What happens when the valve core becomes disconnected from the valve stem?
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What will happen to a pneumatic control valve that is in operation if the valve spool becomes disconnected from the valve stem?
1 is a sudden change in the parameter being regulated; 2 is a situation where the control valve fails to perform its control function – the valve stem moves, but the flow rate through the control valve remains unchanged, and the flow meter shows no variation.
It depends on the position of the valve spool when this fault occurs in the control valve, as well as on whether the control valve operates in an open or closed mode.
The main issue is that your control valve is unable to operate autonomously; it deviates from the set control point and cannot be controlled. So go to the site and check it in conjunction with the valve
A control signal is provided, but the result remains unchanged; the flow rate does not change.
This depends on the process conditions: The key is to determine whether the valve is normally open or normally closed; if it is of the normally closed type, there is basically no impact. If it is of the normally open type, then a control signal is sent, with no change in the parameters of the process medium. I went to the site and saw that the valve stem was moving, but the parameters of the medium did not change. Treatment – it’s only possible to replace it with a new one, or to disassemble it, re-weld it, and reinstall it.
The control valve does not function as a controller; the valve stem moves, but the valve core does not move, and the flow rate through the control valve remains unchanged.
1. Sudden change in the parameter being adjusted； 2. The control valve fails to function, and the pneumatic valve stem remains stationary at a certain extreme position.
Observed in the control room: When the control parameters are changed, the corresponding controlled parameters show almost no change at all； Observed on-site: The actuator operated normally, while the valve spool hardly moved.