Exchanger Piping

BECHTEL CORPORATION ENGINEERING – PLANT DESIGN DESIGN GUIDE EXCHANGER PIPING 3DG-P22-00004, Revision 002, 2002 July 23 Reason for Issue: Issued for for Use Prepared by: B. Tarr Checked by: P.R.Wood Approved by: R. Fox INTRODUCTION This Engineering Design Guide explains the different types of heat exchangers that are most commonly used in facilities. It addresses locations, elevation requirements, nozzle locations, exchanger supporting, associated piping supports, maintenance and operation access.

Electronic documents, once printed, are uncontrolled and may become outdated. Refer to the electronic documents in BecRef for current revisions.

Bechtel Confidential © Bechtel Bechtel Corpora Corporation tion 2002. 2002. Conta Contains ins confidentia confidentiall and/or and/or proprieta proprietary ry informa information tion to Bechtel Bechtel and and its affiliated affiliated companies companies which which shall shall not not be used, used, disclosed or reproduced in any format by any non-Bechtel party without Bechtel’s prior written permission. All rights reserved. 3DG-P22-00004-002 Page 1 of 52

TABLE OF CONTENTS INTRODUCTION .................................................. ........................................................................... .................................................. ...........................................1 ..................1 LIST OF FIGURES ............................................... ........................................................................ .................................................. ...........................................5 ..................5 1.0 1. 0

PURP PU RPOS OSE E ............................................... ........................................................................ .................................................. ...............................................7 ......................7

2.0

EXCLU EX CLUSI SIONS ONS......................... .................................................. .................................................. .................................................. ....................................... ..............7 7

3.0

DISC DI SCUS USSI SION ON...................... ............................................... .................................................. .................................................. ...........................................7 ..................7

3.1 3. 1

SAFE FETY TY...................... ............................................... .................................................. .................................................. .................................................. ........................... 7

3.2 3. 2

OPER OP ERAT ATIO ION N ................................................ ......................................................................... .................................................. ...........................................7 ..................7

3.3

MAIN MA INTEN TENAN ANCE CE...................... ............................................... .................................................. .................................................. ....................................... ..............7 7

4.0

TERMI TER MINOL NOLOGY OGY .................................................. ........................................................................... ................................................... ................................... .........7 7

5.0

BASICS BAS ICS OF HEA HEAT T TRANS TRANSFER FER ......................................................................................9

6.0

TYPES TYPE S OF EXC EXCHAN HANGERS GERS ...........................................................................................10

6.1 6. 1

SHEL SH ELL L & TUB TUBE E ............................................... ........................................................................ .................................................. ..................................... ............10 10

6.2

DOUBLE DOUB LE PIP PIPE E EXC EXCHAN HANGERS GERS.....................................................................................18 .....................................................................................18

6.3

AIR AI R COO COOLE LERS RS ............................................... ........................................................................ .................................................. ..................................... ............18 18

6.4

OTHER EXCHA EXCHANGER NGER TYPE TYPES S .....................................................................................20

7.0

EXCHANGER EXCHAN GER PLOT LOCATION LOCATION AND ELEVA ELEVATION TION OF EXCHAN EXCHANGERS GERS....................24 ....................24

7.1

SHELL SHE LL & TUBE ARRA ARRANGEM NGEMENTS ENTS .............................................................................24

7.2

LOCATION LOCA TION BY ASS ASSOCI OCIATI ATION ON.....................................................................................24 .....................................................................................24

7.3

EXCHAN EXC HANGER GER BATTER BATTERY Y ARR ARRANG ANGEME EMENTS NTS...............................................................27 ...............................................................27

7.4

ELBOW NOZZLES TO REDUCE SHELL ELEVA ELEVATION TION................................................28 ................................................28

7.5

EXCHAN EXC HANGERS GERS WITH COND CONDENS ENSATE ATE POTS POTS...............................................................28 ...............................................................28

7.6

REBOILE REBO ILERS RS WITH COND CONDENS ENSATE ATE POTS ...................................................................30

Electronic documents, once printed, are uncontrolled and may become outdated. Refer to the electronic documents in BecRef for current revisions. Bechtel Confidential © Bechtel Corporation 1995, 2002. All rights reserved. Engineering Design Guide – Exchanger Exchanger Piping 3DG-P22-00004-002

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7.7

DOUBLE DOUB LE PIP PIPE E EXC EXCHAN HANGERS GERS.....................................................................................30 .....................................................................................30

7.8

RACK RAC K MOUN MOUNTED TED AI AIR R COOLE COOLERS RS................................................................................30 ................................................................................30

8.0

SHELL AND TUBE NOZZLE LOCATION & NOZZLE TYPE .......................................33

8.1

SHELL SHE LL & TUBE TUBE NOZZL NOZZLE E LOCA LOCATION TION OPTI OPTIONS ONS.........................................................33 .........................................................33

8.2

SHELL SHE LL & TUBE TUBE NOZZL NOZZLE E ORIE ORIENTATI NTATION ON OPTI OPTIONS ONS...................................................34 ...................................................34

8.3

NOZZLE NOZZL E LOCA LOCATION TION WITH RES RESPEC PECT T TO FLOW .......................................................35

8.4

AIR AI R COO COOLE LERS RS ................................................ ......................................................................... .................................................. ..................................... ............35 35

9.0 9. 0

SUPP SU PPOR ORTS TS ................................................. .......................................................................... .................................................. .........................................37 ................37

9.1 9. 1

SHEL SH ELL L & TUB TUBE E ............................................... ........................................................................ .................................................. ..................................... ............37 37

9.2

SPACE SPA CE FRAM FRAMES ES OR SPA SPACER CERS S ..................................................................................38

9.3

SADDLE SA DDLE / FOUND FOUNDATI ATION ON CLEA CLEARAN RANCES CES....................................................................39 ....................................................................39

9.4

SHELL SHE LL & TUBE PIP PIPE E SUP SUPPORT PORT LOCA LOCATIONS TIONS ...........................................................40

9.5

VERTICA VER TICAL L REBO REBOILE ILER R SUP SUPPORTS PORTS .............................................................................41

