8 replies to this topic

[jprocess]

Dear All:
Line Break Valves are widely used between offshore gas gathering networks and reception facilities, near the shore to isolate the sealine from the reception facilities at the onset of a rupture.
Now what should be failure position of LBV?
There are two options:
1. FC: Based on the function of LBV, it should have a closed position as fail safe position. But suppose that during pigging operation the valve goes in FC position! This may cause some difficulties in pigging operation and shut down of downstream units!
2. FO: Will cause loss of inventory at the onset of rupture but will not have the above mentioned problems of FC state!
Your valuable comments are appreciated.

[JoeWong]

Dear All:
Line Break Valves are widely used between offshore gas gathering networks and reception facilities, near the shore to isolate the sealine from the reception facilities at the onset of a rupture.
Now what should be failure position of LBV?
There are two options:
1. FC: Based on the function of LBV, it should have a closed position as fail safe position. But suppose that during pigging operation the valve goes in FC position! This may cause some difficulties in pigging operation and shut down of downstream units!
2. FO: Will cause loss of inventory at the onset of rupture but will not have the above mentioned problems of FC state!
Your valuable comments are appreciated.

Put safety as priority. I consider FC.

[rxnarang]

Fail Close. Protect the onshore facility.

Pigging problems MAY not cause a hazard.

Rajiv

[jprocess]

Dear Rajiv and JoeWong,
Thanks a lot for your valuable comments.

Pigging problems MAY not cause a hazard.

I agree that FC should be the fail safe position but if pig traps behind of Fail Closed LBV the feed stream to downstream units will be lost and may cause shut down of downstream units.

[JoeWong]

Dear Rajiv and JoeWong,
Thanks a lot for your valuable comments.

Pigging problems MAY not cause a hazard.

I agree that FC should be the fail safe position but if pig traps behind of Fail Closed LBV the feed stream to downstream units will be lost and may cause shut down of downstream units.

Lost in the pipeline ? It will stay in the pipeline. It won't lost. Check with some operator if the pig is recoverable...tell us here.

I have not seen FO First Valve On (FVO, same as you LVB) and last valve off (LVO).

Again, safety first.

[jprocess]

Lost in the pipeline ? It will stay in the pipeline. It won't lost.

I mean downstream units will no longer have any feed stream!

[djack77494]

Fail closed is the only configuration I have seen for similar valves, and I totally support that viewpoint. In the event of a significant disruption as you are describing, the downstream facilities would be affected in any case. But the main point is that you MUST bring your system to a safe condition. There are any number of scenarios where a fail open valve would not achieve that; there are far fewer where a fail closed valve would not achieve that. The downstream units should be designed so that they also remain safe in the event of a supply disruption.
Doug

[JoeWong]

Lost in the pipeline ? It will stay in the pipeline. It won't lost.

I mean downstream units will no longer have any feed stream!

The downstream system will have low pressure control and protection system (if design is good)... I don't worry about the downstream system...

Read Doug's response. He explanation is much better...

[jprocess]

Dear Doug:

There are any number of scenarios where a fail open valve would not achieve that; there are far fewer where a fail closed valve would not achieve that.

Why did you use "any number of scenarios" for FO while use "far fewer" for FC?