3 replies to this topic

[R NESAMANI]

Dear all,

I m working in Natural gas dispatch terminal.
We have 18'' ball valves. Trunnion mounted, 3 pc ball, 18'' 600# ball valve.
In upstream & D/S of flow meter. We wanted to remove the flow meter, so we vented the gas in flow meter.
But gas pr did not go below 5 kg/cm2. Also we opened the drain of the ball valve in D/s of the flow meter.
Gas is coming out from drain continuously. So its passing.
1) We did some tuning to position the valve in tight close. no use.
2) We pumped some cleaning fluid, then after 12 hrs , we pumped sealant. Still no use.

Tell me any idea to rectify this problem. Valve can't be removed from the stream. We can do online maint.

[TS1979]

It may not be the valve passing. It may be that the downstream of the ball valve was installed in wrong direction. For the ball valve, the flow directions for the U/S and D/S of the flow meter should be opposite. To isolate the flow meter, the high pressure face for the D/S isolation valve is the end which is further away from the flow meter instead of the end near the flowmeter. check the installation of the ball valves. If the two valve were installed with same flow direction, then the installation of the D/S valve is wrong. Please let us know what your finding is

[fallah]

TS1979,

As far as i know, the issue you did mention is mostly applicabe for floating ball valve which will provide better seal against differential pressure in flow direction when it is closed.

Fallah

[R NESAMANI]

Hi all, The details of the ball valve is

Size: 18’’ 600# ; Body: LF2 ; Stem: LF2/ENP ; Three piece, Trunnion mounted ball valve; Pipeline fluid : Natural gas;

On 11th & 12th June’12, we have done the maintenance of Ball valves at Dabhol terminal. We have used cleaning fluid then sealant injection. We adjusted the ball valve position also by moving the wheel. But the passing in ball valves still persists.
We vented the gas in the section up to 5 kg/cm2 & when we closed the 2'' vent line, within 40 sec pressure increased to 70 kg/cm2.
So i doubt that the problem is not passing, it is due to the valve position (not fully closed). so how to adjust the position of the valve.
These valves don’t have any isolation so only checking online (adjusting position) can be done.