Facilities Piping EPT 09-T-01 July 1998 Draft
Scope This This Engineering Engineering Practice Prac tice Tutorial (EPT) (EP T) supplements the basic basic requirements for the design design of piping systems for for refineries, refineries, petrochemica petr ochemicall plants and onshore and and offshore production and processing processing facilitie facilitiess contained in MP 16-P -01. -01. It covers all piping for f or onshore and and offshore offs hore production production and processing processing facilities.
Version 0
EPT 09-T-01
Facilities Piping
July 1998 Draft
Table of Contents Scop Sc ope e................................ ............................................................. ................................ ............................... ..................................................................... ....................................................... .............. 1 Table Tab le of Figure Fig ures s ................................................................................................................................ 5 Table of Tables Table s ............ .................. ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ......... ...6 6 1.
Refer Ref erenc ences es.................................................................................................................................. .................................................................................................................................. 7 1.1.
MEPS–Mobil MEPS –Mobil Engineering Engineer ing Practices Practi ces....... .............. .............. .............. ........... ........... .............. .............. .............. ........... ............ ............ ....7 7
1.2. 1.2 .
Mobil Tutorials Tutor ials ................................................................................................................. 7
1.3.
API AP I–American Petroleum Institute Institu te ............ .................. ............ ............ ............ ............ ............ ............ ............ ............ ........... ........... ........ ..7 7
1.4.
ASTM ASTM –American Society for Testing and Materials ............ .................. ........... ........... ............. ............. ............ ........ 8
1.5.
ASME–Soc ASME –Society iety of Mechanical Mechan ical Engineers Engine ers ........... ................ ........... ........... ............... ............... .......... .......... ........... ........... ......... .... 8
1.6.
CFR CF R–U.S. –U.S . Code of Federal Regulations Regulat ions ............ .................. ........... ........... ............ ............ ............ ............ ............ ............ ..........8 ....8
1.7.
MSS–Manufacturers Standardization Society of the Valves and Fittings Industry, Inc......................................................................................................................................8
1.8.
NFPA–Nat NFPA –National ional Fire Protection Prote ction Association Assoc iation ............ .................. ............ ............ ............ ............ ........... ........... ............ .......... ....9 9
2.
Gener Gen eral al ........................................................................................................................................ 9
3.
Defini Def initio tions ns .................................................................................................................................. 9
4.
Pipin Pip ing g Desi De sign gn .......................................................................................................................... 11 4.1. 4.1 .
Design Des ign Basis.................................................................................................................. Bas is.................................................................................................................. 11
4.2. 4.2 .
Sizing Siz ing Criter Cri teria ia ................................................................................................................1 2
4.3. 4.3 .
Pressu Pre ssure re Design............................................................................................................1 Des ign............................................................................................................1 2
4.4.
Static and Dynamic Analysis Analys is...... ............ ............ ............ ............ ............ ............ ............ ............ ............ ........... ........... ............ ............ ..........12 ....12
4.5.
Pipe Wall Thickness Thicknes s Equations Equation s .............. ..................... ............... ........... .......... .............. .............. .............. ........... ........... ............. ...........13 .....13
4.6.
Pressure Pressu re Ratings Rating s .............. ...................... ............... .......... .......... .............. .............. .............. ........... ........... .............. .............. .............. ........... ........... ..........2 ...21 1
4.7.
Determining Deter mining Pressure Press ure Breaks Break s ............ .................. ............ ............ ............ ............ ............ ............ ............ ............ ........... ........... ............ ........2 ..24 4
© Mobil Oil,1998
2 of 59
EPT 09-T-01
5.
6.
Facilities Piping
July 1998 Draft
Piping Pip ing Layout Lay out and Arrang Arr angeme ement nt ............ .................. ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ..........30 ....30 5.1.
General...........................................................................................................................30
5.2.
Maintenan Maint enance ce and Operabili Oper ability ty ............ .................. ............ ........... ........... ............ ............ ............ ............ ............ ............ ........... ........... ..........30 ....30
Design Conside Consid e rations rati ons for Specific Piping Systems System s ...... ......... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....3 .31 1 6.1. 6.1 .
Compre Com presso ssors rs ................................ ............................................................ ............................................................................... .....................................................3 ..31 1
6.2. 6.2 .
Pump Piping Pipin g .................................................................................................................. 34
6.3. 6.3 .
Steam Stea m Turbine Turb ine Piping Pipi ng ...................................................................................................37
6.4. 6.4 .
Vessel Ves sel Piping Pip ing ................................ ............................................................ ............................................................................... .....................................................3 ..39 9
6.5.
Fired Heater Piping ............ .................. ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ .......4 .43 3
6.6. 6.6 .
Relief Relie f Valve Piping Pipin g ........................................................................................................4 5
6.7. 6.7 .
Utility Util ity Piping Pip ing ...................................................................................................................46
6.8. 6.8 .
Exchange Exch angerr Piping Pipi ng.......................................................................................................... .......................................................................................................... 47
6.9.
Storage Sto rage Tank Piping ........... ................. ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ .......... ......4 ..48 8
6.10. 6.1 0. Undergrou Underg round nd Piping Pipi ng......................................................................................................4 ......................................................................................................4 9 6.11. 6.1 1. Manifold Manifol d Piping Pipi ng ..............................................................................................................4 9 6.12. 6.12 . Control Valve Stations Station s .............. ...................... ............... .......... .......... .............. .............. .............. ........... ............ ............... .............. .............. .......... .....5 ..51 1 7.
Pipe Pi pe Suppo Sup port rts s .......................................................................................................................... 52
8.
Joints Join ts and Specia Spe ciall Compone Comp onents nts (Includ (In cluding ing Blanks) Blan ks)...... ............ ............ ............ ............ ............ ............ ........... ...........53 ......53 8.1. 8.1 .
9.
Flange Flan ge Protec Pro tector tors..................... s..........................................................................................................5 .....................................................................................5 4
Valving Valv ing .......................................................................................................................................5 6 9.1.
Chokes............................................................................................................................56
10. Vents Ven ts and Drains Dra ins ............ .................. ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ........... .......... .......... ..........57 .....57 11. Branch Bran ch Connect Conn ections ions ............ .................. ............ ............ ............ ............ ............ ........... ........... ............ ............ ............ ............ ............ ............ ............ ........... .........57 ....57 12. Models .......................................................................................................................................5 7 13. Piping Pip ing Insula Ins ulatio tion n .....................................................................................................................5 8
© Mobil Oil,1998
3 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
13.1. 13.1 . Insulating Insulati ng Materials ............ .................. ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ .......5 .59 9 13.2. 13.2 . Vapor Vapo r Barrie Bar rierr .......... ............... .......... .......... .......... ............... ............... .......... .......... .......... ............... ............... .......... .......... .......... ................ ................. ............59 ......59 13.3. H2S .................................................................................................................................. 59 13.4. 13.4 . Thickness of Insul In sulat ation ion ............ .................. ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............59 ......59
© Mobil Oil,1998
4 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
Table of Figures Figure Figur e 1: Example Flowsh Flo wsheet eet of a Simplified Simplif ied Productio Produ ction n System Syst em ........ ........... ....... ....... ....... ........ ....... ...... ..... ..24 24 Figure 2: Example 1: Flowsheet Showing the the Location of Pressure Breaks .... ...... .... .... .... ....2 ..27 7 Figure 3: Example 2: Required Pressure Breaks Brea ks with with Valve in Position 5...... 5........ .... .... .... .... .... .... 28 Figure 4: Example 3: Flowsheet Showing an an Acceptable Acceptable Alternative to the Location Location of Pressu Pre ssure re Brea Br eaks ks..... ........... ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ ............ .......... ...... ..29 29 Figure 5: Example 4: Another Acceptable Alternative to to the Location of Pressure Brea Br eaks ks............................................................................................................................ ............................................................................................................................ 29 Figure 6: Schematic Diagram Diagram Showing a Typical Typical Drain Drain Piping Arrangement (Courtesy of Parag Pa ragon on Enginee Eng ineering ring Services Service s , Inc.) Inc. ) ...... ......... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ..... ..42 42 Figure 7: Sectional View View of a Manifold Valve (Courtesy of National Supply Co.) .... ...... .... 51 Figure 8: Types o f Flange Protectors (Courtesy (Courtes y of Paragon Engineering Services, Inc.) In c.) ................................ ............................................................ ................................................................................................. ..................................................................... 55
© Mobil Oil,1998
5 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
Table of Tables Table 1: Thread Allowance for Pipe Wall Thickness Calculations, ASME B31.3.........13 Table 2: Minimum Yield Strength for Various Grades of Pipe..........................................15 Table 3: Basic Design Factor F ................................................................................................. 15 Table 4: Temperature Derating Factor, T................................................................................16 Table 5: Design Factors for Ste el Pipe Construction (Courtesy of ASME) ...................19 Table 6: Summary ASME Pressure Ratings Material Group 1.1 (Source: ASME B16.5) ............................................................................................................................. 22 Table 7: Pressure-Temperature Ratings (Metric Units) (Maximum Allowable Working Pressure in MPa) (Source: API SPEC 6A) ...........................................................23 Table 8: Pressure-Temperature Ratings (Customary Units) (Maximum Allowable Working Pressure in psi) (Source: API SPEC 6A) ............................................23
© Mobil Oil,1998
6 of 59
EPT 09-T-01
1.
Facilities Piping
July 1998 Draft
References The following publications form a part of this Practice. Unless otherwise specified herein, use the latest edition.
1.1.
MEPS–Mobil Engineering Practices
MP 00-P-04
Winterizing & Heat Tracing
MP 15-P-04
Centrifugal Compressors
MP 15-P-05
Reciprocating Compressors
MP 16-P-01
Piping-General Design
MP 16-P-30A
Piping - Materials and Service Classifications (M&R)
MP 16-P-31A
Piping-Classifications-(E&P, On/Offshore)
MP 16-P-40
Piping-Fabrication, Erection, Inspection, & Testing
MP 33-P-13
Electrical - MV Motor Control
MP 33-P-23
Electrical - Raceway & Cable Tray Installations
MP 70-P-06
Pressure Relief and Vapor Depressuring Systems
1.2.
Mobil Tutorials
EPT 04-T-06
Steam Systems
EPT 04-T-09
Cooling Water Systems
EPT 04-T-10
Utility Stations-Service Water, Steam, Air
EPT 04-T-13
Fuel Gas Systems
EPT 04-T-18
Instrument and Plant Air Systems
EPT 09-T-05
Piping-Code Selection Guide
1.3.
API–American Petroleum Institute
API RP 14C
Recommended Practice for Analysis, Design, Installation, and Testing of Basic Surface Safety Systems for Offshore Production Platforms Fifth Edition; Errata - 1994
API RP 14E
Recommended Practice for Design and Installation of Offshore Production
© Mobil Oil,1998
7 of 59
EPT 09-T-01
July 1998 Draft
Facilities Piping
Platform Piping Systems Fifth Edition API SPEC 5L
Specification for Line Pipe Forty-First Edition
API SPEC 6A
Specification for Wellhead and Christmas Tree Equipment Seventeenth Edition
API STD 600
Steel Gate Valves - Flanged and Butt-Welding Ends, Bolted and Pressure Seal Bonnets Tenth Edition
1.4.
ASTM–American Society for Testing and Materials
ASTM A106
1.5.
Standard Specification for Seamless Carbon Steel Pipe for HighTemperature Service
ASME–Society of Mechanical Engineers
ASME B31.3
Process Piping
ASME B31.4
Liquid Transportation Systems for Hydrocarbons, Liquid Petroleum Gas, Anhydrous Ammonia, and Alcohols
ASME B31.8
Gas Transmission and Distribution Piping Systems
ASME B16.5
Pipe Flanges and Flanged Fittings NPS /2 Through NP S 24
ASME B16.34
Valves - Flanged, Threaded, and Welding End
ASME B16.47
Large Diameter Steel Flanges NPS 26 Through NPS 60
1.6.
CFR–U.S. Code of Federal Regulations
49 CFR 192
1.7.
1
Transportation, Subchapter D–Pipeline Safety, Transportation of Natural and Other Gases by Pipeline: Minimum Federal Safety Standards
MSS–Manufacturers Standardization Society of the Valves and Fittings Industry, Inc.
MSS SP-58
Pipe Hangers and Supports - Materials, Design and Manufacture
MSS SP-69
Pipe Hangers and Supports - Selection and Application
© Mobil Oil,1998
8 of 59
EPT 09-T-01
1.8.
Facilities Piping
NFPA–National Fire Protection Association
NFPA 321
2.
