8.4 MAINTENANCE SCHEDULE
ESTABLISH INTERVALS ACCORDING TO PLANT REQUIREMENTS.
a- Stem packing or seal leakage. In case of leakage from stem seal or packing proceed first to inject
sealant through the sealant nipple where provided (see 8.4.1 below). If it does not stop the leak the
stem gland seal must be replaced.
b- Body-adaptor leakage. If leakage from body and adaptor join occurs, it is necessary to replace the
body gasket.
c- Seat leakage. In case of leakage from seat rings it is possible to inject special silicon grease into
emergency seal injection nipples (see 8.4.1 below). Be sure that the grease pump employed for this
intervention is able to give a pressure higher than the pipeline pressure.
8.4.1 Emergency Sealant Injection Procedure
A sealant is a heavy grease-like substance used to stop small leakages through sealing surfaces. A
slightly damaged or scratched sealing surface can still close if some sealant is injected. Sealant injection
is intended for temporary emergency situations, where a major valve overhaul to replace the seats is not
possible.
Sealant is injected through the grease fittings (25) located in the valve body, near the seat area. Grease
fittings are not fitted on all valves as some clients prefer not to have them to prevent the possibility of
applying grease unnecessarily which can then attract debris and damage the seat. In smaller size valves
there is only a body sealant injection. In this case the valves must be full open during injection, more
grease is required as the valve cavity must first fill, then stroke the valve in order to wipe the grease
onto the seats. Then repeat the procedure. For normal lubrication see 8.2.
Sealant injection is a temporary measure, remove the valve at first opportunity and
repair. Greasing the seats can then attract more debris onto the seats so only grease
in an emergency, unless flushing with light grease as shown in Section 2.4.
In most cases, sealant injection in the upstream seat will be enough to stop a small leakage. However, it
would probably be necessary to inject sealant each time the valve is operated to keep leakage under
control. If standard grease does not work there are many PTFE composite greases with advanced sealing
capabilities available.
The procedure for injection of sealant in the seats is as follows:
1. Before injection of sealant, ensure that the ball stops are not out of alignment. A small misalignment of
2 or 3 degrees may open the bore hole to the line pressure, causing continuous leakage.
2. Use an appropriate high pressure sealant-injection pump, capable of overcoming the pipe pressure and
the high pressure build-up caused by the sealant itself, during it’s injection in the sealant passages.
3. Confirm that the ball is in the closed position (unless, as is sometimes the case with valves 80 NB (3”)
and under, the valve has a single sealant nipple only on body cavity, then it must be in full open
Australian Pipeline Valve - Installation, Operation and Maintenance Manual
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SIDE ENTRY 3P TRUNNION BALL VALVES API6D STANDARD - BVF100 SERIES
