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24539788 asme-book-2

  1. 1. Overview of Process Plant Piping System DesignParticipant’s Guide
  2. 2. CONTACT INFORMATION ASME Headquarters 1-800-THE-ASME ASME Professional Development 1-800-THE-ASMEEastern Regional Office Southern Regional Office8996 Burke Lake Road – Suite L102 1950 Stemmons Freeway – Suite 5037CBurke, VA 22015-1607 Dallas, TX 75207-3109703-978-5000 214-746-4900800-221-5536 800-445-2388703-978-1157 (FAX) 214-746-4902 (FAX)Midwest Regional Office Western Regional Office17 North Elmhurst Avenue – Suite 108 119-C Paul DriveMt. Prospect, IL 60056-2406 San Rafael, CA 94903-2022847-392-8876 415-499-1148800-628-6437 800-624-9002847-392-8801 (FAX) 415-499-1338 (FAX) You can also find information onNortheast Regional Office these courses and all of ASME,326 Clock Tower Commons including ASME ProfessionalRoute 22 Development, the Vice President ofBrewster, NY 10509-9241 Professional Development, and other914-279-6200 contacts at the ASME Web site……800-628-5981914-279-7765 (FAX) http://www.asme.orgInternational Regional Office 1-800-THE-ASME
  3. 3. Overview of Process Plant Piping System Design By: Vincent A. Carucci Carmagen Engineering, Inc. Copyright © 2000 by All Rights Reserved
  4. 4. TABLE OF CONTENTSPART 1: PARTICIPANT NOTES ..............................................................................3PART 2: BACKGROUND MATERIAL .................................................................................... 73 I. Introduction ....................................................................................................................... 73 II. General ............................................................................................................................. 73 A. What is a piping system .......................................................................................... 73 B. Scope of ASME B31.3............................................................................................. 73 III. Material selection considerations...................................................................................... 75 A. Strength................................................................................................................... 75 B. Corrosion Resistance .............................................................................................. 77 C. Material Fracture Toughness .................................................................................. 77 D. Fabricability ............................................................................................................. 78 E. Availability and Cost ................................................................................................ 78 IV. Piping Components........................................................................................................... 79 A. Fittings, Flanges, and Gaskets................................................................................ 79 B. Flange Rating .......................................................................................................... 85 Sample Problem 1 - Determine Flange Rating ................................................................. 88 Solution ............................................................................................................................. 88 V. Valves ............................................................................................................................... 89 A. Valve Functions....................................................................................................... 89 B. Primary Valve Types ............................................................................................... 90 C. Valve Selection Process ......................................................................................... 98 Exercise 1 – Determine Required Flange Rating ............................................................. 99 VI. Design ............................................................................................................................. 100 A. Design Conditions ................................................................................................. 100 B. Loads and Stresses............................................................................................... 101 C. Pressure Design of Components .......................................................................... 105 Sample Problem 2 - Determine Pipe wall thickness ....................................................... 110 Sample Problem 3 .......................................................................................................... 116 Exercise 2: Determine Required Pipe Wall Thickness .................................................. 121 VII. System Design ................................................................................................................ 122 A. Layout Considerations .......................................................................................... 122 B. Pipe Supports and Restraints ............................................................................... 123 C. Piping Flexibility..................................................................................................... 129 D. Required Design Information for Piping Stress Analysis ...................................... 132 E. Criteria for Allowable Equipment Nozzle Loads .................................................... 132 F. When Should A Computer Analysis Be Used ....................................................... 134 G. Design Considerations for Piping System Stress Analysis ................................... 134 VIII. Fabrication, Assembly, and Erection .............................................................................. 140 A. Welding and Heat Treatment ................................................................................ 140 B. Assembly and Erection.......................................................................................... 144 IX. Quality Control ................................................................................................................ 151 A. Inspection .............................................................................................................. 151 B. Testing................................................................................................................... 154 X. Other Considerations ...................................................................................................... 156 A. Nonmetallic Piping................................................................................................. 156 B. Category M Fluid Service...................................................................................... 157 C. High Pressure Piping............................................................................................. 158 XI. Summary......................................................................................................................... 160
  5. 5. Part 1:Participant Notes 3
  6. 6. OVERVIEW OF PROCESS PLANT PIPING SYSTEM DESIGN By: Vincent A. Carucci Carmagen Engineering, Inc. 1Notes: Piping System Piping system: conveys fluid between locations Piping system includes: • Pipe • Fittings (e.g. elbows, reducers, branch connections, etc.) • Flanges, gaskets, bolting • Valves • Pipe supports 2Notes: 4
