AWWA C511-2007 Reduced-Pressure Principle Backflow Prevention Assembly《减压原则倒流防止器》.pdf

1、The Authoritative Resource for Safe WaterANSI/AWWA C511-07(Revision of ANSI/AWWA C511-97)AWWA StandardEffective date: Oct. 1, 2008.First edition approved by AWWA Board of Directors June 23, 1991.This edition approved June 24, 2007.Approved by American National Standards Institute July 24, 2008.Reduc

2、ed-Pressure Principle Backflow Prevention Assembly6666 West Quincy AvenueDenver, CO 80235-3098T 800.926.7337www.awwa.orgAdvocacyCommunicationsConferencesEducation and TrainingScience and TechnologySectionsiiAWWA StandardThis document is an American Water Works Association (AWWA) standard. It is not

3、a specification. AWWA standardsdescribe minimum requirements and do not contain all of the engineering and administrative information normallycontained in specifications. The AWWA standards usually contain options that must be evaluated by the user of thestandard. Until each optional feature is spec

4、ified by the user, the product or service is not fully defined. AWWApublication of a standard does not constitute endorsement of any product or product type, nor does AWWA test, certify,or approve any product. The use of AWWA standards is entirely voluntary. This standard does not supersede or takep

5、recedence over or displace any applicable law, regulation, or codes of any governmental authority. AWWA standardsare intended to represent a consensus of the water supply industry that the product described will provide satisfactoryservice. When AWWA revises or withdraws this standard, an official n

6、otice of action will be placed on the first page ofthe classified advertising section of Journal AWWA. The action becomes effective on the first day of the month followingthe month of Journal AWWA publication of the official notice.American National StandardAn American National Standard implies a co

7、nsensus of those substantially concerned with its scope and provisions. AnAmerican National Standard is intended as a guide to aid the manufacturer, the consumer, and the general public. Theexistence of an American National Standard does not in any respect preclude anyone, whether that person hasapp

8、roved the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or proceduresnot conforming to the standard. American National Standards are subject to periodic review, and users are cautionedto obtain the latest editions. Producers of goods made in conformity wit

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12、ced or transmitted in any form or by any means, electronicor mechanical, including photocopy, recording, or any information or retrieval system, except in the form of briefexcerpts or quotations for review purposes, without the written permission of the publisher. Copyright 2008 by American Water Wo

13、rks AssociationPrinted in USAiiiCommittee PersonnelThe AWWA Standards Committee on Backflow Preventers, which reviewed and approvedthis standard, had the following personnel at the time of approval:James T. Cowgill, ChairRichard A. Coates, SecretaryGeneral Interest MembersS.F. Asay, Drinking Water w

14、etted components shallalso comply with section 4.1.2.3. Ductile iron componentsASTM A395, ASTM A536; wetted compo-nents shall also comply with section 4.1.2.4. Elastomeric materialselastomeric components shall be rubber or ther-moplastic elastomers.5. Diaphragmsdiaphragms shall be rubber or thermopl

15、astic and capable ofwithstanding the performance requirements as detailed in this standard.6. Springsstainless steel (ASTM A313).7. Stainless steel componentsstainless steel alloys shall be ASTM A276UNS S30400, S30500, or S31600.8. Plastic componentsplastic components shall be suitable for waterserv

16、ice and capable of withstanding the performance requirements as detailed in thisstandard.9. Other alloys, rubbers, plastics, or other materials that are adaptable andwill give at least equivalent trouble-free service may be used if tested and foundequivalent. Brass alloys shall contain less than 15

17、percent zinc. Any alloy containingmore than 15 percent zinc shall be subject to a dezincification-resistant test perISO 6509 providing that the average depth of penetration shall not exceed 100 m.Sec. 4.2 General Design4.2.1 Size, rated flow, and allowable pressure loss.4.2.1.1 Nominal size. The siz

18、e of a backflow prevention assembly asindicated in Table 1 shall be identified by the size of inlet and outlet connection ofthe assembly.6 AWWA C511-074.2.1.2 Rated flow and allowable pressure loss. The maximum allowablepressure loss at any rate of flow, from zero and up to and including the maximum

19、rated flow for the indicated size, shall not exceed the values shown in Table 1.4.2.1.3 General flow and operating requirements. The water passagewaysshall be streamlined to minimize turbulence and pressure loss. Moving parts shall bedesigned to operate in a positive manner, without chatter. Differe

20、ntial pressure reliefvalves shall open and close positively and quietly and shall not “hunt” excessivelyunder normal fluctuations of flow rate or pressure. The design of the assembly shallbe such that it will not cause undue pressure surges during a cycle of operation, andthe operation of the assemb

