CM4120 Chemical Plant Operations Lab Introduction to Chemical Manufacturing

1CM4120Unit Operations LabPiping SystemsPiping Systems in the Chemical Process IndustriesMarch, 2009IntroductionBasis for DesignPiping Codes and StandardsDesign of Process Piping SystemsJoints and FittingsValves12CM4120Unit Operations LabPiping SystemsPiping Systems include:

Pipe, Flanges, FittingsBolting, GasketsValvesHangers and SupportsInsulations, Coverings, CoatingsHeat Tracing2Everything between equipment and instrumentation is considered piping

3CM4120Unit Operations LabPiping SystemsPiping systems are like arteries and veins. They carry the lifeblood of modern civilization.

Mohinder Nayyar, P.E.Piping Handbook, 7th ed.McGraw-Hill, 20003The invention of piping systems is what allowed civilization to develop beyond small villages.Early records show use of hollow log piping and open-channel water distribution systems by the Egyptians, Romans, and Babylonians.

4CM4120Unit Operations LabPiping SystemsPrimary Design Consideration is SafetyEvaluate Process ConditionsTemperaturePressureChemical compatibility/Corrosion allowancesVibration, flexing, bendingExpansion/Contraction due to temperature changeEnvironmental conditionsEvaluate the Effects of a LeakEvaluate Performance in a Fire Situation4Before starting to design a piping system there are many considerations.Foremost concern in any good design is safety.5CM4120Unit Operations LabPiping SystemsSecondary Considerations

Evaluate any Special RequirementsSanitary requirements CleanabilityServiceability ease of maintenance of equipmentPossible contamination of process fluid by piping materials, sealants, or gasketingEarthquake, Hurricane, Lightening, PermafrostLowest Cost over the Lifetime5Does the system have to be disassembled frequently for maintenance or cleaning?Are there trace elements in the piping, sealants, or gasketing that may contaminate the process fluid or utility?What is the total cost of the piping system over the expected life?6CM4120Unit Operations LabPiping SystemsPiping System Routing and LayoutThe unwritten #1 rule:Serviceability/Operability

UO Lab

67CM4120Unit Operations LabPiping SystemsPiping System Design Criteria

4 areas to consider:Physical AttributesLoading and Service ConditionsEnvironmental FactorsMaterials-Related Considerations

7Physical Attributes:SizeLayoutDimensional limitsOperability (slope for drainage, mechanical fittings for ease of dis-assembly

Loading/Service Conditions:conditions that stress the piping system- internal from process fluids pressure, temperature, T/P cycling- external from wind, ice, service personnel, trafficalso consider load cycling and load durationmust design for all expected combinations/ worst case

Environmental Factors:physical and chemical conditions that deteriorate the system over time- corrosion (internal or external)- erosion- physical damage fork lift operators

Materials-Related Considerations:Strength something like 2/3 of yield strengthToughness- use ductile materials, CS is ductile down to T = 0 F, then reduce P ratingCorrosion resistance negligible over design lifetime, increase wall thickness if necessary- use design temp to determine corrosion rate- will corrosion create process fluid contamination problem?- Special considerations CS is subject to Graphitization when T>775 Ffor long periods (carbon converts to graphite and becomes brittle)Pressure integrity Leak-tight WRT stress/strain in pipe system (not gaskets or seals)8CM4120Unit Operations LabPiping SystemsCodes and Standards simplify design, manufacturing, installation process

Standards provide design criteria for componentsstandard sizes for pipedimensions for fittings or valvesCodes specific design/fabrication methodologiesIncorporated into local/regional statute Its the LAW

8Use commonly accepted methods-- reduce design time-- produce safe design-- limit liability.

9CM4120Unit Operations LabPiping SystemsASME 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.9Many professional and standards associations have developed codes and standard practices for the design, assembly, and testing of process piping.

Depending on which industry segment, which part of the plant, the type of service (drinking water vs. oil pipeline) or the type of construction, you would refer to the appropriate code or standard.

