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Shielding Gas Cylinder Duration Calculator

How long will a shielding gas cylinder last? Enter the cylinder's gas volume and your flow rate.

Cylinder & flow

Fields start empty. Enter your own values, or load the worked example to see how it works.

ft³

Gas volume at atmospheric pressure, from your supplier or cylinder label. Not pressure (PSI) and not water capacity.

CFH

Flowmeter reading. CFH = cubic feet per hour.

%
%
% of working time

Share of the working day the arc is on. Used only for the elapsed shop time estimate.

Enter your values (or load an example) to see results. Fix any highlighted inputs.

Continuous flow vs. estimated elapsed shop time

Continuous-flow duration is how long the gas lasts if it runs non-stop at your flow rate. It is the most reliable result. Estimated elapsed shop time is a rougher figure: it assumes gas flows mainly while the arc is on. If the arc is on 25% of the day, the cylinder would last about four times as many working hours. Pre-flow, post-flow, purging, leaks and other gas use are not included, so real shop time will be shorter.

Formula

Usable gas      = cylinder volume × remaining % × (1 − reserve %)
Continuous time = usable gas ÷ flow rate
                  (L/min × 60 = L/h)
Est. elapsed shop time = continuous time ÷ arc-on %

Flow (CFH or L/min) is volume per time. Cylinder pressure (PSI or bar) is not flow and can't be used here directly.

Worked examples

125 ft³ cylinder, full, 25 CFH
Continuous = 125 ÷ 25 = 5 h
With 25% arc-on: 5 ÷ 0.25 = 20 working hours

3,000 L cylinder, 50% left, 10% reserve, 12 L/min
Usable     = 3,000 × 0.5 × 0.9 = 1,350 L
Continuous = 1,350 ÷ (12 × 60) = 1.88 h (1 h 53 min)

FAQ

›My cylinder is sold as '125' — is that 125 ft³?
Often, but not always. Cylinder size names don't always equal the gas content, and actual fill varies. Use the gas volume your supplier states.
›How do I know what percent is left?
For compressed gases like argon mixes, gauge pressure falls roughly in proportion to content, so current pressure ÷ full pressure gives an approximation. For liquefied gases like CO₂, pressure stays nearly constant until almost empty, so weigh the cylinder instead.
›What flow rate should I use?
Use the flow rate from your WPS or equipment manufacturer. This calculator doesn't recommend one.

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