July 1998 Draft
Standard on Basic Classification of Flammable and Combustible Liquids (National Fire Codes, vol. 6)
General The design of piping systems for refineries, petrochemical plants, and onshore and offshore production and processing facilities contained in MP 16-P-01 shall be in accordance with requirements of this Tutorial, unless superceded by more stringent local regulations.
3.
Definitions Cold Spring
Cold spring is the intentional deformation of piping during assembly to produce a desired initial displacement or stress.
Facility
A site containing one or more pieces of equipment and interconnecting piping required to convey, separate, treat, process, pump or compress a fluid.
Fluid
Term used for a gas, liquid, vapor or mixture thereof.
Fluid Service
A piping code term that establishes the basis for design of a piping system and considers the combination of fluid properties, operating conditions and other factors. ASME B31.3 has fluid service classifications as listed below.
Fluid Service, Category D
A fluid service in which all of the following apply: 1. The fluid handled is nonflammable, nontoxic and not damaging to human tissues. 2. The design pressure does not exceed 1035 kPa (150 psi). 3. The design temperature is -29–186°C (-20–366°F).
Fluid Service, Category M
A fluid service in which the potential for personnelexposure is judged to be significant and in which a single exposure to a very small quantity of a toxic fluid, caused by leakage, ca n produce serious irreversible harm to persons on breathing or bodily contact, even when prompt restorative measures are taken.
Fluid Service, High Pressure
A fluid service for which the owner specifies the us e of Chapter IX of ASME B31.3 for piping design and construction.
Fluid Service, Normal
A fluid service pertaining to most piping covered by ASME B31.3, i.e. not subject to the rules of Category D, Category M or High Pressure Fluid
© Mobil Oil,1998
9 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
Service and not subject to severe cyclic conditions. Maximum Allowable Working Pressure (MAWP)
The maximum pressure at the coincident temperature to which a pressure retaining component can be subjected without exceeding the allowable stress of the material or pressure/temperature rating of the component.
NPS
NominalPipe Size in inches.
Piping
Assemblies of piping components used to convey, distribute, mix, separate , discharge, meter, control or snub fluid flows. Piping also includes pipesupporting elements, but not support structures.
Piping Components
Mechanical elements suitable for joining or assembly into pressure-tight fluid-containing piping systems. Components include pipe , tubing, fittings, flanges, gaskets, bolting, valves and devices such as expansion joints, flexible joints, pressure hoses, traps, strainers, in-line portions of instruments and separators.
Piping System
Interconnected piping subject to the same set or sets of design conditions.
Pressure Class
Pressure rating class designation (for example, Class 150, 300, 600, etc.) for pipe flanges and flanged fittings in accordance with the pressuretemperature rating criteria of ASME B16.5, ASME B16.47 and ASME B16.34.
Primary Piping
Piping that contains process streams during normal operation of a plant or that shall contain process streams during operation of standby or spare equipment. This includes bypass piping, alternative process connections , startup piping, chemical piping and auxiliary piping systems such as gland oil, seal oil, lubricating oil, fuel gas, fuel oil, heating or cooling oil, flushing oil, flare and blowdown piping and the like. Also considered to be primary piping is non-Category D fluid service utility piping that is essential to operation of the plant.
Safeguarding
Provision of protective measures of the types outlined in Appendix G of ASME B31.3, where deemed necessary.
Secondary Piping
Piping (other than specifically defined as primary piping) that is used as drains, vents, pumpouts, sample connections (if not in continuous service) and certain instrument leads that contain process streams only upon intermittent or occasional use and are not an integral or essential part of the process system.
Severe Cyclic Conditions
Those conditions in which the displacement stress (SE ) computed in accordance with ASME B31.3 exceeds 80 percent of the code allowable stress (SA ) and the equivalent number of cycles exceeds 7000.
Utility Piping
Includes piping systems for fluid such as air, nitrogen, cooling water, steam, etc.
© Mobil Oil,1998
10 of 59
EPT 09-T-01
4.
Facilities Piping
July 1998 Draft
Piping Design 4.1.
Design Basis •
ASME B31.3 does not require a margin between maximum operating and design conditions. However, it does not permit continuous operation of a piping system at conditions exceeding design conditions . Therefore, the design conditions (pressure, temperature, location of spec . breaks, etc.) shall be carefully determined, considering cost/risk factors. Short-term (upset) operation above the design conditions is acceptable within the limitations of ASME B31.3.
•
The design of piping shall provide for the most severe coincident (occurring at the same time) condition of temperature, pressure and loading. The most severe condition is that which results in the greatest required component thickness and highest-pressure rating. When two or more conditions exist , they shall be separately evaluated using design pressure, design temperature and loadings applicable to each case.
•
In determining the operating pressure and temperature of a piping system, variations may be expected because of operating fluctuations, other than upsets. When establishing maximum operating conditions, these fluctuations shall be considered as well as liquid static head, fluid friction losses under clean and fouled conditions, pump and compressor characteristics and pressure pulsations.
•
For design pressures of 3450 kPa (500 psi) or less, the design pressure is generally set at 10 percent or 210 kPa (30 psi) above the maximum anticipated operating pressure, whichever is greater.
•
For design pressures greater than 3450 kPa (500 psi), setting the design pressure 10 percent higher than the operating pressure may result in unjustifiable costs, particularly if higher flange ratings are required. For such piping systems, each system shall be evaluated in order to establish a reasonable design pressure rather than setting a fixed percentage over the maximum operating pressure. The design of a centrifugalpump discharge line shall be at least equal to the pump shutoff pressure.
•
The design temperature shall be the highest or lowest temperature to which the piping system is subjected plus a margin to cover uncertainties in temperature prediction. The following are examples of conditions that may determine the piping system design temperature:
−
In hot service (above ambient temperature), use the maximum expected operating temperature plus a minimum of 25°C (45°F) as a safety factor.
−
For cold service (below ambient temperature), use the minimum expected operating temperature minus a minimum of 5 °C (10°F) as a safety factor.
−
The maximum temperature that can occur when bypassing a heat exchanger or cooler for cleaning.
© Mobil Oil,1998
11 of 59
EPT 09-T-01
4.2.
Facilities Piping
July 1998 Draft
−
A high metal temperature on uninsulated pipe due to solar radiation.
−
The maximum metal temperature that can occur during steamout or decoking operations.
−
When flanges, valves and other components are not insulated, the temperature allowance for uninsulated components described in ASME B31.3 shall not be used without Mobil approval. (Note: Many times, operating plants will decide to insulate these components at some later date).
Sizing Criteria General rules for line sizing are listed in MP 16-P -01, Section 3.2 and Appendix B. The rules shall be applicable in most normal situations, but may not be suitable for all cases . Hydraulic calculations shall be performed to confirm the total pressure drops and pressure balance within the piping system, regardless of whether the lines meet the allowable pressure drop and velocity criteria given in MP 16-P-01.
4.3.
Pressure Design General rules for pressure design of pipe and other components are listed in MP 16-P-01, Section 3.3. Pressure classes, wall thickness and material selection of pipe and other components shall be determined using design conditions. When the calculated wall thickness considering manufacturers' under-allowance (mill tolerance) exceeds the nearest commercially available wall thickness by a few thousandths of an inch, the corrosion allowance may be adjusted subject to Mobil approval.
4.4.
Static and Dynamic Analysis •
Piping systems shall have sufficient flexibility to prevent thermal expansion or contraction from causing:
−
Failure of piping or supports from overstress or fatigue
−
Leakage at joints
−
Detrimental stresses or distortion in piping and valves or in connected equipment
•
When the routing of a piping system does not inherently provide adequate flexibility, the needed flexibility shall be provided by expansion bends, loops or offsets. Bellows expansion joints are the least preferred means of providing required flexibility and they shall not be used without prior Mobil approval.
•
In addition to static stress analysis , piping systems shall be reviewed for the possibility of flow- induced vibration, pressure pulse induced vibration, hydraulic surge (water hammer) and slug flow. This includes, but is not limited to, compressor piping, reciprocating pumps, high-velocity gas lines (including relief valve discharge lines), loading lines, seawater lines, liquid lines with quick closing valves, etc.
© Mobil Oil,1998
12 of 59
EPT 09-T-01
4.5.
July 1998 Draft
Facilities Piping
Pipe Wall Thickness Equations 4.5.1.
ASME B31.3 The wall thickness required by ASME B31.3 can be calculated for a given pipe by:
t = t c + t th +
100 2(S t E L + Pi Y ) 100 - Tol Pi d o
Where: t
=
Required pipe wall thickness to be specified when ordering the pipe, mm (in).
tc
=
Corrosion allowance, mm (in), normally 1.3 mm (0.05 in) for carbon steel.
tth
=
Thread or groove depth, mm (in) (Table 1).
Pi
=
Internal design pipe pressure, kPa (psig).
do
=
Pipe OD, mm (in).
St
=
Allowable stress for pipe material at design temperature, kPa (psi); See ASME B31.3, Appendix A.
EL
=
Longitudinal weld joint factor, dimensionless.
=
1.00 for seamless.
=
0.85 for electrical resistance welded ERW pipe.
=
Coefficient.
=
0.4 for ferrous materials below 900 °F.
=
Pipe manufacturer's allowed wall thickness tolerance.
=
12.5 percent for API SPEC 5L pipe up to 20 in diameter.
=
10 percent for API SPEC 5L pipe greater than 20 in diameter.
Y
Tol
Table 1: Thread Allowance for Pipe Wall Thickness Calculations, ASME B31.3 Nominal Pipe Size
t tn (in)
1
/4 – /8
3
0.05
1
/2 – 3 /4
0.06
1–2
0.08
© Mobil Oil,1998
13 of 59
EPT 09-T-01
July 1998 Draft
Facilities Piping
Nominal Pipe Size 1
2 /2 –20
t tn (in)
0.11
The code requires that the specified wall thickness be sufficient that, even with the wall in an assumed corroded condition where a thread or groove is cut, the hoop stress shall not exceed the allowable . For this reason, tc and tth shall be added to the thickness required by hoop stress alone. Pipe is manufactured to meet a nominalwall thickness. The finished pipe can have slightly less than the specified wall thickness as long as the pipe meets the nominalwall thickness and tolerance requirements of the code under which the pipe is manufactured (normally ASTM A106 or API SPEC 5L). For ease in picking a pipe wall thickness, tables such as Table 2.5 in API RP 14E are published, giving the maximum allowable working pressure for standard pipe diameters and wall thickness.
||Start E&P Only 4.5.2.
ASME B31.8 and 49 CFR 192 1. The wall thickness specified by ASME B31.8 and by 49 CFR 192 for a given pipe can be calculated by:
t=
Pi d o
2(FE L TS y )
t
=
Required pipe wall thickness to be specified when ordering the pipe, mm (in).
Pi
=
Internal design pipe pressure, kPa (psig).
do
=
Pipe OD, mm (in).
Sy
=
Minimum yield strength of pipe material, kPa (psi); Table 2.
F
=
Design factor, dimensionless (Table 3).
EL
=
Longitudinal weld joint factor, dimensionless.
=
1.00 for seamless , ERW and flash weld.
=
0.80 for furnace lap and electrical fusion welded pipe.
=
0.60 for furnace buttwelded pipe.
=
Temperature derating factor , dimensionless (Table 4).
T
© Mobil Oil,1998
14 of 59
EPT 09-T-01
July 1998 Draft
Facilities Piping
Table 2: Minimum Yield Strength for Various Grades of Pipe Grade
Minimum Yield Strength, psi
API 5L-B
35,000
API 5LX-42
42,000
API 5LX-46
46,000
API 5LX-52
52,000
API 5l X-60
60,000
API 5L X-65
65,000
ASTM A-106B
35,000
ASTM A-333-6
35,000
Note: For additionalinformation see ASME B31.8, Appendix D.
Table 3: Basic Design Factor, F Location Class
Class Location
Design Factor, General Description (see F Note)
(B31.8 Definition)
(DOT CFR 192)
Location Class 1, Division 1
Not Applicable
0.80
Based on actual operating conditions
Location Class 1, Division 2
Class Location 1
0.72
Sparsely populated areas, farmland, deserts
Location Class 2
Class Location 2
0.60
Fringe areas around cities and towns
Location Class 3
Class Location 3
0.50
Residentialand industrial areas.
Location Class 4
Class Location 4
0.40
Dense areas with multi-story buildings
NOTE : These descriptions are general in nature. A more specific description of locations for use of the different factors is included in ASME B31.8 and Department of Transportation requirements.
