1、ANSI/SMACNA 0062006HVACDUCT CONSTRUCTIONSTANDARDSMETAL AND FLEXIBLESHEET METAL AND AIR CONDITIONING CONTRACTORSNATIONAL ASSOCIATION, INC.www.smacna.orgHVACDUCT CONSTRUCTIONSTANDARDSMETAL AND FLEXIBLETHIRD EDITION 2005SHEET METAL AND AIR CONDITIONING CONTRACTORSNATIONAL ASSOCIATION, INC.4201 Lafayett
2、e Center DriveChantilly, VA 201511209www.smacna.orgHVACDUCT CONSTRUCTIONSTANDARDSMETAL AND FLEXIBLECOPYRIGHT C0069 SMACNA 2005All Rights ReservedbySHEET METAL AND AIR CONDITIONING CONTRACTORSNATIONAL ASSOCIATION, INC.4201 Lafayette Center DriveChantilly, VA 201511209Printed in the U.S.A.FIRST EDITIO
3、N 1985SECOND EDITION 1995THIRD EDITION 2005SECOND PRINTING 2006THIRD PRINTING 2008FOURTH PRINTING 2009Except as allowed in the Notice to Users and in certain licensing contracts, no part of this book may bereproduced, stored in a retrievable system, or transmitted, in any form or by any means, elect
4、ronic,mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher.iiiHVAC Duct Construction Standards Metal and Flexible Third EditionFOREWORDThis Third Edition of the SMACNA commercial metal and flexible duct construction standards is another in a longli
5、ne dating from the 1950s. A quick overview of the changes is provided in the front of this manual.SMACNA expresses appreciation to the many who have offered suggestions for constructive improvement in the fab-rication and installation of duct systems. Suggestions for future improvement are welcome.
6、Special thanks is givento those who volunteered their time, gave special knowledge and struggled with development of a consensus thatwould reflect the needs for a diversified industry. Although standardization intrinsically involves selection, no inten-tion of discrimination against the use of any p
7、roduct or method that would serve a designers need equally or betterexists.SHEET METAL AND AIR CONDITIONING CONTRACTORSNATIONAL ASSOCIATION, INC.iv HVAC Duct Construction Standards Metal and Flexible Third EditionHVAC DUCT CONSTRUCTION TASK FORCERoy Jensen, ChairmanMechOneColorado Springs, ColoradoD
8、ouglas AhlbergArctic Sheet Metal, Inc.Portland, OregonChris CombeSuperior Air Handling CorporationClearfield, UtahMark EdhammerSouthland IndustriesSan Jose, CaliforniaRoy RicciMcCuskerGill, Inc.Hingham, MassachusettsJerry RobinsonStromberg Sheet Metal Works, Inc.Beltsville, MarylandRobert J. Wasilew
9、ski, Staff LiaisonSMACNA, Inc.Chantilly, VirginiaEli P. Howard, III, Staff LiaisonSMACNA, Inc.Chantilly, VirginiaFORMER COMMITTEE MEMBERS* ANDOTHER CONTRIBUTORS TO THE THIRD EDITIONMichael Mamayek*, Chairman 1992 1993Illingworth CorporationMilwaukee, WIThomas Boniface*, Chairman 1989 1991Independent
10、 Sheet MetalWayne, NJH. Andrew Kimmel*, Chairman 1988E.W. Ensroth Co.Warren, MIRobert S. Deeds*, Chairman 1986 1987METCO, Inc.Salt Lake City, UTNorman T.R. Heathorn*N.B. Heathorn, Inc.Oakland, CAGerald D. Hermanson*Hermanson CorporationRenton, WAGeorge J. Thomas, Jr.*Thomas Roofing 2. Be dielectrica
11、lly isolated;3. Be waterproof, weatherproof, or ul-traviolet ray resistant;4. Withstand temperatures higher than120F (48C) or lower than 40F(4.4C);5. Contain radionuclides or serve inother safetyrelated construction;6. Be electrically grounded;7. Maintain leakage integrity at pres-sures in excess of
12、 their duct classifi-cation;8. Be underground below the watertable;9. Be submerged in liquid;10. Withstand continuous vibration vis-ible to the naked eye;11. Be totally leakfree within an encap-sulating vapor barrier; and12. Create closure in portions of thebuilding structure used as ducts,1.3HVAC D