ASME boiler and pressure vessel code and B31 are most relevant to ChEANSI American National Standards InstituteASME American Society of Mechanical EngineersASTM American Society for Testing and MaterialsAPI American Petroleum InstitutePPI Plastic Pipe InstituteAWS American Welding SocietyPFI Pipe Fabrication Institute

10CM4120Unit Operations LabPiping SystemsASME B31 Pertinent sectionsB31.1 Power plant boilersB31.3 Chemical plant and refinery pipingB31.4 Liquid petroleum transportB31.7 Nuclear power plant radioactive fluids

10Within a chemical plant, one section will govern in one part of the plant.In other parts of the plant, a different section may govern the design and installation.

11CM4120Unit Operations LabPiping SystemsASME B31.3 Chemical Plant and Refinery Piping CodeIncludes piping systems in:Chemical and refinery plantsPharmaceutical and food processingTextile and paper plantsBoilers

11Most important for chemical engineers12CM4120Unit Operations LabPiping SystemsASME B31.3 covers:Materials of constructionPiping design processFabrication, Erection, AssemblyDesign of supportsExamination, inspection, and testing

12Need to be familiar with B31.3 if you have plant responsibilities.Code is laid out in sections, starting with scope and definitions and progressing thru design, inspection, and testing.13CM4120Unit Operations LabPiping SystemsPiping Design Process a three step approach

Design for FlowFind min. diameter to achieve desired flow velocityDesign for Pressure IntegrityFind min. wall thickness for process and external conditionsFind appropriate rating of in-line componentsRe-check for Flow Criteria1314CM4120Unit Operations LabPiping SystemsStandard Pipe SizesDiameters are NominalSizes 12 and less, nominal size < ODSizes 14 and over, nominal size = OD

Wall thickness inferred thru Schedule

Defined Schedules:5, 10, 20, 30, 40, 60, 80, 100, 120, 140, 160

14Specs for piping found in ANSI B36.10 and B36.19

Attempt made to manufacture pipe systems to handle classes of allowable working pressure so that all diameters of pipe of the same pressure rating would be compatible.Schedule

Higher the schedule, the thicker the wall, the higher the working pressureThe OD stays the same for all pipe of the same nominal diameterExample: 4 schedule 40 pipeOD = 4.50ID = 4.026

15CM4120Unit Operations LabPiping SystemsStandard Tubing SizesSteel tubingDiameters are Actual ODWall thickness is specifiedRefrigeration TubingSingle wall thickness available for each sizeActual ODCopper Tubing Nominal sizesType K, L, M15Pipe is always round, tubing can be round, oval, or rectangular/squareTubing specifications in ANSI B32.5

Example: Steel tubing4 X 4 OD3 ID

Refrigeration tubing: OD w/ 0.035 wall for 0.680 ID

Copper TubingType K is thickest2 type KOD = 2.125Wall = 0.083ID = 1.95916CM4120Unit Operations LabPiping SystemsCriteria for Design for Flow

EconomicsServiceable over Design LifeSmallest diameter usually is lowest costPerformanceMinimum entrainment velocityPrevent erosion or cavitation16First step is to determine appropriate flow velocity for each piping segment.Find minimum pipe ID to attain the velocity.Select the next largest available size of Standard Weight pipe.

17CM4120Unit Operations LabPiping SystemsDesign 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, 1991.17Reduce pumping lossesMinimize noise levelsSlurries need to keep solids entrained and prevent sedimentationPump suction lines need to minimize head loss in suction piping so that fluid doesnt vaporize in/at pump

18CM4120Unit Operations LabPiping SystemsSelecting appropriate pipe ScheduleSchedule = P/S * 1000P = 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?

18Ballpark estimate useful for costingStill need to check actual wall stress at process conditions.19CM4120Unit Operations LabPiping SystemsDetermine min. reqd wall thickness:Pressure Integrity Design MethodASME B31.3,

tm=min. wall thicknessP=design pressure, psigD=O.D. of pipe, in.S=allowable stress, psiE=weld joint efficiencyy=factor to adjust for tempA= addl thickness for corrosion, external loads, etc.19ASME B31.3 uses Pressure-Integrity design method for determining the min. wall thickness.

