Australian Pipeline Valve - Installation, Operation and Maintenance Manual 18 EXPANDING SEAL PLUG VALVE DOUBLE BLOCK & BLEED API6D - TWIN SERIES 7 . 0 M A I N T E N A N C E In cold climates before freezing weather sets in, any possible collection of water below plug or plug trunnion should be drained out through drain plugs (No. 14) Check manual body bleed (no. 23) for zero pressure before removing plugs. If, at any time, the manual body bleed should indicate an upstream leak which cannot be stopped by ordinary hand force on the handwheel, this must be corrected by one of the following: a. Operate valve through open - close cycle while fluid is flowing, to try flush out valve body. After several flushing attempts, close valve and check body bleed again. If body bleed still indicates valve leak, check thermal relief assembly before replacing seating slips. b. To replace seating slips, the line must be drained. Place valve in open position (check body bleed for zero line pressure); then remove lower plate (No. 16) or bonnet (No. 8. APV has both top and bottom entry to facilitate in-line maintenance. c. Seating slips (No. 13) can be withdrawn from plug dovetails and replaced. It is usually best to replace the gasket (No. 11) and lower plate o-ring (No. 10) or bonnet “O” ring (No. 10) when slips are replaced. If stem packing should fail, it can be changed as follows: a. Close valve and check body bleed for upstream shut off. Leave body bleed open. If valve is holding tight, then packing can be changed under line pressure. If body bleed shows the valve is not holding upstream, then the line must be bled down in order to proceed with the change. b. Remove operator as outlined below. c. Remove packing gland (No. 5) and replace inner and outer o-rings (Nos. 3 & 4). d. Remove packing rings (No. 5) carefully and replace. e. Replace operator as outlined below. 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.