MKS HPS LPV1-25-AC Series, Operation And Maintenance Manual

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the limit switch assembly as described in section 7.4.2, make electrical
connections as discussed in section 6.2, and adjust the switches as detailed
in section 7.4.4
7.4.4 Limit Switch Adjustment
An ohmmeter and pneumatic supply are required for limit switch
adjustment. Connect the ohmmeter to the NC (normally closed) and C
(common) terminals of the closed position limit switch. With the valve in its
closed position, open circuit resistance should be indicated. Cycle the valve
to its open position. Closed circuit resistance should be indicated (less than
0.5 ohm). Run the valve through several cycles to be sure that the switch is
actuating properly and sufficiently near full closure.
If the switch does not actuate, actuates too early, or is always actuated, the
switch needs adjustment. Loosen the lower 2-56 screw holding the switch
just enough to allow movement of the switch about the upper 2-56 screw.
Move the switch to correct the problem and tighten the lower 2-56 screw.
Test the operation of the switch through several cycles to ensure proper
function. Repeat these steps until it functions properly.
Connect the ohmmeter to the NC and C terminals of the open position limit
switch. With the valve in its closed position, closed circuit resistance should
be indicated. Cycle the valve to its open position. Open circuit resistance
should be indicated. Run the valve through several cycles to be sure that
the switch is actuating properly and when the valve is fully opened.
If the switch does not actuate, actuates too early, or is always actuated, the
switch needs adjustment. Loosen the upper 2-56 screw holding the switch
just enough to allow movement of the switch about the lower 2-56 screw.
Move the switch to correct the problem and tighten the upper 2-56 screw.
Test the operation of the switch through several cycles to ensure proper
function. Repeat these steps until it functions properly.
7.5 Solenoid Pilot Valve Service –
Pneumatic Actuation Only
In normal use, solenoid pilot valves should last millions of cycles, although
this number is reduced by about a factor of ten when a dry pneumatic
supply is used.
The solenoid valve is connected to the actuator cylinder by a 1/8" NPT
nipple and the threads are sealed with a jointing compound or Teflon
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tape.
If Teflon tape is used, excess tape overlapping the end of the nipple in the
assembly can be sheared off, resulting in blockage of pneumatic flow and
possible valve failure.