ma

fa t rer o f 6 6 a n e e tric ater eaters is es to ake th e pain t n sh eet meta ackets (o pen t p an d tt m) at °F. T e ackets w ei h 3 s, are 2 " in diameter y " i h ith an tside area f 2 .5 t  2 . T e pr ess req ires 20 ja kets e pai ted per r. T e jackets w ill e s spen ded fro m a c o vey r ain n 9 t e ters a d i l e ro tated as t ey m ve. T e ch ain eig s 12 s/ft. T e h eaters ill b e i stal ed in a t el ven ith 2 i es f i s ati n a d re e tive a s. T e oven is 8 ft , 4 ft ide a d 7 ft i h a d as e d pe i s 3 f t y 6 t. re imin ary test resu ts sh w th e ja kets mu st e aked fo r six min tes f r a satisfacto ry is . T e pai t ei s .25 s/ g a l, c o tai s vo latiles a d c vers 212 ft 2  per g al . Assu me a ro m temperat re f 7 °F pe i c eat f steel = .12 t /l /°F i i g p i t f s ve t = 1 ° F pec i fi c eat f s ve t = . 4 t °F ate t eat f vap rizati n = 1 6 t /l Heat R equired for Operation — H e at A bs o rb ed by J a c k e ts —

(20 ac k ets r x 3 3 0

s=

0

s r)  

s r x 0 .12 t ° F x ( 0 - 7 0 ° F )   = .5 kW   12 t kW  H e a t A b s orb e d b y S o lv e n t

v

2 .5 f t2   x 2 0 jac k ets r x 5 % 212 ft 2 /g a I- 3

ve t

me  = 1.20 g a r

1.2 ph x 7 .25

Total Hea t Absorbed —

al x 0 . 4 t b x (1 -70 °F)= .1 kW 12 t kW 

Heat re ired to vap ri e so ve t  1.20 ph x 7 .25 al x 1 5 6 12 t / kW  

t b = .4 kW

Heat a s r ed y s ve t = .1 + .4 = .5 kW  Heat Required by Ventilation Air ( F P A reco mme dati n is a mi im m o f 1 ic feet per al n f s ve t evapo rated.) e siity f air = . 0 s/ft  pec i fi c h eat f air = .2 0 t °F Note  —

Ve ti atio n air is h eated y re-radiati n a d ve ti n r m t e w rk, o v e alls, etc . Air temperat re is alw ays less th an th e w rk temperat re. Ass me a 2 °F air temperatu re. V

me = 1.20 ph x 1

12

0 ft  h x 0 . 8

0 t   = 12

0 t  /h r 

t  x 0 .24 t ° F x (2 - 7 0 ° F )   12 t / kW  

Heat a s rb ed b y ven tilati n air = .7 8 kW  rma y C o nv e y o r C h a i n & H a ng e rs — t e vey r ain is tside t e radiatio n pattern f t e h eaters an d is eated y ve ti n fr m air in t e t e. i e t e h eat a s r ed y t e air as a ready b een acc ted f r, t e h eat a s r ed y t e vey r may e ign red. (Co veyo r speed s d pro vide 6 mi tes in th e 8 fo t h eated area.) 

.5 kW + .5 kW + .8 kW = 1 .8 kW   Heat Losses —  Heat sses fr m o ven su rface

ith 2 i c h es f i s ati n ( raph - 12 ) = 12 W/ft 2 . Assu me in side s rfac e temperatu re f w a l a d c e i i g = 2 ° F ,  ∆ T  = 1 ° F ) Wall area 7 ft x 8 ft x 2 ft = 112 ft 2  Cei i g a d r area 8 ft x 4 ft x 2 ft = 4 ft 2  pen t el e ds = 3 f t x 6 t x 2 ft = 6 t  2  Heat ss fr m o tside s rfa es f o ve 1 6 t2   x 12 W/ft 2  = 2.1 kW/h r 1 0 W/ kW   Heat ss fr m o pen ven en ds (ass me th e pen en ds are eq al to an in su ated meta su rfa e der th e same diti s as th e ven s rfa es) ( ee raph -12 .)  3 6 t2   x 0 .6 W / t2   x 1 ° F = 3 . 9 kW r 1 0 W kW   To ta l He a t L o ss e s —

2.1 kW + . 8 kW

. 9 kW   Total Hea t Ca pacity Re quired for Operation — 1 .8 kW + . 9 kW = 21.8 kW/h r 

As ith an y pro ess eat al ati , it is n t po ssib e to ac t fo r all th e variab es an d k s in th e app i ati . A safety fa t r is re mmen ded. r radian t h eati g applicati s, a safety facto r o f 1.4 is su ested. Total Heat Required = 21.8 x 1.4 =

.5 kW

Technical

Technical Information

Radiant Infrared Heating - Comfort Heating Indoor Spot Heating 

11.5

Infrared spot heating of work stat ions and personne l in large unheat ed structures or areas has proven to be economical and satisfactory. The following guidelines may be used for spot heating applications (areas with length or  w idth le s s th an 0 fe et

1.

2.

.

.

.

.

.

6 0 ° e e c to r 22° Tilt 10 W 

W/2 

e te rmi n e   the equivalent ambient temperature desired (normally 7 F is the nominal average). tra c t 1 from 2 to determine the theoretical increase in ambient tem perature ∆T  ) expected from the infrared system. If drafts are present in the occupied area (air movement over 4 4 feet per minute (0 .5 mph) v elocity), wind shielding or protection from drafts should be considered.

o u n tin g Heig h t  

.

etermin e  fi xture mounting locations a)  In areas w here the width dimension is 5 feet or less, use at least two fi xtures mounted op posite each other at the perimeter of the area and tilted at an angle. This provides a greater area of exposure to the infrared energy by personnel in the work area. Tilt the xtures so that the upper limit of the xture pattern is at approximately s ix feet above the center of the work station area (Figure 2 ). )  W hen locating fi xtures, be sure to allow adequate height clearance for large moving equipment such as cranes and lift truck s. )  Av oid directing infrared onto outside  walls stimate   (tentatively) the radiated pattern area. Add length of fi xture to the fi xture pattern width (W ) to establish pattern length (L). Pattern Area = L x W (Fig. ).

ixture Location

A

le i f rm adiation

W Width o f R adiation attern

etermin e  the area to be heated in ft  . This is termed the “des ign or work area” (A D) (Fig . 1 ) .

ti p y  the design area by one watt per squ are foot times the theo retical temp erature increase ( ∆T ) des ired as determined in Step 3 (minimum of 1  w at ts pe r s qu are fo ot . T he de s ig n f acto r of one watt per square foot density assum es a xture mounting height of 1 0 feet. Add 5 for each foot greater than 1 0 feet in mounting height. Avoid mounting fi xtures below 8 feet

Figure 2 — Tilted Infrared Fix-  tures for Spot Heating 

Figure 1 — Design Area 

e te rmi n e  the coldest anticipated inside ambient temperature the sys tem m ust overcom e. If freeze protection is provided by another heating s ys tem, this temperature will be 4 F

W/2  W 

Figure 3 — Pattern Area 

ivide the design area (S tep 4 ) into the pattern area (S tep 7 ).

accomplished by using m ultistage air thermostats set at different temperatures.

Q=

Indoor Area Heating 

Pattern Area Design Area 

If the pattern area is equal to or greater than the des ign area, quotient (Q) w ill be equal to or greater than 1 and coverage is adequate. If Q is less than 1 , the design area exceeds the pattern area of individual xtures. A djust the heater locations and patterns or add additional xtures with patterns overlapping as necessary, to ensure adequate coverage.

.

(Q in Step 8 ) by the ti p y quotient   increase in theoretical temperature ( ∆T of Step 3 ) by the design area (A D of Step 4 ) to determine the amount of radiation to be installed.

Radiation (W atts) = Q x

10 .

∆T  x

A D

a n y Type s of   radiant heaters are available for comfort heating applications including ceiling, w all and portable fl oor standing m odels. Choose s peci c fi xtures from the product page s. It is preferred that half the wattage requirements be installed on each side of the work station in the design area.

C tr ls  Manual control by percentage timers may be adequate for a small installation. To provide bette r control of comfort levels in  v ary ing am bie nt te m pe rat ure s , d iv ide the t otal heat required into tw o or three circuits s o that each fi xture or heating element circuit can be sw itched on in sequence. S taging can be

In many industrial environments, area heating (areas with length or width greater than 5 ft) can be accomplished economically with multiple infrared heaters. For quick e stim ates , determine the minimum inside temperature and use a factor of 0 .5 watts per square foot of des ign area for each deg ree of theoretical temp erature. If the calculated heat loss of the structure, including infi ltration or v entilation air, is less than the quick estimate, select the lower  v alu e. L ocat e h ea te rs unifo rm ly th roug ho ut the area with at least a 3 % overlap in radiation pattern.

Outdoor Spot Heating  The s ame guidelines outlined under Indoor Spot Heating should be followed except that  w at ts per s qu are fo ot fo r ea ch de g ree of theo retical ambient tem perature increase s hould be doubled (approximately 2 watts per square foot for each 1 F). This factor applies to outdoor heating a pplications with little or no wind chill effect on pers onnel. If w ind velocities are a factor in the application, determine the equiv alent air temperature from the W ind Chill Chart in NEMA publication HE3 -1 1 or other information source.

o te  — Increasing the infrared radiation to massive levels to offset wind chill can create discomfort and thermal stress. In outdoor expos ed applications, a wind break or shielding is usually more effective. -3

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Technical

Te

i al In rmati

e tri al

dame ta s T ree ase Ca

O hm’s Law

hea

e a

ed

s Law

h ic h s t a te s

e c u r re n t n a r e s is t a n c e h e a

hm

s L aw

I

E  R 

s tr a d i

na

h e re : I

=

E

=

ol age

R

=

hm s

r vo

n un kno

p e re s

o k no

on s of

hm

e s is ta n c e )

he co nven

=

p e re s

V =

ol age

R

hm s

=

n va ues

e s is ta n c e )

o b e c o n n e c t e d to a w d e e r a t io ed

OHMS = VOLTS 2    WATTS 

AMPERES =

WATTS  VOLTS 

AMPERES =

WATTS  OHMS 

WATTS  WATTS

=

VOLTS x AMPERES 

WATTS

=

AMPERES 2  x OHMS 

WATTS

=

VOLTS 2  OHMS 

 

 Applied  Voltage  110

115

120

208

Rated Voltage  230 240 277 380

220

on

d asse

415

440

460

480

575  

  

  

  

  

  

 

bl es

a n g e o f o p e ra t n g

a t a g e o u t p u t v a r ie s

o l a g e s , h e a c tu a l r an y ap

a-

OHMS = WATTS    AMPERES 2 

VOLTS OHMS 

Percent of Rated Wattage for Various Applied Voltages

n ly p o d u c e s

ag e. t s co

o r e le c t c h e a t n g e le m e n s a

h

VOLTS  AMPERES 

AMPERES =

n a t h e r ig h

a te d W a t a g e a t a te d V

r e c t ly w

OHMS 

u r re n t

n o ne o f he va

n e le c t c r e s is ta n c e e le m e n t

n c e th e

WATTS  AMPERES 

on alab-

Voltage & Wattage Relationships

ol ag es.

VOLTS =

OHMS =

s Law sho

V  WR  R   W  W  V  I  W  V   I  IR  (VOLTS) (AMPS) R  V  (OHMS) (WATTS) VI  R  W  I  I 2 R  W  2  2  V  I 2  V  W  R 

u r re n t

n e le c t c a l v a lu e c a n b e d e r iv e d b y

u s in g a n y

WATTS X OHMS 

VOLTS = AMPERES X OHMS 

ag e s: h e re : I

V  R 

I

g e em en

y exp ressed as:

T h e s a m e e q u a t o n u s in g r e v ia t i n

VOLTS =

n e d b y a p e c is e

p h y s ic a l u le d e fin e d a s O h m

 AMPERES 

ut

a g e o f e le c r ic r e s is t a n c

n g e le m e n s is d e te r

at

OHM’S LAW

VOLTS 

T h e re la t o n s h p b e t e e n W a t a g e ( h e a t ) o u an d

atio s 

f

e s

are o f

a t a g e c a n b e c a lc u a te d

a g e . T h e r e la t

sh p

e x p r e s s e d b y th e e q u a t o n b e lo w h e re :

V 2  W A = W R x A V R2 

 A  =

A c tu a l

R  =

( )

 A  R 

at age

a te d W a t a g e

= A pp

ed V

= R a te d V o

ag age

T hree Phase Equations (Balanced) s L a w , a s s a te d a b

ve, ap

3

3

D elta

e s t o e le c t r

I L 

c a l e s is ta n c e e le m e n s o p e a te d o n s in g ph ase ci cui s.

hm

s Law can b e m od

ed

o c a lc u a te th r e e p h a s e v a lu e s b y a d d in g c o r re c t i n

actor f r t e p

ase

R 1 

R 2 

a g e r e la -

ci cu en

V L = V P = I L = I P = W T = R 1  = Wc  = Rc  =

.

I P  R 2 

V P 

V P 

V L 

I P 

o n s h ip s . T h e th r e e p h a s e e q u a t o n s s h o w can b e app

Wye

V L 

R 1 

e d t o a n y b a la n c e d D e l a o r W y e

e te r m s u s e d

n the e

at

s are

R 3 

R 3 

fie d b e l

I L 

I L 

L in e V o l a g P hase L ne

ol age u r re n t

P hase To al  =

ur ent at

e s is ta n c e

cu t (Eq

al

cu

s)

e s is ta n c e in O h m s M e a s u r e d

h a s e to P h a s e

I-36 

ps)

 = E e m e n t

at ag e pe r c u it

ps)

V P = W T = I P = W C = R C =

V L = W T = I L =

L

1 .7 3 I L  x L  ÷

1 73

1 .7 3 I L  x

Note  —

L

2 x

L

L

)÷

For O pen page.

÷

P

3 (V P  x

L

 ÷

1 .7 3

rcu C

R C

=

L

 ÷ 0 .5 W

ela con nect on s,see next

C

V P = W T = I P = W C = R C =

L  ÷

V L = W T I L =

1 7 3

1 .7 3 I L  x

L

L

1 .7 3 I L  x

Note  —

2 x For

L

L

)÷

÷

P L

 1

 ÷

P

rcui C

R C =

L

 ÷ 0 .5 W

p e n W y e co n n e c t o n s , s e e n e x t

page.

C

Technical

Technical Information

Three Phase Equations & Heater Wiring Diagrams pen

e ta & Wye  

Typical Heater Wirin g

Three phase heating circuits are most efficient when operated under balanced conditions. If it is necessary to operate an unbalanced load, the equations below can be used to calculate the circuit values for open three phase Delta or Wye circuits. The terms used in the equations are identified below:  V L   =  V P   = IL  = ILL  = IP  =  W T  = R  = R c  =

Line Voltage Phase (Element) Voltage Line Current (Amps) Line Current (Unbalanced Phase) Phase Current (Amps) Total Watts R2 = R3 = Element Resistance Circuit Resistance in Ohms Measured from Phase to Phase

3Ø

pen

 V P

L 1 P ha s e Power Source L Heater(s)

Heater(s)

I   LL   = 1 7 3

 I P

pen Wye  

R 

IP

R 

3 Phase Power L2 Source L Fused Disconnect Switch

DPST Thermostat 

Fused Disconnect Switch

IL

 V L  = VP  2  W T  = VL 2 ÷ 2R1 IL  = IP

The loss of a phase or failure of an element in a three (3) element Wye circuit will reduce the wattage output by 50%. Heating elements are basically in series on single phase power.

Heater(s)

Three P hase A C hea ter circuit where line voltage and current do not exceed the rmostat rating. Circuit does not have a “positive” off.

 V P

 V L

or Phase P ower Source

1 or Phase Power Source

Heater(s)

Sensor T/C or RTD

Electronic Temperature Control

Single or Three Phase AC heater circuit using electronic tempe rature controllers and contactors. Controller and contactor holding coil must be rated for the same voltage as the heater circuit. Control circuit requires over- current protection. Circuit B re a k e r 1 or Phase Power Source

High Speed Fuses

SCR Power Controller Heater(s)

L L L

Se nsor T/C or RTD

Single or Three Phase AC heater circuit using an electronic temperature controller and a SCR (solid state) power controller Controller must be rated the same voltage as the heater circuit. Control circuit requires over-current protection. All electrical wiring to electric heaters must be installed in accordance with the National Electrical Code or local electrical codes by a qualified person.

Wirin g & Am ie t Temperatu res 

L

L 

The loss of a phase or failure of an element in a three (3) element Delta circuit will reduce the wattage output by 33%.

VL  ÷ IL  x VL IL VL 2 ÷ WC

Fused Disconnect Switch

 V L

 V   = VP  W T  = 2 (V L 2 ÷ R1) IL  = IP

Fused Disconnect Switches

Electronic Temperature Control

ILL

VL 2VL  x IL IL 2VP  x IP

Contactor L L L

S i n g l e P h a s e 1 0 V A C h e a t e r c irc u it w h e re l i n e v o l ta g e and current do not excee d thermostat rating.

Single Phase AC circuits w here line voltage a nd current do not exceed thermostat rating.

R 

 V P  =  W T   = IP  = R C  =

SPST Thermostat 

1 Phase L Power Source L

IP

Ø

Fused Disconnect Switch

DPST Thermostat 

R 

 V  =  W T  = IP  =  W C =

The following diagrams show typical heater wiring schematics.

e ta   IL

P 

iagrams 

Contactor

L L L L L

Heater(s) DPST Thermostat 

Single or Three Phase AC heater circuit where line v oltage and current excee d thermostat rating. Separate control circuit can use a single pole or double pole thermostat. Control circuit requires over-current protection.

 W A R N IN G — H a za rd of El e ct ri c S h oc k . Any installation involving electric heaters must be effectively grounded in accordance with the National Electrical Code to eliminate shock hazard.

Ambient temperatures must be considered when selecting wiring materials for electric heater circuits. Heating equipment and processes may cause associated wiring to operate well above ambient temperatures. These temperatures may result from heat conducted from the heater terminals, radiation from heated surfaces or simply high ambient air temperatures. Nickel plated copper or nickel alloy conductors with high temperature insulation should always be used in high temperature areas. Outside these areas, conventional wiring materials can usually be used. 60°C building wire is usually not suitable unless otherwise indicated.

W i ri n g i n

evere C o n di ti o n s  

Moist or wet locations require gasketed terminal and junction boxes to protect equipment and wiring. Rigid conduit is recommended. Hazardous Locations require the use of approved explosion-proof terminal and junction boxes. Rigid conduit or mineral insulated (MI) cable is mandatory in Division 1 areas. Some Hazardous Locations may require conduit seals (EYS) adjacent to the equipment.

I- 3

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

Technical

Technical Information

Wiring Practices for Electric Heaters e

at on

on

ors

The selection of wiring materials to be used in a particular application depends upon the service Voltage and the anticipated operating temperatures. The table below lists s ome of the more com mon code wire constructions according to their temperature limitations. Insulated wires s hould be derated for elevated ambient temperatures and should never be used abo ve their temperature rating. The operating tem perature of unplated copper wire should be limited to °C (3 F) maximum.  A co m plete lis tin g of w ire c ons tru ction an d allowable current carrying c apacities is show n in the National Electric Code Article 3

he

o co u p le

e

h e r o c o u p e C o lo r Type   J K T E R 

 

 h ite Y e llo  B lu e P u p le B aFN

p o se

S

 

B aFN

Max. Conductor  Temperature  Wire  Type  °C °F   (600V)

N

Cons truction  (Copper Conductors)

T R   T    R TN

T h e m o p la s tic Rubbe Themoplastic  e a t R e s i s ta  t R u b b e   e a t R e s i s ta  t     Themoplastic  N  e a t R e s i s ta  t C o s s  QN 7 er P sW M T    e a t R e s i s ta  t C o s s  QN 7 er P sW F E P   7 e R Q  

g h T e m p e ra t

e

g M a t r ia l

Max. Conductor  Construction  Temperature  Wire  Type  (Nickel Plated Copper or °C °F   (600V) Nickel Conductors) e R Q - G ss - 7 e R Q   T T TT M S M i c a   la s s  S ilic o  e F a - G ss - 7 e R Q   M T Qese 1 e B a e   ie o  B u s B a s  ith C e  a m i c I  s u la t o  s

Note —  ig h t e m p e  a t u e  i i g m a t e i  s re e IRr  e  WQ

o n a c to r S z i Contact ors are normally rated for inductive and resistive loads. Most electric resistance heaters have negligible inrush or inductive current. Select contactors based on resistive load ratings. Us ing the formulas s hown in the paragraphs on  w ire s izin g to dete rm ine the amp load per pole (phase). Select a contactor with the next highest current rating. Use a two pole contactor for single phase ( two-wire) power and a three pole contactor for balanced Delta or Wye three phase loads. For heater loads w ith high inrush current, refer to product data information for maximum amperage.

I-38 

ri g H

Thermocouples and extension lead wires are color coded to aid in identifi cation and to av oid inadvertent cross wiring. The following charts indicate the colors us ed of different alloys

Positive  Color ( + )

e n e ra l

abl

O a  g e

odi

Io  C o  s ta  ta  C h o m e l  lu m e l C o p p e  C o  s ta  ta  C ho m e l C o s ta  ta  PlatiumPlatium    ith   % R h o diu m  PlatiumPlatium    ith  % R h o diu m  N ic o s il N is il

Wr

h e r o c o u p le E x te n s o n Type T  J E K  R o S B

eQW e

e C o lo r s

Color  Positive Negative  Overall  TP  J P EP KP SP BP

TN  J N EN KN SN BN

Blue aFN P uple e l lo     e e   a   

Note — 1 e W e (-) F Q   ith e d c o lo e d i s u la tio 

e c tr ic a l o i se

Wr

Positive  Color  (+ ) Blue   h ite P uple e llo    aFN  a   

eQW e

on rol

Electrical “noise” refers to extraneous electrical  voltag es that interfere w ith leg itimate control signals. M ost electrical noise is introduced by electromag netic coupling with fl uorescent lights , contactors, power wiring, s witches and other arcing devices. S hield control circuit wiring and eep thermocouple wires s eparate from power  wiring. Tra ce s hielded thermocou ple lead wires in a separate conduit for maximum protection.

Tem perat e L

e a t er s

The following are some general recommendations for wiring electric heating elem ents and ass emblies. These recomm endations are only sug ges tions and are not intended to confl ict  w ith the N at ional E lectric C od e o r loc al c odes

WARNING — Hazard of Electric Shock. A ny

Alloys  

Note — 1 e W e (-) F Q   ith e d c o lo e d i s u la tio 

s o r E e c r ic

s or C on rol

Most mechanical controls and thermostats (control bodies) can withstand a w ide range of ambient temperatures ranging from below freezing to over F. Electronic controls, transformers , contactors and other electrical devices are more temperature sensitive and extreme temperatures will usually shorten the life of the component . Mos t electrical and electronic equipm ent w ill function accurately in ambient temperatures ranging from about °F to about 1 F. Triacs and SCR controls frequently require special cooling for full load ratings when operated over F. Refer to the installation instructions or contact the d evice manufacturer for recommendations.

installation involving electric heaters m ust be effectively grounded in accordance with the Nat ional Electrical Code to eliminate s hock hazard. A ll electrical wiring to electric heat ers must be installed in accordance with the National Electrical code or local electrical codes by a quali ed person.

1. Repet itive heating and cooling can cause  w iring conn ectio ns to loos en ov er tim e. High amperage through a loose terminal can cause overheating and terminal failure. All heater term inal connections should be tightened to a m aximum torque consistent with terminal strength. Use a secon d wrench or pliers to prevent twisting heater terminals.

2. Us e stranded w ire in applications w here the pow er wires to heater terminal connections m ay be subject to movem ent.  W he n u s ing s olid w ire o r bus ba r on heater terminals, provide expans ion loops between points of support to m inimize damaging s tress es due to expansion and contraction

3. S older or silver braze lead connections to heating elements that m ay be s ubject to extreme temperatures or vibration. Use a minimum of fl ux to complete the connection and eep fl ux from contaminating the heating element. Rem ove residual ux to prevent corrosion of the electrical joint.

4. Keep thermos tat capillary tubing and thermocouple w iring clear of heater terminals to prevent accidental short circuits. S leeving or insulated tubing is recommended

5. Us e wiring suitable for the anticipated operating temperatures. Unless the heater is specifi cally m ark ed for use with low temp erature copper wiring, high tem perature alloy conductors are recommended for connections to the heater terminals.

6. Do not use rubber, wax impreg nated or plastic cov ered wire inside terminal enclosures of heaters in high temperature applications. Thes e insulations w ill deteriorate and give off fumes which can contaminate the heating elements and cause short circuits.

Technical

Technical Information  Wiring Practices for Electric Heaters (cont’d.) Selecting Wi re Siz e (AW G ) e s iz e ( w r e g a co

e) of

h e h e a t in g sou ce.

