Line debris is increasing the required closing torque.
Flush or clean valve to remove the debris.
Actuator/shaft adaptor misaligned.
The actuator mounting must be realigned. This is done by loosening
the bolting and then repositioning the actuator on the mounting plate.
Packing is over-tightened.
Loosen packing bolts to hand tight and then reapply torque. Torque
values are found in the standard maintenance manuals which can be
downloaded from the Velan website.
For pneumatic actuator, air supply pressure is inadequate.
Verify either on the submitted drawings or with Velan what is the
required level of air pressure. If the supply pressure is low, make
sure that there are no leak paths in the air supply line.
The shaft key has sheared, disconnecting the stem from actuation.
To identify this problem, remove the actuator and inspect the drive
nut for signs of damage. This problem can usually be solved by installing
new components.
The actuator duty cycle was exceeded causing the actuator motor
to burn out.
Replace the actuator motor.
There is problem with the actuator other than those listed above.
At this point, the actuator should be inspected by an expert to
determine the cause of problem and the best possible solution.
