Fisher 655 - Manual (Page 6)

655 and 655R Actuators
Instruction Manual
Form 1292
July 2007
6
f. Stroke the actuator, and measure the stem
movement to check travel. If the movement is
more than full travel, turn the valve stem out of
the actuator stem the amount of over-travel. If
movement is less than full travel, turn the valve
stem into the actuator stem the amount of
under-travel.
For Push-Down-To-Open Valves:
a. Place the actuator, yoke locknut, and travel
indicator disk (key 11, if used) over the valve
stem. Support the actuator above the valve body
so the actuator stem and valve stem do not
contact when the valve plug is seated.
b. Connect the pressure control lines as
described in the Loading Connection portion of
this section.
c. Move the valve plug, by hand, from the seated
to the open position, and make sure that valve
stem movement corresponds to the desired
travel.
d. Stroke the actuator until the diaphragm plate
(key 4) contacts the down travel stop (see
figure 3).
e. With the valve plug positioned as described in
step c above, lower the actuator until the actuator
stem contacts the valve stem, and measure the
distance from the bottom of the actuator yoke to
the mating shoulder on the bonnet.
f. Thread the valve stem into the actuator stem
until the thread engagement is equal to the
distance measured in the previous step. Tighten
the hex nuts (key 12) together, and use a wrench
to turn the valve plug and stem assembly.
g. Lower the actuator onto the valve body
bonnet, and tighten the yoke locknut.
h. Stroke the actuator, and measure the stem
movement to check travel. If the movement is
more than full travel, turn the valve stem into the
actuator stem the amount of over-travel. If the
movement is less than full travel, turn the valve
stem out of the actuator stem the amount of
under-travel.
3. After correct travel has been obtained, tighten the
hex nuts (key 12) against the actuator stem (key 8),
and tighten the yoke locknut with a hammer and
punch.
Note
Changing the spring adjustment will
not change the actuator pressure
range for that particular spring (see
table 2). Changing the spring
adjustment merely shifts the position
of the spring either up or down so that
valve travel can coincide with the
actuator pressure setting range.
4. While monitoring loading pressure with a
pressure gauge, stroke the actuator, and then turn
the adjusting screw until the valve begins to travel at
the desired pressure. Turn the adjusting screw out of
the yoke to decrease spring compression and thus
allow the valve to begin travel at a lower loading
pressure. Turn the adjusting screw into the yoke to
increase spring compression and thus allow the
valve to begin travel at a higher loading pressure.
Loading Connections
Install the control line following the steps listed
below. Typical installations are shown in figure 2.
1. Connect the control line into either the upstream
pipeline for pressure-relief service or into the
downstream pipeline for pressure-reducing service
as shown in figure 2. Make the pipeline tap at least
four to eight pipe diameters away from the regulator
or relief valve, or any elbow, swage, or nipple, to
avoid abnormal velocities or turbulence.
2. Connect the other end of the control line to the
1/2 NPT connection in the center of the upper
diaphragm casing (key 1) or to the connection in the
handwheel body (key 28, figures 5 and 6; key 142,
figure 7).
3. Fit the control line with a large-port needle valve.
Partially closing or throttling this valve will tend to
dampen any cycling or pulsating action of the
regulator. Never completely close the needle valve
while the regulator is in operation.
Startup
The procedures for placing into operation and
adjusting the equipment for both pressure-reducing
and pressure-relief applications are described below.
Typical installation schematics are shown in figure 2.
Startup For Pressure-Reducing Service
1. Open the needle valve in the control line.
2. Open the downstream shutoff valve.
3. Close the valve in the bypass line.