Single Phas e

e e le c r ic a

ctor f r a p art cu ar ap

d e p e n d u p o n th e A

Table II — Ampera ge (Cu rrent) for Typical kW H eater Ra tings

ca

kW 

n

p e r a g e ( c u r re n t)

oad

ldraw

om

h ic h

he po

u r re n t c a n b e c a lc u la te d b y

su

y,

n a s in g e p h a s e e am

hm

o-w

To al

rcu t

hree p hase po

   

h b a la n c e

y: To al

rcu t

L in e

on kW

h e lo a d c u r re n t h a s b e e n d e t e r

at ng s.

al

a b e s in

ectr cal e ri

em

erat re ap

0 °C

r t c le 3

e (N on

            

480V

208V

   

Three Insulated Conductors in a Rac eway or Conduit  C oppe C oppe  1 eO 1 LFN eO W e

ay b

f

en

e N ae, Tab

ed am

n s u a te d w

cati

e in a 3

0

). s a

t s ts r e c o

o r th e m o r e c o m

 

440V

   

240V

440V

480V

575V  

       

 

                

                

   

aci es

e s fo r h ig h

s . C u r re n t r a t

Isulatio Tpe   m b ie  t  Temp

s for

°C a m b ie n t a r e i c lu d e d

or

r e fe r e n c e .

   

Table III — Allowable Ampacities C o  d u ct o Tpe

ned

e s iz e fo r th e c a lc u la te d a m p e r a g e

I at

          

240V

o l a g e x 1 .7 3

s ts a m p e r a g e s fo r c o m

s e le c t e d f r m

   

208V

a t ta g

All owable Ampaciti es nce



g lo a d s , n e a m p e a g e i

3 P h A m p e a ge

T a b le II

y:

ag

er ci cui s w

ye h eat

c a lc u a te d

e) pow er

a t ta g

Li e V

el a o r

ol ow ng

e r a g e p e r l e is c a lc u a te d

1 P h A m p e a ge n



er

a w . T o c a lc u a te a m p e a g e , u s e th e o r m u la s .

120V

Three Phas e Balanced Load  

S iz e    

Single Conductor 1,2  in Free Air (200°C Ambient) 1L e 1L e

C o a te d Coppe C o p pe  TN FEP T T M T M T     P F   TT M S M S M T   SR TF E C C C C C F F F F F M a  im u m C o  d u c t o  T e m p e  a t u e  I  s u l a t io  L i m i ts  C C C C C F F F F F

Corrections for Elevated Ambient Temperatures T h e re c o m

end ed cu

e n t c a r r y in g c a p a c

f 2 0 0 ° C a n d 2 5 0 °C

es

e a r e v a l d if c o n d u c

o r te m p e a tu r e s d o n o t e x c e e d 1 0 4 °F ( 4 0 ° pe at ng

e m p e a tu r e s in e x c e s s o f 1 0 4 °

( 4 0 ° ) re q

re t e ap

c o r re c t i n f a c t r

Example  —

c a t i n o f a te m

r

ze 14 AW

33

g w re.

, ype TG T w

c a p a b le o f h a n d l n g 3 9 40 ° ) bu t

erat re

e c o r re s p

e i

peres at10 4°

ust be reduced

o 0 85

85

) or

p e r e s w h e n o p e ra te d a t 2 1 2 °F (1 0 0 °

Multi ple Insulated W ires in Conduit Th e w n

e s iz e s e le c te d a b o v e m a y b e u s e d

e h ea

g c ir c u it

en cl se d n ri d he

ng . f

s ta l e d co

n

ect on

h

r fle x

ree (3) w res e c

t o

e sa a c to r m

e co

, an

er current

st be us ed . Fo r 4 to 6

c o n d u c to r s in a s in g e c o n d u it u s e 8 0 % ecom

rotect

e th a n 3 c o n d u c o r s a r e

e n d e d c u r re n t c a r y in g c a p a c

of he y.For 7

Correction Factors for Elevated Ambient Temperatures    m b ie  t  F o  a m b ie  t t e m p e  a t u e e  c e e d i  g t h e v a lu e s i t h e a b o v e t a b l e  C m u l t ip l t h e a l lo  a b l e a m p a c i t ie s b  t h e a p p  o p ia t e f a c t o  b e l o                                                                              a t a d e  iv e d o  e  ta p o l a t e d f o m v a l u e s a  d c it e ia s e t f o t h i N E C  t ic le

  m b ie  t  F                                       

 M  T & M  S i s u l a t e d  ie i s i t e  d e d t o b e u s e d f o  i  te  c o   e c t i o  o f s t  ip h e a t e  s a  d e le m e  t s l o c a t e d i  h ig h t e m p e  a t u e a m b i e  t s a  d is  o t i t e  d e d f o  g e  e  a l p u  p o s e  ii g   o  o t u s e t h e s e  m p  a t i g s f o  t h e e i  s u la t e d c o  d u c t o  s i s i d e aceas o coduits

o 2 4 c o n d u c to r s u s e 7 0 %

I-39 

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

Technical

Reference Data 

Pressure-Temperature Ratings of Common Flange Materials 

Recommended Maximum Pressure-Temperature Ratings1 for C ata log F la nge Immersion & Ci rculati on Heaters2 C ass 15 0 (P ressu res in psig )

Temp. (° F )   - 0 to

1 1 1 1 1 1 1 1 1 1 1

0 0 1 1 2 2 3 3 4 4 5

00 50 00 50 00 50 00 50 00 50 00

C ass 3 0 0 (P ressu res in psig ) C ass 6 0 0 (P ressu res in psig )   - 16 . 5 a teria l ro u p N u m b e r   1.1 1. 2.1 2.2 2. 2. 2. 1.1 1. 2.1 2.2 2. 2. 2. 1.1 1. 2.1 2.2 2. 2. 2. Auste itic teels  Auste itic teels  Auste itic teels  Allo y  Allo y  Allo y  Type  Type  Type  Cart ee l Type  Carte e Type  Carte e l Type  304L 304L 304L 1 1 1 1 Cr- Type  Type  Type  3 4 7 , 1 Cr Type  Type  Type  3 4 7 , 1 Cr- Type  Type  Type  3 4 7 , Temp  te e l 1 2 16 1 21 te e l 1 2 16 1 21 te e l 1 2 16 1 21 (°F)  - 0 to 1 ,4 8 1 ,5 0 1 ,4 4 1 4 4 0 1 ,2 0 1 ,4 4 1 ,4 4 1 ,3 5 1 ,4 2 1 ,2 0 1 2 4 0 1 ,0 1 1 ,2 2 1 ,2 7 1 ,3 1 1 ,3 4 1 ,0 5 1120 1 ,0 9 1 ,1 7 1, 1, 1, 1 ,2 0 1 ,2 8 1 ,0 3 1 ,0 9 1 ,2 1 1 ,0 7 1 ,1 7 1 ,0 6 1 ,1 3 1 ,0 1 1 ,0 6 1 ,0 1

1 1 9 1 2 3 4 5

AA A A A A A A

Material Group s ,A -L F -F , A -F -F ,F H a nd A -F ,F H a nd A -F L, F L a nd A -F ,F H a nd A -F ,F H a nd A

1 1 1 1 1 1 1 1 1 1 1

N ote s  A , B C D -

L , ,

H H

E, F G H

. T he a bov e ta ble is in a cco rda nce w ith A N S I B .5 , 1 8 E dition. F or othe r m a te ria ls , critica l a pplica tions or for hig he r pre s s ure  P S r r rT LrP nV, rIr R A  . .5 Rr F RnF  RX r RF O& K rRP ORx OV RI F . . rVVX r-P S rr rLnJ V IRrA  S rVVX r Y VVOV n  nJ V P y r IrRP K Y O V VKRw n Ln K ERY  EO X  R &R rTX LrP nV, r-LnIRrFP nn OLJ P nFOFX OLRnV. & RnFy RX r RF O& K rRP ORx OV RI F  IRrIX rK rLnIRrP LRn n VS FL F rFRP P nLRnV IRr  &R  nJ V n KrV.

Other Notes —  A . N o t re co m m e nd e d fo r p ro lo n g e d u s e a bo v e F . D R nR V 5 nJ V E R  °  Rr - 7 0 S O R r 8 °  & . D R nR V -   2  nJ V E RY  6 5 °  D . N ot re com m e nde d for prolong e d u s e a bov e 1 °F . D R nR V -  nJ V Rr - 3 0  S O E R  ° . R nR V -  nJ V Rr - 3 1  S O E R  ° . R nR V 1  nJ V Rr 1 RY r °. . D R nR V - 7  nJ V Rr - 3 4 7 S O E R  °.

Pi pe Specificati ons — Standa rd (Schedule 40) Steel & Stai nless Pi pe o m in a l i pe S i z e   /8 /4 /8 /2 /4 -

-40

i pe   c h e du l e   S ch 4 0 (S td S ch 4 0 (S td S ch 4 0 (S td S ch 4 0 (S td S ch 4 0 (S td S ch 4 0 (S td S ch 4 0 (S td S ch 4 0 (S td S ch 4 0 (S td S ch 4 0 (S td S ch 4 0 (S td S ch 4 0 (S td S ch 4 0 (S td S ch 4 0 (S td S ch 4 0 (S td S ch 4 0 (S td S ch 4 0 (S td S ta nd a rd S ta nd a rd

tsi de D i a. Wall Th ic kn ess  (I .)  (I .)  0 .4 0 0 .0 6 0 .5 4 0 .0 8 0 .6 7 0 .0 9 0 .8 4 0 .1 0 1 .0 5 0 .1 1 3 1 .3 1 0 .1 3 1 .6 6 0 .1 4 1 .9 0 0 .1 4 2 .3 7 0 .1 5 2 .8 7 0 .2 0 3 .5 0 0 .2 1 4 .0 0 0 .2 2 4 .5 0 0 .2 3 5 .5 6 0 .2 5 6 .6 2 0 .2 8 8 .6 2 0 .3 2 10 75 0 .3 6 12 75 0 .3 7 14 00 0 .3 7

I n s i de D i a . (I .)  0 .2 6 0 .3 6 0 .4 9 0 .6 2 0 .8 2 1 .0 4 1 .3 8 1 .6 1 2 .0 6 2 .4 6 3 .0 6 3 .5 4 4 .0 2 5 .0 4 6 .0 6 7 .9 8 10 02 12 00 13 25

In side  Area (In 2 )  0 .0 5 6 8 0 .1 0 4 1 0 .1 9 0 .3 0 0 .5 3 0 .8 6 1 .4 9 2 .0 3 3 .3 6 4 .0 7 7 .0 3 12 20 28 50 78 113 13 7

73 01 89 00 90 10 .9 0

We i t   ( s/ F t . )   0 .2 4 0 .4 2 0 .5 6 0 .8 5 1 .1 3 1 .6 7 2 .2 7 2 .7 1 3 .6 5 5 .7 9 7 .5 7 9.11 10 79 14 62 18 97 28 55 40 48 49 56 54 57

V lume  ( a l/ F t . )   0 .0 0 3 0 0 .0 0 5 4 0 .0 0 9 9 0 .0 1 5 7 0 .0 2 7 7 0 .0 4 4 9 0 .0 7 7 9 0 .1 0 0 .1 7 0 .2 4 0 .3 8 0 .5 1 0 .6 6

Wt. Water  ( s/ F t . )   0 .0 2 4 6 0 .0 4 5 1 0 .0 8 2 7 0 .1 3 1 6 0 .2 3 0 1 0 .3 7 0 .6 4 0 .8 8 1 .4 5 2 .0 7

12 21 34 49 59

51 69 10 00 70

Th ds/In. ( T)  

11 11 11 11

-

0 0 1 1 2 2 3 3 4 4 5

00 50 00 50 00 50 00 50 00 50 00

Technical

Reference Data  Physical & Thermodynamic Properties of Common Liquids Substance Acetic Acid Acetone Allyl Alcohol Ammonia Amyl Alcohol Aniline Bromine Butyl Alcohol Butyric Acid Carbolic Acid (Phenol) Carbon Disulde Carbon Tetrachloride Caustic Soda (50% Solution) Decane Di-ethyl Ether Ether Ethyl Acetate Ethyl Alcohol Ethyl Bromide Ethyl Chloride Ethyl Iodide Ethylene Glycol Ethylene Bromide Ethylene Chloride Formic Acid Glycerin Heat Transfer Fluids Dowtherm A Dowtherm G Mobiltherm 603 Therminol VP-1 Heptane Hexane Linseed Oil Methyl Acetate Methyl Alcohol Methyl Iodide Nitric Acid (100%) Nitrobenzene Octane Olive Oil Pentane Petroleum Products   Asphalt Benzene (Benzol)   Kerosene Fuel Oil #6   Gasoline Lube Oils Parafn (Melted)   Toluene Propionic Acid Propyl Alcohol Soy Bean Oil Sulfur (Melted) Sulfuric Acid (100%) Tallow (Lard) Turpentine Water Xylene (Ortho)

Density1 (Lbs/Ft3) 65.5 49.42 53.31 43.5 51.06 63.77 194.7 50.54 60.2 66.7 78.9 99.47 95.4 45.6 44.61 46 52.3 49.27 90.5 56.05 120.8 69.2 136.5 71.75 76.13 78.69

Specific Heat (Btu/lb/°F) 0.522 0.514 0.665 1.099 0.65 0.512 0.107 0.563 0.515 0.561 0.24 0.201 0.78 0.5 0.541 0.503 0.468 0.68 0.215 0.368 0.161 0.555 0.173 0.294 0.526 0.576

66.1 65.4 53.7 65.9 42.68 41.18 58.28 57.84 49.42 142.58 94.41 75.63 44.12 57.28 39.37

0.377 0.377 0.592 0.377 0.532 0.6 0.44 0.468 0.601 — 0.42 0.35 0.51 0.471 0.558

62.3 54.85 49.9 58.5 41.2 55.4 44.3 54.03 61.77 50.16 57.35 14.6 114.25 58.66 54.48 62.4 55

0.42 0.412 0.5 0.41 0.5 0.43 0.71 0.404 0.473 0.57 ~ 0.28 0.234 0.344 0.64 0.42 1 0.411

Thermal Conductivity (Btu/in/hr/ft2 /°F) 1.19 1.22 1.25 3.48 1.13 1.2 — 1.07 1.13 — 1.12 0.744 — 1.03 — 0.97 1.21 1.26 — 2.15 2.57 1 — — 1.25 1.36 — — — — 0.89 0.86 — 1.12 1.49 — 1.92 11.52 1 — 0.79 5.04 1.02 1.03 0.85 0.936 — 1.68 1.08 1.2 — — — — — 0.876 4.17 1.08

Melting Point (°F) 62 -140 -200 107 -110 21 19 -130 20 106 -169 -9 — -21 -177 — -116 -174 -182 -214 -163 — 50 -35 47 68

Latent Heat of Fusion (Btu/lb) 84 42.1 — 142.9 — 48.8 28.5 54 54.1 52.3 — 12.8 — 86.9 42.4 — — 46.4 — — — — — — 118.9 85.5

54 40 — — -132 -40 -4 -144 -144 -87 -42 42 -70 — -202

42.2 42.2 — — — — — — 42.7 — 71.5 40.5 — — —

— 42 — — — — — -139 -5 -197 — — 51 50 - 106 14 32 -13

— 54.2 — — — — — — — — — — 43.3 — — 143.6 —

Boiling Point (°F) 245 133 206 -28 280 364 138 244 326 360 115 170 — 345 94 95 171 173 101 54 162 388 269 183 213 554

Latent Heat of Vaporization (Btu/lb) 174.2 224 294.1 583 216.3 186.6 79.4 254 217 — 148.8 83.5 — — 151 160 183.8 367.5 107.8 165.9 82 344 99.2 139.2 216 —

Viscosity Centipoise 1.222 0.31 1.363 — — 4.467 1.005 2.948 1.54 12.74 0.376 0.975 — 0.77 0.245 — 0.45 1.2 0.402 — 0.592 — 1.721 0.838 1.784 830

494 551 — 495 210 155 548 134 148 108 187 412 258 ~ 572 97

127 123 — 130.6 137.3 142.5 — 176.6 473 82.6 270 142.4 131.7 — 153.6

— — — — 0.416 0.326 33.1 0.388 0.596 0.5 — 2.1 0.542 84 0.24

— 176 — — 128 - 164 — ~ 525 231 286 208 — 833 638 — 319 212 291

— 169.4 — — — — — 155.7 177.8 296 — — 219.7 — 123.5 972 149.2

— 0.654 — — — — — 0.59 1.102 2.256 40.6 — 50 17.6 1.487 1.005 0.881

1. Where the temperature is not given, room temperature of 68°F (20°C) is understood. Other Notes — A. Dowtherm is a trademark of the Dow Chemical Company. B. Mobiltherm is a trademark of the Mobil Oil Corporation. C. Therminol is a trademark of the Monsanto Company.

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

I-41

Technical

Reference Data  Properties of Air Specific Heat, Viscosity & Density (Weight) of Air at Various Pressures & Temperatures  Specific Air Heat Temp (Btu/  (°F) Lbs/°F)                                                                                  

Absolute Viscosity (Lbs/  Ft/Hr)                                                                                 

0                                                                                 

10                           

                                                                                  

Gauge Pressure in Lbs/In 2 (based on atmospheric pressure of 14.7 Lbs/In 2 absolute at sea level) 20 30 40 50 60 70 80 100 120 150 200                                                                               

                                                                              

                                                                              

                                                                                

Density (Weight) in Lbs/Ft                                                                                                                                                                                                                                                    

250

300

3

                                                                                

                                                                                

                                                                                

                                                                                 

                                                                                

                                                                                 

Calculation of Density at Other Tem-  Water Vapor Content of Air in Pounds of Water/100 Ft 3  at Various Temperatures & Relative Humidity   peratures & Pressures  Density at a specific pressure and temperature can be converted to density at another pressure and temperature using the following equation: D2 = D1 T1 x P2 T2 P1 Where: T1 = (°F + 460°) initial condition T2 = (°F + 460°) new condition D1 = density lbs/ft 3 initial condition D2 = density lbs/ft 3 new condition P1 = absolute pressure (psia) initial condition P2 = absolute pressure (psia) new condition

Calculation of Flow or Volume  The same formula can be used to convert air flow or volume at gauge pressure (psig) to standard conditions (atmospheric pressure at 70°F) by substituting cubic feet (ft 3) or cubic feet per minute (CFM) for density (D): Std. CFM = Actual CFM (70 + 460) x (psig + 14.7) (T2 +460) 14.7 psia

I-42

Lbs/100 Ft 3 at Specified Relative Humidity Air (°F) 20% 25% 30% 35% 40% 45% 50% 55% 60% 65% 70% 75% 80% 85%                                                                                                                                                                                                                                            Note — T o c o v e  t “ g a i s o f m o is t u e ” t o p o u d s  m u lt ip l g  a i s b    

90% 95% 100%                            

Technical

Reference Data  Physical & Thermodynamic Properties of Common Gases Properties of Common Gases at Normal Temperatures  Specific Ht. at Constant Press2 (Btu/lb/°F) 0 .3 8 3 2 0 .2 4 0 0 0 .5 2 0 2 0 .1 2 3 3

Density1 (Lbs/Ft3) 0 .0 6 0 .0 7 4 8 0 .0 4 0 .1 0 3 3

Substance  A c e ty le n e  A ir  A m m on ia   A rg on B uta n e -is o B uta ne -n C a rbo n D ioxide C a rbon M ono xide C hlorine Chlorodiuoromethane (F-22)

0 .1 1 4 0 .0 7 2 5 0 .1 8 5 3 0 .2 8

C hloroform C y a no g e n Dichlorodiuoromethane (F-12) E tha ne E thy l C hloride E th y le ne F luorine H e lium H y drog e n H y dro g e n B rom ide H y drog e n C hloride H y drog e n F luoride H y drog e n Io dide Hydrogen Sulde M e tha ne M e th y l C hlorid e M e th y l E th e r M e th y l F luoride N e on N itric O xide N itro g e n N itrou s O xide O xy g e n P hos phine P ropa ne Silicone Tetrauoride S ulfur D iox ide  W a te r V a p o r e n on

0 .3 2 0 .0 8 0 .1 7 0 .0 7 0 .1 0 0 .0 1 0 .0 0 0 .2 2 0 .1 0 0 .0 5 0 .3 5 0 .0 9 0 .0 4 0 .1 4 0 .1 3 0 .0 9 0 .0 5 0 .0 7 0 .0 7 0 .1 2 0 .0 8 0 .0 9 0 .1 2 0 .2 9 0 .1 6 0 .0 3 0 .3 6

0 .2 0 2 5 0 .2 4 2 5 0 .1 1 2 0 .1 5 1 0

59 03 56 75 23 35 46

77

Thermal Conductivity (Btu/in/hr/ft2 /°F) 0 .1 2 0.18 0 .1 5 0.113 0 .0 9 4 0 .0 8 7 0.12 0.18 0 .0 5

0 .1 4 0 .4 0 0 .1 4 0 .3 8 0 .2 7 0 .3 9 0 .1 8 1 .2 5 3 .4 0 0 .0 8 0 .1 9

40 95 10 61 50 90 20 00 90 20 40

0 .0 6 0 .2 4 0 .5 9 0 .2 4

00 51 29 00

0 .0 9 0 .2 1 0 .0 6 4 8

0 .2 3 0 .2 4 0 .2 1 0 .2 1

20 38 26 75

0 .3 2 0 .1 6 5 6 0 .1 8 0 .1 0 5 0.18

-211 -109.3 -340.6 -150.88 -256

Latent Heat Fusion2 (Btu/lb3)

0 .0 9 1 0

0 .1 5 4 4 0 .4 8 2 0

-415.61 -268.6 -345.75 -152.32 -361.12 -208.3 -309.82

0.07 0 .1 7 0

-

.1

W e ig ht in lbs /ft  a t a pp roxim a te ly

.

W he re te m pe ra ture is not g iv e n, 6 °F (2 °C ) is un de rs tood.

.

A ll prop e rtie s a re a t a pre s s ure e qu iv a le nt t o 7

13 64 33 08 S u blim a te s -312.7 -30.46 -41.36 14 3. -6.106 -21.62 53 96 -304.6 -4 5 2 . 0 9 -4 2 3 . 7 5 -91.66 -117.58 -34.06 -32.26 -1 0 7 1 -12.82 -108.4 -243.4 -297.4 -

-104.8

15 7. 16 4. 14 5.

46 4. 16 6.

19 0. .3 23 7. 24 8. 18 4.

17 0. 14 3.

-

.

Latent Heat Vaporization (Btu/lb)

-

-18.22 -277.6 -217.7 -272.92 -369.4 -457.6 -434.45 -124.06 -168.34 -134.14 -60.34 -122.8 -296.5 -154.48 -216.4

0 .0 5 0.13 0 .0 6 1 0 .1 2 3 0 .1 7 6 0 .9 8 8 1.16

Boiling Point (°F) -118.48

19 4.

0 .0 9 7

0 .0 9 72

Melting Point (°F) -114.34

-

F a nd a tm os phe ric pre s s ure 0 m m of m e rcury, u nle s s oth e rw is e indica te d.

