Piping Systems

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
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CM4120
Unit Operations Lab
Piping Systems
Piping Systems include:
 Pipe
 Flanges
 Fittings
 Bolting
 Gaskets
 Valves
 Hangers and supports
 Insulations, coverings, coatings
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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, 7
th
ed.
McGraw-Hill, 2000
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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
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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
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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


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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

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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.
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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

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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

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CM4120
Unit Operations Lab
Piping Systems
ASME B31.3 covers:
Materials and design
Fabrication
Erection and assembly
Support
Examination, inspection, and testing

Web reference: www.piping-toolbox.com
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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

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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
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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
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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

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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

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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
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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

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CM4120
Unit Operations Lab
Piping Systems
Materials – Others
Glass
Concrete
Lined or coated
 Glass
 Rubber
 Cement
 Teflon
 Zinc (galvanized pipe)
Double Containment piping systems
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CM4120
Unit Operations Lab
Piping Systems
Piping Insulation
Prevent heat loss/ gain
Prevent condensation – below ambient
Personnel protection – over 125
o
F
Freeze protection – outdoor cold climates
Fire protection
Noise control
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CM4120
Unit Operations Lab
Piping Systems
Fiberglass Insulation w/ Asbestos plastered
fitting coverings

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Unit Operations Lab
Piping Systems
Metal Jacketed
insulation covering
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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
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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
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CM4120
Unit Operations Lab
Piping Systems
Results of inadequate support

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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



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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
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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

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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.
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CM4120
Unit Operations Lab
Piping Systems
Next determine wall thickness:
Pressure Integrity Design method
ASME B31.3,
 
A
Py SE
PD
tm 


2
t
m
=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.
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CM4120
Unit Operations Lab
Piping Systems
Finally re-check ID

Select in-line components

Determine insulation, coverings, coatings

Design and locate supports and hangers
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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/in
o
F

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CM4120
Unit Operations Lab
Piping Systems
Temp of pipe at amb. cond. =70
o
F
Temp of 100 psig sat. steam =338
o
F
ΔT=268
o
F
L=20’=240”
expansion due to temperature
increase is α *L* ΔT
=(6.6x10
-6
in/in
o
F)*(240in)*(268
o
F)
=0.42” in per 20’ of pipe
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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=30x10
6
psi for low carbon steel

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CM4120
Unit Operations Lab
Piping Systems
σ= α *(ΔT)*E
=(6.6x10
-6
in/in
o
F)*(268
o
F)*(30x10
6
lb
f
/in
2
)
=53,000 lb
f
/in
2

since σ=F/A, F=σ*A
where: F=force on end restraints
A=cross sec. area of 2”, sched 40
pipe
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CM4120
Unit Operations Lab
Piping Systems
A=Π(OD
2
-ID
2
)/4
= Π(2.375
2
-2.067
2
)/4
=1.07 sq.in

F= σ*A
=(53,000 lb
f
/in
2
)*(1.07 in
2
)
Force on the end restraints =57,000 lb
f
or 28.5 tons

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CM4120
Unit Operations Lab
Piping Systems
Pipe Joints
 Threaded
 Welded
 Soldered/ Brazed
 Glued
 Compression
 Bell and spigot
 Upset or expanded

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CM4120
Unit Operations Lab
Piping Systems
Threaded joints

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CM4120
Unit Operations Lab
Piping Systems
Soldered joints

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Unit Operations Lab
Piping Systems
Welded joints

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CM4120
Unit Operations Lab
Piping Systems
Compression joints

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

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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
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CM4120
Unit Operations Lab
Piping Systems
Fittings for joining 2
sections of pipe:
Coupling

Reducing Coupling

Union

Flange
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CM4120
Unit Operations Lab
Piping Systems
Fittings for changing
directions in pipe:
45
o
Ell

90
o
Ell

Street Ell
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CM4120
Unit Operations Lab
Piping Systems
Fittings for adding
a branch in a run
of piping:
Tee

Cross


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CM4120
Unit Operations Lab
Piping Systems
Fittings for blocking
the end of a run of
piping:
Pipe plug

Pipe cap

Blind Flange
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CM4120
Unit Operations Lab
Piping Systems
Misc. pipe fittings:
Nipple

Reducing bushing


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CM4120
Unit Operations Lab
Piping Systems
Gate Valve:
Used to block flow
(on/off service)


Sliding “gate”
on knife-gate
valve
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CM4120
Unit Operations Lab
Piping Systems
Globe Valve:
Used to regulate
flow

Cut-away shows
stem seal
plug
and seat
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CM4120
Unit Operations Lab
Piping Systems
Ball Valve:
Typically used as
block valve

“Quarter-turn” valve

Cut-away shows ball
and seat
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CM4120
Unit Operations Lab
Piping Systems
Butterfly Valve:
Can be used for
flow control or
on/off
Valve actuator/
positioner for
accurate flow
control


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

Swing check


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CM4120
Unit Operations Lab
Piping Systems
References:
Piping Handbook, 7
th
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
www.flowserve.com, Flowserve Corp., Sept. 2004.
www.engineeringtoolbox.com, The Engineering
Toolbox, Sept. 2004.