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 12 in.diameter, nominal pipe sizes (NPS) are used, which do not matchthe internal or external diameters. For pipe 14 in. and larger, the sizecorresponds to the outside diameter.Steel pipe is manufactured with wall thicknesses identified byschedule or weight class. Altho
10、ugh schedule numbers and weightclass designations are related, they are not constant for all pipe sizes.Standard weight (STD) and Schedule 40 pipe have the same wallthickness through NPS 10. For 12 in. and larger standard weightpipe, the wall thickness remains constant at 0.375 in., whereasSchedule
11、40 wall thickness increases with each size. A similarequality exists between Extra Strong (XS) and Schedule 80 pipethrough 8 in.; above 8 in., XS pipe has a 0.500 in. wall, whereasSchedule 80 increases in wall thickness. Table 2 lists properties ofrepresentative steel pipe.Joints in steel pipe are m
12、ade by welding 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 formu
13、las for determining whetherreinforcement is required. Such calculations are seldom needed inHVAC applications because (1) standard-weight pipe through NPS20 at 300 psig requires no reinforcement; full-size branch connec-tions are not recommended; and (2) fittings such as tees and rein-forced outlet
14、fittings provide inherent 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 supp
15、ly installations. 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 ProcessAvailableSizes, in.MinimumTens
16、ile Strength, psiBasicAllowable Stress S, psiJointEfficiencyFactor EAllowable StressbSE, psiAllowable Stress RangecSA, psiA53 Steel F Cont. Weld 1/2 to 4 45,000 11,250 0.6 6,800 16,900A53 Steel B S Seamless 1/2 to 26 60,000 15,000 1.0 15,000 22,500A53 Steel B E ERW 2 to 20 60,000 15,000 0.85 12,800
17、22,500A106 Steel B S Seamless 1/2 to 26 60,000 15,000 1.0 15,000 22,500B88 Copper Hard Drawn 1/4 to 12 36,000 9,000 1.0 9,000 13,500aListed stresses are for temperatures to 650F for steel pipe (to 400F for Type F) and to 250F for copper tubing.bTo be used for internal pressure stress calculations in
18、 Equations (1) and (2).cTo be used only for piping flexibility calculations; see Equations (3) and (4).46.2 2012 ASHRAE HandbookHVAC Systems and Equipment includes Types K, L, M, and DWV for water and drain service.ASTM Standard B280 specifies air-conditioning and refrigeration(ACR) tube for refrige
19、ration service.Types K, L, M, and DWV designate descending wall thicknessesfor 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
20、and refrigeration trades specify coppertube by the outside diameter (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
21、 lists pressure/tempera-ture ratings of soldered and brazed joints. 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
22、.Brass pipe and copper pipe are also made in steel pipe thick-nesses 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 ratin
23、gsthan the solder joints used at fittings. Type K may be used withbrazed 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
24、 on Special Systems covers other limitations onrefrigerant piping.Ductile Iron and Cast IronCast-iron soil pipe comes in XH or service weight. 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 spigotend
25、s for lead and oakum joints or elastomer push-on joints. Cast-iron pipe 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, les
26、s brittle, and similar to cast iron in corrosion resis-tance. It is commonly 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
27、. Bell and spigot and MJjoints are not self-restrained. Restrained MJ 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
28、 pressure ratings forfittings, flanges, and flanged fittings. These data 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
29、weight should not be threaded.ASME Standard B31.5 limits the threading for various refrigerantsand pipe sizes.Soldering and BrazingCopper tube is usually joined by soldering or brazing socket endfittings. Brazing materials melt above 1000F and produce a stron-ger joint than solder. Table 4 lists sol
30、dered and brazed jointstrengths. ASME Standard B16.22 specified wrought copper solderjoint fittings and ASME Standard B16.18 specified cast copper sol-der joint fittings are pressure rated the same way as annealed TypeL copper tube of the same size. Health concerns have caused manyjurisdictions to b
31、an solder containing lead or antimony for joiningpipe in potable-water systems. Lead-based solder, in particular,must not be used for potable water.Flared and Compression JointsFlared and compression fittings can be used to join copper, steel,stainless steel, and aluminum tubing. Properly rated fitt
