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CM4120Unit Operations Lab
Piping SystemsPiping Systems in the Chemical
Process IndustriesMarch, 2008 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 SystemsPiping Systems include:
Pipe Flanges Fittings Bolting Gaskets Valves Hangers and supports Insulations, coverings, coatings
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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 SystemsPrimary 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 LeakEvaluate Performance in a Fire Situation
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CM4120Unit Operations Lab
Piping SystemsSecondary 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 LabPiping SystemsPiping System Design Criteria4 areas to consider:
Physical Attributes Loading and Service Conditions Environmental Factors Materials-Related Considerations
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CM4120Unit Operations Lab
Piping SystemsCodes and Standards simplify design,
manufacturing, installation processStandards – 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 LabPiping 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 SystemsASME B31 is the applicable standard
for design of most piping systems in chemical plantsB31.1 – 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 SystemsASME B31.3 – Chemical Plant and
Refinery Piping CodeIncludes:
Process piping in chemical and refinery plantsProcess piping in pharmaceutical and food processingProcess piping in textile and paper plantsBoiler piping
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CM4120Unit Operations Lab
Piping SystemsASME B31.3 covers:
Materials and designFabricationErection and assemblySupportExamination, inspection, and testing
Web reference: www.piping-toolbox.com
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CM4120Unit Operations Lab
Piping SystemsStandard 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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CM4120Unit Operations Lab
Piping SystemsStandard 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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CM4120Unit Operations Lab
Piping SystemsMaterials – 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 SystemsMaterials – 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 SystemsMaterials – 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 SystemsMaterials – 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 SystemsMaterials – 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 SystemsMaterials – Others
GlassConcreteLined or coated
Glass Rubber Cement Teflon Zinc (galvanized pipe)
Double Containment piping systems
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CM4120Unit Operations Lab
Piping SystemsPiping Insulation
Prevent heat loss/ gainPrevent condensation – below ambientPersonnel protection – over 125oFFreeze protection – outdoor cold climatesFire protectionNoise control
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CM4120Unit Operations LabPiping SystemsFiberglass Insulation w/ Asbestos
plastered fitting coverings
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CM4120Unit Operations LabPiping Systems
Metal Jacketedinsulation
covering
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CM4120Unit Operations Lab
Piping SystemsHeat 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 SystemsPiping Supports
Prevent strain at connectionsPrevent sagMust allow for expansion/contractionDesign for wind/snow and ice/earthquakeClearance for plant traffic and equipment
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CM4120Unit Operations LabPiping SystemsResults of inadequate support
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CM4120Unit Operations LabPiping SystemsResults of inadequate support:
Flixborough, EnglandMay, 1974 – Leaking reactor removed from
train of reactors and temporarily replaced with a section of pipe
June, 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 LabPiping SystemsThe Design Process – a three step
approachDesign for Flow Find min. diameter to achieve desired flow
velocityDesign 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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CM4120Unit Operations Lab
Piping SystemsDesign for Flow
Determined by economicsPiping system must provide reliable service
for expected lifeSmallest diameter usually is lowest cost
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CM4120Unit Operations LabPiping SystemsTypical design velocity Rules of
Thumb when sizing piping...Water lines: 5-7 ft/secPump discharge: (d/2 + 4 ft/sec)Pump suction: (1/3 * discharge velocity)Steam: d in 1000 ft/minSlurries: > min. entrainment velocity
d = I.D. of pipe in inchesfrom Rase and Barrow, Project Engineering of Process
Plants, John Wiley, New York, 1957.
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CM4120Unit Operations LabPiping SystemsNext determine wall thickness:
Pressure Integrity Design methodASME B31.3,
APySE
PDtm
2
tm=min. wall thicknessP=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 LabPiping SystemsFinally re-check ID
Select in-line components
Determine insulation, coverings, coatings
Design and locate supports and hangers
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CM4120Unit Operations LabPiping SystemsEffect of Thermal ExpansionExample: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 LabPiping SystemsTemp 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 LabPiping SystemsWhat 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 LabPiping Systemsσ= α *(ΔT)*E
=(6.6x10-6 in/inoF)*(268oF)*(30x106lbf/in2)=53,000 lbf/in2
since σ=F/A, F=σ*Awhere: F=force on end restraints
A=cross sec. area of 2”, sched 40 pipe
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CM4120Unit Operations LabPiping SystemsA=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 SystemsPipe Joints
Threaded Welded Soldered/ Brazed Glued Compression Bell and spigot Upset or expanded
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CM4120Unit Operations LabPiping Systems
Threaded joints
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CM4120Unit Operations LabPiping Systems
Soldered joints
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CM4120Unit Operations LabPiping Systems
Welded joints
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CM4120Unit Operations LabPiping SystemsCompression joints
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CM4120Unit Operations LabPiping SystemsMechanical joints
shown on glass drain piping system
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CM4120Unit Operations Lab
Piping SystemsPipe 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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CM4120Unit Operations LabPiping SystemsFittings for joining 2
sections of pipe:Coupling
Reducing Coupling
Union
Flange
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CM4120Unit Operations LabPiping Systems
Fittings for changing directions in pipe:
45o Ell
90o Ell
Street Ell
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CM4120Unit Operations LabPiping Systems
Fittings for adding a branch in a run of piping:
Tee
Cross
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CM4120Unit Operations LabPiping Systems
Fittings for blocking the end of a run of piping:
Pipe plug
Pipe cap
Blind Flange
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CM4120Unit Operations LabPiping Systems
Misc. pipe fittings:Nipple
Reducing bushing
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CM4120Unit Operations LabPiping Systems
Gate Valve:Used to block
flow (on/off service)
Sliding “gate”on knife-gatevalve
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CM4120Unit Operations LabPiping Systems
Globe Valve:Used to
regulate flow
Cut-away showsstem seal
plug and seat
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CM4120Unit Operations LabPiping Systems
Ball Valve:Typically used
as block valve
“Quarter-turn” valve
Cut-away shows ball and seat
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CM4120Unit Operations LabPiping 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 LabPiping Systems
Check Valves:Used to prevent
backflowPiston check
Swing check
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CM4120Unit Operations LabPiping SystemsReferences:
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, 1998www.flowserve.com, Flowserve Corp., Sept. 2004.www.engineeringtoolbox.com, The Engineering Toolbox, Sept. 2004.