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1 CM4120 Unit Operations Lab Piping Systems Piping Systems in the Chemical Process Industries March, 2009 Introduction Basis for Design Piping Codes and.

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Presentation on theme: "1 CM4120 Unit Operations Lab Piping Systems Piping Systems in the Chemical Process Industries March, 2009 Introduction Basis for Design Piping Codes and."— Presentation transcript:

1 1 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

2 2 CM4120 Unit Operations Lab Piping Systems Piping Systems include: Pipe, Flanges, Fittings Bolting, Gaskets Valves Hangers and Supports Insulations, Coverings, Coatings Heat Tracing

3 3 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, 7 th ed. McGraw-Hill, 2000

4 4 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

5 5 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

6 6 CM4120 Unit Operations Lab Piping Systems Piping System Routing and Layout The unwritten #1 rule: Serviceability/Operability

7 7 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

8 8 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 Its the LAW

9 9 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.

10 10 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

11 11 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

12 12 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

13 13 CM4120 Unit Operations Lab Piping Systems Piping Design Process – a three step approach 1. Design for Flow Find min. diameter to achieve desired flow velocity 2. Design for Pressure Integrity Find min. wall thickness for process and external conditions Find appropriate rating of in-line components 3. Re-check for Flow Criteria

14 14 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

15 15 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

16 16 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

17 17 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) ft/sec high pressure (>100 psig) ft/sec Slurries: > min. entrainment velocity from Peters and Timmerhaus, Plant Design and Economics for Chemical Engineers, 4 th ed., McGraw-Hill, 1991.

18 18 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?

19 19 CM4120 Unit Operations Lab Piping Systems Determine min. reqd wall thickness: Pressure Integrity Design Method ASME B31.3, t m =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= addl thickness for corrosion, external loads, etc.

20 20 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.

21 21 CM4120 Unit Operations Lab Piping Systems Inline Components: Fittings Valves Gaskets, Seals, and Thread Sealants Connection Hardware – Bolts, studs, nuts, washers

22 22 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

23 23 CM4120 Unit Operations Lab Piping Systems Maximum Allowable non-shock Pressure (psig) Temperature ( o F) Pressure Class Rating for Flanged Fittings (lb) Hydrostatic Test Pressure (psig) to Ratings for flanged steel pipe fittings, ANSI B

24 24 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.

25 25 CM4120 Unit Operations Lab Piping Systems Piping Insulation Prevent heat loss/ gain Prevent condensation – below ambient Personnel protection – over 125 o F Freeze protection – outdoor cold climates Fire protection Noise control

26 26 CM4120 Unit Operations Lab Piping Systems Recommended minimum Thickness of Insulation (inches) * Nominal Pipe Size NPS (inches) Temperature Range ( o C) Temperature Range ( o F) Hot Water Low Pressure Steam Medium Pressure Steam High Pressure Steam < 1" /4" - 2" /2" - 4" " - 6" > 8" * based on insulation with thermal resistivity in the range ft 2 hr o F/ Btu in Source: Engineering Toolbox, http://www.engineeringtoolbox.com/pipes-insulation-thickness-d_16.html

27 27 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

28 28 CM4120 Unit Operations Lab Piping Systems Fiberglass Insulation w/ Asbestos-plastered fitting coverings

29 29 CM4120 Unit Operations Lab Piping Systems Metal Jacketed insulation covering

30 30 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.

