AWWA C508:2001 pdf download.SWING-CHECK VALVES FOR WATERWORKS SERVICE, 2-IN. THROUGH 24-IN. (50-mm THROUGH 600-mm) NPS
4.4.1 General. All check valves shall be designed to prevent any permanent distortion of the body, cover, or seats and to avoid any strain upon the seats that would be sufficient to force them out of alignment when under test pressure as specifed in Sec. 5.2.
4.4.2 Closure assembly. The closure assembly shall be designed to assume the closed position by gravity under no-flow conditions in a horizontal pipeline.
4.4.3 Accessibility of internal parts. Internal working parts shall be readily accessible and shall be replaceable without the use of special tools and without removing the valve body from the pipeline.
4.4.4 Disc/hinge assembly stop. When the check valve is wide open, the disc/ :hinge assembly shall bear against a definite stop. The point of contact is located so that any impact or loading applied by water flow will tend not to twist or bend disc parts. If this stop is located on the cover, the cover shall be designed to prohibit improper assembly in the event of repairs.
4.4.5 Net-flow area. Swing-check valves, when fully open, shall have a net-flow area not less than the area of a circle with a diameter equal to the nominal pipe size.
4.4.6.1 Flanged ends. The end flanges of flanged valves shall conform to dimensions and drillings of ANSIASME B16.1 class 125 or ANSIAWWA C110/ A21.10 unless explicitly provided otherwise in the purchaser's specifications. Unless spot-facing is required by the purchaser's specifications, the bolt holes of the end flanges shall not be spot-faced except when the thickness at any point within the spot- face area, as defined in MSS SP-9, exceeds the required minimum thickness of ANSIASME B16.1 by the excess thickness tolerance as shown in Table 2 or exceeds the maximum thickness of AWWA C110. If the foregoing limit is exceeded, either spot-facing or back facing may be used to meet the requirements. When required, all spot- facing shall be done in accordance with MSS SP-9. Bolt holes shall straddle the vertical centerline of the valve, unless otherwise specified by the purchaser.AWWA C508 pdf download.