CM4120 Unit Operations Lab Piping Systems

CM4120Unit Operations LabPiping Systems Piping Systems in the Chemical Process Industries March, 2008 • 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

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 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 is the applicable standard for design of most piping systems in chemical plants • 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: • Process piping in chemical and refinery plants • Process piping in pharmaceutical and food processing • Process piping in textile and paper plants • Boiler piping

CM4120Unit Operations LabPiping Systems ASME B31.3 covers: • Materials and design • Fabrication • Erection and assembly • Support • Examination, inspection, and testing Web reference: www.piping-toolbox.com

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” • Schedule = P/S * 1000 • 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 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 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 Fiberglass Insulation w/ Asbestos plastered fitting coverings

CM4120Unit Operations LabPiping Systems Metal Jacketed insulation covering

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 Piping Supports • Prevent strain at connections • Prevent sag • Must allow for expansion/contraction • Design for wind/snow and ice/earthquake • Clearance for plant traffic and equipment

CM4120Unit Operations LabPiping Systems Results of inadequate support

CM4120Unit Operations LabPiping Systems Results of inadequate support: Flixborough, England May, 1974 – Leaking reactor removed from train of reactors and temporarily replaced with a section of pipe June, 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 The 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 Design for Flow • Determined by economics Piping system must provide reliable service for expected life Smallest diameter usually is lowest cost

CM4120Unit Operations LabPiping Systems Typical design velocity Rules of Thumb when sizing piping... Water lines: 5-7 ft/sec Pump discharge: (d/2 + 4 ft/sec) Pump suction: (1/3 * discharge velocity) Steam: d in 1000 ft/min Slurries: > min. entrainment velocity d = I.D. of pipe in inches from Rase and Barrow, Project Engineering of Process Plants, John Wiley, New York, 1957.

CM4120Unit Operations LabPiping Systems Next determine 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 Finally re-check ID Select in-line components Determine insulation, coverings, coatings Design and locate supports and hangers

CM4120Unit Operations LabPiping Systems Effect of Thermal Expansion Example: 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 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, F=σ*A where: F=force on end restraints A=cross sec. area of 2”, sched 40 pipe

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

CM4120Unit Operations LabPiping Systems Threaded joints

CM4120Unit Operations LabPiping Systems Soldered joints

CM4120Unit Operations LabPiping Systems Welded joints

CM4120Unit Operations LabPiping Systems Compression joints

CM4120Unit Operations LabPiping Systems Mechanical joints shown on glass drain piping system

CM4120Unit Operations LabPiping Systems Pipe 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

CM4120Unit Operations LabPiping Systems Fittings for joining 2 sections of pipe: Coupling Reducing Coupling Union Flange

CM4120Unit Operations LabPiping Systems Fittings for changing directions in pipe: 45o Ell 90o Ell Street Ell

CM4120Unit Operations LabPiping Systems Fittings for adding a branch in a run of piping: Tee Cross

CM4120Unit Operations LabPiping Systems Fittings for blocking the end of a run of piping: Pipe plug Pipe cap Blind Flange

CM4120Unit Operations LabPiping Systems Misc. pipe fittings: Nipple Reducing bushing

CM4120Unit Operations LabPiping Systems Gate Valve: Used to block flow (on/off service) Sliding “gate” on knife-gate valve

CM4120Unit Operations LabPiping Systems Globe Valve: Used to regulate flow Cut-away shows stem seal plug and seat

CM4120 Unit Operations Lab Piping Systems