9.6

AIR AI R COOLE COOLER R SUP SUPPOR PORTS TS ............................................................................................42

10.0 MAINTENANCE AND OPERATIONAL ACCESS .........................................................43 10.1 SHELL & TUBE ............................................... ........................................................................ .................................................. ..................................... ............43 43 10.2 BUNDLE EXTRACTOR.................................................................................................46 EXTRACTOR .................................................................................................46 10.3 CLEARA CLEARANCES NCES ................................................ ......................................................................... .................................................. ..................................... ............47 47 10.4 STACKED EXCHANGERS............................................................................................47 EXCHANGERS............................................................................................47 10.5 CRANE ACCESS........................ ACCESS................................................. .................................................. ................................................... ................................. .......47 47 10.6 AIR COOLERS ................................................ ......................................................................... .................................................. ..................................... ............47 47 10.7 AIR COOLER HEADER BOX ACCESS ........................................................................48 10.8 PLATFORM OPTIONS OPTIONS FOR AIR COOLER COOLER MOTOR ACCESS....................................49 ACCESS ....................................49 11.0 11 .0

PIPE PI PE ST STRE RESS SS...................... ............................................... .................................................. .................................................. ..................................... ............50 50


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11.1 EXCHANGER ANCHOR LOCATION............................................................................50 LOCATION ............................................................................50 11.2 SHELL & TUBE NOZZLE NOZZLE LOADS LOADS ................................................................................51 11.3 AIR COOLER NOZZLE NOZZLE LOADS LOADS....................................................................................51 ....................................................................................51 12.0 12 .0

REFE RE FERE RENC NCES ES......................... .................................................. .................................................. ................................................... ................................. .......52 52


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LIST OF FIGURES Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Fig igur ure e 10 10 Fig igu ure 11 Fig igu ure 12 12 Fig igu ure 13 Figu Fi gure re 14 Figu Fi gure re 15 Figure Fig ure 16 Fig igu ure 17 Figu Fi gure re 18 Figure 19 Figu Fi gure re 20 Figu Fi gure re 21 Figu Fi gure re 22 22 Figu Fi gure re 23 23 Fig igu ure 24 24 Figu Fi gure re 25 Figu Fi gure re 26 26 Figu Fi gure re 27 Figu Fi gure re 28 Figu Fi gure re 29 Figu Fi gure re 30 Fig igu ure 31 Figure Fig ure 32 Figu Fi gure re 33 33 Figure 34 Figure 35 Figure 36 Figure 37 Figure 38 Figure 39 Figure 40 Figure 41 Figure 42

Standard Counterflow Patterns for Shell & Tube .................................................9 Exchanger Nomenclature ...................................................................................12 Shell & Tube Fabrication Tolerances .................................................................14 Shell & Tube Fabrication Tolerances .................................................................15 Vertical Vessel Mounted Reboilers ....................................................................16 Condensate Pot Effect on Tower .......................................................................17 Vertical Direct Mount Condenser .......................................................................17 Double Pipe Exchanger Components ................................................................18 Air Cooler Header Box Types ............................................................................19 Air Coo oole lerr Co Compon one ent nts s ......................................................................................20 Stab-in Reboil ile er .................................................................................................21 Spir ira al Ex Exchanger ................................................................................................21 Pla latte Exchanger .................................................................................................22 Alum Al umin inum um Co Core re Ex Exch chan ange gerr ................................................................................23 Core Co re Exch chan ange gerr In Insu sula lati tion on.................................................................................23 .................................................................................23 Standa Sta ndard rd Pipin Piping g Arra Arrange ngeme ments nts for Sh Shell ell & Tub Tube e Excha Exchange ngers rs ...........................24 Exch chan ange gerr Pla Place cem ment ........................................................................................27 Arra Ar rang ngem emen entt of of Ex Exch chan ange gerr Bat Batte terie ries s .................................................................28 Elbow Nozzles ...................................................................................................28 Alte Al tern rnat ative ive to Ve Vert rtic ical al Con Conde dens nsat ate e Pot Pot ..............................................................29 Cond Co nden ensa sate te Po Pott Pipi Piping ng Ar Arra rang ngem emen entt ................................................................29 Doub Do uble le Pip Pipe e Ex Exch chan ange gerr – Met Metho hod d of Su Supp ppor ortt ....................................................30 Conv Co nven entio tiona nall Plat Platfo form rm De Desi sign gn for for Air Air Coo Cooler lers s ...................................................31 Air Coole lerr Su Supports ...........................................................................................32 Nozz No zzle le Adju Adjust stm men ents ts to Sta Stand ndar ard d Exch Exchan ange gers rs ....................................................33 Poss Po ssibl ible e Nozz Nozzle le Arr Arran ange gem men ents ts for for Shel Shelll & Tube Tubes s .............................................34 Chan Ch ange ge No Nozz zzles les to Im Impr prov ove e Rou Routin ting g .................................................................35 Chan Ch ange ge Fl Flow ow to Im Impr prov ove e Rou Routi ting ng ......................................................................35 Odd Od d or or Eve Even n Pas Pass s Air Air Coo oole lers rs ...........................................................................36 Stan St anda dard rd Ai Airr Coo Cooler ler Pi Pipin ping g Arr Arran ange gem men ents ts .........................................................36 Ins In ser erts ts fo forr Air Air Cool oler ers s ........................................................................................37 Shell Sh ell & Tub Tubes es at Grad Grade e with with Sa Same me U/G Co Coolin oling g Water Water Supp Supply ly ........................38 Shel Sh elll & Tube Tubes s on El Elev evat ated ed Pla Platf tfor orm m ..................................................................38 Space Framing Framing...................................................................................................39 ...................................................................................................39 Clearances for Shell & Tube Exchan Exchangers gers ..........................................................40 Support Design for Piping at Shell & Tube ........................................................41 Vertical Reboilers Reboilers...............................................................................................42 ...............................................................................................42 Air Cooler Supports ...........................................................................................43 Shell & Tube Excha Exchanger nger Access ........................................................................44 Tube Pulling Requirem Requirements ents ...............................................................................45 Tube Bundle Extrac Extractor tor .......................................................................................46 Crane Access Access...................... ................................................ ................................................... .................................................. ............................ ...47 47