Properties of Common Gases at Cryogenic Temperatures  Properties / Gases D e n s it y @ ° F A t m lb / f t   B o i lin g P o in t @ 1 A t m - ° F M e lt in g P o i n t @ 1 A t m - ° F  V a p o r D e ns ity @ B P - lb s /ft  L iquid D e ns ity @ B P - lbs /ft   V a p o r P re s s u re S o lid @ M P in m m H e a t of V a por @ B P - B tu/lb H e a t of F us ion @ M P - B tu/lb Cp @ ° F @ 1 A tm - B tu /lb ° F Cp Cv @ 9 ° F @ 1 A tm C ritica l Te m pe ra ture - F C ritica l P re s s ure @ 1 A tm

N2

02

-320.4 -345.8 0 .2 8 50 19

-297.4 -361.1 0 .2 9 71 29 .0

11.0 0 .2 4

.9 0 .2 1

-232.8

-181.1

He -452 - 8 ( 2 6 A tm 0 .9 9 7 .8 0 < 02 < 03 < 1. 5 °F 5 92 °F -450.2

H2 -434.6 0 .0 8 4.37 19 4. 25.2 3.39 1.41 -399.8 12.8

CH4 -258.7 -299.2 0 .1 1 2 26 47 70.0 24 8. 26.1 0 .5 2 1.31 -1 1 45.8

NH3 -28.03 -107.9 0 .0 5 5 6 42 58 58 8. 15 1. 0 .5 2 27 0. 111.5

A -302.4 -308.7 0 .3 6 86 77

0 .1 2 -188.5 48.0

Ne -410.6 -415.7 0 .5 9 74 91 37.4 .2 0 . 2 5 (Approx) 1.64 -379.7 26.8

I-43

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

Technical

Reference Data  Physical & Thermodynamic Properties of Common Solids P r perties f

Substance  A lu m inu m  A n tim o n y  B a bb itt - T in B a rium B e ry llium B is m ut h B ra s s (Y e llow C a dm ium C a lcium C a rbo n C hrom ium C ob a lt  C opp e r G old IN C O L O Y  8 IN C O N E L  ®  6 Iridium Iro n ( Lead L ithium M a g ne s ium M a ng a ne s e M e rcu ry  M oly bd e num M O N E L ®  4 N ick e l P la tinu m P o ta s s ium R hodium S ilv e r S odium S old e r 50% Sn - 50 Pb S te e l, C a rbo n S te e l, S S Ta nta lum T in Tita nium Ty pe M e ta l 85% Pb - 15 S b Tu ng s te n U ra niu m  V a n a diu m Z inc Z irco nium

eta s (

id)

P r perties f

Thermal Specific Conductivity Melting Density Heat (Btu/  Point (Lb/Ft3) (Btu/lb/°F) in/hr/ft2 /°F) (°F) 0 .2 2 1536 1220 0 .0 5 0 4 1167 0 .0 7 0 .0 6 1562 0 .4 2 2462 0 .0 2 9 4 0 .0 9 ~ 1680 0 .0 5 5 2 0 .1 6 1490 0 .1 6 > 6400 0.111 2940 0 .1 0 0 1 2696 0 .0 9 2 8 2784 1981 1204 0 .0 3 1 2 2352 1945 0 .1 0 2475 0 .1 0 2470 1399 0 .0 3 2 3 4449 0 .1 0 7 5 2795 0 .0 3 0 6 0.79 0 .2 4 1188 1204 0 .1 2 1 1 2300 0 .0 3 3 3 -3 0 .0 6 4748 11 2370 0 .1 0 3 2 2624 1333 0 .0 3 1 9 3224 0 .1 7 0 .0 5 3570 0 .0 5 5 7 2904 1761 0 .2 8 ~ 440

1035

1204

2548 2550 5162

0 .0 3 0 .0 5 4 8 0 .1 1 2 0 .0 3 0 .0 2 0 .1 1 5 0 .0 9 3 1 0 .0 6

3272 ~ 479 1104

Note — W he re te m pe ra ture is not g iv e n, 6 te m pe ra ture is un de rs too d.

I-44

6119 < 3362 3110 3452 F (2

C)

Latent Heat Fusion (Btu/lb) 16 7.

57 2.

Metal  A lu m inu m B is m u th C a d m iu m

115

eta s (L i u id)   Melting Latent Ht. Liquid Point of Fusion Temp. Density (°F) (Btu/lb) (°F) (Lbs/ft3) 1220 14 8. 1292 14 7. 1454 520 21.6 1000 1400 609 23.8

G o ld Lead

Specific Thermal Heat Conductivity (Btu/  (Btu/  Lb/°F) in/hr/ft2 /°F)

0 .0 3 0 .0 3 0 .0 3 0 .0 6 0 .0 6 0 .0 6

, 10.6

0 .0 3 0 .0 3 1300

L ith iu m

357

M a g n e s iu m M e rc u ry

1204 1328 1341 -3 8

P o ta s s iu m 13 1.

S ilv e r S o d iu m

1 76 1

1 1 1 2

3 7 8 0

0 6 3 0

0 1 2 0

0 .3 1 0 .3 2 0 .0 3 0 .0 3 0 .0 3 0 .1 9 0 .1 8 0 .1 8 0 .0 6 0 .0 6 0 .0 6

2 0 1300

S old e r 50 Sn -50 60 Sn -40 T in

0 .0 5 0 .0 5 0 .0 5

Z in c 1112

0 .1 1 7

Technical

Reference Data

Physical & Thermodynamic Properties of Common Solids P r o perties o f N n - eta ic S o ids

Substance

Alumina Aluminum Silicate   (Lava) Asphalt Bakelite Basalt Beeswax Boron Nitride (Comp.) Brick, Building Carbon, Powder Graphite, Solid Graphite, Powder   Diamond Cellulose (Pulp) Chalk Charcoal (Oak) Clay Coal (Anthracite) Coke Concrete, Sand Concrete, Cinder Cordierite Cork (Granulated) Earth (42% H2O) Earth (Dry, Packed) Earth (Dry, Stony) Fiberglas® (Insul.) Fiberglas® (Insul.) Firebrick (Clay) Fosterite Fused Silica (Quartz) Glass   Normal   Crown Flint (Leaded)   Pyrex Granite Ice -0°C (32°F) Limestone

Density  (Lbs/Ft 

Speci c Heat  (Btu/lb/°F 20 °C 68°F

P r o perties o f No n - eta ic S o ids   Thermal Conductivity  (Btu/in/ hr/ft / ° F )

20 5

Melting Point  (°F)

23 1

0.19

—

13 0 81 81 18 4 60 13 0 12 3 13 1 14 0 13 0 21 9 3.4 14 3 33 115 97 75 14 4 97 13 8 5.4 10 8 95 12 7 0.75 3 112 17 4 13 7

0.25 0.4 0.35 0.2 — 0.32 0.22 0.168 0.165 0.165 0.16 0.35 0.215 0.2 0.22 0.3 0.36 0.22 0.21 0.35 0.485 0.9 0.42 0.44 — — 0.198 0.23 0.31

9 5.2 116 — — 15 0 4.8 2.4 1044 1.27 15840 0.32 5.76 0.36 9 1.18 6.6 12.6 4.92 23 0.336 7.44 0.9 3.6 0.29 0.22 6.96 26 9.96

— 25 0 — — 14 4 — — 6400 — — — — — — — — — — — — — — — — — — — — —

13 9 15 4 20 0 13 9 15 9 57.5 15 3

0.199 0.161 0.117 0.20 0.192 0.465 0.217

7.08 7.08 9.48 7.08 13 - 28 15.6 6.48

2200 — — — — 32 —

Substance

Magnesia 85% (Insul.) Magnesium Oxide Marble Mica Paper Plastics ABS Cellulose Acetate Epoxy (Resin) Fluoroplastic (PTFE)   Nylon   Phenolic   Polyethylene   Polystyrene Polystyrene (Exp.)   Polypropylene Polyurethane (Exp.)   Polyvinyl Parafn Porcelain Pyroceram Quartz Rigid Insulation Fiber Board Inorganic Bonded Rock Salt Rubber Soft Rubber, Hard Sand Silicon Sodium Carbonate Sodium Chloride Sodium Cyanide Sodium Nitrate Sodium Nitrite Steatite Sugar Sulfur Woods (Average) Oak, Red Pine, White

Density  (Lbs/Ft 

12 13 5 17 0 16 5 58 62.2 82.9 71.8 13 3 69.1 82.9 57 64.8 1.7 56.7 1.5 86.4 56 14 5 16 3 13 8 14.8 10 - 15 13 6 68.6 74.3 94 14 5 13 5 13 5 94 14 1 13 5 15 8 10 5 12 9 23 - 70 42 25

Speci c Heat  (Btu/lb/°F 20 °C 68°F

Thermal Conductivity  Melting (Btu/in/ Point  hr/ft / ° F ) (°F)

0.222 0.25 0.21 0.206 0.32

4.2 17.6 18 3 0.9

— — — — —

0.3 - 0.4 0.3 - 0.42 0.4 - 0.5 0.25 0.4 0.35 0.55 0.32 0.29 0.45 0.38 0.2 - 0.3 0.69 0.26 0.233 0.17

1.56 2.28 1.2 - 3.5 1.68 1.2 0.097 - 0.3 2.28 0.7 - 1.08 0.252 1.21 - 1.36 0.228 0.84 - 1.20 1.68 15.6 23.4 27.6

— — — — — — — — — — — — 13 3 — — 3150

0.28 0.45 — 0.48 0.96 0.48 1.104 0.195 2.25 0.181 — 0.30 — 0.22 — 0.3 — 0.29 — 0.3 — 0.2 23.2 0.3 — 0.181 1.8 0.45 - 0.67 0.78 - 1.78 0.57 1.188 0.67 0.72

1472

0.21

— — — 2577 1546 1440 1015 55 5 49 0 — 16 0 — — — —

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

I- 4

Technical

Re ere e ata 

q iva e ts C versio s 

Temperat ure Equi valents ( °F and °C ) C -5 -4 -4 -3 -3 -2 -2 -1 -1 -5

F -5 -4 -4 -3 -2 -1 -4 -5

C

F

C

F

C

F

F

C

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

1004 1013 1022 1031 1040 1049 1058 1067 1076 1085 1094 1103 1112 1121 1130 1139 1148 1157 1166 1175 1184 1193 1202 1211 1220 1229 1238

Values for Interpolati on i n Above Table   1°C = 1.8°F 2°C = 3.6°F 3°C = 5.4°F 4°C = 7.2°F 5°C = 9°F

C

6°C = 10.8°F 7°C = 12.6°F 8°C = 14.4°F 9°C = 16.2°F

2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4 4

F 47 56 65 74 83 92 01 10 19 28 37 46 55 64 73 82 91 00 09 18 27 36 45 54 63 72 81 90 99

C

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

5 5 5 5 5 5 5 5 5 5 5 6 6 6 6 6 6 6 6 6 6 6 7 7 7 7 7 7 7

F 0 1 2 3 4 5 6 7 8 8 9 0 1 2 3 4 5 6 7 7 8 9 0 1 2 3 4 5 6

C

8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0

10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 11 11

0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 0 0

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2

0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5

7 7 7 7 8 8 8 8 8 8 8 8 8 8 8 9 9 9 9 9 9 9 9 9 9 9 0 0 0

F 69 78 87 96 05 14 23 32 41 50 59 68 77 86 95 04 13 22 31 40 49 58 67 76 85 94 03 12 21

F or mula for Conver ti ng Temperature Scales

1°F = 0.55°C 2°F = 1.11°C 3°F = 1.66°C 4°F = 2.22°C 5°F = 2.77°C

6°F = 3.33°C 7°F = 3.88°C 8°F = 4.44°C 9°F = 5°C

Fahrenheit to Celsius Celsius to Fahrenheit Fahrenheit to Rankine (absolute) Celsius to Kelvin (absolute)

°F = 1.8°C + 32 °C = 5/9 x (°F - 32) °R = °F + 460 °K = °C + 273

Note — All decimals are exact. All decimals are repeating decimals.

Pressure E qui val ents U nit

1 1 1 1 1

lbs /in g / cm A tm os phe re (a tm Bar P a s ca l (N /m 2

1 m m H g . (0 °C ) 1 in . H g . ( 3 ° F ) 1 f t. H 0 °F 0 ft H 0 °F

L bs In

Kg/cm

 A tm

0 .0 7 0 3 14 14 14 14

22 69 50 5 x 10

0 .0 1 9 3 4 0 .4 9 1 2 0 .4 3 3 1 43 31

-5

1 .0 3 3 3 1 .0 1 9 7 1 1 .0 3 x 1 0 1 .3 5 0 .0 3 0 .0 3 3 .0 4

9 51 4 53 0 45 48

0 .0 6 8 0 4 0 .9 6 7 8 -5

0 .9 8 6 9 1 x 1 0 -5 0 .1 3 0 .0 3 0 .0 2 2 .9 4

Notes —  A . 1 in c h o f H g M e rc u ry ) = .6 in c h e s o f w a te r. B . 1 poun d pe r s qua re inch (ps i) = .3 1 fe e t of w a te r C . 1 f o o t o f w a t e r = . 4 1 p o u n d s p e r s q u a re i n c h ( p s i) .

I- 4

16 342 947 69

Ba r

P a s ca ls

0 .0 6 8 9 5 0 .9 8 0 6 6 1 .0 1 3 2 5 1 x 10

6 ,8 9 9 8 ,0 6 1 0 1 ,3 2 1 x 10

-5

0 .1 3 0 .0 3 0 .0 2 2 .9 8

33 3 86 9 86 59

1 3 ,3 3 3 ,3 8 2 ,9 8 2 9 8 ,7 0

mm Hg. (0°C)

51 71 7 3 5 .5 6 7 5 0 .0 6 5 x

2 .0 3 28 96 29 92 29 53 0 .0 0 0 2 9 0 .0 3 9 3 7

22 39 22 39

Ft H O (60°F)

In. Hg (32°F)

0 .8 8 1 7 5 88 17

2 32 33 33 0

.3 0 8 6 84 92 49 .0 0 0 3 3

0 .0 4 4 6 5 1 .1 3 4 2

Technical

Reference Data  Engineering Constants & Conversions C ommon Conversion Factors

C ommon Conversion Fa ctors Multiply To Convert Units By  A tm os ph e res a tm 1 0133  A tm o s ph e re s a tm 29 92 B ar 0 9869 B ar 14 504 B ritis h the rm a l u nit  B tu 1 ,0 5 B ritis h the rm a l u nit  B tu 0 00029 B ritis h the rm a l u nit  B tu 0 2931 B ritis h the rm a l u nit  B tu 0 252 B rit th e r un its /hr B tuh 0 2931 B rit th e r un its /hr B tuh 0 2931 B rit th e r un its /hr B tuh 0 00029 B rit th e r un its B tu/in/h 0 1442  inch/ho ur/s qft/° F ft  /° F C a lo rie s ca l 4 C e n tim e te r cm 0 03281 C e n tim e te r cm 0 3937 C e n tim e te rs /s e con d cm /s 1 969  3 C ub ic c e ntim e te r cm 0 061 C ub ic fe e t  ft  62 43 C ub ic fe e t  ft  28 32 C ub ic fe e t  ft  0 02832 C ub ic fe e t  ft  7 481 C ub ic fe e t  ft  28 32 C ub ic fe e t/m inut e c fm 1 699 C ub ic fe e t/m inut e te rm 0 00047 C ub ic fe e t/m inut e c fm 0 4719 C ubic inch in 16 39 C ub ic m e te r m 3 35 32 C ub ic m e te r m 3 264 2 C ub ic m e te r m 3 1 ,0 0 C u bic m e te rs /hr m 3 /h 0 5885 C u bic m e te rs /hr m 3 /h 4 403 C u bic m e te rs /s e c m 3 /s 2,119 F e e t  ft  30 48 F e e t  ft  0 3048 F e e t/m inu te fp m 0 508 F e e t/m inu te fp m 0 00508 G a llon, Im pe ria l 1 201 G a llon, U S gal G a llon, U S gal 0 1337 G a llon, U S gal 8 337 G a llon, U S gal 0 8327 G a llon, U S gal 3 785 G a llon, U S gal 0 00378 G a llons /m inute g pm 0 2271 G a llons /m inute g pm 0 06309 G ra m s g 0 03527 G ra m s g 0 00220 G ra m s /cu ce nt im e te r g /cm 3 1 ,0 0 G ra m s /cu ce nt im e te r g /cm 3 62 43 G ra m s /cu ce nt im e te r g /cm 3 0 03613 H ors e po w e r hp 0 7457 H ors e po w e r hp 2 ,5 4 H ors e po w e r h p 3 3 ,0 0 H ors e pow e r, bo ile r bhp 9 803 H ors e pow e r, bo ile r bhp 3 ,3 5 Inche s in 2 Inche s in 5 Inc he s M e rcury  in H g 0 03342 Inc he s M e rcury  in H g 0 03937

To Obtain Units B ar Inc he s M e rcury  in H g  A tm o s ph e re s a tm P ound s /s qu a re inch ps i  J o u le s  J 3 1 K ilow a tts W   W a tts  W  K iloc a lorie s cal  J o u le s /s e co nd  J /s  W a tt/ h o u rs  W h 3 1 K ilow a tt/ho urs Wh  W a tts /m e te r/° C  W / m /° C

2

5

4 5

J ou le s  J F e e t  ft  Inch e s in F e e t/m inu te fp m C ubic inche s in P ound s of w a te r lb C ub ic c e nt im e te rs c m 3 C u bic m e te rs m 3 G a llon s , U S gal L ite rs l C ub ic m e te rs /ho ur m 3 /h C u bic m e te rs /s e c m 3 /s L ite rs /s e co nd l/s C ub ic c e ntim e te rs c m 3 C ub ic fe e t  ft  G a llon s , U S gal L ite rs l C ub ic fe e t/m in cfm G a llons /m in g pm C ub ic fe e t/m in cfm C e n tim e te rs cm M e te rs m C e ntim e te rs /s e c cm /s M e te rs /s e c m /s G a llon s , U S gal C ubic inche s in C ub ic fe e t  ft  P ound s of w a te r lb G a llon Im pe ria l L ite rs l C u bic m e te rs m 3 C u bic m e te rs /h r m 3 /h L ite rs /s e c l/s O unc e s oz P ounds lb K ilog ra m s /c u m e te r g / m 3 P ounds /cubic fo ot  lb/ft  P ounds /cubic inch lb/in K ilow a tts W  B ritis h t he rm a l u nits B tu F oot -lbs /m in ft-lb/m in K ilow a tts W  B ritis h t he r un its /hr B tuh C e n tim e te rs cm M illim e te rs mm  A tm o s ph e re s a tm Torr

To Convert Units  J o u le s  J  J o ul e s  J  J o ul e s  J  J o ul e s /s e co n d  J /s K iloca lorie s /hou r k ca l h K ilo g ra m s g K ilo /cu bic m e te r g / m 3 K ilo /cu bic m e te r g / m 3 K ilog ra m s /s q c m g / c m 2 K ilojoule J K ilom e te rs /ho ur kmh K ilopa s ca l k Pa K ilow a tt/h ou rs Wh K ilow a tt  W  L ite r l L ite r l L ite r l L ite rs /s e co nd l/s L ite rs /s e co nd l/s M e te r m M e te r m M e te rs /s e co nd m /s M ile s /h ou r m ph M illilite r ml M illim e te r mm N e w ton s /s q m e te r N /m  2 O unce oz P ound lb P ound lb P ounds /cubic fo ot  lb/ft  P ounds /cubic fo ot  lb/ft  P ounds /cubic inch lb/in P oun ds /s qu a re inc h ps i P oun ds /s qu a re inc h ps i P oun ds /s qu a re inc h ps i P oun ds /s qu a re inc h ps i P oun ds /s qu a re inc h ps i P oun ds /s qu a re inc h ps i S q ua re ce ntim e te rs cm  2 S q ua re ce ntim e te rs cm  2 S qu a re fe e t  ft  S qu a re fe e t  ft  S qua re inch e s in S q ua re m e te rs m 2 Torr Torr  W a tt- ho u rs  W h  W a tt- ho u rs  W h  W a tt- ho u rs  W h  W a tt- ho u rs  W h  W a tts  W   W a tts  W   W a tts  W   W a tts /m e te r/° C  W / m /° C  W a tts /s q c e nt im e te r  W / cm  2  W a tts /s q u a re in c h  W / in a rd s  y d

Multiply By 0 000948 0 2388 0 0002778 3 2 0 0 14 0 0 0 3 ,4 1 3 ,4 1 0 0 0 2 15 3 39 196 1

45

1 2

5

0 0 8 3 0 0 6 7 0 0 0 6 6 1 0 0

0 6 10 0 5 3 ,6 0 3 3 0

96 205 001 06243 22 631 145

03532 001 2642 119 85 281 37 9 609 03937

6 4 0 0 6 0 0 0 8 8 7 0 1

5 1 2 8 6 6 7 9 9 1 0 5

0 4 7 0

929 52 6 01316

36 602

805 895 031 5 5 1076 5

412 001

3 412 0 001 6 934 6 452 0 155 0

To Obtain Units B ritis h th e rm a l un it  B tu C a lo rie s ca l  W a tt/ h rs  W h  W a tts  W  B ritis h th e r u n its h r B tuh P ound s lb G ra m s /cu ce nt im e te r g /cm 3 P ounds /cubic fo ot  lb/ft  P ound s /s qua re inc h ps i W a tt h rs  W h M ile s h r m ph P o un d s s q ua re in c h ps i B ritis h t he r un its /h r B tuh B ritis h th e rm a l un its B tu C ub ic fe e t  ft  C u bic m e te rs m 3 G a llon , U S gal C ubic fe e t/m in cfm G a llons /m in g pm F e e t  ft  Inche s in F e e t/m in fpm K ilo m e te rs h r m /h C u bic ce ntim e te rs c m 3 Inche s in P o un ds s q ua re in ch ps i G ra m s g G ra m s g K ilog ra m s g G ra m s /cu ce nt im e te r g /cm 3 K ilog ra m s /c u m e te r g / m 3 G ra m s /cu ce nt im e te r g /cm 3  A tm o s ph e re s a tm B ar K ilog ra m s /s q c m g / c m 2 K ilopa s ca ls P a  N e w ton s /s q m e te r N /m  2 Torr S qu a re fe e t  ft  S qua re inche s in S qu a re ce ntim e te rs c m 2 S q ua re m e te rs m 2 S qu a re ce ntim e te rs c m 2 S qu a re fe e t  ft   A tm o s ph e re s a tm Inc he s M e rcury  in H g  J o u le s  J B ritis h t he r un its /h r B tuh K ilojou le s J K ilow a tt-h ou rs Wh  J o u le s /s e co n d  J /s B ritis h th e rm a l un its B tu K ilow a tts W  B ritis h t he r un its inch/hour/ s qft/° F B tu/in /hr/ft /° F  W a tts /s q u a re in ch  W / in  W a tts /s q ce n tim e te r W / c m 2 M e te rs m

I-47

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

Technical

Re ere e ata  C rr sio n

ide r E e tric Immersio n Heaters 

Corrosion Guide

Terminal Enclosures

The Corrosion Guide on the following pages provides suggested sheath materials for many applications. While it is by no means complete, the guide does include all of the readily available sheath materials and a wide variety of common chemicals and solutions. The compilation is based on available data and application experience and is furnished as a guide to the user. The recommendations are only suggestions and should not be interpreted as an absolute choice of sheath material in a particular application.

Corrosion of electric immersion heaters is not limited to the sheath material. Frequently, application problems are related to contamination or corrosion of heater terminals and electrical connections. When selecting a heating element sheath material, also consider the location and environment of the terminal enclosure. Select an appropriate heater electrical terminal enclosure.

Types of Corrosion In immersion heater applications, a protective or “passive” film forms on the surface of a metal sheath which protects it from further corrosion. As long as the film remains intact, the base metal is protected. Corrosion mechanisms destroy the protective film and allow the base metal to be attacked. Sheath corrosion takes a number of different forms. The most common are: General Corrosion Galvanic Corrosion Stress Corrosion Cracking Intergranular Corrosion. Temperature accelerates the corrosion process. Austenitic stainless steels are particularly susceptible to stress corrosion cracking and intergranular corrosion.

Sheath Selection Process Since it is the responsibility of the end user to make the final selection of sheath material for any particular application, the information in this guide may be used as a reference in the investigation of a particular process. Select the sheath material and watt density based upon your intimate knowledge of the chemicals and operating conditions which exist in the actual application. As part of the analysis, you should consider the anticipated operating temperatures, the recommendations of the chemical supplier and actual test results where available. Contact your Local Chromalox Sales office for assistance or sheath material recommendations for chemicals and solutions not shown in this list.

I- 4

 Av oid  galvanic corrosion. Avoid contact

of the element sheath with dissimilar metals. K e e p  immersion heaters out of the space

between anode and cathode in electroplating processes. The effects of plating current may damage the element sheath. Examine  immersion heaters periodically

for corrosion and sludge accumulation. Take corrective action to maintain continuity of operation.

Temperat ures & Watt D ensit ies Consider your selection of a heater sheath material very carefully. Once the material has been selected, design the application for sheath watt densities as low as practical and economical. Remember, the sheath of an immersion heater functions as a heat transfer surface and thus operates at temperatures above the temperature of the surrounding media. The higher the watt density, the higher the sheath temperature. The elevated media temperatures and the fluid movement around the sheath accelerate chemical reactions and may create severe localized corrosive conditions on the metal surface. Materials recommended for construction of your tank or vessel may not be suitable as the sheath material for the immersion heater.

Operating & Maintenance Factors for M aximum Heater Li fe Sheath selection is only part of the solution to resolving potential corrosion problems. The ultimate life of a heating element sheath in a particular application will also depend upon a number of operating and maintenance factors. These factors are usually within control of the end user. To ensure maximum heater life and minimize sheath corrosion, Chromalox recommends the user: Maintain  the chemistry of the solution.

Avoid carry-over from other processes.  Av oid  depletion of bath chemistry.

Maintain bath chemistry at optimum levels. Filter or remove accumulating sludge,

since sludge impedes flow of heat from element sheath and accelerates corrosion. K e e p  process temperatures stable and

as low as possible. Excessive operating temperatures mean shorter heater life.

Electrically G round  metal sheath heaters

to the tank and, in turn, to earth for safety and protection of personnel against electrical shock. Consider the use of a ground fault circuit interrupter (GFCI) for optimum safety.