  7. 7. ASME B31.3 • Provides requirements for: – Design – Erection – Materials – Inspection – Fabrication – Testing • For process plants including – Petroleum refineries – Paper plants – Chemical plants – Semiconductor – Pharmaceutical plants plants – Textile plants – Cryogenic plants 3Notes: Scope of ASME B31.3 • Piping and piping components, all fluid services: – Raw, intermediate, and finished chemicals – Petroleum products – Gas, steam, air, and water – Fluidized solids – Refrigerants – Cryogenic fluids • Interconnections within packaged equipment • Scope exclusions specified 4Notes: 5
  8. 8. Strength • Yield and Tensile Strength • Creep Strength • Fatigue Strength • Alloy Content • Material Grain size • Steel Production Process 5Notes: Stress - Strain Diagram S B A C E 6Notes: 6
  9. 9. Corrosion Resistance • Deterioration of metal by chemical or electrochemical action • Most important factor to consider • Corrosion allowance added thickness • Alloying increases corrosion resistance 7Notes: Piping System Corrosion General or Uniform metal loss. May be combined with erosion if Uniform high-velocity fluids, or moving fluids containing Corrosion abrasives. Pitting Localized metal loss randomly located on material Corrosion surface. Occurs most often in stagnant areas or areas of low-flow velocity. Galvanic Occurs when two dissimilar metals contact each other in Corrosion corrosive electrolytic environment. Anodic metal develops deep pits or grooves as current flows from it to cathodic metal. Crevice Corrosion Localized corrosion similar to pitting. Occurs at places such as gaskets, lap joints, and bolts where crevice exists. Concentration Occurs when different concentration of either a corrosive Cell Corrosion fluid or dissolved oxygen contacts areas of same metal. Usually associated with stagnant fluid. Graphitic Occurs in cast iron exposed to salt water or weak acids. Corrosion Reduces iron in cast iron, and leaves graphite in place. Result is extremely soft material with no metal loss. 8Notes: 7
  10. 10. Material Toughness • Energy necessary to initiate and propagate a crack • Decreases as temperature decreases • Factors affecting fracture toughness include: – Chemical composition or alloying elements – Heat treatment – Grain size 9Notes: Fabricability • Ease of construction • Material must be weldable • Common shapes and forms include: – Seamless pipe – Plate welded pipe – Wrought or forged elbows, tees, reducers, crosses – Forged flanges, couplings, valves – Cast valves 10Notes: 8
  11. 11. Availability and Cost • Consider economics • Compare acceptable options based on: – Availability – Relative cost 11Notes: Pipe Fittings • Produce change in geometry – Modify flow direction – Bring pipes together – Alter pipe diameter – Terminate pipe 12Notes: 9
  12. 12. Elbow and Return 90° 45° 180° Return 13 Figure 4.1Notes: Tee Reducing Outlet Tee Cross Tee Figure 4.2 14Notes: 10
  13. 13. Reducer Concentric Eccentric Figure 4.3 15Notes: Welding Outlet Fitting 16 Figure 4.4Notes: 11
  14. 14. Cap Figure 4.5 17Notes: Lap-joint Stub End Note square corner R R Enlarged Section of Lap 18 Figure 4.6Notes: 12
  15. 15. Typical Flange Assembly Flange Bolting Gasket 19 Figure 4.7Notes: Types of Flange Attachment and Facing Flange Attachment Types Flange Facing Types Threaded Flanges Flat Faced Socket-Welded Flanges Blind Flanges Raised Face Slip-On Flanges Lapped Flanges Ring Joint Weld Neck Flanges 20 Table 4.1Notes: 13
  16. 16. Flange Facing Types 21 Figure 4.8Notes: Gaskets • Resilient material • Inserted between flanges • Compressed by bolts to create seal • Commonly used types – Sheet – Spiral wound – Solid metal ring 22Notes: 14
  17. 17. Flange Rating Class • Based on ASME B16.5 • Acceptable pressure/temperature combinations • Seven classes (150, 300, 400, 600, 900, 1,500, 2,500) • Flange strength increases with class number • Material and design temperature combinations without pressure indicated not acceptable 23Notes: Material Specification List 24 Table 4.2Notes: 15
  18. 18. Pressure - Temperature Ratings Material 1.8 1.9 1.10 Group No. Classes 150 300 400 150 300 400 150 300 400 Temp., °F -20 to 100 235 620 825 290 750 1000 290 750 1000 200 220 570 765 260 750 1000 260 750 1000 300 215 555 745 230 720 965 230 730 970 400 200 555 740 200 695 885 200 705 940 500 170 555 740 170 695 805 170 665 885 600 140 555 740 140 605 785 140 605 805 650 125 555 740 125 590 785 125 590 785 700 110 545 725 110 570 710 110 570 755 750 95 515 685 95 530 675 95 530 710 800 80 510 675 80 510 650 80 510 675 850 65 485 650 65 485 600 65 485 650 900 50 450 600 50 450 425 50 450 600 950 35 320 425 35 320 290 35 375 505 1000 20 215 290 20 215 190 20 260 345 25 Table 4.3Notes: Sample Problem 1 Flange Rating New piping system to be installed at existing plant. Determine required flange class. • Pipe Material: 1 1 Cr − 1 Mo 4 2 • Design Temperature: 700°F • Design Pressure: 500 psig 26Notes: 16
  19. 19. Sample Problem 1 Solution • Determine Material Group Number (Fig. 4.2) Group Number = 1.9 • Find allowable design pressure at intersection of design temperature and Group No. Check Class 150. – Allowable pressure = 110 psig < design pressure – Move to next higher class and repeat steps • For Class 300, allowable pressure = 570 psig • Required flange Class: 300 27Notes: Valves • Functions – Block flow – Throttle flow – Prevent flow reversal 28Notes: 17
  20. 20. Full Port Gate Valve 1. Handwheel Nut 2. Handwheel 3. Stem Nut 4. Yoke 5. Yoke Bolting 6. Stem 7. Gland Flange 8. Gland 9. Gland Bolts or Gland Eye-bolts and nuts 10. Gland Lug Bolts and Nuts 11. Stem Packing 12. Plug 13. Lantern Ring 14. Backseat Bushing 15. Bonnet 16. Bonnet Gasket 17. Bonnet Bolts and Nuts 18. Gate 19. Seat Ring 20. Body 21. One-Piece Gland (Alternate) 22. Valve Port 29 Figure 5.1Notes: Globe Valve • Most economic for throttling flow • Can be hand-controlled • Provides “tight” shutoff • Not suitable for scraping or rodding • Too costly for on/off block operations 30Notes: 18
  21. 21. Check Valve • Prevents flow reversal • Does not completely shut off reverse flow • Available in all sizes, ratings, materials • Valve type selection determined by – Size limitations – Cost – Availability – Service 31Notes: Swing Check Valve Cap Pin Seat Ring Hinge Flow Direction Disc Body 32 Figure 5.2Notes: 19
  22. 22. Ball Check Valve 33 Figure 5.3Notes: Lift Check Valve Seat Ring Piston Flow Direction 34 Figure 5.4Notes: 20
  23. 23. Wafer Check Valve 35 Figure 5.5Notes: Ball Valve No. Part Names 1 Body 2 Body Cap 3 Ball 4 Body Seal Gasket 5 Seat 6 Stem 7 Gland Flange 8 Stem Packing 9 Gland Follower 10 Thrust Bearing 11 Thrust Washer 12 Indicator Stop 13 Snap Ring 14 Gland Bolt 15 Stem Bearing 16 Body Stud Bolt & Nuts 17 Gland Cover 18 Gland Cover Bolts 19 Handle 36 Figure 5.6Notes: 21
  24. 24. Plug Valve Wedge Molded-In Resilient Seal Sealing Slip 37 Figure 5.7Notes: Valve Selection Process General procedure for valve selection. 1. Identify design information including pressure and temperature, valve function, material, etc. 2. Identify potentially appropriate valve types and components based on application and function (i.e., block, throttle, or reverse flow prevention). 38Notes: 22
