1、 SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
2、from, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2008 SAE International All rights reserved. No part of this publication m
3、ay be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA)
4、 Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgAIR869B AEROSPACEINFORMATIONREPORTIssued 1967-04 Reaffirmed 2004-04 Revised 2008-09 Superseding AIR869A (R) V-Couplings, Including V-Band and V-Retainer Coupling Assemblies, Flange and Seal Design, Application of RATI
5、ONALEMany of the referenced standards have been replaced by new SAE and other standards. More information and expanded explanations have been added.1. SCOPE This SAE Aerospace Information Report (AIR) is intended to inform users of the proper use, application, and installation of V-Couplings, which
6、will perform satisfactorily only if they are properly installed. This document informs the user of the correct manner of applying and installing V-Couplings and also cautions against improper use. 2. REFERENCES 2.1 Applicable Documents The following publications form a part of this document to the e
7、xtent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the issue in effect on the date of the purchase order. In the event of conflict between the text of this document and references cited herein, the text of this document takes
8、 precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. 2.1.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4
9、970 (outside USA), www.sae.org.AMS-W-6858 Welding, Resistance: Spot and Seam ARP699 High Temperature Pneumatic Duct Systems for Aircraft AS1701 Lubricant, Solid Film AS1895 Coupling Assembly, V-Retainer, High Pressure, High Temperature, Pneumatic Tube AS1960 Coupling Assembly, V-Band, Sheet Metal Fl
10、ange, Pneumatic Tube AS4108 T-Bolt and Eye Bolt, A-286 Cres, 1000 F Fatigue Rated AS4751 Coupling Assembly, V-Band, Sheet Metal Wide Flange, Pneumatic Tube SAE values your input. To provide feedbackon this Technical Report, please visit http:/www.sae.org/technical/standards/AIR869BCopyright SAE Inte
11、rnational Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR869B - 2 -AS5355 Couplings, Clamped, Grooved, V-Band AS24563 Coupling Flanges, V-Band, Profile Dimensions for 2.1.2 AIA/NAS Publications Available from Aerospace
12、Industries Association, 1000 Wilson Boulevard, Suite 1700, Arlington, VA 22209-3928, Tel: 703-358-1000, www.aia-aerospace.org.NASM7873 NUT, SELF-LOCKING, 1200 DEG F NASM25027 NUT, SELF-LOCKING, 250 DEG F, 450 DEG F, AND 800 DEG F2.2 Definitions CLAMP: The general category of special fasteners which
13、includes, V-Couplings, band clamps, and strap assemblies. V-BAND COUPLING: A sheet metal band clamp with sheet metal or machined retainer sections welded or riveted to the band or band loops (i.e., AS1960, AS4751). Also called V-Band Clamps. V-RETAINER COUPLINGS: Coupling with the V-retainer as an i
14、ntegral part of the coupling segment. V-Retainer Couplings have no band or straps. The latch components are attached to lugs on the retainer segments (i.e., AS1895). V-COUPLING: The family of V-Band Couplings and V-Retainer Couplings. V-COUPLING JOINT: The connection composed of a V-Coupling, mating
15、 flanges, and a seal when used. 2.3 Symbols Ag = Seal load, in psi B = Bolt nominal diameter, in inches Df = Flange outside diameter, in inches Dn = Coupling nominal diameter, in inches Dpl = Pitch line diameter, in inches (flange to retainer contact point, see Figure 1) Ds = Diameter at seal line o
16、r seal, in inches H = Hoop or circumferential band load, in pounds Kb = Number of bolts at each latch location Ga = Radial apex gap, in inches E = Axial load, in pounds Hs = Seal height, in inches Ls = Axial load to preload seal, in pounds M = Bending moment, in pounds-inches Copyright SAE Internati
17、onal Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR869B - 3 -Na = Axial tension load, in pounds per inch of circumference Nb = Axial force as a result of bending moments, in pounds per inch of circumference Np = Axial