Table Legend to the Corrosion Guide  A 

= Good to Excellent service life

B

= Fair to Good service life, expect some sheath corrosion

C

= Depends on Conditions such as solution concentration, operating temperature and fluid flow = Not Suitable or Not Recommended

Blank  = Data Incomplete or Not Available  W A R N IN G  — Hazard of Electric Shock Any

installation involving electric heaters must be effectively grounded in accordance with the National Electrical Code to eliminate shock hazard. All electrical wiring to electric heaters must be installed in accordance with the National Electrical code or local electrical codes by a qualified person. For maximum equipment protection, the National Electrical Code recommends Ground Fault Protection be provided for each branch circuit supplying electric heating equipment.

Warra nty D isclai mer Ma ny factors that a ffect the corrosion of heater sheath m aterial are beyond the control of the he ater m anufacturer. F or this reason, Chromalox ass umes no responsibility for any e lectric Imm ersion heate r failure that can be attributed to corrosion. This is in lieu of any warranties, written or verbal, relative to heater performa nce in a corrosive environment.

Technical

Reference Data Corrosion Guide for Electric Immersion Heaters (cont’d.) Legend

Sheath Material

B = Fair to Good C = Depends on Conditions X = N o t S u i ta b le Blank  = Data Not Available

Solution Acetic Acid (100%) Acetic Acid (50%) Acetone (100%) Actane 70™ Actane 80™ Actane Salt™ Alcoa Bright Dip R5™ Allyl Alcohol Alcohol Alcorite™ Alkaline Cleaners Alkaline Soaking Cleaners Alodine™ Aluminum (Molten) Aluminum Bright Dip Aluminum Chloride (Aqueous) Aluminum Cleaners Aluminum Sulphate (Sat.) Alum Ammonia (Anhydrous) Ammonia (Gas) Ammonium Biuoride Ammonium Chloride (50%) Ammonium Hydroxide (25%) Ammonium Nitrate Ammonium Persulphate Ammonium Sulphate (< 40%) Amyl Alcohol Aniline Anodizing ARP 28™ ARP 80™ Blackening Salt Arsenic Acid Asphalt Barium Hydroxide (Sat.) Barium Sulphate Beer Black Nickel Black Oxide Black Liquor Bleach 5.5% Cl, Clorox™ Bonderizing™ Boric Acid Brass Cyanide Bright Nickel Brine (Salt Water) Bronze Plating Butyl Alcohol (Butanol) Cadmium Black Cadmium Fluoborate Cadmium Plating Calcium Chlorate

   0    0    8

  m   u   n    i   m   u    l    A

   l   e   e   t    S   n   o    b   r   a    C

   0    0    6    ®    L   n   o   r   r    E   e    N    I   p   t    O   p   s   o    C   a    C    N    C    I

   0    0    4    ®    ®    O    L    L    E    d    O    N   a    C   e    N    L    O    I    M

X C A

X X BC

X X A

B B A

 A  = Good to Excellent 

X X X

C X A

X X B

BC B A

   S    S    7    4    3  ,    1    2    3  ,    4    0    3

 

  y   o    l    l   e   t    S    S   s   a    S    H     S    3    b    7    6    C    6    1    3    0    2    2    C    ®

Corrosion Rating BC BC A A C A AC BC B B BC A

   2    1   m   u   z    i   t   n    ®  n   r   o   a   a   t   e   u    i    T    T

A A A

A A A

A B A A

B A

A A A A A

   2    1   t   y   s   t   e    i   s   g   n   g   e   u    S   D

Notes 

23 15 2 1 1

CONTACT FACTORY B B

B   A B A

A A B   A

B A

A A

A A

A B

A A

B A

B B

B

A A A X

B

23 - 26 30 - 40 30 - 40

1 2 2 1 1 1

CONTACT FACTORY CONTACT FACTORY X X X X C X X X B B B X C B X X X X B A

X C X X A C X X BC A X X A C X X A B C X

X X X X X X X X X X X X A X X C X X B B

X X

X X

X

X

X

C

X BC

X A BC

C C X X X X X X A X X X B B X X A B B

X

BC A

A

X A X BC A B X A A X C B B B X X A B B A

C

X A BC BC C C X C A BC C A B B X B A B AC B

X X B X C C X X X X C B B B A X X X B X  

X A X X A X B A X X X B BC B X X X C B A

X X A A BC BC X BC B   A A A X B C C A A A A C B C B B B A A X X B BC B B AC

B B B B A

A BC BC BC BC BC SEE ZINC PHOSPHATE C BC BC BC A A

AC

AC

A

A

B A

A

C A A

B

A BC

C A B B BC BC BC A A B   A AC B B A B A A B B B B B B A A A B A B B A BC

A A A A A A A

B B A A A A X A A C A A A X X A AC A B

C AC

C   A

A A A A A A A A A A A A A A A A A A A A A A

A

A

A

A

A

B

A A

B

B

X

B

B

B

C

BC

B

B

B

23 - 26

2 1 1

6 - 10

2

55 30 - 40 23 23 15 15 - 23

5 5

A 23 55 A A

B

1, 9 1 1 1 1

A A

A

B A

C B B B A

A A X A A A A X B X A A A A A A

1 1, 5 10, 11 1 2 1 1

A

See notes at end of table.

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

I-49 

Technical

Reference Data Corrosion Guide for Electric Immersion Heaters (cont’d.) L e g e nd  A  = Good to Excellent 

B = Fair to Good  C = Depe nds on Conditions  X = Not Suitable  Blank  = Data Not Available  S o lu t io n Calcium Chloride (Sat.) Carbon Dioxide - Dry Gas Carbon Dioxide - Wet Gas Carbon Tetrachloride Carbonic Acid (Phenol) Castor Oil Caustic Etch Caustic Soda Chlorine Gas - Dry Chlorine Gas - Wet Chloroacetic Acid Chromic Acetate Chromic Acid (40%) Chromic Anodizing Chromylite Citric Acid (Conc.) Clear Chromate Cobalt Nickel Cod Liver Oil Copper Acid Copper Bright Copper Bright Acid Copper Chloride Copper Cyanide Copper Fluoborate Copper Nitrate Copper Pyrophosphate Copper Strike Copper Sulphate Creosote Cresylic Acid 50% Deionized Water Deoxidizer (Etching) Deoxidizer (3AL-13 Non-Chrome) Detergents Dichromic Seal Diethylene Glycol Diversey-DS9333™ Diversey-511™ Diversey-514™ Dowtherm™ (Diphenyl) Dur-Nu™ Electro Cleaner Electropolishing Electroless Nickel Electroless Tin (Acid) Electroless Tin (Alkaline) Enthone Acid - 80 Ethers, General Ethyl Chloride Ethylene Glycol Fatty Acids Ferric Chloride Ferric Nitrate (< 50%) Ferric Sulphate Fluoborate Fluoboric Acid Fluorine Gas (Dry) Formaldehyde (< 50%)

See notes at end of table.

I- 5

S he a th M a te ria l    S    S     l    e    e    m    t    u    S    n    n    i    o    m     b    u    r     l    a    A    C

   r    e    p    p    o    C

   n    o    r    I    t    s    a    C

   L    E    N    O    C    N    I

BC A  A  X B BC X

B B X C B A A 

B BC X AC X AC C

B B X X C A A

B A A A A A A

X X X

C X X

C X X

X X X

B X C

X

X

X

X

X

X

X

X

X

   S    S

 ,    O    L    O    C    N    I

    d    a    e    L

   L    E    N    O    M

 ,

   S    S

B

AC

A

A

B X

X B

   z    t    r    a    u    Q

   m    u    i    n    a    t    i     T

A A B AC A A BC

A A A  A A A X

A AC BC A A A   A 

B BC AC

A  A  A A  A A  A  A A A 

      b    C

   C

C o rro s io n R a t in g B X B BC B B   A  A A A B   A B B B A  A  A  A AC A A A A AC AC A A A X B A A A   BC A X   A A  A A A   SEE SODIUM HYDROXIDE X C BC B A  AC X X C X X X C X C X X C  

X

   y    o     l     l    e    t    s    a    H

BC

B

BC

BC

A A

A

A

A

A

B A

   t    s   y    e   t    i    g   s    g   n    u   e    S   D

   n    o    e     T

23     10 - 23 10 - 23   23 - 26   23 - 26 15 - 26

A A A  A A

X X A

B B A  

A 

X

A A 

A

 

23 - 26

  A 

A 

X

X X

X A 

X

X

X

X

X C C

A X A  BC

X BC

A X A  C

X BC B X BC B C

B B B BC B B C

X

X X B X

X B B A A  A  A  X B X B B X X B SEE WATER

X B B A

A A  A A

A  B A A

B   A

A

X B B A 

B A

A  A A

A AC

C

A 

B

B

A 

B

X AC

B

X

A 

C

X A 

B

B

A 

B

1 1 B B A 

B B B

B B B

A A A 

A A  B

A 

6 - 15 A 

A

AC

A 

B

A

A

A  A A  A 

A

A

A

A

A 

  40 - 55

23 23

  A

A 

A  A A

A

A 

A

B B A A  X X X

B B A  X X X X

B B B C X X C

X AC B

AC X X

X X B

B B B X X X X X X

B A B B C X C A  B

A  A  A  AC X BC C

C B

B B X X X B

B B B B X X C

A A  A A B   A BC A X X BC B BC A C

C X

B A B

BC AC AC

AC A AC

A  A 

A 

B A  A A X A  A

B B A A BC BC A

AC A   A 

A  BC B

A  A A A A A A A

C A

2 2 1 1

A  A 

1 1 1 1 1, 6 1 1 1 1

A  A   A  A 

A 

BC

2 1 1 1 6 2

1

A

X X

Notes

B A A A A AC A X X A

A  A  A  A A A  A A A  A  C A 

  23 - 30   23 - 26

1 1 1 1, 5 1 5 1,5 1 1 1 1 1 1 2 2 5

   

1

Technical

Reference Data Corrosion Guide for Electric Immersion Heaters (cont’d.) Legend

Sheath Material

 A  = Good to Excellent  B = Fair to Good C = Depends on Conditions X = N o t S u it a ble Blank  = Data Not Available S o lu t io n Formic Acid (10 - 85%) Freon (F-11, F-12, F-22) Fruit Juices (Pulp) Fuel Oil (Normal) Fuel Oil (Acid) Gasohol Gasolene (Rened) Gasolene (Sour) Glycerin (Glycerol) Grey Nickel Hydrocarbons-Aliphatic Hydrocarbons-Aromatic Hydrochloric Acid (Dilute) Hydrochloric Acid (50%) Hydrocyanic Acid (10%) Hydrouoric Acid (Dilute) Hydrogen Peroxide (90%) Indium Iridite™ - #4 - 75, #4 - 73, #14, #14 - 2, #14 - 9, #18 - P Iridite™ - #1, #2, #3, #4-C, #4PC&S, #4P-4, #4-80, #4L-1, #4-2, #4-2A, #4-2P, #5P-1, #7, #7-P, #8, #8-P, #8-2, #12-P, #15, #17P, #18P Iridite™ Dyes - #12L-2, #40, #80 Irilac™ Iron Fluoborate Iron Phosphate (Parkerizing™) Isoprep™ Deoxidizer #187, #188 Isoprep™ Cleaner #186 Isoprep™ #191 Acid Salts Jetal™ Jet Fuel JP-4 Kerosene Lacquer Solvents Lead Acetate Lead Acid Salts Lime Saturated Water Linseed Oil Lubricating Oil Machine Oil Magnesium Chloride Magnesium Hydroxide Magnesium Nitrate Magnesium Sulfate McDermid™ #629 Mercuric Chloride Mercury Methyl Alcohol (Methanol) Methyl Bromide Methyl Chloride Methylene Chloride Milk Mineral Oil

  m   u   n    i   m   u    l    A

   l   e   e   t    S   n   o    b   r   a    C

   0    0    6    ®    L   n   o   r   r    E   e    N    I   p   t    O   p   s    C   o   a    C    C    N    I

B B B B X B B X A 

X C X A  X B B B B

C B B X B B X A 

A A X X B X A 

A A X X B X X

A A X X X X X

X

   0    0    8

   0    0    4    ®    ®    O    L    L    E    d    O    N   a    C    O   e    N    I    L    M

B C B

B A B B C B B C A

B A A A  C B B C A 

A A X X X X X

A A BC X B BC B

A A BC X B X B

A  X

X A

B

B A A  B C B B X A

X X X B X

A A BC X B C B

   S    S    7    4    3  ,    1    2    3  ,    4    0    3

 

  y   o    l    l   e   t    S    S   s   a    S    H     S    3    b    6    7    6    C    1    0    3    2    2    C    ®

C o rro s io n R a t in g AC A A B A A A   B BC B BC A  A A A  B A C B B B B B B B B B B B B B A A A A A A X X B X AC

A A X X B X AC

A A X X B B AC

A A AC BC A  A

   2    2    1    1   t   m   y   s    ®   t   u   z   e    i    i   t   n   r   s   g   n   o   a   g   a   t   e   u  n   u    i   e    T    T    S   D

A 

C

A 

B

A A  A 

A 

A  A A A A A A   A   B B X X A X X B A   A

A  A   A 

A  A  A  A 

3-9 30 - 40 6 - 15 6 - 10 23 - 26 23 23

Notes 

2, 3, 7 2, 3, 7 2, 5 2, 3, 5

23 23 - 26 23 - 26 20 - 30 15 - 25

1, 5 2 2

23 23 - 26

5 1

A 

A 

1

A 

X X

X

X X

X A 

X BC

B B

X

X X

X B

X B

A  A  A 

X B

B

B A

B

A  A A A  A A A

A AC

A  A  

1 1 1 1

A  A  A  A 

A

1 1 1 1

A 

B B A X

B B A X

X B B B B   A A X BC B A  B B B BC X X C X X C A  B

X A  B C X BC B B

BC A X B B A B B B BC X X B B B C C B

A  B A 

B B A  X

B B A A A  A  B AC

B A  A A B B A  B

X B B B A   B A   B X B X B X B A  B

X B A B B B A A

X A  A  B C B A  AC

A  B A   B X A

B A A X B B B

X A  B C C BC

X X B B C B X B

B B B B

A  BC B A B B B A B B C A B B

X X A B A  B B BC B AC AC B C   A A AC

B B A B

BC B A B

A  A B B B A B B

B A A 

A B

B

A  A A

A A

23 - 26 23 - 26

 

2 2

A 

1 A 

B B B   A A A B B B B

B BC B A A A B B   A A A B AC A  A B   AC A A A   B AC

X A A A A A A  A  A  A  A A A A A A

C A A  A  A A B B

23 - 40 10   - 15 23 - 26 23 - 26

2 7 7

A   A    A  A 

1 B A A A A A A

A  A   23 - 30 A   A   A  A   30 - 40 A   23 - 26

2

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

See notes at end of table.

I-51 

Technical

Reference Data Corrosion Guide for Electric Immersion Heaters (cont’d.) Legend

Sheath Material

 A  = Good to Excellent  B = Fair to Good C = Depends on Conditions X = N o t S u i ta b le Blank  = Data Not Available

  m   u   n    i   m   u    l    A

   l   e   e   t    S   n   o    b   r   a    C

   0    0    6    ®   n    E   o    L   r   r   e    N    I   p   t    O   p   s   o    C   a    C    N    C    I

   0    0    8

   0    0    ®    4    ®    O    L    L    E    d    O    N   a    C   e    O    N    I    L    M

S o lu t io n

Muriatic Acid Naphtha Nickel Acetate Nickel Chloride Nickel Plate-Bright Nickel Plate-Dull Nickel Plate - Watts Solution Nickel Sulphate Nickel Copper Strike Nitric Acid (20%) Nitric & Hydrochloric Acid Nitric & 6% Phosphoric Acid Nitric & Sodium Chromate Nitric & Sulfuric Acid (50% - 50%) Nitrobenzene Oakite™ #67 Oleic Acid Olive Oil Oxalic Acid (50%) Paint Stripper (High Alkaline) Paint Stripper (Solvent)

P araf Parkerizing™ Peanut Oil Perchloroethylene P et rol e m O il s (R e ed  Petroleum Oils (Sour) Phenol (Carbolic Acid) Phosphates (Generic) Phosphate Cleaners Phosphatizing Phosphoric Acid (25% - 50%) Picric Acid Plating Solutions - Brass Plating Solutions - Cadmium Plating Solutions - Chrome (25%) Plating Solutions - Chrome (40%) Plating Solutions - Cobalt Plating Solutions - Copper Plating Solutions - Gold (Cyanide) Plating Solutions - Gold (Acid) Plating Solutions - Nickel Plating Solutions - Silver Plating Solutions - Tin Plating Solutions - Tin-Nickel Plating Solutions - Tin-Alkaline Plating Solutions - Zinc Plating Solutions - Zinc Acid Plating Solutions - Zinc Cyanide Potassium Aluminum Sulphate Potassium Bichromate Potassium Chloride (30%) Potassium Cyanide (30%) Potassium - Hydrochloric Solution Potassium Hydroxide (27%) Potassium Nitrate (80 %) Potassium Sulphate (10%) See notes at end of table.

I-52 

   S    S    7    4    3  ,    1    2    3  ,    4    0    3

 

  y   o    l    l   e   t    S    S   s   a    3    S    H  -    6    S    b    6    C    7    1    3    0    2    2    C    ®

   2    1   t   y   s   t   e    i   n   s   o   g   n   g   e   u   e    T    S   D

  m   u   z    i   t   r   n   a   a   t   u    i    T

   2    1    ®

A

A

A

A

B   A C C

A A  A  A A

A

A   A  A  A  A 

23 23 23 23

A A  A A

A

A   A  A  A  A   A 

15 15 15

Notes 

C o rro s io n R a t in g

SEE HYDROCHLORIC ACID A

A

A 

B

A

A

A

A

A

X X X X

A A 

X X X

X

X

AC

B

C

B

BC C C

BC C C

X

X

C

X

C

C

B

C

B

B

B

X X

X X

X X

BC X

BC C

AC

X X

X X

AC AC

AC AC

AC A

BC

BC

C

AC

A A AC

B

B

X BC C AC

X

B BC B X

BC BC

BC B B B

C B BC X

X B A AC

X X B AC AC

X X X

X B BC B B

AC A 

B B A

 

(Cyanide Free) AC

B

X

A

A

AC

B X

B B

B B B

B

A

AC A 

A 

X

AC

B

 A

A

A

A 

B

B B X B

A 

B B X X

A

A

B B B

B B C

A

B   A A  SEE IRON PHOSPHATE B B A  A AC AC

A

A

B B

A 

A

A

A

A

X

B

B

A

A AC AC A 

AC

X

AC

BC BC X BC X X

X X X X

AC

X X X

X X

X

BC C X X

C BC

B X

BC X

C X X X

A

B

23 - 26 A 

A

A

B B

X

BC A C B B B   AC B   AC B AC B   AC

AC AC AC AC

AC

AC

AC AC

AC AC

AC AC

AC

BC BC BC

B

A

A

C A

AC AC AC

AC AC AC

AC

AC

A    A

X X A  A A A A  A A  A A A A A A  A

X A A

X A

X C BC BC

C C X X

C X X

X

BC B BC

C BC BC

X B X

B AC

B B BC AC

B B B B B BC

1 1, 2 2, 7

23 - 26 23 23 - 26 15 - 23

2, 3, 7 2, 3, 7

23 - 40 23 - 40 23 23

1, 5, 9 1, 5, 9 1, 5, 9 5, 9

A  A  A   23 - 35 A   23 - 35 A  23 - 35 A   15 - 20

23 - 35 AC AC A  A A

X

A   23 - 35 A   15 - 20

15 - 20 A   23 - 35 A   23 - 35 A  23 - 35 A  23 - 35

15 - 20 A   23 - 35

A A 

A

BC B B B

A A A A  A

A AC A 

A  A  

X

X

X

A  A  A 

A A

A  A

A

15 - 20 15 - 20

A 

C B X X

30 - 40 23 - 26 6 - 15

A  

A 

A

A  A 

 

A A

C B

BC B

A 

B C X

AC

AC

A

AC

B

B

B

B

X B BC

B B

BC B

B B

A 

B

B B

A

A

A

A

A

B

2 1

A  

A  A  A

1 1

15 30 - 40

A  AC

2 1 1, 5 1, 5 1, 5 1, 5

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

1  

Technical

Reference Data Corrosion Guide for Electric Immersion Heaters (cont’d.) Legend

Sheath Material

 A  = Good to Excellent  B = Fair to Good C = Depends on Conditions X = N o t S u i ta b le Blank  = Data Not Available

  m   u   n    i   m   u    l    A

   l   e   e   t    S   n   o    b   r   a    C

   0    0    6    ®   n    E   o    L   r   r   e    N    I   p   t    O   p   s    C   o   a    C    C    N    I

   0    0    8

   0    0    4    ®    ®    O    L    L    E    d    O    N   a    C   e    O    N    I    L    M

S o lu t io n

Reynolds Brightener Rhodium Hydroxide Rochelle Salt - Cyanide Ruthenium Plating Silicon Oils Silver Bromide (10%) Silver Cyanide Silver Lume Silver Nitrate Soap Solutions Sodium Bichromate (Neutral) Sodium Bisulphate Sodium Bromide (10%) Sodium Carbonate Sodium Chlorate Sodium Chloride Sodium Citrate Sodium Cyanide Sodium Dichromate (Hot Seal) Sodium Hydroxide (50%) Sodium Hypochlorite (20%) Sodium Nitrate Sodium Peroxide (10%) Sodium Phosphate (Neutral) Sodium Salicylate Sodium Silicate Sodium Sulfate

Sodi m Su lde(< 0 Sodium Stannate Sodium Thiosulfate (Hypo) Solder Bath Steam (Medium Pressure) Stearic Acid Sugar Solution Sulfamate Nickel Sulfamic Acid Sulfur Sulfur Chloride (Dry) Sulfur Dioxide (Dry) Sulfur Dioxide (Wet) Sulfuric Acid (10% - 50%) Sulfuric Acid (98%) Sulfurous Acid Tannic Acid Tin (Molten) Trichloroethane Trichlorethylene Triethylene Glycol Trioxide (Pickle) Trisodium Phosphate Turco™ 4181 (Alkaline Cleaner) Turco™ 40 08 (Descaler) Turco™ 43 38 (Oxidizer) Turco™ Ultrasonic Solution Ubac™ Udylite™ #66 Unichrome™ CR-110 Unichrome™ 5RHS

   S    S    7    4    3  ,    1    2    3  ,    4    0    3

 

  y   o    l    l   e   t    S    S   s   a    3    S    H  -    6    S    b    6    C    7    1    3    0    2    2    C    ®

   2    1   t   y   s   t   e    i   n   s   o   g   n   g   e   u   e    T    S   D

  m   u   z    i   t   r   n   a   a   t   u    i    T

   2    1    ®

A A

A  A 

A

A 

Notes 

C o rro s io n R a t in g

A

BC X X

B X C

1 1 1

A 

B C X BC   A C

AC

X X

X C

AC AC

B X

23 - 26 C   AC

A A

A A

AC

AC

AC

AC

B BC B BC B

AC AC

A

AC

B B B

A  A  A 

C BC C

AC

A A A A

A   A  

1

A 

X B C X X X B X X X B X X

X BC C X C BC BC B X X X X X C X B

B

X BC B C C C X C X X BC C X B BC B B B B X C X X C C

C

B

A

A

A

A

A

X

X X X

C X X BC X X X X C X

X X X C X X X X X

AC

B X C AC

X C X

A 

X C X X X C X X

AC

X X X X X

X BC X X X BC BC

X C A 

X X C X X X B C X B C B C B X X C C B

BC

BC

AC

AC

B BC B

B BC B

A A AC AC

AC AC A  AC

BC

BC

X

B X

A

A 

BC B B B B B B B X

B B B

AC

A

A AC A

A

A

BC

BC

A

A

A A A

X

BC

BC

A 

AC AC AC

B B X A AC A  

X C

X BC

C

BC B

X B B X X

A  AC AC

X X X X X X X

B X AC

X BC B B B A 

BC B B BC X

B BC B BC C BC BC C BC AC

AC

BC

BC

AC

AC

B B X X X BC B X A AC A

A  AC AC

BC BC BC A

AC

BC B B BC

B B B B

AC

A 

BC B B X BC

BC B B B B BC B BC X BC B

A

X C B BC

BC X B X X X X B X

X X

A AC A

A

A  A

A

X BC B B B B B BC X B A A

BC

A

A

BC B X X X X B X

BC B B X BC BC B X

A

A

B

B

A

A A  A

A

A

X

BC

AC

AC A  A  A  A 

X

X

X

A

B

AC AC

AC

C

A  A  A 

A A A A 

X

BC A

C

AC

X X

AC

AC

B   A C B BC A  A   BC B C

BC B B X BC BC

X

BC B BC BC B B C B

A

A

BC B B B BC   A C B AC AC

AC

B B X

B B

C A AC A AC

A A

C A  A

B

A 

C

C C

A A

AC

X

X

A

X

A B   A A A AC

3

11 1 6, 8 5

4

4 10 - 15

A A A A A A A A A  A   A A

A  A A   10 - 23 A A  AC A   A   A  15 - 23 A  10 - 20 A   X 15 A  X 15 A  A A  AC A  

X

A

AC

A   55 A  A  A  A  A  A   A  A  A  30 - 40 A   15 A  20 A  23 A   A  A  A  A  A  A  A  A  

A A A A

A A

20

A

 

23 23 1

A  A 

23 A  A A A

A

4

 

 

X

7 1

A  A  A 

23

1 1, 5 1, 7 1 1 1, 5 1 1

See notes at end of table.

