1、46.1CHAPTER 46PIPES, TUBES, AND FITTINGSPipe . 46.1Fittings . 46.2Joining Methods. 46.2Special Systems 46.6Selection of Materials 46.6Pipe Wall Thickness . 46.7Stress Calculations. 46.7Plastic Piping. 46.7Pipe-Supporting Elements 46.8Pipe Expansion and Flexibility 46.10Pipe Bends and Loops 46.10Expa
2、nsion Joints and Expansion Compensating Devices 46.12HIS CHAPTER covers the selection, application, and installa-Ttion of pipe, tubes, and fittings commonly used for heating, air-conditioning, and refrigeration. Pipe hangers and pipe expansionare also addressed. When selecting and applying these com
3、ponents,applicable local codes, state or provincial codes, and voluntaryindustry standards (some of which have been adopted by code juris-dictions) must be followed.The following organizations in the United States issue codes andstandards for piping systems and components:ASME American Society of Me
4、chanical EngineersASTM American Society for Testing and MaterialsNFPA National Fire Protection AssociationBOCA Building Officials and Code Administrators,InternationalMSS Manufacturers Standardization Society of theValve and Fittings Industry, Inc.AWWA American Water Works AssociationParallel federa
5、l specifications also have been developed by gov-ernment agencies and are used for many public works projects.Chapter IV of ASME Standard B31.9 lists applicable U.S. codesand standards for HVAC piping. In addition, it gives the require-ments for the safe design and construction of piping systems for
6、building heating and air conditioning. ASME Standard B31.5 givessimilar requirements for refrigerant piping.PIPESteel PipeSteel pipe is manufactured by several processes. Seamless pipe,made by piercing or extruding, has no longitudinal seam. Othermanufacturing methods roll a strip or sheet of steel
7、(skelp) into acylinder and weld a longitudinal seam. A continuous-weld (CW)furnace butt-welding process forces and joins the edges together athigh temperature. An electric current welds the seam in electric-resistance-welded (ERW) pipe. ASTM Standards A53 and A106specify steel pipe. Both standards s
8、pecify A and B grades. The Agrade has a lower tensile strength and is not widely used.The ASME pressure piping codes require that a longitudinaljoint efficiency factor E (Table 1) be applied to each type of seamwhen calculating the allowable stress. ASME Standard B36.10Mspecifies the dimensional sta
9、ndard for steel pipe. Through 300 mmdiameter, nominal pipe sizes (NPS) are used, which do not matchthe internal or external diameters. For pipe 350 mm and larger, thesize corresponds to the outside diameter.Steel pipe is manufactured with wall thicknesses identified byschedule or class. Although sch
10、edule numbers and class designa-tions are related, they are not constant for all pipe sizes. UnitedStates standard (STD) and Schedule 40 pipe have the same wallthickness through 250 mm NPS. For 300 mm and larger standardpipe, the wall thickness remains constant at 10 mm, whereas Sched-ule 40 wall th
11、ickness increases with each size. A similar equalityexists between Extra Strong (XS) and Schedule 80 pipe through200 mm; above 200 mm, XS pipe has a 12.7 mm wall, whereasSchedule 80 increases in wall thickness. Table 2 lists properties ofrepresentative steel pipe.Joints in steel pipe are made by wel
12、ding or by using threaded,flanged, or grooved fittings. Unreinforced welded-in branch con-nections weaken a main pipeline, and added reinforcement is nec-essary, unless the excess wall thickness of both mains and branchesis sufficient to sustain the pressure.ASME Standard B31.1 gives formulas for de
13、termining whetherreinforcement is required. Such calculations are seldom needed inHVAC applications because (1) standard pipe through 500 mm NPSat 2.1 MPa requires no reinforcement; full-size branch connectionsare not recommended; and (2) fittings such as tees and reinforcedoutlet fittings provide i
14、nherent reinforcement.Type F steel pipe is not allowed for ASME Standard B31.5refrigerant piping.Copper TubeBecause of their inherent resistance to corrosion and ease ofinstallation, copper and copper alloys are often used in heating, air-conditioning, refrigeration, and water supply installations.
