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.
