2.5 MAINTENANCE POST FLUSHING a- At the end of flushing operation it may be possible to leave the line full of test fluid and in this case no intervention is required. If the line must be drained proceed as follows: • Make sure that the valve is in full open position. • Open plugs and drain it completely. Observe safety plant procedures prior to opening any body plugs in case any remaining fluid or gas is pressurised or trapped in body cavities. • After draining flush the cavity of valve through the vent plug. Consult an expert on use of special excavation procedures. • Lubricate the stem with fluid protective oil or grease through the injector (if applicable). (Seat lubrication is only for emergency purposes not for ongoing maintenance). • Completely tighten all drain and vent plugs. Consult your plant safety procedures and only perform work under supervision of expert valve maintenance personnel. b- Operate the valve at least 2 times (complete closing and opening operation). c- Repeat the operation every 6 months if the pipeline is not used. d- Always get authorisation to partially operate an in-service valve. Australian Pipeline Valve - Installation, Operation and Maintenance Manual 12 EXPANDING SEAL PLUG VALVE DOUBLE BLOCK & BLEED API6D - TWIN SERIES Natural gas is not usually clean. Natural gas may carry condensates and dirt that gets trapped in the valves, and may damage the internal parts. Also, operation of the valves becomes more difficult. It is true that plant sites do install filters in their system, but experience has proven that no system is perfect. The internal parts of the valve can be partially protected using judicious amounts of grease to fill the cavities. However, other than when flushing or if there is seat leakage, or if valve cannot be opened, no grease should be applied via seat sealant injectors to soft seats as it will attract debris and cause damage. A soft seated valve is always at risk if service is not clean. Personal injury may result from sudden release of any process pressure. APV recommends the use of protective clothing, gloves and eyewear when performing any installation or maintenance. Isolate the valve from the system and relieve pressure prior to performing maintenance. Never unscrew sealant injection nipples from body, seats or stem as these outlets are exposed to full line pressure and only the in-built check valve in the sealant nipple itself isolates the pressure. Similarly, the body drain and vent valve plugs are exposed to full line pressure if opened. Disconnect any operating lines providing air pressure, control signals or electrical power to actuators.