Post on 11-Dec-2015
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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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CM4120Unit 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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CM4120Unit 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
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CM4120Unit Operations Lab
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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CM4120Unit 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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CM4120Unit Operations Lab
Piping Systems
Piping System Routing and LayoutThe unwritten #1 rule:
Serviceability/Operability
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CM4120Unit 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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CM4120Unit 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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CM4120Unit Operations Lab
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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CM4120Unit Operations Lab
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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CM4120Unit Operations Lab
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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CM4120Unit Operations Lab
Piping Systems
ASME B31.3 covers:Materials of constructionPiping design processFabrication, Erection, AssemblyDesign of supportsExamination, inspection, and testing
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CM4120Unit 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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CM4120Unit Operations Lab
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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CM4120Unit Operations Lab
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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CM4120Unit Operations Lab
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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CM4120Unit Operations Lab
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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CM4120Unit Operations Lab
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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CM4120Unit Operations Lab
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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CM4120Unit 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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CM4120Unit Operations Lab
Piping Systems
Inline Components:FittingsValvesGaskets, Seals, and Thread SealantsConnection Hardware – Bolts, studs,
nuts, washers
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CM4120Unit 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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CM4120Unit Operations Lab
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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CM4120Unit 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.
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CM4120Unit Operations Lab
Piping Systems
Piping Insulation
Prevent heat loss/ gainPrevent condensation – below ambientPersonnel protection – over 125oFFreeze protection – outdoor cold climatesFire protectionNoise control
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CM4120Unit Operations Lab
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
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CM4120Unit 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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CM4120Unit Operations Lab
Piping Systems
Fiberglass Insulation w/ Asbestos-plastered fitting coverings
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CM4120Unit Operations Lab
Piping Systems
Metal Jacketedinsulation
covering
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CM4120Unit 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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CM4120Unit Operations Lab
Piping Systems
Piping Supports
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CM4120Unit Operations Lab
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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CM4120Unit 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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CM4120Unit Operations Lab
Piping Systems
Inadequate support
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CM4120Unit 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 coefficientfor mild steel, α =6.6x10-6 in/inoF
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CM4120Unit Operations Lab
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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CM4120Unit 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 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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CM4120Unit Operations Lab
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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CM4120Unit Operations Lab
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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CM4120Unit 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 breaks28 dead, 89 injured, 1800 houses damaged, 160 shops and factories damaged, large crater where plant stood
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CM4120Unit Operations Lab
Piping Systems
Heat Tracing
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CM4120Unit 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 linesMethods Electric Hot Fluids
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CM4120Unit Operations Lab
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.
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CM4120Unit 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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CM4120Unit 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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CM4120Unit 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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CM4120Unit 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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CM4120Unit 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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CM4120Unit Operations Lab
Piping Systems
Materials – OthersGlassConcreteLined or coated
Glass Rubber Cement Teflon Zinc (galvanized pipe)
Double Containment piping systems
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CM4120Unit Operations Lab
Piping Systems
Pipe Joints Threaded Welded Soldered/ Brazed Glued Compression Bell and spigot Upset or expanded
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CM4120Unit Operations Lab
Piping Systems
Threaded joints
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CM4120Unit Operations Lab
Piping Systems
Soldered joints
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CM4120Unit Operations Lab
Piping Systems
Welded joints
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CM4120Unit Operations Lab
Piping Systems
Compression joints
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CM4120Unit Operations Lab
Piping Systems
Mechanical jointsshown on glass drain piping system
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CM4120Unit Operations Lab
Piping Systems
Fittings for joining 2 sections of pipe:
Coupling
Reducing Coupling
Union
Flange
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CM4120Unit Operations Lab
Piping Systems
Fittings for changing directions in pipe:
45o Ell
90o Ell
Street Ell
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CM4120Unit Operations Lab
Piping Systems
Fittings for adding a branch in a run of piping:
Tee
Cross
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CM4120Unit Operations Lab
Piping Systems
Fittings for blocking the end of a run of piping:
Pipe plug
Pipe cap
Blind Flange
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CM4120Unit Operations Lab
Piping Systems
Misc. pipe fittings:
Nipple
Reducing bushing
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CM4120Unit Operations Lab
Piping Systems
Gate Valve:Used to block
flow (on/off service)
Sliding “gate”on knife-gatevalve
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CM4120Unit Operations Lab
Piping Systems
Globe Valve:Used to
regulate flow
Cut-away showsstem seal
plug and seat
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CM4120Unit Operations Lab
Piping Systems
Ball Valve:Typically used
as block valve
“Quarter-turn” valve
Cut-away shows ball and seat
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CM4120Unit 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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CM4120Unit Operations Lab
Piping Systems
Check Valves:Used to prevent
backflow
Piston check
Swing check