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1、The Authoritative Resource for Safe Water ANSI/AWWA C511-07 (Revision of ANSI/AWWA C511-97) AWWA Standard Effective 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, 200
2、8. Reduced-Pressure Principle Backflow Prevention Assembly 6666 West Quincy Avenue Denver, CO 80235-3098 T 800.926.7337 www.awwa.org Advocacy Communications Conferences Education and Training Science and Technology Sections ii AWWA Standard This document is an American Water Works Association (AWWA)
3、 standard. It is not a specification. AWWA standards describe minimum requirements and do not contain all of the engineering and administrative information normally contained in specifications. The AWWA standards usually contain options that must be evaluated by the user of the standard. Until each
4、optional feature is specified by the user, the product or service is not fully defined. AWWA publication 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 d
5、oes not supersede or take precedence over or displace any applicable law, regulation, or codes of any governmental authority. AWWA standards are intended to represent a consensus of the water supply industry that the product described will provide satisfactory service. When AWWA revises or withdraws
6、 this standard, an official notice of action will be placed on the first page of the classified advertising section of Journal AWWA. The action becomes effective on the first day of the month following the month of Journal AWWA publication of the official notice. American National Standard An Americ
7、an National Standard implies a consensus of those substantially concerned with its scope and provisions. An American National Standard is intended as a guide to aid the manufacturer, the consumer, and the general public. The existence of an American National Standard does not in any respect preclude
8、 anyone, whether that person has approved the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not conforming to the standard. American National Standards are subject to periodic review, and users are cautioned to obtain the latest editions. Pro
9、ducers of goods made in conformity with an American National Standard are encouraged to state on their own responsibility in advertising and promotional materials or on tags or labels that the goods are produced in conformity with particular American National Standards. CAUTION NOTICE:The American N
10、ational Standards Institute (ANSI) approval date on the front cover of this standard indicates completion of the ANSI approval process. This American National Standard may be revised or withdrawn at any time. ANSI procedures require that action be taken to reaffirm, revise, or withdraw this standard
11、 no later than five years from the date of publication. Purchasers of American National Standards may receive current information on all standards by calling or writing the American National Standards Institute, 25 West 43rd Street, Fourth Floor, New York, NY 10036; (212) 642-4900. All rights reserv
12、ed. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information or retrieval system, except in the form of brief excerpts or quotations for review purposes, without the written permission of th
13、e publisher. Copyright 2008 by American Water Works Association Printed in USA -,-,- iii Committee Personnel The AWWA Standards Committee on Backflow Preventers, which reviewed and approved this standard, had the following personnel at the time of approval: James T. Cowgill, Chair Richard A. Coates,
14、 Secretary General Interest Members S.F. Asay, Drinking Water wetted components shall also 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- moplas
15、tic elastomers. 5.Diaphragmsdiaphragms shall be rubber or thermoplastic and capable of withstanding the performance requirements as detailed in this standard. 6.Springsstainless steel (ASTM A313). 7.Stainless steel componentsstainless steel alloys shall be ASTM A276 UNS S30400, S30500, or S31600. 8.
