Medical Gas Installation N2 Purity

[DrRTU]

Installing medical O2 and Vacuum as per NFPA 99 2012 chapter 5. Can we use “industrial grade” N2 for inerting during braze or do we have to use “medical grade”? I believe both specs are listed as oil free.

 

[BigInch]

As I recall from by Big3 days, there was absolutely no difference between any industrial or medical "quality" gas we put in any bottle, other than the QA/QC testing itself and the marking on the bottle of course.

Learn from the mistakes of others. You don't have time to make them all yourself.

 

[DrRTU]

Biginch, Thank you. That is what I thought. My NFPA 99 has disappeared and I believe the wording is oil free. I know medical grade bottle gas is used with sterilized items. Medical grade has the certs with O2 content but industrial is the same percent. My certified fitters have 2 different opinions. I don't want to waste the more expensive gas or risk rejection of the piping.

 

[BigInch]

Oil free is more to do with how it is handled and stored rather than how it was made. Keep away from oil-filled pressure gauges, oiled fittings, bushings, oiled pipes and hoses. Compressed O2 + Oil, or oil + liquid O2 = explosion.

We never certified O2, N2 as sterile.
Probably the most important test you could do on O2 med, or breathing air would be for CO content.
We did smoke test for N2 purity against O2 content.
Dew points for all.
The biggest difference was that industrial O2 went into red bottles, med into green.

Learn from the mistakes of others. You don't have time to make them all yourself.

 

[Duwe6]

Especially if you get the "large, economy size" N2, from a liquid dewar. Gaseous [evaporated] N2 from cryo liquid is by definition 'oil free' as the oil, if any, lies solid at the bottom of the dewar jug. For the same reason, there is no moisture or CO2. They all stay frozen. Only CO will not, but there really is no 'mechanism' to get CO into a jug of liquid N2.

Same with liquid argon.

 

[BigInch]

The CO2 is extracted from the raw air before compression by first, if I remember correctly, bubbling the air through a solution of concentrated NaOH. If there was to be any making it past, it would quickly freeze, as would most things.

Learn from the mistakes of others. You don't have time to make them all yourself.

 

[Gator]

BigInch, I thought it was Main Air Compressor > Adsorbers/Reversing exchangers, with CO2 coming out via the latter.

Piping Design Central

 

[BigInch]

Not in that plant. Least I don't remember it that way. BTW it was 40 yrs ago.

Learn from the mistakes of others. You don't have time to make them all yourself.