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W3671-3*/IL
Figure 3. Schematic of Design CAV4 Valve with
Cavitrol IV Trim
Maintenance
Valve parts are subject to normal wear and must be
inspected and replaced as necessary. Inspection and
maintenance frequency depends on the severity of
service conditions. This section includes instructions
for packing lubrication, packing replacement, trim re-
moval, trim replacement, and use of flushing trim.
Because of the care Fisher Controls takes in meeting
all manufacturing requirements (such as heat treating
and dimensional tolerances), use only replacement
parts manufactured or furnished by Fisher Controls.
Key numbers used in these procedures are shown in
figure 10, except where indicated.
VALVE PLUG
UPPER CAGE
SEATING SURFACES
FOUR STAGED
PRESSURE DROPS–
ALL SIGNIFICANT
THROTTLING AND
PRESSURE REDUCTIONS
OCCUR IN THESE ARES
Packing Lubrication
A lubricator or lubricator/isolating valve (figure 4) is
available for use with PTFE-composition packing or
other packings that require lubrication. If a lubricator or
lubricator/isolating valve is used, it will be installed in
place of the pipe plug (key 17) in the bonnet (key 12).
Use a good quality silicon-base lubricant. Packing
used in processes with temperatures over 260_C
(500_F) should not be lubricated. Be certain the lubri-
cant is compatible with the process liquid. The fre-
quency of lubrication depends upon the severity of the
service conditions.
To operate the lubricator, simply turn the cap screw
clockwise to force lubricant into the packing box. The
lubricator/isolating valve operates the same way ex-
Design CAV4
WARNING
Avoid personal injury and property dam-
age from sudden release of process
pressure or bursting of parts. Before
performing any maintenance operations:
D Always wear protective gloves,
clothing, and eyewear when performing
any maintenance operations to avoid
personal injury.
D Disconnect any operating lines pro-
viding air pressure, electric power, or a
control signal to the actuator. Be sure
the actuator cannot suddenly open or
close the valve.
D Use bypass valves or completely
shut off the process to isolate the valve
from process pressure. Relieve process
pressure on both sides of the valve.
Drain the process media from both sides
of the valve.
D Vent the power actuator loading
pressure, and relieve any actuator
spring precompression.
D Use lock-out procedures to be sure
that the above measures stay in effect
while you work on the equipment.
D The valve packing box may contain
process fluids that are pressurized, even
when the valve has been removed from
the pipeline. Process fluids may spray
out under pressure when removing the
packing hardware or packing rings, or
when loosening the packing box pipe
plug.
5
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