13、uct Construction Standards Metal and Flexible Third Editionsuch as ceiling plenums, shafts, orpressurized compartments.f. The requirements to seal apply to bothpositive and negative pressure modes ofoperation.g. Externally insulated ducts located out-side of buildings shall be sealed beforebeing ins
14、ulated, as though they were in-side. If air leak sites in ducts located out-side of buildings are exposed to weather,they shall receive exterior duct sealant.An exterior duct sealant is defined as asealant that is marketed specifically asforming a positive air and watertightseal, bonding well to the
15、 metal involved,remaining flexible with metal move-ment, and having a service temperaturerange of 30F (34C) to 175F (79C).If exposed to direct sunlight, it shall alsobe ultraviolet ray and ozoneresistant orshall, after curing, be painted with acompatible coating that provides suchresistance. The ter
16、m sealant is not limit-ed to adhesives or mastics but includestapes and combinations of openweavefabric or absorbent strips and mastics.1.3.2 Rectangular Duct ReinforcementS1.10 Unless otherwise specified or allowed, rec-tangular ductwork shall be constructed in ac-cordance with Tables 21 through 23
17、3 anddetails associated with them.S1.11 The duct gage tables are based on G60coated galvanized steel of lockforming gradeconforming to ASTM Standards A653 andA924. Uncoated steel, prepainted steel, steelwith metal coating such as aluminum or alu-minumzinc compounds, and stainless steelmay be used if
18、 a minimum correspondingbase metal thickness and material strength isprovided. Lockforming grades of such mate-rial must be used.The use of alternative materials requiresspecification or approval by a designer. Thesurface conditions, hardness, ductility, corro-sion resistance, and other characterist
19、ics ofthese materials must be judged acceptable bythe designer for the planned service.Specifications that refer to use of materialthat is two gages heavier mean two numbersseparated in a series that uses both odd andeven number progression; e.g., 18 is twogages heavier than 20 on Appendix pagesA.1,
20、 A.2 and A.3.S1.12 Unless otherwise specified, reinforcementmay be uncoated steel or galvanized steel.S1.13 A reinforcement code classification (letterand EI index) higher than indicated must besubstituted when the tables do not provide thespecific construction details for a lower clas-sification. A
21、 higher rated construction mem-ber may also be substituted for convenience.S1.14 Joint spacing on unreinforced ducts is unlim-ited. On ducts that require reinforcement,joint spacing is unrestricted except that thejoint itself must qualify for the minimum re-inforcement code associated with the rein-
22、forcement spacing.S1.15 Duct sides that are 19 in. (483 mm) and overand are 20 gage (1.00 mm) or less, with morethan 10 square feet (0.93 square m) of un-braced panel area, shall be crossbroken orbeaded as indicated in Figure 29 unless theyare lined or externally insulated. Ducts thatare of heavier
23、gage, smaller dimensions, andsmaller panel area and those that are lined orexternally insulated are not required to havecrossbreaking or beading.S1.16 Fittings shall be reinforced like sections ofstraight duct. On size change fittings, thegreater fitting dimension determines the ductgage. Where fitt
24、ing curvature or internalmember attachments provide equivalent ri-gidity, such features may be credited as rein-forcement.S1.17 Duct wall thickness, joints, seams, and rein-forcements must be coordinated to provideproper assembly.S1.18 Other construction that meets the functionalcriteria in Chapter
25、11 or is as serviceable asthat produced by the construction tables maybe provided.1.3.3 Tie Rod InstallationsS1.19 Internal ties shall be one of the methodsshown in Figures 25 and 26. The restrainingmember and its connections shall be capableof sustaining a load equal to 75 percent of the1.4 HVAC Du
