1. Overview of Process Plant
Piping System Design
Participant’s Guide

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3. Overview of Process Plant
Piping System Design
By:
Vincent A. Carucci
Carmagen Engineering, Inc.
Copyright © 2000 by
All Rights Reserved

4. TABLE OF CONTENTS
PART 1: PARTICIPANT NOTES ..............................................................................3
PART 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. Part 1:
Participant Notes
3

6. OVERVIEW OF
PROCESS PLANT PIPING
SYSTEM DESIGN
By: Vincent A. Carucci
Carmagen Engineering, Inc.
1
Notes:
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
2
Notes:
4

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
3
Notes:
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
4
Notes:
5

8. Strength
• Yield and Tensile Strength
• Creep Strength
• Fatigue Strength
• Alloy Content
• Material Grain size
• Steel Production Process
5
Notes:
Stress - Strain Diagram
S B
A C
E
6
Notes:
6

9. Corrosion Resistance
• Deterioration of metal by chemical or
electrochemical action
• Most important factor to consider
• Corrosion allowance added thickness
• Alloying increases corrosion resistance
7
Notes:
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.
8
Notes:
7

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
9
Notes:
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
10
Notes:
8

11. Availability and Cost
• Consider economics
• Compare acceptable options based on:
– Availability
– Relative cost
11
Notes:
Pipe Fittings
• Produce change in geometry
– Modify flow direction
– Bring pipes together
– Alter pipe diameter
– Terminate pipe
12
Notes:
9

12. Elbow and Return
90° 45°
180° Return
13
Figure 4.1
Notes:
Tee
Reducing Outlet Tee Cross Tee
Figure 4.2
14
Notes:
10

13. Reducer
Concentric Eccentric
Figure 4.3
15
Notes:
Welding Outlet Fitting
16
Figure 4.4
Notes:
11

14. Cap
Figure 4.5
17
Notes:
Lap-joint Stub End
Note square corner
R
R
Enlarged Section
of Lap
18
Figure 4.6
Notes:
12

15. Typical Flange Assembly
Flange
Bolting
Gasket
19
Figure 4.7
Notes:
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 4.1
Notes:
13

16. Flange Facing Types
21
Figure 4.8
Notes:
Gaskets
• Resilient material
• Inserted between flanges
• Compressed by bolts to create seal
• Commonly used types
– Sheet
– Spiral wound
– Solid metal ring
22
Notes:
14

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
23
Notes:
Material Specification List
24
Table 4.2
Notes:
15

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 4.3
Notes:
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
26
Notes:
16

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
27
Notes:
Valves
• Functions
– Block flow
– Throttle flow
– Prevent flow reversal
28
Notes:
17

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 5.1
Notes:
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
30
Notes:
18

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
31
Notes:
Swing Check Valve
Cap
Pin
Seat
Ring
Hinge
Flow
Direction
Disc
Body
32
Figure 5.2
Notes:
19

22. Ball Check Valve
33
Figure 5.3
Notes:
Lift Check Valve
Seat
Ring
Piston
Flow
Direction
34
Figure 5.4
Notes:
20

23. Wafer Check Valve
35
Figure 5.5
Notes:
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 5.6
Notes:
21

24. Plug Valve
Wedge
Molded-In Resilient Seal
Sealing Slip
37
Figure 5.7
Notes:
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).
38
Notes:
22

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.
39
Notes:
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
40
Notes:
23

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
41
Notes:
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
42
Notes:
24

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 loading
Notes:
Stresses Produced By
Internal Pressure
Sl
Sc
P
t
Sl = Longitudinal Stress
Sc = Circumferential (Hoop) Stress
t = Wall Thickness
P = Internal Pressure
44
Figure 6.1
Notes:
25

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
45
Notes:
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
46
Notes:
26

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
47
Notes:
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
48
Notes:
27

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
49
Notes:
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 6.2
Notes:
28

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
51
Notes:
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
52
Notes:
29

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.
53
Notes:
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.
54
Notes:
30

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
55
Notes:
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 6.2
Notes:
31

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
57
Notes:
Required Reinforcement Area
Required reinforcement area, A1:
A 1 = t h d1(2 − sin β)
Where: th = Minimum required header
thickness, in.
58
Notes:
32

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
59
Notes:
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%
60
Notes:
33

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
61
Notes:
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
62
Notes:
34