  25. 25. Valve Selection Process, cont’d 3. Determine valve application requirements (i.e., design or service limitations). 4. Finalize valve selection. Check factors to consider if two or more valves are suitable. 5. Provide full technical description specifying type, material, flange rating, etc. 39Notes: Exercise 1 - Determine Required Flange Rating • Pipe: 1 1 Cr − 1 Mo 4 2 • Flanges: A-182 Gr. F11 • Design Temperature: 900°F • Design Pressure: 375 psig 40Notes: 23
  26. 26. Exercise 1 - Solution 1. Identify material specification of flange A-182 Gr, F11 2. Determine Material Group No. (Table 4.2) Group 1.9 3. Determine class using Table 4.3 with design temperature and Material Group No. – The lowest Class for design pressure of 375 psig is Class 300. – Class 300 has 450 psig maximum pressure at 900°F 41Notes: Design Conditions • General – Normal operating conditions – Design conditions • Design pressure and temperature – Identify connected equipment and associated design conditions – Consider contingent conditions – Consider flow direction – Verify conditions with process engineer 42Notes: 24
  27. 27. Loading Conditions Principal pipe load types • Sustained loads – Act on system all or most of time – Consist of pressure and total weight load • Thermal expansion loads – Caused by thermal displacements – Result from restrained movement • Occasional loads – Act for short portion of operating time 43 – Seismic and/or dynamic loadingNotes: Stresses Produced By Internal Pressure Sl Sc P t Sl = Longitudinal Stress Sc = Circumferential (Hoop) Stress t = Wall Thickness P = Internal Pressure 44 Figure 6.1Notes: 25
  28. 28. Stress Categorization • Primary Stresses – Direct – Shear – Bending • Secondary stresses – Act across pipe wall thickness – Cause local yielding and minor distortions – Not a source of direct failure 45Notes: Stress Categorization, cont’d • Peak stresses – More localized – Rapidly decrease within short distance of origin – Occur where stress concentrations and fatigue failure might occur – Significance equivalent to secondary stresses – Do not cause significant distortion 46Notes: 26
  29. 29. Allowable Stresses Function of – Material properties – Temperature – Safety factors Established to avoid: – General collapse or excessive distortion from sustained loads – Localized fatigue failure from thermal expansion loads – Collapse or distortion from occasional loads 47Notes: B31.3 Allowable Stresses in Tension Basic Allowable Stress S, ksi. At Metal Temperature, °F. ° ° Spec. No/Grade Material 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 Carbon Steel A 106 B 20.0 20.0 20.0 20.0 18.9 17.3 16.5 10.8 6.5 2.5 1.0 C - ½Mo A 335 P1 18.3 18.3 17.5 16.9 16.3 15.7 15.1 13.5 12.7 4. 2.4 1¼ - ½Mo A 335 P11 20.0 18.7 18.0 17.5 17.2 16.7 15.6 15.0 12.8 6.3 2.8 1.2 18Cr - 8Ni pipe A 312 TP304 20.0 20.0 20.0 18.7 17.5 16.4 16.0 15.2 14.6 13.8 9.7 6.0 3.7 2.3 1.4 16Cr - 12Ni-2Mo A 312 TP316 20.0 20.0 20.0 19.3 17.9 17.0 16.3 15.9 15.5 15.3 12.4 7.4 4.1 2.3 1.3 pipe Table 6.1 48Notes: 27
  30. 30. Pipe Thickness Required For Internal Pressure PD t= • 2 (SE + PY ) P = Design pressure, psig D = Pipe outside diameter, in. S = Allowable stress in tension, psi E = Longitudinal-joint quality factor Y = Wall thickness correction factor • t m = t + CA tm • t nom = 0.875 49Notes: Spec. Class (or Type) Description Ej No. Carbon Steel API ... Seamless pipe 1.00 5L ... Electric resistance welded pipe 0.85 ... Electric fusion welded pipe, double butt, straight or 0.95 spiral seam Furnace butt welded A 53 Type S Seamless pipe 1.00 Type E Electric resistance welded pipe 0.85 Type F Furnace butt welded pipe 0.60 A 106 ... Seamless pipe 1.00 Low and Intermediate Alloy Steel A 333 ... Seamless pipe 1.00 ... Electric resistance welded pipe 0.85 A 335 ... Seamless pipe 1.00 Stainless Steel A 312 ... Seamless pipe 1.00 ... Electric fusion welded pipe, double butt seam 0.85 ... Electric fusion welded pipe, single butt seam 0.80 A 358 1, 3, 4 Electric fusion welded pipe, 100% radiographed 1.00 5 Electric fusion welded pipe, spot radiographed 0.90 2 Electric fusion welded pipe, double butt seam 0.85 Nickel and Nickel Alloy B 161 ... Seamless pipe and tube 1.00 B 514 ... Welded pipe 0.80 B 675 All Welded pipe 0.80 50 Table 6.2Notes: 28
  31. 31. Temperature, °F Materials 900 & lower 950 1000 1050 1100 1150 & up Ferritic 0.4 0.5 0.7 0.7 0.7 0.7 Steels Austenitic 0.4 0.4 0.4 0.4 0.5 0.7 Steels Other 0.4 0.4 0.4 0.4 0.4 0.4 Ductile Metals Cast iron 0.0 ... ... ... ... ... Table 6.3 51Notes: Curved and Mitered Pipe • Curved pipe – Elbows or bends – Same thickness as straight pipe • Mitered bend – Straight pipe sections welded together – Often used in large diameter pipe – May require larger thickness • Function of number of welds, conditions, size 52Notes: 29
  32. 32. Sample Problem 2 - Determine Pipe Wall Thickness Design temperature: 650°F Design pressure: 1,380 psig. Pipe outside diameter: 14 in. Material: ASTM A335, Gr. P11 ( 1 14 Cr − 12 Mo ), seamless Corrosion allowance: 0.0625 in. 53Notes: Sample Problem 2 - Solution PD t= 2(SE + PY) 1,380 × 14 t= 2[(16,200 × 1) + (1,380 × 0.4 )] t = 0.577 in. 54Notes: 30
  33. 33. Sample Problem 2 - Solution, cont’d tm = t + c = 0.577 + 0.0625 = 0.6395 in. 0.6395 t nom = = 0.731 in. 0.875 55Notes: Welded Branch Connection Db Tb Nom. Reinforcement Reinforcement tb c Zone Limits Thk. Zone Limits Mill Tol. A3 A3 L4 A4 A4 A1 Tr c th Th Dh d1 Mill A2 A2 Tol. Nom. d2 d2 Thk. β Pipe C 56 Figure 6.2Notes: 31
  34. 34. Reinforcement Area Db − 2(Tb − c) d1 = sin β d1 = Effective length removed from run pipe, in. Db = Branch outside diameter, in. Tb = Minimum branch thickness, in. c = Corrosion allowance, in. β = Acute angle between branch and header 57Notes: Required Reinforcement Area Required reinforcement area, A1: A 1 = t h d1(2 − sin β) Where: th = Minimum required header thickness, in. 58Notes: 32
  35. 35. Reinforcement Pad • Provides additional reinforcement • Usually more economical than increasing wall thickness • Selection variables – Material – Outside diameter – Wall thickness æ (D − Db ) ö A4 = ç p ç sin β Tr è 59Notes: Sample Problem 3 • Pipe material: Seamless, A 106/Gr. B for branch and header, S = 16,500 psi • Design conditions: 550 psig @ 700°F • c = 0.0625 in. • Mill tolerance: 12.5% 60Notes: 33
  36. 36. Sample Problem 3, cont’d • Nominal Pipe Header: 0.562 in. Thicknesses: Branch: 0.375 in. • Required Pipe Header: 0.395 in. Thicknesses: Branch: 0.263 in. • Branch connection at 90° angle 61Notes: Sample Problem 3 - Solution Db − 2(Tb − c) d1 = sin β 16 − 2 (0.375 × 0.875 − 0.0625 ) d1 = = 15.469 in. sin 90° A1 = thd1(2 − sinβ) A1 = 0.395 × 15.469 (2 − sin90°) = 6.11in.2 62Notes: 34
  37. 37. Sample Problem 3 - Solution, cont’d • Calculate excess area available in header, A2. A 2 = (2d2−d1)(Th−th−c ) d2 = d1 = 15.469 in. < Dh = 24 in. A2 = (2 × 15.469 - 15.469) (0.875 × 0.562 - 0.395 - 0.0625) A2 = 0.53 in.2 63Notes: Sample Problem 3 - Solution, cont’d • Calculate excess area available in branch, • A3. 2L 4(Tb − tb−c ) A3 = sinβ L 4 = 2.5 (0.875 × 0.375 − 0.0625 ) = 0.664 in. 2 × 0.664 (0.875 × 0.375 − 0.263 − 0.0625 ) 2 A3 = = 0.003 in. sin 90° 64Notes: 35
