5-1
Chapter 5. Adjustment
As a general rule the diaphragm type control Valves require no adjustment. However, when
coupling an actuator to a valve body after removing the actuator for overhaul or other
purposes, adjustment of travel (stroke) is necessary. For this adjustment, refer to Figure 4-7,
Figure 5-1 and proceed as follows:
(1) Fix the actuator to the valve body by securely tightening the yoke clamping-nut (use a
chisel and a hammer).
(2) Connect an adjustable air pressure (with a pressure regulator) to the actuator - to the top
diaphragm case for the direct action type or to the bottom diaphragm case for the reverse
action type.
(3) Lower the valve seat and check that it is contacted with the valve seat.
For the Direct Action Type
(4) Apply to the actuator the maximum air pressure corresponding to the spring range
indicated on the nameplate.
(5) Increase the air pressure to the supply pressure and check that the actuator stem moves by
1 - 2 mm in response. (This movement represents the allowance of stroke.)
(6) Decrease the air pressure once. Then increase it again to the maximum value
corresponding to the spring range, in the increasing direction.
(7) In the above state, align the actuator stem and valve stem on a straight line, adjust so that
the thread of the stem connector mates with those of actuator stem and valve stem and
securely tighten the clamping-bolts of the stem connector. (See Figure 5-1.)
For the reverse action type
(4) Apply to the actuator the minimum air pressure corresponding to the spring range
indicated on the nameplate, and check that the actuator stem moves by 1-2mm
inresponse.
(5) Increase the air pressure once. Then decrease it again to the minimum value corre.
sponding to the spring range, in the decreasing direction.
(6) Perform a procedure identical with that of Item (7) of''For the Direct Action Type.'' (See
Figure 5-1.)
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