Welding HE - Good ?

October 2000, Peter Johnson - Gilldiver@aol.com

Just to settle this once and for all, I did some searching on my work database 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
• 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.

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.