  38. 38. Sample Problem 3 - Solution, cont’d • Calculate other excess area available, A4. A4 = 0. • Total Available Area: AT = A2 + A3 + A4 AT = 0.53 + 0.003 + 0 = 0.533 in.2 available reinforcement. AT < A1 ∴ Pad needed 65Notes: Sample Problem 3 - Solution, cont’d • Reinforcement pad: A106, Gr. B, 0.562 in. thick • Recalculate Available Reinforcement L41 = 2.5 (Th - c) = 2.5 (0.875 × 0.562 - 0.0625) = 1.073 in. L42 = 2.5 (Tb - c) + Tr = 2.5 (0.875 × 0.375 - 0.0625) + 0.562 (0.875) = 1.16 in 66Notes: 36
  39. 39. Sample Problem 3 - Solution, cont’d Therefore, L4 = 1.073 in. 2L 4 (Tb − t b − c) A3 = sin β 2 × 1.073 (0.875 × 0.375 − 0.263 − 0.0625 ) A3 = sin90 o A 3 = 0.005 in.2 (vs. the 0.003 in.2 previously calculated ) A T = A 2 + A 3 + A 4 = 0.53 + 0.005 + 0 = 0.535 in.2 67Notes: Sample Problem 3 - Solution, cont’d • Calculate additional reinforcement required and pad dimensions: A4 = 6.11 - 0.535 = 5.575 in.2 Pad diameter, Dp is: Tr = 0.562 (0.875) = 0.492 in. A 4 Db 5.575 Dp = + = + 16 = 27.3 Tr sin β 0.492 Since 2d2 > Dp, pad diameter is acceptable 68Notes: 37
  40. 40. Exercise 2 - Determine Required Pipe Wall Thickness • Design Temperature: 260°F • Design Pressure: 150 psig • Pipe OD: 30 in. • Pipe material: A 106, Gr. B seamless • Corrosion allowance: 0.125 • Mill tolerance: 12.5% • Thickness for internal pressure and nominal thickness? 69Notes: Exercise 2 - Solution • From Tables 6.1, 6.2, and 6.3 obtain values: – S = 20,000 psi – E = 1.0 – Y = 0.4 • Thickness calculation: PD 150 × 30 t= = 2(SE + PY ) 2[(20,000 × 1.0 ) + (150 × 0.04 )] t = 0.112 in. 70Notes: 38
  41. 41. Exercise 2 - Solution, cont’d • Corrosion allowance calculation: t m = t + CA = 0.112 + 0.125 t = 0.237 in. • Mill tolerance calculation: tm 0.237 t nom = = 0.875 0.875 t nom = 0.271 in. 71Notes: Layout Considerations • Operational – Operating and control points easily reached • Maintenance – Ample clearance for maintenance equipment – Room for equipment removal – Sufficient space for access to supports • Safety – Consider personnel safety – Access to fire fighting equipment 72Notes: 39
  42. 42. Pipe Supports and Restraints • Supports – Absorb system weight – Reduce: + longitudinal pipe stress + pipe sag + end point reaction loads • Restraints – Control or direct thermal movement due to: + thermal expansion 73 + imposed loadsNotes: Support and Restraint Selection Factors • Weight load • Available attachment clearance • Availability of structural steel • Direction of loads and/or movement • Design temperature • Vertical thermal movement at supports 74Notes: 40
  43. 43. Rigid Supports Shoe Saddle Base Adjustable Support Dummy Support Trunnion 75 Figure 7.1Notes: Hangers 76 Figure 7.2Notes: 41
  44. 44. Flexible Supports Load and Deflection Small Change in Scale Effective Lever Arm Large Change in Effective Lever Arm Relatively Constant Load Typical Variable-Load Typical Constant-Load Spring Support Spring Support Mechanism 77 Figure 7.3Notes: Restraints • Control, limit, redirect thermal movement – Reduce thermal stress – Reduce loads on equipment connections • Absorb imposed loads – Wind – Earthquake – Slug flow – Water hammer – Flow induced-vibration 78Notes: 42
  45. 45. Restraints, cont’d • Restraint Selection – Direction of pipe movement – Location of restraint point – Magnitude of load 79Notes: Anchors and Guides • Anchor – Full fixation – Permits very limited (if any) translation or rotation • Guide – Permits movement along pipe axis – Prevents lateral movement – May permit pipe rotation 80Notes: 43
  46. 46. Restraints - Anchors Anchor Anchor Partial Anchor 81 Figure 7.4Notes: Restraints - Guides Guide Guide x Guide Vertical Guide 82 Figure 7.5Notes: 44
  47. 47. Piping Flexibility • Inadequate flexibility – Leaky flanges – Fatigue failure – Excessive maintenance – Operations problems – Damaged equipment • System must accommodate thermal movement 83Notes: Flexibility Analysis • Considers layout, support, restraint • Ensures thermal stresses and reaction loads are within allowable limits • Anticipates stresses due to: – Elevated design temperatures + Increases pipe thermal stress and reaction loads + Reduces material strength – Pipe movement 84 – Supports and restraintsNotes: 45
  48. 48. Flexibility Analysis, cont’d • Evaluates loads imposed on equipment • Determines imposed loads on piping system and associated structures • Loads compared to industry standards – Based on tables – Calculated 85Notes: Design Factors • Layout • Pipe diameter, • Component thickness design details • Design temperature • Fluid service and pressure • Connected • End-point movements equipment type • Existing structural • Operating steel locations scenarios • Special design considerations 86Notes: 46
  49. 49. Equipment Nozzle Load Standards and Parameters Parameters Used Equipment Item Industry Standard To Determine Acceptable Loads Centrifugal Pumps API 610 Nozzle size Centrifugal API 617, 1.85 times Nozzle size, material Compressors NEMA SM-23 allowable Air-Cooled Heat API 661 Nozzle size Exchangers Pressure Vessels, Shell- ASME Code Section Nozzle size, thickness, and-Tube Heat VIII, WRC 107, reinforcement details, Exchanger Nozzles WRC 297 vessel/exchanger diameter, and wall thickness. Stress analysis required. Tank Nozzles API 650 Nozzle size, tank diameter, height, shell thickness, nozzle elevation. Steam Turbines NEMA SM-23 Nozzle size 87 Table 7.1Notes: Computer Analysis • Used to perform detailed piping stress analysis • Can perform numerous analyses • Accurately completes unique and difficult functions – Time-history analyses – Seismic and wind motion – Support motion – Finite element analysis 88 – Animation effectsNotes: 47
  50. 50. Computer Analysis Guidelines Maximum Differential Type Of Piping Pipe Size, NPS Flexibility Temp. General piping ≥4 ≥ 400°F ≥8 ≥ 300°F ≥ 12 ≥ 200°F ≥ 20 any For rotating equipment ≥3 Any For air-fin heat exchangers ≥4 Any For tankage ≥ 12 Any 89 Table 7.2Notes: Piping Flexibility Temperature • Analysis based on largest temperature difference imposed by normal and abnormal operating conditions • Results give: – Largest pipe stress range – Largest reaction loads on connections, supports, and restraints • Extent of analysis depends on situation 90Notes: 48
  51. 51. Normal Temperature Conditions To Consider Temperature range expected for most of time plant is Stable in operation. Margin above operating temperature Operation (i.e., use of design temperature rather than operating temperature) allows for process flexibility. Determine if heating or cooling cycles pose flexibility Startup and problems. For example, if tower is heated while Shutdown attached piping remains cold, piping flexibility should be checked. Regeneration Design for normal operation, regeneration, or and Decoking decoking, and switching from one service to the Piping other. An example is furnace decoking. Requires multiple analyses to evaluate expected temperature variations, for no flow in some of piping, Spared and for switching from one piece of equipment to Equipment another. Common example is piping for two or more pumps with one or more spares. 91 Table 7.3Notes: Abnormal Temperature Conditions To Consider Temperature changes due to loss of cooling medium Loss of Cooling flow should be considered. Includes pipe that is Medium Flow normally at ambient temperature but can be blocked in, while subject to solar radiation. Most on-site equipment and lines, and many off-site lines, are freed of gas or air by using steam. For 125 psig steam, 300°F is typically used for metal temperature. Piping connected to equipment which Steamout for Air will be steamed out, especially piping connected to or Gas Freeing upper parts of towers, should be checked for tower at 300°F and piping at ambient plus 50°F. This may govern flexibility of lines connected to towers that operate at less than 300°F or that have a smaller temperature variation from top to bottom. If process flow can be stopped while heat is still being No Process Flow applied, flexibility should be checked for maximum While Heating metal temperature. Such situations can occur with Continues steam tracing and steam jacketing. 92 Table 7.4Notes: 49
