A butterfly valve may have jerky operation for the following reasons:
The actuator/shaft adaptor is misaligned
Remove the actuator mounting and realign.
The packing is too tight
Loosen the packing torque until it is only hand tight. Tighten to
the required level and then cycle the valve. Re-tighten, if required.
CAUTION: Always follow safety instructions when operating on valve.
If the valve has a pneumatic actuator, the air supply may be inadequate.
Increase the air supply pressure to standard operating level.
