CM4120 Unit Operations Lab Piping Systems Piping Systems in the Chemical Process Industries March, 2009 Introduction Basis for Design Piping Codes and Standards Design of Process Piping Systems Joints and Fittings Valves

CM4120 Unit Operations Lab Piping Systems Piping Systems include: Pipe, Flanges, Fittings Bolting, Gaskets Valves Hangers and Supports Insulations, Coverings, Coatings Heat Tracing Everything between equipment and instrumentation is considered piping

CM4120 Unit 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 The 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.

CM4120 Unit Operations Lab Piping 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 Before starting to design a piping system there are many considerations. Foremost concern in any good design is safety.

CM4120 Unit 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 Does 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?

CM4120 Unit Operations Lab Piping Systems Piping System Routing and Layout The unwritten #1 rule: Serviceability/Operability UO Lab

CM4120 Unit Operations Lab Piping Systems Piping System Design Criteria 4 areas to consider: Physical Attributes Loading and Service Conditions Environmental Factors Materials-Related Considerations Physical Attributes: Size Layout Dimensional limits Operability (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, traffic also consider load cycling and load duration must 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 strength Toughness - use ductile materials, CS is ductile down to T = 0 F, then reduce P rating Corrosion 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 F for long periods (carbon converts to graphite and becomes brittle) Pressure integrity – Leak-tight WRT stress/strain in pipe system (not gaskets or seals)

CM4120 Unit 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 Use commonly accepted methods -- reduce design time -- produce safe design -- limit liability.

CM4120 Unit Operations Lab Piping 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. Many 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 ChE ANSI – American National Standards Institute ASME – American Society of Mechanical Engineers ASTM – American Society for Testing and Materials API – American Petroleum Institute PPI – Plastic Pipe Institute AWS – American Welding Society PFI – Pipe Fabrication Institute

CM4120 Unit Operations Lab Piping Systems ASME B31 Pertinent sections B31.1 – Power plant boilers B31.3 – Chemical plant and refinery piping B31.4 – Liquid petroleum transport B31.7 – Nuclear power plant radioactive fluids Within 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.

CM4120 Unit Operations Lab Piping Systems ASME B31.3 – Chemical Plant and Refinery Piping Code Includes piping systems in: Chemical and refinery plants Pharmaceutical and food processing Textile and paper plants Boilers Most important for chemical engineers

CM4120 Unit Operations Lab Piping Systems ASME B31.3 covers: Materials of construction Piping design process Fabrication, Erection, Assembly Design of supports Examination, inspection, and testing Need 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.

CM4120 Unit Operations Lab Piping Systems Piping 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 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” Defined Schedules: 5, 10, 20, 30, 40, 60, 80, 100, 120, 140, 160 Specs 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 pressure The OD stays the same for all pipe of the same nominal diameter Example: 4” schedule 40 pipe OD = 4.50” ID = 4.026”

CM4120 Unit Operations Lab Piping 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 Pipe is always round, tubing can be round, oval, or rectangular/square Tubing specifications in ANSI B32.5 Example: Steel tubing 4” X ¼” 4” OD 3 ½” ID Refrigeration tubing: ¾” ¾” OD w/ 0.035” wall for 0.680” ID Copper Tubing Type K is thickest 2” type K OD = 2.125” Wall = 0.083” ID = 1.959”

CM4120 Unit Operations Lab Piping Systems Criteria for Design for Flow Economics Serviceable over Design Life Smallest diameter usually is lowest cost Performance Minimum entrainment velocity Prevent erosion or cavitation First 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.

CM4120 Unit Operations Lab Piping Systems Design Rules of Thumb when sizing for velocity... Water lines: 3-10 ft/sec Pump discharge: 3-12 ft/sec Pump suction: (1/3 x discharge velocity) Steam: low pressure (25 psig or less) 50-100 ft/sec high pressure (>100 psig) 100-200 ft/sec Slurries: > min. entrainment velocity from Peters and Timmerhaus, Plant Design and Economics for Chemical Engineers, 4th ed., McGraw-Hill, 1991. Reduce pumping losses Minimize noise levels Slurries – need to keep solids entrained and prevent sedimentation Pump suction lines – need to minimize head loss in suction piping so that fluid doesn’t vaporize in/at pump

CM4120 Unit Operations Lab Piping Systems Selecting appropriate pipe Schedule Schedule = P/S * 1000 P = max. working pressure of pipe, psig S = allowable stress in piping material, psi For carbon steel pipe, S = 36,000 psi What is max. working pressure for Schedule 40 Carbon Steel pipe? Ballpark estimate useful for costing Still need to check actual wall stress at process conditions.

