[ASME B31.3] CO2 (Carbon Dioxide) fluid service classification

[Yanuar88]

Dear All,

Apologies if this has been addressed before, but there are numerous Carbon Capture Projects established in many countries. My question is: Is CO2 classified as a Category D Fluid service according to ASME B31.3, particularly in terms of being 'non-toxic'?"

Thanks,
Yanuar

 

[LittleInch]

There is often a bit of a debate about this, but IMHO, CO2 should be regarded as toxic fluid as long term exposure to high levels of concentration, but not enough to cause death by asphyxiation, is recognised as being "toxic". It is though an asphyxiant, so if something like Nitrogen is not a Cat D fluid then neither should CO2.

In any event Cat D is limited to 10 bar / 150 psi, but in most usages a Cat D fluid is basically inert, so water, air, that sort of thing.

B31.3 does not provide a list or guidance on this issue and leaves it to the owner.

I think there is enough information out there to show that CO2 is or has the potential to be toxic that it should not be regarded as a Cat D fluid. IMHO.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[DekDee]

LI,
Dictionary description of toxic = poisonous
Dictionary description of poisonous = very harmful and able to cause illness or death.
Would a leak of nitrogen or CO2 cause illness or death ?
Obviously if you were in an enclosed room full of those gases - yes, you could have illness or death.
But, in an oil refinery with all piping open to atmosphere ?

 

[DekDee]

You are correct though - there is a lot of debate on this.
Especially in the relevant B31.3 sub-committees.

 

[LittleInch]

I always go back to Apollo 13 - if it wasn't toxic or dangerous, why did they bother?

Interesting thing here from NASA and also quoting NIOSH limits of exposure of 1% in air. Very achievable in a semi confined space, even in all that piping.
4% is quoted as "NIOSH: immediately dangerous to life..."

https://www.nasa.gov/wp-content/uploads/2023/12/ochmo-tb-004-carbon-dioxide.pdf

On a no wind cold day, there isn't much air movement.

"Would a leak of nitrogen or CO2 cause illness or death ?"
Answer YES.
You cannot legislate for where a gas goes once it escapes from your piping

So IMHO, CO2 is not a cat D fluid.
Cat D is intended to allow for lower levels of inspection and testing for basically non hazardous low pressure piping. I really don't think CO2 is one.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[DekDee]

LI,
Tend to agree with you on CO2 - all I could find is it is mildly toxic (under 5000 ppm it is deemed acceptable for working).
However, not sure on Nitrogen.
The refinery I am currently working on in Australia (which has very high safety standards) has Nitrogen as a Cat D.
I was mildly surprised to find it was in the same Line Class as Air / Water.
Without a definitive list of what is and isn't we can only speculate.

 

[LittleInch]

"Mildly toxic" = "a little bit dead"?

Nitrogen is s bit different I guess because we regularly breathe 80% without an issue. Whereas breathe 4% CO2 it is.

It's just when N2 gets to 90% that it becomes a problem, but isn't really toxic, just an. asphyxiant

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

We didn't worry about N2 or He, we figured that our enclosed space rules would offer protection.
However, Ar was a different story.
We did fill a basement of a building with AR once.
Didn't lose anyone but it was close.
Fortunately, the first person to go in was a trained diver and he recognized that there was a problem before it was too late.

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