1. CM4120 Unit Operations Lab Piping Systems
Piping Systems in the Chemical Process Industries
March, 2008
Introduction
Basis for Design
Piping Codes and Standards
Design of Process Piping Systems
Joints and Fittings
Valves

2. CM4120 Unit Operations Lab Piping Systems
Piping Systems include:
Pipe
Flanges
Fittings
Bolting
Gaskets
Valves
Hangers and supports
Insulations, coverings, coatings
Everything between equipment and instrumentation is considered piping

3. CM4120 Unit Operations Lab Piping Systems
“Piping systems are like arteries and veins. They carry the lifeblood of modern civilization.”
Mohinder Nayyar, P.E.
Piping Handbook, 7th ed.
McGraw-Hill, 2000
The invention of piping systems is what allowed civilization to develop beyond small villages.
Early records show use of hollow log piping and open-channel water distribution systems by the Egyptians, Romans, and Babylonians.

4. CM4120 Unit Operations Lab Piping Systems
Primary Design Consideration is Safety
Evaluate Process Conditions
Temperature
Pressure
Chemical compatibility/Corrosion allowances
Vibration, flexing, bending
Expansion/Contraction due to temperature change
Environmental conditions
Evaluate the Effects of a Leak
Evaluate Performance in a Fire Situation
Before starting to design a piping system there are many considerations.
Foremost concern in any good design is safety.

5. CM4120 Unit Operations Lab Piping Systems
Secondary Considerations
Evaluate any Special Requirements
Sanitary requirements – “Cleanability”
Serviceability – ease of maintenance of equipment
Possible contamination of process fluid by piping materials, sealants, or gasketing
Earthquake, Hurricane, Lightening, Permafrost
Lowest Cost over the Lifetime
Does the system have to be disassembled frequently for maintenance or cleaning?
Are there trace elements in the piping, sealants, or gasketing that may contaminate the process fluid or utility?
What is the total cost of the piping system over the expected life?

6. CM4120 Unit Operations Lab Piping Systems
Piping System Design Criteria
4 areas to consider:
Physical Attributes
Loading and Service Conditions
Environmental Factors
Materials-Related Considerations
Physical Attributes:
Size
Layout
Dimensional limits
Operability (slope for drainage, mechanical fittings for ease of dis-assembly
Loading/Service Conditions:
conditions that stress the piping system
- internal – from process fluids – pressure, temperature, T/P cycling
- external – from wind, ice, service personnel, traffic
also consider load cycling and load duration
must design for all expected combinations/ worst case
Environmental Factors:
physical and chemical conditions that deteriorate the system over time
- corrosion (internal or external)
- erosion
- physical damage – fork lift operators
Materials-Related Considerations:
Strength – something like 2/3 of yield strength
Toughness
- use ductile materials, CS is ductile down to T = 0 F, then reduce P rating
Corrosion resistance
– negligible over design lifetime, increase wall thickness if necessary
- use design temp to determine corrosion rate
- will corrosion create process fluid contamination problem?
- Special considerations – CS is subject to Graphitization when T>775 F
for long periods (carbon converts to graphite and becomes brittle)
Pressure integrity – Leak-tight WRT stress/strain in pipe system (not gaskets or seals)

7. CM4120 Unit Operations Lab Piping Systems
Codes and Standards simplify design, manufacturing, installation process
Standards – provide design criteria for components
standard sizes for pipe
dimensions for fittings or valves
Codes – specific design/fabrication methodologies
Incorporated into local/regional statute
It’s the LAW
Use commonly accepted methods
-- reduce design time
-- produce safe design
-- limit liability.

8. CM4120 Unit Operations Lab Piping Systems
ASME Boiler and Pressure Vessel Code
ASME B31: Code for Pressure Piping
ANSI Standards – dimensions for valves, piping, fittings, nuts/washers, etc.
ASTM Standards for piping and tube
API – Specs for pipe and pipelines
AWS, ASHRAE, NFPA, PPI, UL, etc.
Many professional and standards associations have developed codes and standard practices for the design, assembly, and testing of process piping.
Depending on which industry segment, which part of the plant, the type of service (drinking water vs. oil pipeline) or the type of construction, you would refer to the appropriate code or standard.
ASME boiler and pressure vessel code and B31 are most relevant to ChE
ANSI – American National Standards Institute
ASME – American Society of Mechanical Engineers
ASTM – American Society for Testing and Materials
API – American Petroleum Institute
PPI – Plastic Pipe Institute
AWS – American Welding Society
PFI – Pipe Fabrication Institute

9. CM4120 Unit Operations Lab Piping Systems
ASME B31 is the applicable standard for design of most piping systems in chemical plants
B31.1 – Power plant boilers
B31.3 – Chemical plant and refinery piping
B31.4 – Liquid petroleum transport
B31.7 – Nuclear power plant radioactive fluids
Within a chemical plant, one section will govern in one part of the plant.
In other parts of the plant, a different section may govern the design and installation.

