Butterfly Valves. Features of Construction The valves shall be manufactured with integral body seats, suitable for open-closed and throttling service. Each valve shall be capable of withstanding the rated pressure from either side. Leakage rates shall not exceed 3.6cc/hr/cm of nominal valve diameter. The valves shall be furnished with double flanged ends. The valves, where specified or shown on the Drawings, shall be manually operated with gear box and hand wheel and shall be furnished with extension spindles. The extension spindle shall be furnished with a universal coupling and intermediate supports. Butterfly Valves to be installed shall be of the metal seated type generally as per BS EN 593. Valves shall be suitable for mounting in any position. The valve seat shall be of integrally cast and of replaceable design. When the valve is fully closed, the seal shall seat firmly. The seat surfaces shall be machined smooth to provide a long life for the seal. All fasteners shall be set flush so as to offer the least possible resistance to the flow through the valve. All valves shall be suitable for throttling purpose. All valve spindles and hand wheels shall be positioned to give good access for operational personnel. Valve of diameter 400 mm and above shall be provided with an enclosed gear arrangement for ease of operation. The gearing shall be such that the valve can be opened and closed by one man against an unbalanced head of 1.15 times the specified rating. Valve and gearing shall be such as to permit manual operation in a reasonable time and not exceed a required rim pull of 80 N. All hand wheels shall be arranged to turn in a clockwise direction to close the valve, the direction of rotation for opening and closing being indicated on the hand wheels. Butterfly valves conforming to IS 13095 or equivalent International standard are acceptable. Pressure rating for the butterfly valves to be installed in the distribution network shall be as specified in Table 5-1. Table 5-1 Pressure Ratings for Butterfly Valves Service Pressure Rating Operating Pressure (MPa) Body Test Pressure (MPa) Distribution lines PN 1.6 1.6 2.4
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Samples: gmdwsb.assam.gov.in, gmdwsb.assam.gov.in, gmdwsb.assam.gov.in