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Figure 43

Plugged Header Box ..........................................................................................48

LIST OF FIGURES (contd.) Figure 44 Figure 45 Figure 46 Figure 47

Air Cooler Platforming Alternatives ....................................................................50 Slotted Holes for Shell & Tubes .........................................................................51 Lateral Stresses on Air Cooler Nozzles .............................................................52 Spring Supports for Air Coolers .........................................................................52


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1.0

PURPOSE

To provide the layout designer with guidelines for the development of piping design for nonfired heat transfer exchangers. 2.0 2.0

EXC XCLU LUS SIONS ONS

All or part of this guide may be superseded by client mandatory standards standards or by the codes and regulations imposed by governmental jurisdictions covering the location where the piping is installed. 3.0 3.0

DIS DISCU CUS SSION SION

3.1

SAFETY

Proper consideration for personnel safety around exchangers requires arranging piping and valves in a manner that does not obstruct access for operation, maintenance or egress. 3.2

OPE OPERATION TION

Exchangers normally require minimal minimal attention during operation. Valves however, must must be located for easy access. Where valves cannot be operated from grade, chain operators shall be used. If chain operators are not allowed per client specifications, platform access to valves shall be considered. 3.3 3.3

MAIINTEN MA NTENA ANC NCE E

Piping shall be arranged in a manner to allow adequate access to removable channel covers without requiring requiring excessive dismantling of the piping system. system. The bolting connecting the channel cover to the shell must be easily accessed in order to pull the tube bundle. Consideration shall be given for clearances in all directions for the use of bundle extractors (10.2). 4.0 4.0

TERM TERMIINOLO NOLOGY GY

Baffles: Partial interior walls set within the shell of an exchanger to redirect the flow in the exchanger to maximize maximize contact time and thereby increase heat transfer (Fig. 1). Bundle: A group of tubes connected to common inlet and outlet head/heads. Bundles are usually associated with shell and tube type exchangers (Fig. 1), though at times they may be used independent of a shell (as in the case of stab-in heaters) (Fig. 11). Cell: A grouping of tubes connected to common common inlet and outlet manifold manifold boxes. Cells are usually associated with air coolers.


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Conduction: The ability of an object to pass (conduct) heat through its molecular structure; the distribution or transfer of heat (energy) from one end of an object or from one object to another through physical contact. Convection: The mixing action that occurs in any heated fluid (heated fluid rises displacing cool fluid which falls replacing heated fluid); the transfer of heat within a fluid or from one fluid to another by means of the thermal mixing action. Fins: Appendages affixed to the outer skin of tubes to augment their surface area to increase contact time and thereby heat transfer. Forced draft: A method of tube cooling in which fan driven air is blown directly through a tube cell (Fig. 10). Induced Induced draft: A method of tube cooling in which fan drawn air is pulled (induced) through a tube cell (Fig. 10). Parallel: A method of interconnection of exchangers in which the flow fl ow stream is split between two or more exchang exchangers ers capable of operating independently either simultaneously or in back-up of each other. Exchangers in parallel usually can be isolated from the flow stream to allow for maintenance or for temperature or output control (Fig. 16). Series: A method of interconnection of exchangers in which the flow fl ow stream must must past through each exchanger exchanger in sequence. Exchangers operating in series are treated as one system component component and usually cannot be isolated without shutdown of the system (Fig. 16). Shell: Closed conduit used to convey a medium around a set of tubes for the purpose of heat transfer between that medium and one being conveyed by the tubes (Fig. 1). TEMA: The Tubular Exchanger Manufacturers Association, an industrial association associati on which has published standards for the design and manufacture of tubular exchangers (Fig. 2). Thermosiphon: Thermosiphon: A method method of circulation based on a heated heated fluid's tendency to rise. This method of circulation is used most often in boiler and reboiler systems. Tubes: Closed conduit for a single heating/cooling media most often used in conjunction with a sealed outer conduit (shell), but may also be used in open contact with atmospheric cooling/heating media. They are also often referred referred to as channels (Fig. 1).


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5.0

BASI BA SICS CS OF HE HEAT AT TRANS TRANSFE FER R

The most common common method of heat transfer from one fluid to another in a process environment is by the use use of exchangers. exchangers. Exchangers, Exchangers, while varying greatly greatly in design, all operate on the same principle. The principle that heat (energy) tends to equalize by dissipation. That is that heated objects try to equalize their temperature by transmitting their heat to surrounding cooler objects. objects. This is similar to a liquid seeking seeking its own level. Hot Hot objects try to transmit transmit their heat to any cooler objects around them, which in turn tend to absorb that heat. All exchangers employ this principle by using one or more of three heat transfer methods; conduction, convection and radiation. The tendency of the heated portions of a fluid to rise dictates the most common pattern of flow in exchanger piping. That pattern is for the fluid receiving heat to flow up through the the exchanger and the fluid expending heat to flow down (Fig. 1).

Figu gure re 1

Stan St anda dard rd Co Coun unte terf rfllow Pa Patte ttern rnss for for Sh Shel elll & Tu Tub be


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6.0

TYPES TYPES OF EXCHA EXCHANGE NGERS RS

While often referred to by their design and construction characteristics, exchangers are most frequently identified by their process function. The following is a listing of process names names often assigned exchangers relative to their function: Exchanger: Heats one stream while cooling another (Very efficient in that there is no waste heat loss). Cooler: Cools liquids or gases without without condensation. Subcooler: Condenses vapor and further cools the condensate using water as a cooling medium. Condenser: Cools a vapor to its dew point in order to extract condensate from it. Chiller: Uses refrigerants to cool a stream below the standard temperature of available cooling water streams. Heater: Heats process stream (generally to its boiling point) with no appreciable vaporization (often uses steam as heating heati ng medium). Reboiler: Reboils (vaporizes) the bottom stream of a fractionating tower prior to its return to the tower. Often employs thermosiphon thermosiphon phenomenon rather than any mechanical mechanical flow enhancement. Waste Heat Boiler: Uses waste heat (i.e., gas-turbine exhaust) as a heating medium. Steam Generator: Uses process liquids or gases to produce steam (usually from boiler feed water). Vaporizer: Vaporizes part of a process stream (also called an evaporator). 6.1

SHELL & TUBE TUBE

The most common heat exchanger encountered in any process or power plant is the shell and tube exchanger. exchanger. These exchangers, exchangers, because of their reliability, low maintenance, maintenance, and durability, generally offer the most economical method of heat control and transfer, while their "no moving parts" simple means of operation can be very efficient. They operate by conducting one fluid stream through the channel (tube) head of the exchanger into a set set of tubes (the bundle) that is encased encased within the exchanger exchanger shell. A second fluid is simultaneously directed through the shell (usually in the opposite direction) while maintaining contact with with the tubes. The heat transfer transfer is effected through the tube walls walls without the fluids coming in direct contact with each other.


