Fisher 9500 - Manual (Page 6)

9500 Valve
Instruction Manual
Form 2433
November 2007
6
leakage downstream (between the bushings and
disc hubs) may also indicate a need for hub seal
adjustment.
To adjust the hub seals:
1. Tighten both thrust-plate cap screws (key 10) 1/4
turn on one side (the side where shaft leakage is
occurring).
CAUTION
To avoid excessive side thrust on the
disc and possible liner damage,
tighten cap screws on both sides of
the valve alternately and in 1/4-turn
increments. Do not over-tighten by
continuous turning or by tightening
one side only. Over- tightening the cap
screws will cause the liner to fail.
2. Tighten both thrust-plate cap screws 1/4 turn on
the other side of the valve.
3. Repeat steps 1 and 2 until leakage stops.
Note
If this adjustment is being performed
to stop minor leakage past the disc,
check the leakage after turning the cap
screws enough to move the thrust
plates 0.8 mm (1/32 inch) closer to the
valve body. If leakage has not stopped
or diminished, the leakage is probably
due to incorrect linkage adjustment or
damaged valve parts. Refer to the
Linkage section to check linkage
adjustment; refer to the Maintenance
section to inspect and replace parts.
4. If leakage around the shaft cannot be stopped by
adjusting hub seals, refer to the
Maintenance section
to inspect and replace damaged parts.
Linkage
If the linkage between the power actuator and valve
is improperly adjusted, the actuator may reach the
end of travel before (or after) the disc reaches the
fully closed position. This could result in leakage
past the disc. The linkage adjustment is set at the
factory, and it should not be necessary to adjust
linkage unless the actuator and valve have been
separated and the adjustment altered.
To check the linkage adjustment on Fishtail discs,
the flat is on the same side of the shaft as the nose
or leading edge of the valve disc (as shown in
figure 2). When the valve disc is at the fully closed
position, the flat will be either top-dead-center or
bottom-dead-center in relation to the valve body.
The top-dead-center position is shown in figure 2. A
more accurate check of the fully closed disc position
is obtained by removing the valve from the pipeline.
WARNING
To avoid personal injury and damage
to the process system caused by the
sudden release of pressure, isolate the
control valve from all pressure and
relieve pressure from the valve body
before removing the valve from the
line. Be sure the disc is closed so that
it will not hit the mating flanges when
being removed from the line.
With the valve removed from the line, position the
actuator to the valve-closed end of the travel.
Measure the distance between the valve face and
the top and bottom edges of the disc as shown in
figure 2. The disc is at the fully closed position if the
two measurements are equal.
To adjust linkage, refer to the actuator instruction
manual.
Three-Way Valve Tandem Linkage
If the valve is used as part of a three-way valve
assembly, adjustment of the tandem linkage (see
figure 5) may be necessary to ensure proper rotation
of the slave valve disc.
If the adjustment is being performed with the
three-way valve assembly out of the line, temporarily
bolt the valve bodies to the tee to compress the liner
faces until there is metal-to-metal contact between
the valve bodies and the tee.
Check the rotation of the power valve disc per
instructions in the Linkage section. If necessary,
adjust the linkage between the actuator and the
power valve.
To check the fully closed position of the slave valve
disc, use the partial keyway on the slave valve shaft
or measure equal distances between the slave valve
face and the top and bottom of the slave valve disc
as described in the Linkage section. Tighten the