  52. 52. Extent of Analysis • Extent depends on situation • Analyze right combination of conditions • Not necessary to include system sections that are irrelevant to analysis results 93Notes: Modifying System Design • Provide more offsets or bends • Use more expansion loops • Install expansion joints • Locate restraints to: – Minimize thermal and friction loads – Redirect thermal expansion • Use spring supports to reduce large vertical thermal loads • Use Teflon bearing pads to reduce friction loads 94Notes: 50
  53. 53. System Design Considerations • Pump systems – Operating vs. spared pumps • Heat traced piping systems – Heat tracing + Reduces liquid viscosity + Prevents condensate accumulation – Tracing on with process off 95Notes: System Design Considerations, cont’d • Atmospheric storage tank – Movement at nozzles – Tank settlement • Friction loads at supports and restraints – Can act as anchors or restraints – May cause high pipe stresses or reaction loads • Air-cooled heat exchangers – Consider header box and bundle movement 96Notes: 51
  54. 54. Tank Nozzle SHELL NOZZLE BOTTOM 97 Figure 7.6Notes: Welding • Welding is primary way of joining pipe • Provides safety and reliability • Qualified welding procedure and welders • Butt welds used for: – Pipe ends – Butt-weld-type flanges or fittings to pipe ends – Edges of formed plate 98Notes: 52
  55. 55. Butt-Welded Joint Designs Equal Thickness (a) Standard End Preparation (b) Standard End Preparation of Pipe of Butt-Welding Fittings and Optional End Preparation of (c) Suggested End Preparation, Pipe 7/8 in. and Thinner Pipe and Fittings Over 7/8 in. Thickness 99 Figure 8.1Notes: Butt-Welded Joint Designs Unequal Thickness 3/32 in. max. (a) (b) (c) (d) 100 Figure 8.2Notes: 53
  56. 56. Fillet Welds 101 Figure 8.3Notes: Weld Preparation • Welder and equipment must be qualified • Internal and external surfaces must be clean and free of paint, oil, rust, scale, etc. • Ends must be: – Suitably shaped for material, wall thickness, welding process – Smooth with no slag from oxygen or arc cutting 102Notes: 54
  57. 57. Preheating • Minimizes detrimental effects of: – High temperature – Severe thermal gradients • Benefits include: – Dries metal and removes surface moisture – Reduces temperature difference between base metal and weld – Helps maintain molten weld pool – Helps drive off absorbed gases 103Notes: Postweld Heat Treatment (PWHT) • Primarily for stress relief – Only reason considered in B31.3 • Averts or relieves detrimental effects – Residual stresses + Shrinkage during cooldown + Bending or forming processes – High temperature – Severe thermal gradients 104Notes: 55
  58. 58. Postweld Heat Treatment (PWHT), cont’d • Other reasons for PWHT to be specified by user – Process considerations – Restore corrosion resistance of normal grades of stainless steel – Prevent caustic embrittlement of carbon steel – Reduce weld hardness 105Notes: Storage and Handling • Store piping on mounds or sleepers • Stacking not too high • Store fittings and valves in shipping crates or on racks • End protectors firmly attached • Lift lined and coated pipes and fittings with fabric or rubber covered slings and padding 106Notes: 56
  59. 59. Pipe Fitup and Tolerances • Good fitup essential – Sound weld – Minimize loads • Dimensional tolerances • Flange tolerances 107Notes: Pipe Alignment Load Sensitive Equipment • Special care and tighter tolerances needed • Piping should start at nozzle flange – Initial section loosely bolted – Gaskets used during fabrication to be replaced • Succeeding pipe sections bolted on • Field welds to join piping located near machine 108Notes: 57
  60. 60. Load Sensitive Equipment, cont’d • Spring supports locked in cold position during installation and adjusted in locked position later • Final bolt tensioning follows initial alignment of nozzle flanges • Final nozzle alignment and component flange boltup should be completed after replacing any sections removed 109Notes: Load Sensitive Equipment, cont’d • More stringent limits for piping > NPS 3 • Prevent ingress of debris during construction 110Notes: 58
  61. 61. Flange Joint Assembly • Primary factors – Selection – Design – Preparation – Inspection – Installation • Identify and control causes of leakage 111Notes: Flange Preparation, Inspection, and Installation • Redo damaged surfaces • Clean faces • Align flanges • Lubricate threads and nuts • Place gasket properly • Use proper flange boltup procedure 112Notes: 59
  62. 62. “Criss-Cross” Bolt-tightening Sequence 113 Figure 8.4Notes: Causes of Flange Leakage • Uneven bolt stress • Improper flange alignment • Improper gasket centering • Dirty or damaged flange faces • Excessive loads at flange locations • Thermal shock • Improper gasket size or material • Improper flange facing 114Notes: 60
  63. 63. Inspection • Defect identification • Weld inspection – Technique – Weld type – Anticipated type of defect – Location of weld – Pipe material 115Notes: Typical Weld Imperfections Lack of Fusion Between Weld Bead and Base Metal a) Side Wall Lack of Fusion b) Lack of Fusion Between Adjacent Passes Incomplete Filling at Root on One Side Only Incomplete Filling at Root c) Incomplete Penetration Due d) Incomplete Penetration of to Internal Misalignment Weld Groove External Undercut Root Bead Fused to Both Inside Internal Undercut Surfaces but Center of Root Slightly Below Inside Surface of Pipe (Not Incomplete Penetration) e) Concave Root Surface f) Undercut (Suck-Up) g) Excess External Reinforcement 116 Figure 9.1Notes: 61
  64. 64. Weld Inspection Guidelines Type of Inspection Situation/Weld Type Defect Visual All welds. • Minor structural welds. • Cracks. • Slag inclusions. Radiography • Butt welds. • Gas pockets. • Girth welds. • Slag inclusions. • Miter groove welds. • Incomplete penetration. Magnetic Particle • Ferromagnetic • Cracks. materials. • Porosity. • For flaws up to 6 mm (1/4 in.) beneath the • Lack of fusion. surface. Liquid Penetrant • Ferrous and • Cracks. nonferrous materials. • Seams. • Intermediate weld passes. • Porosity. Weld root pass. • Folds. • Simple and • Inclusions. • inexpensive. Shrinkage. • • Surface defects. Ultrasonic Confirms high weld • Laminations. quality in pressure- Slag inclusions in thick containing joints. • plates. • Subsurface flaws. 117 Table 9.1Notes: Testing • Pressure test system to demonstrate integrity • Hydrostatic test unless pneumatic approved for special cases • Hydrostatic test pressure – ≥ 1½ times design pressure 118Notes: 62