I-53 

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

Technical

Reference Data Corrosion Guide for Electric Immersion Heaters (cont’d.) Legend

Sheath Material

 A  = Good to Excellent  B = Fair to Good C = Depends on Conditions X = N o t S u it a ble Blank  = Data Not Available

  m   u   n    i   m   u    l    A

   l   e   e   t    S   n   o    b   r   a    C

   0    0    6    ®    L   n   o   r   r    E   e    N    I   p   t    O   p   s    C   o   a    C    C    N    I

   0    0    8

   0    0    4    ®    ®    O    L    L    E    d    O    N   a    C    O   e    N    I    L    M

S o lu t io n

Vegetable Oil Water, Deionized Water, Demineralized Water, Pure (Distilled) Water, Process Water, Potable Water, Salt Brine Water, Sea Watts Nickel Strike Whiskey Wines

W oods N ickelS t rike  Yellow Dichromate Zinc (Molten) Zinc Chloride Zinc Phosphate Zincate™

B X X X C C X X

B X X X X X X X

BC X X X B B BC BC

X X

X X

BC BC

X X

X

X X

B X X X

X

A A A A A AC

BC

B C C

A  A  A  A A  A  AC AC

A

B B B A 

B

A

B

X

X B

X BC

X X

X BC

   S    S    7    4    3  ,    1    2    3  ,    4    0    3

 

  y   o    l    l   e   t    S    S   s   a    S  -    H    S    3    b    6    6    C    7    1    3    0    2    2    C    ®

  m   u   z    i   t   r   n   a   a   t   u    i    T

C o rro s io n R a t in g B B A AC B A A A  B A A A  A A A A   BC BC B A  A BC BC B A  A C BC A  C BC BC A C A A  B A A  AC B A A  A  A  A A 

X X

X B

X B

B

A 

A A A

Actane™ - Ethone Inc. Alcoa™ - Aluminum Company of America Alcorite™ - Fredrick Gumm Chemical Co. Alodine™ - Amchem Products Inc. ARP™ - Allied-Kelite Products Div. Bonderizing™ - Parker Div. OMI Corp. Clorox™ - The Clorox Co. Diversey™ - Diversey Chemical Co.

23 - 26 50 - 75 50 - 75 50 - 75 A  50 - 75 A  50 - 75 55 55 A   55 55

X B

10 10 10 10, 11 10, 11 10, 11 10, 11 1 2

X A 

X

23

A 

Dowtherm™ - Dow Chemical Co. Dur-Nu™ The Duriron Co., Inc. Iridite™ - Allied-Kelite Products Div. Irilac™ - Allied-Kelite Products Div. Isoprep™ - Allied-Kelite Products Div. Jetal™ - Technic Inc. MacDermid™ - MacDermid, Inc. Oakite™ - Oakite Products Inc.

Notes 

1 1

A  A

   2    1   t   y   s   t   e    i   n   s   o   g   n   g   e   u   e    T    S   D

   2    1    ®

1, 5 1

Parkerizing™ - Parker Div. OMI Corp. Turco™ - Turco Products Div., Purex Corp. Ubac™ - The Udylite Co., OMI Corp. Udylite™ - The Udylit e Co., OMI Corp. Unichrome™ - M & T Chemicals I nc. Zincate™ - Ashland Chemical

N o te s

1.

This solution is a mixture of various chemical compounds or is a proprietary trade name whose identity and proportions are unknown or su bj ectt o cha e it hou tou rk ow l ed e Checkt hechem icalsu ppl ierorm a factrert o con rm t hechoiceof sheath material or alternate sheath materials that may be suitable.

2.

C A U T IO N — Flammable material.

.

Chem icalcom posit ion

aries idel. Con t actt hechem icalsu ppl ierforspeci c recom m e dat ion s.

4.

Direct immersion heaters are usually not practical. Recommend using clamp-on heaters on the outside surface of a cast iron pot.

5.

Element surface loading should not exceed 23 watts per square inch.

6.

For concentrations greater than 15%, element surface loading should not exceed 15 watts per square inch.

.

Con ce t rat ion s ar w idel. Seesu

8.

Remove crusts at liquid level.

9.

Clean often.

est ed at tde sit chartorcon t act ou rL ocalChrom al ox S al es of ce 

10 . Passivate stainless steel for maximum corrosion resistance. 11. Stainless steel materials may be subject to chloride or stress corrosion cracking in this environment.

. S

I-54 

est ed at tde sit ies do n otappl t o Te on ® coated heaters. Lower watt densities may be required.

Technical

Technical Information 

NEMA Enclosures &Chromalox Equivalents  NEMA Enclosures for Non-H aza rdous Areas The National Electrical Manufacturer’s Association (NEMA) publishes a classification system for electrical enclosures. The NEMA classification or type indicates the exposure or environment for which the enclosure was designed. While Chromalox E1, E2, E3 and E4 enclosures are designed for applications similar to the NEMA types, they are not identical due to modifications required to adapt the housings to heater configurations. Condensed descriptions of the NEMA non- hazardous enclosure types are listed below with the Chromalox equivalents indicated. The condensed descriptions are not intended to be complete representations of the National Electrical Manufacturers Association standards for electrical enclosures. For complete details on NEMA enclosure requirements refer to NEMA Std. No. 250. Type 1 E losu res  are for indoor use in locations where unusual service conditions do not exist. Intended primarily to provide protection against contact with the enclosed equipment and limited amounts of falling dirt. (C r ma l x 1 r e n e ra l rp se e c l o su res.)  Type 2 E losu res  are for indoor use providing protection against limited amounts of falling water and dirt.

Type 3 s re s  are for outdoor use providing protection against windblown dust, rain, and sleet and damage from external ice formation on the enclosure.

Type 6 P c l o s re s  are similar to Type 6 except Type 6P protects against the entry of water during prolonged submersion at a limited depth.

Type 3 R c l o s re s  are similar to Type 3 except Type 3R provides protection against falling rain.

Type 12 lo su res  are intended for indoor use providing protection against dust, falling dirt and dripping non-corrosive liquids. (C r ma l x E 2 a n d E e n c l o s re s. )  

Type 3 S c l o s re s  are for outdoor use protecting against windblown dust, rain, and sleet and providing for operation of external mechanisms when ice laden.

Type 1 2K c l o s re s (k k ts) are similar to Type 12 except they are provided with knockouts. Knockouts only permitted in either or both the top or bottom walls.

Type 4 s re s  are for indoor or outdoor use providing protection against windblown dust and rain, splashing water, and hose-directed water and remain undamaged by the formation of ice on the enclosure. (C r ma l x 4 i st re R e si sta n t o r 2 i st re a n d x p l si o n e si sta n t e n c su res.) 

Type 13 lo s res  are for indoor use providing protection against lint, dust, spraying of water, oil and non-corrosive coolant. (C r mal x E 2 en lo s res may e u se d. )  

Type 4 X c l o s re s  are similar to Type 4 except Type 4X also protects against corrosion.

The table below lists a comparison of the characteristics of NEMA and Chromalox enclosures for NonHazardous areas.

Type 5 s re s  are for indoor use and protects against dust and falling dirt. Type 6 s re s  are for indoor or outdoor use providing protection against the entry of water during temporary submersion at a limited depth and remain undamaged by ice on the enclosure.

o te  — For Classified (Hazardous) Location enclosures, refer to NEMA Enclosures and Hazardous Location Heaters elsewhere in this section.

C ompar ison of Specific Appli cations of En closures for N on-Haz ardous Locations r vi ders vi a de D esg re a De e gf rere tef c t iro nteAc t iao ni n sAt a i st   t ef ing vi r me n t al C di ti o n s   t ef ing vi r me n t al C di ti o n s   In c id e n ta l c o n ta c t w ith th e e n c lo s e d e q u ip m e n t F a llin g d irt F a llin g liq u id s a n d lig h t s p la s h in g st lint bers and

ing s —

otC lass III

1

1

2

 

2

3

3R

3S

Type f 4 4X

5

s re

6

6P

11 12 12K 13 11 12 12 1

E1 1

C r ma E2 E3 2

® 

E

X

H o s e d o w n a n d s p la s h in g w a te r O il a n d c o o la n t s e e p a g e O il o r c o o la n t s p ra y in g a n d s p la s h in g  W in d b lo w n d u s t R a in , s n o w a n d s le e t S le e t C o rro s iv e a g e n ts O c c a s io n a l te m p o ra ry s u b m e rs io n O c c a s io n a l p ro lo n g e d s u b m e rs io n       N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

-5

Technical

Technical Information NEMA Enclosures & Hazardous Location Heaters N

A clo s res fo r Classi ed c a ti o s (H a za rd s)  

The following are condensed descriptions of the NEMA enclosure types for Classified (Hazardous) Locations. The Chromalox enclosures equivalent to the NEMA description are indicated. The Chromalox enclosure may not be indentical to the NEMA description due to modifications required to adapt the housing to heater configurations. The NEMA enclosure descriptions are not intended to be complete representations of the National Electrical Manufacturers Association standards for electrical enclosures. For complete details on NEMA enclosure requirements, refer to NEMA Std. No. 250.

Ch roma x c l o s res f o r E ec t ri c Heaters in Classi ed catio s  Chromalox has terminal enclosures specifically designed for use on electric heaters installed in Classified (Hazardous) areas. These enclosures are identified as Type E2 and E3. Typical flange heaters with E2 hazardous area terminal enclosures are shown below. EYS Seal

Resistant enclosures.)

2

Type 8 Enclosures —  are intended for indoor

or outdoor use in locations classified as Class I, Groups A, B, C and D as defined in the National Electrical Code. (Chromalox E2 enclosures.) 2 Type 9 Enclosures —  are intended for indoor

use in locations classified as Class II, Groups E, F and G as defined in the National Electrical Code. (Chromalox E , E3 or Explosion Resistant enclosures.) Type 1 0 Enclosures  (MSHA) shall be capable

of meeting the requirements of the Mine Safety and Health Administration, 30 C.F.R., Part 18.

C o mpa ri s n

plug and flanged immersion heaters are available with terminal enclosures CSA or CSA NRTL/C certified for Class I, Groups B, C and D and Class II Groups E, F and G. Supplemental low-liquid level controls are required for maximum safety and equipment protection when immersion heaters are used in hazardous locations. 2 Circulation Heaters —  Many water and oil

Type 7 Enclosures —  are intended for indoor

use in locations classified as Class I, Groups A, B, C and D as defined in the National Electrical Code.  (Chromalox E , E3 or Explosion

Immersion Heaters —  Screw

Explosion R esistant Enclosure

circulation heaters are available with terminal enclosures CSA or CSA NRTL/C certified Class I, Groups B, C and D and Class II, Groups E, F and G. Supplemental controls are required for maximum safety and equipment protection when circulation heaters are used in hazardous locations

Explosion Resistant E n cl o s ure w i t h E Y S S e a l

E2 enclosures are supplied with gaskets and are suitable for both indoor and outdoor locations. E2 enclosures meet the moisture and explosion-resistant requirements for NEMA 4, 12, 7, 8 and 9 applications. E3 enclosures are usually not furnished with gaskets and are intended primarily for indoor and dry locations. See table below.

Electric H eaters fo r Hazard s

catio s 

Chromalox provides a wide variety of electric immersion and air heaters for use in hazardous locations. These heaters are listed by Underwriters Laboratories (UL) or certified by Canadian Standards Association (CSA). Heaters designed and certified for Class I or II Division I hazardous locations can be used in Division 2 areas in the same class.

f pec i c App i c a ti o s f

c l o s r es f o r I n d r H aza rd

s

 Blower type air heaters (CXHA) are available for Class I, Division I, Groups C and D and Class II, Division I, Groups E, F and G with UL, UL-C, and/or CSA certification. Convection type air heaters (CVEP) are available for use in Class I, Division I, Groups B, C and D hazardous locations. Convection type air heaters (FPEP and CEP) are available for use in Class I, Division I, Groups C and D and Class II, Division I Groups E, F and G.

 A ir H e a te rs

S pecialty Products & Components

Chromalox has designed, manufactured and provided certification on a large number of specialty products for hazardous areas and other special applications. These products include UL Recognized Components (finned tubular elements), duct heaters and special aircraft ground support equipment. Contact your Local Chromalox Sales office for assistance in designing equipment or solving any unique electric heating application for hazardous areas.

c a ti o s   N EM A

 A tm os ph e re s C on ta in in g

C la s s

Acetylene I Hydrogen, Manufactured Gas I Diethel Ether, Ethylene, Cyclopropane I Gasoline, Hexane, Butane, Naptha, Propane, Acetone Toluene or Isoprene I Metal Dust II Carbon Black, Coal Dust, Coke Dust II Flour, Starch, Grain Dust II Fibers, Flyings III Methane with or without Coal Dust MSHA 1. Requires seals in the conduit adjacent to the terminal enclosure. 2. For EMT and MT styles, Class 1 Group B; Divisions 1& 2, consult factory.

I- 5

C hrom a lox  

G rou p

A B C D E F G G

X X X X

X X X X X X X X X

E

E

X1,2 X X X X X X

X1,2 X X X X X X

Technical

Technical Information Hazardous Locations & Electric Heater Applications Hazardous Locations (NEC)5  A rtic les 0 to 4 in t he N at ional E lec trical Code (NEC ) defi ne the requirements for electrical and electronic equipment and wiring in locations wh ere fi re or explosion hazards may exist. In Article , hazardous locations are categorized by class. Class es are defi ned as follows

Class I — Groups A, B, C & D - Division 1 or 2 Temperature Rating T1 - T6 Class II — Groups E, F & G - Division 1 or Temperature Rating T1 - T6 Class III — Division 1 or 2

Cla ss I, II & III (NEC 500) Hazardous location class es are identi ed based on the explosive material present. The following informat ion is an interpretation and sum mary of each class and a discuss ion of some of the conditions to be considered when using electric heaters in these areas. Refer to the N ational Electrical Code and local authorities for the proper class ifi cation and requirements of a specifi c hazardous location.

Class I Locations (Gas es) are areas where amm able gas es or vapors are or may be present in the air in quantities s uffi cient to produce explosive or ignitable mixtures ( NEC 5 - ) . Class II Locations (Dus t) are areas where the presence of combus tible dust presents a fi re or explosion hazard (NEC 5 -6 ). Class III Locations (Fibers) are areas m ade hazardous because of the presence of easily ignitable fi bers or fl yings, but in which such fi bers or yings are not li ely to be in sus pension in the air in quantities suffi cient to produce ignitable mixtures (NEC 5 -7 ).

G roup Cl assifi cati on, C lass I & II 6 Certain chemicals create higher explosive pressures and m ore heat than others when ignited. In Class I and II hazardous locations, chem ical fam ilies are further class ifi ed by Groups. Group classifi cation involves determination of the m aximum explosion pressures, the maximum safe clearance or gap between clamped enclosure joints and the minimum ignition tem perature of the atmos pheric mixture for a particular chemical.

NEC requires tha t any electrical equipment approved for use in a hazardous location must be approved for the class and for the specifi c group (g as or dust) that will be present. Groups are identi ed as A , B, C, D, E, F and G and are explained as follows:

Class I — Gases6(NEC 500-3a) Combus tible and ammable gases and vapors in Class I are sub-d ivided into four groups A , B, C and D. Group A gases create the most explosive press ure and therefore are the most diffi cult to contain. Group B is next, then Group C w ith Group D being the lowest. Third party listings of electrical equipment for G roup A or B are more diffi cult to obtain than Group C or D. Individual gas es are further defi ned by ignition temperature (see Temperature Ratings).

Group A — Gases include:  A ce ty lene Group B — Gases include:

Ignition Temperature °C °F 5

Ignition Temperature °C °F Butadiene 420 788 Ethylene oxide 429 804 H ydro gen & m fg 0 g a s es > % h y dro g en ( b y v olu m e Propylene oxide 449 840 Group C — Ignition Temperature Gases include: °C °F  A ce ta ldehy de 5 C y clo pro pa ne 0 D ie th y l e th er 0 Ethy lene 0 D im e th y l h y dra zin e 9 Group D — is the larges t group and includes many of the comm on petroleum products. Gases include:  A ce to ne  A lcoho l’s - bu ta no l ( bu ty l)  Am y l alc oh ol B ut y l a lc oh ol ( t er) E th an ol ( e th y l) Is o bu ty l a lc oh ol Is o pro py l a lc oh ol M e th an ol ( m et hy l) P ro py l a lc oh ol  A m m on ia  Benzene Butane Ethane

Ignition Temperature °C 5 5 0 0 6 7 9 5 0 651 0 5 5

°F

Gases include: E th y l a ce ta te Ethylene dichloride Gasoline ( 5 6 - 0 octane) ( 1 0 0 octane) Heptanes Hexanes Is o bu ty l a ce ta te Is opre ne M ethane ( N at. g as ) M e th y l e th y l e to ne Petroleum naphtha  Octanes P entanes P ropane  V iny l ac et at e  V iny l ch loride y lenes

Ignition Temperature °C °F 7 3 0 6 0 5 1 0 2 6 288 0 0 0 7 2 0

550

Notes 1. Group D equipment m ay be us ed for this atm osphere if isolated in accordance w ith S ection -5 (a) by sealing all conduit(s) /2 inch or larger (within 8 inches of the enclosure). 2. Group C equipment m ay be us ed for this atm osphere if isolated in accordance  w ith S ec tion 5 -5 a) by s ea ling all conduit(s ) 1 /2 inch or larger (within 8 inches of the enclosure). 3. For Classification of Ammonia Atmospheres see S afety C ode for Mechanical R e frig e ra tio n ( A N S I /A S H R A E 1 - 1 and S afety Requirements for the S torage and Handling of Anhy drous A mm onia ( AN S I C GA G 2 ). 4. Also Known By the synonym s benzine, ligroin, petroleum ethe r or naphtha. 5. NEC and National Electrical Code are registered trademark s of the National Fire Protection Association. 6. For a Complete List defi ning properties of amm able liquids, gases , solids or dusts, refer to the latest edition of NFPA 325, NFPA 497 or NFPA 499.       N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

1204

I-57

Technical

Technical Information

Hazardous Locations & Electric Heater Applications C l ass I I —

D u st   N E C

- b

Groups E, F a nd G (Clas s II) —  C mb stib e

d sts are divided i to ro ps E , F an d G . Classi atio n in vo ves i vestig atio n an d testi g f t e assem ed e s re i di g t e amped j in ts, c eara es an d s aft o pe in s. Th e b an keti g effe t o f layers o f d st t e e e trical d tivity a d t e i itio temperatu re o f th e d st are also evalu ated. Group E Atmospheres  c

tain metal du st i di g a mi m, ma esi m, t eir co m mer ial allo ys a d o th er metals o f similarly azardo s c aracteristi s h avin g resistivity less th an 10  O m- c m. Group F Atmospheres  c o tain c o m

sti e ar a e s d sts, ar a , al r t er atmo sp eres tain in g th ese d sts sen sitized y o th er azardo s materia s a d h avin g resistivity reater th an 10 2  t r h 1  O m- c m. Group G Atmospheres  c o tain c o m

s ti e d sts s h as r, rai , da d emic als h avin g resistivity o f 1  O m- c m r g reater.

C l ass I II —

F i bers N E C 5

- a)

Atmo sp eres co tain in g easily i ita e fi ers s h as ray , co tt , fl a , te, h emp, kap k, ex elsio r an d similar materials.

D ivisions in H azardous L ocations T e C fu rt er s -divides azard s a tio s i to ivisio s ( iv. 1 an d 2). T e re ireme ts fo r D ivisio n 2 are ess stri en t th an fo r ivisi n 1. T e t o divisi s are discu ssed i t e fo i g para rap s.

D ivision I L ocations  N C - 5 ( a) is a area w ere t e h azard can e ist der rmal perati g ditio s. In ded are areas w ere amma e r mb stib e iq ids are tran sferred fr m e tai er to an t er, pe vats, pain t spray t s r an y atio n ere ig itab e mi tu res are sed. Also in lu ded are atio s ere a azard is a sed y fre e t main te an e, repair o r eq ipme t fail re. Class I, Division 1

 N C - 6 ( a) is a area w ere co mb stib e d st is n rmal y in t e air in s ffic ie t q a tities to pr d e i it Class II, Division 1

I- 5

a e mi t res o r w ere mech an ical fai re r a rmal e ipmen t perati n mi t pro d e i ita e mi t res. atio s also i de peratio s w ere azards e ist b e a se freq e t me an i al fai re f ma in ery r e ipme t a d w ere e e tri a y co d tive mb stib e d sts (a l ro p E a d so me ro p ) are prese t in azard s a tities.  N C - 7 (a) is a area ere easily i itab le ers o r materials pr d i g m sti e yi s are a d ed man fa tu red o r u sed. Class III, Division 1

D i v i si on 2 L oca t i on s  N C - 5 ( ) is an area ere i itab e g ases r vap rs are h an dled pro essed r sed, t ich are rmal y in sed co tain ers o r clo sed systems fr m ic h t ey c a n y esc a pe t r h ac c ide ta r pt re r reakd n f s h tai ers r systems. Class I, Division 2

 N C - 6 ( ) is a area w ere mb sti e d st is n t n rmal y in t e air in su ffi ien t an tities to pro d e ig itab e mi tu res r in terfere ith th e pera tio n f e e tri al eq ipme t, r w ere d st is prese t as a resu t o f i freq e t malfu tio i g f pr c e ssi g r h a d i g e ipme t. In ded are sit atio s ere m stib e du st acc mu atio s may in terfere ith th e safe dissipatio n f h eat fro m elec tric al eq ipme t. o e e tri a y c d tive d sts as de ed in C 5 2-1, ( ast sen ten e) are i ded i Class II, D iv. 2 atm sp eres. Class II, Division 2

release po in t f t e amma le li id. Wh ere th e spread o f fl amma le vapo rs a d g ases is t tain ed y adeq ate partitio s, th e area desi ated as Class I, D iv. 2 serves as a “tran siti n z o e” et een t e az ard s a d azardo s area. iv. 1 is th e h azardo s area ere fl amma e g ases r vap rs are released fr m t e liq id. D iv. 2 is th e area f rt er aw ay fr m th e po in t f release, ere th e ases r vap rs are t no rma y f s ffi ie t e trati n to pro d e an ig itab e mi tu re.

C l a ss I & I I —

ri i a y, e ipme t in ea h r p ad e ma im m temperatu re rati . T e max im m r r ps A, B a d D as 2 ° C ( ° F ) a d r p C as 1 ° C ( ° F ) . ec o iz i g t at emicals an d ases ave differe t ig itio temperat res, N C revised t e temperatu re ratin s acc rdin y. Heat pro d in g e ipmen t m st n w e ide ti ed by C ass, G r p, D ivi si n an d “T” rati . Th e “T” rati g sh all t exc eed t e i itio n temperatu re f t e specifi as, vapo r o r du st prese t. Val es f r “T” ratin s fo r C ass I a d II e ipmen t are sh n in t e ta e e

T-Ra tin gs for C lass I an d II Maximum D e g re e s ( ° C )

Temperature D e g re e s ( ° F )

Identifi cation T ” N u m be r

450 300 280 260 230 215 200 180 165 160 135 120 100 85

842 572 536 500 446 419 392 356 329 320 275 248 212 185

T1 T2 T2A T2B T2C T2D T3 T3A T3B T3C T4 T4A T5 T6

Note —

T ere is o ivisi n 2 assi ati fo r C ass II, ro p .  N C - 7 ( b ) is a area w ere easi y ig itab e fi ers are sto red o r an dled. Class III, Division 2

C l a ss I —

A d j a cen t D i v i si on s

In mo st in do r areas ith adeq ate partitio s, iv. 1 an d 2 are self-c tain ed areas. With partitio s, a D iv. 1 area may ex ist adja en t t a -h azard s area. H ever, td rs r in ar e i d r areas w ith few r n o parti tio s, Class I, iv. 1 a d Class 1, D iv. 2 areas su al y e ist adjacen t to ea h th er. T e D iv. 1 ati n ein g ear th e p in t o f vap r release an d D ivisio n 2 is at a iven distan e fro mt e

T em p er a tu re R a t i n gs

 — r a mp ete list de i g pr per ties f fl amma e liq ids, ases, s lids r du sts, refer to th e atest editio n f N A 25 FPA497 or FPA499 . Note

Technical

Technical Information Control Systems Selection Guidelines Topics: Process controls, overtemperature controls, level controls, s ensors, pow er controls, and panels.

Now that you hav e s elected the heater(s ) for y our process, it is time to choose control components, panels, and sensors, to provide the desired results.

