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Hi Muhammad,
1. Mechanical constraints like actuator packing that are dirty. If the valve has a special mechanical linkage, maybe that it's not lubricated.
2. The gain of the valve it's set to low.
3. Pneumatic converter/positioner assembly it's out of calibration, you need to take that out and get it to a calibration shop.
4. Air header pressure low. Check the valve air supply and see at that point of tapping that isolation valve of the supply it's of and the isolation valve ot the entire tapping multipoint it's ok.
Good luck!
1.Should check its calibration span according to4...20 mA
2.Air Pressure
3.Mechanical valve alignment and its intenal seat.
POSITIONER SIGNAL DELAY DUE TO AGEING.
Each solenoid is rated for flow in liters per minute or by a flow coefficient (Cv) or flow factor (Kv). The rated airflow of the solenoid valve must meet the bulk handling valve manufacturer’s requirements of air demand to the air cylinder. If purchasing solenoids locally, make sure the air flow and other ratings are a perfect match to the solenoid specified by the valve manufacturer. Using a lower flow solenoid valve will cause performance problems such as chattering and slow actuation of the blade.
Your air supply on your control valve is not sufficient or means pressure is less
The pneumatic control valve slow response is caused by :
1- Low air pressure input ... you have to check the air regulator setting
2-Mechanical valve is bad or just too slow in moving due to a stuck
