Welding Tips and Tricks

Hi Everyone,

I went from a S size bottle (150 cf) to a T size bottle (337 cf).

When I first connected the T size the gauge pressure to the regulator was 2,650 psi. I believe the highest I ever saw an S cylinder was 2,100.

This may be kind of a stupid question; but, what is the comparison between 850 psi on the T versus 850 psi on the S in terms of usable volume. Would it be 337/150 more volume for the T, or isn't there a reliable way to compare the gauge reading to the volume for different size cylinders?

I'm trying to get a handle on this so I can schedule to have a bottle delivered at about the time I run out.

I Googled this; but, I didn't really come up with anything that looked like it made sense.

Thanks,

Jeff

I could be wrong but in pretty sure the PSI is not directly correlated to volume.

My brain says 337 cubic feet is 337 cubic feet regardless of pressure it's sitting at.

Cause on my cylinders of argon I've seen anywhere from 1900-2400PSI. They all seem to last around the same amount of time but I don't pay too close of attention since I have a spare bottle to swap to and then get a refill at my leisure.


Anybody feel free to correct me if I'm wrong as I'd love to know the right answer for this.

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Hi Toggatug,

Thanks for the information.

I don't understand whether or not there is any kind of linear relations ship between the pressure in the tank and the available volume.

I am used to working with CO2. Because CO2 is a compressed liquid, the pressure is constant until all the liquid has vaporized in the tank. Then the pressure drops rapidly as gas is released. I know that Argon is a compressed gas, so the CO2 scenario wouldn't apply.

I was just trying to ballpark when I should exchange tanks. The T size is too big for me to hoss around. Delivery is reasonable, so it's a great deal. I do have an 80 cf for backup. I just don't want to tap into it unless I get in a jam.

Thanks,

Jeff

Jeff2016 wrote: ↑Wed Jan 05, 2022 1:49 pm Would it be 337/150 more volume for the T, or isn't there a reliable way to compare the gauge reading to the volume for different size cylinders?

From what I can tell/know, that estimate (the 337/150 factor) slightly over-shoots the volume comparison because the T cylinder has a higher required fill pressure to contain the ~330 ft³ of gas, where as the S cylinder is filled to a lower pressure (typically) closer to 2000psi

Some charts show S tanks (150 ft³) rated to 2015psi, but it may be over-filled by 10% if the rating calls for it and if the vendor chooses to do so.









Assuming your T cylinder is rated at 2400psi, and your S was 2015psi which they should be,

The T cylinder contains 12.5 ft³ per 100psi of tank pressure. So 850psi would equate to roughly 106 ft³ of Argon.
The S cylinder contains 7.44 ft³ per 100psi of tank pressure. So 850psi would equate to roughly 63 ft³ of Argon.

337/150 ≈ 2.25, where as 12.5/7.44 ≈ 1.7, so as you can see the factor of 337/150 over-shoots the estimate by approx 17-20%. (not all 300 tanks are overfilled 10% to get to 330 ft³ so that's where another slight discrepancy lies)

If the initial pressures were higher than what the cylinder is rated for due to the allowable 10% over-fill, that's great because you essentially got a small bit of free Argon, but doesn't change the fact that the required fill pressures are 2015 and 2400 psi for S- and T-sizes, respectfully.

Hi Oscar,

That's great information! Thank you.

It all makes great sense. Easier to estimate now, for sure.

Take Care,

Jeff

Thanks Oscar, I learned something new now too!

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