All design factors are included in the appropriate code.Need to reduce pressure ratings for high-low tempNeed to add matl for corrosion/erosion allowanceNeed to add matl for external loadsNeed to add material for threading, grooving, other material removal process

20CM4120Unit Operations LabPiping SystemsAfter determining wall thickness:Re-check ID for velocity;

Select in-line components;

Determine insulation, coverings, coatings;

Design and locate supports and hangers.

20Heavy wall pipe may have reduced the ID below the min allowable based on flow velocity criteria.

21CM4120Unit Operations LabPiping SystemsInline Components:FittingsValvesGaskets, Seals, and Thread SealantsConnection Hardware Bolts, studs, nuts, washers2122CM4120Unit Operations LabPiping SystemsPipe Fittings - SteelForgedCastMalleable Iron

Select Class of Fittings150 lb., 300 lb., 600 lb., etc.Need a look-up table to determine max. allowable P at the design temperature22Used to connect or adapt pipe to other pipe or equipment.Used to change directions.Used to change pipe diameter or terminate a pipe run.Forged Steel in threaded or socket weldCast Iron, bronze, brass Malleable Iron generally in threaded23CM4120Unit Operations LabPiping SystemsMaximum Allowable non-shock Pressure (psig)Temperature(oF)Pressure Class Rating for Flanged Fittings (lb)15030040060090015002500Hydrostatic Test Pressure (psig)450112515002225335055759275-20 to 10028574099014802220370561702002606759001350202533755625300230655875131519703280547040020063584512701900317052805001706008001200179529954990600140550730109516402735456065012553571510751610268544757001105357101065160026654440750955056701010151025204200800804105508251235206034308506527035553580513402230900501702303455158601430950351051402053105158601000205070105155260430Ratings for flanged steel pipe fittings, ANSI B16.5 - 1988.http://www.engineeringtoolbox.com/ansi-flanges-pressure-temperature-d_342.html23Select appropriate class, check for availability

Look for special conditions like need for long radius ells or clean-outs.24CM4120Unit Operations LabPiping SystemsDesign Checklist:Re-check ID for velocity;

Select in-line components;

Determine insulation, coverings, coatings;

Design and locate supports and hangers.

2425CM4120Unit Operations LabPiping SystemsPiping Insulation

Prevent heat loss/ gainPrevent condensation below ambientPersonnel protection over 125oFFreeze protection outdoor cold climatesFire protectionNoise control25Insulating material and covering systemIf the pipe is exposed to washdown or is installed outdoors, need to consider the effects of water on insulating material.Must consider:physical abuse of insulating systemlocation of supportsproximity to adjacent runs of pipeconnections to equipment, valves, and instrumentationMost insulating systems also include a protective covering of cloth, metal, or plastic.26CM4120Unit Operations LabPiping SystemsRecommended minimum Thickness of Insulation (inches)*Nominal Pipe SizeNPS(inches)Temperature Range (oC)50 - 9090 - 120120 - 150150 - 230Temperature Range (oF)120 - 200201 - 250251 - 305306 - 450Hot WaterLow Pressure SteamMedium Pressure SteamHigh Pressure Steam< 1"1.01.52.02.51 1/4" - 2"1.01.52.52.52 1/2" - 4"1.52.02.53.05" - 6"1.52.03.03.5> 8"1.52.03.03.5* 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, 3-26-20092627CM4120Unit Operations LabPiping SystemsCommon Types of Insulation

Mineral FiberFiberglasRock woolCellular glass(Asbestos or Asbestos-containing)Polymeric closed cell foamsFlexible polyethyleneRigid foam polystyrene, polyurethanes

2728CM4120Unit Operations LabPiping SystemsFiberglass Insulation w/ Asbestos-plastered fitting coverings

28Plaster of Asbestos was hand-formed around each fittingOften these systems were cloth covered.29CM4120Unit Operations LabPiping SystemsMetal Jacketedinsulation covering

29Jacketing can be aluminum, galvanized steel or stainless steel.This is embossed aluminum indoor application.

Also pre-formed plastic is available.30CM4120Unit Operations LabPiping SystemsAfter determining wall thickness:Re-check ID for velocity;

Select in-line components;

Determine insulation, coverings, coatings;

Design and locate supports and hangers.