15、Thereare two principal classes of copper tube. ASTM Standard B88The preparation of this chapter is assigned to TC 6.1, Hydronic and SteamEquipment and Systems.Table 1 Allowable Stressesafor Pipe and TubeASTMSpecification Grade TypeManufacturing ProcessAvailable Sizes, mmMinimumTensile Strength, MPaB
16、asicAllowable Stress S, MPaJointEfficiencyFactor EAllowable StressbSE, MPaAllowable Stress RangecSA, MPaA53 Steel F Cont. Weld 15 to 100 310 77.5 0.6 46.5 117A53 Steel B S Seamless 15 to 660 413 103 1.0 103 155A53 Steel B E ERW 50 to 500 413 103 0.85 87.6 155A106 Steel B S Seamless 15 to 660 413 103
17、 1.0 103 155B88 Copper Hard Drawn 8 to 300 248 62 1.0 62 93.1aListed stresses are for temperatures to 340C for steel pipe (to 205C for Type F) and to 120C for copper tubing.bTo be used for internal pressure stress calculations in Equations (1) and (2).cTo be used only for piping flexibility calculat
18、ions; see Equations (3) and (4).46.2 2012 ASHRAE HandbookHVAC Systems and Equipment (SI)includes Types K, L, M, and DWV for water and drain service.ASTM Standard B280 specifies air-conditioning and refrigeration(ACR) tube for refrigeration service.Types K, L, M, and DWV designate descending wall thi
19、cknessesfor copper tube. All types have the same outside diameter for corre-sponding sizes. Table 3 lists properties of ASTM B88 copper tube.In the plumbing industry, tube of nominal size approximates theinside diameter. The heating and refrigeration trades specify coppertube by the outside diameter
20、 (OD). ACR tubing has a different set ofwall thicknesses. Types K, L, and M tube may be hard drawn orannealed (soft) temper.Copper tubing is joined with soldered or brazed, wrought or castcopper capillary socket-end fittings. Table 4 lists pressure/tempera-ture ratings of soldered and brazed joints.
21、 Small copper tube is alsojoined by flare or compression fittings. Hard-drawn tubing has a higher allowable stress than annealedtubing, but if hard tubing is joined by soldering or brazing, theannealed allowable stress should be used.Brass pipe and copper pipe are also made in steel pipe thick-nesse
22、s for threading. High cost has eliminated these materials fromthe market, except for special applications.The heating and air-conditioning industry generally uses Types Land M tubing, which have higher internal working pressure ratingsthan the solder joints used at fittings. Type K may be used withb
23、razed joints for higher pressure-temperature requirements or fordirect burial. Type M should be used with care where exposed topotential external damage.Copper and brass should not be used in ammonia refrigeratingsystems. The section on Special Systems covers other limitations onrefrigerant piping.D
24、uctile Iron and Cast IronCast-iron soil pipe comes as Class 4000 series. It is not usedunder pressure because the pipe is not suitable and the joints are notrestrained. Cast-iron pipe and fittings typically have bell and spigotends for lead and oakum joints or elastomer push-on joints. Cast-iron pip
25、e and fittings are also furnished with no-hub ends for joiningwith no-hub clamps. Local plumbing codes specify permitted mate-rials and joints.Ductile iron has now replaced cast iron for pressure pipe. Ductileiron is stronger, less brittle, and similar to cast iron in corrosion resis-tance. It is co
26、mmonly used for buried pressure water mains or inother locations where internal or external corrosion is a problem.Joints are made with flanged fittings, mechanical joint (MJ) fittings,or elastomer gaskets for bell and spigot ends. Bell and spigot and MJjoints are not self-restrained. Restrained MJ
27、systems are available.Ductile-iron pipe is made in seven thickness classes for different ser-vice conditions. AWWA Standard C150/A2l.50 covers the properselection of pipe classes.FITTINGSThe following standards give dimensions and pressure ratings forfittings, flanges, and flanged fittings. These da
28、ta are also availablefrom manufacturers catalogs.JOINING METHODSThreadingThreading as per ASME Standard B1.20.1 is the most commonmethod for joining small-diameter steel or brass pipe. Pipe with awall thickness less than standard should not be threaded. ASMEStandard B31.5 limits the threading for va
