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3.
Guided trim: coat the guide portion of the stem with
MOLYKOTE G-Rapid Spray lubricant or an equivalent
light lubricant suitable for your service. Assemble plug
to stem.
4.
Insert the stem into the bonnet. Set the gasket around
the boss on the bonnet. Carefully assemble the bonnet
to the body and allow the plug to center into the seat.
Push down on the stem to be sure that the plug has
fully engaged the seat. Hand-tighten the body bolts.
* for ¼” Motor valves, use ½” torque values
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∗
for ¼” motor valves with Grafoil gasket, use quantity
of 2.
5.
Install the packing as described in “Packing
Replacement”.
6.
While holding the plug firmly in position in the bottom
seat, secure the body to the bonnet with the bolts.
Torque bolts evenly to the values shown.
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7.
Reassemble the two stem nuts and indicator all the
way onto the stem threads. Lock to the actuator.
8.
If the actuator is reverse acting (ATO), apply
approximately 6 psig air pressure to the actuator.
8a. If MOTOR VALVE, position the bottom seat to full open
9.
Insert support legs into the bonnet flange and thread
the stem into the actuator stem. Hold the actuator stem
with a wrench to prevent it from turning. When the stems
are engaged enough to bring the support legs into full
contact with the bonnet flange, install the nuts onto
support legs and tighten.
(You can press down on the actuator to compress the
springs and bring the legs into contact with the bonnet
flange.) The actuator spring preload must be adjusted;
refer to “Actuator Spring Preload Adjustment”. For Motor
Valve see “Motor Valve Seat Spring Pre-Load”.
∗
Standard Bolting
Actuator Spring Preload Adjustment
1.
The two stem nuts should be loosened and threaded
down on the stem and then locked together.
2.
A regulated air supply must be provided to the actuator.
Connect the air to the lower case for reverse acting or
to the upper case for direct action actuators.
3.
Standard actuators have ranges of either 3-15 psig or
6-30 psig. The range is stamped on the valve nameplate.
These instructions will assume that the range is 3-15. If
yours differs, substitute the appropriate pressure where
these instructions refer to 3 psig.
4a. Direct Acting Actuator (ATC): Slowly increase the air
pressure up to 3 psig while observing the stem for
movement. If there is movement at less than 3 psig:
thread the valve stem into the actuator stem, wrenching
on locked stem nuts and keeping the actuator stem
from turning to increase the spring preload. If there is
no movement at 3 psig: thread the valve stem out of
the actuator stem to decrease the spring load.
4b. Reverse Acting Actuator (ATO): The bottom seat is
closed against upward fluid thrust by actuator spring
force. Total compression placed on the actuator spring
must be sufficient to provide preload plug force required
to close the valve. If preload adjustment is made with
no pressure in valve body, then, when the control valve
is placed in operation, additional compression must be
placed on the spring to provide valve closure force.
With proper adjustment, valve will close tightly and will
not begin to open until the preload pressure is exceeded.
Slowly increase the air pressure up to 3 psig while
observing the stem for movement. Adjust spring preload
until valve just starts to open when 3 psig air pressure
is supplied to the actuator diaphragm. If there is valve
movement at less than 3 psig: thread the valve stem
out of the actuator stem, wrenching on the locked stem
nuts and keeping the actuator stem from turning to
increase spring preload. If there is no valve movement
at 3 psig: thread the valve stem into the actuator stem,
wrenching on the locked stem nuts and holding on to
the actuator stem to keep it from moving, to decrease
spring preload.
Actuator Maintenance
Disassembly and Inspection of Actuator
Note: The actuator stem has two retaining rings. The purpose
of these rings is to maintain compression on the springs (to
keep them in place) should the actuator be removed from
the valve bonnet. The upper ring functions with reverse
action and the lower ring functions with direct acting
actuators.
1.
Follow instructions under Maintenance section to
remove valve from line.
2.
Remove the actuator as described in “ Removing Valve
Actuator”.
3.
Direct Acting Actuator (ATC): separate the cases by
removing the bolts. Use a wrench on the flats of the
actuator stem to prevent it from turning and remove
the bolt and lockwasher. Lift off the diaphragm washer,
diaphragm, diaphragm plate, and ThredSeal. Remove
the springs.
If the actuator stem is to be removed, remove one
retaining ring and push the actuator stem out. Remove
and discard the o-ring and two backup rings.
4.
Reverse Acting Actuator (ATO): separate the cases
by removing the bolts. Remove the springs. Use a
wrench on the flats of the actuator stem to prevent it
from turning and remove the bolt and lockwasher. Lift
off the diaphragm plate, diaphragm, diaphragm washer,
and,ThredSeal.
If the actuator stem is to be removed, remove one
retaining ring and push the actuator stem out. Remove
