compressor api 14c 1

[142846]

Hello. I have question about use of bdv for compressors based on API 14c. API rp 14c 2017 says "A blowdown valve should be located on the compressor unit final discharge line(s) for compressors greater than 1000 hp." what is the concept of application of this bdv? Is this sentence applicable for reciprocating compressors that there is not surge for this type of compressors.Normally and usually Applicable of BDV returns to fire and gas but I think concerns of this sentence of api 14c is about compressor protection not event of fire and gas? thanks a lot.

 

[1503-44]

My linked version is the one that is legally current in the USA. Newer editions of 14 series have not yet been adopted into the CFRs. It may take years and years to do so, if ever. The current CFRs still only require the use of 2003 edition of ASME B31.8

We can freely access the codes and standards that are referenced in the CFRs at so many websites on the internet, because any such editions must be made available to all US citizens at no additional charge. I think quite a lot of the standard writing organizations issued new editions after that law was enacted only so they can tell us that we are using an old edition, knowing full well that we would believe we must immediately buy the latest edition from them, many (all) of which are very expensive for interested individuals that do not actually need to use the latest editions in their daily activities.

It would help if you could post the text of only the paragraphs in 14C that mention the blowdown of separators. Thanks. I would like to try to understand this requirement, as apparently it is a new line of reasoning.

Depending on the type of scrubber/separator, it might be better to blow it down through the inlet side to avoid damaging the internals.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[142846]

ax1e
please attached find about compressor blowdown based on api 14c 2001 (19 years ago).

 

[1503-44]

That does not necessarily mean a direct blowdown of the suction scrubber through a blowdown valve located on the scrubber or located directly on suction piping. Blowdown of suction scrubbers, separators and all suction piping, as well as compressor and its discharge piping an occur through the blowdown valve located on the station discharge line. And yes if course that has been one of the requirements in addition to SDVs at compressor station inlet and outlets since the first edition of 14C.

AX1E-THANKS A LOT
BASED ON ATTACHED FILE BLOWDOWN HAS BEEN OPENED EVEN FOR SCRUBBER HIGH LEVEL AND ANY OTHER PROCESS CONDITIONS NOT FIRE AND GAS. IN YOUR OPINION WHY API 14C INSIST AND PERSISTENCE TO OPEN BDV EVEN IN HIGH LEVEL SCRUBBER? BECAUSE I AM AGREE WITH YOU AND I THINK THERE IS NO NECESSARY TO OPEN BDV IN THESE CONDITIONS.

Correct. I do not see any requirement to directly blow down the suction scrubber, nor do I see any requirement or need to trigger a blowdown event of any kind if suction scrubber or seperator levels goes high. I would trigger a compressor shut down if suction scrubber or separator levels reached HiHi, but I would not trigger a blow down event. You have not shown me anything from 2017 edition that would lead me to believe differently.

Do you have any more questions?



“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[142846]

ax1e,
1. you are right about the revision of api 14c.
2. from my first contribution my question was about blowdown valve that installed on the compressor unit final discharge line(s) and blowdown on the suction scrubber has not my concern.
3. Based on attached above my contribution (extracted from API 14c 7th edition that is similar to 8th edition),obviously observed that process abnormal conditions ON SCRUBBER causes opening the BDV located at final DISCHARGE lines. MY QUESTION IS WHY (BASED ON WHICH PHILOSOPHY OR CONCEPT) BDV SHALL BE OPENED AFTER PROCESS ABNORMAL CONDITIONS ON SCRUBBER?

 

[1503-44]

Blowdown of ALL gas in the station is what is required by CFRs and B31.8 API cannot ignore the legal requirements and separators can contain a large volume of it.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[142846]

ax1e
Without considering any API or CFR Or ... and only based on your technical experience, are you agree to opening BDV (final section) after pressure or level high or low on scrubber to discharge ALL gas. What about the partially discharge?

 

[1503-44]

In a genuine emergecy situation with an active ESD, I certainly would shut in the station and blow down all piping, separator included. Minding the time to blowdown, I might place a blowdown directly on upstream suction/separator piping in addition to discharge piping.

I can't really think of any purely process-based reason to blow down a separator on compressor suction. I think it might be a good idea to have it at low pressure and low liquid level when starting up a compressor station so that potential inlet pressure swings associated with liquid surges might be more easily controlled. Maybe somebody else can think of one.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[georgeverghese]

The only reason I can see for blowdown of the compression train for such non LOC events is when the any of the suction stages of the train is not capable of withstanding the worst case shutdown settleout pressure relevant to that compression stage. But this is an awkward way of dealing with this design deficiency, and transient overpressure of the weaker components may still occur during this shutdown - blowdown event. All components should, by design, be capable of handling the worst case settleout pressure.

 

[MortenA]

Could not see if this ha been mentioned - but for centrifugal compressors its recommendable to blow down the casing volume in order to protects the mechanical seals. Normally there would be a timer to prevent short stops to cause a BD. I dont know about the 1000 HP requirement.