Specifications Part 1 - Water Supply, Sewerage and Tube Well Works

Table 6.5Nominal DiaMinimum Test Duration in Minutes forBody Test Seat Test When Applicable.Upto and including 50 0.25 0.2565 to 150 1 1200 to 300 2 2350 to 1000 5 21200 to 2000 5 36.4.11 MarkingMarking shall be cast integral on the body or on a plate securely attached tothe body. The markings shall be in accordance with IS 9866 : 1981.6.6 Non return valve: (See Drawing No.-4)6.5.1 A device provided with a disc hinged on one edges so that it opens in thedirection of normal flow and closes with reversal of flow. Non return valve are 3types: 1 swing check type cast iron reflex valve. 2. Gun metal non return valve.3. Cast steel reflex valve.6.5.2 The reflux valves are swing type gate valves with a flap hinged at its top andthe flow in the forward direction causing the flap to swing open. The amount ofopening depends upon the velocity of flow and the weight of flap. With thedecrease of velocity, the opening reduces and it closes down preventing anyback flow during reversal of flow.6.5.3 The main consideration for the selection of reflux valve should always be that itshould not close down without heavy shock. If it closes with a shock it may leadto development of severe water hammer.6.5.4 Single check-type Reflux Valves (Cast iron):6.5.4.1 (Non-return valves) Single Door Pattern should conform to IS: 5312 (Part-I)6.5.4.2 General: The body, door, cover and hinge are of cast iron to IS: 1210. Bodyring, door faces, bearing bushes are of gun metal, hinge pins, door pins anddoor suspension pins are of high tensile brass or chromium steel (minimum 12% chrome) and air release plugs galvanized cast iron. Reflux valves shall bedesignated by nominal pressure (PN) defined as maximum permissible gaugepressure.6.5.4.3 Size of valve 50mm to 600mm.6.5.5. Swing check type reflux (non return valves) multi door pattern conforming to IS5312 (Part-2)6.5.5.1 Class of valves Class of reflux valves shall be designated by nominalpressure (PN), defined as the maximum permissible gauge working pressure inMPa as follows: PN 0.6 and PN 16.5.5.2 The materials used for the manufacture of different component parts of valvesshall conform to requirements given in table 6.6.Urban Administration & Development Department Page 71