10. CM4120 Unit Operations Lab Piping Systems
ASME B31.3 – Chemical Plant and Refinery Piping Code
Includes:
Process piping in chemical and refinery plants
Process piping in pharmaceutical and food processing
Process piping in textile and paper plants
Boiler piping
Most important for chemical engineers

11. CM4120 Unit Operations Lab Piping Systems
ASME B31.3 covers:
Materials and design
Fabrication
Erection and assembly
Support
Examination, inspection, and testing
Web reference:
Need to be familiar with B31.3 if you have plant responsibilities.
Code is laid out in sections, starting with scope and definitions and progressing thru design, inspection, and testing.

12. CM4120 Unit Operations Lab Piping Systems
Standard Pipe Sizes
Diameters are “Nominal”
Sizes 12” and less, nominal size < OD
Sizes 14” and over, nominal size = OD
Wall thickness inferred thru “Schedule”
Schedule = P/S * 1000
Defined Schedules:
5, 10, 20, 30, 40, 60, 80, 100, 120, 140, 160
Specs for piping found in ANSI B36.10 and B36.19
Attempt made to manufacture pipe systems to handle classes of allowable working pressure so that all diameters of pipe of the same pressure rating would be compatible.
“Schedule”
P = maximum allowable working pressure of pipe
S = allowable stress in pipe material
Higher the schedule, the thicker the wall, the higher the working pressure
The OD stays the same for all pipe of the same nominal diameter
Example: 4” schedule 40 pipe
OD = 4.50”
ID = 4.026”

13. CM4120 Unit Operations Lab Piping Systems
Standard Tubing Sizes
Steel tubing
Diameters are Actual OD
Wall thickness is specified
Refrigeration Tubing
Single wall thickness available for each size
Actual OD
Copper Tubing – Nominal sizes
Type K, L, M
Pipe is always round, tubing can be round, oval, or rectangular/square
Tubing specifications in ANSI B32.5
Example: Steel tubing
4” X ¼”
4” OD
3 ½” ID
Refrigeration tubing: ¾”
¾” OD w/ 0.035” wall for 0.680” ID
Copper Tubing
Type K is thickest
2” type K
OD = 2.125”
Wall = 0.083”
ID = 1.959”

14. CM4120 Unit Operations Lab Piping Systems
Materials – Metallic piping
Carbon and low alloy steel
Ductile
Inexpensive and available
Easy to machine, weld, cut
Some drawbacks
Can be cut, welded or threaded, and assembled using commonly available skilled labor
Subject to Embrittlement failures
caustics
high pressure steam
Conversion of carbides to graphite
exposure to high temp over time
Subject to hydrogen stress cracking

15. CM4120 Unit Operations Lab Piping Systems
Materials – Metallic piping
Alloy Steels including “Stainless Steels”
Good corrosion resistance
More difficult to machine, weld, cut
Some drawbacks
Requires special welding techniques
Harder to cut, thread and machine
Stress corrosion failures
exposure to chlorides
Embrittlement failure
After exposure to high temp (welding without annealing)

16. CM4120 Unit Operations Lab Piping Systems
Materials – Metallic piping
Nickel, Titanium, Copper, etc.
Copper is used in residential and commercial applications and is widely available
Other materials are expensive and difficult to machine, weld, join
Some incompatibilities with each

17. CM4120 Unit Operations Lab Piping Systems
Materials – Non-Metallic piping
Thermoplastics
Wide range of chemical compatibility
Light weight
Easily cut and joined
Low temperature limits
Need extra supports

18. CM4120 Unit Operations Lab Piping Systems
Materials – Non-Metallic piping
Fiberglass Reinforced Pipe
Wide range of chemical compatibility
Easily cut and joined
Wider temperature limits than thermoplastics
Thermal expansion similar to carbon steel
Similar structural performance as carbon steel

19. CM4120 Unit Operations Lab Piping Systems
Materials – Others
Glass
Concrete
Lined or coated
Rubber
Cement
Teflon
Zinc (galvanized pipe)
Double Containment piping systems
Used for low cost, corrosion resistance, long life, ease of cleaning
Lined pipe is chemical resistant inner layer with structural outer layer

20. CM4120 Unit Operations Lab Piping Systems
Piping Insulation
Prevent heat loss/ gain
Prevent condensation – below ambient
Personnel protection – over 125oF
Freeze protection – outdoor cold climates
Fire protection
Noise control
Insulating material and covering system
If the pipe is exposed to washdown or is installed outdoors, need to consider the effects of water on insulating material.
Must consider:
physical abuse of insulating system
location of supports
proximity to adjacent runs of pipe
connections to equipment, valves, and instrumentation
Most insulating systems also include a protective covering of cloth, metal, or plastic.