26、ct Construction Standards Metal and Flexible Third Editionduct construction pressure class load appliedas 5.2 pounds per square foot per inch of wa-ter gage (101.63 kg per square meter per kPa)over an area equal to the width of the ducttimes the reinforcement interval. When morethan one tie rod is u
27、sed at a crossection of theduct, the design load may be proportionatelyreduced. For Tables 21 through 27, ductsizes over 20 in. (508 mm) have tie rodconstruction alternatives in many instances.S1.19.1 Intermediate Reinforcement and Joint TieRod LoadsThe steel tie rod design load Tables 234 and234M g
28、ive the load for both positive andnegative pressure service on ducts of 48 in.(1200 mm) through 120 in. (3000 mm) ateach pressure class.S1.19.2 Tie Rod AlternativesA tie rod may be attached to any intermediateangle, channel, or zee by Figure 25 (A), (B),(C), or (F). When one of these backs up ajoint
29、, the attachment options are the same.The attachment of a tie rod member that rein-forces a joint is allowed for joints T3, T6a,T8a, T14, T16, T21, T24, and T25.The attachment of tie rods or tie straps as inFigure 26 by welding, bolting, riveting, orscrewing within one inch (25 mm) of eachside of jo
30、ints T 15, T21, and the T24 andT25 series. Each tie rod may be sized for onehalf of the load in Tables 234 and 234M.S1.19.3 Only one tie rod is required for joint T22.Only one tie rod is required on negative pres-sure for joints T15, T21, T24, T25 usingFigure 25(G). On 18 gage (1.31 mm) ductwith 2 i
31、n. wg (500 Pa) positive pressure asingle tie rod for T21, the pocket side of T15or pinned flanges of T24 and T25 is accept-ed as G rating up to 96 in. (2400 mm).S1.19.4 For positive pressure service, several alterna-tives are available for compliance withTables 234 and 234M. Partially or fullythread
32、ed tie rod from Tables 235 and 235Mmay be used by size readout or the allowableload data may be used for sizing calculationsat 150 percent of the loads in Tables 234 and234M. One half inch (12.7 mm) ridgid con-duit (RC) may be used. Thinwall (EMT) con-duit may be used with these size and load lim-it
33、s applying for Tables 234 and 234M: 900lbs (400 kg) for 1_w in. (12.1 mm); 1340 lbs(600 kg) for 3_r in. (19.1 mm); 1980 lbs (900kg) for 1 in. (25 mm). 1 in. 1_r in. (25 3mm) strap may be used provided that weldstress does not exceed 13,600 psi (93,772kPa) and that any bolts are sized per Tables235 a
34、nd 235M as minimums.S1.19.5 For negative pressure rods, tubing, pipe, orangles are alternatives. The selection stepsare as follows:Step 1: Find the design load for the pres-sure class and duct width in Table234.Step 2A: For rods, from Table 236 for thelength to be used, select a size tomeet the load
35、 from Table 234 orcalculate the size needed to limitthe compression stress to that as-sociated with a maximum lengthto radius of gyration ratio (L/rg)or;Step 2B: For rigid conduit (RC), select fromTable 237 the smallest size of thelength that satisfies the load fromTable 234 or;Step 2C: For EMT cond
36、uit, select fromTable 238 the smallest size for thelength that satisfies the load fromTable 234 or;Step 2D: For pipe, select from Table 239the smallest size for the length thatsatisfies the load from Table 234or;Step 2E: For angles, select from Table 240the smallest size for the length thatsatisfies
37、 the load from Table 234.S1.20 Holes made in the duct wall for tie rod pas-sage shall be of minimum size and shall besealed in accordance with the provisions ofS1.8 and S1.9. Except as limited by jointspecifications and certain mandatory uses, tierod alternatives are indicated in Tables 21through 27