System Considerations In order to as sem ble a complete control system , you will need the following information

Voltage, wattage, current (calculated from voltage and w attage), Number of zones: (different sections controlled differently) , Area location or classification: (indoor, outdoor, explosion hazard), and

Closed Loop Control System

The desired process temperature range, as well as permitted deviations should be spec ifi ed. Close control and/or control of one pass heating of g as or liquids w ill probably require electronic control Process accuracy issues: For large mas s processes (big tank s, large block s of m etal) w here the temperature won’t or can’t move quick ly, and the tem perature requirement is not critical, mechanical bulb and capillary t hermos tats can us ually be us ed, or if electronic control with indication is needed a s imple On/Off controller with a contactor is nec ess ary. Process speed: For proces ses hav ing low ma ss , fast, accurate control is impo rtant. A proportional or PID controller with an S CR power controller would be a good choice. Process upset: If the proces s is s ubject to upset, ( oven door opened for new bat ch, for inst ance), a P ID control will be required for good results This is also the case if heating liquid or gas (air) in one pass. A n S CR will be needed as w ell Environmental (ambient conditions): Process controls, overtemperature controls, and accessories must be selected with the surrounding area in mind. Wet, dry, and explosion hazard areas mus t be considered, as w ell as the am bient temperature range the equipment w ill operate in. Mec hanical controls should not be expos ed to tem peratures abov e their stat ed range. Electronic controls are designed to operate in an ambient temperature of above 3 2 F, and below a stated maximum, usually 1 0 or 0 F Safety: An ov ertemperature control should be included to protect process , area, heater(s ), and/or product in the event of a primary control failure, or interruption of fl ow in mov ing sy stem s. If the power control is an S CR , a contactor or shunt trip should be provided so the load can be shut dow n, even if the SC R’s are shorted. If heating confi ned liquid or gas , an approved m echanical temperature/press ure relief valve is als o required. For some areas, AS ME certifi cation may be required on press ure vess els.

System Components These parameters will help you determine the sys tem com ponents you need:

Sensor: This can be a bulb and capillary, thermocouple, RTD or non-contact IR s ensors Temperature Controller: This can be a m echanical bulb & capillary cont roller or an electronic controller to accurately control the process • Ove rtemperature Controller (Lim its) : For protection of the process and/or the heater sheat h, an overtemperature controller should alway s be us ed to ensure sa fe operation in the event of process co ntrol failure and/ or interruption of fl ow in dynam ic sys tem s. • Pow er Controller: In order to switch the heater load, either mech anical contactors or S CR s are needed.

Sensors The sens or is the dev ice measuring the temperature or other variable of a sys tem. It is us ually in direct contact with the heated medium and m ust be specifi ed to handle the temperature and conditions of the process . Electronic controllers convert the signal from RTD’s and thermocouples to a temperature reading.

Thermocouples Rugged and versatile, with many selections for various temperature ranges, thermocouples consist of two different material wires welded together. Thes e devices produce a very sm all DC v oltage, depending on tem perature and thermoco uple type. The controller or overtem perature controller, interprets this voltag e, and compares it with internal standards, displaying and /or controlling a tem perature.  A dv an tag es : L ots of choic es , ru g g ed , inex pens iv e.

I-59

      N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

Technical

Te

i al In rmati

C tro l ystems e e tio n

ide in es (cont d.)

Disadvantages: Output is not linear with temperature when new thermocouples are within 2 to 3 F accuracy. Thermocouple alloys age, which affects accuracy further. Microprocessor controls are best at interpreting TC voltage curves. Thermocouple wire of the same type as the thermocouple (i.e. type J for J), must be used to connect the thermocouple to the controller. N o te The red lead is always the negative lead in USA thermocouple color-coding.

RTD’S RTD’s or Resistance Temperature Detectors, provide a resistance change linearly related to a temperature change. The most common is the 100-ohm platinum. The controller measures the change of resistance, and relates it to temperature. Advantages: RTD’s are much more accurate and more linear than thermocouples. Standard copper wire can be used to connect the sensor to the control. Since the signal is larger than a thermocouple signal, it is more immune to electrical noise. Three wire RTD's can also be run longer distances than thermocouples. Disadvantages: RTD’s are more costly than thermocouples, and less rugged. In addition, they should not be exposed to a temperature higher than their rated operating temperature. Don’t weld or braze them.

Transmitters A transmitter is an electronic circuit that converts the low level signal of a thermocouple, RTD, or other device or parameter (like humidity) to a current loop, typically a 4 to 20mA signal. This produces better immunity to noise than the low-level signal by itself. Advantage: Longer control signal runs are possible without interference. Disadvantage: Increased cost of installation.

Infrared Sensor IR (non-contact) sensors provide a control signal related to the temperature of an object, without touching the object. The IR sensor “looks” at the process, and adds or reduces heat as required. They are often used in continuous processes where material is passing through a convection oven or under radiant heaters. Advantages: Provides good closed loop control for flowing processes or surface drying applications. Disadvantages: More expensive than contact sensors. Does not work well for shiny objects. A temperature control is still required to interpret the output of an IR sensor, compare it to the setpoint, and operate a power controller.

S ensor Placeme nt  Placement is very important for a good control result. The temperature control, no matter how smart its PID loop is, can only process the information supplied to it.

Heater

Sensor

Where possible, in a block type system (like a platen) the heater, sensor and load (die) should be as close together as possible. This minimizes thermal lag, and provides good response to changes. (See Figure 1) In a stable system, where the heater is separated from the load, the sensor can be placed near the heater to provide for close heater control. The load will be cooler than the sensed temperature by the drop through the heat transfer path from the heater to the load. This is not good for changing condition systems. (See Figure 2)

A compromise may be provided for by placing the sensor between the heater and the load. This is good for fairly stable systems where the heat demand may be alternately constant or variable.(See Figure 3)

Load

Figure 1 Best S olution

For changing systems, the sensor can be placed closer to the load to respond to changing load requirements. The sensor farther from the heater increases the thermal load. This will cause overshoots and undershoots. A PID controller is required to minimize the temperature cycling. (See Figure 4) In conclusion, it is important that the heater, sensor and load be as close as possible. The sensor should always be between the heater and the load. I- 6

Figure 2

B

Figure 3

Figure 4

Technical

Technical Information Control Systems Selection Guidelines

cont’d.)

 W iri ng Th erm p e e ten sio n ire f t e same type as t e th erm p e (J fo r ) mu st e sed to e t tr s to se so rs. a y varieties th ermo ple e te si n ire are avai ab e, ith in su atio n types f r differe t e viro me ts. Fo r t ermo ples, t e n eg ative(-) lead is al ays red in th e A. C pper w ire an e sed fo r R T ’s an d -2 mA sig a s. T ’s an d t ermo ples ave w evel e ectri al sig a s. ie din g is re mme ded. T e s ie d s d y e r ded at e e d (t e tr er e d) to av id r d ps. e s r w ires s d t e run in t e same d it as p er ires to preven t i terfere e.

Environmental and Safety en so rs an d acc esso ries mu st e se ected ith th e su rr di g area in mi d. Wet, dry an d expl si n azard areas mu st e sidered, as el as t e amb ien t temperat re ra e t e e ipmen t w ill see. I s atio n fo r e ten sio n irin g m st a so e a e to it stan d t e amb ien t co ditio s. ectro ic se so rs an d tran smitters are desi ed to perate ab ve 2 F, a d el w a stated ma im m, su al y 120 r 14 0 F. S ee specifi c it fo r perati g am ie t temperat re ran e.

Choosing a S ensor S ele ction Criteria  Th e m st po pu ar se so r is t e t ermo  yo r pro ess. F r b est ac rac y, u se an

ple, an d o f t se, J an d K are m st freq en tly u sed. elect a TC ith a temperatu re ra e mat ed to TD less yo r temperatu re ran e do es n t permit.

ervice iss es: W en p a in g a se s r t ro placed ith t drain in g t e ta k.

Thermocouple Type

J K T E N R S B

Temp Range

3 0 0 to 14 0 0 F

4 5 0 to 23 0 0 F

4 5 0 to 7 0 0 F

Recommended Temperature Range

3 2 to 14 0 0 F

h t e side f a tan k f liq id,

Temperature Rang e for Standard Limits of Error 2 to 527 F (0 to 2 5 C)  559 to 1 0 F (293 to 7 60 C) 

Standard Limits of Error

+/- 4 F +/- .75%

sider si g a se s r ith a t erm

Negative  W ire Color

RE

Positive  W ire Color

WH TE

 J a ck &  Plug Color

 A pp li ca ti on Inf orm a ti on

itable for va m, reduc ing , o r i ert atm sp eres idizing atmosp ere w ith reduc ed life. Ir n idizes B LACK   rapidy a ve 1 0 F (53 8 C), so y heavy aug e ire is reco mme ded f r h igh to su p rou s atm sp eres abo ve 1 0 F (5 8 C). Reco mmended for co ti s xidiz ing r neutra atmosp eres. M stly sed abo ve 100 0 F (5 8 C). je t to fail re if expo sed to sulphu r. P refere tial idation f ch romium in positive leg at ertain lo Y ELLOW   xyg en co cen tration s causes ‘ reen ro t’ and a d larg e neg ative cali rati n drifts m st seriou s in th e 1 -1 0 F (8 1 -1 8 C) ra e. Ventilati n r i ertsealing f t e protecti n tub e can preve t t is.

3 2 to 23 0 0 F

-3 28 to -166 F (-200 to -110 C)  -166 to 3 2 F (-110 to 0 C)  2 to 559 F (0 to 293 C)  559 to 2282 F (293 to 1250 C) 

/- 2 +/- 4 F +/- 4 F -.

3 0 0 to 7 0 0 F

-3 28 to -89 F (-2 0 to -67 C)  -8 9 to 3 2 F (-67 to 0 C)  2 to 2 1 F (0 to 133 C)  271 to 662 F (1 3 to 0 C) 

/ - 1. / - 1.8 / - 1.8 +/- .75%

-3 28 to -2 4 F (-2 0 to -1 0 C)  -2 4 to 2 F (-1 0 to 0 C)  2 to 6 4 F (0 to 34 0 C)  6 4 to 1652 F (3 0 to 9 0 C) 

/- 1 /- 3.1 /- 3.1 - 0.

RE

P URP LE

Reco mmended f r co ti sly ox idizi g r i ert atmosph eres. S -zero limits f error n t estab lish ed. P URP LE   Hi est therm electric o tp t f co mm n cali ra ti s.

2 to 559 F (0 to 293 C)  559 to 23 0 F (293 to 1260 C)  + / - 4 F   to F ( to C)  +/- .75%   to F ( to C) 

RE

ORA GE

ORA GE   ave s rter life a d stab ility pr lems due to

RE

RE

Y ELLOW

LUE

LUE  

4 5 0 to 18 0 0 F

3 2 to 16 0 0 F

3 2 to 4 20 0 F

3 2 to 23 0 0 F

3 2 to 27 0 0 F

10 0 0 to 27 0 0 F

2 to 1112 F (0 to 6 0 C) 1112 to 2642 F (60 0 to 14 50 C) 

/ - 2.7 / - .2

RE

B LACK

GREE

3 2 to 27 0 0 F

10 0 0 to 27 0 0 F

2 to 1112 F (0 to 6 0 C) 1112 to 2642 F (6 0 to 1 50 C) 

/ - 2.7 / - .2

RE

B LACK

GREE

14 7 2 to 3 10 0 F

el , so th e sen so r an e re

16 0 0 to 3 10 0 F

147 2 to 30 92 F ( 0 to 170 0 C) 

-

.

RE

GRA

Useable in idizing , reduc ing , o r inert atm sp eres as ell as vacu m. N t s ject to c rr si n in mo ist atmosph eres. Limits o f erro r p lish ed fo r s -zero temperatu re ra es.

Can e u sed in applicati s w ere Type Kelemen ts idati n and th e development o f ‘green rot’. Re mmended fo r h igh temperat re. M st e protected ith -metallic pr tectio n tub e a d ceramic insu lators. C ti ed igh temperat re usa es c a u s es g r ai n g r th i c h c a n ead to mec h a i c a failu re. N eg ative calib rati n drift au sed y Rho di m diffusion to pu re leg as ell as fr m R di m vo latilizatio . Type R is u sed in in du stry; Type S in th e la rato ry.

ame as R &S t o tp t is l er. Also less suscepWH TE   ti e to rain g row th an d drif t.

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Technical

Technical Information

Control Systems Selection Guidelines (cont d.) Recom me nded Upper Tem peratures for Protected Thermocouples Thermocouple Type

 J K  T E N

S heath Diameters & Wire S izes for S ingle Elements 1 6 OD 1 8 OD 3 6 OD 1 4 OD

Maximum Element  Temperature

8 G auge

2 G auge

9 Ga ug e

6 G auge

700 F

700 F

900 F

900 F

1400 F  

1600 F

1600 F

1800 F

1800 F

2300 F  

400 F

400 F

500 F

500 F

700 F  

800 F

800 F

1000 F

1000 F

1600 F  

2300 F

2300 F

1800 F

1800 F

2300 F  

Temperature or Process Controllers Electric heat, while c lean, efficient and manageable, can cause damage to product and / or equipment if the temperature is not known, and correc-  tions applied as required. Bes t res ults will be obtained whe n the maximum and minimum allowable tempe ratures for a given proc es s are known, and controls selected to achieve these results.

Type s of Controllers: Electronic Controllers Electronic Controllers rece ive a s ignal from a thermoc ouple or RTD and determine how much heat is needed to control the proces s . Thes e c ontrol-  lers can range from very s imple dial co ntrollers to complex multiloop PID co ntrollers .  Advantage s : Very acc urate control, digital dis plays and fl exibility for many applications  Disadvantage: More expensive than s ome mec hanical controls .

Bulb & Ca pillary and Bi-Meta l Thermosta ts Mec hanical thermos tats depend on expanding liquids or metals to open or clos e contacts in res pons e to temperature c hanges . Us ually, no tem-   perature is dis played, and a calibrated knob is provided on some models . In mechanical controllers , the se nsor is part of the controller.  Advantage s : Relatively inexpensive. Some bulb and capillary co ntrols can switch large amounts of current for one or more poles (c onductors). Easy to s et up, jus t turn the knob for the des ired tempe rature. Disadvantages : On-off c ontrols s ome times have a large differential or dead band. This is the difference in deg rees between turn off and turn on. our proces s variation will be g reater than the dead band. Bulb and capillary controls do not fail s afely. If the c apillary tube with the fl uid in it be-  co mes pinche d or broken, the thermos tat will fail in a heat-on c ondition, which is a hazard. Bi-metal thermos tats, which have no bulb or capillary, typically have smaller deadbands , and can co ntrol more c los ely. Some will not ope rate a contactor, which may be nee ded to s witch the higher cur-  rents and voltages needed by the heater. They are o ften appropriate o nly for small 120-240V s ingle-phas e he aters . Tempe rature accuracy is inferior to electronic co ntrollers.

Control Modes Manual: (s witch or c ircuit breaker) For s ome applications , s uch as water pipe freeze protec tion, c ircuit breakers are turned on in the Fall and off in the Spring.  Advantage s : Low co s t, eas y operation. Disadvantages : Pos s ibility of not remembe ring to turn on equipment in the fall. Energy is wasted when equipment is on if it is not required. Con-  s ider an ambient temperature control to s witch the equipment on if the temperature is below 40 F.

I- 6

Technical

Technical Information

Control Systems Selection Guidelines (cont'd.) Open Loop(Intensity or duty-cy cle control):

Heater

Process

Includes motor driven timers, infi nite control bi-met al relays , and SC R controllers with k nobs for setting power percentage. Open loop control does not use a sensor to determine the amount of heat needed. The control device is set to a s peci c percent output and switches the output on and off to app roximate th e percentage of av ailable heater wattag e. Typically us ed for radiant heat.

Power

Controller

 A dv an tag es : L ow co s t, ea s e o f o pe ration

Controller

Control Signal

Disadvantage: Does not compensate for variations in ambient temperatures or incoming product temperatures. Must, in many cases be reset, often after operator observation of poor process results.

A.C. Power

On Off (bulb & capillary, bi-metal, or electronic) ( S ee Figure 5

Open Loop Control S ys tem  The deadband (Hy steres is) represents a n area about set point in which no control action tak es place, and determines at w hat temperature the output switches ON and OFF. Narrow deadband settings giv e more accurate control but result in more frequent output sw itching, which can cause ea rly failure of electromechanical contactors. On-Off control is av ailable in electronic, bulb and capillary, and bi-met al controls.

Disadvantage: The control is only as accu rate as the deadband. Large overshoots will occur  w ith s y s te m s w ith s ig nifi ca nt lag

    e     r     u      t     a     r     e     p Operating Differential     m     e Hysteresis/Deadband      T

Proportional  Proportional controls reduce the h eat output gradually (w ithin the Proportional Band) , as the process approaches the s et point.

    e     r     u     t     a     r     e     p     m     e      T

Setpoint

 A dv an tag e: M ore ac cu rat e c ontro l th an On -off control. In stable conditions ( cons tant load), proportional control can ma intain a spec ifi c tem perature. S ince they are electronic, with  w ired s en s ors , s uc h a s th erm oc ouples , the control can sense an open sensor and s hut down the p rocess , resulting in a safe r control sy stem than mechanical on-off controls.

Proportional Band Overshoot

Setpoint

Offset Undershoot Manual Reset  Adjustment

Time

Figure 5 

Time

Figure 6 

Disadvantage: Proportional controls work best on stable process es. They have trouble m aintaining temperature during process upsets. S ome proportional controls can s witch sig nifi cant loads with optional high current relays and s olid state s witching dev ices.

PID  PID (P roportional, Integral, and Derivative) controls, when properly s et up (tuned ) can man age m ost s ituations, including process ups ets . Lik e a Proportional control, the heat output is g radually reduced w hile approaching s et point, but also w ith the integral and derivative action can control process es w ith vary ing loads at set point. A wide variety of sens ors and parameters ensure a good m atch of control to process. M any PID controllers have autotuning functions that automatically tune to the process.  A dv an tag es : G ood o v era ll co nt rol. S ince t hey are ele ct ronic, w ith w ired s en s ors , s uc h a s thermocouples, the control can sense an open sensor and shut down the process, resulting in a safer control system than mechanical on-off control. Disadvantages: More costly; m ore set-up required because of g reater fl exibilty. Requires external power controller to s witch the load.

Overtemperature Controls(High Limit Controls):

   e    r    u     t    a    r    e    p    m    e     T

PI PID

Proportional Band Offset

Setpoint P PD Time Figure 7 

(Bu lb & capillary, electronic non-indicating, and electronic indicating) Ove rtemperature controls prov ide a safety back up for the primary control and/or the heaters in case o f a problem. The ov ertemperature controller's function is to protect the process or heater. In an overtemperature condition the overtemperature controller will shut dow n the process . The overtem perature controller cannot be cleared until the proces s co ols and an operator ma nually res ets the controller. It is im portant to use overtem perature controllers with a shutdow n device s uch as a con tactor to protect the heater process and personnel from dam age or injury.

I-63 

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Technical

Technical Information

Control Systems Selection Guidelines

cont d.)

Bulb & C apillary Ove rtempe rature Controls

have the same issues as mechanical temperature controls: Advantages: they are inexpensive and can switch significant power. Most are easy to set up. Disadvantages: Bulb and capillary controls do not fail safely. If the capillary tube with the fluid in it becomes pinched or broken, the control will not go into an alarm condition, which is a hazard. Knob shows nominal setting, but not process temperature.

Electronic Non-Indicating Ove rtem perature Controls: Advantages: Inexpensive, easy set up. If power is lost to the controller or the sensor breaks, the overtemperature controller will go into alarm and shut down the process. Disadvantages: Usually requires an external contactor to switch power. Knob has poor resolution for setting temperature, and there is no way to read process temperature.

Electronic Indicating Ov ertem perature Controls:

are microprocessor based units with many sensor choices, and the ability to

accurately view set point or process temperature. Advantages: More set up accuracy, variable deadband. If power is lost to the controller or the sensor breaks, the overtemperature controller will go into alarm and shut down the process. Disadvantages: Requires a contactor to switch the load. Set up more involved than for bulb and capillary units.

Lev el Controls.

If a liquid is being heated, and the possibility exists for the level to fall to the point where the hot section of the heating element could be exposed to air, a level sensor is suggested to prevent damage to area, heater and/or liquid. See the catalog for selection based on your fluid type. Level control should be wired so heater turns off if liquid falls below acceptable level. Environmental and S afety Considerations: Process controls, overtemperature controls, and accessories must be selected with the surrounding area in mind. Wet, dry, explosion hazard areas must be considered, as well as the ambient temperature range the equipment will see. Mechanical controls should not be exposed to temperatures above the control temperature range. Electronic controls are designed to operate above 32 F, and below a stated maximum, usually 120 or 140 F. See specific control for ambient temperature range.

o w er C

tr s  

For small loads (less than 20 amps) some bulb and capillary and electronic controllers can switch the heater directly. For larger loads it is necessary to use an external power controller. There are various mechanical and solid state power controllers available.

Types f P

er C o n tr o l s  

Me chanical C ontactors Mechanical contactors are similar to motor starters. They are capable of switching large amounts of power on an infrequent basis. If turned on and off at a fast rate (more than 1 or 2 times a minute), mechanical wear and contact erosion will require frequent replacement. Advantages: Low cost. High switching currents. They do not produce much heat from their operation. Disadvantages: Contactors are subject to mechanical wear, and produce electrical and mechanical noise.

Me rcury Displaceme nt Contactors Mercury displacement contactors (or mercury contactors) are similar in operation to above mechanical contactors, except mercury is made to move up and down a sealed tube by an external electromagnet, which pulls down a steel core when the coil is energized. Advantages: Little mechanical noise, long life, with faster on and off cycles (every 10 seconds) than regular mechanical contactors. Disadvantages: Contains mercury, a hazardous substance, not permitted in some plants. Mercury tubes may rupture during severe over current conditions, releasing the mercury. (Fast semi-conductor fuses minimize this possibility).

Snubbers To minimize electrical noise, snubbers should be connected across each contactor coil minimizing arcing of control relay contacts. A Snubber is an electronic circuit, which absorbs the inductive kick back of the contactor coil when it turns off. Environmental and S afety Considerations: Arcing contactor contacts may ignite flammable vapors. Mercury may be released from mercury contactors. I- 6

Technical

Technical Information 

Control Systems Selection Guidelines

cont d.)

SCR’s SCRs (Silicon Controlled Rectifiers) are devices used to switch power. Since SCRs are solid state devices with no mechanical moving parts, they are able to switch current quickly without wear. Some SCR devices can switch up to 600VAC at 600 amps. With this switching capability they are used to precisely control single or three phase heater loads. Many different “firing packages” are available to achieve desired results with varying load types and related conditions. “Zero-crossover firing” switches power at the zero voltage or the sine wave almost eliminating EMI and RFI. “Phase-Angle firing” switches anywhere in the sine wave and although it is electrically noisy, it is required for some loads i.e. tungsten, transformer driven load. SCRs have two major disadvantages over mechanical contactors. 1) SCRs tend to fail shorted (full on). A mechanical disconnect device and overtemperature controller are strongly recommended. SCRs CANNOT BE USED AS A SHUT DOWN DEVICE. 2) SCRs generate heat when current is passed through them (1.5 watts per amp or per leg). For example, an SCR switching a 100Amp load, with 2 legs of a three phase design will generate approximately 300Watts of heat. It is important to include cooling or ventilation in designs using SCRs. SCR power controllers come in many shapes and sizes. Solid State Relays are the simplest SCR devices. These are generally single phase, low current devices with few special features. More sophisticated and higher amperage SCR power controllers, sometimes called Power Packs, have more features and capabilities.

Zero Crossove r Firing Zero-crossover fired SCRs turn on at the zero voltage point of the sine wave. Switching at zero volts means no current is flowing when the switching occurs and therefore little conducted and/or radiated electrical noise is produced. This helps prevent problems with nearby computers and other instrumentation, which may be noise sensitive. Types of zero crossover control are: • On-Off • Time Proportional • DOT On– Off Zero-Crossove r Control  receives a signal from a remote device to turn on or off. Generally a

temperature controller will cycle it’s output to approximate a percent output. For example: for a 50% output the controller will turn on the SCR for 1/2 second and turn it off for 1/2 second. The signal from the controller can be a pulsed dc voltage, or a relay contact input.

Figure 8

Proportional Power Controller (Zero Voltage Switching DOT)

Time P roportional Zero-Crossov er Contro l receives an analog signal (i.e. 4-20mA) from a remote

controller or other device. The SCRs time-proportional firing package takes the 4-20mA signal and converts it into a ON and OFF time based on the cycle time. For example, the cycle time is 2 seconds, the signal received is 50%(12mA), the firing package will have the SCR turn on for 1 second and off for one second. DOT (dem and oriented transfer) zero-crossove r control

The SCRs DOT firing package t akes the 4-20mA signal from a remote controller. Demand Oriented Transfer (DOT) is a zero-crossover SCR which varies the on-off time to the smallest possible time base to provide superior resolution and minimum power supply disturbances. For example, a 50% power output can be one cycle on and one off. Considering the incoming supply is 60 cycles per second, the SCR can be turning on and off 30 times a second. DOT firing is the most accurate Zero-Crossover firing method. Zero-Crossover firing also ensures low electrical noise.