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
63
Notes:
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°
64
Notes:
35

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
65
Notes:
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
66
Notes:
36

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
67
Notes:
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
68
Notes:
37

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?
69
Notes:
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.
70
Notes:
38

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.
71
Notes:
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
72
Notes:
39

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 loads
Notes:
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
74
Notes:
40

43. Rigid Supports
Shoe Saddle Base Adjustable
Support
Dummy Support Trunnion
75
Figure 7.1
Notes:
Hangers
76
Figure 7.2
Notes:
41

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 7.3
Notes:
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
78
Notes:
42

45. Restraints, cont’d
• Restraint Selection
– Direction of pipe movement
– Location of restraint point
– Magnitude of load
79
Notes:
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
80
Notes:
43

46. Restraints - Anchors
Anchor Anchor Partial Anchor
81
Figure 7.4
Notes:
Restraints - Guides
Guide Guide
x
Guide
Vertical Guide
82
Figure 7.5
Notes:
44

47. Piping Flexibility
• Inadequate flexibility
– Leaky flanges
– Fatigue failure
– Excessive maintenance
– Operations problems
– Damaged equipment
• System must accommodate thermal
movement
83
Notes:
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 restraints
Notes:
45

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
85
Notes:
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
86
Notes:
46

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 7.1
Notes:
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 effects
Notes:
47

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 7.2
Notes:
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
90
Notes:
48

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 7.3
Notes:
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 7.4
Notes:
49

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
93
Notes:
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
94
Notes:
50

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
95
Notes:
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
96
Notes:
51

54. Tank Nozzle
SHELL
NOZZLE
BOTTOM
97
Figure 7.6
Notes:
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
98
Notes:
52

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 8.1
Notes:
Butt-Welded Joint Designs
Unequal Thickness
3/32 in. max.
(a) (b) (c)
(d)
100
Figure 8.2
Notes:
53

56. Fillet Welds
101
Figure 8.3
Notes:
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
102
Notes:
54

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
103
Notes:
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
104
Notes:
55

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
105
Notes:
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
106
Notes:
56

59. Pipe Fitup and Tolerances
• Good fitup essential
– Sound weld
– Minimize loads
• Dimensional tolerances
• Flange tolerances
107
Notes:
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
108
Notes:
57

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
109
Notes:
Load Sensitive Equipment,
cont’d
• More stringent limits for piping > NPS 3
• Prevent ingress of debris during
construction
110
Notes:
58

61. Flange Joint Assembly
• Primary factors
– Selection
– Design
– Preparation
– Inspection
– Installation
• Identify and control causes of leakage
111
Notes:
Flange Preparation,
Inspection, and Installation
• Redo damaged surfaces
• Clean faces
• Align flanges
• Lubricate threads and nuts
• Place gasket properly
• Use proper flange boltup procedure
112
Notes:
59

62. “Criss-Cross”
Bolt-tightening Sequence
113
Figure 8.4
Notes:
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
114
Notes:
60

63. Inspection
• Defect identification
• Weld inspection
– Technique
– Weld type
– Anticipated type of defect
– Location of weld
– Pipe material
115
Notes:
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 9.1
Notes:
61

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 9.1
Notes:
Testing
• Pressure test system to demonstrate
integrity
• Hydrostatic test unless pneumatic
approved for special cases
• Hydrostatic test pressure
– ≥ 1½ times design pressure
118
Notes:
62

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
119
Notes:
Testing, cont’d
• Pneumatic test at 1.1P
• Instrument take-off piping and sampling
piping strength tested with connected
equipment
120
Notes:
63

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
121
Notes:
Nonmetallic Piping, cont’d
• No allowances for pressure or temperature
variations above design conditions
• Most severe coincident pressure and
temperature conditions determine design
conditions
122
Notes:
64

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
123
Notes:
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.
124
Notes:
65

68. Nonmetallic Piping, cont’d
• Thermoplastics not used in flammable
service, and safeguarded in most fluid
services.
• Joined by bonding
125
Notes:
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.
126
Notes:
66

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.
127
Notes:
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.
128
Notes:
67

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.
129
Notes:
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
130
Notes:
68

71. High Pressure Piping,
cont’d
• Other considerations
– Dynamic effects
– Weight effects
– Thermal expansion and contraction effects
– Support, anchor, and terminal movement
131
Notes:
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
service
Notes:
69