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6.1.1 Conventional Conventional TEMA Exchangers Exchangers Of shell and tube exchangers the most common are those designed to meet TEMA standards of design and construction (Fig. 2).


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Figure 2

Exchanger No Nomenclature

TEMA exchangers exchangers offer the following:


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Economy: Economy: they can be varied in size in accordance with with the heat transfer required required thereby utilizing utili zing the minimal material for the maximum result; they can handle large flow rates with a large range of pressure ratings; they can often reduce waste heat by heating one flow stream while cooling another. Maintenance: standardization allows standardized maintenance maintenance procedures with more more readily obtainable parts; few parts subject to failure; fail ure; minimal assembly/disassembly requirements. Efficiency: by “multiple “multiple pass series flow” these exchangers exchangers offer an almost unlimited range range of transfer rates. Reliability and Consistency: design is made made simpler and reliabil reliability ity increased by the the standardization of design and construction tolerances set by TEMA.

6.1.2 Fabricatio Fabrication n Tolerances Tolerances Electronic documents, once printed, are uncontrolled and may become outdated. Refer to the electronic documents in BecRef for current revisions. Bechtel Confidential © Bechtel Corporation 1995, 2002. All rights reserved. Engineering Design Guide – Exchanger Exchanger Piping 3DG-P22-00004-002

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Figure 3

Sh ell & Tube Fabrication Tolerances To lerances


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Figu gure re 4

Sheell & Tub Sh ubee Fa Fabri riccati tion on To Tollera ran nces


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6.1.3 Reboiler Reboilers s A variation of the conventional shell and tube, still incorporating TEMA standardized components, is the reboiler (Figs. 5 and 6).

Figure 5

Vert rtiical Vess sseel Mou oun nte ted d Reboi oillers


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Figure 6

Condensate Po Pot Ef Effect on on Tower

6.1.4 Direct Mount Condensers Condensers Occasionally condensers associated with separators, knockout drums, or accumulators are mounted directly on the vessel. Such configuration can be very cost effective effective in that they eliminate some of the components required for a stand alone condenser, the interconnecting piping between the equipment as well as the supports for said piping. (Fig. 7)

Figure 7

Verti ticcal Direct Mou Moun nt Con Cond denser


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6.2

DOUBLE DOUBLE PIPE PIPE EXCHA EXCHANGE NGERS RS

Double pipe pipe are probably the most economical exchangers available. They consist of a single tube enclosed within another. As with with conventional shell and tube exchangers, exchangers, double pipes rely on the cross flow of two fluid fl uid streams to affect a heat transfer. In an effort to increase the contact time of fluids in double pipe exchangers, most manufactures attach fins to the inner tube. This practice has resulted in this type of exchanger exchanger being referred to as fin-tubes or G-fins. (Fig. 8)

Figure 8

6.3

Dou oub ble Pi Pip pe Ex Excchanger Com ompo pon nents

AIR COOL COOLE ERS

Air coolers make up the second largest family of process and power plant exchangers. While not as efficient, compact or precise as shell and tubes, air coolers are often the answer when supplies of cooling fluids (cooling (cooling water, refrigerant, cool process process fluids...) are limited. Their purchase cost is often lower than that of shell and tubes, which can also make them preferable for services where precise temperature control is less of a concern. Electronic documents, once printed, are uncontrolled and may become outdated. Refer to the electronic documents in BecRef for current revisions. Bechtel Confidential © Bechtel Corporation 1995, 2002. All rights reserved. Engineering Design Guide – Exchanger Exchanger Piping 3DG-P22-00004-002

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Air coolers operate by flowing a fluid through a set of tubes (cell) while air is passed through the cell around the tubes. The passing air absorbs and carries away the heat. Header boxes boxes for air coolers may may be specified plugged or with with cover plate. Plugged boxes boxes allow the maintenance of damaged tubes without the disassembly of the box but are generally heavier and more prone to leakage. (Fig. 9)

Figure 9

Air Cooler Header Box Types


Page 19 of 52

6.3.1 Forced Forced Draft Draft Forced draft coolers operate by pushing air through the tube cells from fans mounted below them. This method of fan and motor mounting make them easily accessible from below the exchanger. These coolers are more efficient than induced draft because the cool air they move is denser (more air is moved), however, because the fans tend to channel the air, distribution may be uneven. This may result in the formation of hot spots in the cells and cause uneven tube wear. The cells of these coolers are exposed to the elements, also contributing to wear (Fig. 10). 6.3.2 Induce Induced d Dra Draft ft Induced draft coolers draw air up through the tube cells with fans mounted above them. This arrangement reduces the formation of hot spots by flowing air more evenly across the tubes and do protect the cells from the elements by covering them with the fan cowlings. The air they move, however, is warm and less dense (having already passed through the cells), reducing their efficiency. The over head fan and motor motor mounting make make these coolers more difficult to maintain (Fig. 10).