21、ly shall not be impaired by the water-pressure surges thatare normally encountered in a water supply system. The assembly shall be sensitiveenough to react to pressure conditions without a time lag that would allow backflow.Table 1 Parameters for reduced-pressure principle backflow prevention assemb

22、lyNominal Size Maximum Rated Flow Maximum Allowable Pressure Lossin. (mm)*gpm (L/sec) psi (kPa)1/4 (6) 1(0.6 24 (165.4)3/8 (9) 3(19) 22 (151.6)1/2 (12) 7.5 (0.47) 22 (151.6)3/4 (19) 30 (1.89) 20 (137.88)1(25) 50 (3.15) 18 (124.09)11/4 (31) 75 (4.73) 18 (124.09)11/2 (38) 100 (6.31) 16 (110.30)2(50) 1

23、60 (10.10) 16 (110.30)21/2 (64) 225 (14.20) 16 (110.30)3(75) 320 (20.19) 15 (103.41)4 (100) 500 (31.55) 14 (96.51)6 (150) 1,000 (63.10) 14 (96.51)8 (200) 1,600 (100.96) 14 (96.51)10 (250) 2,300 (145.13) 14 (96.51)12 (305) 3,000 (189.30) 14 (96.51)*Metric conversions given in this standard are direct

24、 conversions of US customary units and are not those specified inInternational Organization for Standardization (ISO) standards.REDUCED-PRESSURE PRINCIPLE BACKFLOW PREVENTION ASSEMBLY 74.2.2 Structural and operational capability.4.2.2.1 Structural capability. The assembly shall be capable of withsta

25、ndingan internal hydrostatic test pressure of twice the maximum working pressure of theassembly for 10 min without leakage. The check valves shall withstand abackpressure, with atmospheric pressure on the inlet side, of twice the maximumrated working pressure of the assembly without leakage.4.2.2.2

26、Operational capability. The assembly shall be capable of goingthrough a full cycle of operation, during which the operating pressure on the inlet sideof the assembly drops sharply from 150 psi (1,034 kPa) to atmospheric pressure andreturns slowly after a short time interval to 150 psi (1,034 kPa) wi

27、thout permanentdistortion or damage to any of its parts. The backflow preventer assemblies shallwithstand a flow of 150 percent of the flows in Table 1 for 10 min without damage.Sec. 4.3 Detailed Design4.3.1 Design of assembly. It is essential that assemblies be trouble-free; thatmoving parts do not

28、 bind or gall; and that there be no distortion that will interferewith the intended performance of the assembly. Flow channels shall be streamlined toprevent cavitation, minimize pressure loss, and eliminate pockets that could entrapforeign materials.4.3.1.1 Access to internal parts. Internal wetted

29、 parts shall be accessible forinspection, repair, and renewal, without disturbing either the structural integrity ofthe piping system or the integrity of the shutoff valves used to isolate the backflowpreventer, by the removal of the assembly from the line using the shutoff valves toisolate the asse

30、mbly.4.3.1.2 Connections. End connections, test cocks, and control pipingconnections to components of the backflow prevention assembly shall be eitherthreaded, in accordance with ASME B1.20.1, or flanged, in accordance with ASMEB16.1, ASME B16.24, or ANSI/AWWA C110/A21.10, or grooved and shoulderedj

31、oints per ANSI/AWWA C606.4.3.1.3 Test cocks. Resilient-seated, full-ported test cocks shall be attachedto corrosion-resistant nipples or have male threads to be installed in tapped holes. Ateach location on a valve body where such a tapped hole is required, there shall be aboss to permit sufficient

32、threading for nipples. Test cocks shall have female iron pipesize (IPS) ends on the discharge side. Test connections of 1/8 in. (3 mm) shall bepermitted to be either IPS female threads or male 1/4 in. (6 mm) flared-typeconnections per SAE J513. The minimum sizes (IPS) of test cocks shall be 1/8 in.8

33、 AWWA C511-07(3 mm) for assemblies up to and including 1-in. (25-mm) nominal size; 1/4 in.(6 mm) for assemblies up to and including 2-in. (50-mm) nominal size; 1/2 in.(12 mm) for assemblies 21/2-in. through 4-in. (64-mm through 100-mm) nominalsize; and 3/4 in. (19 mm) for assemblies 6 in. (150 mm) a

34、nd larger. Test cocks shallbe installed at the following locations on backflow prevention assemblies:1. On the supply (inlet) side of the supply shutoff valve.NOTE: The #1 test cock is not required for the 1/4 in. and 3/8 in. sizeassemblies.2. Between the supply shutoff valve and the first check val