CM4120 Unit Operations Lab Piping Systems Determine min. req’d wall thickness: Pressure Integrity Design Method ASME B31.3, ASME 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 temp Need to add mat’l for corrosion/erosion allowance Need to add mat’l for external loads Need to add material for threading, grooving, other material removal process tm=min. wall thickness P=design pressure, psig D=O.D. of pipe, in. S=allowable stress, psi E=weld joint efficiency y=factor to adjust for temp A= add’l thickness for corrosion, external loads, etc.

CM4120 Unit 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. Heavy wall pipe may have reduced the ID below the min allowable based on flow velocity criteria.

CM4120 Unit Operations Lab Piping Systems Inline Components: Fittings Valves Gaskets, Seals, and Thread Sealants Connection Hardware – Bolts, studs, nuts, washers

CM4120 Unit 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 Used 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 weld Cast Iron, bronze, brass Malleable Iron generally in threaded

CM4120 Unit Operations Lab Piping Systems Ratings for flanged steel pipe fittings, ANSI B16.5 - 1988. 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 2225 3350 5575 9275 -20 to 100 285 740 990 1480 2220 3705 6170 200 260 675 1350 2025 3375 5625 230 655 875 1315 1970 3280 5470 635 845 1270 1900 3170 5280 500 170 800 1200 1795 2995 4990 140 550 730 1095 1640 2735 4560 650 125 535 715 1075 1610 2685 4475 700 110 710 1065 1600 2665 4440 750 95 505 670 1010 1510 2520 4200 80 410 825 1235 2060 3430 850 65 270 355 805 1340 2230 50 345 515 860 1430 950 35 105 205 310 1000 20 70 155 430 Select appropriate class, check for availability Look for special conditions like need for long radius ells or clean-outs. http://www.engineeringtoolbox.com/ansi-flanges-pressure-temperature-d_342.html

CM4120 Unit 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.

CM4120 Unit Operations Lab Piping Systems Piping Insulation Prevent heat loss/ gain Prevent condensation – below ambient Personnel protection – over 125oF Freeze protection – outdoor cold climates Fire protection Noise control Insulating material and covering system If 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 system location of supports proximity to adjacent runs of pipe connections to equipment, valves, and instrumentation Most insulating systems also include a protective covering of cloth, metal, or plastic.

CM4120 Unit Operations Lab Piping Systems Recommended minimum Thickness of Insulation (inches)* Nominal Pipe Size NPS (inches) Temperature Range (oC) 50 - 90 90 - 120 120 - 150 150 - 230 Temperature Range (oF) 120 - 200 201 - 250 251 - 305 306 - 450 Hot Water Low Pressure Steam Medium Pressure Steam High Pressure Steam < 1" 1.0 1.5 2.0 2.5 1 1/4" - 2" 2 1/2" - 4" 3.0 5" - 6" 3.5 > 8" * based on insulation with thermal resistivity in the range 4 - 4.6 ft2 hr oF/ Btu in Source: Engineering Toolbox, http://www.engineeringtoolbox.com/pipes-insulation-thickness-d_16.html, 3-26-2009

CM4120 Unit 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

CM4120 Unit Operations Lab Piping Systems Fiberglass Insulation w/ Asbestos-plastered fitting coverings Plaster of Asbestos was hand-formed around each fitting Often these systems were cloth covered.

CM4120 Unit Operations Lab Piping Systems Metal Jacketed insulation covering Jacketing can be aluminum, galvanized steel or stainless steel. This is embossed aluminum – indoor application. Also pre-formed plastic is available.

CM4120 Unit 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.

CM4120 Unit Operations Lab Piping Systems Piping Supports

CM4120 Unit Operations Lab Piping Systems Supports Prevent strain at connections Prevent sag Allow for expansion/contraction Design for wind, snow/ice, earthquake Provide clearance for plant traffic/equipment Determining max. space between supports is part of design process.