29、rious refrigerants andpipe sizes.Soldering and BrazingCopper tube is usually joined by soldering or brazing socket endfittings. Brazing materials melt above 540C and produce a strongerjoint than solder. Table 4 lists soldered and brazed joint strengths.ASME Standard B16.22 specified wrought copper s
30、older joint fit-tings and ASME Standard B16.18 specified cast copper solder jointfittings are pressure rated the same way as annealed Type L coppertube of the same size. Health concerns have caused many jurisdic-tions to ban solder containing lead or antimony for joining pipe inpotable-water systems
31、. Lead-based solder, in particular, must not beused for potable water.Flared and Compression JointsFlared and compression fittings can be used to join copper, steel,stainless steel, and aluminum tubing. Properly rated fittings cankeep the joints as strong as the tube.Applicable Standards for Fitting
32、sSteelaASME Std.Pipe Flanges and Flanged Fittings B16.5Factory-Made Wrought Steel Buttwelding Fittings B16.9Forged Fittings, Socket-Welding and Threaded B16.11Wrought Steel Buttwelding Short Radius Elbows and Returns B16.28Cast Iron, Malleable Iron, Ductile IronbCast Iron Pipe Flanges and Flanged Fi
33、ttings B16.1Malleable Iron Threaded Fittings B16.3Gray Iron Threaded Fittings B16.4Cast Iron Threaded Drainage Fittings B16.12Ductile Iron Pipe Flanges and Flanged Fittings, Classes 150 and 300 B16.42Copper and BronzecCast Bronze Threaded Fittings, Classes 125 and 25 B16.15Cast Copper Alloy Solder J
34、oint Pressure Fittings B16.18Wrought Copper and Copper Alloy Solder Joint Pressure Fittings B16.22Cast Copper Alloy Solder Joint Drainage Fittings, DWV B16.23Cast Copper Alloy Pipe Flanges and Flanged Fittings, Classes 150, 300, 400, 600, 900, 1500, and 2500 B16.24Cast Copper Alloy Fittings for Flar
35、ed Copper Tubes B16.26Wrought Copper and Wrought Copper AlloySolder Joint Drainage Fittings B16.29NonmetallicdASTM Std.Threaded PVC Plastic Pipe Fittings, Schedule 80 D2464Threaded PVC Plastic Pipe Fittings, Schedule 40 D2466Socket-Type PVC Plastic Pipe Fittings, Schedule 80 D2467Reinforced Epoxy Re
36、sin Gas Pressure Pipe and Fittings D2517Threaded CPVC Plastic Pipe Fittings, Schedule 80 F437Socket-Type CPVC Plastic Pipe Fittings, Schedule 40 F438Socket-Type CPVC Plastic Pipe Fittings, Schedule 80 F439Polybutylene (PB) Plastic Hot- and Cold-WaterDistribution Systems D3309ePlastic Insert Fittings
37、 for Polybutylene Tubing F845eSolvent Cements for PVC Plastic Piping Systems D2564Solvent Cements for CPVC Plastic Pipe and Fittings F493aWrought steel butt-welding fittings are made to match steel pipe wall thicknesses andare rated at the same working pressure as seamless pipe. Flanges and flanged
38、fittingsare rated by working steam pressure classes. Forged steel fittings are rated from 14 to41 MPa in classes and are used for high-temperature and high-pressure service forsmall pipe sizes.bThe class numbers refer to the maximum working saturated steam gage pressure (inpounds per square inch. Mu
39、ltiply these values by 6.9 to convert to kilopascals). Forliquids at lower temperatures, higher pressures are allowed. Groove-end fittings ofthese materials are made by various manufacturers who publish their own ratings.cThe classes refer to maximum working steam gage pressure (in pounds per square
40、inch. Multiply these values by 6.9 to convert to kilopascals). At ambient temperatures,higher liquid pressures are allowed. Solder joint fittings are limited by the strength ofthe soldered or brazed joint (see Table 4).dRatings of plastic fittings match the pipe of corresponding schedule number.eWit
41、hdrawn with no replacement.Pipes, Tubes, and Fittings 46.3Table 2 Steel Pipe DataU.S. Nominal Size,in.NominalSize,mm ScheduleaWall Thickness t, mmInside Diameter d, mmSurface Area Cross Section MassWorking PressurecASTM A53 B to 200COutside, m2/mInside, m2/mMetal Area, mm2Flow Area,mm2Pipe,kg/mWater
42、,kg/mMfr.ProcessJoint TypebkPa (gage)1/4 8 40 ST 2.24 9.25 0.043 0.029 80.6 67.1 0.631 0.067 CW T 129680 XS 3.02 7.67 0.043 0.024 101.5 46.2 0.796 0.046 CW T 60063/8 10 40 ST 2.31 12.52 0.054 0.039 107.7 123.2 0.844 0.123 CW T 140080 XS 3.20 10.74 0.054 0.034 140.2 90.7 1.098 0.091 CW T 56541/2 15 4
43、0 ST 2.77 15.80 0.067 0.050 161.5 196.0 1.265 0.196 CW T 147680 XS 3.73 13.87 0.067 0.044 206.5 151.1 1.618 0.151 CW T 51923/4 20 40 ST 2.87 20.93 0.084 0.066 214.6 344.0 1.68 0.344 CW T 149680 XS 3.91 18.85 0.084 0.059 279.7 279.0 2.19 0.279 CW T 46951 25 40 ST 3.38 26.64 0.105 0.084 318.6 557.6 2.
