PNEUMATIC ACTUATORS
ASSEMBLY & MAINTENANCE PROCEDURES
Ref. Doc. MMMACTREGDRE English Rev.2 – January 2012
21
18. FAULT FINDING
WARNING !!
Before disassembling the actuator, follow the instructions given below:
18.1 Actuator with solenoid valve
A If the actuator does not function check as follows:
1. The valve is free to rotate
2. The actuator is of the correct size
3. The correct voltage is supplied to the solenoid (the valve coil is tagged with the correct voltage
4. Sufficient compressed air is supplied to the solenoid valve
B If the proper voltage and air pressure have been verified and the valve is free to move proceed as
follows:
1. Apply the correct voltage to the solenoid valve. Check for a clicking sound.
2. If sound is not detected:
I) Carefully unscrew the solenoid and solenoid stem from the block.
II) Re-apply voltage and observe the solenoid plunger. If it does not retract replace
the solenoid valve.
3. If the solenoid functions, remove both the solenoid and the mounting block for testing.
Connect with a minimum 3 bar g air supply and correct voltage. Switch it on off and check the air
flow. Air should flow out of only one outlet port when the solenoid is energised.
C If the actuator functions but exhibits leak or power loss accompanied by leakage proceed as
follows:
1. Check the voltage. It must be within 10% of the specified voltage.
2. Check compressed air supply. Ensure that no intense pressure drops occur as the unit is
cycled. Loss of pressure can cause incomplete shifting of the spool valve in the block or at
one of the piston seals of the actuator. A leaking piston seal will usually leak on either cycle,
on spring return actuators, piston seal leakage will show at port B on the air manifold flange. A
leaking spool valve will require replacing. Leaking piston seals can be restored by replacing
the “O” rings with new ones.
a. Actuator without a solenoid valve.
For actuators without solenoid valve, (or those where the solenoid valve and mounting block are
working correctly), remove the actuator from the valve, disassemble and check the following:
1. Make sure all porting is clear of obstructions.
2. Make sure that the actuator is lubricated and that there is no solidified grease between the
pinion and piston racks. If solidified grease is present, clean, dry, regrease and reassemble.
3. Verify that the actuator pinion shaft and / or pistons are not seized. If seized, reassemble as
per instructions in section 8.
4. If the unit exhibits excessive backlash, check the teeth on the piston racks for wear.
5. With spring return actuators, check for misplaced or broken springs. If spring are broken
check the body for scoring.
6. If the actuator and valve are free reassemble the actuator and retest. If the unit still fails to
operate, contact ACTREG.
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