Figure 9 Phase Angle Firing

Phase Angle A phase angle control splits each half cycle into a percentage needed for the instantaneous load requirements. Phase angle firing is required for tungsten and transformer loads. Advantages: extremely tight control. Disadvantages: Electrical noise and power line harmonics are produced during operation. With these noise problems, even though phase angle control is tighter than zero-crossover control it is usually only used when required by the load type.

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F i g u re 1

I- 6

Technical

Technical Information

Control Systems Selection Guidelines (cont d.) Three P hase P ower Control Using S CRs 2 le g v s . 3 l eg –  “Legs” refers to the number of lines switched in a 3-phase SCR circuit. “Two legs” means 2 of the three lines are switched, and the third is passed through un-switched (hot). Advantage: 2 leg is cheaper than 3 leg switching, since only 2 sets of SCR’s are needed, not 3. Only 2/3 as much heat is produced by the SCR’s in a 2 leg vs. a 3-leg system. Two leg switching can only be used with zero-crossover SCRs and on Delta or 3 wire Wye loads. 3 leg for 3 phase loads –  3 leg control is required for any 4 wire Wye load and for any 3-phase angle fired applications. Environmental and S afety Considerations:

Power controls, and accessories must be selected with the surrounding area in mind. Wet, dry, and explosion hazard areas must be considered, as well as the ambient temperature range the equipment will operate in. SCR controls are designed to operate above 32 F, and below a stated maximum, usually 100 to 120 F. See specific SCR for allowable ambient. Heat produced by the SCR’s must be removed. This is usually done with ventilation, fans, air conditioners or heat sinks mounted on the outside of the enclosure. Even if the SCR has a built-in fan, ample air changes in the panel must be provided, perhaps by an additional fan, to keep inside of panel below maximum allowable ambient for the components inside, for the highest expected external ambient.

Choosing a Powe r Control Electrical Considerations Contactors must be selected for voltage and current of load(s). If you have three 3 phase, 30 Amp loads, for example, 3 small contactors may take up less space than one large contactor, and would be more cost effective. SCR’s should be selected / specified based on the voltage, total current of the load(s) and the number phases. For a 3-phase delta circuit a 2-leg unit can be used, for 3-phase 4 wire circuits, or phase-angle control, 3 leg SCR’s are required. Be sure to use I2T fuses (fast blow) to protect the SCR’s. Environmental and S afety Considerations:

Power controls and accessories must be selected with the surrounding area in mind. Wet, dry, explosion hazard areas must be considered, as well as the ambient temperature range the equipment will experience. Panels generally require internal heaters, if the ambient is below 32 F. In addition, the maximum ambient should be considered and taken into account. This is particularly important for SCR panels, since the SCR’s generate heat, which must be removed during operation. Panels should not be mounted where they will receive direct sunlight.

P ower C ontrol Pa nels Power Control Panels are assembled systems which combine temperature control, overtemperature control, contactors, SCRs and other components into a prewired complete control system.

Stock Panels Chromalox has a good selection of “off the shelf” stock Contactor, SCR and Heat Trace panels. Features include, NEMA 4X Fiberglas contactors of 40, 75, or 90 Amp rating. Optional temperature controls, overtemperature controls and disconnects are also available.

®

 enclosure,

S tandard Design Panels Chromalox has pre-designed panels of several series, both SCR and contactor, with NEMA 1, 4, 4X, and 7 ratings. Many choices of voltages, currents, branch circuit fusing and controls are offered. Consideration is given to heat dissipation, environments and safety requirements. Custom Design Panels Chromalox is ready to design and manufacture your custom panel as a variation of one or our standard panels or full custom from scratch. Many additional features are available. We can incorporate motor starter relays for pumps and fans, as well as use specific brand controls to meet plant specifications. Chromalox has a UL approved panel-shop and can also make panels to military specifications. Chromalox’ instrument, control and panel shops are ISO-9001.

Choosing a Pa nel Panel should be selected/specified based on the voltage, current, and number of circuits of the load(s). Panel must be compatible with the area classification (ex. NEMA 4) where it is to be located.

Loads , C ircuit Protection The National Electrical Code (NEC) requires load circuit protection for all circuits and branch circuits. HVAC heating applications further require that all sub circuits not exceed 48 amps. Advantages: Keeps wire sizes reasonable, and allows for more reliable operation. If one circuit shorts, the others can usually continue to operate, if fused separately. I- 6

Technical

Technical Information

Control Systems Selection Guidelines

cont d.)

Wiring Issues Chrom alox panels are compliant with the NEC . The installer is res ponsible for applying N EC and all local codes. The connection to the heater may require s pecial high te mperature wire at least w ithin se veral feet of the hea ter, to prevent w ire insulation damag e, and / or conductor oxidation.

Environmental and Safety Considerations: Panels and accessories must be selected with the surrounding area in mind. Wet, dry, explosion hazard areas must be considered, as well as the amb ient temperature range the equ ipment w ill operate in. Panels generally require an internal heater, if the ambient is below 2 F. In addition, the max imum am bient should be considered and tak en into account. This is particularly important for SC R panels, since the S CR s g enerate heat during operation. Panels s hould never be mounted wh ere they will receive direct sunlight. Outdoor insta llations require shading.

Building a Panel Choosing Controllers and Power Controls Temperature controls, overtemperature controls, and power controls must be chosen based on process temperature range, process speed, area classifi cation, ambient temperature, (minimum and maximum ), v oltage and current.

Heat and Cold Management  W hile he at is th e u s ua l pa ne l loa d, it is th e e ne m y ins ide of a p an el. This is es pecia lly tru e f or S C R pa nels . F an s m us t b e p rov ided t o re m ov e h ea t generated, and ensure that the temperature inside the panel does not exceed the maximum operating ambient for the power controls and other com ponents . For wet, dusty, or explosion areas, consider mounting the p anel in a clean, dry control room awa y from contam inants. There are different sta ndard models of Chromalox panels that are built with these cons iderations. All include specifi cations of maximum ambient tem perature outside the enclosure.

Layout Considerations Panel layout must follow NEC and local codes. Ample room must be provided for all components, and bend radii of the wiring. Door mounted components m ust clear sub-panel mounted components. W iring mus t allow for easy door opening for access. A disconnect s hould be provided to permit safe acces s to panel components for servicing. All Chromalox Panels meet N EC codes.

Environmental and Safety Considerations: Panels and accessories must be selected with the surrounding area in mind. Wet, dry, explosion hazard areas must be considered, as well as the amb ient temperature range the equ ipment w ill operate in. Panels generally require an internal heater if the am bient is below 3 2 F. In addition, the max imum am bient should be considered and tak en into account. This is particularly important for SC R panels, since the S CR s g enerate heat during operation. Panels shou ld not be mounted w here they w ill receive direct sunlight.

Chromalox® , Inc. is pleased to offer suggestions on the use of its products. However, Chromalox ® , Inc. neither assumes responsibil ity for any omissi ons or errors nor assumes liabil ity for any damages that result from the use of its products in accordance with information provided by Chromalox ® , Inc., either verbal or written.       N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

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Technical

Technical Information Thermal System Glossary 

 A  Absolute Zero – The lowest theoretical temperature. At absolute zero, a body would have no molecular motion of heat energy. Absolute zero is the zero point on the Rankine and Kelvin scale. (-273.15 C or-459.67 F)

Analog Set Point – potentiometer adjustment of the control setting Anneal - To relieve stress in a metal or glass material by heating to just below its melting point, then gradually cooling to ambient temperature. Annealing lowers tensile strength while increasing flexibility. Tubular heaters are annealed prior to forming.

Accuracy Calibration Accuracy – the potential error of a device compared to a physical constant or agency standard. Control Accuracy – maintaining a process at the desired setting. The errors or combination of errors in the entire system including the sensor, control, power, load and design inefficiencies effect control accuracy. Display Accuracy – the amount of potential error between a measured value and the control’s displayed value. Set Point Accuracy – the potential error between a measured value and the control setting.

ANSI – American National Standards Institute

Address – for digital communication between host computer and control, is a numerical value, typically between 1 and 255. The same address must be entered into both the computer program and the specific control to be addressed, or communicated with.

Automatic Reset (Integral) – the integral function of a control that automatically compensates for the difference between the set point and the actual process temperature. A signal moves the proportioning band up or down to correct for the droop or offset error.

Alarm – a control condition or function, indicating that the process is at a predetermined amount above and/or below the set point.

Automatic Tuning (of control parameters) – a control that calculates the optimum PID parameters with a built-in software algorithm to eliminate manual tuning efforts.

Alarm relay options – normally energized (relay energized when not in alarm) normally de-energized (relay not energized unless in alarm). Latching means a reset button must be pushed when the temperature drops below the alarm setting plus dead band. Alarm Type – typical choices for PID controls are: disabled, high, low, + deviation, -deviation, +/- deviation., and event (for ramp soak units.) Algorithm – a set of rules with a finite number of steps for solving a problem. Alternating Current (AC) – an electrical power system where the voltage reverses, alternating negative and positive. Typical frequency is 50 or 60 Hz. (cycles per second) Ambient Compensation – the ability of an instrument to compensate for changes in the ambient temperature so that the changes do not effect control accuracy. Ambient Temperature – the temperature of the immediate surroundings in which equipment is to operate. AWG (American Wire Gauge) – also known as B & S wire gauge. Standard system to specify the diameter of wires for both power and control circuits. The larger the gauge number, the smaller the wire diameter.

Anti-reset Windup – a feature in 3 mode (PID) controls which prevents the integral (automatic rest) circuit from functioning when the temperature is outside the proportional band. ASME – American Society of Mechanical Engineers. ASTM – American Society for Testing and Materials. Atmospheric Pressure (Standard) – Pressure exerted by the earth’s atmosphere on the objects within. Measured at 60 F (15 C), at sea level, standard atmospheric pressure is 14.7 psia.

Auxiliary Output – additional outputs for control of functions other than the primary control output, such as lights, buzzers, horns or gas purges that are triggered by the control alarm function. Auxiliary Setpoint – an alternate set point on some PID controls, which can be selected from a button or external signal. AWG – American Wire Gauge.

B Band and Nozzle Heaters – component heaters designed to heat cylindrical objects such as plastic extruders. A variety of sizes and constructions are available. Bandwidth – the total temperature variation measured at some point in the system, normally the process. Baud Rate – In serial communications, the rate of information transfer in bits per second. Must be set for the same value in the controller and the host computer program. Typical values are 1200, 2400, 4800, 9600, and 19200. The control, computer and wiring must be able to operate at the baud rate selected.

Ampere (amp) – the rate of flow of current in a circuit.

Bend Radius (minimum) – the minimum radius for bending a wire, heating element or heat trace cable, without damage.

Analog Indication – a meter with graduated scale and a pointer that moves to indicate process condition.

Blackbody a theoretical object that radiates the maximum amount of energy at a given temperature and absorbs all energy incident upon it.

Analog Output – a voltage or current signal that is a continuous function of the measured parameter.

Braid – a flexible woven covering, usually of metal wire, covering an insulated wire to provide a ground path (or shield) or to protect from mechanical damage.

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Technical

Technical Information Thermal System Glossary (cont'd.) Boiling Point – the tempe rature at which a subs tance in the liquid state transforms to the g aseous state. Com monly refers to the boiling point of water (1 0 C or 2 F at sea level). BTU – British T hermal Unit; the am ount of therm al energy required to raise one pound of water, 1 F . Bulb & Capillary – refers to thermostat cons truction which has a bulb fi lled with a fl uid in the process. The increasing heat forces the uid through a narrow tube into a bellows . The bellows actuates a snap s witch, at a temperature determined by the k nob setting which mov es the sw itch toward or away from the bellows. Bulkhead Threaded Fittings – ava ilable on tubular heaters, fact ory brazed, to allow heaters to be mount ed through the wall of a tank or duct, etc. Bumpless Transfer – The smooth, automatic transition from automatic control (closed loop) to manual control (open Loop). The control output is m aintained during the transfer. Burst Firing – a fast cycling control output, typically 3 -3 VDC, used in conjunction w ith a s olid s tate relay.

C Calibration – the process of adjusting an instrument s o that the indication is accurate com pared to the actual value. Calorie – the amount of t hermal energy required to raise one g ram o f w a te r 1 C a t 5 C Cartridge and Immersion Temperature Controllers – are mechanical Thermos tats w ith operation base d on the difference of expansion of different metals. Cartridge Heaters – cy lindrical heaters w ith leads exiting on e end. Mos t often inserted in drilled holes in platens and m olds to heat block s of metal. A variety of standard diameters, lengths and wattages are available, as w ell as s pecial lengths , electrical ratings , and lead wire options. Cascade – Control function where the output o f one control loop provides the set point for a second loop, which determines the control action. CE –  A m ark th at de s igna te s co m plianc e w ith Europ ea n U nion ( EU requireme nts f or products s old in Europe Celsius – (C entigrade) a temperature scale with 0 C defi ned as the ice point and 1 0 C as the boiling point of water at sea level. Ceramic Beads – beads of ceramic material, with various hole sizes, intended to insulate bare high tem perature wire, to prevent s hort circuits. Ceramic Fiber – a light w eight, low density fi ber, typically used as a high tem perature insulation or a refractory  Ceramic Post Terminal Insulators – used to cover the terminals of com mon s trip heaters to preven t personnel contact with electrical hazards. S old in pairs.

cfm – the vo lumetric fl ow rate of a liquid or gas in cubic feet per minute. Chatter – the rapid cycling of a relay due to t oo narrow a bandw idth in the control. Circuit – a complete or partial path over which current may fl ow. Circulation Heaters – heaters for fl uids or gass es consisting of an insulated pipe body with an immersion heater inside. Various sheath and pipe body m aterials are offered to heat a v ariety of mate rial to a range of temperatures. Mechanical thermostats are included on som e mod els. Options include mechanical or electrical controls, built-in sensors, baffl es, and AS ME design and certifi cation. Complete sk id mounted sys tems with panels are also available. Closed Loop Control – a control system in which process temperature changes are detected by a sens or. The feedback f rom the sensor allows the control to mak e adjustments f or accurate sys tem regulation.

Cold Junction Compensation – a tem perature sensitive device that prevents changes in the ambient temperature from affecting the cold junction of a thermocouple. Cold Length – the distance from the end of the sheath to the heated sec tion of a tubular or other similar heater Comfort Heaters – heaters, usually for the heating of areas to maintain comfort of the occupants. Generally not for use in areas above 1 0 F. A wide variety of types ( convection and fan forced) are ava ilable for use in ordinary, corrosive, and explos ion hazard areas. Common Mode Line Filter – a device to fi lter noise s ignals on both power lines with respect to ground. Common Mode Rejection Ratio – the ability of an ins trument to reject interference from a com mon v oltage at the input terminals  w ith relatio n t o g round. E xpres s ed in d B ( de cibels Compression Fittings – bul head fi ttings des igned for customer installation on round tubular heaters, to allow he aters to be mounte d through the wa ll of a tank , duct, etc. Conduction – the transfer of heat from one material at a given temperature to another m aterial at a low er temperature, wh ile in direct contact w ith each other Conductivity – the ability of heat or electricity to fl ow throug h a material. Constant Wattage – refers to a type of hea t trace cable having a constant wattage output regardless of the surrounding temperature. Continuity Check – A tes t that determines whether current can fl ow throughout the length of a circuit. Control Loop – the bas ic control loop of any autom atic control sys tem consists of: ) v ariable (process) ) sensor ) error detector (of control ) control ) fi nal control element (relay, SS R, S CR) ) temperature indication I-69

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Technical

Technical Information Thermal System Glossary (cont’d.) Control Mode – the m ethod in which the control restores the sy stem temp erature to set point. On/Off, proportioning, and P ID are the mos t common control modes. Control Type – options are direct acting (cooling) and reverse acting (heating). Convection – the transfer of heat from a s ource or higher temperature area in a gas or liquid by the m ovem ent and mixing of the m ass es. CSA – abbreviation for third party tes ting and approval agen cy, Canadian Standards A ss ociation C-UL – this is an acceptance of UL (U nderwriters Laboratory) approval of a product. Often accepted by cus tomers w ho w ould normally require CSA approval. CPS – Cy cles per S econd (See Hertz). Current – meas ured in amperes ( A) , is the fl ow of electricity. One ampere is one coulomb per second. Current Limiting – a m eans to limit the current delivered to a load by a pow er control device, usually an S CR Current Proportioning – a 4 -2 0 milliamp (typical) current output  w hich p rov ides a c urre nt proportio na l to th e a m ount of co nt rol required. Current Transformer – a transformer, usually toroidal (doughnut) shaped , designed to acc omm odate an electrical conductor, and pro v ide a re duce d, bu t lin ea r ou tp ut at a lo w er curren t, for ins tru m en t use. Typically speci ed by ratio i. e. 1 :1 Cycle Rate (or Cycle Time) – in a time proportioning control, the period (usually in seconds) of time that is required to complete one on/off cycle once temperature has settled at the center of the proportioning band.

D Data Logging – Recording a process variable over an extended period of tim e. Dead Band (differential) – is the difference in degrees between tempe rature control turn on an turn off. This pa rameter is for on-off controls. It also a pplies t o overtem perature controls. Default Parameters – The programming instructions permanently  w ritt en in m icropro ce s s or s oftw are Definite Purpose Magnetic Contactor – sim ilar to a motor s tarter relay, for use w ith on-off controllers for s low process es. Av ailable  w ith optio nal en clos ure s for g en era l, w et , and ex plos ion pro of are as Density – mas s per unit of volume, such as lbs./ cu.ft  Derivative – (See Rate) Deviation the difference between the selected value and the actual value Deviation Alarm – an offset value that follows the set point. If the set point is 3 0 F and the Deviation Alarm value is + 0 F (or 0 F), I-70

then the set point is changed to 3 0 F, the Deviation Value alarm  w ould b e 3 0 F p lus 0 F ( or 3 0 F) . S ee P roc es s A larm

Deviation Meter – the display of process temperature on meter that indicates d ifference of or deviation of the process tempe rature from the set point. di/dt – the rate of chang e of current vs . time. Filtering on large S CR units m ay be necess ary to prevent damag e from large current changes in small time periods Dielectric – an electrical insulator - a m aterial with low e lectrical conductivity. Dielectric Strength – an amount of v oltage that an insulating m aterial can withstand before an electrical break down occ urs. Differential – in an on/off control, the tem perature difference expressed in degrees between w here the control switches off and the control switches on. Differential Mode Line Filter – a device to fi lter noise s ignals between two power lines. Digital Indication – the actual process te mperature in indicated by LED or LC D display. Digital Set Point – the desired temperature v alue is s et by means of up-down pushbuttons or pushwheel sw itch DIN – Deutsche Industrial Norms, a G erman agency that s ets engineering stan dards. Control panel hole size cutouts are typically based on DIN dimens ions Diode – A de v ice th at allow s curren t t o fl ow in o nly one d irec tio n. Direct Current (DC) – an electric current fl owing in one direction. Disconnect – a control panel mounted main switch, which provides a me ans to turn off powe r in the panel before opening the door for servicing. Most disconnects do not provide overcurrent protection. This mus t be provided upstream using fuses or circuit break ers. Dishwasher Heaters – immersion heaters with terminal housing and built-in controls, des igned for use in comm ercial dishw ashe rs DOT (Demand Oriented Transfer) – an SCR power control system using the sm allest time base possible. For example, 2 % output  w ould b e 1 cy cle on, a nd 3 cy cle s of f. Drift – a change in a value over a long period due to changes in factors such as ambient temperature, time or line voltage. Droop – in time proportioning controls, the difference in temperature between the set point and where the sy stem temperature stabilizes. Corrected by automatic or manual reset. Drum Heaters – fl exible heaters designed to heat or maintain the temperature of standard , 1 , 3 0 and 5 gallon drums. A selection of ratings are available, some with thermostats. Dry Well Heater – a heater des igned to be ins talled in a dry area, usually a pipe, to heat the pipe, with the ultimate purpose of h eating liquid s urrounding the pipe.

Technical

Technical Information Thermal System Glossary (cont'd.) Dual Output – the primary control output w ill regulate the p rocess tem perature. A second ary control output will be utilized for process cooling or as an alarm. Duty Cycle – the ratio of on time to on tim e plus off time, express ed as a percentage. dv/dt transient protection – fi ltering to limit voltage vs . time presented to an S CR . Helps protect SCR s ag ainst transient voltages.

E Efficiency – the amount of us eful output versus energy input, express ed as a percentage. Electric Stud Heater – a long cy lindrical heater designed t o be inserted into the hollow bolts of large machinery to obtain “ shrink t tightness” when the bolts cool. Electromagnetic Interference (EMI) – electrical and m agnet ic noise” than can be generated when s witching A C pow er. EMI can interfere with the operation of microproces sor bas ed controls. Element Clamps – cast iron clamps are offered to clamp s trip and ring heaters to s urfaces for conduction heating of tank s, etc. Emissivity – The ratio of radiant energy em itted from a surface compared to the radiant energy em itted from a black body at the sam e temperature. Endothermic – a process is endothermic when it absorbs heat. Enthalpy – the sum of the internal energy of a body and the product of its volume multiplied by the pressure used to evaluate the energy change occurring when a vapor or gas is heated. Expressed in units of Btu/lb. or Joules/gram.

F Fahrenheit – a temperature scale with 3 2 F defi ned as the ice point and 2 2 F as the boiling point of water at sea level. Flanged Immersion Heaters – imm ersion heaters w ith mounting anges ( AN S I standard and others) . Most offer a choice of terminal housings for various environments. Optional sheath thermocouples are also av ailable. Flexible Heaters – available in many standard sizes and ratings, mos t are cons tructed of s ilicone rubber, with internal winding. S pecials with accessories such as thermos tats, cords and plugs are available, as well as unique shapes. Flow Rate – speed or velocity of fl uid mov ement. FM (Factory Mutual Research Corporation) – a third party approv al agency, which tests and approves equipment for service in various areas and conditions. Form A Relay – Single pole, single throw relay with Normally Open (N O) and com mon contacts. W hen coil is energized, the contacts  w ill clo s e. Form B Relay – Single pole, single throw relay with Normally Closed (N C) and common contacts. Contacts are open when coil is energized. Form C Relay – S ingle pole, double throw relay w ith Normally Open (N O), Normally C losed (NC ) and comm on contacts. Can be selected as Form A or Form B contact. fpm – ow v elocity in feet per minute fps – ow v elocity in feet per second.

Error – the difference betwee n the correct value and the reading or display value.

Freezing Point – the temperature where a material changes from a liquid to a solid.

Exothermic – a process is exothermic when it generates heat.

Frequency – the number of event occurrences or cycles over a specifi ed period of time.

Explosion Proof Strip Heater – used to heat by conduction in areas  w ith explo s ion haza rds

Fuse – A de v ice th at interru pts po w er in a c ircuit w he n a n o v erlo ad occurs.

Explosion Proof Terminal Housing (or Enclosure) – an enclosure, housing , or panel which will contain a internal gas explosion. This prevents an explosion from setting off surrounding area. Housing contents must not produce surface temperature which would ignite amm able gases or vapors in the vicinity.

Fuzzy Logic – A n a rtifi cial int ellig ence te chnique th at allow s cont rol decisions to be m ade upon approximate or incomplete information. It is a continuous decision mak ing function that can prevent initial overshoot and set point differentials.

Extension Wire – w ire in te nded to co nnec t a s ens or ( ty pically a thermocouple or RTD) to a panel or control. Thermocouple wire mus t be same type as TC (J for J ). RTD wire may be copper

G

External Interlock – provided on most Chromalox panels, the interlock is a jumper, which turns off the load w hen interrupted. Typically connected to a fl ow or press ure sw itch for mov ing sys tems to protect against a no fl ow condition.

GFCI – (G round Fault Circuit Interrupter) – an electronic circuit  w hich m on itors th e c urre nt ow ing fro m a c onduct or t o a g rou nd reference. When the current exceeds a predetermined value, the GFC I shuts the circuit down.

Event – a programm able On/Off output us ed to sign al peripheral equipment or a process

GIGA – the prefi x for one billion (G) gph – the volum etric ow rate in gallons per hour I-71

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Technical

Technical Information Thermal System Glossary (cont'd.) gpm – the v olumetric fl ow rate in gallons per minute. Ground – the electrical line having the s ame pot ential as the s urrounding earth; the neg ative s ide of a DC powe r supply; the reference point for an electrical sy stem Grounded Junction – A th erm ocou ple junct ion in w hich t he s he at h and conductors are welded together forming a completely sealed integrated junction.

