One of our customers called and informed that, he has one booster Air Compressor with two of Flowserve shear stream HP Valves with Actuators & Siemens Make Positioners. The problem, both the actuators overshoots the desired positions while opening, the operation is smooth while closing.
E.g. When we give a command of 25% open through the DCS the Actuators overshoots initially to 35-36% % then the Positioner (SIMENS SIPART PS2 6DR5010) tries to bring the Position down & the Actuators comes to 25%. Similarly, at 50% it shoots to 63-66% & comes back again, at 70% goes to up to 82-84% and on 80% through DCS it goes to 92-96% & comes back to desired position then. Such action is not visible while closing operation.
Following was done to test and identify the issue by customer:
We checked the Positioners by Removing the Valve assembly from the pipeline & Detaching the Valve from the Actuators, Checked Actuators by Connecting Instrument Air Connection & 4-20 mA through the Positioner, but nothing helped.
Siemens as well as the valve manufacturer was contacted and various tests carried out, various configuration changes tried and nothing seemed to help.
We observed that the behavior seems to be generating from the positioner and actuator part, valve seemed ok so, we decided to investigate it again, what we found was:
While selecting different components, the valve manufacturer selected a wrong solenoid model for this application, the solenoid was mounted directly on the valve and was restricting the vent port of the actuator, causing this problem.
Solution: Added a simple tubing between the actuator and the solenoid, thus removing the vent restriction and the machine was in perfect running condition again.