Flowserve V-378 R1 Edward Equiwedge Gate Valve - Manual (Page 8)

8
Flow Control Division
Edward Valves
Service Problems
(cont.)
area of the gasket and body I.D. contact
may be caused by surface imperfections
in the body wall in the form of pin holes,
extended cracks, or indentations where
the metal has failed sometime after valve
installation and use. Such imperfections
may be surface indications deeper flaws
in the body casting which may cause a
by-pass around the pressure seal.
Gate and Seat Leakage
A leak existing at the seat and gate of a
properly closed valve might be indicated
by one of the following: a definite pressure
loss in the high pressure side of the valve;
continued flow through an inspection drain
on the low pressure side; or, in hot lines, a
downstream pipe that remains hot beyond
the usual length of time and conductivity
range. First, try opening the valve slightly
to flush any foreign material from the seat-
ing surfaces and then fully close the valve.
If this doesn’t stop the leakage, then one or
more of the following may be the cause:
1. Foreign material has been imbedded
into the seating surfaces preventing a
seal.
2. Foreign material has scratched or cut
the seating surface.
3. An obstruction such as a tool or other
foreign material has been lodged across
or between the seats and preventing the
gate from closing.
4. The valve seat has been steam or water
cut by not fully closing the valve during
a previous operation.
If the valve cannot be isolated and
repaired as soon as possible, schedule the
work to be done at the next outage.
Body or Bonnet Wall Leak
This is a leak through the pressure contain-
ing parts of the valve. A leak occurring
through the bonnet should be readily
detectable because of the lack of insula-
tion. On the body, because of the heavy
insulation, a small leak may go unnoticed
for a time on a hot line because the piping
evaporates the leakage.
Lubrication
In order to obtain long service life and
maximum reliability, valves require per-
iodic lubrication of the bearings and stem
threads the same as for any machinery
with rotating parts.
All handwheel actuated Equiwedge gate
valves are equipped with low friction bear-
ings, needle bearings in the smaller sizes
and tapered roller bearings in the larger
sizes. These valves have a lube fitting for
convenient relubrication. Both the stem
threads and the bearings can be relubed
through this fitting. In addition, it is advis-
able to clean the stem first while in the
open position and apply fresh grease to
the threads, then repeat while in the closed
position.
For valves that are operated infrequently,
relubrication at least once a year is recom-
mended. The recommended lubricant for
both bearings and stem threads is Rycon
EP 2, manufactured by the American Oil
Company. This is an extreme pressure,
temperature lubricant of high quality. Use
of other lubricants should be avoided.
For valves that are operated frequently, the
lubricant should be replenished at both the
bearings and stem threads every three
months or at shorter intervals depending
on the severity of the service.