Heavy HC from breathing valve during pipeline pigging
Heavy HC from breathing valve during pipeline pigging
(OP)
Dear all,
There is a pig receiver at a natural gas plant. Condensate from a pipeline is taken to the vessel through the condesate line with PRV installed. The flashing condensate will get into the vessel causing some HC getting out of the vessel through the breathing valve to the atmosphere. The breathing valve releases the vapour directly to the atmosphere but to the safe localization. There is no flare at the plant only a cold vent stack at remote location.
The guys from the plant claims that it is not possible to vent the vapours directly to the atmosphere because heavy HC released during the pigging may accumulate and cause the explosive atmosphere around the vessel. In my opinion it is pointless to have few hundreds of pipe to hook it up to the vent. Is there any example in the literature that my solution (breathing valve directly to the atmosphere) is acceptable. Are there are any calculations that can be done to prove that it is safe?
Or maybe guys from the plant are right and my solution is not acceptable at all.
Thanks for any comments.
Rob
There is a pig receiver at a natural gas plant. Condensate from a pipeline is taken to the vessel through the condesate line with PRV installed. The flashing condensate will get into the vessel causing some HC getting out of the vessel through the breathing valve to the atmosphere. The breathing valve releases the vapour directly to the atmosphere but to the safe localization. There is no flare at the plant only a cold vent stack at remote location.
The guys from the plant claims that it is not possible to vent the vapours directly to the atmosphere because heavy HC released during the pigging may accumulate and cause the explosive atmosphere around the vessel. In my opinion it is pointless to have few hundreds of pipe to hook it up to the vent. Is there any example in the literature that my solution (breathing valve directly to the atmosphere) is acceptable. Are there are any calculations that can be done to prove that it is safe?
Or maybe guys from the plant are right and my solution is not acceptable at all.
Thanks for any comments.
Rob





RE: Heavy HC from breathing valve during pipeline pigging
- Material balance for the escapes at the vent.
- Check the explosive safe and trigger limits for this HC over a known volume around the vessel- (depending on worst conditions of no winds- there will be an accumulation, i.e non-steady state flow) which could trigger an explosion (read on explosive dusts, causes, protections and preventions- flares are usually a cheap prevention).
- Compare your findings and always assume worst case scenario in design. (in my opinion- I wouldn't sweat the extra piping to avert the vent fumes away from the vessel). Let me know your findings- good luck.
RE: Heavy HC from breathing valve during pipeline pigging
Best regards
Morten
RE: Heavy HC from breathing valve during pipeline pigging
The other approach may be to install a flare stack with some assist gas like fuel gas to be burned during pigging operations. Most of the sweet ones I've worked on have only had short vent pipes similar to yours.
RE: Heavy HC from breathing valve during pipeline pigging
I will say this, though...
If the "guys from the plant" are uncomfortable about something, pay very, very close attention to it.
If it looks like a duck, walks like a duck, smells like a duck, quacks like a duck...
Regards,
SNORGY.
RE: Heavy HC from breathing valve during pipeline pigging
RE: Heavy HC from breathing valve during pipeline pigging
It seems like there is no other option than hook it up to vent stack. I hope they will accept this...
The stack is 10m high.
cheers
RE: Heavy HC from breathing valve during pipeline pigging
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: Heavy HC from breathing valve during pipeline pigging