# Determining How Long My Gas Cylinder Will Last

1. Mar 21, 2016

### cosmarchy

I'm not sure whether this is the correct place to post but here goes

I'm trying to determine how long my argon gas cylinder will last when I am using it for tig welding.

The cylinder is supplied with 1.32m³ (1320L) of Argon at 137 bar (13.7 MPa).

If I set my regulator pressure to 0.5 bar (0.050 MPa) and re-arrange Boyles Law P1V1=P2V2 so that V2=V1/(P2/P1) I will get a volume of 361,680L.
With a flowrate of 4cfh (113.28L/h) I would expect 361,680L / 113.28L/h to last approx 3192hrs.

Does this sound right - seems ludicrously high to me? Was it the correct way or is there a better / more accurate way, I should have done this?

Thanks

2. Mar 21, 2016

### Kevin McHugh

The answer is in your question. You have 1320 L of gas. Your flow rate is 113 L/hr. You have just over ten hours of gas flow rate.

3. Mar 21, 2016

### Staff: Mentor

In other words: 1.32 m3 is not the cylinder volume (it would be enormously huge), but the decompressed gas volume.