Continuous Purge Gas Requirement in Flare, and Vent System on Platform
Continuous Purge Gas Requirement in Flare, and Vent System on Platform
(OP)
Hi friends,
I received the new P&IDs for the new wellhead platform and found that there is no continuous purge gas for flare, and vent facilities. Normally,flaring, and venting on wellhead platform are occasionally occured. However, as I understand purge gas on flare, and vent system has to be provided to protect the system from air ingress which can lead to underiably internal combustion inside the system.
Could you please tell me if the purge gas can be possibly not to be continuously performed in the flare and vent system ?
If the continuous gas purging may not be required, which cases of flare and vent systems that may not require this continuous gas purging ?
If the continuous gas purging is always required, what is the reason that it is required ?
Thank you very much, (^_^)
Worachai
I received the new P&IDs for the new wellhead platform and found that there is no continuous purge gas for flare, and vent facilities. Normally,flaring, and venting on wellhead platform are occasionally occured. However, as I understand purge gas on flare, and vent system has to be provided to protect the system from air ingress which can lead to underiably internal combustion inside the system.
Could you please tell me if the purge gas can be possibly not to be continuously performed in the flare and vent system ?
If the continuous gas purging may not be required, which cases of flare and vent systems that may not require this continuous gas purging ?
If the continuous gas purging is always required, what is the reason that it is required ?
Thank you very much, (^_^)
Worachai





RE: Continuous Purge Gas Requirement in Flare, and Vent System on Platform
If this is a cold vent system (basically a vent just to the atmosphere with no pilots), then I've seen these without purges. The logic is that a major release will simply push the air out of the vent header given the gas velocities. Talk to the contractor and find out the design basis for the flare and how it is intended to be used. They you'll need to decide if you agree with that logic. If your company's specs don't help you, review with what you typically do on other platforms and whether you need to match that.
RE: Continuous Purge Gas Requirement in Flare, and Vent System on Platform
Usually there will be an open drain for maintenance and this will usually have a vent. The vent is not purged but could be purged if required.
Best Regards
Morten
RE: Continuous Purge Gas Requirement in Flare, and Vent System on Platform
Thank you very much for your answer. It is very helpful for me. (^_^)
Best Regards,
Worachai
RE: Continuous Purge Gas Requirement in Flare, and Vent System on Platform
Found excellent article on HIPPS (high integrity pressure protection systems) at:
http://www.clarkson.edu/~wilcox/Design/hipps.pdf
I guess it is allowed by ASME as of 1996 or so, so is relatively new... where HIPPS substitutes for need of pressure relief valves and flare system?...
If worachai, or anyone else, uses HIPPS, is it common to also have flare stack as backup? ... where it would be purged with inert gas prior to lighting??
Cheers//
RE: Continuous Purge Gas Requirement in Flare, and Vent System on Platform
I think the stack is purged using N2 and that the flare drum doubles as closed drain with a spill over valve and a special quick acting emergency valve with a bursting disc as a back up.
The flare drum "float" on the compressor inlet fressure under normal operation (constant back pressure on your PSV's).
In denmark its mostly in connection with unmanned installtions (platforms). If you dont have shut-in design pressure on your piping/pipeline then HIPPS is required. Then you dont have a flare stack.
You could also read the NORSOk standards:
http://www.nts.no/norsok/p/p00104/p00104.htm
covers HIPPS as the Norwegians see it (and i belive they are the one that knows most about this subject).
Best Regards
Morten