Figure 10

6.4 6.4

Air Coo ooller Com omp pon oneents

OTHER OTHER EXCH EXCHAN ANGE GER R TYPE TYPES S


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6.4.1 Stab-In Exchangers Exchangers Also referred to as bayonet exchangers, they are often used where pressure loss through piping, space limitations or other circumstances preclude preclude the use of more conventional conventional exchangers. They are usually constructed of a TEMA standardized head an and d tube bundle. Often used as heating elements for tanks and occasionally in lieu of reboilers for fractionating towers. These exchangers, because of the way they are integrally connected to the equipment they service, usually cannot be worked worked on without without shut down of that that equipment. This limits their maintainability and often makes them a last choice method of heat control (Fig. 11)

Figure 11

Sta tab b-in Reboiler

6.4.2 Spiral Spiral Exchange Exchangers rs These consist of a tube or set of tubes, twisted into a helical coil, contained in a barrel like shell or casing. The casing is usually split (most (most often vertically) and can be opened opened for maintenance. maintenance. One fluid enters and exits the tubes through nozzles penetrating one side of the casing while the second fluid passes through the casing from nozzles on either end (Fig. (Fi g. 12).

Figure 12

Spiral Exchanger


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6.4.3 Plate Exchangers Exchangers While not having true tubes, the plate exchanger operates on the same mechanical principles as the shell and tube. Instead of tubes the plate exchanger uses uses sets of tightly arranged thin, flat, hollow plates. The fluids flows flows through alternate contacting opposite walls walls of each plate, transferring their heat in the process. process. These exchangers exchangers can be very efficient efficient in their ability to transfer heat attaining as low as a 2% heat differential between exiting fluids. Plates can also be added or removed to vary the performance or for maintenance and repair (Fig. 13).

Figure 13

Plate Exchanger

6.4.4 Core Core Exchan Exchanger ger Core exchangers exchangers (or core chillers) are a unique variation of plate exchangers. These exchangers exchangers use plates alternately set within a shell through which the flow media pass, as do plate exchangers. The plates in a core, however, are sealed together, in a process called brazing, to create a single monolithic monolithic unit. Materials used in these types of exchangers exchangers are often aluminum or aluminum alloys, which are great for heat transfer, but notoriously bad in terms of tinsel strength and stress durability. For that reason cores are used used for low temperature or chilling services exclusively. Piping serving these exchangers exchangers is usually usually S.S., requiring a transition piece between the piping and exchanger. These are often supplied by a third party vendor specializing in such items. (Fig. 14 & 15)


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Figure 14 Figure 15

Aluminum Cor oree Ex Excchanger Cor oree Ex Excchanger In Inssulati tion on


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7.0

EXCHANG EXCHANGER ER PLOT LOCATION LOCATION AND ELEVATI ELEVATION ON OF EXCHANG EXCHANGERS ERS

7.1

SHELL SH ELL & TUBE AR ARRA RANGE NGEME MENTS NTS

With exchanger piping, as with most piping systems, the less piping required, the better the design. The designer shall shall investigate strategies such as stacking stacking and banking exchangers exchangers in like service to minimize the piping required (Fig. 16)

Figu Fi gure re 16 16

7.2

Stand Sta ndard ard Pi Pipi ping ng Ar Arran rangem gemen ents ts for for Shel Shelll & Tub Tubee Exch Exchan ange gers rs

LOCATI LOCATION ON BY AS ASSOC SOCIA IATION TION

In setting locations for exchangers, attention shall be paid to the placement of associated equipment. (Fig. 17) Locations will be chosen with a view toward reducing the amount of Electronic documents, once printed, are uncontrolled and may become outdated. Refer to the electronic documents in BecRef for current revisions. Bechtel Confidential © Bechtel Corporation 1995, 2002. All rights reserved. Engineering Design Guide – Exchanger Exchanger Piping 3DG-P22-00004-002

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piping required to connect the system. system. The overall system flow will be reviewed and studies done to determine the optimal placement for exchangers.


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POOR LOCATION

PREFERED LOCATION

Example 1

PREFERED LOCATION

POOR LOCATION

Example 2 EXCHANGER PLACEMENT Fig. 17

Figure 17

7.3

Exchanger Placement

EXCHA EXCHANGE NGER R BA BATTER TTERY Y AR ARRA RANGE NGEME MENTS NTS

Exchanger battery arrangements for maintenance and operational access and also serve as unobstructed escape escape routes from the area in case of emergency (Fig. 18).


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Figu gure re 18

7.4

Arr rran ange gem men entt of Ex Exch chan ange gerr Bat Batte teri ries es

ELBOW ELBOW NOZZLES NOZZLES TO REDUC REDUCE E SHELL SHELL ELEVATIO ELEVATION N

The elevation of exchangers is frequently set by the requirements of the process they are trying to maintain. The designer shall be aware, aware, however, of the opportunities for reducing piping runs that lowering or raising some exchangers may present (Fig. 19). It should be noted that elbow nozzles will, to a certain extent, “fix” the pipe routing local to the exchanger due to nozzle orientations. The customer shall be consulted prior to any decision to use e elbow lbow nozzles.

Figure 19

7.5

Elbow Nozzles

EXCHA EXCHANGE NGERS RS WITH WITH CONDE CONDENSA NSATE TE POTS POTS

The elevation of exchangers operating on steam is often set by the resident time of the downstream condensate pot, i.e. the time the condensate must remain in the pot prior to being Electronic documents, once printed, are uncontrolled and may become outdated. Refer to the electronic documents in BecRef for current revisions. Bechtel Confidential © Bechtel Corporation 1995, 2002. All rights reserved. Engineering Design Guide – Exchanger Exchanger Piping 3DG-P22-00004-002

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returned to the condensate header, and is critical to maintaining upstream and downstream pressure and temperature. If process conditions allow, use of a horizontal pot rather rather than a vertical one, it can significantly lower the elevation requirements of the exchanger (Figs.20 & 21).