30

31CM4120Unit Operations LabPiping SystemsPiping Supports

3132CM4120Unit Operations LabPiping SystemsSupports

Prevent strain at connectionsPrevent sagAllow for expansion/contractionDesign for wind, snow/ice, earthquakeProvide clearance for plant traffic/equipment32Determining max. space between supports is part of design process.

33CM4120Unit Operations LabPiping SystemsSteel Pipe - Distance between Supports (ft)Outside Diameter (in)Horizontal RunVertical Run1/24.5103/47.51017.5101 1/47.5121 1/27.51227.5152 1/210153101541018Source: Engineering Toolbox, http://www.engineeringtoolbox.com/steel-pipe-supports-d_1071.html, 2-26-093334CM4120Unit Operations LabPiping SystemsInadequate support

35CM4120Unit Operations LabPiping SystemsEffect of Thermal Expansion on piping and supportsExample 1:Calculate the expansion per 20 length of 2, schedule 40 carbon steel steam line at boiler startup for a 100 psig steam service.=thermal expansion coefficientfor mild steel, =6.6x10-6 in/inoF

36CM4120Unit Operations LabPiping SystemsTemp of pipe at amb. cond. =70oFTemp of 100 psig sat. steam =338oFT=268oFL=20=240expansion due to temperatureincrease is *L* T=(6.6x10-6in/inoF)*(240in)*(268oF)=0.42 in per 20 of pipe37CM4120Unit Operations LabPiping SystemsExample 2:What force is exerted on the end restraints of that 20 pipe if it is rigidly installed (end restraints cant move)?=internal stress due to T, and = *(T)*EE is the material property called Modulus of Elasticity, relationship between stress and strainE=30x106 psi for low carbon steel

38CM4120Unit Operations LabPiping Systems= *(T)*E=(6.6x10-6 in/inoF)*(268oF)*(30x106lbf/in2)=53,000 lbf/in2

since =F/A,The force on the end restraints is F=*Awhere:F=force in lbfA=cross sec. area of 2, sched 40 pipe in sq. inches39CM4120Unit Operations LabPiping SystemsA=(OD2-ID2)/4= (2.3752-2.0672)/4=1.07 sq.in

F= *A=(53,000 lbf/in2)*(1.07 in2)Force on the end restraints = 57,000 lbfor 28.5 tons

40CM4120Unit Operations LabPiping SystemsResults 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

20 inch pipe ruptured, possibly due to fire in an adjacent 8 pipe that had been burning for an hour40 metric tons of cyclohexane vaporized and explodedFires continued to burn for 10 daysExplosion occurred on a Saturday or an additional 500 workers would have been killed

The official inquiry into the accident determined that the bypass pipe had failed due to unforeseen lateral stresses in the pipe during a pressure surge. The bypass had been designed by engineers who were not experienced in high-pressure piping design, no plans or calculations had been produced, the pipe was not pressure-tested, and was mounted on temporary scaffolding poles that allowed the pipe to twist under pressure. It should be noted that the by-pass pipe was a smaller diameter (20") than the reactor flanges (24") and in order to align the flanges, short sections of steel bellows were added at each end of the by-pass - under pressure such bellows tend to squirm or twist.Further investigation led to new theories in 2000. The test results released in November 2000 seemed to back up Mr Ralph King's theory that the presence of water inside the reactors and the simultaneous shutting down of crucial equipment, generated a massive build-up of pressure that blew the valve apart.Source: Flixborough Disaster, Wikipedia, 3/18/2009

4041CM4120Unit Operations LabPiping SystemsHeat Tracing

4142CM4120Unit Operations LabPiping SystemsHeat Tracing

Prevents flow problems in cold climatesFreeze protectionLoss of flow due to viscosity increasePrevent condensation in vapor linesMethodsElectricHot Fluids42Heat tape or pipe runs along side of process pipe.Induction heating of the pipe can also be used.Steam is most common fluid.Glycols in a recirculating system.Insulation covers the pipe and heat tracing.

