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You all speak about the Purity of He , the Mil specs ,bla bla.. Is not the Gas purity im worried about is the cylinder im breathing from im worried. Have you ever been in a steel welding and construction yard ? Have you seen what those tanks are going through ? Left abandoned next to all kind of dangerous materials and contaminates ( fuel , Paint , chemicals .. you just name it ) I saw many of them lying next to industrial drills with the valve full open waiting to be pick up from the gas supplier. I saw man welding next to the open valves for days. You now why ? Because they know for sure that nobody will use them for anything else than welding. Have a look at the exterior condition i bed my #$%$ that they are the same rusty condition in the inside. Do you know what is the rule for welding tanks in the gas supply company ? Use it as long as it doesn't leak. I made a special negotiation with my gas supplier to private me 99.995 in clean inspected tanks used for high purity He. If i was ever thinking of using welding grade i will have bought my on tanks and send them over and over for refilling. ( i dont have a clue if this is feasible in the US ) Cytech Dv. Manos Manoli Limassol - Cyprus Gilldiver@ao*.co* wrote: > Just to settle this once and for all, I did some searching on my work data > base for the MIL and commercial specs for welding and breathing helium. Here > are the results: > > There are 3 Mil-spec and one industry specs that come up: > > MIL-PRF-27407B Performance Specification Propellant Pressurizing Agent, > Helium (Last rev date 8/25/97) > > BB-H-1168 Helium Technical > > MSFC-SPEC-364C Helium (Last rev date 8/15/69) > > Compressed Gas Association Specification CGA G-9.1 Helium > > I could not get a copy of G-9.1 so I will stay with the Mil-Specs. > > MSFC-SPEC-364C lists the same requirements as BB-H-1168, and BB-H-1168 > refers to MIL-PRF-27407B. So lets stick with MIL-PRF-27407B. > > Section 6.1 Intended Use: This section states that: > > Type I Grade A helium is for "pressurization of rocket propellant systems, > space vehicles and associated ground support equipment, welding and other > shielding gas operations. > > Type I Grade B helium is for "intended for use as a respirable breathing gas > for divers during deep excursions into the oceans." > > Type II is Liquid Helium. > > So we are concerned with the difference between Type I Grade A and Type I > Grade B. > > Here are the differences from Table I. > > Grade A Grade B > Purity 99.995 99.997 > Impurities (ppm by vol, max) 50 ppm max - > Water 9 9 > Hydrocarbons 5 1 > Oxygen 3 3 > Nitrogen + argon 14 5 > Neon 23 23 > Hydrogen 1 1 > Carbon dioxide 1 - > Carbon monoxide 1 - > > I then called my two compresses gas suppliers who will cert to MIL-PRF-27407B > and asked for the difference between Grade A and B. The reply was "We test > every cylinder of Grade B and only every lot of Grade A." I then asked how > easily they meet the requirements of this spec and the reply was "We almost > never even see the listed contaminates and when we do they are only just > detectable." > > I then stated to them "So the only difference between Grade A and B is how > you handle the bottles, testing of every bottle, and the cert?" The reply was > Yes, and about a 300% markup for the paperwork. > > So, there is no difference in the purity or quality you get between welding > (Grade A) and breathing (Grade B) helium. > > There, now can we talk about something else? > > Peter Johnson > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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