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below reservoir pressure the valve opens, allowing reverse <br /> flow from the reservoir and thus maintaining fluid pressure <br /> within the water distribution system. <br /> C. The altitude control valve(s) shall be of the size and type <br /> indicated on the Contract drawings and as manufactured by <br /> GA Industries or approved equal. <br /> I. Surge Relief Valve: <br /> 1. Surge relief valves shall be hydraulically operated, pilot actuated <br /> globe valves. The valve shall open when system pressure exceeds <br /> its pressure setting and throttle as necessary to limit system <br /> pressure to a pre-set maximum pressure. When pressure subsides <br /> below the pre-set maximum the valve shall close tight. The valve <br /> shall be constructed with integral ANSI 125 lb drilled flanges with a <br /> rated pressure of 250 psi, full ported globe body design. The main <br /> valve shall be serviceable without removal from the line through a <br /> flanged cover, which provides access to internal components. <br /> 2. The valve shall be constructed of heavy cast or ductile iron body, <br /> conforming to ASTIVI specification A-126 Class B with bronze or <br /> stainless steel trim. The bronze ports shall conform to ASTM <br /> specification B-62. All ferrous surfaces shall be coated with NSF <br /> certified epoxy, conforming to AWWA D1.02. The surge relief valve <br /> shall be fully bronze mounted, external pilot operated, with a rugged <br /> internal free floating piston (operated without springs, diaphragm or <br /> levers), single seat with seat bore equal to the size of the valve. <br /> 3. For true alignment of the piston (to correct lateral thrust and stem <br /> binding) the piston shall be guided above and below the seat a <br /> distance no less than 75% of the seat diameter. The piston shall <br /> carry a contoured cushion device that will cause a gradual change in <br /> flow area as the valve approaches the seat. <br /> 4. The main valve shall include a position indicator to show the position <br /> of opening of the piston, adjustable, independent, opening and <br /> closing speed control valves, a cam operated limit switch, strainer, <br /> gauge cocks for testing purposes, and solenoid pilot valves with a <br /> manual operator. <br /> 5. The system shall have a normally closed, direct-acting, diaphragm <br /> operated, spring loaded bronze pressure relief pilot that is field <br /> adjustable from zero to a minimum of 10% above the factory setting. <br /> The pilot valve, controlling operation of the main valve, shall have a <br /> range for adjustment, be easily accessible and so arranged to allow <br /> Rev. 10122101 PROJECT#13.01126 02640-Page 8 <br />