18、force due to internal pressure, in pounds per inch of circumference N = Design load, in pounds per inch of circumference Ns = Seal seating load, in pounds per inch of circumference P = Internal pressure, psig T = Approximate design nut torque, in pounds-inches = V-Retainer angle, in degrees (commonl
19、y 40 degrees) 2.3.1 Subscripts c = coupling f = flange g = gasket b = bending moment pl = pitch line n = nominal p = pressure s = seal line or seal 3. V-COUPLING DESIGN FEATURES AND FACTORS V-Couplings are used to join two flanges together forming a V-Coupling Joint. The V-Coupling is tightened by a
20、pplying torque to a nut which tightens a circumferential band or band loops or an integral retainer and lugs exerting an inward radial force onto V-shaped retainer segments. These retainer segments then exert an axial clamping force onto the flanges, joining or pressing them together. V-couplings co
21、nsist of V-band couplings (Figures 2 and 3) and V-retainer couplings (Figure 4). V-Band Coupling design features are shown in Figures 2, 3, and 5. V-Retainer Coupling design features are shown in Figures 4 and 6. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo repr
22、oduction or networking permitted without license from IHS-,-,-SAE AIR869B - 4 -FIGURE 1 - LOCATION OF FLANGE TO REATINER CONTACT POINT (Dpl) FIGURE 2 - V-BAND COUPLING JOINT AND MACHINED FLANGES Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networ
23、king permitted without license from IHS-,-,-SAE AIR869B - 5 -FIGURE 3 - V-BAND COUPLING JOINT AND SHEET METAL FLANGES FIGURE 4 - V-RETAINER COUPLING JOINT AND MACHINED FLANGES 3.1 Design Loads and Torque The axial compressive clamping load that is generated by the application of nut torque must be s
24、ufficient to withstand design loads and the required seal load if used. These loads can be resolved into a load per unit of circumferential length at the flange to retainer contact point (Dpl Figures 2, 3, and 4) by the following formulas: Copyright SAE International Provided by IHS under license wi
25、th SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR869B - 6 -3.1.1 Seal Seating Load (Ns) a. Load-per-unit circumferential length, Ns, at pitch diameter, Dpl, may be given by the seal manufacturer. b. Or if total axial load, E, required to seal joint is g
26、iven, then: DplENs= (Eq. 1)c. Or with seal load per unit area Ag given: HsAgNs = (Eq. 2)(No consideration is given to the difference between actual diameter of seal and pitch diameter since it is relatively minor as diameters increase. The designer may account for it in the calculations if desired.)
27、 3.1.2 Design Total Load (N) a. As a result of internal pressure: Dpl4)Ds(PNp2= (Eq. 3)b. As a result of bending moment: 2)Dpl(M4Nb= (Eq. 4)c. As a result of axial tension load: DplENa= (Eq. 5)d. As a result of seal seating load, see 3.1.1. NOTE: N is a result of any one or the sum of all the preced
28、ing loads. NsNbNaNpN += (Eq. 6)N aids in the use of published clamp manufacturers “pressure curves“ which rate V-Couplings according to diameter and internal pressure loading only. If such curves are unavailable, consult the clamp manufacturer. 3.1.3 Design Nut Torque (T) The approximate design nut
29、torque in pound-inches is KbHB2.T = (Eq. 7)Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR869B - 7 -Neglecting friction between the retainers and flanges, the circumferential hoop load (H) in
30、 the band is 2TANNDplH= (Eq. 8)The recommended nut torque for the V-Coupling should be the approximate design nut torque given by the above calculation plus an allowance for the friction of the locknut. Since thread friction is often unpredictable, actual testing andreference to clamp manufacturers
31、recommended torque values is suggested. Locknut designs and thread lubricants will affect the design torque. Locknuts generally increase torque requirements while lubricants tend to decrease torque requirements. The correct installation torque is the torque that tightens the V-Coupling to the design
32、 apex gap between the flanges outside diameter and the retainers inside diameter. 3.1.4 Critical Installation Most pneumatic duct flange joints are critical in application because they contain high temperature gaseous fluid media. For such installations, the following are design recommendations. a.
