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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. CM4120 Unit Operations Lab Piping Systems.

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cm4120 unit operations lab piping systems
CM4120Unit Operations LabPiping 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
cm4120 unit operations lab piping systems1
CM4120Unit Operations LabPiping Systems

Piping Systems include:

  • Pipe
  • Flanges
  • Fittings
  • Bolting
  • Gaskets
  • Valves
  • Hangers and supports
  • Insulations, coverings, coatings
cm4120 unit operations lab piping systems2
CM4120Unit Operations LabPiping 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

cm4120 unit operations lab piping systems3
CM4120Unit Operations LabPiping 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
cm4120 unit operations lab piping systems4
CM4120Unit Operations LabPiping 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
cm4120 unit operations lab piping systems5
CM4120Unit Operations LabPiping Systems

Piping System Design Criteria

4 areas to consider:

  • Physical Attributes
  • Loading and Service Conditions
  • Environmental Factors
  • Materials-Related Considerations
cm4120 unit operations lab piping systems6
CM4120Unit Operations LabPiping 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
cm4120 unit operations lab piping systems7
CM4120Unit Operations LabPiping 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.
cm4120 unit operations lab piping systems8
CM4120Unit Operations LabPiping 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
cm4120 unit operations lab piping systems9
CM4120Unit Operations LabPiping 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
cm4120 unit operations lab piping systems10
CM4120Unit Operations LabPiping Systems

ASME B31.3 covers:

  • Materials and design
  • Fabrication
  • Erection and assembly
  • Support
  • Examination, inspection, and testing

Web reference: www.piping-toolbox.com

cm4120 unit operations lab piping systems11
CM4120Unit Operations LabPiping 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

cm4120 unit operations lab piping systems12
CM4120Unit Operations LabPiping 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
cm4120 unit operations lab piping systems13
CM4120Unit Operations LabPiping Systems

Materials – Metallic piping

Carbon and low alloy steel

  • Ductile
  • Inexpensive and available
  • Easy to machine, weld, cut
  • Some drawbacks
cm4120 unit operations lab piping systems14
CM4120Unit Operations LabPiping Systems

Materials – Metallic piping

Alloy Steels including “Stainless Steels”

  • Good corrosion resistance
  • More difficult to machine, weld, cut
  • Some drawbacks
cm4120 unit operations lab piping systems15
CM4120Unit Operations LabPiping 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
cm4120 unit operations lab piping systems16
CM4120Unit Operations LabPiping Systems

Materials – Non-Metallic piping

Thermoplastics

  • Wide range of chemical compatibility
  • Light weight
  • Easily cut and joined
  • Low temperature limits
  • Need extra supports
cm4120 unit operations lab piping systems17
CM4120Unit Operations LabPiping 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
cm4120 unit operations lab piping systems18
CM4120Unit Operations LabPiping Systems

Materials – Others

Glass

Concrete

Lined or coated

  • Glass
  • Rubber
  • Cement
  • Teflon
  • Zinc (galvanized pipe)

Double Containment piping systems

cm4120 unit operations lab piping systems19
CM4120Unit Operations LabPiping Systems

Piping Insulation

  • Prevent heat loss/ gain
  • Prevent condensation – below ambient
  • Personnel protection – over 125oF
  • Freeze protection – outdoor cold climates
  • Fire protection
  • Noise control
cm4120 unit operations lab piping systems20
CM4120Unit Operations LabPiping Systems

Fiberglass Insulation w/ Asbestos plastered fitting coverings

cm4120 unit operations lab piping systems21
CM4120Unit Operations LabPiping Systems

Metal Jacketed

insulation covering

cm4120 unit operations lab piping systems22
CM4120Unit Operations LabPiping 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
cm4120 unit operations lab piping systems23
CM4120Unit Operations LabPiping 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
cm4120 unit operations lab piping systems24
CM4120Unit Operations LabPiping Systems

Results of inadequate support

cm4120 unit operations lab piping systems25
CM4120Unit Operations LabPiping 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

cm4120 unit operations lab piping systems26
CM4120Unit Operations LabPiping 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
cm4120 unit operations lab piping systems27
CM4120Unit Operations LabPiping Systems