Figu gure re 20

Alte tern rnat atiive to Ver Verti tica call Con Conde den nsa sate te Pot Pot

Figu gure re 21

Con onde den nsa sate te Po Pott Pipi Pipin ng Arr Arran ange gem men entt


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7.6

REBOI REB OILE LERS RS WITH WITH CONDEN CONDENSA SATE TE POTS

With vertical reboilers the condensate pot is commonly at grade and once again backpressure is critical to maintaining temperature in the reboiler. The pot elevation in this case is often set by the pump or downstream downstream condensate system requirements. Every effort must be made to keep the elevation of this pot as low as possible. possible. The higher the pot has to be, the higher the reboiler must be and consequently the higher the tower liquid level must be. As the tower tower goes up so do all costs associated with it (additional skirt steel, additional piping, stronger foundation...) (Fig. 6). 7.7

DOUBLE DOUBLE PIPE PIPE EXCHA EXCHANGE NGERS RS

These exchangers are usually stacked in large banks and operated in series because of their relatively low heat transfer rates. Occasionally, when only one double pipe is required, it is good to keep in mind that there are options on mounting the exchanger that can result in significant cost savings. The standard method method of support for such items is an independent two-pier two-pier foundation, but the light weight of the double pipe lends it to mounting on piers for other required equipment (such as drums) or even nearby nearby structural columns columns by side bolting (Fig. 22). Such mounting mounting eliminates the need for the foundation.

Figu gure re 22

7.8

Doub Do ublle Pi Pipe Ex Exch chan ange gerr – Met Meth hod of of Sup Suppo port rt

RACK RA CK MOUNTE MOUNTED D AIR AIR COOLER COOLERS S

Air cooler elevations (whether at grade or elevated on racks or structures) are generally set by their air drawing capabilities, therefore a certain amount of clear space must be maintained to ensure the performance of the cooler. It is necessary to provide maintenance platforming for access to the motors motors and header header boxes (Fig. 23 & 24). Note that this platforming, because of its relative elevation when air coolers are rack mounted, makes makes a good place for locating l ocating relief valves.


Page 30 of 52

Area can be used for equipment relief valves to flare

HEADER BOXES

PLATFORMS

MOTORS

PLATFORMING

HEADER LEVEL

MOTOR / FAN LEVEL

CONVENTIONAL PLATFORM DESIGN FOR AIR COOLERS Fig. 23

Figu gure re 23 23

Con Co nve vent ntiion onal al Pl Plat atfform De Desi sign gn for Ai Air Cool Cooler erss


Page 31 of 52

PLAN WHEN ENGINEERING CONTRACTOR PROVIDES SUPPORTING STEEL, INTERMEDIATE PIPE SUPPORTS CAN BE LOCATED MORE EASILY

ELEVATION

ACCESS WAY

ACCESS WAY

BY VENDOR BY ENG. CONTRACTOR BY VENDOR BY ENG. CONTRACTOR AT GRADE OR ON RACK

AIR COOLER SUPPORTS

Figure 24

Fig. 24

Air Cooler Supports


Page 32 of 52

8.0

SHELL SHELL AND TUBE NOZZLE NOZZLE LOCATION LOCATION & NOZZLE NOZZLE TYPE

8.1

SHELL SHELL & TUBE NOZZLE NOZZLE LOCATI LOCATION ON OPTION OPTIONS S

The designer shall be aware of the allowable variations to shell and tube exchanger nozzle locations (Fig. 25).

Figu gure re 25

Nozz No zzlle Adj djus ustm tmen ents ts to Stan Standa dard rd Ex Exch chan ange gers rs


Page 33 of 52

8.2

SHELL SHELL & TUBE NOZZLE ORIENTATIO ORIENTATION N OPTIONS OPTIONS

A rearrangement of nozzles, can in some cases, reduce the required piping for a system. While such relocation is something that must be discussed with and approved by the Responsible Engineer (RE), significant cost savings can be attained by such rearrangement. (Fig. 26 and 27)

Figu gure re 26 26

Possi Pos sibl blee Noz Nozzl zlee Arr Arran ange gem men ents ts for for Shel Shelll & Tu Tub bes


Page 34 of 52

Figu gure re 27

8.3

Chan ange ge No Nozz zzlles to Im Impr prov ovee Rou outi tin ng

NOZZLE NOZZLE LOCATI LOCATION ON WITH WITH RE RESP SPEC ECT T TO FLOW FLOW

As with relocation of nozzles, a change in the flow direction of an exchanger can at times result in an improved improved design design (Fig. 28). As with with nozzle relocation, any any changes in the flow direction must be discussed with and approved by the RE prior to implementation in the design.

Figure 28

8.4

Change Fl Flow to Im Impro rov ve Rou Routi tin ng

AIR COOL COOLE ERS

8.4.1 Nozzle Nozzle Location Locations s The locations of nozzles are based on the number of tube bundle cells manifolded together and the number number of passes the tubes make between between the inlet and outlet manifold boxes. An even number of passes place the inlet and outlet nozzles on the same side of the cooler, while an odd number of passes results in the nozzles being on opposite opposite sides. This can be particularly important when when the coolers are rack mounted. mounted. If the upstream and downstream equipment equipment are on the same side of the rack an even pass arrangement is preferable, while if they are on opposite sides of the rack an odd number of passes could reduce piping runs (Fig. 29).


Page 35 of 52

Figure 29

Odd or Ev Eveen Pass Air Coo oollers

8.4.2 Air Cooler Piping Arrangements Arrangements The piping arrangements called for at air coolers can also greatly affect their placement and elevation. In cases where true symmetrical symmetrical (cascaded) (cascaded) piping is required to stabilize two-phase flow, the required required elevations of supports for the piping can become prohibitive. In such cases the use of header box inserts may reduce the need for symmetry to the point that a rake style arrangement arrangement may be used (Fig. (Fig. 30 and 31). The RE shall be consulted about such possibil possibilities. ities.

Figu Fi gure re 30

Stan Sta nda dard rd Air Co Cool oler er Pi Pipi ping ng Arra rran nge gem men ents ts


Page 36 of 52

Figure 31

Inserts for Air Coo oollers

9.0

SUP UPP PORTS ORTS

9.1

SHELL & TUBE TUBE

Shell & Tube exchangers exchangers at grade operating operating off of the same same underground cooling water supply line shall be aligned by the channel channel head nozzle (Fig. 32). The offset of the supports supports will have little cost effect at grade. Exchangers Exchangers in upper levels of structures, however, however, shall be aligned by supports to minimize the requirement for structural steel (Fig. 33).


