CM4120 Unit Operations Lab Piping Systems

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping Systems Piping Systems include: • Pipe, Flanges, Fittings • Bolting, Gaskets • Valves • Hangers and Supports • Insulations, Coverings, Coatings • Heat Tracing

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping Systems Piping System Routing and Layout The unwritten #1 rule: Serviceability/Operability UO Lab

CM4120Unit Operations LabPiping Systems Piping System Design Criteria 4 areas to consider: • Physical Attributes • Loading and Service Conditions • Environmental Factors • Materials-Related Considerations

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping 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.

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping Systems ASME B31.3 covers: • Materials of construction • Piping design process • Fabrication, Erection, Assembly • Design of supports • Examination, inspection, and testing

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping 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.

CM4120Unit Operations LabPiping 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?

CM4120Unit Operations LabPiping Systems Determine min. req’d wall thickness: Pressure Integrity Design Method ASME B31.3, E=weld joint efficiency y=factor to adjust for temp A= add’l thickness for corrosion, external loads, etc. tm=min. wall thickness P=design pressure, psig D=O.D. of pipe, in. S=allowable stress, psi

CM4120Unit Operations LabPiping Systems After determining wall thickness: Re-check ID for velocity; Select in-line components; Determine insulation, coverings, coatings; Design and locate supports and hangers.

CM4120Unit Operations LabPiping Systems Inline Components: Fittings Valves Gaskets, Seals, and Thread Sealants Connection Hardware – Bolts, studs, nuts, washers

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping Systems Ratings for flanged steel pipe fittings, ANSI B16.5 - 1988. http://www.engineeringtoolbox.com/ansi-flanges-pressure-temperature-d_342.html

CM4120Unit Operations LabPiping Systems Design Checklist: Re-check ID for velocity; Select in-line components; Determine insulation, coverings, coatings; Design and locate supports and hangers.

CM4120Unit Operations LabPiping Systems Piping Insulation • Prevent heat loss/ gain • Prevent condensation – below ambient • Personnel protection – over 125oF • Freeze protection – outdoor cold climates • Fire protection • Noise control

CM4120Unit Operations LabPiping Systems * 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

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping Systems Fiberglass Insulation w/ Asbestos-plastered fitting coverings

CM4120Unit Operations LabPiping Systems Metal Jacketed insulation covering

CM4120Unit Operations LabPiping Systems After determining wall thickness: Re-check ID for velocity; Select in-line components; Determine insulation, coverings, coatings; Design and locate supports and hangers.

CM4120Unit Operations LabPiping Systems Piping Supports

CM4120Unit Operations LabPiping Systems Supports • Prevent strain at connections • Prevent sag • Allow for expansion/contraction • Design for wind, snow/ice, earthquake • Provide clearance for plant traffic/equipment

CM4120Unit Operations LabPiping Systems Source: Engineering Toolbox, http://www.engineeringtoolbox.com/steel-pipe-supports-d_1071.html, 2-26-09

CM4120Unit Operations LabPiping Systems Inadequate support

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping 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*A where: F=force in lbf A=cross sec. area of 2”, sched 40 pipe in sq. inches

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping Systems Heat Tracing

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping 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.

CM4120Unit Operations LabPiping Systems Materials – Metallic piping Carbon and low alloy steel • Ductile • Inexpensive and available • Easy to machine, weld, cut • Some drawbacks

CM4120Unit Operations LabPiping Systems Materials – Metallic piping Alloy Steels including “Stainless Steels” • Good corrosion resistance • More difficult to machine, weld, cut • Some drawbacks

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping Systems Materials – Non-Metallic piping Thermoplastics • Wide range of chemical compatibility • Light weight • Easily cut and joined • Low temperature limits • Need extra supports

CM4120Unit Operations LabPiping 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

CM4120Unit Operations LabPiping Systems Materials – Others Glass Concrete Lined or coated • Glass • Rubber • Cement • Teflon • Zinc (galvanized pipe) Double Containment piping systems

CM4120Unit Operations LabPiping Systems Pipe Joints • Threaded • Welded • Soldered/ Brazed • Glued • Compression • Bell and spigot • Upset or expanded

CM4120 Unit Operations Lab Piping Systems