CM4120 Unit 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 1 1 1/4 12 1 1/2 2 15 2 1/2 3 4 18 Source: Engineering Toolbox, http://www.engineeringtoolbox.com/steel-pipe-supports-d_1071.html, 2-26-09

CM4120 Unit Operations Lab Piping Systems Inadequate support

CM4120 Unit 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 coefficient for mild steel, α =6.6x10-6 in/inoF

CM4120 Unit Operations Lab Piping 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 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

CM4120 Unit Operations Lab Piping Systems =(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*A where: F=force in lbf A=cross sec. area of 2”, sched 40 pipe in sq. inches

CM4120 Unit 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

CM4120 Unit 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 breaks 28 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 hour 40 metric tons of cyclohexane vaporized and exploded Fires continued to burn for 10 days Explosion 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

CM4120 Unit Operations Lab Piping Systems Heat Tracing

CM4120 Unit 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 lines Methods Electric Hot Fluids Heat 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.

CM4120 Unit 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, 1998 www.flowserve.com, Flowserve Corp., Sept. 2004. www.engineeringtoolbox.com, The Engineering Toolbox, Sept. 2004.

CM4120 Unit Operations Lab Piping Systems Materials – Metallic piping Carbon and low alloy steel Ductile Inexpensive and available Easy to machine, weld, cut Some drawbacks Can be cut, welded or threaded, and assembled using commonly available skilled labor Subject to Embrittlement failures caustics high pressure steam Conversion of carbides to graphite exposure to high temp over time Subject to hydrogen stress cracking

CM4120 Unit Operations Lab Piping Systems Materials – Metallic piping Alloy Steels including “Stainless Steels” Good corrosion resistance More difficult to machine, weld, cut Some drawbacks Requires special welding techniques Harder to cut, thread and machine Stress corrosion failures exposure to chlorides Embrittlement failure After exposure to high temp (welding without annealing)

CM4120 Unit 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

CM4120 Unit 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

CM4120 Unit 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

CM4120 Unit Operations Lab Piping Systems Materials – Others Glass Concrete Lined or coated Rubber Cement Teflon Zinc (galvanized pipe) Double Containment piping systems Used for low cost, corrosion resistance, long life, ease of cleaning Lined pipe is chemical resistant inner layer with structural outer layer

CM4120 Unit Operations Lab Piping Systems Pipe Joints Threaded Welded Soldered/ Brazed Glued Compression Bell and spigot Upset or expanded Most common are threaded and welded Threaded – up to 2” Welded – butt welded or socket welded Upset – for thin wall pipe and tubing

CM4120 Unit Operations Lab Piping Systems Threaded joints

CM4120 Unit Operations Lab Piping Systems Soldered joints

CM4120 Unit Operations Lab Piping Systems Welded joints

CM4120 Unit Operations Lab Piping Systems Compression joints

CM4120 Unit Operations Lab Piping Systems Mechanical joints shown on glass drain piping system

CM4120 Unit Operations Lab Piping Systems Fittings for joining 2 sections of pipe: Coupling Reducing Coupling Union Flange Couplings 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-assembled

CM4120 Unit Operations Lab Piping Systems Fittings for changing directions in pipe: 45o Ell 90o Ell Street Ell Both short and long-radius fittings available

CM4120 Unit Operations Lab Piping Systems Fittings for adding a branch in a run of piping: Tee Cross

CM4120 Unit Operations Lab Piping Systems Fittings for blocking the end of a run of piping: Pipe plug Pipe cap Blind Flange Caps, plugs, and blind flanges are used to block off the end of a pipe

CM4120 Unit Operations Lab Piping Systems Misc. pipe fittings: Nipple Reducing bushing Nipples 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.

CM4120 Unit Operations Lab Piping Systems Gate Valve: Used to block flow (on/off service) Sliding “gate” on knife-gate valve

CM4120 Unit Operations Lab Piping Systems Globe Valve: Used to regulate flow Cut-away shows stem seal plug and seat

CM4120 Unit Operations Lab Piping Systems Ball Valve: Typically used as block valve “Quarter-turn” valve Cut-away shows ball and seat

CM4120 Unit Operations Lab Piping Systems Butterfly Valve: Can be used for flow control or on/off Valve actuator/ positioner for accurate flow control

CM4120 Unit Operations Lab Piping Systems Check Valves: Used to prevent backflow Piston check Swing check