H Heat – thermal energy expressed in Calories, Btu’s or Joules. Heat Balance – proper sizing of the hea t source to the requireme nts of the sys tem (including heat losses) Heat Exchangers – metal tubes or plastic coils designed to heat or cool solutions by immersion, with a fl uid (or steam) circulating through the coil to obtain the des ired effect.

Heat Transfer Systems – consist of circulation heater(s), pump, control panel and related item s, ready to conne ct to your s ervice and process . Oil and water sy stem s are available, in many s izes with a host of features and access ories. Helically Coiled Resistance Wire – a coil of Nichrome w ire, wound in a helix, which is the resistance w inding of the heater. Hertz – units of expression for frequency, measured in cycles per second. High Temperature Wire – special wire with high tem perature insulation and nick el or nick el plated copper conductor. Can w ithstand higher temperatures than plastic insulated copper conductor wire used for g eneral connections. Do not us e tin plated copper lugs on high tem p wire. They w ill oxidize and fail. High t emperature terminations require special nick el or sta inless ste el lugs , if lugs are used. Hi-Pot Test – the application of a high v oltage to an electrical conductor to test the s urrounding insu lation.

Heat of Fusion – the amount of energy required to change one pound of a mat erial from a s olid to a liquid without an increase in tempe rature. Express ed in Btu/lb.

Hopper Heaters – modular heaters, cons isting of tubular heating elements mounted to a m etal plate, for attachment to hoppers. These are used to k eep the walls above a critical tem perature to prevent contents from stick ing to or attack ing the hopper

Heat of Vaporization – the amount of energy required to change one pound of a m aterial from a liquid to a v apor without an increase in tempe rature. Express ed in Btu/lb.

Humidity Transmitter – an electronic device which provides a 4 -2 mA signal based on the relative humidity s ensed by the probe.

Heat Offset – for som e PID controllers; allows the creation of a dead area where neither heat nor cold is on, to prevent t he process from oscillating between heat and cool. Saves energy. Heat Sink – in power control, an array of plates or fi ns, us ually aluminum, which conducts heat away from the power control devices (S CR s) and dissipates the heat by free or forced convection Heat Tracing – heat applied to pipes or tank s, to replace heat lost through the insulation to the ambient. Heat Transfer – a process of thermal energy fl owing from one body to another. ) C onduction: the transf er of heat from one particle of matter to another. ) C onve ction: the transfer of heat from one part of a particle to another by the mixing of the warm er particles w ith the cooler ) R adiant: the transfer of heat from one body to another as the result of the bodies em itting and absorbing radiation energy. Heat Transfer and Release Coating – a compound designed to be applied between heaters and the surfaces being heated to improve heat transfer. Also mak es cartridge heaters easier to remove from drilled holes. Heat Transfer Fluid Vaporizer – a vaporizer for heat transfe r fl uids, to obtain improved process heat transfer by recovery of the heat of  v ap oriz at ion Heat Transfer Medium – a g as, liquid or solid through which heat ows from the heat source to the wor I-72

Hysteresis – the temperature sensitivity designed into the on/off control action between the on and off switching points. Expressed in percentage of control range. Also k nown as dead band.

I Ice Point – the temperature where pure water freezes ( 0 C or 3 2 F). Immersion Heaters – heating elements des igned to heat a fl uid or gas by direct contact. Impedance – the total opposition in a circuit to the fl ow of alternating current. Measured in ohms and represented by Z” Infrared – or radiation is the exchange of energy by electromagnetic  w av es . The inf rare d s pe ctrum ex te nds fro m the d ee p re d e nd of th e  v is ible s pect rum to the m icrow av e reg ion of th e ra dio s pe ct rum , The portion adjacent to the vis ible spec trum is of importance to heating Radiant heat transfer can be very effi cient in directing energy from the heat s ource to an object. Insulation, Electrical – a substance which surrounds an electrical conductor, to prevent current from fl owing to or leak ing to ground or to other conductors. Insulation Resistance – is the resis tance of an ins ulator to current ow from a conductor (typically a heating element w inding) to ground (the sheath). U sually meas ured by the application of a v oltage, and measuring the resulting current. The resultant resistance,  w hich is ex pres s ed in o hm s , is ca lcu lated by the f orm ula : R = V / I.

Technical

Technical Information Thermal System Glossary (cont'd.) Insulation, Therma Insulation, Thermall – a material material which reduces reduces heat fl ow from heated areas or objects to colder colder objects objects to conserv e energy improve performance, or prevent operator contact with hot objects.

Liquid Level Control – detects liquid liquid level level below a reference depth. Can be us ed for replenishm replenishm ent or to turn off a heater to prevent damage.

Input Scaling – all allows ows PID control to be adjusted adjusted to dis play inputs from transm itters (i.e. humidity), in appropriate appropriate engineering units.

Load – the electrica electricall demand of a process expr express ess ed as wattage, amps or resistance (ohms).

Integral – (S ee Automatic Automatic Reset). Intrinsic Safety Barriers – devices that limit current voltage and total energy delivered to a se nsor or other instrum instrum ent located in a hazardous area. Intrinsically Safe Equipment and Wiring – products that are not capablee of releasing pabl releasing s uffi cie cient nt energy in a circui circuitt to ignite a fl amm abl ablee atmosphere in a hazardous area.

M Manual Reset – the adjustm ent on a proportional control which shifts the proportioning proportioning band in relation relation to the s et point to eliminate droop or offset errors.

Isothermal – a process or area area that m aintai aintains ns a constant temperature.

Mass Flow Rate –  w eig ht of a s ub s ta nc e fl ow ing pe perr un it o f t im e past a specifi c cross cross -section -sectional al area area within within a sys tem.

 J

Maximum Allowable Load Resistance – the maximum resistance (in ohms ) into which a control can deliver deliver specifi ed current. current. Us uall uallyy specifi ed for mA outputs, and is limit limited ed by inter internal nal contr control ol supply voltage.

unit of thermal thermal ener energy. gy. 1 J oul oulee equals equals 1 ampere Joule – the basic unit pass ed through through a resistance resistance of 1 ohm for 1 second.

Junction – A thermo couple junction junction is the point at which two alloys are joined. joined. A ty pical thermocou thermocou ple circuit circuit would hav e a m easuring and a reference junction. junction.

Measuring Junction – the thermocoup le junction junction at the point of meas urement in in the process process Mechanical Relay – an electromechanical device that completes or break s a circuit circuit by clos ing or opening electrical electrical contacts.

K 

Mega – the metric prefi prefi x for one milli million on (M

Kelvin – the unit of absolute or thermodynamic temperature scale. Zero Kelvin is abs olute zero, where all molecular activity s tops. N o s ym y m bo bo l is us u s ed ed . 0 C = K; 0 C = K. Kilo – the metric metric pre x for one one thousand (K) Kilowatt (kw) –

minimum temperatur temperaturee Mean Temperature – the maximum and minimum average of a process at equilibrium.

0 w at a t ts ts o r

2 B tu tu pe pe r h ou ou r

Kilowatt Hour – electri electrical cal unit unit of energy energy expended by one k il ilowatt owatt in one hour.

L Lag – the time delay from applicati application on of heat until the proces proces s reaches tem perature or the delay delay in a controller responding to a temperature change. Least Significant Digit – The digit farthest t o the right in a display. Light Emitting Diode (LED) – a solid state device which produces light li ght from the fl ow of electric electric current current through a sem iconductor These are individual indicating lights or segmented readouts used to display temperature. Linearity – the compliance of an instrument’s response to a straight line.

Mercury Contactor (Mercury Displacement Relay) – a m echani echani-cal relay relay w ith mercury as the c urr urrent ent carrying conductor. They are fast er er,, quieter, quieter, and last longer than conv entional mechanical contactors. Contains mercury, a hazardous substance, not permitted in some plan plants. ts. MI Cable (Mineral Insulated Cable) – refers to metal sheath heat trace cable, having internal mag nesium oxide insulation between the conductor(s) and the sheath. Specially suited for high temperature operation,, and is m echanicall operation echanicallyy rugged. A ll MI cables are made t o order

Micro – The metric prefi x for one millionth millionth Microamp ( one millionth millionth of an amp) amp) Micron – (one m ilillilionth onth of a met er). central processing processing unit (C PU ) that performs Microprocessor – The central the logic operations in a micro-computer system. The microprocessor in a process or instrument control decodes instructions from the stored program, performs algorithmic and logic functions, and produces prod uces s ignal ignalss and comm ands.

Milli – The metric prefi prefi x for one thousandth

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Milliamp – (one thousandth of an amp). Millivolt – (one thousandth of a volt)

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Technical

Technical Information Thermal System Glossary (cont'd.) Moisture Resistant Terminal Housing – a terminal housing designed to meet the req requir uirements ements of NEM A 4 . Chromalox Chromalox types E2 and E4 meet these requirements. requirements. MOV Protection – S CR pro protecti tection on provi provided ded by a Metal Oxide Oxide VarisVaristor (MOV ), w hic hichh clamps v ol oltages tages at limits limits to stay belo below w cri critic tical al S CR fai failur luree values.

N NEC (National Electrical Code) – regul regulati ations ons and specifi cati cations ons for  w iring as pu publis blis he d b y th thee N at ion ional al F ire P rot ec ectio tio n A s s oc iat ion ion,, Inc Electrical Manufacturer’s Manufacturer’s As sociation NEMA – Nat ional Electrical

Noise – undesirable electrical electrical interference interference on the s ignal wires. Noise Suppression – a dev ice used to reduce electrical interfer interference. ence. Normal Mode Rejection Ratio – the ability ability of an instrume nt to reject rej ect interfe interferenc rencee of the line line freq frequency uency (5 -6 Hz) across the input input terminals.

Over-the side Immersion Heaters – immersion heaters desig ned for use in open top tank s. A wide variety of sheath materials and coatings are available available to heat mos t solutions Ris ers to terminal housings housings are provided, as well as optional mechanical thermostats for some models.

Overshoot – excursion of temperature above the set point.

P Percentage Timing Input Controllers – are motor driven adjustable duration cam devices. These provide an adjustable duty cycle, for a time time base of 1 5 or 3 0 second seconds. s. Us eful for inten ntensity sity (open loop) loop) control. Not for use with tungsten quartz radiant heaters. Phase – time bas ed relationship relationship between a n intermittent intermittent function and a reference. Electrically, Electrically, the express ion is in angular degrees to des cri cribe be the v oltage or current relationship relationship of two alternating  w av ef orm s

NPT – National Pipe Thread

Phase Angle Control – S CR ri ring ng m ode in in which which the SC R’ R’ss are turned on for a portion portion of each half cycle. Neces sary for high high inrush and/or inducti inductive ve loa loads, ds, s uch as tungsten (quartz lamp) lamp) heater heaterss and transformers.

O

Phase Proportioning – a tem perature control control form form w here the power supplied to the process is controlled controlled by limiting the phas e angle of the line line voltag e.

OCE (Open Coil Element) – heater heaterss designed to be installed installed in 2 or 3 inch customer- supplied supplied thread threaded ed schedule schedule 4 0 dry well pipes pipes to heat liquids liquids w ith the heat transferred through the pipe w all alls. s. Provides low watt density on the pipe for viscous fl uid uids, s, and allows allows for heater replacement replacement w ithout draining draining the tank . Ava il ilable able terminal housings provide easy connections to heater with high temperature  w ire. N ot fo r us e in ex explo ploss ion ha haza za rd a rea s Offset – the difference in in tem perature between the s et point and the actual process temperature. OHM – the unit of electric resistance. On-Off – a control whos e action is full on or full off. Open Coil Elements – elements with the Nichrome resistance wire exposed. Designed to heat by radiation and/or convection. Open Coil Oven Elements – ri ribbon bbon wound ope n coil elements designed specifi call callyy for use in ovens. Open Loop Control – a control control sy stem w ith no sensing feedback Open Sensor Output Command – for some PID controls, allows selection of shut down or switch to pre-assigned power output (i.e. ), in in the the event event of an an open open sensor sensor Output Limit – for some PID controls, allows selection of a maximum percent of full power. Useful of heater is ov ersized, or for fas t heat up followed by close c ontrol. OSHA – US Gov ernment agency, Occupatio Occupational nal Safety and Health Health  A dm inis tra tio n ( or A g en cy . S pe cifi es an andd e nf orce s s af et y in t he  w ork pla place ce I-74

PID – three mode tem perature control– control– proporti proportional, onal, integral integral (automatic reset), derivative derivative (rate). Polarity – having two oppositely charged poles; one positive, one negative. Potting – The sealing sealing of com ponents with a compound such as epoxy to prot protect ect against m oistur oisturee and other contaminants. contaminants. Process Air Heaters – component heaters or complete ass embli emblies es for heating low pressure, high volume air for processes. Single elements el ements of 5 watts to duct duct heate heaters rs of w are in incl clude udedd in in the the selection. Process Alarm – a fi xed alarm alarm or secondary set point value indeindependent of the primary set point. Should a process value exceed this  v alu e, an ala rm co nd nditio itionn w ou ld re g is te r. heaterss pro providi viding ng a variet varietyy of wav eProcess Radiant Heaters – heater lengths of radiant energy for heating processes, drying parts, freeze protection, etc. Many types and sizes are available. indicated v alue of the parameter being me aProcess Value – the indicated sured/controlled.

Process Variable – the parameter being c ontrol ontrolled led or meas ured such as t emperature, relative relative humidity, ow, level, press ure, etc. proportional band) the tempe rature band Proportioning Band – (or proportional in degrees within which a c ontrol’s proporti proportioning oning function is active. The width is usually adjustable, and is expressed in degrees or as a percent of span.

Technical

Technical Information Thermal System Glossary (cont'd.) Proportioning Control Mode – w he n p roc roces es s te m pe perat rat ure ap ap-proaches s et point and enters the proportioning proportioning band, the output is switched on and off at the established cycle time. The change in power to the load provides a throttling action which results in less tem perature overshoot. This cycling w il illl continue until until on and off times are equal. Protection Head – a junction box for the protection protection of the sens or to extens ion wire connection. connection. Protection heads can provide m echanical, moisture, and ex plosion area protection. psia – pounds per s quare inch inch abs olute. Press ure reference reference to a  v ac uu uum m psig – pound per square inch gauge. Pressure reference to ambient air press press ure.

Q Quality of Steam – the relative relative a mount of liquid liquid present in s aturated steam as a percent percent of the the total total weight weight.. The The quali quality ty of steam is is 1 less le ss the per percent liq liqui uid. d. Dry Dry s atur aturated ated steam steam has a quality quality of 1 Quartz Lamp Radiant Heater – a heater in a refl ector ector,, using a tungs ten fi lament quartz tube heater for the radi radiant ant source. The best source when the heater must be able to be turned turned off quickly when the line line stops. Intensity Intensity control mus t use phase angle fi red SCR s.

R  Ramp – a programmed rise in temperature. Range – an area between two limits in which a measurement or control action action tak es place. Typically Typically expres sed in upper and lower limits. Rankine – an absolute temperature scale based upon the Fahrenheit scale with 0 between the ice ice point point and boi boili ling ng point point of water. water. 0 F = 4 59 67 R Rate (derivative) – a control function function that me asures the rate of increase or decrease of the system temperature and brings the control into an accelerated proportioni proportioning ng ac tion. This This m ode prevents an overshoot condition at initial heat-up and with system disturbances. Rate Time – the interval interval over w hic hichh the s ys tem tem pera perature ture is is sampled for the derivative function. controllers, ers, an exter external nal -2 0 mA s ignal ignal,, Remote Setpoint – on some controll or similar, similar, will change the set point of a control. Good fo r remote computer sys tem control or cascading.

Repressed Bends – requir required ed w hen a tubular heater is is be nt to tighter radius than permitted for customer bending. Repress dies restore the internal compaction of the magnesium oxide to prevent voids,  w hic hichh m ay res ult in p rem at ature ure he heat at er f ailu ailure. re. electric curren currentt m easured Resistance – the resistance to the fl ow of electric in ohms ohms

Resolution Sensitivity – the amount of temperatur temperaturee change that mus t occur before the control will actuate. It may be express ed in tem perature or as a percentag e of the control’s control’s s cale. Response Time – In analog instruments , the time required for a change of the measured quantity to change the indication. In sensors, the the time time requi require redd to reach reach .2 % of the the step change. change. Retransmit Output – analog output scaled to the process or the set point value. Ring and Disc Heaters – component heaters which are fl at and circircular.. They are us uall cular uallyy us ed to heat by clamp on conduction. Variety of s izes offered allows allows for nes tin ting. g. RS232 or RS 422-485 Input/Output Signal –  A s eria l int erf ac e suitable for connection between a digital control and a persona l com puter puter,, a hos t com puter or printer RTD – a tem pera perature ture sensing probe of fi nely wound platinum platinum w ir iree that has a linear linear resis resis tance chang e for a corresponding corresponding tempe rature change. The resistance incre increases ases as the temperatur temperaturee rises rises . A base resistanc re sistancee of 0 ohms at 3 2 F is is the indu industry stry (DIN) standar standard. d.

S Saturation Temperature – the boiling tem perature of a liquid liquid at the existing existi ng pre press ss ure. SCFM – Vol  Volumetr umetriic fl ow rate rate in in cubi cubic feet per minu minute te at 6 0 F (1 5 C) and standard atmospheric pressure. SCR – S il ilicon icon Controll Controlled ed R ecti er Secondary Insulating Bushings – porcelain bushings designed to allow all ow certain strip heaters to b e electricall electricallyy isolated from g round,  w he henn u s ing on hig he r v olt oltag ag es fo r air he at ing . The T he he heat at er t ab abss m us t be punched at the factory factory to accomm odate the bushings bushings Self-Regulating – refers to a type of hea t trace cable, which has a decreased watta ge output for increasing temperature. Self-tune – an internal program in s ome PID controllers, controllers, wh ich allows all ows the control to experience experience the proces s a nd internally internally calculate parameters to obtain good process control operation.

feature on som e S CR uni units, ts, permitting permitting the Remote Shutdown – a feature shutdown of output from a remote contact opening or closing.

Serial Interface – the hardware and wiring to connect control(s)  w ith dig ita itall co m m un ica icatio tio ns to a c om pu te ter. r. Typic Ty pical al c ho ice icess are R S 2 2 ( s in in g le le d ro ro p) p) , R S 4 , 8 ( m u ltlt i-i- dr dro p) p) .

Repeatability – the ability ability to give the sam e output or measurement under repeated identical conditions.

Sensor Breakdown Protection – circuitry which ensures safe process shut down in the event of s ensor failure. failure.

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Technical

Technical Information Thermal System Glossary (cont'd.) Sensor Selection – a menu or hardware feature on mos t indicating controls which allows selection of a number of thermocouple types, RTD’s and /or other sens ors

Specific Heat – the ratio of thermal energy required to raise the temperature of a m ass of material 1 degree to the thermal energy required to raise an equal mas s of w ater 1 degree.

Serial Communications – A m et hod o f t rans m itt ing data betw ee n devices.

Speed of Response – time needed for a tem perature change occurring at the s ensor to be t ranslated into a control action.

Set Point – control sett ing to achieve or maintain tempe rature.

Spring Loaded – refers to sensor probes designed for use in thermowells. The probe has a spring, which forces the tip of the sensor to mak e g ood contact with the inside end of a properly chosen thermowell.

Screw Plug Immersion Heaters – immersion heaters, which mount  w ith a s cre w plug , t y pic ally w ith a s ta nd ard N P T t hre ad . M os t h av e an available selection of terminal housings for various environments. Some also include built-in mechanical thermostats. Shape Factor – in radiant applications, the am ount of energy received by the targ et relative to heater rating and distance to the target. Sheath – the outer shell of a heating element, usually m etal. Typical materials are: copper, steel, sta inless ste el alloys , and others. Provides mechanical protection and a ground path. Sheath Length – the length of the sheath measured without the terminals o r protruding term inal pins. Typically held within one percent for Chromalox tubular heaters. Shield – mat erial surrounding a conduct or(s ) to prev ent interference of electrostatic or EMI from ex ternal sources. Shorted SCR Detection – circuitry in som e S CR s to detect a shorted SC R in a power control module. Us ually the output can be an alarm to alert operator that unit needs serv ice. Shunt Trip – a coil, designed to turn off the m ain disconn ect on a panel, when energized. Typically used for large SCR panels, to drop the load if high limit is reached. Single End Tubular Heaters – tubular heaters with both electrical connections located at one end of heater. Simp li es w iring. Slide Wire Feedback – A pote ntiom et er t ha t v arie s res is ta nc e in response to a valve position. This provides valve position information to the valv e controller Soak – To raise the tem perature of a metal object in a heated environment to produce a m etallurgical change. A lso, a pre-programm ed time to provide a set point to a process , as us ed in a ramp-soak program. Soft Metal Melting Pot – an open top vess el designed to melt solder, tin and/or lead. Soft Start – reduces v oltage on initial start-up which reduces pow er to the heaters. Solid State Relay – a s olid state sw itching device which completes or break s a circuit electrically with no m oving pa rts. Span – the difference between the upper and lower limits o f a controller’s range. Specific Gravity – the ratio of mas s of any material to the same  v olum e o f p ure w at er a t 4 C I-76

Stability – the ability of an ins trument or sens or to maintain a constant output when a constant input is applied. Standard – reference point from w hich references or calibrations are made. Steam Boilers – automa tically prov ide a source of steam for processes or other uses. Boilers are available in a wide variety of sizes and s tyles. A ccessories include automatic blowdown, condensate return sys tems , steam s eparators and m ore Strip Heaters – heating elements with a rectangular cross section, usually us ed to heat objects by clamp on conduction or heating air by free or forced conve ction. Super Heating – the heating of a liquid abov e its boiling t emperature without changing to a gas eous s tate; or the heating of a g as considerably abov e the boiling tem perature. Surge Current – a higher than nominal current of short duration occurring w hen pow er is initially applied to loads s uch as self regulating heat cable and tungsten lament quartz radiant heaters.

T Temperature Gradient – the range of tem perature variations at v arious phy sical locations throughout a thermal sys tem. Tera – the prefi x for one trillion(T) Terminal Pin – a pin in the end of tubular and similarly cons tructed heaters to which the resistance winding is attached. The pin extends out of the heate r and is attached to a terminal to facilitate wiring. Terminals – the me ans to att ach wiring to heaters. For tubular heaters, a wide variety are available to accomm odate wires, lugs, or 1 /4 inch push on connectors. Thermal Conductivity – the property of a m aterial to conduct heat. Thermal Expansion – an increase in size due to an increase in temperature. Thermal Lag – the time delay in the distribution of heat throug hout a thermal system.

Technical

Technical Information Thermal System Glossary (cont'd.) Thermal System – a s eries of components arranged and des igned to provide heat. The four elements or components compromising a Thermal S ys tem are: ) work or load ) heat source ) heat transfer medium ) control sys tem Thermistor – a temperature sensing probe manufactured of a mixture of metal oxides then encapsulated in epoxy or glass. A large chang e in resis tance is exhibited proportional to a chang e in temperature. The resistance usually decreases as temperature rises. Thermocouple – a temperature s ensing probe consisting of the junction of two dissim ilar metals w hich has a m illivolt output proportional to the difference in tempe rature between the “ hot” junction and the lead wires (c old junction). Thermowell – a closed-end tube into which a temperature sensor is inserted to isolate it from the e nvironment.

 V  VDE – an independent, German th ird party tes ting organization for product safety. Viscosity – the inherent resistance of a s ubstance to fl ow  Voltage – an electrical potential, which is m eas ured in volts.

 W  Wattage – a unit of me asurem ent of electrical power. In a resistiv e circuit, VI = W (S ee Ohms Law formulas). Watt Density – the rated wattage of an element per unit of surface area. Usually expressed in watts per square inch.

Thin Blade Heaters – tubular type heaters having a 1 / 4 / by 1 inch cross section. Av ailable in single or three phase m odels

Welded – one comm on method of attaching s ensor probe to threaded hub. Welding produces a moisture proof, mechanically strong bond.

Touch Safe Design – optional shields av ailable on s ome S CR power control modules, reduce the poss ibility of pe rsonnel coming in contact with high voltage.

Z

Transducer – a device that converts a measured variable into another form which is the trans ducer’s outpu t. A thermocouple transforms heat to a millivolt output.

Zero Voltage (or Zero Crossover) Switch ing – completing or break ing of a circuit when the voltage w ave form crosses zero voltage.

Transmitter – a device used to transmit temperature data from the sensor. Tubular Element – cylindrical component heating element made  w ith a m et al s he at h, en clos ing a m ag ne s ium ox ide s urro unde d Nichrome resistance winding. C ross section may be round, heart shape or fl at pressed.

U  Undershoot – excursion of temperature below s et point. Underwriters’ Laboratories (UL) – a third party approval agency for components and fi nished products. Ungrounded Junction – A t hermocouple junction fully insulated from the sheath. User Selected Security Code – a feature on some PID controls, allows the s election of an unique code, if the default codes are compromised.       N       L      O       A      I       T       C       I       A       N      M       H      R       C      O       E      F       T      N       I

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