Page 37 of 52

Figure Figu re 32 Figu gure re 33

9.2

Shelll & Tub Shel Tubes es at Grad Gradee wit with h Sam Samee U/G U/G Cool Cooliing Wa Water ter Sup Suppl ply y Shel Sh elll & Tu Tub bes on El Elev evat ated ed Pl Plat atffor orm m

SPAC SPACE E FRAME FRAMES S OR SPAC SPACER ERS S

As a standard, shell shell and tube exchangers come come w with ith saddle supports. When ordered for a stacked application, the lower exchanger is generally ordered with opposed top and bottom saddles to support the upper upper exchanger. exchanger. However, However, there are occasions when it is desirable to set the upper exchanger at a greater height than normally achievable with saddles (i.e., exchangers in different services that are stacked to save plot space or expansion of an Electronic documents, once printed, are uncontrolled and may become outdated. Refer to the electronic documents in BecRef for current revisions. Bechtel Confidential © Bechtel Corporation 1995, 2002. All rights reserved. Engineering Design Guide – Exchanger Exchanger Piping 3DG-P22-00004-002

Page 38 of 52

existing unit requiring the placement of a new exchanger on an existing one). In these cases, space frames frames (or spacers) will be required (Fig. 34).

Figure 34

9.3

Space Framing

SADDL SA DDLE E / FOUNDA FOUNDATIO TION N CLEAR CLEARAN ANCES CES

Clearances for piping, valves, insulation, maintenance equipment and instrumentation shall always be checked (Fig. 35). Electronic documents, once printed, are uncontrolled and may become outdated. Refer to the electronic documents in BecRef for current revisions. Bechtel Confidential © Bechtel Corporation 1995, 2002. All rights reserved. Engineering Design Guide – Exchanger Exchanger Piping 3DG-P22-00004-002

Page 39 of 52

Figure 35

9.4

Clearances for Shell & Tube Exchangers

SHELL SH ELL & TUBE PIPE PIPE SUPPOR SUPPORT T LOCATI LOCATIONS ONS

Often pipe supports at shell and tube exchangers can be incorporated with the exchangers support foundations or can be set upon the same foundation. foundati on. This can save the expense of Electronic documents, once printed, are uncontrolled and may become outdated. Refer to the electronic documents in BecRef for current revisions. Bechtel Confidential © Bechtel Corporation 1995, 2002. All rights reserved. Engineering Design Guide – Exchanger Exchanger Piping 3DG-P22-00004-002

Page 40 of 52

separate support foundations foundations (Fig. (Fig. 36). Anchors set on such supports allow the pipe to grow with the exchanger instead of against it.

Figure 36

9.5

Support Design for Pipin Piping g at Shell & Tube

VERTI VERTICA CAL L REB REBOI OILER LER SU SUPP PPORTS ORTS


Page 41 of 52

In setting vertical reboilers, a number of options for method of support are possible. The best choice for any given application will depend on the process requirements as well as the availability of space, type and and weight of the equipment being used. The maintenance requirements requirements for these reboilers shall also be reviewed in deciding how best to support them in that bundle pulling for a vertical exchanger can require require some unconventional clearances (Figs. 5, 37 & 40)

Figure 37

9.6 9.6

Vertical Reboil Reboilers ers

AIR AIR COOL COOLER ER SU SUPP PPOR ORTS TS


Page 42 of 52

Air coolers can be ordered with two different types of supporting structures, with or without legs provided (Fig. (Fig. 38). The latter of these two options options can help reduce costs costs and increase flexibility of the exchanger's supports especially when the coolers are to set above a pipe rack. Coolers provided with with legs can reduce costs for grade grade mounted air coolers and can also be mounted with air controlling louvers or walls to protect against freezing or reduce motor noise levels. The types of supporting structures for these coolers can can affect the piping runs serving them.

Figure 38

Air Cooler Support Supportss

10.0

MAINTENANCE MAI NTENANCE AND OPERATIONAL OPERATIONAL ACCESS

10.1 10 .1

SHEL SH ELL L & TUBE TUBE


Page 43 of 52

Exchangers shall be piped with a view toward maximizing access to the tube bundle and other maintainable components components (Figs. 39 & 40). 40). Break out flanges at the channel channel end, however, are often an unnecessary unnecessar y added expense. expense. Even at exchangers with with fixed tube bundles (where bundle pulling is not a concern), sufficient room shall be allowed al lowed at the heads to allow all ow rodding out of tubes. Usually an area equal equal to the length of the the tubes will do. Clear accessways should be provided to allow operator access to valves. If chain operators are used for elevated valves, care should be taken to avoid chains obstructing the walkways. walkways. HEAD + 30" (750mm) 9" (230mm) min. (ALL BODY FLANGES) OPERATING VALVES (SUGGESTED LOCATIONS)

WALKWAY

A E R A L A V O M E R D A E H

30" (750mm) min.

18" (450mm) MIN. BETWEEN FLANGES OR INSULATION

18" (450mm) min. (TYPICAL)

TUBE LENGTH + 30" (750mm)

HEAD SWING (IF FITTED WITH A DAVIT)

SHELL AND TUBE EXCHANGER ACCESS

Figure 39

FIG. 39

Shell & Tube Exchanger Access


Page 44 of 52

Figure 40

Tube Pulling Requirement Requirementss


Page 45 of 52

10.2 10. 2

BUNDLE BUN DLE EXTRA EXTRACTOR CTOR

Most tube bundle pulling equipment can operate with a minimum of space allowance (Fig. 41). Check the client's clearance requirements for his particular bundle extractor.