© Mobil Oil,1998
15 of 59
EPT 09-T-01
July 1998 Draft
Facilities Piping
Table 4: Temperature Derating Factor, T °
4.5.2.1.
Temperature, F
Derating Factor
-20 to 250
1.000
300
0.967
350
0.933
400
0.900
450
0.867
Threaded Pipe
ASME B31.8 does not have a section on threaded or grooved joints; it assumes that all pipe is welded. If threaded pipe is used, consideration shall be given to adding an allowance for thread or groove depth, as specified in ASME B31.3 (Table 1).
4.5.2.2.
Corrosion Allowances
Most gas transmission lines handle a relatively "clean" product and so no specific wall thickness allowance is suggested for internal corrosion in ASME B31.8. In chemical plants and refineries a more corrosive product is normally handled. ASME B31.3 specifically states that an allowance shall be included for corrosion and erosion. API RP 14E suggests that a corrosion/mechanical strength allowance of 1.25 mm (0.05 in) be used for carbon steel piping. This has become more or less a standard for production facility piping. In sour service most operators increase the corrosion allowance to 2.5 mm (0.10 in) (see MP 16-P-01).
4.5.2.3.
Safety Factors
ASME B31.8 recognizes that some gas transmission lines are located in sparsely settled areas where the cost of failure is low, while others are located in the middle of suburban areas where the potentialfor loss of life is greater and still others are located next to large concentrations of people where the risk to life is even greater. Thus, along the length of a gas transmission line, several different safety factors may be appropriate. This is considered by multiplying the pipe yield strength by a factor appropriate for a specific risk rather than specifying a single allowable stress for the material. Factors range from the most liberal (F = 0.80) to the most severe (F = 0.40). The greater the consequence of failure, the lower the design factor and thus the greater the required wall thickness.
© Mobil Oil,1998
16 of 59
EPT 09-T-01
Facilities Piping
4.5.2.4.
July 1998 Draft
Location Class
•
Table 3 shows in generalterms the location class and design factor, F, to use in different instances. A more specific description of locations for use of the different factors can be found in ASME B31.8 and 49 CFR 192. To determine the location class, it is necessary first to define a location class for the area in question. Unfortunately, the definition of location class and even terminology is somewhat different between ASME B31.8 and 49 CFR 192. ASME B31.8 applies to gathering lines offshore and onshore, unless within a city or subdivision. For pipelines located within a city or subdivision, local city, county or state codes apply. ASME B31.8 defines location class in terms of a "one-mile section."
•
To calculate the one-mile section layout, use a section one mile long and one-quarter mile wide along the pipeline route, with the pipeline on the center of the section. Count the dwellings intended for human occupancy. Each separate dwelling unit in a multiple dwelling building is counted as a separate building intended for human occupancy.
•
Before 1989, ASME B31.8 designated the design factor by a construction type as either A , B, C or D. In 1989, ASME B31.8 was revised and the term "construction type" was eliminated. The new designation is called the Location Class.
•
There are five classes of locations for ASME B31.8:
4.5.2.4.1.
Location Class 1–Division 1
This design factor (F) of 0.80 is based on actual gas pipeline operational experience at operation levels in excess of those previously recommended by ASME B31.8.
4.5.2.4.2.
Location Class 1–Division 2
Any one mile section that has 10 or fewer buildings intended for human occupancy. This includes areas such a wastelands, deserts, rugged mountains , grazing land and farmland.
4.5.2.4.3.
Location Class 2
Any one mile section that has more than 10 but fewer than 46 buildings intended for human occupancy. This includes fringe areas around cities and towns, industrialareas, ranch or country estates.
4.5.2.4.4.
Location Class 3
Any one mile section that has 46 or more buildings intended for human occupancy. This includes suburban housing developments, shopping centers, residential areas and industrial areas.
© Mobil Oil,1998
17 of 59
EPT 09-T-01
Facilities Piping
4.5.2.4.5.
July 1998 Draft
Location Class 4
Includes locations where multistory buildings are prevalent, traffic is heavy or dense and where there may be numerous other underground utilities.
4.5.3.
49 CFR 192 •
49 CFR 192 applies to gas transportation lines, including pipeline facilities within the limits of the outer continental shelf. The code applies to onshore gas gathering and distribution lines located within cities, towns, villages, residential or commercial areas , subdivisions and business or shopping centers. This code does not apply to gathering lines outside of these areas or to offshore gathering lines upstream of facilities where hydrocarbons are produced, separated, dehydrated or processed.
•
As previously mentioned, 49 CFR 192 uses different terms than ASME B31.8 to describe the populated areas that are used in determining the design factor, F. 49 CFR 192 uses a term ca lled the "class location."
•
The class location onshore for the Department of Transportation (49 CFR 192) is determined by a class location unit , which is an area extending 220 yards on either side of the centerline of any continuous 1 mile length of pipeline. Each separate dwelling unit in a multiple dwelling unit building is counted as a separate building intended for human occupancy.
•
There are four classes of locations for 49 CFR 192:
4.5.3.1.
Class Location 1
Includes areas that contain 10 or fewer buildings intended for human occupancy.
4.5.3.2.
Class Location 2
Includes areas where there are more than 10 but fewer than 46 buildings intended for human occupancy.
4.5.3.3.
Class Location 3
Includes areas where there are 46 or more buildings intended for human occupancy or where the pipeline lies within 100 yards of a building or a small, well-defined outside area such as a playground, recreation area, outdoor theater or other place of public assembly that is occupied by 20 or more persons for at least five days a week for 10 weeks in any 12 month period.
4.5.3.4.
Class Location 4
Includes areas where buildings with four or more stories above ground are present.
© Mobil Oil,1998
18 of 59
EPT 09-T-01
July 1998 Draft
Facilities Piping
•
There are several class boundaries. When a cluster of buildings intended for human occupancy requires a Class 2 or Class 3 location, the location ends 220 yards from the nearest building in the cluster. A Class 4 location ends 220 yards from the nearest building with four or more stories above ground.
•
The design factor for both ASME B31.8 and 49 CFR 192 is a function of the location class (or the class location). In populated areas, however, a different design factor may be required for pipelines located near roads, highways and railroads. Table 5 shows the required design factor for both codes to be used for various locations . 49 CFR 192 requirements allow some exceptions to these design factors. Specifically, a design factor of 0.60 is used for pipe located on offshore platforms including risers or facilities sited in inland navigable waters. A design factor of 0.54 is used for pipe that has been subjected to cold expansion to meet the specified minimum yield strength and is subsequently heated, other than by welding or stress relieving, to a temperature higher than 482 °C (900°F) for any period of time or is heated above 316 °C (600°F) for more than one hour.
Table 5: Design Factors for Steel Pipe Construction (Courtesy of ASME) Facility
Location Class 1
2
3
4
Div. 1
Div. 2
0.80
0.72
0.60
0.50
0.40
a. Private roads
0.80
0.72
0.60
0.50
0.40
b. Unimproved public roads
0.60
0.60
0.60
0.50
0.40
0.60
0.60
0.50
0.50
0.40
a. Private roads
0.80
0.72
0.60
0.50
0.40
b. Unimproved public roads
0.72
0.72
0.60
0.50
0.40
0.72
0.72
0.60
0.50
0.40
Pipelines, mains and service lines Crossings of roads, railroads without casing:
c. Roads, highways or public streets with hard surface and railroads Crossings of roads , railroads with casing:
c. Roads, highways or public streets with hard surface and railroads
Parallel encroachment of pipelines and mains on roads and railroads : a. Private roads
0.80
0.72
0.60
0.50
0.40
b. Unimproved public roads
0.80
0.72
0.60
0.50
0.40
© Mobil Oil,1998
19 of 59
EPT 09-T-01
July 1998 Draft
Facilities Piping
Facility
Location Class 1
2
3
4
Div. 1
Div. 2
c. Roads, highways or public streets with hard surface and railroads
0.60
0.60
0.60
0.50
0.40
Fabricated assemblies
0.60
0.60
0.60
0.50
0.40
Pipelines on bridges
0.60
0.60
0.60
0.50
0.40
Compressor station piping
0.50
0.50
0.50
0.50
0.40
Near concentration of people in Location Class 1 and 2
0.50
0.50
0.50
0.50
0.40
4.5.4.
•
In different local governmental jurisdictions there may be slightly different definitions for the location class (or the class location). Some jurisdictions also differentiate between sweet and sour services. The designer is cautioned to become familiar with the Department of Transportation, and localcodes and standards before completing the design.
•
ASME B31.8 includes a table that lists allowable working pressures for various pipe grades and design factors for normally available pipe diameters and wall thickness for use in gas transmission and distribution piping.
ASME B31.4 The equation for required wall thickness in ASME B31.4 is the same as that in ASME B31.8, except that the safety factor is fixed at F = 0.72 and there is no temperature derating factor . This is because the consequences of a leak in an oil line are not as severe as the consequences of a leak in a gas line. It is possible for a gas leak to lead quickly to an explosion and loss of life if a combustible cloud of gas comes in contact with a spark. An oil leak, on the other hand, provides a visual warning of its presence. It shall typically spread more slowly to a source of combustion, giving ample warning for personnel in the vicinity to escape. While it may catch fire, it is unlikely to result in an explosion. ASME B31.4 does not have a temperature derating factor ("T") since it states that it is only applicable to temperatures -29–121 °C (-20–250°F).
4.5.5.
Comparison of ASME B31.3 and ASME B31.8
If we compare the wall thickness required by ASME B31.3 and ASME B31.8 for piping in a c ompressor station, it can be seen that ASME B31.3 is more conservative than ASME B31.8, especially when higher yield strength pipe material is used. This difference creates a problem in choosing the interface between a production facility designed to ASME
© Mobil Oil,1998
20 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
B31.3 and a pipeline designed to ASME B31.8 or ASME B31.4. The location of the transition varies from company to company, but it is usually a t the plant fence for an onshore facility and at the first flange above the water on an offshore platform (see EPT 09-T-05).
End of E&P Only||
4.6.
Pressure Ratings When designing piping systems one shall consider piping components such as pipe flanges, fittings and valves. These piping components shall be able to withstand the stresses imposed by internal pressure. Unlike pipe, they are not straight cylinders but are of complex geometry and require a detailed study in order to determine the pressures they can withstand. Rather than requiring every designer to perform finite element analysis on each component, industry has developed standards for pipe flanges, fittings and valves. The goal of the standards is to provide interchangeability between manufacturers, set dimensional standards, specify allowable service ratings for pressure and temperature ranges, specify material properties and specify methods of production and quality control. ASME B16.5 and API SPEC 6A specifications are the most commonly used. By specifying a specific pressure rating class that is rated for a pressure equaling or exceeding the maximum working pressure of the particular piping system, the designer is assured that all flanges, fittings and valves furnished by any manufacturer shall contain the pressure and have interchangeable dimensions.
4.6.1.
ASME B16.5 ASME B16.5 has seven classes of flanges: 150, 300, 400, 600, 900, 1500 and 2500. Historically, the class designation was the allowable working pressure at 454°C (850°F). For example, the 300 ASME class rating had a primary pressure rating of 2068 kPa (300 psi) at 454°C (850°F). For all classes, the maximum non-shock pressure rating is higher at lower temperatures. Over time and with the development of new materials, the meaning of the pressure rating classes has changed and the class designation is no longer equal to the maximum working pressure. Table 6 is a listing of the maximum non-shock working pressure rating for Material Group 1.1, as listed in the 1996 edition of ASME B16.5. Material Group 1.1 includes most of the carbon steels commonly used in production facility piping. Table 6 lists temperatures up to 93.3°C (200°F) since most facility piping operates at temperatures less than 93.3 °C (200°F).
© Mobil Oil,1998
21 of 59
EPT 09-T-01
July 1998 Draft
Facilities Piping
Table 6: Summary ASME Pressure Ratings Material Group 1.1 (Source: ASME B16.5) Class
°
°
Temperature F -20 to Temperature F 100 to 100 Pressure (psig) 200 Pressure (psig)
150
285
260
300
740
675
600
1480
1350
900
2220
2025
1500
3705
3375
2500
6170
5625
Table 2 in ASME B16.5 contains additional information for other materials and for temperatures up to 815.6 °C (1500 °F). The pressure rating at any specific temperature above 37.8 °C (100°F) can be determined by interpolation. The pressure rating of a piping system is set either by the wall thickness of the pipe or by the pressure rating of the valves and fittings. Note that in ASME B31.3 the allowable stress for most commonly used steels in production facility piping systems is constant through 204.4 °C (400°F) and in ASME B31.8 the temperature derating factor is 1.0 through 121.1 °C (250°F). Thus the pressure rating of a piping system may be set by the wall thickness of the pipe at low temperatures and by the pressure rating of the valves and fittings at a higher temperature. Although ASME Class 400 exists, it shall not be used in production facility design. Valves and fittings in this class are not readily available and so may cost more than those in Class 600.
