SIDE ENTRY 2P TRUNNION BALL VALVES API6D STANDARD - FS9000 SERIES
Australian Pipeline Valve - Installation, Operation and Maintenance Manual
9
necessary, is the most dangerous activity for the valves, and it happens before they are put to service.
Whilst ball valves are normally not lubricated, should it be required to flush potential debris (or lubricate
sticky valves) a different practise to the lubrication of either a gate valve or plug valve should be
employed. We recommend the following: -
1. Find a good grease for natural gas or your service. The grease must be insoluble. It must be resistant to
breakdown or shearing of the gel structure under high pressure injection and under the pressure
between seating surfaces. It must be stable over a wide range of temperatures, and not freeze. It must
not react chemically with the fluid and become solid, or rubber like (i.e. polymerize). Depending on the
service, the best greases are fully synthetic; if you have any doubt or concern, consult a valve
maintenance expert. Field experience has shown that greases and sealants may cause severe problems
with the seat and seal arrangement if used regularly during preventative maintenance. If a non-leaking
ball valve is lubricated with an adhesive grease/sealant, the floating, spring loaded seats can become
stuck within their seat pockets. When the ball floats due to a pressure differential across the valve, the
seals cannot track the ball and leakage can occur. Grease manufacturers produce low viscosity
synthetic ball valve lubricants such as Clare UK “601-Fluid”. Such light greases offer the following
advantages to heavier emergency sealant greases and cheaper brands of light greases: -
• Enhanced resistance to hydrocarbon fluids and gases.
• Will not dry out or form a gum like some other greases when used within its application temperature
range.
• Will not disrupt the operation of the seat and seal arrangement.
2. Use an appropriate high pressure grease-injection pump, capable of overcoming the pipe pressure and
the high pressure build-up caused by the grease itself, during it’s injection in the grease passages.
3. Inject a generous amount of grease in the seats before flushing. The object is to cover them all and to
fill the groove between seat carrier and ball with grease. The dirt will get stuck to the grease during
flushing, but it will not come inside. And before turning the valve for the first time, inject again a small
amount of grease into the seats. A little is enough (1/4 of the normal quantity per seat, see 8.4.1). The
dirty grease will be pushed into the pipe by the fresh grease, and the turning action of the ball will
drag fresh grease towards the seats, not dirty grease.
4. Do not turn the valve during flushing.
Of course, be warned any type of grease, especially synthetic grease can become hard or sticky
causing torque problems and seat spring jamming in which case a line flushing agent like Clare 601
Valve Cleaner may be required. Of course, for leaking seats a heavier sealant like Clare 601 lubricant
must be used for temporary emergency sealing.
Beware of greases made of synthetic oil with a mineral thickener. The natural gas
(or storage prior to use) washes away the oil, leaving the thickener behind. The
thickener is like a powder that caulks or bakes hard on the seats, increasing the
operating torque. Always wipe the seats clean as much as possible prior to
installation. The increased torque may effect pneumatic actuated valves.