Figure 41

Tube Bundle Extracto Extractorr


Page 46 of 52

10.3 10. 3

CLEAR CLEARAN ANCES CES

Clearances for maintenance, such as wrench clearance at flanges shall be provided in all cases. Often 12" (300mm) from bottom of pipe to grade is an adequate elevation for piping, however if a drain is provided in the line, a minimum of 4" (100mm) below the plug shall be provided for the removal of that plug. Knuckle clearance shall also be provided around around spectacle blinds (where (where provided) (Fig. 36). As stated earlier, access ways shall be provided for the maintenance of all exchangers requiring maintenance. These access ways shall shall provide a minimum of 2’-6" (750mm) (750mm) of unobstructed walkway walkway w with ith a minimum minimum of 7’-0" (2200mm (2200mm)) headroom. headroom. The designer shall review the arrangement of exchangers and the placement of access ways as an overall scheme instead of in terms of of individual components. Each access can be used to service more more than one set of exchangers, optimizing the space allocated to their thei r placement (Figs. 39, 40 & 42). 10.4

STACKED STACKED EXCHANGE EXCHANGERS RS

Shell & Tube exchangers may be stacked up to a maximum of three shells high if approved by the customer. 10.5 10. 5

CRANE CRA NE AC ACCES CESS S

For exchangers requiring the movement of large heavy components for maintenance, road and heavy equipment equipment access must must be a consideration. Clear unobstructed lift and laydown areas, and carry-out routes must must be designated and kept clear of equipment, equipment, platforming and structures. structures. A single crane lift area can service several pieces of equipment if properly located (Fig. 42).

Figure 42

10.6 10. 6

Crane Access

AIR AIR COOLER COOLERS S

As well as platforming for header box maintenance, most air coolers (especially those mounted on racks) require platforming platforming for motor motor access (Fig. 44). If the cooler is at grade and the motors are within the reach of and are accessible accessible by mobile equipment, the platforms platforms might be eliminated. Electronic documents, once printed, are uncontrolled and may become outdated. Refer to the electronic documents in BecRef for current revisions. Bechtel Confidential © Bechtel Corporation 1995, 2002. All rights reserved. Engineering Design Guide – Exchanger Exchanger Piping 3DG-P22-00004-002

Page 47 of 52

10.7

AIR AIR COOLER COOLER HEA HEADER DER BOX ACCE ACCESS SS

Platform access at air cooler header header boxes boxes is often required. Such platforming platforming shall provide enough access to allow the blinding of cells or the plugging of damaged tubes without interfering with the support and routing of manifold piping (Fig. 43)

Figure 43

Plugged Header Box


Page 48 of 52

10.8

PLATFORM PLATFORM OPTIONS OPTIONS FOR AIR AIR COOLER COOLER MOTOR MOTOR ACCES ACCESS S

In cases where large platforms are needed to service several bays of coolers, use a solid pattern for platforming. Reducing the details required for design, and simplified construction, outweigh the savings in material (Fig. 44). Finger style platforming shall be used only after consulting with Civil/Structural engineer.


Page 49 of 52

FOR LONG AIR COOLERS

CONVENTIONAL APPROACH TO FAN MOTOR MAINT. PLATFORM

FAN MOTORS CONVENTIONAL APPROACH PROVIDES MORE PLATFORMING, WHILE HAVING LITTLE COST IMPACT VS. ALTERNATE

ALTERNATE APPROACH

FAN MOTORS

AIR COOLER PLATFORMING ALTERNATIVES FIG. 44

gure 44

Fi

Air Cooler Platformin Platforming g Alternatives

11.0 11. 0

PIPE PIPE STRES STRESS S

11.1

EXCHANGE EXCHANGER R ANCH ANCHOR OR LOCATION LOCATION

Anchors play a large role in determining the piping configurations for exchangers. In many cases the location of anchors can be adjusted adjusted to accommodate accommodate a better piping design. This is applicable Electronic documents, once printed, are uncontrolled and may become outdated. Refer to the electronic documents in BecRef for current revisions. Bechtel Confidential © Bechtel Corporation 1995, 2002. All rights reserved. Engineering Design Guide – Exchanger Exchanger Piping 3DG-P22-00004-002

Page 50 of 52

to both pipe anchors anchors and exchanger exchanger support anchors. anchors. With shell and tubes, anchors are generally placed to allow the piping to grow parallel to the growth of the exchanger. exchanger. This minimizes the stress loads on the nozzles (Fig. 36). Anchor points of the exchangers themselves can often be manipulated to provide the best design. Slots can be cut into the exchanger support bolt holes to allow movement in a desired direction (Fig. 45). If friction forces created by the weight of the exchanger exchanger are excessive, slide plates can be introduced to allow all ow greater ease of movement. movement.

Figure 45

11.2

Slotted Holes for Shell & Tubes

SHELL SHELL & TUBE NOZZLE LOADS

The allowable loads at nozzles for shell & tube exchangers are are not usually a problem. However, when exchangers in like service are banked, it shall be kept in mind that tight fitting-to-fitting configurations for the piping may generate unacceptable loads. Changes to the piping configuration or the addition of springs to piping supports can be used to reduce these loads. Adding springs to piping supports can also aid in vertical thermal load reduction when exchanger locations require lengthy vertical piping runs. 11.3

AIR AIR COOLER COOLER NOZZLE NOZZLE LOADS LOADS

Air cooler piping anchors shall be placed close to the exchanger to minimize the growth toward the nozzles. Anchors on distribution headers shall be centered centered to equalize, as much much as possible, the lateral growth parallel to the header boxes. Air coolers are notorious for the low limits of allowable stress at the points of piping connection. The header boxes for these exchangers are usually made of gage steel and configured in a fashion that affords little if any structural strength. When these conditions are applied to even moderately hot services the result is often stress loads at the nozzles that far exceed acceptable. Lengthening the piping riser between the piping header and the manifold box can help to reduce Electronic documents, once printed, are uncontrolled and may become outdated. Refer to the electronic documents in BecRef for current revisions. Bechtel Confidential © Bechtel Corporation 1995, 2002. All rights reserved. Engineering Design Guide – Exchanger Exchanger Piping 3DG-P22-00004-002

Page 51 of 52

the lateral stresses (Fig. 46) and the addition of spring supports can reduce the load forces in the vertical (Fig. 47)

Figure 46

Lateral Stresses on Air Cooler Nozzles

Figure 47

Spring Support Supportss for Air Coolers

12.0

REFERENCES

Tubular Exchanger Manufacturers Association Standards (8 3DI-P21-00001 ISBL E Eq quipm ipment La Layout 3GS3GS-P P34 34-0 -000 0002 02 Pipin iping g Desig esign n an and d La Layo yout ut

th

Edition)


Page 52 of 52

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