AWWA C510-17 pdf download.Double Check-Valve Backflow Prevention Assembly
4.1.1 Dissimilar metals. In the presence of an electrolyte, direct contact between metals of dissimilar corrosion resistance may result in galvanic corrosion of the more active, less corrosion-resistant material. When dissimilar metals must be used for internal parts, the rate of corrosion shall be reduced as much as practical through the selection of materials that exhibit similar resistance to corrosion by plac- ing a dielectric material between the metals or by applying a dielectric coating. When contact between dissimilar metals cannot be avoided, the assembly shall be designed so that the resulting corrosion will be minimized and will not adversely afect water quality or result in malfunctioning or premature failure of the assembly.
4.1.2 Protective coatings. Ferrous bodies and parts shall be coated with a polymerized coating. Te protective coating shall be composed of materials refer- enced in ANSI/AWWA C550 as deemed acceptable in the Food and Drug Admin- istration (FDA) Document, Title 21, Food and Drugs, Code of Federal Regulations, Sec. 175.300. Te manufacturer shall provide documentation verifying compli- ance with this document or NSF/ANSI 61 when requested by the purchaser.
4.1.3.1.1 Bronze components shall be made to ASTM-recognized alloy specifcations with metal and alloys in the unifed numbering system (UNS)* des- ignations. Bronze alloys are not limited to those specifed in this standard. Bronze alloys, however, must meet the performance requirements of this standard, includ- ing but not limited to minimum yield strength, chemical requirements, and cor- rosion resistance.
4.2.1.2 Rated fow and allowable pressure loss. Te maximum allowable pressure loss at any rate of fow, from zero and up to and including the maximum rated fow for the indicated size, shall not exceed the values shown in Table 1.
4.2.1.3 General fow and operating requirements. Te water passageways shall be streamlined to minimize turbulence and pressure loss. Moving parts shall be designed to operate in a positive manner, without chatter. Te design of the assembly shall be such that it will not cause 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. Te assem- bly shall be sensitive enough to react to pressure conditions without a time lag that would allow backfow.AWWA C510-17 pdf download.