4.6.2.
API SPEC 6A Like ASME B16.5, API SPEC 6A also has seven classes of flanges: 2,000, 3,000 , 5,000, 10,000, 15,000, 20,000 and 30,000. The API class designation is the maximum non-shock working pressure rating at 37.8 °C (100°F). For example, 2,000 API class has a pressure rating of 2,000 psi at 37.8 °C (100°F). API flanges are derated for temperature as shown in Tables 7 and 8. For more information, see API SPEC 6A.
© Mobil Oil,1998
22 of 59
EPT 09-T-01
July 1998 Draft
Facilities Piping
Table 7: Pressure-Temperature Ratings (Metric Units) (Maximum Allowable Working Pressure in MPa) (Source: API SPEC 6A) °
Temperature C
Flange Class 2000
3000
5000
(MPa)
(MPa)
(MPa)
-18 to 121
13.8
20.7
34.5
149
13.5
20.2
33.6
177
13.1
19.7
32.8
204
12.8
19.2
32.0
232
12.5
18.7
31.2
260
12.0
18.0
29.9
288
11.3
16.9
28.2
316
10.6
15.9
26.6
343
9.9
14.8
24.7
Table 8: Pressure-Temperature Ratings (Customary Units) (Maximum Allowable Working Pressure in psi) (Source: API SPEC 6A) °
Temperature F
Flange Class 2000
3000
5000
(psi)
(psi)
(psi)
0 to 250
2000
3000
5000
300
1955
2930
4880
350
1905
2860
4765
400
1860
2785
4645
450
1810
2715
4525
500
1735
2605
4340
550
1635
2455
4090
600
1540
2310
3850
650
1430
2145
3575
© Mobil Oil,1998
23 of 59
EPT 09-T-01
4.7.
Facilities Piping
July 1998 Draft
Determining Pressure Breaks 4.7.1.
Rules This Section describes a procedure for determining the design pressure for a specific segment of a piping system. Consider the case of a well with a shut-in tubing pressure of 69,000 kPa (10,000 psi) flowing through a choke to a series of successive separators to a tank as shown in Figure 1. The wellhead shall be designed to withstand 69,000 kPa (10,000 psi) internal pressure , but the tank is incapable of withstanding pressures much in excess of one atmosphere. Clearly, there shall be one or more locations in such a system where the design pressure (that is, the maximum pressure to which the piping can be subjected) is higher on the upstream side than it is on the downstream side. These locations , called "pressure breaks" or "spec breaks," occur at valves, control valves, chokes or other devices which can be shut to isolate one segment of the piping system from another.
Figure 1: Example Flowsheet of a Simplified Production System Since overpressure of a piping system is extremely dangerous and could lead directly to personnelinjury or death, the system shall be designed to withstand the maximum pressure it could be subjected to under any circumstance of inadvertent operation of a manual valve or control. That is, we cannot assume that a knowledgeable operator would never open or close valves in a sequence that could overpressure a segment of the piping system; even knowledgeable operators make mistakes in logic or in tracing out piping
© Mobil Oil,1998
24 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
to determine the correct valve to open or close. Similarly, we cannot depend on operational controls to function properly , since controls do fail and piping system failure due to overpressure can have very high costs. In determining the location of pressure breaks, the following rules shall be followed: 1. Any manual valve can be either open or closed. Use whichever condition creates the highest pressure level for the system. 2. Check valves leak and eventually allow pressure from downstream to leak back to the upstream position. 3. Allow pressure to equalize from one side to another. In addition, we shall assume that control valves fail either open or closed in such a manner as to subject the system to maximum pressure. 4. Shutdown systems can be in bypass and, by themselves, do not provide sufficient protection from overpressure. Some operators assume that two completely independent shutdown sensor valve combinations shall provide sufficient protection from overpressure to be acceptable in certain circumstances. (See API RP 14C for the case of protecting long flow lines from overpressure with two independent, fail-close shutdown valves.) These rules are based on years of operating experience with many production facility piping systems and reflect an industry consensus that the probability of the assumption occurring is too high to justify the cost of failure. If we make the assumption that no device will work to limit pressure, then it would be necessary to design the wellhead, separators and tank in Figure 1 for 69,000 kPa (10,000 psi). Therefore, we assume that relief valves work and that if they are sized correctly, they shall restrict the pressure in their portion of the system to the set pressure of the relief valve. This assumption is made because of the proven reliability of relief valves.
4.7.1.1.
Shutdown Sensor
In some cases, such as for facilities designed in accordance with API RP 14C, a high pressure shutdown sensor shall fail before pressure rises to a relief valve set point. This provides greater reliability and further reduces the risk of overpressure.
4.7.1.2.
Overpressure
In reality , the pressure in the piping system may exceed relief valve set pressure for a short period of time while the relief valve is handling its full design load.
•
The ASME Boiler and Pressure Vessel Code allows pressure to build up to 110–125 percent of s et pressure under certain conditions of relief.
© Mobil Oil,1998
25 of 59
EPT 09-T-01
Facilities Piping
•
July 1998 Draft
This overpressure is considered in the safety factors of piping wall thickness calculations and fitting class pressure ratings and need not be considered in determining the design pressure for the piping system.
4.7.1.3.
Types of Valves
It is imperative that system overpressure be prevented by a relief valve and not by a back pressure control valve. Relief valves are designed for rapid opening, with proven flow coefficients and set points that cannot inadvertently be adjusted. This is not true for a back pressure control valve, for which the response time, setpoint and percent opening can be easily and inadvertently adjusted.
4.7.2.
Procedure To determine the location of pressure breaks, a complete mechanical flow diagram (sometimes called a process and instrument diagram, or P&ID ) is needed. This diagram shall show schematically the process and the location of all equipment, valves, controls and instrumentation. 1. Starting at the lowest pressure relief valve (normally the pressure vacuum valve on a tank), proceed upstream through the piping system until reaching a manual valve, control valve or choke. 2. Apply the four rules to determine the maximum pressure the upstream side of this valve can experience. If this is higher than the pressure rating of the downstream pipe, then a pressure break occurs at this point. If not, continue upstream to the next device in the system and apply the four rules until a pressure break is located. 3. Continue upstream through each line in the process until all pressure breaks are located. This procedure is best explained by an example. In Figure 2 the relief valve on the low pressure separator protects it from seeing pressures in excess of 1400 kPa (200 psi). Thus the flanges and immediate piping around this vessel can be ANSI Class 150. Following the piping upstream to valve 4, it is se en that this valve can be closed when valve 1 is open. Since the control valve and the check valve can communicate pressure, the maximum pressure valve 4 can be subjected to is set by the next relief valve upstream, or 10,200 kPa (1480 psi). Thus valves 1 through 4, as well as all the flanges and piping around the HP separator, shall be rated ASME Class 600.
© Mobil Oil,1998
26 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
Figure 2: Example 1: Flowsheet Showing the Location of Pressure Breaks Next, following the inlet from the LP separator upstream to the manifold valves, it is seen that all manifold valves could be closed, subjecting those on the flow lines from high pressure wells to 34,500 kPa (5000 psi) and from other wells to their shut-in tubing pressure (SITP). Following the inlet line from the HP separator upstream, pressure breaks are required as shown. In Figure 3 a valve is installed at position 5. This requires the pressure breaks as shown. Valves B, D and F shall be rated 5000 AP I because of the possibility of 5, B and D being closed when A, E and F are open.
© Mobil Oil,1998
27 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
Figure 3: Example 2: Required Pressure Breaks with Valve in Position 5 This situation is not practical because of the 5000 API rating required for the control station. Two alternatives can be proposed without violating any rules. These are shown in Figures 4 and 5.
© Mobil Oil,1998
28 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
Figure 4: Example 3: Flowsheet Showing an Acceptable Alternative to the Location of Pressure Breaks
Figure 5: Example 4: Another Acceptable Alternative to the Location of Pressure Breaks © Mobil Oil,1998
29 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
These examples are shown to help to explain how to apply the rules of Section 4.7 of this MEP and not to make any point regarding the proper way to design a specific situation. The important point is that in complex piping systems, care shall be taken to follow the procedure and rules properly and to choose the pressure break locations carefully. Often such an analysis leads to a re-evaluation of the proper location of valves in a piping system.
5.
Piping Layout and Arrangement 5.1.
5.2.
General •
Piping shall be run overhead throughout a unit except in freezing climates, where water, drainage and pumpout lines shall be underground (below the frost line) to the maximum extent possible. Proper corrosion protection shall be applied to underground piping.
•
Equipment subject to damage by heat, such as motor-operated valves, shall not be located where heat can exceed the design temperature of the equipment. Avoid routing lines containing cold high-vapor-pressure fluids near uninsulated hot lines or equipment, especially suction lines to pumps handling such fluids.
•
Avoid routing lines with flanged joints, threaded connections, high radiant heat or high-pressures near instrument/electrical cable trays.
•
Expansion bends shall be located in a horizontal plane and clear of any accessway. Underground expansion bends require expansion pits. Where expansion pits are provided, suitable anchors shall be furnished to ensure that the pipe expansion is contained within the pit dimensions.
•
Tank piping shall be designed with adequate loops and offsets to accommodate expected tank settlement. If this is not possible where large tank settlements are anticipated, ball joints with fire resistant packing or metal bellows expansion joints may be considered.
•
The installation arrangement of expansion joints shall be subject to Mobil approval and shall be reviewed by the joint manufacturer. This approval and review shall conside r service conditions, anchors, guides, supports, piping configuration and all necessary calculations.
Maintenance and Operability Piping shall be arranged to allow removal of equipment without removing or proving temporary support of equipment block valves. Removable pipe details shall be provided where required for equipment removal or maintenance.
© Mobil Oil,1998
30 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
To the extent possible , manually operated valves shall be located so that handwheels/handles are operable from a platform or grade level. If handwheels/handle s are more than 1.8 m (6 ft) above a platform or grade level, the valves shall be equipped with gear operators, extension stems or chain operators.
6.
Design Considerations for Specific Piping Systems 6.1.
Compressors •
Special precaution is necessary in the design of the piping at or near compressors to reduce fatigue failures. The piping shall have the minimum of overhanging weight. Braces shall be provided as needed to reduce vibration. Full penetration buttwelds shall be used wherever feasible, including fittings such as branch connections , etc.
•
To avoid damage to centrifugal compressors, a time delay shall be incorporated into the circuit of centrifugal compressors when needed to ensure that valve closing is not complete until the compressor has slowed sufficiently to prevent compressor damage should surge occur during the coastdown period.
6.1.1.
Suction Piping •
Knockout drums shall be provided upstream of all compressors, except those handling gases with no possibility of condensate (most air compressors, for example). Compressor suction piping between the knockout vessel and the compressor shall be designed with a straight length equal to or exceeding that required by the manufacturer and also designed to prevent trapping or collecting liquid. If this is not reasonable, additionalknockout equipment shall be installed.
•
Piping shall slope continuously downward from the knockout vessel to the compressor suction connection. As a n alternative , and depending on the location of the compressor suction valve, piping shall slope from the valve to the compressor suction on one side and from the valve to the knockout vessel on the other side. Valves shall be located only in horizontal piping.
•
The intake filter-silencer for an air compressor shall be located in a position that prevents the entrance of dust, moisture or corrosive gases.
•
Air compressor suction piping between the filter-silencer and compressor connection shall either be epoxy-coated steel, hot-dip galvanized steel or stainless steel. Other permanent, corrosion-resistant materials may be used subject to Mobil approval. A suction line valve (usually a butterfly valve) shall be provided as part of the compressor package for startup purposes on all centrifugal air compressors.
© Mobil Oil,1998
31 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
•
Suction strainers shall be provided in the suction lines to all compressors in accordance with Section 11 of MP 16-P-01. All screens and filters shall be sufficiently reinforced to prevent their collapse/failure and entry into the compressor. All strainers shall be installed as close to the compressor as feasible .
•
When temporary suction strainers are used, pressure gauge taps shall be provided upstream and downstream for commissioning of compressor. When the temporary strainers are removed, the tapped connections shall be plugged and seal-welded in accordance with MP 16-P-40.
