Piping Systems in the Chemical Process Industries

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Nov 29, 2013 (3 years and 10 months ago)

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1

CM4120

Unit Operations Lab

Piping Systems

Piping Systems in the Chemical Process
Industries

March, 2009


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


Heat Tracing

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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 Routing and Layout

The unwritten #1 rule:

Serviceability/Operability





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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 Pertinent sections

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 piping systems in:

Chemical and refinery plants

Pharmaceutical and food processing

Textile and paper plants

Boilers


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CM4120

Unit Operations Lab

Piping Systems

ASME B31.3 covers:

Materials of construction

Piping design process

Fabrication, Erection, Assembly

Design of supports

Examination, inspection, and testing


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CM4120

Unit Operations Lab

Piping Systems

Piping Design Process


a three step
approach


1.
Design for Flow


Find min. diameter to achieve desired flow velocity

2.
Design for Pressure Integrity


Find min. wall thickness for process and external
conditions


Find appropriate rating of in
-
line components

3.
Re
-
check for Flow Criteria

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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”



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

Criteria for Design for Flow


Economics

Serviceable over Design Life

Smallest diameter usually is lowest cost

Performance

Minimum entrainment velocity

Prevent erosion or
cavitation

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CM4120

Unit Operations Lab

Piping Systems

Design Rules of Thumb when sizing for velocity...


Water lines: 3
-
10 ft/sec

Pump discharge: 3
-
12 ft/sec

Pump suction: (1/3 x discharge velocity)

Steam: low pressure (25 psig or less) 50
-
100 ft/sec




high pressure (>100 psig) 100
-
200 ft/sec

Slurries: > min. entrainment velocity



from Peters and
Timmerhaus
,
Plant Design and Economics for
Chemical Engineers, 4
th

ed.,
McGraw
-
Hill, 1991.

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CM4120

Unit Operations Lab

Piping Systems

Selecting appropriate pipe
Schedule


Schedule = P/S * 1000

P = max. working pressure of pipe, psig

S = allowable stress in piping material, psi

For carbon steel pipe, S = 36,000 psi



What is max. working pressure for Schedule
40 Carbon Steel pipe?


psig
P
1440
1000
000
,
36
*
40


19

CM4120

Unit Operations Lab

Piping Systems

Determine min.
req’d

wall thickness:

Pressure Integrity Design Method


ASME B31.3,



A
Py
SE
PD
t
m



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

After determining wall thickness:

Re
-
check ID for velocity;


Select in
-
line components;


Determine insulation, coverings, coatings;


Design and locate supports and hangers.

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CM4120

Unit Operations Lab

Piping Systems

Inline Components:

Fittings

Valves

Gaskets, Seals, and Thread Sealants

Connection Hardware


Bolts, studs, nuts,
washers

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CM4120

Unit Operations Lab

Piping Systems

Pipe Fittings
-

Steel


Forged


Cast


Malleable Iron



Select “Class” of Fittings


150 lb., 300 lb., 600 lb., etc.


Need a look
-
up table to determine max.
allowable P at the design temperature

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CM4120

Unit Operations Lab

Piping Systems

Maximum Allowable non
-
shock Pressure
(psig)

Temperature

(
o
F
)

Pressure Class
Rating for Flanged Fittings
(lb
)

150

300

400

600

900

1500

2500

Hydrostatic Test Pressure
(psig)

450

1125

1500

2225

3350

5575

9275

-
20 to 100

285

740

990

1480

2220

3705

6170

200

260

675

900

1350

2025

3375

5625

300

230

655

875

1315

1970

3280

5470

400

200

635

845

1270

1900

3170

5280

500

170

600

800

1200

1795

2995

4990

600

140

550

730

1095

1640

2735

4560

650

125

535

715

1075

1610

2685

4475

700

110

535

710

1065

1600

2665

4440

750

95

505

670

1010

1510

2520

4200

800

80

410

550

825

1235

2060

3430

850

65

270

355

535

805

1340

2230

900

50

170

230

345

515

860

1430

950

35

105

140

205

310

515

860

1000

20

50

70

105

155

260

430

Ratings for flanged steel pipe fittings, ANSI B16.5
-

1988.

http://www.engineeringtoolbox.com/ansi
-
flanges
-
pressure
-
temperature
-
d_342.html

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CM4120

Unit Operations Lab

Piping Systems

Design Checklist:

Re
-
check ID for velocity;


Select in
-
line components;


Determine insulation, coverings, coatings;


Design and locate supports and hangers.

