1 CM4120 Unit Operations Lab Piping Systems Piping Systems in the Chemical Process Industries March,...

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CM4120Unit Operations Lab

Piping Systems

Piping Systems in the Chemical Process IndustriesMarch, 2009

Introduction Basis for Design Piping Codes and Standards Design of Process Piping Systems Joints and Fittings Valves

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Piping Systems

Piping Systems include: Pipe, Flanges, Fittings Bolting, Gaskets Valves Hangers and Supports Insulations, Coverings,

Coatings Heat Tracing

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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

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Piping Systems

Primary Design Consideration is SafetyEvaluate Process Conditions Temperature Pressure Chemical compatibility/Corrosion allowances Vibration, flexing, bending Expansion/Contraction due to temperature

change Environmental conditions

Evaluate the Effects of a LeakEvaluate Performance in a Fire Situation

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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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Piping Systems

Piping System Routing and LayoutThe unwritten #1 rule:

Serviceability/Operability

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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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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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Piping Systems

ASME Boiler and Pressure Vessel CodeASME B31: Code for Pressure PipingANSI Standards – dimensions for valves, piping, fittings, nuts/washers, etc.ASTM Standards for piping and tubeAPI – Specs for pipe and pipelinesAWS, ASHRAE, NFPA, PPI, UL, etc.

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Piping Systems

ASME B31 Pertinent sectionsB31.1 – Power plant boilersB31.3 – Chemical plant and refinery pipingB31.4 – Liquid petroleum transportB31.7 – Nuclear power plant radioactive fluids

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Piping Systems

ASME B31.3 – Chemical Plant and Refinery Piping Code

Includes piping systems in:Chemical and refinery plantsPharmaceutical and food processingTextile and paper plantsBoilers

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Piping Systems

ASME B31.3 covers:Materials of constructionPiping design processFabrication, Erection, AssemblyDesign of supportsExamination, inspection, and testing

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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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Piping Systems

Standard Pipe SizesDiameters 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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Piping Systems

Standard Tubing SizesSteel 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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Piping Systems

Criteria for Design for Flow

EconomicsServiceable over Design LifeSmallest diameter usually is lowest cost

PerformanceMinimum entrainment velocityPrevent erosion or cavitation

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Piping Systems

Design Rules of Thumb when sizing for velocity...

Water lines: 3-10 ft/secPump discharge: 3-12 ft/secPump suction: (1/3 x discharge velocity)Steam: low pressure (25 psig or less) 50-100

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

ft/secSlurries: > min. entrainment velocity

from Peters and Timmerhaus, Plant Design and Economics for Chemical Engineers, 4th ed., McGraw-Hill, 1991.

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Piping Systems

Selecting appropriate pipe Schedule Schedule = P/S * 1000

P = max. working pressure of pipe, psigS = allowable stress in piping material, psiFor carbon steel pipe, S = 36,000 psi

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

psigP 14401000

000,36*40

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Piping Systems

Determine min. req’d wall thickness:Pressure Integrity Design Method

ASME B31.3,

APySE

PDtm

2

tm=min. wall thickness

P=design pressure, psigD=O.D. of pipe, in.S=allowable stress, psi

E=weld joint efficiencyy=factor to adjust for tempA= add’l thickness for

corrosion, external loads, etc.

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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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Piping Systems

Inline Components:FittingsValvesGaskets, Seals, and Thread SealantsConnection Hardware – Bolts, studs,

nuts, washers

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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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Piping Systems

Maximum Allowable non-shock Pressure (psig)

Temperature(oF)

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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Piping Systems

Design Checklist:Re-check ID for velocity;




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Piping Systems

Piping Insulation

Prevent heat loss/ gainPrevent condensation – below ambientPersonnel protection – over 125oFFreeze protection – outdoor cold climatesFire protectionNoise control

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Piping Systems

Recommended minimum Thickness of Insulation (inches)*

Nominal Pipe SizeNPS

(inches)

Temperature Range (oC)

50 - 90 90 - 120 120 - 150 150 - 230

Temperature Range (oF)

120 - 200 201 - 250 251 - 305 306 - 450

Hot WaterLow Pressure

SteamMedium Pressure

SteamHigh 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 ft2 hr oF/ Btu inSource: Engineering Toolbox, http://www.engineeringtoolbox.com/pipes-insulation-thickness-d_16.html, 3-26-2009

http://www.engineeringtoolbox.com/pipes-insulation-thickness-d_16.html

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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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Piping Systems