•
Compressor piping shall be cleaned in accordance with MP 16-P-40.
• No hose shall be used in lube oil and seal oil piping.
6.1.2.
Emergency Isolation Valves •
•
Requirements for emergency isolation valves at reciprocating compressors are generally specified/reviewed by Lost Prevention and/or rotating equipment specialists. In general, the following isolation valves are required:
−
Reciprocating compressors over 200 horsepower in hydrocarbon or toxic service shall have emergency isolation valves on the suction and discharge sides. Where the discharge goes to two different locations , isolation valves are required in both discharge lines. Valves shall be in accordance with MP 16-P-30A (M&R) or MP 16P-31A (E&P).
−
Reciprocating compressors under 1000 horsepower may have handoperated emergency isolation valves in sizes up to and including NP S 8. The valves shall be remotely operated if they are NPS 10 and larger, or if they are of a size that requires a gear operator. Hand-operated emergency valves shall be located at least 9 m (30 ft) horizontally from the compressor. Remote-operated emergency shutoff valves may be located closer than 9 m (30 ft); however, the control shall be installed at least 15 m (50 ft) from the compressor.
−
Reciprocating compressors 1000 horsepower and larger shall have remotely operated emergency isolation valves. A pushbutton station with a position indicator shall be located in the area of the compressor, at least 15 m (50 ft) away and in a readily accessible location not expected to be exposed to fire. A second control station shall be installed in the control room.
−
Fireproofing of remote-control emergency valve assemblies is required. All resilient seated emergency control valves shall be of a fire safe design.
Requirements for emergency isolation valves at centrifugal compressors are generally specified/reviewed by Lost Prevention and/or rotating
© Mobil Oil,1998
32 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
equipment specialists. In general, the following isolation valves are required:
6.1.3.
−
Centrifugal compressors in all sizes shall have a remote-operated emergency block valve in the suction piping. The compressor suction isolation valve, if remotely operated, can also be the emergency valve. Necessary safeguards for the discharge piping are discussed in Section 6.1.3 of this MEP.
−
Location requirements for motor-operated remote valves and for the pushbutton stations shall be the same as those for reciprocating compressors.
−
Fireproofing of remote-control emergency valve assemblies is required. All resilient seated emergency control valves shall be of a fire safe design.
Reciprocating and Positive Displacement Compressors •
An isometric drawing of all compressor piping shall be prepared to enable the vendor and/or Mobil to perform an analysis of pipi ng pulsation. The piping shown shall extend from knockout vessel to the compressor suction and from the discharge through any cooler to the next major vessel. The piping shall include relief valves, bypasses and recirculating lines. The drawing shall be fully dimensioned and show all supports, guides and anchors.
•
The design for pulsation limitations shall be in accordance with MP 15P-05 and subject to approval by Mobil and the compressor manufacturer. The use of restrictions in the piping to reduce pressure pulsation shall be subject to Mobil approval.
•
The suction and discharge piping of reciprocating compressors shall be securely anchored to control vibration. The anchoring method used shall be approved by Mobil.
•
If suction valve unloaders have not been provided for compressor startup, a valve bypass shall be installed from suction to discharge within the suction and discharge block valves. If required by the project specifications, bypass valves shall be manually operated and used only after maintenance for initial run- in at no load. The configuration of bypass piping and valve location shall prevent the collection of liquid with the valve closed.
•
The selection of any check valve used in the discharge of a reciprocating compressor shall be subject to Mobil approval. The recommended valve type is a reed plate type, such as manufactured by Hoerbiger or Ibach.
•
As a minimum, the suction line immediately upstream and adjacent to the suction pulsation damper for compressors handling gas at or near its dew point shall be heat-traced or steam jacketed for approximately 6 or 8
© Mobil Oil,1998
33 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
diameters to vaporize liquid traveling on the pipe wall. Rotary compressors in similar service but not requiring suction pulsation damper equipment shall be provided with liquid removal facilities immediately adjacent to the compressor suction connection. In freezing climates, heat tracing of the suction piping in such service shall be required from the knockout drum up to and including the pulsation dampers.
•
6.1.4.
6.2.
Relief valves shall be provided upstream of the first valve on the discharge line of positive displacement compressors where necessary to prevent excessive pressure or stalling if either is harmful to the equipment. The discharge from relief valves shall not be returned to the suction line or suction drum.
Centrifugal Compressor Piping •
Bottom-connected compressor suction lines shall contain a sump or boot with a gauge glass and drain located at the low point in the line below and as close to the compressor as feasible.
•
Check valve selection shall be in accordance with MP 16-P-30A (M&R) or MP 16-P-31A (E&P). Check valve installation shall be as close to the nozzle as feasible to reduce possible damage to the compressor during surge conditions and to prevent backflow during an emergency.
•
If silencers are required, they shall be installed in the suction and discharge piping as close to the compressor nozzles as feasible but downstream of the check valve on the discharge side. In order to optimize the layout, the silencers may be arranged with side or end connections. Silencer shells and flanges shall conform to the appropriate piping classifications .
•
Interconnecting oil piping between the compressor, turbine and lube oil console shall comply with the piping specifications for the console (see MP 15-P-04). No elastometric or metal hose shall be used for lube or seal oil piping.
•
Low points in the discharge line from an oil-lubricated air compressor shall be avoided to eliminate the possibility of lube oil being trapped and subsequently ignited. If low points are unavoidable , they shall be provided with drains. The recommendations for auxiliary piping contained in Section 6.2.3 of this MEP are also applicable to centrifugal compressors.
Pump Piping •
Block valves shall be provided in the suction and discharge lines of all pumps. The valves shall be located within 3 m (10 ft) of the pump nozzles. Connections for vents, drains and pressure gauges shall be located inside these block valves.
•
Expansion joints shall not be used on pump suction and discharge lines without Mobil approval. An exception is pumps taking suction from a cooling tower basin, where an
© Mobil Oil,1998
34 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
expansion joint is frequently needed on the short suction line from the basin. For such pumps , an expansion joint is generally not needed on the discharge side of the pump if the piping contains at least one 90 degree elbow before going underground.
6.2.1.
Suction Piping •
Suction piping for pumps shall be arranged s o that the flow is as smooth (non-turbulent) as possible a t the pump suction nozzle . Suction piping shall be designed to avoid pocketing vapor or gas. Any reduction in suction line size required at horizontal pump nozzles shall be made with an eccentric reducer positioned as follows: flat side on top for horizontal runs and vertical runs approaching the nozzle from below; flat side on the bottom for vertical runs approaching the nozzle from above. A concentric reducer shall be used if the reduction occurs immediately adjacent to an elbow on the downcomer from an overhead header. Longradius elbows shall be used in all suction lines.
•
For double-suction centrifugal pumps there shall be at least 5 pipe diameters between a side-suction nozzle and any upstream elbow, unless the elbow is in the vertical plane. There shall also be at least 5 pipe diameters between a top-suction nozzle and any upstream elbow in a vertical plane parallel to the pump shaft.
−
Where no reducer is installed between the pump flange and the elbow, a straight run at least 5 pipe diameters long shall be provided. A valve may be installed within the run. In a horizontal line, the valve stem for gate valves shall be installed in the vertical-up position.
−
Where a reducer is installed between the pump flange and the elbow, a straight run at least 2 pipe diameters long (based on the larger pipe diameter) shall be provided. A reducer next to the pump flange is considered to be equivalent to 3 large diameters.
•
Suction lines containing cold high-vapor-pressure fluids shall not be routed near hot lines or equipment. Provision for venting blocked-in fluids shall be made.
•
Suction block valves shall be line size. However, where a centrifugal pump's suction nozzle is smaller than the suction line size, the block valve may be the same size as the pump suction nozzle if pressure drop considerations permit and the velocity through the valve does not exceed 3 m/s (10 ft/sec).
•
Permanent strainers shall be installed in suction lines to pumps handling fluids that may contain solids (such as coke fines), unless the pump is specifically designed to handle such material. They shall also be installed on other pumps if required by MP 16-P-40 or the P&IDs. All strainers shall be designed to withstand the pressure forces from a blocked mesh.
© Mobil Oil,1998
35 of 59
EPT 09-T-01
Facilities Piping
•
6.2.2.
July 1998 Draft
Temporary strainers shall be installed in the suction lines of all pumps , except for pumps where permanent strainers are installed. Strainers shall have a free area at least twice the pump suction area and a mesh size approved by the pump manufacturer. If a cone-type strainer, the cone shall point upstream. All strainers shall be located in the suction line between the pump and the block valve and as close to the pump as feasible. Suction lines shall be designed so that the temporary strainers may be easily installed and removed without springing the pipe. Strainers shall be sufficiently rigid and resistant to corrosion to prevent their failure and entry into the pump.
Discharge Piping •
A check valve shall be installed in the discharge line of each centrifugal or rotary pump. The check valve shall be located between the pump and the block valve. If pressure drop considerations permit , the block and check valves may be one size smaller than the discharge line size, but not smaller than the pump discharge nozzle. Check valves are usually not needed for reciprocating pumps that have internalvalving that prevents backflow or for those that do not discharge into vapor or mixed-phase process conditions.
•
Check valve selection shall be in accordance with MP 16-P-30A (M&R) or MP 16-P-31A (E&P). Special attention is required for lines where quick closing (<10 sec) check valves may cause pressure surges (water hammer).
•
A drain shall be provided between the block and check valves in lines containing highly corrosive or toxic fluids, such as phenol, caustic or acid. For maximum drainage , the drain shall be on the check valve body above the closure member.
•
If a pump is expected to operate for extended periods at flowrates lower than the manufacturer's recommended minimum flowrate, it shall be equipped with either a flow-actuated recirculation line back to the point of suction or a flow-actuated shut-down switch. The minimum size of 3 the recirculating line shall be NPS /4 . The line shall be equipped with at least one block valve and an orifice sized to restrict flow to the recommended minimum flowrate of the pump.
•
Pumps that may be idle during plant operation and that have to start quickly shall be provided with warm-up lines if the pump design temperature exceeds 230°C (450°F) or if the process fluid will solidify at atmospheric temperature. Cooldown lines shall be provided for pumps operating at design temperatures less than 0°C (32°F). A warm-up line 3 shall consist of an NPS /4 (minimum) valved bypass around the pump discharge block and check valves. The warm-up lines shall be heat traced if the process fluid will solidify a t atmospheric temperature.
•
A relief valve shall be provided upstream of the first valve on the discharge line of positive displacement pumps. Normally, the relief valve shall discharge into the pump suction line. In services where a
© Mobil Oil,1998
36 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
serious heat buildup may occur at the pump during blocked discharge, or where the pressure breakdown will liberate gas, the relief valve discharge line shall be installed to relieve to an unblocked suction source, such as a tank or an accumulator. The relief valve may only be eliminated if the pump and the equipment downstream of the pump are designed to withstand the shutoff or stalling pressure.
6.2.3.
6.3.
Auxiliary Piping for Pumps •
Auxiliary piping shall conform to the applicable line class specification (see MP 16-P-30A [M&R] or MP 16-P-31A [E&P]) and shall be arranged and valved to permit easy removal and maintenance of equipment.
•
Cooling water piping shall be provided with block valves at each pump. In freezing climates, a valved bypass shall be provided so that a flow can be maintained when the block valves are closed.
•
Pump spill pans/baseplates, casing drains and vents shall be piped to the appropriate drainage or flare system, as shall cooling water that is not returned to the cooling tower. Vents on vacuum service pumps, however, shall be piped to the vapor space on the vacuum vessel. Fluids shall not be discharged onto pump bases.
•
If a pump is steam traced or steam jacketed, the trap and trap piping shall be located so that they do not interfere with pump maintenance.
Steam Turbine Piping •
Steam driver piping, including drains , shall be designed to avoid pockets and to minimize condensation. Inlet piping to turbines and other steam drivers shall branch from the top of the supply header and contain a block valve in a horizontalrun near and above the header.
•
Connections to exhaust headers shall be made to the top of the header unless the line from the driver is at least one size smaller than the header. If it is smaller, it is permissible to make a centerline connection to the side of the header, provided that such routing does not obstruct space in a pipe rack available for future lines.
•
Provisions are generally made for bleed warming steam into turbines and other steam drivers.
•
Piping connections for pressure indicators shall be provided in supply and exhaust piping of turbines driving centrifugal compressors.
6.3.1.
Turbine Inlet Piping •
For initial throttling of general-purpose turbines, a valve shall be installed at the turbine inlet. For inlet piping NPS 6 and larger, a gate valve is generally acceptable . For NPS 4 and smaller inlet piping, a globe valve shall be used.