44、50 0.558 CW T 155880 XS 4.55 24.31 0.105 0.076 412.1 464.1 3.23 0.464 CW T 44271 1/4 32 40 ST 3.56 35.05 0.132 0.110 431.3 965.0 3.38 0.965 CW T 157980 XS 4.85 32.46 0.132 0.102 568.7 827.6 4.45 0.828 CW T 40961 1/2 40 40 ST 3.68 40.89 0.152 0.128 515.5 1 313 4.05 1.313 CW T 159380 XS 5.08 38.10 0.1
45、52 0.120 689.0 1 140 5.40 1.140 CW T 39722 50 40 ST 3.91 52.50 0.190 0.165 690.3 2 165 5.43 2.165 CW T 158680 XS 5.54 49.25 0.190 0.155 953 1 905 7.47 1.905 CW T 37992 1/2 65 40 ST 5.16 62.71 0.229 0.197 1 099 3 089 8.62 3.089 CW W 367580 XS 7.01 59.00 0.229 0.185 1 454 2 734 11.40 2.734 CW W 57573
46、80 40 ST 5.49 77.93 0.279 0.245 1 438 4 769 11.27 4.769 CW W 332380 XS 7.62 73.66 0.279 0.231 1 946 4 261 15.25 4.261 CW W 52884 100 40 ST 6.02 102.26 0.359 0.321 2 048 8 213 16.04 8.213 CW W 296580 XS 8.56 97.18 0.359 0.305 2 844 7 417 22.28 7.417 CW W 47926 150 40 ST 7.11 154.05 0.529 0.484 3 601
47、18 639 28.22 18.64 ERW W 479980 XS 10.97 146.33 0.529 0.460 5 423 16 817 42.49 16.82 ERW W 83368 200 30 7.04 205.0 0.688 0.644 4 687 33 000 36.73 33.01 ERW W 362740 ST 8.18 202.7 0.688 0.637 5 419 32 280 42.46 32.28 ERW W 443380 XS 12.70 193.7 0.688 0.608 8 234 29 460 64.51 29.46 ERW W 762610 250 30
48、 7.80 257.5 0.858 0.809 6 498 52 060 50.91 52.06 ERW W 334440 ST 9.27 254.5 0.858 0.800 7 683 50 870 60.20 50.87 ERW W 4178XS 12.70 247.7 0.858 0.778 10 388 48 170 81.39 48.17 ERW W 611680 15.06 242.9 0.858 0.763 12 208 46 350 95.66 46.35 ERW W 745312 300 30 8.38 307.1 1.017 0.965 8 307 74 060 65.09
49、 74.06 ERW W 3096ST 9.53 304.8 1.017 0.958 9 406 72 970 73.70 72.97 ERW W 364140 10.31 303.2 1.017 0.953 10 158 72 190 79.59 72.21 ERW W 4020XS 12.70 298.5 1.017 0.938 12 414 69 940 97.28 69.96 ERW W 515780 17.45 289.0 1.017 0.908 16 797 65 550 131.62 65.57 ERW W 741914 350 30 ST 9.53 336.6 1.117 1.057 10 356 88 970 81.15 88.96 ERW W 331640 11.10 333.4 1.117 1.047 12 013 87 290 94.13 87.30 ERW W 3999XS 12.70 330.2 1.117 1.037 13 681 85 610 107.21 85.63 ERW W 469580 19.05 317.5 1.117 0.997 20 142 79 160 157.82 79.17 ERW W 745316 400 30 ST 9.53 387.4 1.277 1.217 11 876 117 800 93
