Centrifugal Pump Operation - PLC Programming

[Selk]

I would like to ask, how the centrifugal pump operation is done through PLC in Auto - sequence mode in general.

Starting of Pump in Auto Sequence:

1) Whenever the pump has to be operated, the discharge valve needs to be in "shut" or "close" position.
2) After the Motor/pump has been started/accelerated to full speed, the discharge valve should start opening slowly to "open" position.
3) What happens if the discharge valve got struck in the middle position?
4) There is a timer which starts after the motor/pump has been given a start command. If the discharge valve got struck, the timer would get run out and stops the motor regardless of the discharge valve position.

Stopping of Pump in Auto Sequence:

1) First the discharge valve should be shut to give "Close" signal.
2) Again What happens if the discharge valve got struck in the middle position?
3) There is a timer which starts after the motor/pump has been given a stop command. If the discharge valve got struck, the timer would get run out and stops the motor regardless of discharge valve position.

I'm concerned because if the discharge valve got struck in the middle, the motor would be stopped/ started frequently which would affect the motor's life. Also how the discharge valve "Open torque switch" & "Close torque switch" be put into use in the ladder programming

Thank you for your insights!

 

[parky]

Not a good idea to start a centrifugal pump against a closed valve.
normally you open the valve, check it's open then start the pump, in reverse you would stop the pump, delay to allow pump to stop & then close the valve.
If the valve failed to open or it lost it's open limit then stop the pump.
If you are worried about starts per hour then put a delay timer on last stop so that it could not be started after x time.
If it is required that the valve be closed on start then I suggest start pump & open valve, start a timer if valve does not reach open position within x seconds stop pump etc. & hold on alarm.
Alarms should then only be reset by operator so that it would not hunt (cycle on/off).