© Mobil Oil,1998
37 of 59
EPT 09-T-01
Facilities Piping
6.3.2.
6.3.3.
July 1998 Draft
•
Inlet piping to each turbine shall be equipped with a commercial in-line steam strainer with a scale trap section. The drain connection shall be equipped with a steam trap and a free blow connection. For critical turbines, the separator shall have bypass piping.
•
Special-purpose turbines driven with super-heated steam shall have a connection immediately upstream of the separator for turbine washing. The connection shall be NPS 4 with a valve and blind flange.
Turbine Exhaust Piping •
A gate valve shall be provided in the exhaust line of each steam driver that does not exhaust directly to the atmosphere or directly into an individual condenser. This gate valve shall be installed close to the steam driver so that the position of the gate is obvious to the operator whenever he or she is in a position to operate the inlet valve.
•
Exhaust lines from turbines that exhaust directly to the atmosphere shall be provided with exhaust heads and silencers.
•
Exhaust piping from condensing turbines shall be equipped with a waterseal relief valve. It shall be sized for maximum steam flow through the turbine nozzles and set for atmospheric pressure.
•
Where there is a block valve in the exhaust line from a steam driver and the steam driver casing (and any expansion joints) is not designed for full steam supply pressure, a spring-loaded relief valve shall be provided on the exhaust piping between the driver and the first block valve. Relief valves shall be sized for the full steam capacity of the driver and set for the turbine case design pressure.
•
Each relief valve shall be provided with a separate discharge line arranged to discharge steam to the atmosphere as directly as possible and supported so that minimum load is carried by the relief valve. The top of the discharge pipe shall be at a height that prevents the discharge of steam from creating hazards, such as burns , frozen condensate on walkways or reduce visibility. Each discharge pipe shall be provided with a weep hole to prevent the accumulation of water above the relief valve. In many areas it may be necessary to route the drain to the nearest drain funnel.
Auxiliary Piping •
Trapped drain piping (steam trap) shall be provided at the lowest point of each turbine casing drain.
•
Untrapped drain piping shall be provided at the lowest point of the steam end of reciprocating pumps and compressors.
•
Drain piping from turbine shaft packing glands and from governor valve packing glands shall be connected to an open drain system. These drain lines shall be run separately.
© Mobil Oil,1998
38 of 59
EPT 09-T-01
6.4.
Facilities Piping
July 1998 Draft
Vessel Piping 6.4.1.
6.4.2.
Arrangement •
Piping at vessel nozzles shall be arranged so that blanks can be readily installed and valves easily removed for maintenance. Blanks shall be in accordance with Section 7 of MP 16-P-01.
•
For economy and ease of support, piping at towers shall be run parallel to and as close as feasible to the tower.
•
The piping designer shall coordinate piping requirements with the designers of the instruments, structures and vessels to achieve the optimum nozzle location so that valves, instruments and blanks are accessible from grade or platforms and do not obstruct passageways.
•
Process requirements usually govern the location of the valves in vessel piping. However, block valves shall generally be provided at vessel nozzles for all piping connections , except as follows:
−
Connections for vapor and reboiler lines, unless the reboilers are in parallel and need to be cleaned onstream
−
Connections for sidestream drawoff lines (except water drawoffs)
−
Furnace transfer lines to vacuum vessels
−
Connections to lines containing block valves located within 9 m (30 ft) in a horizontal direction from the vessel nozzle
•
Valves, flanged joints and threaded joints shall not be located inside vessel skirts.
•
Piping connections shall not be made to manway covers, other than on coke drums. (The bottom manway cover [or bottom head] on coke drums is the preferred location for the main charge, quench and drain nozzles.)
Emergency Shutoff Valves •
Emergency shutoff valves shall be provided on outlets below normal operating liquid levels on all process vessels where the volume of liquid 3 exceeds 75 M (2000 U.S. gallons) in the bottom or side draws, and where one or more of the following conditions exist :
−
The liquid conforms to NFPA 321, Classes 1A and 1B. These classifications include liquids with a flash point below 23 °C (73°F) and a boiling point below 38 °C (100°F) and liquids that are heated above their flash point. For complete specification refer to NFPA 321.
−
The temperature is 260 °C (500°F) or higher.
© Mobil Oil,1998
39 of 59
EPT 09-T-01
Facilities Piping
−
July 1998 Draft
The pressure is 2070 kPag (300 psig) or greater.
•
Emergency shutoff valves shall be located as close to the vessel as feasible, but no farther than 9 m (30 ft) measured horizontally from the side of the vessel. The total pipe length from the nozzle to the valve shall not exceed 15 m (50 ft).
•
Emergency shutoff valves shall be operable from grade of platforms as follows:
•
−
Access to a manually operated valve shall be considered adequate if it can be operated from a platform no more than 6 m (20 ft) above grade and access to the platforms is by stairway. Access to the platform by ladder shall not be permitted.
−
Valves NPS 8 and smaller may be manually operated. They may also be fitted with extension spindles or angle drives to fulfill the criteria of operability from grade. The use of chain wheels for this service shall be subject to Mobil approval.
−
Valves NPS 10 and larger shall be power-operated. Their controls shall be located in a place at grade safe from fire exposure. Electric cables, motor operators, valve operators, pistons, etc. shall be fireproofed. Resilient seated valves shall be of a fire safe design.
A control valve shall satisfy the requirements for an emergency block valve if the following conditions are met:
−
It is not equipped with a stop to prevent full closure.
−
It meets the accessibility requirements in the above paragraph.
−
It will provide a tight shutoff.
−
It will close on failure of the air supply.
−
It meets the fire resistance requirements in the above paragraph.
•
The pipe material and wall thickness from the vessel to the emergency block valve shall be provided a corrosion resistance no less than that of the vessel or vessel liner.
•
Emergency shutoff valves need not be installed in thermo-syphon reboiler circuits if the corrosion resistance of the piping is not less than that of the vessel.
•
If the liquid from a side draw pan flows into the bottom of a second vessel (such as a stripper) and the total liquid in the drawoff pan plus that 3 in the bottom of the second vessel exceeds 75 M (2000 U.S. gallons), then an emergency valve shall be installed in the bottom outlet line on the second vessel provided one of the three conditions noted in the first paragraph above exists. However, if a control valve in the side draw line between those vessels meets the requirements above, an emergency
© Mobil Oil,1998
40 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
block valve is not required in the second vessel outlet unless the liquid in 3 the bottom of that vessel exceeds 75 M (2000 U.S. gallons ).
6.4.3.
Vents and Drains •
Atmospheric vents on vessels shall be equipped with blinded or plugged block valves.
•
All vessel drains discharging into a sewer or open drain shall have permanent piping arranged to permit the visual observation of flow (if permitted by environmentalrules). Vent and drain connections shall be sized so that the water used for a hydrostatic test or for flushing ca n be drained off without pulling a vacuum.
•
Vessel drain lines shall not be used for steam-out connections.
•
Drains used only during shutdown periods shall be provided with plugs or blanks. Vents and drains tied into closed drain systems shared with equipment of a higher working pressure shall be equipped with check valves. Vents and drains from equipment containing water or water vapor shall not be tied into low-temperature of LPG/LNG vent or drain systems.
•
If vessel drain valves are used often, they have a tendency to erode out. As the valve is opened and closed, solid slurry abruptly flows across the valve and creates an erosive action. Figure 6 shows a tandem valve arrangement to minimize this potential problem. To drain the vessel, the throttling valve is closed and one or more drain valves are opened, with no flow going through them. The throttling valve is then opened. To stop draining the throttling valve is closed, flow goes to zero and the drain valves are shut. The throttling valve shall eventually cut out, but it can be repaired easily without having to drain the vessel.
© Mobil Oil,1998
41 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
Figure 6: Schematic Diagram Showing a Typical Drain Piping Arrangement (Courtesy of Paragon Engineering Services, Inc.) •
Vessel drain systems can be very dangerous and deserve careful attention. There is a tendency to connect high-pressure vessels with low pressure vessels through the drain system. If a drain is inadvertently left open, pressure can communicate through the drain system from the high pressure vessel to the low-pressure vessel. In such a system, the low pressure vessel relief valve shall be sized for this potential gas blowby condition.
•
The liquid drained from a vessel may flash a considerable quantity of natural gas when it flows into an atmospheric drain header. The gas will exit from the piping system to the atmosphere at the nearest possible location. Thus, the sump collecting vessel drains shall be vented to a safe location as well as being designed for gas blowby.
•
Open gravity drains shall not be combined with pressure vesseldrain systems . The gas flashing from vessel liquids may exit an open drain system at any point and create a hazard.
•
On open drain piping leaving buildings, a liquid seal shall be installed as further protection to assure that gases flashing from liquids from other locations in the drain system will not vent from the system in the building.
•
The elevation of gravity drain systems shall be checked carefully to assure that liquids will flow to the collection point without exiting the piping at an intermediate low point (see MP 16-P-01).
© Mobil Oil,1998
42 of 59
EPT 09-T-01
Facilities Piping
6.4.4.
6.5.
July 1998 Draft
Steamout and Pumpout •
If steamout is specified on the P&IDs, permanent NPS 11 /2 or larger steamout connections shall be provided for all vessels not equipped with a process steam connection. Steamout connections shall consist of a block valve at the vessel, a flanged check valve, a removable spool with bleeder valve and a second block valve. Steam inlets to vessels shall be designed so the line can be drained of condensate prior to being placed into service.
•
Process steam connections shall consist of a block valve at the vessel, a spool with bleeder and a single-seated automatic or manual control valve. A block valve shall also be installed at the steam header takeoff.
•
Pumpout piping shall be provided for all vessels in accordance with the P&IDs. Where feasible, process pumps and lines shall be used for pumpout.
•
The pumpout header shall have a classification covering the highest temperature and pressure encountered in any branch connection, and shall be run at an elevation to permit gravity drainage from the vessel.
Fired Heater Piping 6.5.1.
Process Piping •
Lines, in which coke formation or fouling of tubes is anticipated, shall be designed and constructed to facilitate planned methods of mechanical cleaning.
•
Unless otherwise shown on the P&IDs, permanent steam/air decoking and/or pigging connections shall be made to the process piping on heaters in crude, vacuum, coker and visbreaker units. Dropout spools shall be provided for all decoking connections, except for those steam connections that are also installed for steamout operations.
•
Blanks shall be provided at the inlet and outlet of each heater. On heaters with parallel coils (passes), blanks are required to separate the coils for decoking purposes. Each of the parallel coils require steam/air decoking connections.
•
The decoking manifold shall be located above the blowdown drum so that the effluent coke line can slope toward the drum. Steam and air valves shall be located near peep doors for tube observation. Spool pieces shall be installed at heater inlet and outlet connections to provide observation of coke buildup in heater tubes.
•
When not provided on the heater coils, flanged vent and drain 1 connections (NPS 1 /2 minimum) shall be installed in the piping. These connections shall be equipped with a valve and a blind flange. If feasible, these connections shall be used for pressure testing the coils.
© Mobil Oil,1998
43 of 59
EPT 09-T-01
Facilities Piping
6.5.2.
July 1998 Draft
•
A check valve shall be installed at the tower/reactor end of the heater transfer line to prevent backflow if a heater tube ruptures on catalytic hydrodesulfurization (CHD), hydrotreater or hydrocracker units. A check valve shall be provided at other locations or units if shown on the P&IDs. The transfer-line check valve shall be a full-port swing check valve with buttweld ends, bolted cover, no external moving parts, conforming to API STD 600. The seating surfaces, pivot pins, pivot pin bushings and disc center pivot surfaces shall be hardfaced. The valve shall be installed in horizontalpiping as near to the tower/reactor as possible.
•
If blowdown facilities are required by the P&IDs, blowdown valves shall be sized for a flow area approximately equal to that of the largest tube in the coil, but shall not be smaller than NPS 2. Where there is a likelihood of coke formation, manually operated valves shall be globe types with the pressure against the bottom of the disc.
Burner Fuel Piping •
Heaters shall have manual burner control valves for fuel oil, fuel gas and steam. Burner valves shall be located so that adjustments can be made while observing the flame from a working level without entering the area beneath the heater. The piping layout shall allow easy access for burner tip cleaning.
•
On all heaters and fired boilers, burner and pilot safety shutoff valve actuation shall be at least 15 m (50 ft) away from and adjacent to the purge steam actuation.
