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Oxygen Cylinder storage room exhaust

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BronYrAur

BronYrAur

Mechanical
Nov 2, 2005
799
I am confused by what I am reading in an NFPA white paper on med gas storage. See attached. The table on page 3 states that the volume of gas is needed in order to determine the ventilation requirements. In the table they show the cubic inch volume of the cylinders and the cubic feet volume of the gasses. So, this gas information must be shown as some pressurized condition, although it does not say what the pressure is.

Right under this table, it indicated on page 4 that the STP volume of the vessels is to be used to determine the required ventilation. So I am confused on whether to use the volume of the cylinders or the compressed volume of gas.

In my particular case, I have 20 type H cylinders of medical oxygen.

Anyone have experience with this?
 
 https://files.engineering.com/getfile.aspx?folder=874bc4bc-981e-4584-845f-ddf9838643ce&file=WhitePaperMedGasCylinderStorage.pdf
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BronYrAur:

If you look at the second FAQ on page 5 they state that 12-13 E size cylinders would be less than the 300cf threshold. From column six of the table: 13 E size cylinders x 23cf = 299cf. In your case, however, 20 H size cylinders x 244cf = 4,880cf > 3,000cf so ventilation plus all the architectural requirements would need to be met. At least that's my read on it.

Regards

DB
 
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The room will only be 10'x8'x8'. So if I am to use the compressed gas volume numbers, then I will be at the 500 cfm requirement. that's 47 air changes per hour. Seems crazy!
 
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NFPA document - Page 4 said:
VENTILATION
Ventilation is required for storage locations
containing greater than 3000 ft3 of gas. This can
be provided with natural or mechanical exhaust.
The volume of fluid to be used in determining
ventilation is the volume (at STP) of the largest
single vessel or the entire volume of connected
vessels on a common manifold, whichever is
greater
Click to expand...
 
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MintJulep

That was my initial thought but then the more I read it seemed like I was supposed to use the compressed volume. And in the FAQ, as DBronson says, they're talking about the compressed volume.

Looking at cylinder volume I only have about 31 cubic feet total. For my 20 cylinders. So I would only need 6 CFM? That sounds too extreme on the other end.

 
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No, any reference to STP means UNCOMPRESSED gas volume, so 244 cf per cylinder.

If they only cared about "compressed volume", they would only have needed the "Nominal Volume" column of the table. For the example FAQ, the E-cylinder was 23 cf of oxygen at STP; the volume of the cylinder is only 293 ci = 0.170 cf

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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But the 244 cf per cylinder is for a cylinder that has an internal volume of 2,660 cubic inches, or only about 1.5 cf.

 
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Look, when the tank ruptures, is it really going to be about the 1.5 cf volume?

Re-read the brochure that you posted. The FAQ in question asks about 12 E-cylinders for the 300 cf, which works out to 25 CF per cylinder, which is NOT 293 ci for the nominal volume, and the volume listed under the oxygen column is 23 cf.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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Okay I think maybe we are hung up on terminology here. So the 244 corresponds to some pressurised gas in the tank but it would be 244 cubic feet if it were all expanded to atmospheric pressure. I guess that's the problem I'm having because who's to say what pressure is in the tank other than some standardized pressures?

So bottom line, I'm back up to 500 CFM giving me 47 air changes per hour. Seems crazy.
 
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Yes agreed on your calc, but the paper says no more than 500 CFM. So hopefully we aren't supposed to read between the lines and back-calculate how much gas would be allowed. In other words, hopefully the 500 cfm is not a limit on the amount of gas that can be stored.

I get tired of the bureaucratic morons who write these codes. they always leave critical information subject to interpretation.
 
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BronYrAur,
If the cylinders are on a manifold, and the Manifold springs a leak. You are going to get the uncompressed volume of any cylinder on that bank that has the shut off valve open. are you ready for that?
B.E.

You are judged not by what you know, but by what you can do.
 
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Hence, why everyone seems to do this outside under a rain roof.

These tanks get delivered by truck-drivers outside. Not many places want these delivery guys hiking back and forth thru their facilities.

Keith Cress
kcress -
 
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This room will have access from the exterior only. So would you agree that I need 500 CFM exhaust in this little 10 by 8 by 8 room?
 
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I can't say on the 500CFM. It makes me wonder how any hospital can exist. If you have to handle the storage room seeing ALL the gas out of ALL the manifolded bottles then why wouldn't this case be the same for every hospital suite fed by that same manifold? Perhaps they're after a regulator and so not subject..

I would make the exterior wall ornamental or chainlink fencing, or some other 50% or less coverage converting the space to exterior some creative way.

Keith Cress
kcress -
 
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Anything fed by the manifold would be limited by the critical velocity through the piping, which is often pretty narrow; it's only at the manifold where you might get a massive release of the gas.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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