43CM4120Unit Operations LabPiping SystemsReferences: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. 2004.44CM4120Unit Operations LabPiping SystemsMaterials Metallic piping

Carbon and low alloy steelDuctileInexpensive and availableEasy to machine, weld, cutSome drawbacks44Can be cut, welded or threaded, and assembled using commonly available skilled labor

Subject to Embrittlement failurescausticshigh pressure steamConversion of carbides to graphiteexposure to high temp over timeSubject to hydrogen stress cracking

45CM4120Unit Operations LabPiping SystemsMaterials Metallic piping

Alloy Steels including Stainless SteelsGood corrosion resistanceMore difficult to machine, weld, cutSome drawbacks

45Requires special welding techniquesHarder to cut, thread and machineStress corrosion failuresexposure to chloridesEmbrittlement failureAfter exposure to high temp (welding without annealing)46CM4120Unit Operations LabPiping SystemsMaterials Metallic piping

Nickel, Titanium, Copper, etc.Copper is used in residential and commercial applications and is widely availableOther materials are expensive and difficult to machine, weld, joinSome incompatibilities with each

4647CM4120Unit Operations LabPiping SystemsMaterials Non-Metallic piping

ThermoplasticsWide range of chemical compatibilityLight weightEasily cut and joinedLow temperature limitsNeed extra supports48CM4120Unit Operations LabPiping SystemsMaterials Non-Metallic piping

Fiberglass Reinforced PipeWide range of chemical compatibilityEasily cut and joinedWider temperature limits than thermoplasticsThermal expansion similar to carbon steelSimilar structural performance as carbon steel

49CM4120Unit Operations LabPiping SystemsMaterials Others

GlassConcreteLined or coatedGlassRubberCementTeflonZinc (galvanized pipe)Double Containment piping systems49Used for low cost, corrosion resistance, long life, ease of cleaningLined pipe is chemical resistant inner layer with structural outer layer50CM4120Unit Operations LabPiping SystemsPipe Joints

ThreadedWeldedSoldered/ BrazedGluedCompressionBell and spigotUpset or expanded

50Most common are threaded and weldedThreaded up to 2Welded butt welded or socket weldedUpset for thin wall pipe and tubing

51CM4120Unit Operations LabPiping SystemsThreaded joints

52CM4120Unit Operations LabPiping SystemsSoldered joints

53CM4120Unit Operations LabPiping SystemsWelded joints

54CM4120Unit Operations LabPiping SystemsCompression joints

55CM4120Unit Operations LabPiping SystemsMechanical jointsshown on glass drain piping system

56CM4120Unit Operations LabPiping SystemsFittings for joining 2 sections of pipe:

Coupling

Reducing Coupling

Union

Flange

56Couplings join two lengths of pipe

Reducing couplings used for joining two lengths of pipe of different diameters. Can be concentric or eccentric.

Unions and flanges are used when piping must be dis-assembled57CM4120Unit Operations LabPiping SystemsFittings for changing directions in pipe:

45o Ell

90o Ell

Street Ell

57Both short and long-radius fittings available

58CM4120Unit Operations LabPiping SystemsFittings for adding a branch in a run of piping:

Tee

Cross

5859CM4120Unit Operations LabPiping SystemsFittings for blocking the end of a run of piping:

Pipe plug

Pipe cap

Blind Flange

59Caps, plugs, and blind flanges are used to block off the end of a pipe60CM4120Unit Operations LabPiping SystemsMisc. pipe fittings:

Nipple

Reducing bushing

60Nipples lengths up to 12 inch standard, other lengths available

Reducing bushings are typically used to reduce the size of a tank or vessel fitting to the size of the pipe run.Not normally used as in-line fittings.61CM4120Unit Operations LabPiping SystemsGate Valve:Used to block flow (on/off service)

Sliding gateon knife-gatevalve

6162

CM4120Unit Operations LabPiping SystemsGlobe Valve:Used to regulate flow

Cut-away showsstem seal plug and seat

6263

CM4120Unit Operations LabPiping SystemsBall Valve:Typically used as block valve

Quarter-turn valve

Cut-away shows ball and seat

6364CM4120Unit Operations LabPiping SystemsButterfly Valve:Can be used for flow control or on/off

Valve actuator/ positioner for accurate flow control

6465CM4120Unit Operations LabPiping SystemsCheck Valves:Used to prevent backflow

Piston check

Swing check

65