Helium and Oxygen Pricing

[teknitroxdiver]

So in spite of what I've read elsewhere about the gas being the same and coming from the same tanks, you are saying I need to buy the more expensive Medical O2 and UHP helium instead of the industrial grade? I'm not talking about balloon grade. I'm talking welding supply house stuff. Am I being stupid to consider this?

There's no reason to get medical O2 over ABO.

 

[Wookie]

There's no reason to get medical O2 over ABO.

I pay 12 for a 220 of medical and 50 for a 300 of ABO..... In Texas.

 

[teknitroxdiver]

I pay 12 for a 220 of medical and 50 for a 300 of ABO..... In Texas.

Really? Wow. There's your reason to get medical then!

 

[TrimixToo]

If you are going to breath it, it needs to be breathing grade. Even though it comes from the same filler. Helium 5.0 is the lowest grade I would consider at Trimix depths. ABO or Medical are the only grade I would consider, but you will learn all of that in your blender course and your AN/DP and Trimix course.

I'm with Frank on this. Among other things, 5.0 is the lowest grade from my local gas supplier with a certified THC level low enough for partial pressure blending.

Edit: Oh, and a T of 5.0 He was $225 today for me.

John

 

[RayfromTX]

I was quoted 95$ for 220 cuft of UHP and 22 for 210 of O2 welding.

 

[nadwidny]

I'm with Frank on this. Among other things, 5.0 is the lowest grade from my local gas supplier with a certified THC level low enough for partial pressure blending.

Edit: Oh, and a T of 5.0 He was $225 today for me.

So you want a real kicker? Your O2 probably has 10 or more times THC than your air.

 

[TrimixToo]

So you want a real kicker? Your O2 probably has 10 or more times THC than your air.

The specs for OCA and ABO are very close to the same (25 vs. 28 ppm THC), which I will admit I found surprising when I looked up the ABO standard this morning. I'd expected the ABO spec to be tighter, but in retrospect it makes sense that they would be close from transfilling safety standpoint. My compressor's last test showed <1 ppm THC, though, so ABO could easily have more than 28x that and still meet spec.

Locally, though, available He grades lower than 5.0 have no THC spec. If they published the analyses for the lower grades I'm sure I could save some money on He. That's probably why they don't do it.

John

 

[nadwidny]

The specs for OCA and ABO are very close to the same (25 vs. 28 ppm THC), which I will admit I found surprising when I looked up the ABO standard this morning. I'd expected the ABO spec to be tighter, but in retrospect it makes sense that they would be close from transfilling safety standpoint. My compressor's last test showed <1 ppm THC, though, so ABO could easily have more than 28x that and still meet spec.

Firstly we need to define THC. Up here in Canada methane would be included in that amount but in the US it seems to me that some labs do, some don't. If methane is included then it's impossible to get a THC value less than 1ppm since methane is present at around 2.0ppm in normal ambient air.So when a lab reports THC in an air sample as less than 1ppm, they are talking about what we would call VNMH (Volatile Non-Methane Hydrocarbons) which in Canada is reported as a separate analyte from methane and is normally less than 1ppm.

Because of the presence of methane in air, when it comes time to make breathing O2, getting rid of it is difficult, expensive and not necessary. That means that the methane spec for ABO (also medical, and welding) isn't lower than for air as the methane is concentrated as the nitrogen, etc is removed from the air. That's why in Canada the specs for methane in medical O2 range from 25 ppm to 100ppm, depending on the standard.

BTW the standard for methane in breathing air here is 10ppm maximum, so the 25ppm for OCA means that OCA isn't all that clean of a standard. To get 25 ppm methane in air there would have to be a natural gas leak nearby or sewer gas getting into the system.