Control Valve Positioning

<...determine and check what is actually wrong here?...>

The check of what is wrong has been done, otherwise there would be no need for the original post.

It is a simple matter to change the action of a valve actuator, and it can be done usually without removing the valve body from the pipeline subject to the actuator model. Arrange for an instrument technician to attend and do it, and in the meantime change the controller setting to the opposite action for the time that the technician takes to arrive and complete the task so that the plant can keep running. Clearly, the controller action needs to be changed back again on completion of the task.

To prevent recurrence, check that the valve servicing task sheets have the required valve action option stated, and that there is a check-box to signal that the technician has checked the required action on the bench before returning the valve for reinstallation.

The is valve normally closed(NC), air to open?

Is it a simple matter of incorrectly hooking up your air lines?

Unless the spring was put on the wrong side of the actuator, were the actuator now becomes normally open (NO).

If this is the case, that is a bad thing, usually. You want the actuator to be (NC) in case there is a system failure, you want the unit to shut down.

Correct the actuator.

Hi - There is no mention of the "Make" and Model of the valve. If the valve has been overhauled it could be reversed, sound like a Fisher "A" series body. - obviously unqualified personnel are repairing the valve - The instrument guy is also suspect as his knowledge of valve repairs is poor - a instrument mechanic should be able to repair the complete valve.

I hope nobody will come with this sort of questiones concerning a nuclear plant

If before the valve was air to open and now its air to close, then someone reversed the actuator or positioner settings.

Have a qualified person check the valve.

Hello Fadzril

You have given limited information here.

What type of valve is this? i mean globe/plug/angle etc.

When you mean Overhauled the valve did you mean overhaul the actuator or the valve.

if its the actuator and its a double acting actuator since this is pnuematic could be possible that while connecting the air the people have connected the wrong tappings to the actuator . It is difficult to imagine the mechanical team changed the actuation of the valve in the valve, Kindly cross check whether its the actuator or the valve. its also possible that some enthusiastic engineer just changed the controls indication in the DCS you might want to cross check that as well.