38、 for reinforcement sizes listed tothe right of duct wall thickness. G denotes thesize with tie rod on 22 gage in H22G nomen-clature.S1.21 Tie rods shall be galvanized steel. All internalties, whether of rod, tube, pipe, or angle shall1.5HVAC Duct Construction Standards Metal and Flexible Third Editi
39、onbe of material having the same nature andcorrosion resistance as the duct wall material.Concealed components shall not be subject tonor cause galvanic corrosion. Tie straps, usedon positive pressure only, shall be 1 in. 1_iin. (25 3.2 mm) minimum galvanized steeland the smallest edge shall face th
40、e airflow.S1.22 When the internal ties are integrated withsupports such as those in Figure 59, theyshall be selected to be suitable for additionalduty.S1.23 Up to 120 in. (3048 mm) width ties shall bespaced at even intervals of duct width not ex-ceeding 60 in. (1524 mm). The use of tiesdoes not void
41、 the need to attach reinforce-ments to the duct wall, however, when tiesoccur outside the duct, as on twosided orfoursided reinforcements at positive 4 in. wg(1000 Pa) and over, the attachment withintwo inches of the corner is not required. Referto Figure 212.S1.24 Ties shall be attached so that the
42、y will notloosen or detach for the selected duct pres-sure service class nor for an occasional 50percent over pressure temporary condition.For positive pressure, threaded inserts placedin pipes and tubes shall be secure at 200 per-cent of Table 234 design load.S1.25 When ties occur in two directions
43、 in the samevicinity, they shall either be prevented fromcontacting or be permanently fastened to-gether.S1.26 Refer to Figures 25, 26, 213, and 59 forbasic tie rod application details on mediumand large size ducts.S1.27 Ties may be structural components of theduct and used as part of the suspension
44、 systemfor ducts over 96 in. (2438 mm) in width, pro-vided that the hanger load is directly trans-mitted to a trapeze or duct reinforcementmember beneath the duct.S1.28 The construction of ducts of widths greaterthan 120 in. (30,488 mm) involves the use oftie rods on joints and intermediate reinforc
45、e-ment at intervals not exceeding 60 in. (1.5 m)for 6 in. wg (1500 Pa) or less. For 10 in. wg(2500 Pa) the maximum interval is 48 in. (1.2m), see Figure 213 for construction sched-ules.S1.29 Rectangular aluminum duct construction us-ing ASTM Standard B 209 alloy sheet and theadaptations of the steel
46、 duct constructiontables set forth in Tables 250 to 252 is ac-ceptable for pressure classes not exceeding 3in. wg (750 Pa).S1.30 For Tables 21, 22, 23, and 24, use equiva-lent sheet thickness from Table 250.S1.31 For Tables 231, 232, and 233, a connectornot using angles or bar stock must have itsthi
47、ckness increased per Table 250 and its di-mensions increased per Table 251.S1.32 For Tables 231, 232 and 233, a connectorusing angles or bar stock must have its alumi-num thickness increased per Table 250 andmust use either aluminum stock or galva-nized stock from Table 251.S1.33 For Table 229, use
48、only galvanized steelmembers in Table 252 or the equivalent alu-minum members. Use either galvanized steelmembers of dimensions given or aluminummembers having both thickness and dimen-sion conforming to Table 252. Other suitablealuminum shapes having a moment of inertiathree times that of steel may
49、 be used.S1.34 Add fasteners as necessary to carry loadings.S1.35 Consider the need for dielectric isolation byzinc chromate paint, asphalt impregnated pa-per, bituminous paint, or other method.S1.36 Follow construction details for steelconstruction standards unless they are super-seded by data on this page or by other consid-erations pertinent to aluminum. Use a lockforming grade of sheet material.1.3.4 Transverse Joints for Rect