21. CM4120 Unit Operations Lab Piping Systems
Fiberglass Insulation w/ Asbestos plastered fitting coverings
Plaster of Asbestos was hand-formed around each fitting
Often these systems were cloth covered.

22. CM4120 Unit Operations Lab Piping Systems
Metal Jacketed
insulation covering
Jacketing can be aluminum, galvanized steel or stainless steel.
This is embossed aluminum – indoor application.
Also preformed plastic is available.

23. CM4120 Unit Operations Lab Piping Systems
Heat Tracing
Prevents flow problems in cold climates
Freeze protection
Loss of flow due to viscosity increase
Prevent condensation in vapor lines
Methods
Electric
Hot Fluids
Heat tape or pipe runs along side of process pipe.
Induction heating of the pipe can also be used.
Steam is most common fluid.
Glycols in a recirculating system.
Insulation covers the pipe and heat tracing.

24. CM4120 Unit Operations Lab Piping Systems
Piping Supports
Prevent strain at connections
Prevent sag
Must allow for expansion/contraction
Design for wind/snow and ice/earthquake
Clearance for plant traffic and equipment
Determining max. space between supports is part of design process.

25. CM4120 Unit Operations Lab Piping Systems
Results of inadequate support

26. CM4120 Unit Operations Lab Piping Systems
Results of inadequate support: Flixborough, England
May, 1974 – Leaking reactor removed from train of reactors and temporarily replaced with a section of pipe
June, 1974 – Supports collapse, pipe breaks
28 dead, 89 injured, 1800 houses damaged, 160 shops and factories damaged, large crater where plant stood

27. CM4120 Unit Operations Lab Piping Systems
The Design Process – a three step approach
Design for Flow
Find min. diameter to achieve desired flow velocity
Design for Pressure Integrity
Find min. wall thickness for process and external conditions
Find appropriate rating of in-line components
Re-check for Flow Criteria

28. CM4120 Unit Operations Lab Piping Systems
Design for Flow
Determined by economics
Piping system must provide reliable service for expected life
Smallest diameter usually is lowest cost
First step is to determine appropriate flow velocity for each piping segment.
Find minimum pipe ID to attain the velocity.
Select the next largest available size of Standard Weight pipe.

29. CM4120 Unit Operations Lab Piping Systems
Typical design velocity Rules of Thumb when sizing piping...
Water lines: 5-7 ft/sec
Pump discharge: (d/2 + 4 ft/sec)
Pump suction: (1/3 * discharge velocity)
Steam: d in 1000 ft/min
Slurries: > min. entrainment velocity
d = I.D. of pipe in inches
from Rase and Barrow, Project Engineering of Process Plants, John Wiley, New York, 1957.
Reduce pumping losses
Minimize noise levels
Slurries – need to keep solids entrained and prevent sedimentation
Pump suction lines – need to minimize head loss in suction piping so that fluid doesn’t vaporize in/at pump

30. CM4120 Unit Operations Lab Piping Systems
Next determine wall thickness:
Pressure Integrity Design method
ASME B31.3,
ASME B31.3 uses Pressure-Integrity design method for determining the min. wall thickness.
All design factors are included in the appropriate code.
Need to reduce pressure ratings for high-low temp
Need to add mat’l for corrosion/erosion allowance
Need to add mat’l for external loads
Need to add material for threading, grooving, other material removal process
tm=min. wall thickness
P=design pressure, psig
D=O.D. of pipe, in.
S=allowable stress, psi
E=weld joint efficiency
y=factor to adjust for temp
A= add’l thickness for corrosion, external loads, etc.

31. CM4120 Unit Operations Lab Piping Systems
Finally re-check ID
Select in-line components
Determine insulation, coverings, coatings
Design and locate supports and hangers
Heavy wall pipe may have reduced the ID below the min allowable based on flow velocity criteria.
Using the same temp/press data as for piping design, select the “class” of fittings and valves.