  65. 65. Testing, cont’d – For design temperature > test temperature: 1. 5 P S T PT = S ST/S must be ≤ 6.5 PT = Minimum hydrostatic test pressure, psig P = Internal design pressure, psig ST = Allowable stress at test temperature, psi S = Allowable stress at design temperature, psi 119Notes: Testing, cont’d • Pneumatic test at 1.1P • Instrument take-off piping and sampling piping strength tested with connected equipment 120Notes: 63
  66. 66. Nonmetallic Piping • Thermoplastic Piping – Can be repeatedly softened and hardened by increasing and decreasing temperature • Reinforced Thermosetting Resin Piping (RTR) – Fabricated from resin which can be treated to become infusible or insoluble 121Notes: Nonmetallic Piping, cont’d • No allowances for pressure or temperature variations above design conditions • Most severe coincident pressure and temperature conditions determine design conditions 122Notes: 64
  67. 67. Nonmetallic Piping, cont’d • Designed to prevent movement from causing: – Failure at supports – Leakage at joints – Detrimental stresses or distortions • Stress-strain relationship inapplicable 123Notes: Nonmetallic Piping, cont’d • Flexibility and support requirement same as for piping in normal fluid service. In addition: – Piping must be supported, guided, anchored to prevent damage. – Point loads and narrow contact areas avoided – Padding placed between piping and supports – Valves and load transmitting equipment supported independently to prevent excessive loads. 124Notes: 65
  68. 68. Nonmetallic Piping, cont’d • Thermoplastics not used in flammable service, and safeguarded in most fluid services. • Joined by bonding 125Notes: Category M Fluid Service Category M Fluid • Significant potential for personnel exposure • Single exposure to small quantity can cause irreversible harm to breathing or skin. 126Notes: 66
  69. 69. Category M Fluid Service, cont’d • Requirements same as for piping in normal fluid service. In addition: – Design, layout, and operation conducted with minimal impact and shock loads. – Detrimental vibration, pulsation, resonance effects to be avoided or minimized. – No pressure-temperature variation allowances. 127Notes:Category M Fluid Service, cont’d – Most severe coincident pressure-temperature conditions determine design temperature and pressure. – All fabrication and joints visually examined. – Sensitive leak test required in addition to other required testing. 128Notes: 67
  70. 70. Category M Fluid Service, cont’d • Following may not be used – Miter bends not designated as fittings, fabricated laps, nonmetallic fabricated branch connections. – Nonmetallic valves and specialty components. – Threaded nonmetallic flanges. – Expanded, threaded, caulked joints. 129Notes: High Pressure Piping • Ambient effects on design conditions – Pressure reduction based on cooling of gas or vapor – Increased pressure due to heating of a static fluid – Moisture condensation 130Notes: 68
  71. 71. High Pressure Piping, cont’d • Other considerations – Dynamic effects – Weight effects – Thermal expansion and contraction effects – Support, anchor, and terminal movement 131Notes: High Pressure Piping, cont’d • Testing – Each system hydrostatically or pneumatically leak tested – Each weld and piping component tested – Post installation pressure test at 110% of design pressure if pre-installation test was performed • Examination – Generally more extensive than normal fluid 132 serviceNotes: 69
  72. 72. Summary • Process plant piping much more than just pipe • ASME B31.3 covers process plant piping • Covers design, materials, fabrication, erection, inspection, and testing • Course provided overview of requirements 133Notes: 70
  73. 73. Part 2:Background Material 71
  74. 74. OVERVIEW OF PROCESS PLANT PIPING SYSTEM DESIGN Carmagen Engineering, Inc. 72
  75. 75. I. INTRODUCTIONThis course provides an overview of process plant piping system design. Itdiscusses requirements contained in ASME B31.3, Process Piping, plusadditional requirements and guidelines based on common industry practice. Theinformation contained in this course is readily applicable to on-the-jobapplications, and prepares participants to take more extensive courses ifappropriate.II. GENERAL A. What is a piping system A piping system conveys fluid from one location to another. Within a process plant, the locations are typically one or more equipment items (e.g., pumps, pressure vessels, heat exchangers, process heaters, etc.), or individual process plants that are within the boundary of a process facility. A piping system consists of: • Pipe sections • Fittings (e.g., elbows, reducers, branch connections, etc.) • Flanges, gaskets, and bolting • Valves • Pipe supports and restraints Each individual component plus the overall system must be designed for the specified design conditions. B. Scope of ASME B31.3 ASME B31.3 specifies the design, materials, fabrication, erection, inspection, and testing requirements for process plant piping systems. Process plants include petroleum refineries; chemical, pharmaceutical, textile, paper, semiconductor, and cryogenic plants; and related process plants and terminals. 73
  76. 76. ASME B31.3 applies to piping and piping components that are usedfor all fluid services, not just hydrocarbon services. These includethe following:• Raw, intermediate, and finished chemicals.• Petroleum products.• Gas, steam, air, and water.• Fluidized solids.• Refrigerants.• Cryogenic fluids.The scope also includes piping that interconnects pieces or stageswithin a packaged-equipment assembly.The following are excluded from the scope of ASME B31.3:• Piping systems for internal gauge pressures at or above zero but less than 15 psi, provided that the fluid is nonflammable, nontoxic, and not damaging to human tissue, and its design temperature is from -20°F through 366°F.• Power boilers that are designed in accordance with the ASME Boiler and Pressure Vessel Code Section I and external boiler piping that must conform to ASME B31.1.• Tubes, tube headers, crossovers, and manifolds that are located inside a fired heater enclosure.• Pressure vessels, heat exchangers, pumps, compressors, and other fluid-handling or processing equipment. This includes both internal piping and connections for external piping. 74
  77. 77. III. MATERIAL SELECTION CONSIDERATIONSPiping system material selection considerations are discussed below. A. Strength A materials strength is defined by its yield, tensile, creep, and fatigue strengths. Alloy content, material grain size, and the steel production process are factors that affect material strength. 1.0 Yield and Tensile Strength A stress-strain diagram that is produced from a standard tensile test (Figure 3.1) illustrates the yield and tensile strengths. As the stress in a material increases, its deformation also increases. The yield strength is the stress that is required to produce permanent deformation in the material (Point A in Figure 3.1). If the stress is further increased, the permanent deformation continues to increase until the material fails. The maximum stress that the material attains is the tensile strength (Point B in Figure 3.1). If a large amount of strain occurs in going from Point A to Point C, the rupture point, the material is said to be ductile. Steel is an example of a ductile material. If the strain in going from Point A to Point C is small, the material is brittle. Gray cast iron is an example of a brittle material. S B A C E Typical Stress-Strain Diagram for Steel Figure 3.1 75