25

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

26

CM4120

Unit Operations Lab

Piping Systems

Recommended minimum Thickness of Insulation

(inches)
*

Nominal Pipe Size

NPS

(inches)

Temperature Range
(
o
C)

50
-

90

90
-

120

120
-

150

150
-

230

Temperature Range

(
o
F)

120
-

200

201
-

250

251
-

305

306
-

450

Hot Water

Low Pressure
Steam

Medium Pressure
Steam

High Pressure
Steam

< 1"

1.0

1.5

2.0

2.5

1 1/4"
-

2"

1.0

1.5

2.5

2.5

2 1/2"
-

4"

1.5

2.0

2.5

3.0

5"
-

6"

1.5

2.0

3.0

3.5

> 8"

1.5

2.0

3.0

3.5

* based on insulation with thermal resistivity in the range
4
-

4.6 ft
2

hr
o
F
/ Btu in

Source: Engineering Toolbox,
http://www.engineeringtoolbox.com/pipes
-
insulation
-
thickness
-
d_16.html
, 3
-
26
-
2009

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CM4120

Unit Operations Lab

Piping Systems

Common Types of Insulation


Mineral Fiber


Fiberglas


Rock wool


Cellular glass


(Asbestos or Asbestos
-
containing)

Polymeric closed cell foams


Flexible


polyethylene


Rigid foam


polystyrene, polyurethanes


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CM4120

Unit Operations Lab

Piping Systems

Fiberglass Insulation w/ Asbestos
-
plastered
fitting coverings


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CM4120

Unit Operations Lab

Piping Systems

Metal Jacketed

insulation covering

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CM4120

Unit Operations Lab

Piping Systems

After determining wall thickness:

Re
-
check ID for velocity;


Select in
-
line components;


Determine insulation, coverings, coatings;


Design and locate supports and hangers.

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CM4120

Unit Operations Lab

Piping Systems

Piping Supports


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CM4120

Unit Operations Lab

Piping Systems

Supports


Prevent strain at connections

Prevent sag

Allow for expansion/contraction

Design for wind, snow/ice, earthquake

Provide clearance for plant traffic/equipment

33

CM4120

Unit Operations Lab

Piping Systems

Steel Pipe
-

Distance between Supports
(ft)

Outside Diameter

(in)

Horizontal Run

Vertical Run

1/2

4.5

10

3/4

7.5

10

1

7.5

10

1 1/4

7.5

12

1 1/2

7.5

12

2

7.5

15

2 1/2

10

15

3

10

15

4

10

18

Source: Engineering Toolbox,
http://www.engineeringtoolbox.com/steel
-
pipe
-
supports
-
d_1071.html
, 2
-
26
-
09

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CM4120

Unit Operations Lab

Piping Systems

Inadequate support


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CM4120

Unit Operations Lab

Piping Systems

Effect of Thermal Expansion on piping
and supports

Example 1:

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


36

CM4120

Unit Operations Lab

Piping Systems

Temp of pipe at
amb
. cond. =70
o
F

Temp of 100 psig sat. steam =338
o
F

Δ
T=268
o
F

L=20’=240”

expansion due to temperature

increase is

α
*L*
Δ
T



=(6.6x10
-
6
in/
in
o
F
)*(240in)*(268
o
F)





=
0.42” in per 20’ of pipe

37

CM4120

Unit Operations Lab

Piping Systems

Example 2:

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
Δ
T, and



σ
=

α
*(
Δ
T)*E

E is the material property called Modulus of
Elasticity, relationship between stress and
strain

E=30x10
6

psi for low carbon steel


38

CM4120

Unit Operations Lab

Piping Systems

σ
=
α
*(
Δ
T)*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,

The force on the end restraints is F=
σ
*A

where:

F=force in
lb
f




A=cross sec. area of 2”,
sched

40



pipe in sq. inches

39

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


40

CM4120

Unit Operations Lab

Piping Systems

Results of inadequate support:
Flixborough
,
England


May, 1974


Leaking reactor #5 removed from train
of 6 reactors and temporarily replaced with a
section of 20” pipe. Pipe is supported by
scaffolding.


June 1, 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

Heat Tracing


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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

43

CM4120

Unit Operations Lab

Piping Systems

References:

Piping Handbook
, 7
th

ed.,
Nayyar
, McGraw
-
Hill, New
York, 2000.

Plant
Desing

and Economics for Chemical Engineers,
4
th

ed.,
Peters and
Timmerhaus
, McGraw
-
Hill, 1991.

Valve Handbook
,
Skousen
, McGraw
-
Hill, New York,
1998

www.flowserve.com
, Flowserve Corp., Sept. 2004.

www.engineeringtoolbox.com
, The Engineering
Toolbox, Sept. 2004.

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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


46

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


47

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

48

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


49

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

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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CM4120

Unit Operations Lab

Piping Systems

Welded joints


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CM4120

Unit Operations Lab

Piping Systems

Compression joints


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CM4120

Unit Operations Lab

Piping Systems

Mechanical joints


shown on glass drain piping system


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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