33、Consider the operating temperature of the V-Coupling Joint when selecting materials. The more commonly used materials are: 1. 300 Series cres: 800 F max 2. A-286 cres: 1200 F max 3. Nickel alloys: 1200 F max All sheet metal V-Band Couplings, especially those operating at elevated temperature over 80
34、0 F, should have tangential band loops or wraps (see Figure 5) to prevent excessive relaxation and further straightening of the band resulting in reduced tightness of the latch. FIGURE 5 - V-BAND COUPLING Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction
35、 or networking permitted without license from IHS-,-,-SAE AIR869B - 8 -b. Recommended exclusively is the use of A-286 cres bolts per AS4108. This iron-based superalloy has been the preferred material for aerospace bolts and has been specified on the V-Couplings in AS1895, AS1960, AS4751, and AS5355.
36、c. The maximum load capacity of a V-Coupling is limited by the bending yield strength of the retainer segment at its apex corners. The combined forces of axial load, internal pressure, and bending loads apply this bending load on the retainer apex corners, see Figures 2, 3, and 4. The “burst pressur
37、e curves“ published by manufacturers relates to the yield point of the retainer at the maximum internal gas pressure only rated load as a function of seal diameter. The formulas which combine axial, bending, and pressure loads into an equivalent pressure only load to facilitate the use of the publis
38、hed pressure curves are in 3.1.2. Published maximum load rating curves apply only at room temperature. V-Couplings to be used at elevated temperatures must have their design load capability reduced by a correction factor (see applicable V-Coupling standard or supplier published data). d. Most V-Coup
39、lings have latches consisting of a T-bolt or eye bolt, trunnion, and locknut. Some of these bolts are defined in AS4108. Some V-Band Couplings have a quick-release latch which adds a hinged and slotted yoke that engages the bushing wrapped head of the T-bolt. Select the quick-release latch only when
40、 the V-Coupling is expected to be installed and removed frequently, or when quick installation and removal is necessary. T-bolts can only be replaced on quick-release latches and cannot be replaced on the basic T-bolt latch. Eyebolts can only be replaced by the manufacturer. Safety latches (secondar
41、y backup latch) are commonly used on V-Retainer Couplings (see Figure 6) and occasionally on V-Band Couplings. This is a redundant latch system that maintains joint integrity with reduced sealing in the event of the primary latch failure, which requires immediate replacement of the V-Coupling. FIGUR
42、E 6 - V-RETAINER COUPLING Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR869B - 9 -e. The majority of aerospace V-Couplings are tightened with an all metal self-locking nut. Such locknuts con
43、form to either NASM7873 or NASM25027. These locknuts have a limited number of installations and removal cycles on a bolt before excessive wear causes thread galling and seizure. The following recommended guidelines will promote successful use of all-metal locknuts on V-Couplings.1. Both the locknut
44、and bolt threads should be clean and free of dirt, burrs, and damaged threads. All stainless steel nuts should be silver plated or dry film lubricated, to prevent thread galling and seizure. 2. Installation of the locknut should not exceed 2 rps or 120 rpm. Installation with a hand torque wrench is
45、recommended. Excessive nut rotation speed causes frictional heat which promotes thread galling. 3. Lubricants greatly reduce the free running frictional resistance between locknuts and bolts. Dry film lubricants per AS1701 when applied to bolt threads have significantly increased thread life and red
46、uced galling. Antiseize thread lubricants have also been used with success. CAUTION: Use of lubricants on bolt threads can significantly affect torque/tension relationships. When a lubricant is used, the installation torque must be reduced accordingly to prevent excessive tightening that can damage
47、the clamp. f. Beware of excessive chlorine exposure to V-Couplings. The 300 series (austenitic) cres materials are very prone to stress corrosion cracking when exposed to excess chlorides. Nickel alloys such as 625, 718, K-400 and K-500 are recommended for excess chloride exposure. 3.1.5 Flange Conf
48、iguration and Seal Selection V-Couplings are used on two different kinds of flanges, solid machined flanges and flexible sheet metal flanges. Solid machined flanges are usually used on high strength applications such as bleed air connections on engines and on mechanical accessory connections. Sheet metal flanges are lighter weight flanges and are usually used on pneumatic ducting. All solid machined flanges in pneumatic systems require a separate seal that is either elastomeric or metallic to affec
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