32、ings cankeep the joints as strong as the tube.Applicable Standards for FittingsSteelaASME 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 B16.2
33、8Cast Iron, Malleable Iron, Ductile IronbCast Iron Pipe Flanges and Flanged Fittings 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
34、 Bronze Threaded Fittings, Classes 125 and 25 B16.15Cast Copper Alloy Solder Joint 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
35、, 300, 400, 600, 900, 1500, and 2500 B16.24Cast Copper Alloy Fittings for Flared 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 D2
36、466Socket-Type PVC Plastic Pipe Fittings, Schedule 80 D2467Reinforced Epoxy Resin 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)
37、 Plastic Hot- and Cold-WaterDistribution Systems D3309ePlastic Insert Fittings 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 an
38、dare rated at the same working pressure as seamless pipe. Flanges and flanged fittingsare rated by working steam pressure classes. Forged steel fittings are rated from 2000to 6000 psi in classes and are used for high-temperature and high-pressure service forsmall pipe sizes.bThe class numbers refer
39、to the maximum working saturated steam gage pressure (inpsi). For liquids at lower temperatures, higher pressures are allowed. Groove-endfittings of these materials are made by various manufacturers who publish their ownratings.cThe classes refer to maximum working steam gage pressure (in psi). At a
40、mbient tem-peratures, higher liquid pressures are allowed. Solder joint fittings are limited by thestrength of the soldered or brazed joint (see Table 4).dRatings of plastic fittings match the pipe of corresponding schedule number.eWithdrawn with no replacement.Pipes, Tubes, and Fittings 46.3Table 2
41、 Steel Pipe DataNominal Size,in.PipeOD,in.Schedule Number or WeightaWall Thickness t, in.Inside Diameter d, in.Surface Area Cross Section WeightWorking PressurecASTM A53 B to 400FOutside, ft2/ftInside,ft2/ftMetal Area, in2Flow Area, in2Pipe,lb/ftWater,lb/ftMfr.ProcessJoint Typebpsig1/4 0.540 40 ST 0
42、.088 0.364 0.141 0.095 0.125 0.104 0.424 0.045 CW T 18880 XS 0.119 0.302 0.141 0.079 0.157 0.072 0.535 0.031 CW T 8713/8 0.675 40 ST 0.091 0.493 0.177 0.129 0.167 0.191 0.567 0.083 CW T 20380 XS 0.126 0.423 0.177 0.111 0.217 0.141 0.738 0.061 CW T 8201/2 0.840 40 ST 0.109 0.622 0.220 0.163 0.250 0.3
43、04 0.850 0.131 CW T 21480 XS 0.147 0.546 0.220 0.143 0.320 0.234 1.087 0.101 CW T 7533/4 1.050 40 ST 0.113 0.824 0.275 0.216 0.333 0.533 1.13 0.231 CW T 21780 XS 0.154 0.742 0.275 0.194 0.433 0.432 1.47 0.187 CW T 6811 1.315 40 ST 0.133 1.049 0.344 0.275 0.494 0.864 1.68 0.374 CW T 22680 XS 0.179 0.
44、957 0.344 0.251 0.639 0.719 2.17 0.311 CW T 6421 1/4 1.660 40 ST 0.140 1.380 0.435 0.361 0.669 1.50 2.27 0.647 CW T 22980 XS 0.191 1.278 0.435 0.335 0.881 1.28 2.99 0.555 CW T 5941 1/2 1.900 40 ST 0.145 1.610 0.497 0.421 0.799 2.04 2.72 0.881 CW T 23180 XS 0.200 1.500 0.497 0.393 1.068 1.77 3.63 0.7
45、65 CW T 5762 2.375 40 ST 0.154 2.067 0.622 0.541 1.07 3.36 3.65 1.45 CW T 23080 XS 0.218 1.939 0.622 0.508 1.48 2.95 5.02 1.28 CW T 5512 1/2 2.875 40 ST 0.203 2.469 0.753 0.646 1.70 4.79 5.79 2.07 CW W 53380 XS 0.276 2.323 0.753 0.608 2.25 4.24 7.66 1.83 CW W 8353 3.500 40 ST 0.216 3.068 0.916 0.803
46、 2.23 7.39 7.57 3.20 CW W 48280 XS 0.300 2.900 0.916 0.759 3.02 6.60 10.25 2.86 CW W 7674 4.500 40 ST 0.237 4.026 1.178 1.054 3.17 12.73 10.78 5.51 CW W 43080 XS 0.337 3.826 1.178 1.002 4.41 11.50 14.97 4.98 CW W 6956 6.625 40 ST 0.280 6.065 1.734 1.588 5.58 28.89 18.96 12.50 ERW W 69680 XS 0.432 5.
47、761 1.734 1.508 8.40 26.07 28.55 11.28 ERW W 12098 8.625 30 0.277 8.071 2.258 2.113 7.26 51.16 24.68 22.14 ERW W 52640 ST 0.322 7.981 2.258 2.089 8.40 50.03 28.53 21.65 ERW W 64380 XS 0.500 7.625 2.258 1.996 12.76 45.66 43.35 19.76 ERW W 110610 10.75 30 0.307 10.136 2.814 2.654 10.07 80.69 34.21 34.
48、92 ERW W 48540 ST 0.365 10.020 2.814 2.623 11.91 78.85 40.45 34.12 ERW W 606XS 0.500 9.750 2.814 2.552 16.10 74.66 54.69 32.31 ERW W 88780 0.593 9.564 2.814 2.504 18.92 71.84 64.28 31.09 ERW W 108112 12.75 30 0.330 12.090 3.338 3.165 12.88 114.8 43.74 49.68 ERW W 449ST 0.375 12.000 3.338 3.141 14.58
49、 113.1 49.52 48.94 ERW W 52840 0.406 11.938 3.338 3.125 15.74 111.9 53.48 48.44 ERW W 583XS 0.500 11.750 3.338 3.076 19.24 108.4 65.37 46.92 ERW W 74880 0.687 11.376 3.338 2.978 26.03 101.6 88.44 43.98 ERW W 107614 14.00 30 ST 0.375 13.250 3.665 3.469 16.05 137.9 54.53 59.67 ERW W 48140 0.437 13.126 3.665 3.436 18.62 135.3 63.25 58.56 ERW W 580XS 0.500 13.000 3.665 3.403 21.21 132.7 72.04 57.44 ERW W 68180 0.750 12.500 3.665 3.272 31.22 122.7 106.05 53.11 ERW W 108116 16.00 30 ST 0.375 15.250 4.189 3.992 18.41 182.6 62.53 79.04 ERW W 42140 XS 0.500 15.000 4.189 3.927 24.35 176.