  78. 78. 2.0 Creep Strength Below about 750°F for a given stress, the strain in most materials remains constant with time. Above this temperature, even with constant stress, the strain in the material will increase with time. This behavior is known as creep. The creep strength, like the yield and tensile strengths, varies with temperature. For a particular temperature, the creep strength of a material is the minimum stress that will rupture the material during a specified period of time. The temperature at which creep strength begins to be a factor is a function of material chemistry. For alloy materials (i.e., not carbon steel) creep strength becomes a consideration at temperatures higher than 750°F.3.0 Fatigue Strength The term “fatigue” refers to the situation where a specimen breaks under a load that it has previously withstood for a length of time, or breaks during a load cycle that it has previously withstood several times. The first type of fatigue is called “static,” and the second type is called “cyclic.” Examples of static fatigue are: creep fracture and stress corrosion cracking. Static fatigue will not be discussed further in this course. One analogy to cyclic fatigue is the bending of a paper clip. The initial bending beyond a certain point causes the paper clip to yield (i.e., permanently deform) but not break. The clip could be bent back and forth several more times and still not break. However after a sufficient number of bending (i.e., load) cycles, the paper clip will break under this repetitive loading. Purely elastic deformation (i.e., without yielding) cannot cause a cyclic fatigue failure. The fatigue strength of a material under cyclic loading can then be defined as the ability to withstand repetitive loading without failure. The number of cycles to failure of a material decreases as the stress resulting from the applied load increases. 76
  79. 79. B. Corrosion Resistance Corrosion of materials involves deterioration of the metal by chemical or electrochemical attack. Corrosion resistance is usually the single most important factor that influences pipe material selection. Table 3.1 summarizes the typical types of piping system corrosion.General or Uniform Characterized by uniform metal loss over entire surface of material. Corrosion May be combined with erosion if material is exposed to high-velocity fluids, or moving fluids that contain abrasive materials. Pitting Form of localized metal loss randomly located on material surface. Corrosion Occurs most often in stagnant areas or areas of low-flow velocity.Galvanic Corrosion Occurs when two dissimilar metals contact each other in corrosive electrolytic environment. The anodic metal develops deep pits or grooves as a current flows from it to the cathodic metal.Crevice Corrosion Localized corrosion similar to pitting. Occurs at places such as gaskets, lap joints, and bolts, where a crevice can exist.Concentration Cell Occurs when different concentration of either corrosive fluid or Corrosion dissolved oxygen contacts areas of same metal. Usually associated with stagnant fluid.Graphitic Corrosion Occurs in cast iron exposed to salt water or weak acids. Reduces iron in the cast iron and leaves the graphite in place. Result is extremely soft material with no metal loss. Typical Types of Piping System Corrosion Table 3.1 For process plant piping systems in corrosive service, corrosion protection is usually achieved by using alloys that resist corrosion. The most common alloys used for this purpose are chromium and nickel. Low-alloy steels with a chromium content of 1¼% to 9% and stainless steels are used in corrosive environments. C. Material Fracture Toughness One way to characterize the fracture behavior of a material is the amount of energy necessary to initiate and propagate a crack at a given temperature. This is the materials fracture toughness, which 77
  80. 80. decreases as the temperature decreases. Tough materials require a relatively large amount of energy to initiate and propagate a crack. The impact energy required to fracture a material sample at a given temperature can be measured by standard Charpy V-notch tests. Various factors other than temperature affect the fracture toughness of a material. These include the following: • Chemical composition or alloying elements. • Heat treatment. • Grain size. The major chemical elements that affect a materials fracture toughness are carbon, manganese, nickel, oxygen, sulfur, and molybdenum. High carbon content, or excessive amounts of oxygen, sulfur, or molybdenum, hurts fracture toughness. The addition of manganese or nickel improves fracture toughness.D. Fabricability A material must be available in the shapes or forms that are required, and it typically must be weldable. In piping systems, some common shapes and forms include the following: • Seamless pipe. • Plate that is used for welded pipe. • Wrought or forged elbows, tees, reducers, and crosses. • Forged flanges, couplings, and valves. • Cast valves.E. Availability and Cost The last factors that affect piping material selection are availability and cost. Where there is more than one technically acceptable material, the final selection must consider what is readily available and what are the relative costs of the acceptable options. For example, the use of carbon steel with a large corrosion allowance could be more expensive than using a low-alloy material with a smaller corrosion allowance. 78
  81. 81. IV. PIPING COMPONENTS A. Fittings, Flanges, and Gaskets 1.0 Pipe Fittings Fittings are used to make some change in the geometry of a piping system. This change could include: • Modifying the flow direction. • Bringing two or more pipes together. • Altering the pipe diameter. • Terminating a pipe. The most common types of fittings are elbows, tees, reducers, welding outlets, pipe caps, and lap joint stub ends. These are illustrated in Figures 4.1 through 4.6. Fittings may be attached to pipe by threading, socket welding, or butt welding. An elbow or return (Figure 4.1) changes the direction of a pipe run. Standard elbows change the direction by either 45° or 90°. Returns change the direction by 180°. 90° 45° 180° Return Elbow and Return Figure 4.1 79
  82. 82. A tee (Figure 4.2) provides for the intersection of threesections of pipe.• A straight tee has equal diameters for both the run and branch pipe connections.• A reducing-outlet tee has a branch diameter which is smaller in size than the run diameter.• A cross permits the intersection of four sections of pipe and is rarely seen in process plants. Tee Figure 4.2A reducer (illustrated in Figure 4.3) changes the diameter ina straight section of pipe. The centerlines of the large andsmall diameter ends coincide in a concentric reducer,whereas they are offset in an eccentric type. Concentric Eccentric Reducer Figure 4.3A welding outlet fitting, or integrally reinforced branchconnection (Figure 4.4) has all the reinforcement required tostrengthen the opening contained within the fitting itself. 80
