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When using Fisher valve positioners and control valves, we may encounter various issues, such as unstable force in the positioner signal regulator, unstable force in the pneumatic valve actuator regulator, or the absence of a pneumatic valve in the positioner. The editor will introduce these situations below. Unstable pressure of the signal regulator for the control valve in Fisher valve positioners is usually caused by an inappropriate time constant in the control system; we can then reset this time constant to a suitable value. Unstable operation of control valves with valve positioners is usually caused by leaks in the output pipeline ； The actuator is too small ； The nozzle baffles of the amplifier are not parallel; the baffles do not cover the nozzle ； The ball valve of the amplifier becomes poorly sealed due to dirt and wear, and output oscillations occur when the amount of pneumatic energy required to operate the valve increases significantly ； The reasons for the high frictional resistance during the movement of the valve stem, as well as the obstruction at the contact points, can all be addressed one by one. Reason for the valve positioner having a signal but not moving: The actuator spring has rusted due to long-term disuse ； The valve core is stuck to the valve seat ； The valve stem is broken or bent ； Valve core detachment ； If there are carbon deposits or dirt on the valve seat, or if the valve core is frozen, we can determine the cause of the lack of operation based on these factors. Above, we have introduced the various situations and reasons we may encounter when using Fisher valve positioners. When using it, everyone can decide based on the actual situation. If you have different opinions, you can contact us.