•
Gas distribution headers a t heaters shall be arranged for uniform distribution, with burner line valves connected to the top of the header. The headers may be located at an elevation above or below the burners to suit the individual condition. However, access to the burners shall not be obstructed. Drains shall be installed at low points on the headers and on the leads from the header to the burners. Valves for throttling fuel gas shall be of the globe or needle design. On/off valves may be ball valves, but they shall not be used for throttling. A block and bleed valve (with blank) shall be provided in the fuel gas line to each heater.
•
Fuel oil headers shall be circulated, self-cleaning and void of dead ends. All residualfuel oil line shall be heat traced and insulated.
•
The fuel oil header at each heater shall be located at an elevation above the burners, with globe-type burner line valves connected to the side or top of the header and the lines draining to the burners.
•
If provided, atomizing steam for burners shall be supplied from a pressure-controlled header that is properly drained and trapped to prevent condensate from entering the burners. When steam-out connections are specified, they shall be provided for each burner oil line adjacent to the oil valve. Lines to burners shall be run from the top of the steam header.
© Mobil Oil,1998
44 of 59
EPT 09-T-01
Facilities Piping
•
6.5.3.
6.6.
July 1998 Draft
Piping arrangements for steam atomization shall incorporate safeguards to prevent fuel oil from entering the steam system. Unless otherwise specified, a ball check valve shall be installed in each steam connection at the burner, with the valve in the up-flow position.
Utilities Piping •
Purge and steamout lines to heaters shall be supplied from a remote manifold located at grade level and in a "safe" area. A trap shall be installed on each line to the heater. The manifold shall be located a minimum of 15 m (50 ft) horizontally from the nearest purge steam discharge point.
•
Emergency purging steam lines are generally piped to header boxes and combustion chambers so that purge steam can be applied separately and equally to each box or chamber. Each valve shall be identified at the remoter header in relation to the header box or combustion chamber it supplies. Purge steam to header boxes is not needed if welded return bends are used.
•
Permanently piped steamout connections shall be provided to the inlet and outlet of each heater pass containing liquids or liquid/gas mixtures. Steam at 690–1380 kPag (100–200 psig) is normally used. A check valve and double blocks with bleed valve shall be provided at all steamout connections . From the heater coil, the arrangement shall be block valve, bleeder, check valve, block valve. The final block valve may be omitted if the steam pressure will at all times be higher than the process pressure.
•
A properly trapped service steam loop shall be installed around each heater (to supply steam utility stations at grade) and on all working platform levels. The number and locations of steam hose stations shall be stated in the project specifications. Sootblowers, if installed, shall be supplied with a block and bleed valve at the steam connection to the blower.
•
Header box drains (NPS 2, minimum) shall be piped to an oily water sewer.
Relief Valve Piping •
Relief valve piping shall be in accordance with MP 70-P -06 and Section 5.7 of MP 16-P-01.
•
Bellows type expansion joints shall not be used in pressure relief discharge piping or flare lines.
•
Sparing of relief valves and blocks for relief valves shall follow the requirements in MP 70-P-06. When blocks are provided for relief valves, the block valves shall be equipped with a padlock and chain or interlocking device.
© Mobil Oil,1998
45 of 59
EPT 09-T-01
6.7.
Facilities Piping
July 1998 Draft
Utility Piping •
Utility stations (including hose requirements) for service water, steam, air and nitrogen shall be in accordance with EPT 04-T-10. Each steam and nitrogen hose outlet shall be provided with a steel gate valve. Air and water outlets shall have bronze or aluminum-bronze ball valves.
•
Steam piping systems shall meet the requirements of EPT 04-T-06. Condens ate collection systems shall meet the requirements of EPT 04-T-06.
•
Utility stations shall remain in service at all times, except when isolated for repairs. Steam shall be supplied by a source that will not be closed off during shutdowns.
•
The steam supply for smothering, snuffing, space heating and protective heating shall be connected to a source that will not be shut off during shutdowns or when the steam to a piece of equipment is shut off.
•
Whenever steam is exhausted to the atmosphere, the line shall be fitted with an exhaust head with a drain to a sewer. The exhaust system shall be reviewed to ensure that sound levels and flow induced vibration levels are within acceptable limits.
•
The ends of steam mains and all low points in steam lines (except steam tracer lines) shall be provided with drip legs. The maximum distance between drip legs shall be 90 m (300 ft).
•
Steam traps shall be provided for the removal of condensate from collection points. Each trap shall serve only one collection point. Whenever possible , the steam trap shall be installed below and close to the equipment or piping.
•
Hot oil and steam tracing systems shall conform to MP 00-P-04. Cooling water systems shall conform to the requirements of EPT 04-T-09.
•
All water piping shall be located or protected to prevent freezing. In cold climates, headers and branches that are outdoors and in intermittent service (but not below the frost line) shall be traced and/or insulated. Tracing and insulating water lines with low continuous flowrates shall also be considered.
•
Low point drains shall be provided so that any water line located above the frost line can be drained when it is shut down. A vent shall be provided for ea ch high point between block valves on large water mains. These vents shall be protected from mechanicaldamage and from freezing, as required.
•
Provisions shall be made to ensure that water is available for sanitary facilities, safety showers and eyewash fountains during unit shutdowns.
•
Fuel gas systems shall conform to the requirements of EPT 04-T-13. Instrument air and plant air systems shall conform to EPT 04-T-18.
•
Plant air piping shall either slope downward toward dry drums and moisture traps or shall be horizontal. Branch connections on all air headers shall be into the top of the pipe. Block valves shall be provided in all branch lines from air headers.
© Mobil Oil,1998
46 of 59
EPT 09-T-01
6.8.
Facilities Piping
July 1998 Draft
Exchanger Piping 6.8.1.
Shell-and-Tube Exchanger Piping •
A backwash connection shall be provided in the cooling water inlet piping to each exchanger or group of exchangers operating in series. The connection shall be line size, but not greater than NPS 6. It shall be equipped with a quick opening valve, e.g. butterfly valve and a blind flange, and shall be located between the exchanger and the inlet block valve. These connections shall not be installed on closed-loop systems using tempered water.
•
Flanged chemical cleaning connections shall be provided between the block valve and the exchanger nozzles when indicated on the P&IDs. These connections shall generally be N PS 3 for exchangers with an inside diameter of 700 mm (28 in) and larger, and NPS 2 for smaller exchangers. It is permissible to combine chemical cleaning and backwash connections, provided the larger size is used.
•
On any exchanger that will be taken out of service for cleaning or repair while the unit is running, all piping connections shall be equipped with a block valve and a blanking location. Process and water piping to shelland-tube units shall be arranged to permit easy removal of shell covers, channel covers, channels and bundles. This shall be accomplished by providing a removable section of piping (other than at the block valve and blanking location).
•
For single -shell heat exchangers , all vent and drain connections shall be provided with valves equipped with plugs or blanks. Funnels and pipe shall be provided to drain oil and chemicals to suitable sewers. For selfdraining stacked exchanger installations , drain valves shall be installed in the piping below the lowest exchanger.
•
Requirements for water lines are as follows:
−
Piping shall be arranged, or check valves shall be properly located, to permit water to remain in all units upon the loss of cooling water supply.
−
In areas where freezing can occur, provision shall be made for draining all water from a blocked exchanger and an NPS 1 valved bypass shall be installed to maintain flow in the water lines. The distance from the freeze protection bypass to the exchanger block valve shall be minimized. Drains shall be located to obtain maximum drainage of the exchangers and piping.
•
Symmetrical piping shall be used to keep the pressure drop equal in lines to and from exchangers operating in parallel.
•
All streams to be heated shall enter at the bottom of the exchanger and all streams to be cooled shall enter at the top of the exchanger.
© Mobil Oil,1998
47 of 59
EPT 09-T-01
Facilities Piping
6.8.2.
6.8.3.
6.9.
July 1998 Draft
•
Condenser piping shall be sized to provide sufficient velocity to carry condensate along with the vapors. Pockets shall be avoided in these lines.
•
A check valve shall be provided in the steam supply line to an exchanger if the steam side has a lower pressure than the other side.
Air Cooled Heat Exchanger Piping •
Inlet and outlet headers shall not be located over or under the tube areas.
•
Branch piping between the headers and the exchange header boxes shall accommodate the thermal expansion of the headers. The centerline of each bay shall be assumed to be an anchor point, unless the exchanger manufacturer provides different information. The piping design shall be coordinated with the exchanger design, so nozzle loads are minimized.
•
The branches to exchanger bays that may be removed from service for repair/cleaning while the unit is operating shall be provided with valves and figure eight blanks. Access to these valves and blanking locations shall be provided. The layout of headers and branches shall allow the removal of any header bundle or cleaning in place.
•
Piping connections to split header bundles shall incorporate enough flexibility to accommodate the thermal expansion produced by differential temperatures within the bundle .
Plate Heat Exchanger Piping •
If any connection to a plate exchanger is located on the removable cover plate, flanged piping sections shall be provided to allow cleaning.
•
Self-cleaning filters shall be provided in the inlet piping if the size of solid particles cannot be accommodated by the plate heat exchanger.
Storage Tank Piping 6.9.1.
Pressurized Storage Tank Piping •
Flanged joints shall be minimized under the storage tank. Atmospheric vents and drains shall be located or piped so that, if they leak or ignite, the flames will not impinge on the storage vessel.
•
Fill and suction lines shall be provided with remotely operated shutoff valves, and these shutoffs shall have locally operated emergency overrides.
•
All butane and propane storage tanks shall be provided with a sufficient number of relief valves so that, in the event of relief valve leakage, it will be possible to shut off the defective valve and replace it while the vessel is in service.
© Mobil Oil,1998
48 of 59
EPT 09-T-01
Facilities Piping
•
6.9.2.
6.10.
July 1998 Draft
−
Each relief valve shall be provided with an upstream block valve (Orbit or equal tight shutoff) and, if connected to a closed system, a downstream block valve.
−
Each block valve shall be equipped with a padlock and chain or interlocking device.
In areas where freezing is likely, water drawoff piping shall be provided for storage spheres. All piping and valves shall be heat traced.
Atmospheric Storage Tank Piping •
All storage tank nozzles below the roof line shall be equipped with a steel block valve.
•
Storage tank piping shall be designed to accommodate any expected tank settlement, thermal expansion and seismic load without overstressing the tank or the piping.
Underground Piping Generally, hydrocarbon and chemical piping shall be placed abovegrade. When they shall be buried, their location shall be marked by signs spaced along the route of the line. Additionally, local regulations such as secondary containment (if required) shall be followed.
6.11.
Manifold Piping The purpose of a manifold is to allow a number of input lines to be routed to two or more output lines (sometimes called "headers" or "logs"). The routing of input lines to output lines is determined by the positions of a series of valves.
6.11.1.
Velocities Typically, the velocities in manifold piping are high and therefore erosional flow can be a problem. For this reason target tees are usually installed, and headers may be looped to reduce velocities. Each inlet source shall have a check valve installed and the manifold shall be pressure rated for the shut-in pressure of the source. Also, the inlet sources shall be spaced far enough apart to allow the valves to be actuated without interference. For 51–102 1 mm (2–4 in) lines the spacing shall be 38–51 mm (1 /2 –2 in) center to center. To minimize the length of the manifold , it is possible to arrange headers in a verticalplane and enter from both sides on a staggered pattern.
6.11.2.
Branch Connections Any branch connections to the manifold shall follow the operating company's pipe, valve and fitting specification. Often a header diameter of at least twice
© Mobil Oil,1998
49 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
the nominal diameter of the input lines is chosen because the operating company's piping specifications will not allow weld-o-lets to be installed where the inlet is more than half the diameter of the header. If there are any plans for future expansion, weld- o-lets, flanges and blind flanges can be preinstalled on the header.
6.11.3.
Valves and Connections The most common type of valves used for manifolds are ball or plug valves since they minimize the interference between slots. Flanged connections are the most common. Clamp-type connections also can be used, but they may be more susceptible to leaks due to misalignment and tend to be more costly. Flanged connections require all valves to be unbolted from the inlet to make sufficient room to remove one valve. Specially designed valves and connections may minimize the space required and reduce costs. Figure 7 shows one such valve arrangement.
•
Flow enters the inlet that contains a block valve and a check valve and is directed either up to a test header or down to one or more group headers.
•
A divert valve with an actuator can be used as shown in the figure for automatic well test (AWT).
•
Such valve arrangements have the drawback of having non-standard dimensions, requiring the use of a single supplier for parts.