32. CM4120 Unit Operations Lab Piping Systems
Effect of Thermal Expansion
Example:
Calculate the expansion per 20’ length of 2”, schedule 40 carbon steel steam line at boiler startup for a 100 psig steam service.
α=thermal expansion coefficient
for mild steel, α =6.6x10-6 in/inoF

33. CM4120 Unit Operations Lab Piping Systems
Temp of pipe at amb. cond. =70oF
Temp of 100 psig sat. steam =338oF
ΔT=268oF
L=20’=240”
expansion due to temperature
increase is α *L* ΔT
=(6.6x10-6in/inoF)*(240in)*(268oF)
=0.42” in per 20’ of pipe

34. CM4120 Unit Operations Lab Piping Systems
What force is exerted on the end restraints of that 20’ pipe if it is rigidly installed (end restraints can’t move)?
σ=internal stress due to ΔT, and
σ = α *(ΔT)*E
E is the material property called Modulus of Elasticity, relationship between stress and strain
E=30x106 psi for low carbon steel

35. CM4120 Unit Operations Lab Piping Systems
=(6.6x10-6 in/inoF)*(268oF)*(30x106lbf/in2)
=53,000 lbf/in2
since σ=F/A, F=σ*A
where: F=force on end restraints
A=cross sec. area of 2”, sched pipe

36. CM4120 Unit Operations Lab Piping Systems
A=Π(OD2-ID2)/4
= Π( )/4
=1.07 sq.in
F= σ*A
=(53,000 lbf/in2)*(1.07 in2)
Force on the end restraints =57,000 lbf
or 28.5 tons

37. CM4120 Unit Operations Lab Piping Systems
Pipe Joints
Threaded
Welded
Soldered/ Brazed
Glued
Compression
Bell and spigot
Upset or expanded
Most common are threaded and welded
Threaded – up to 2”
Welded – butt welded or socket welded
Upset – for thin wall pipe and tubing

38. CM4120 Unit Operations Lab Piping Systems
Threaded joints

39. CM4120 Unit Operations Lab Piping Systems
Soldered joints

40. CM4120 Unit Operations Lab Piping Systems
Welded joints

41. CM4120 Unit Operations Lab Piping Systems
Compression joints

42. CM4120 Unit Operations Lab Piping Systems
Mechanical joints
shown on glass drain piping system

43. CM4120 Unit Operations Lab Piping Systems
Pipe Fittings
Forged
Cast
Malleable Iron
Pressure/Temperature Rated by “Class”
125, 250, or 2000, 3000, etc.
Need a look-up table to determine max. allowable P for the design temperature
Used to connect or adapt pipe to other pipe or equipment.
Used to change directions.
Used to change pipe diameter or terminate a pipe run.
Forged Steel in threaded or socket weld
Cast Iron, bronze, brass
Malleable Iron generally in threaded

44. CM4120 Unit Operations Lab Piping Systems
Fittings for joining 2 sections of pipe:
Coupling
Reducing Coupling
Union
Flange
Couplings join two lengths of pipe
Reducing couplings used for joining two lengths of pipe of different diameters. Can be concentric or eccentric.
Unions and flanges are used when piping must be dis-assembled

45. CM4120 Unit Operations Lab Piping Systems
Fittings for changing directions in pipe:
45o Ell
90o Ell
Street Ell
Both short and long-radius fittings available

46. CM4120 Unit Operations Lab Piping Systems
Fittings for adding a branch in a run of piping:
Tee
Cross

47. CM4120 Unit Operations Lab Piping Systems
Fittings for blocking the end of a run of piping:
Pipe plug
Pipe cap
Blind Flange
Caps, plugs, and blind flanges are used to block off the end of a pipe

48. CM4120 Unit Operations Lab Piping Systems
Misc. pipe fittings:
Nipple
Reducing bushing
Nipples lengths up to 12 inch standard, other lengths available
Reducing bushings are typically used to reduce the size of a tank or vessel fitting to the size of the pipe run.
Not normally used as in-line fittings.

49. CM4120 Unit Operations Lab Piping Systems
Gate Valve:
Used to block flow (on/off service)
Sliding “gate”
on knife-gate
valve

50. CM4120 Unit Operations Lab Piping Systems
Globe Valve:
Used to regulate flow
Cut-away shows
stem seal
plug
and seat

51. CM4120 Unit Operations Lab Piping Systems
Ball Valve:
Typically used as block valve
“Quarter-turn” valve
Cut-away shows ball and seat

52. CM4120 Unit Operations Lab Piping Systems
Butterfly Valve:
Can be used for flow control or on/off
Valve actuator/ positioner for accurate flow control

53. CM4120 Unit Operations Lab Piping Systems
Check Valves:
Used to prevent backflow
Piston check
Swing check

54. CM4120 Unit Operations Lab Piping Systems
References:
Piping Handbook, 7th ed., Nayyar, McGraw-Hill, New York, 2000.
Piping Design for Process Plants, Rase, John Wiley, New York, 1963.
Valve Handbook, Skousen, McGraw-Hill, New York, 1998
Flowserve Corp., Sept
The Engineering Toolbox, Sept