31 31 CM4120 Unit Operations Lab Piping Systems Piping Supports

32 32 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

33 33 CM4120 Unit Operations Lab Piping Systems Steel Pipe - Distance between Supports (ft) Outside Diameter (in) Horizontal RunVertical Run 1/ / / / / Source: Engineering Toolbox, http://www.engineeringtoolbox.com/steel-pipe-supports-d_1071.html

34 34 CM4120 Unit Operations Lab Piping Systems Inadequate support

35 35 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/in o F

36 36 CM4120 Unit Operations Lab Piping Systems Temp of pipe at amb. cond. =70 o F Temp of 100 psig sat. steam =338 o F ΔT=268 o F L=20=240 expansion due to temperature increase is α *L* ΔT =(6.6x10 -6 in/in o F)*(240in)*(268 o F) =0.42 in per 20 of pipe

37 37 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 cant 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=30x10 6 psi for low carbon steel

38 38 CM4120 Unit Operations Lab Piping Systems σ= α *(ΔT)*E =(6.6x10 -6 in/in o F)*(268 o F)*(30x10 6 lb f /in 2 ) =53,000 lb f /in 2 since σ=F/A, The force on the end restraints is F=σ*A where:F=force in lb f A=cross sec. area of 2, sched 40 pipe in sq. inches

39 39 CM4120 Unit Operations Lab Piping Systems A= Π (OD 2 -ID 2 )/4 = Π ( )/4 =1.07 sq.in F= σ*A =(53,000 lb f /in 2 )*(1.07 in 2 ) Force on the end restraints = 57,000 lb f or 28.5 tons

40 40 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

41 41 CM4120 Unit Operations Lab Piping Systems Heat Tracing

42 42 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

43 43 CM4120 Unit Operations Lab Piping Systems References: Piping Handbook, 7 th ed., Nayyar, McGraw-Hill, New York, Plant Desing and Economics for Chemical Engineers, 4 th ed., Peters and Timmerhaus, McGraw-Hill, Valve Handbook, Skousen, McGraw-Hill, New York, Flowserve Corp., Sept The Engineering Toolbox, Sept

44 44 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

45 45 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

46 46 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

47 47 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

48 48 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

49 49 CM4120 Unit Operations Lab Piping Systems Materials – Others Glass Concrete Lined or coated Glass Rubber Cement Teflon Zinc (galvanized pipe) Double Containment piping systems

50 50 CM4120 Unit Operations Lab Piping Systems Pipe Joints Threaded Welded Soldered/ Brazed Glued Compression Bell and spigot Upset or expanded

51 51 CM4120 Unit Operations Lab Piping Systems Threaded joints

52 52 CM4120 Unit Operations Lab Piping Systems Soldered joints

53 53 CM4120 Unit Operations Lab Piping Systems Welded joints

54 54 CM4120 Unit Operations Lab Piping Systems Compression joints

55 55 CM4120 Unit Operations Lab Piping Systems Mechanical joints shown on glass drain piping system

56 56 CM4120 Unit Operations Lab Piping Systems Fittings for joining 2 sections of pipe: Coupling Reducing Coupling Union Flange

57 57 CM4120 Unit Operations Lab Piping Systems Fittings for changing directions in pipe: 45 o Ell 90 o Ell Street Ell

58 58 CM4120 Unit Operations Lab Piping Systems Fittings for adding a branch in a run of piping: Tee Cross

59 59 CM4120 Unit Operations Lab Piping Systems Fittings for blocking the end of a run of piping: Pipe plug Pipe cap Blind Flange

60 60 CM4120 Unit Operations Lab Piping Systems Misc. pipe fittings: Nipple Reducing bushing

61 61 CM4120 Unit Operations Lab Piping Systems Gate Valve: Used to block flow (on/off service) Sliding gate on knife-gate valve

62 62 CM4120 Unit Operations Lab Piping Systems Globe Valve: Used to regulate flow Cut-away shows stem seal plug and seat

63 63 CM4120 Unit Operations Lab Piping Systems Ball Valve: Typically used as block valve Quarter-turn valve Cut-away shows ball and seat

64 64 CM4120 Unit Operations Lab Piping Systems Butterfly Valve: Can be used for flow control or on/off Valve actuator/ positioner for accurate flow control

65 65 CM4120 Unit Operations Lab Piping Systems Check Valves: Used to prevent backflow Piston check Swing check


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