16、Plastic componentsplastic components shall be suitable for water service and capable of withstanding the performance requirements as detailed in this standard. 9.Other alloys, rubbers, plastics, or other materials that are adaptable and will give at least equivalent trouble-free service may be used
17、if tested and found equivalent. Brass alloys shall contain less than 15 percent zinc. Any alloy containing more than 15 percent zinc shall be subject to a dezincification-resistant test per ISO 6509 providing that the average depth of penetration shall not exceed 100 m. Sec. 4.2General Design 4.2.1S
18、ize, rated flow, and allowable pressure loss. 4.2.1.1Nominal size.The size of a backflow prevention assembly as indicated in Table 1 shall be identified by the size of inlet and outlet connection of the assembly. -,-,- 6AWWA C511-07 4.2.1.2Rated flow and allowable pressure loss.The maximum allowable
19、 pressure loss at any rate of flow, from zero and up to and including the maximum rated flow for the indicated size, shall not exceed the values shown in Table 1. 4.2.1.3General flow and operating requirements.The water passageways shall be streamlined to minimize turbulence and pressure loss. Movin
20、g parts shall be designed to operate in a positive manner, without chatter. Differential pressure relief valves shall open and close positively and quietly and shall not “hunt” excessively under normal fluctuations of flow rate or pressure. The design of the assembly shall be such that it will not c
21、ause undue pressure surges during a cycle of operation, and the operation of the assembly shall not be impaired by the water-pressure surges that are normally encountered in a water supply system. The assembly shall be sensitive enough to react to pressure conditions without a time lag that would al
22、low backflow. Table 1Parameters for reduced-pressure principle backflow prevention assembly Nominal SizeMaximum Rated FlowMaximum Allowable Pressure Loss in.(mm)*gpm(L/sec)psi(kPa) 1/4 (6)1(0.06)24(165.4) 3/8 (9)3(0.19)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(1
23、24.09) 11/4(31)75(4.73)18(124.09) 11/2(38)100(6.31)16(110.30) 2(50)160(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 conver
24、sions given in this standard are direct conversions of US customary units and are not those specified in International Organization for Standardization (ISO) standards. -,-,- REDUCED-PRESSURE PRINCIPLE BACKFLOW PREVENTION ASSEMBLY7 4.2.2Structural and operational capability. 4.2.2.1Structural capabi
25、lity.The assembly shall be capable of withstanding an internal hydrostatic test pressure of twice the maximum working pressure of the assembly for 10 min without leakage. The check valves shall withstand a backpressure, with atmospheric pressure on the inlet side, of twice the maximum rated working
26、pressure of the assembly without leakage. 4.2.2.2Operational capability.The assembly shall be capable of going through a full cycle of operation, during which the operating pressure on the inlet side of the assembly drops sharply from 150 psi (1,034 kPa) to atmospheric pressure and returns slowly af
27、ter a short time interval to 150 psi (1,034 kPa) without permanent distortion or damage to any of its parts. The backflow preventer assemblies shall withstand a flow of 150 percent of the flows in Table 1 for 10 min without damage. Sec. 4.3Detailed Design 4.3.1Design of assembly.It is essential that
28、 assemblies be trouble-free; that moving parts do not bind or gall; and that there be no distortion that will interfere with the intended performance of the assembly. Flow channels shall be streamlined to prevent cavitation, minimize pressure loss, and eliminate pockets that could entrap foreign mat
29、erials. 4.3.1.1Access to internal parts.Internal wetted parts shall be accessible for inspection, repair, and renewal, without disturbing either the structural integrity of the piping system or the integrity of the shutoff valves used to isolate the backflow preventer, by the removal of the assembly
30、 from the line using the shutoff valves to isolate the assembly. 4.3.1.2Connections.End connections, test cocks, and control piping connections to components of the backflow prevention assembly shall be either threaded, in accordance with ASME B1.20.1, or flanged, in accordance with ASME B16.1, ASME
31、 B16.24, or ANSI/AWWA C110/A21.10, or grooved and shouldered joints per ANSI/AWWA C606. 4.3.1.3Test cocks.Resilient-seated, full-ported test cocks shall be attached to corrosion-resistant nipples or have male threads to be installed in tapped holes. At each location on a valve body where such a tapp
32、ed hole is required, there shall be a boss to permit sufficient threading for nipples. Test cocks shall have female iron pipe size (IPS) ends on the discharge side. Test connections of 1/8 in. (3 mm) shall be permitted to be either IPS female threads or male 1/4 in. (6 mm) flared-type connections pe