Fiberglass Insulation w/ Asbestos-plastered fitting coverings

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Piping Systems

Metal Jacketedinsulation

covering

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Piping Systems

After determining wall thickness:Re-check ID for velocity;




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Piping Systems

Piping Supports

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Piping Systems

Supports

Prevent strain at connectionsPrevent sagAllow for expansion/contractionDesign for wind, snow/ice, earthquakeProvide clearance for plant traffic/equipment

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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

http://www.engineeringtoolbox.com/steel-pipe-supports-d_1071.html

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Piping Systems

Inadequate support

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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 coefficientfor mild steel, α =6.6x10-6 in/inoF

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Piping Systems

Temp of pipe at amb. cond. =70oFTemp of 100 psig sat. steam =338oFΔT=268oFL=20’=240”expansion due to temperatureincrease is α *L* ΔT

=(6.6x10-6in/inoF)*(240in)*(268oF)=0.42” in per 20’ of pipe

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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 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

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Piping Systems

σ= α *(ΔT)*E=(6.6x10-6 in/inoF)*(268oF)*(30x106lbf/in2)

=53,000 lbf/in2

since σ=F/A,The force on the end restraints is F=σ*Awhere:F=force in lbf

A=cross sec. area of 2”, sched 40 pipe in sq. inches

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Piping 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

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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 breaks28 dead, 89 injured, 1800 houses damaged, 160 shops and factories damaged, large crater where plant stood

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Piping Systems

Heat Tracing

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Piping Systems

Heat Tracing

Prevents flow problems in cold climates Freeze protection Loss of flow due to viscosity increase

Prevent condensation in vapor linesMethods Electric Hot Fluids

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Piping Systems

References:Piping Handbook, 7th ed., Nayyar, McGraw-Hill, New York, 2000.Plant Desing and Economics for Chemical Engineers, 4th ed., Peters and Timmerhaus, McGraw-Hill, 1991.Valve Handbook, Skousen, McGraw-Hill, New York, 1998www.flowserve.com, Flowserve Corp., Sept. 2004.www.engineeringtoolbox.com, The Engineering Toolbox, Sept. 2004.

http://www.flowserve.com/

http://www.engineeringtoolbox.com/

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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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Piping Systems


Alloy Steels including “Stainless Steels” Good corrosion resistance More difficult to machine, weld, cut Some drawbacks

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Piping Systems


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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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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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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Piping Systems

Materials – OthersGlassConcreteLined or coated

Glass Rubber Cement Teflon Zinc (galvanized pipe)

Double Containment piping systems

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Piping Systems

Pipe Joints Threaded Welded Soldered/ Brazed Glued Compression Bell and spigot Upset or expanded

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Piping Systems

Threaded joints

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Piping Systems

Soldered joints

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Piping Systems

Welded joints

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Piping Systems

Compression joints

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Piping Systems

Mechanical jointsshown on glass drain piping system

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Piping Systems

Fittings for joining 2 sections of pipe:

Coupling

Reducing Coupling

Union

Flange

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Piping Systems

Fittings for changing directions in pipe:

45o Ell

90o Ell

Street Ell

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Piping Systems

Fittings for adding a branch in a run of piping:

Tee

Cross

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Piping Systems

Fittings for blocking the end of a run of piping:

Pipe plug

Pipe cap

Blind Flange

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Piping Systems

Misc. pipe fittings:

Nipple

Reducing bushing

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Piping Systems

Gate Valve:Used to block

flow (on/off service)

Sliding “gate”on knife-gatevalve

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Piping Systems

Globe Valve:Used to

regulate flow

Cut-away showsstem seal

plug and seat

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Piping Systems

Ball Valve:Typically used

as block valve

“Quarter-turn” valve

Cut-away shows ball and seat

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Piping Systems

Butterfly Valve:

Can be used for flow control or on/off

Valve actuator/ positioner for accurate flow

control

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Piping Systems

Check Valves:Used to prevent

backflow

Piston check

Swing check

1 CM4120 Unit Operations Lab Piping Systems Piping Systems in the Chemical Process Industries March,...

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