Australian Pipeline Valve - Installation, Operation and Maintenance Manual 20 API6D THROUGH CONDUIT EXPANDING GATE VALVE - AP400-405 SERIES 8.5.1 a- Operate the valve to the CLOSED position. b- CLOSE upstream drain valve, tightly. c- Make sure the drain valve (see before drain) is in the OPEN position. d- Double check the valves again to insure they are in the proper position. e- Lightly loosen the body bleed fitting plunger (‘B’ below) to allow slow release of pressure from the cavity. Please make sure all persons are clear of the fitting opening during venting. Pressure will begin to decrease and flow will lessen as valve body pressure is released. Note If pressure does not bleed down, CLOSE fitting (‘B’ below) and operate valve again to the CLOSE position to insure proper closure. Reopen fitting (‘B’ below) and allow pressure to finish venting. Use extreme caution when venting the body cavity of a pressurised valve. If the body cavity keeps venting fluid at a constant flow rate for a very long time, it is a signal of bad sealing of the valve seats. For liquid service only a lower drain valve will immediately indicate a leak.