Opening of in-service Butterfly valve with broken locking pin

[franklin55]

We have a 24" Wafer type butterfly valve installed on the inlet cooling water line of one of the exchangers.A few days back the valve was closed for taking the exchanger out of service for maintenance purpose. After the maintenance we tried to take the exchange back into service by opening the valve, but it was found stuck (jammed). We tried to rotate the spindle by applying a large moment arm (putting a pipe wrench to it) but this resulted in the breaking of pin (used to fasten the spindle with the gate). Subsequently the spindle became free. Now the problem is that for replacing the valve we have to de-pressurize the main cooling water header which will result in the long duration plant outage (which we want to avoid). Can any body advice any solution to opening the gate without de-pressurizing the line?? A quick reply is requested.

 

[ash9144]

You could try increasing your CW header pressure. Sometimes the line pressure will force open the disk. The problem is even if it does do that you now have a loose disk which can basically open and close at will. So even if you get it open it could slam shut sometime in the future.

 

[DLite30]

By the way it sounds, I don't think you're going to have any luck with that valve.

You could install a 12" "hot tapped" bypass line around it with a new valve, and put the exchanger back in service with a reduced capacity.

Or you could install a stopple up stream of the valve, to isolate, remove and replace the valve.

 

[franklin55]

we have installed two bypass lines across this valve by ho tapping ( 10" and 12 "), but still the required flow is not passing through it. (Because the cross sectional area of 12" and 10" is less than the area of 24").