Actuator Mounting - Fisher 655 Instruction Manual

in the pipeline ahead of the regulator or relief valve to
protect it while in service. And a conventional three-
valve bypass (see figure 3) should be placed around
the regulator or relief valve to permit continuous op-
eration when it is being installed or repaired.

Actuator Mounting

The actuator may be installed either above or below
the pipeline. If the regulator or relief valve is to be
used for steam service, the valve should be installed
with the actuator positioned below the pipeline, and
the control line should be sloped down toward the dia-
phragm casing. This is to ensure that any forming con-
densate will maintain a water seal to protect the dia-
phragm.
The following procedure describes how to mount the
actuator on either a push-down-to-close or a push-
down-to-open valve so that the actuator stem and
valve stem thread engagement will allow full travel and
proper shutoff. Refer to figure 4 for actuator mounting
components. Key numbers refer to figure 5 unless
otherwise stated.
1. Turn the adjusting screw (key 10) into the yoke
(key 7) to force the diaphragm (key 2) and diaphragm
plate (key 4) against the upper diaphragm casing (key
1).
2. Perform the following steps as appropriate for ei-
ther push-down-to-close or push-down-to-open valve
action.
CAUTION
In the following procedures, do not ro-
tate the valve plug while it is seated
since this may cause damage to the
seating surfaces and thereby allow ex-
cessive leakage. Also, during travel ad-
justment, use tools carefully to avoid
damaging the valve plug stem. A dam-
aged stem could cut the packing and
allow leakage.
For Push-Down-To-Close Valves:
a. Place the actuator part way over the valve stem.
Then, place the yoke locknut over the valve stem,
and slide the travel indicator disk (key 11, if used)
on top of the hex nuts (key 12).
b. Set the actuator onto the valve body. The length
of the valve stem will prevent the actuator yoke
(key 7) from sitting on the bonnet properly. Mea-
sure the distance from the bottom of the actuator
Type 655 and 655R
yoke to the mating shoulder on bonnet, and then
add the valve plug travel to this measurement.
c. Raise the actuator so the valve plug can be
lifted off the seat ring.
Either turn the actuator, or tighten the
hex nuts together, and use a wrench on
the hex nuts to turn the valve plug and
stem assembly.
Thread the valve stem into the actuator stem the dis-
tance measured in the previous step.
d. Lower the actuator onto the valve body bonnet,
and tighten the yoke locknut.
e. Connect the pressure control lines as described
in the Loading Connection portion of this section.
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 actua-
tor 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 indi-
cator 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 4).
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 dis-
tance measured in the previous step. Tighten the
hex nuts (key 12) together, and use a wrench to
turn the valve plug and stem assembly.
Note
3