33、r SAE J513. The minimum sizes (IPS) of test cocks shall be 1/8 in. 8AWWA 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 10
34、0-mm) nominal size; and 3/4 in. (19 mm) for assemblies 6 in. (150 mm) and larger. Test cocks shall be 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. s
35、ize assemblies. 2.Between the supply shutoff valve and the first check valve. 3.Between the check valves. 4.Between the second check valve and the shutoff valve on the outlet side of the assembly. 4.3.1.4Control piping.Control piping and passageways shall be of corrosion-resistant material. 4.3.1.5V
36、alve seats.Provision shall be made for renewal and replacement of valve seats. 4.3.1.6Alignment of check valves.Each clapper disc, facing ring, and clamping and securing bolt or stud shall be concentric to an axis that is normal to the face of the facing ring. When applicable, the unit shall be desi
37、gned so that the facing ring may be clamped and reclamped without warping its face. The clapper must not be 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 that the action of the water
38、will not twist or bend the valve parts or cause them to chatter. The design shall be such that at any flow rate, from zero to (and including) rated flow, the component parts shall not create any chatter or noise. Working parts shall be designed and supported in a manner to preclude distortion or mis
39、alignment. 4.3.1.7Shutoff valves.Shutoff valves shall be resilient seated. Shutoff valves shall be considered an integral part of the assembly and shall meet the material and hydraulic requirements of this standard. Shutoff valves shall meet the appropriate recognized standards of AWWA. Shutoff valv
40、es on assemblies for fire protection service shall meet the appropriate recognized standards of UL and FM. 4.3.2Operating requirements for reduced-pressure principle backflow prevention assembly. 4.3.2.1Normal conditions.During normal operating conditions, whether or not there is flow through the as
41、sembly, the pressure in the zone between the check REDUCED-PRESSURE PRINCIPLE BACKFLOW PREVENTION ASSEMBLY9 valves shall be at least 2 psi (13.8 kPa) less than the pressure on the supply (inlet) side of the assembly. 4.3.2.2No flow from the supply side.When there is no flow from the supply side of t
42、he assembly and the supply pressure drops to 2 psi (13.8 kPa), the pressure within the zone shall be atmospheric. As the supply pressure drops below 2 psi (13.8 kPa), the relief valve shall continue to open and shall reach and maintain the fully open position as the supply pressure drops to atmosphe
43、ric or lower. 4.3.2.3Differential pressure relief valve discharge rates.When the down- stream pressure approaches within 0.5 psi (3.44 kPa) of the supply pressure, with the checking member of the second check valve physically removed and the supply pressure at least equal to the rated water working
44、pressure of the assembly, the relief valve shall discharge water from the zone to the atmosphere with the rate of discharge corresponding to the data shown in Table 2. Table 2Pressure differential relief valve discharge rates Nominal Size of AssemblyRelief Valve Discharge Rate* *These are minimum di
45、scharge rates at which the capability of the relief valve to maintain zone pressure specified in Sec. 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
46、/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)60(3.78) 12(305)75(4.73) -,-,- 10AWWA C511-07 4.3.2.4Downstream pressure exceeds the supply pressure of 0 psi.When the downstream pressure exceeds the atmospheric supply pressure and the second check valve is held fully
47、 open or removed, the relief valve shall discharge water from the zone to the atmosphere with a rate of discharge corresponding to the data shown in Table 2. The pressure in the zone shall not exceed 1.5 psi (10.34 kPa) during the test. 4.3.2.5Outlet check valve pressure.The outlet check valve shall
48、 be inter- nally loaded so that when the pressure on the inlet side of the valve is at least 1 psi (6.89 kPa) and the outlet pressure is atmospheric, the valve will be drip-tight in the normal direction of flow. 4.3.2.6Inlet check valve pressure.To prevent excessive discharge caused by pressure fluc
49、tuation, the minimum pressure differential across the first check valve under normal conditions shall be at least 3 psi (20.7 kPa) greater than the pressure differential necessary to cause the relief valve to open. 4.3.2.7Discharge port.The discharge port of the relief valve shall be of such design as to restrict the attachment of a hose, pipe, or plate. 4.3.2.8Differential pressure relief valve location.Th