  83. 83. Typical Integrally Reinforced Branch Connection Figure 4.4 A pipe cap (Figure 4.5) closes off the end of a pipe section. The wall thickness of a butt-welded pipe cap will typically be identical to that of the adjacent pipe section. Cap Figure 4.5 A lap-joint stub end (Figure 4.6) is used in conjunction with lap-joint flanges. Note square corner R R Enlarged Section of Lap Lap-Joint Stub End Figure 4.6 81
  84. 84. 2.0 Flanges A flange connects a pipe section to a piece of equipment, valve, or another pipe such that relatively simple disassembly is possible. Disassembly may be required for maintenance, inspection, or operational reasons. Figure 4.7 shows a typical flange assembly. Flanges are normally used for pipe sizes above NPS 1½. Flange Bolting Gasket Typical Flange Assembly Figure 4.7 A flange type is specified by stating the type of attachment and the type of face. The type of attachment defines how the flange is connected to a pipe section or piece of 82
  85. 85. equipment (e.g., welded). The type of flange face or facing defines the geometry of the flange surface that contacts the gasket. Table 4.1 summarizes the types of flange attachments and faces. Figure 4.8 illustrates flange facing types.Flange Attachment Types Flange Facing Types Threaded Flanges Flat Faced Socket-Welded Flanges Blind Flanges Raised Face Slip-On Flanges Lapped Flanges Ring Joint Weld Neck Flanges Types of Flange Attachment and Facing Table 4.1 83
  86. 86. Flange Facing Types Figure 4.8 84
  87. 87. 3.0 Gaskets A gasket is a resilient material that is inserted between the flanges and seated against the portion of the flanges called the “face” or “facing”. The gasket provides the seal between the fluid in the pipe and the outside, and thus prevents leakage. Bolts compress the gasket to achieve the seal and hold the flanges together against pressure and other loadings. The three gasket types typically used in pipe flanges for process plant applications are: • Sheet. • Spiral wound. • Solid metal ring.B. Flange Rating ASME B16.5, Pipe Flanges and Flanged Fittings, provides steel flange dimensional details for standard pipe sizes through NPS 24. Specification of an ASME B16.5 flange involves selection of the correct material and flange "Class." The paragraphs that follow discuss the flange class specification process in general terms. Flange material specifications are listed in Table 1A in ASME B16.5 (excerpted in Table 4.2). The material specifications are grouped within Material Group Numbers. For example, if the piping is fabricated from carbon steel, the ASTM A105 material specification is often used. ASTM A105 material is in Material Group No. 1.1. Refer to ASME B16.5 for additional acceptable material specifications and corresponding Material Group Numbers. 85
  88. 88. ASME B16.5, Table 1A, Material Specification List (Excerpt) Table 4.2 After the Material Group has been determined, the next step is to select the appropriate Class. The Class is determined by using pressure/temperature rating tables, the Material Group, design metal temperature, and design pressure. Selecting the Class sets all the detailed dimensions for flanges and flanged fittings. The objective is to select the lowest Class that is appropriate for the specified design conditions. Table 2 of ASME B16.5 provides the information that is necessary to select the appropriate flange Class for the specified design conditions. ASME B16.5 has seven classes: Class 150, 300, 400, 600, 900, 1,500, and 2,500. Each Class specifies the design pressure and temperature combinations that are acceptable for a flange with that designation. As the number of the Class increases, the strength of the flange increases for a given Material Group. A higher flange Class can withstand higher pressure and temperature combinations. Table 4.3 is an excerpt from Table 2 of ASME B16.5 and shows some of the temperature and pressure ratings for several Material Groups. Material and design temperature combinations that do not have a pressure indicated are not acceptable. Specifying the flange size, material, and class completes most of what is necessary for selecting an ASME B16.5 flange. The flange type, facing, bolting material, and gasket type and material must be 86
  89. 89. added to complete the flange selection process. Discussion of these other factors is beyond the scope of this course.Material Group 1.8 1.9 1.10 No. Classes 150 300 400 150 300 400 150 300 400 Temp., °F -20 to 100 235 620 825 290 750 1000 290 750 1000 200 220 570 765 260 750 1000 260 750 1000 300 215 555 745 230 720 965 230 730 970 400 200 555 740 200 695 885 200 705 940 500 170 555 740 170 695 805 170 665 885 600 140 555 740 140 605 785 140 605 805 650 125 555 740 125 590 785 125 590 785 700 110 545 725 110 570 710 110 570 755 750 95 515 685 95 530 675 95 530 710 800 80 510 675 80 510 650 80 510 675 850 65 485 650 65 485 600 65 485 650 900 50 450 600 50 450 425 50 450 600 950 35 320 425 35 320 290 35 375 505 1000 20 215 290 20 215 190 20 260 345 ASME B16.5, Pressure-Temperature Ratings (Excerpt) Table 4.3 87
  90. 90. SAMPLE PROBLEM 1 - DETERMINE FLANGE RATINGA new piping system will be installed at an existing plant. It is necessary todetermine the ASME class that is required for the flanges. The following designinformation is provided:• Pipe Material: 1¼ Cr – ½ Mo.• Design Temperature: 700°F.• Design Pressure: 500 psig.SOLUTIONDetermine the Material Group Number for the flanges by referring to ASME Table1A (excerpted in Table 4.2). Find the 1¼ Cr – ½ Mo material in the NominalDesignation Steel column. The material specification for forged flanges would beA182 Gr. F11, and the corresponding material Group Number is 1.9.Refer to Table 2 for Class 150 (excerpted in Table 4.3). Read the allowabledesign pressure at the intersection of the 700°F design temperature and MaterialGroup 1.9. This is only 110 psig and is not enough for this service.Now check Class 300 and do the same thing. The allowable pressure in thiscase is 570 psig, which is acceptable.The required flange Class is 300. 88
  91. 91. V. VALVES A. Valve Functions The possible valve functions must be known before being able to select the appropriate valve type for a particular application. Fluid flows through a pipe, and valves are used to control the flow. A valve may be used to block flow, throttle flow, or prevent flow reversal. 1.0 Blocking Flow The block-flow function provides completely on or completely off flow control of a fluid, generally without throttling or variable control capability. It might be necessary to block flow to take equipment out of service for maintenance while the rest of the unit remains in operation, or to separate two portions of a single system to accommodate various operating scenarios. 2.0 Throttling Flow Throttling may increase or decrease the amount of fluid flowing in the system and can also help control pressure within the system. It might be necessary to throttle flow to regulate the filling rate of a pressure vessel, or to control unit operating pressure levels. 3.0 Preventing Flow Reversal It might be necessary to automatically prevent fluid from reversing its direction during sudden pressure changes or system upsets. Preventing reverse flow might be necessary to avoid damage to a pump or a compressor, or to automatically prevent backflow into the upstream part of the system due to process reasons. 89

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