35、ve.3. Between the check valves.4. Between the second check valve and the shutoff valve on the outlet side ofthe assembly.4.3.1.4 Control piping. Control piping and passageways shall be ofcorrosion-resistant material.4.3.1.5 Valve seats. Provision shall be made for renewal and replacement ofvalve sea

36、ts.4.3.1.6 Alignment of check valves. Each clapper disc, facing ring, andclamping and securing bolt or stud shall be concentric to an axis that is normal to theface of the facing ring. When applicable, the unit shall be designed so that the facingring may be clamped and reclamped without warping its

37、 face. The clapper must notbe able to tip and catch under the seat ring. When clappers or poppets are in a wide-open position, they must bear on a definite stop that is so designed and placed thatthe action of the water will not twist or bend the valve parts or cause them to chatter.The design shall

38、 be such that at any flow rate, from zero to (and including) ratedflow, the component parts shall not create any chatter or noise. Working parts shallbe designed and supported in a manner to preclude distortion or misalignment.4.3.1.7 Shutoff valves. Shutoff valves shall be resilient seated. Shutoff

39、 valvesshall be considered an integral part of the assembly and shall meet the material andhydraulic requirements of this standard. Shutoff valves shall meet the appropriaterecognized standards of AWWA. Shutoff valves on assemblies for fire protectionservice shall meet the appropriate recognized sta

40、ndards of UL and FM.4.3.2 Operating requirements for reduced-pressure principle backflow preventionassembly.4.3.2.1 Normal conditions. During normal operating conditions, whetheror not there is flow through the assembly, the pressure in the zone between the checkREDUCED-PRESSURE PRINCIPLE BACKFLOW P

41、REVENTION ASSEMBLY 9valves shall be at least 2 psi (13.8 kPa) less than the pressure on the supply (inlet) sideof the assembly.4.3.2.2 No flow from the supply side. When there is no flow from thesupply side of the assembly and the supply pressure drops to 2 psi (13.8 kPa), thepressure within the zon

42、e shall be atmospheric. As the supply pressure drops below2 psi (13.8 kPa), the relief valve shall continue to open and shall reach and maintainthe fully open position as the supply pressure drops to atmospheric or lower.4.3.2.3 Differential pressure relief valve discharge rates. When the down-strea

43、m pressure approaches within 0.5 psi (3.44 kPa) of the supply pressure, with thechecking member of the second check valve physically removed and the supplypressure at least equal to the rated water working pressure of the assembly, the reliefvalve shall discharge water from the zone to the atmospher

44、e with the rate of dischargecorresponding to the data shown in Table 2.Table 2 Pressure differential relief valve discharge ratesNominal Size of Assembly Relief Valve Discharge Rate*These are minimum discharge rates at which the capability of the relief valve to maintain zone pressure specifiedin Se

45、c. 4.3.2, paragraphs 4.3.2.3 and 4.3.2.4, are measured.in. (mm) gpm (L/sec)1/4 (6) 0.5 (0.03)3/8 (9) 1 (0.06)1/2 (12) 3 (0.19)3/4 (19) 5 (0.32)1(25 5 (0.32)11/4 (31) 10 (0.63)11/2 (38) 10 (0.63)2(50 20 (1.26)21/2 (64) 20 (1.26)3(75 30 (1.89)4 (100) 40 (2.52)6 (150) 40 (2.52)8 (200) 60 (3.78)10 (250)

46、 60 (3.78)12 (305) 75 (4.73)10 AWWA C511-074.3.2.4 Downstream pressure exceeds the supply pressure of 0 psi. When thedownstream pressure exceeds the atmospheric supply pressure and the second checkvalve is held fully open or removed, the relief valve shall discharge water from thezone to the atmosph

47、ere with a rate of discharge corresponding to the data shown inTable 2. The pressure in the zone shall not exceed 1.5 psi (10.34 kPa) during the test.4.3.2.5 Outlet check valve pressure. The outlet check valve shall be inter-nally loaded so that when the pressure on the inlet side of the valve is at

48、 least 1 psi(6.89 kPa) and the outlet pressure is atmospheric, the valve will be drip-tight in thenormal direction of flow.4.3.2.6 Inlet check valve pressure. To prevent excessive discharge caused bypressure fluctuation, the minimum pressure differential across the first check valveunder normal cond

49、itions shall be at least 3 psi (20.7 kPa) greater than the pressuredifferential necessary to cause the relief valve to open.4.3.2.7 Discharge port. The discharge port of the relief valve shall be of suchdesign as to restrict the attachment of a hose, pipe, or plate.4.3.2.8 Differential pressure relief valve location. The manufacturer shallinclude with each unit installation instructions, attached to the unit, to designate thatthe relief valve and relief valve discharge port shall be low enough to drain theintermediate “zone” chamber of the reduced-pressure principle assembly to the