Design for Flow

  • Determined by economics

Piping system must provide reliable service for expected life

Smallest diameter usually is lowest cost

cm4120 unit operations lab piping systems28
CM4120Unit Operations LabPiping 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.

cm4120 unit operations lab piping systems29
CM4120Unit Operations LabPiping Systems

Next determine wall thickness:

Pressure Integrity Design method

ASME B31.3,

E=weld joint efficiency

y=factor to adjust for temp

A= add’l thickness for corrosion, external loads, etc.

tm=min. wall thickness

P=design pressure, psig

D=O.D. of pipe, in.

S=allowable stress, psi

cm4120 unit operations lab piping systems30
CM4120Unit Operations LabPiping Systems

Finally re-check ID

Select in-line components

Determine insulation, coverings, coatings

Design and locate supports and hangers

cm4120 unit operations lab piping systems31
CM4120Unit Operations LabPiping 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

cm4120 unit operations lab piping systems32
CM4120Unit Operations LabPiping 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

cm4120 unit operations lab piping systems33
CM4120Unit Operations LabPiping 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

cm4120 unit operations lab piping systems34
CM4120Unit Operations LabPiping Systems

σ= α *(ΔT)*E

=(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 40 pipe

cm4120 unit operations lab piping systems35
CM4120Unit Operations LabPiping Systems

A=Π(OD2-ID2)/4

= Π(2.3752-2.0672)/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

cm4120 unit operations lab piping systems36
CM4120Unit Operations LabPiping Systems

Pipe Joints

  • Threaded
  • Welded
  • Soldered/ Brazed
  • Glued
  • Compression
  • Bell and spigot
  • Upset or expanded
cm4120 unit operations lab piping systems41
CM4120Unit Operations LabPiping Systems

Mechanical joints

shown on glass drain piping system

cm4120 unit operations lab piping systems42
CM4120Unit Operations LabPiping 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
cm4120 unit operations lab piping systems43
CM4120Unit Operations LabPiping Systems

Fittings for joining 2 sections of pipe:

Coupling

Reducing Coupling

Union

Flange

cm4120 unit operations lab piping systems44
CM4120Unit Operations LabPiping Systems

Fittings for changing directions in pipe:

45o Ell

90o Ell

Street Ell

cm4120 unit operations lab piping systems45
CM4120Unit Operations LabPiping Systems

Fittings for adding a branch in a run of piping:

Tee

Cross

cm4120 unit operations lab piping systems46
CM4120Unit Operations LabPiping Systems

Fittings for blocking the end of a run of piping:

Pipe plug

Pipe cap

Blind Flange

cm4120 unit operations lab piping systems47
CM4120Unit Operations LabPiping Systems

Misc. pipe fittings:

Nipple

Reducing bushing

cm4120 unit operations lab piping systems48
CM4120Unit Operations LabPiping Systems

Gate Valve:

Used to block flow (on/off service)

Sliding “gate”

on knife-gate

valve

cm4120 unit operations lab piping systems49
CM4120Unit Operations LabPiping Systems

Globe Valve:

Used to regulate flow

Cut-away shows

stem seal

plug

and seat

cm4120 unit operations lab piping systems50
CM4120Unit Operations LabPiping Systems

Ball Valve:

Typically used as block valve

“Quarter-turn” valve

Cut-away shows ball and seat

cm4120 unit operations lab piping systems51
CM4120Unit Operations LabPiping Systems

Butterfly Valve:

Can be used for flow control or on/off

Valve actuator/ positioner for accurate flow control

cm4120 unit operations lab piping systems52
CM4120Unit Operations LabPiping Systems

Check Valves:

Used to prevent backflow

Piston check

Swing check

cm4120 unit operations lab piping systems53
CM4120Unit Operations LabPiping 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
  • www.flowserve.com, Flowserve Corp., Sept. 2004.
  • www.engineeringtoolbox.com, The Engineering Toolbox, Sept. 2004.