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
133
Notes:
70

73. Part 2:
Background Material
71

74. OVERVIEW OF PROCESS PLANT PIPING SYSTEM DESIGN
Carmagen Engineering, Inc.
72

75. I. INTRODUCTION
This course provides an overview of process plant piping system design. It
discusses requirements contained in ASME B31.3, Process Piping, plus
additional requirements and guidelines based on common industry practice. The
information contained in this course is readily applicable to on-the-job
applications, and prepares participants to take more extensive courses if
appropriate.
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. ASME B31.3 applies to piping and piping components that are used
for all fluid services, not just hydrocarbon services. These include
the 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 stages
within 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. III. MATERIAL SELECTION CONSIDERATIONS
Piping system material selection considerations are discussed below.
A. Strength
A material's 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. 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. 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 material's fracture toughness, which
77

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 material's 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. 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. A tee (Figure 4.2) provides for the intersection of three
sections 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 4.2
A reducer (illustrated in Figure 4.3) changes the diameter in
a straight section of pipe. The centerlines of the large and
small diameter ends coincide in a concentric reducer,
whereas they are offset in an eccentric type.
Concentric Eccentric
Reducer
Figure 4.3
A welding outlet fitting, or integrally reinforced branch
connection (Figure 4.4) has all the reinforcement required to
strengthen the opening contained within the fitting itself.
80

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. 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. 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. Flange Facing Types
Figure 4.8
84

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. 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. 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. SAMPLE PROBLEM 1 - DETERMINE FLANGE RATING
A new piping system will be installed at an existing plant. It is necessary to
determine the ASME class that is required for the flanges. The following design
information is provided:
• Pipe Material: 1¼ Cr – ½ Mo.
• Design Temperature: 700°F.
• Design Pressure: 500 psig.
SOLUTION
Determine the Material Group Number for the flanges by referring to ASME Table
1A (excerpted in Table 4.2). Find the 1¼ Cr – ½ Mo material in the Nominal
Designation Steel column. The material specification for forged flanges would be
A182 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 allowable
design pressure at the intersection of the 700°F design temperature and Material
Group 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 this
case is 570 psig, which is acceptable.
The required flange Class is 300.
88

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

92. B. Primary Valve Types
1.0 Gate Valve
Most valves in process plants function as block valves.
About 75% of all valves in process plants are gate valves.
The gate valve is an optimum engineering and economic
choice for on or off service. The gate valve is not suitable to
throttle flow because it will pass the maximum possible flow
while it is only partially open. Figure 5.1 illustrates a typical
full-port gate valve.
90

93. 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
Full-Port Gate Valve
Figure 5.1
2.0 Globe Valve
The globe valve is the type most commonly used to throttle
flow in a process plant. In the smaller sizes, they are
91

94. typically used as hand-control valves. In larger sizes,
applications are limited primarily to bypasses at control valve
stations. They provide relatively tight shutoff in control valve
bypasses during normal operations; they serve as temporary
flow controllers when control valves must be taken out of
service.
Because all globe valve patterns involve a change in flow
direction, they are not suitable for piping systems that
require scraping or rodding. Globe valves are rarely used for
strictly on/off block valve operations because conventional
gate valves adequately serve that function at a lower cost
and a much lower pressure drop.
3.0 Check Valve
Check valves prevent flow reversal. Typical check valve
applications are in pump and compressor discharge piping
and other systems that require protection against backflow.
Valves which contain a disc or discs that swing out of the
flow passage area usually create a lower pressure drop in
the system than those which contain a ball or piston
element. These latter elements remain in the flowstream
and the port configurations frequently include an angular
change in flow direction. For all process designs, the
intended purpose of check valves is to prevent gross flow
reversal, not to effect complete leakage-free, pressure-tight
shutoff of reverse flow.
The selection of a particular check valve type generally
depends on size, cost, availability, and service. Ball and lift
check valves are usually the choice for sizes NPS 2 and
smaller, while swing check and plate check valves are used
in the larger sizes.
3.1 Swing Check Valve
The main components of a swing check valve (Figure
5.2) are the body, disc, cap, seat ring, disc hinge, and
pin. The disc is hinged at the top and closes against
a seat in the valve body opening. It swings freely in
an arc from the fully closed position to one that
provides unobstructed flow. The valve is kept open
by the flow, and disc seating is accomplished by
gravity and/or flow reversal.
92