Troubleshooting - Actuated Ball Valve Is Slow To Close Or Open

Problem Solving
VALVE IS SLOW TO CLOSE OR OPEN
PNEUMATIC ACTUATED BALL VALVE

There can be various reasons why a pneumatic actuated valve is not operating properly after being fitted and although hard to accept it isn't usually the valve or actuator that is the problem if new, because before shipping the unit is operated and tested prior to despatch.

The new valve when fitted and operated should open and close smoothly and quickly. If it is not then: -

The first check would be to determine if the problem is either the air supply, valve or if it’s the actuator.

To check the actuator

Determine if it’s a single acting (has a spring for either closing or opening) or is it a double acting actuator (needs air to open and air to close).

Single acting usually has a S on the label after the type i.e. HP60S and double acting would have D (HP60D).

Air Supply

Check you have sufficient pilot air (we base our sizing on you operating the actuator, having a minimum of 5.5 bar).

If you have the right pressure, then continue the check

We now need to take the actuator off the valve to see if its functioning as it should.

Remove the four bolts from under the actuator and lift from the valve, paying attention to the position of the valve stem which may well have a bush fitted over it.

We will now test the actuator.

Place on a solid base and operate the actuator making sure it is secure.

If the actuator has a pilot valve fitted to it then the pilot solenoid usually has a manual override. If the actuator hasn’t got a local pilot, then it will have to be operated remotely.

Operate the manual override, If the actuator works as it should do then we will know it isn't this that’s the problem and we should
move onto the valve.

However, If the actuator isn't operating properly then we would check the pilot valve and tube i.e. check for no kinks in the tube and check the pilot valve is exhausting air correctly (sometimes the filter is blocked).

If the actuator still isn't working properly you should send it back to the supplier for testing.

If the actuator is working continue to check the valve

Check the Valve

Sometimes the valve when fitted could have been over torqued causing the end caps to compact the body seals, if compressed, it would make the valve difficult to open and close.

To determine if the valve is opening freely it needs to be operated manually in line, either with a wrench or handle.

If the valve is difficult to open you will need to inspect it more in depth and either remove it from the line, or slacken off the valve (if you feel it’s been over tightened) or if it is a three piece design then you could replace the seat in situ by releasing three of the four bolts (making sure the line is not live). This will allow the body of the valve to swing out and enable you to replace the seals.

This may well be the same symptoms if debris or a foreign body is lodged in the valve or have got behind the seats. This same procedure would need to be done.

Again, if nothing can be detected please return the full actuated unit to the supplier for inspection.