Problem:

The operation of Shutdown valve at KVK GCS SDV101 is completely stuck up and was given for service to CE Valves.

And the operation of SDV102 (after service of actuator assembly at site) was observed to be opening in two or three strokes and not smooth.

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Update:

Last week the shut down valve (SDV101) was received after service from CE valves and checked.

After service the valve could be operated manually with handwheel. (was bit tight)

With actuator the 90 degree opening and closing rotation was observed to be occuring in two or three strokes in a slow motion with pauses in between.

Please advice.

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Operation: 

Shutdown valve has a Gear box mounted, a pneumatic cylinder and two spring assemblies at the ends.

Two ports are available in the cylinder body for charging/discharging of pneumatic supply to the cylinder.

One port is connected to center (between discs) of cylinder and another to the both ends (rear to the discs) of the cylinder.

For opening of valve air is charged between two discs mounted to the central shaft which is moving outward and air is discharged from rear end of the discs. 

For closing of valve air is charged to rear of the disc and air charged between the disc is discharged.

This charging and discharging is done via 5 port solenoid valve assembly.

Note: Pics of Shutdown valve actuator is uploaded to media gallery.