© Mobil Oil,1998
50 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
Figure 7: Sectional View of a Manifold Valve (Courtesy of National Supply Co.) Headers shall be equipped with a blind flange on the end for future additions and for cleanout, and taps shall be provided for pressure gauges. If the header is for an offshore platform, a drip pan is required. To reduce costs, it may be wise to consider a shopfabricated skidded unit.
6.12.
Control Valve Stations Whenever it is necessary to control the process level, pressure, temperature, etc., a control station is installed. A control station may be as simple as a single control valve or it may include severalcontrol valves, block valves, bypass valves, check valves and drain or vent valves.
© Mobil Oil,1998
51 of 59
EPT 09-T-01
7.
Facilities Piping
July 1998 Draft
•
Where there is a control valve, block valves are often provided so the control valve can be maintained without having to drain or bleed the pressure from the vessel and downstream piping. Typically, a safety-systems analysis also would call for a check valve at this point to prevent backflow. Drain or vent valves shall be installed to drain liquid or bleed pressure out of the system so that the control valve c an be maintained.
•
Bypass valves are sometimes installed to allow the control valve to be repaired without shutting in production. On large, important streams the bypass could be another control valve station. Manual bypass valves are more common in smaller facilities. The bypass valve could be a globe valve if it is anticipated that flow will be throttled through the valve manually during the bypass operation, or it could be an on/off valve such as a ball, plug or gate valve, if the flow is to be cycled. Because globe valves do not provide positive shutoff, sometimes there is a ball or other on/off valve piped in series with the globe bypass valve.
•
The piping system for any facility, other than the straight pipe connecting the equipment , is made up primarily of a series of control stations. Flow from one vessel goes through a control station and into a piece of pipe that goes to another vessel. In addition to considering the use of block valves, check valves, etc., all control stations shall be designed so that the control valve can be removed.
•
Any bypass valve shall be located above or on a level with the main control valve. If the bypass is below the control valve, it provides a dead space for water accumulation and corrosion.
Pipe Supports •
The layout and design of piping and its supporting elements shall mee t the objectives of ASME B31.3, Paragraph 321. Suggested pipe support spacing tables are listed in MP 16-P-01, Appendix C. If the contractors' tables are used, they shall be reviewed and approved by Mobil.
•
When it is anticipated that a line will deflect vertically as a result of thermal expansion or contraction (which could thereby unload some supports and overload others), spring supports shall be provided.
•
Supports shall be designed so they will not be disengaged by movement of the supporting pipe or structure. Unless approved otherwise by Mobil, all supports shall be designed to withstand the added load resulting from testing, erection and shipping, if applicable. This is particularly important for piping on offshore platforms that shall be shipped by water.
•
Spacing of overhead pipe supports shall be based on the piping size mix to secure maximum economy. Where support spacing exceeds allowable spans for small lines (NPS 2 and smaller), the lines shall be grouped (when feasible) to simplify supporting methods. To eliminate an intermediate support for a small line, it may be economical to increase line sizes.
•
Supports for piping near equipment shall be designed so that excessive forces and moments caused by temperature changes shall not be transmitted to the equipment. Piping entering vessels shall be supported from brackets attached to the vessel if vertica l expansion of either the vessel or the pipe will cause excessive loads on the vessel nozzle.
© Mobil Oil,1998
52 of 59
EPT 09-T-01
8.
Facilities Piping
July 1998 Draft
•
Piping sections requiring frequent dismantling for maintenance, such as for installation of blanks, shall be provided with permanent supports for the dismantled condition to maintain proper alignment.
•
Process and auxiliary piping shall be arranged and supported so that a minimum number of joints shall have to be disconnected (when removing equipment or components) and so that temporary supports shall not be required. Areas of particular concern are:
−
Auxiliary piping at pumps (arranged to facilitate removal of rotating elements)
−
Burner piping
−
Piping at control valves
−
Exchanger channels
•
MSS SP-58 support types 1, 2, 5, 6, 7, 9, 10, 11, 12, 15, 16, 19, 20, 23, 28, 29, 30, 41, 43 and 49 shall not be used. Guidance for selection and application of pipe hangers and supports ca n be found in MSS SP-69.
•
Pipe supports elements (for example, clamps, turnbuckles, U-bolts, saddles, etc.) are provided in carbon steel, ductile iron or malleable iron. The following limitations apply to these materials: Material
Temperature Range
Carbon steel
-29–343°C (-20–650°F)
Cast iron (see limitations below)
-29–205°C (-20–400°F)
Ductile and malleable iron
-29–205°C (-20–400°F)
21 /4 Cr – 1 Mo
-29–650°C (-20–1200°F)
304 or 316 stainless steel
-198–760°C (-325–1400 °F)
•
Cast iron shall not be used for pipe clamps, beam clamps , hanger flanges, clips , brackets and swivel rings. Cast iron supporting elements are also not permitted for use in any piping system that may be subjected to impact-type loading resulting from pulsation or vibration.
•
Pipe support elements that are welded directly to the pipe (for example, pipe shoes, saddles, trunnions, etc.) shall be of the same nominalmaterial as the pipe.
Joints and Special Components (Including Blanks) •
The number of non-welded (flanged and threaded) joints shall be kept to a minimum. Use of such joints shall be limited to those required for cleaning, maintenance, operation and inspection.
•
Secondary piping shall be separated from primary piping with block valve(s) that have the same specification as those valves used in the primary piping.
© Mobil Oil,1998
53 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
•
Piping requiring mechanicalcleaning for removalof solids buildup shall employ flanged fittings (such as tees and crosses) at changes in direction in lieu of pipe bends and buttwelding elbows. If pipe bends are used, they shall be of a radius suitable for the cleaning tool. The run of pipe between cleanout points shall be a maximum of 12 m (40 ft) if cleaned from one end, and 24 m (80 ft) if cleaned from both ends. Flanged removable spools shall be provided at cleanout points on long straight runs.
•
Permanent blanks shall be in accordance with MP 16-P-01, Section 7.
•
Thin plate blanks (maintenance isolation blanks) shall be used only for lines that are not under pressure and which shall be sealed off to permit inspection or welding during shutdowns.
8.1.
Flange Protectors The full faces of flanges never really touch due to the gaskets or rings that cause the seal. The space between the two flange faces is a very good spot for corrosion to develop, as shown in Figure 8. Flange protectors made of closed-cell soft rubber are sometimes used to exclude liquids from penetrating this area . Stainless-steel bands and grease fittings also are used.
© Mobil Oil,1998
54 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
Figure 8: Types of Flange Protectors (Courtesy of Paragon Engineering Services, Inc.) Closed-cell flange protectors are much less expensive than stainless bands. However, if not installed properly they can actually accelerate corrosion if a path is created through the material to allow moisture to enter. Flange protectors shall not be used in H 2 S service. They may trap small leaks of sour gas and keep them from being dispersed in the atmosphere. Also, many companies do not use flange protectors on lines containing flammable liquids . Liquids from a leaking flange can accumulate under the protective cover, producing a fire hazard.
© Mobil Oil,1998
55 of 59
EPT 09-T-01
9.
Facilities Piping
July 1998 Draft
Valving •
Valve stems and handles shall not project into passageways or be installed with the ste m inclined below the horizontal. See MP 16-P-01 for clearance and accessibility requirements.
•
Valves that are open to the atmosphere shall have their outboard connection either blinded or plugged.
•
Drain and bypass connections may be positioned in a valve body, where necessary, to simplify piping or to ensure complete drainage. The connection type (flanged, threaded, etc.) shall be consistent with those allowed by the governing piping line classification.
||Start E&P Only
9.1.
Chokes Fluid flows from a choke in a high-velocity jet. For this reason, it is desirable to have a straight run of pipe of at least 10–15 pipe diameters downstream of any choke, so that the jet does not impinge on the side of the pipe. Often, on high-pressure wells, two chokes are installed in the flow line: one a positive choke and the other an adjustable choke. The adjustable choke is used to control the flow rate. If it were to erode (cut out), the positive choke then would act to restrict the flow out of the well and keep the well from damaging itself. Where there are two chokes, it is good piping practice to separate the chokes by 10 pipe diameters to keep the jet of flow formed by the first choke from cutting out the second choke. In practice, this separation is not often done because of the expense of separating two chokes by a spool of pipe rated for well shut-in pressure. It is much less expensive to bolt the flanges of the two chokes together. No data have been collected to prove whether the separation of chokes is justified from maintenance and safety considerations. Whenever a choke is installed, it is good piping practice to install block valves within a reasonable distance upstream and downstream so that the choke bean or disc can be changed without having to bleed down a long length of pipeline. A vent valve for bleeding pressure off the segment of the line containing the choke is also needed. This is particularly true in instances where a positive choke is installed at the wellhead and an adjustable choke is installed hundreds of feet away in a line heater. If block valves are not installed downstream of the positive choke and upstream of the adjustable choke, it would be necessary to bleed the entire flow line to atmosphere to perform maintenance on either choke.
© Mobil Oil,1998
56 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
End of E&P Only||
10. Vents and Drains •
Vents that are provided for hydrostatic test purposes only do not require a valve and shall be provided with a seal welded solid plug, except Category D service where a properly tightened (threaded) solid plug is acceptable. Deletion of high point vent valves shall be approved by Mobil and shall have operations concurrence that valves will not be required during startup, operations and/or shutdown. Additionally , subject to approval by the local facility, hydrocarbon lines in Class 300 and lower having design temperatures between ambient and 200 °C (400°F), may have properly tightened (threaded) solid plugs. The metallurgy of the plugs shall be the same nominalmaterialas the pipe.
•
As an alternative to high point vents with seal-welded plugs, particularly in corrosive service, NPS 1 flanged connections may be used. Flanges shall have a minimum pressure class of 300.
•
All vents and drains that are open to the atmosphere shall be blinded or plugged.
11. Branch Connections •
ASME B31.3 permits branch connections to be made by a variety of methods, including tees, reducing tees, reinforced and unreinforced pipe-to-pipe fabricated connections, o-let fittings, etc. Typical branch tables are included in the line classes in MP 16-P-30A (M&R) and MP 16-P-31A (E&P). If the contractors' tables are used, they shall be submitted to Mobil for review and approval.
•
Care shall be exercised in the detail design of branch connections to prevent mechanic al damage or breakage due to vibration or excessive force. Connections that may require bracing or special types of connections include sample points, instrument takeoffs, relief valves, corrosion probes, and vent and drain connections (particularly where two block valves are used).
•
Flexibility shall be provided in branch connections, especially small connections such as drain and trap lines, instrument lines, etc., where piping is subject to large thermal movements. The preferred location for connections is near anchors or guides where the movements of the main line are the lowest.
12. Models •
When a plastic modelis used for a project, it shall be built to a minimum scale of 3/8 in:1 ft or 1:33 metric. Before the model is built , a detailed model specificati on shall be prepared by the contractor for Mobil approval.
© Mobil Oil,1998
57 of 59
EPT 09-T-01
Facilities Piping
July 1998 Draft
•
When a 3D computer model is used for a project, the software to be used requires Mobil approval. The system shall include clash/interference checking and walk-through capabilities.
•
As a minimum, the following items shall be shown on the model:
−
Piping NPS 2 and larger, with flanges and insulation as required. Piping shall be labeled with the line number and specification.
−
All valves, including handwheels or operators.
−
Criticalpipe supports, guides, restraints and anchors.
−
Instrument support stanchions and all instruments, including transmitters labeled for ready identification.
−
Drain hubs, catch basins, manholes and cleanouts.
−
Ladders, platforms and stairs.
−
Lighting equipment and electrical boxes.
−
Fixed hose reels.
−
Fixed fire water spray systems.
−
Fire fighting monitors.
−
Utility stations and safety showers.
−
All process equipment, properly labeled.
−
All package units.
•
Repetitive small piping assemblies, such a s burner manifolds, pump utilities, steam trap manifolds and similar arrangements shall be modeled separately only once. The scale of this 3 piping model shall be /4 in:1 ft, or 1:15 metric.
•
All specialty items shall be tagged.
•
The surface of a plastic model base shall show routing of all underground piping systems (including sewers) and all underground electric power and instrument signal transmission line banks. All underground piping shall be included in a 3D computer model.
•
Mobil personnel shall conduct a modelreview at agreed stages of completion.
13. Piping Insulation Pipe insulation is often required in piping systems that are either much cooler or much hotter than ambient temperature. Insulation is necessary for personnelprotection, to conserve energy or to guard against ignition. For temperatures above approximately 65°C (150°F), most operators provide insulation for personal protection. If the temperature exceeds 200 °C (400°F), insulation is usually
© Mobil Oil,1998
58 of 59
