[ani.kulkarni21]

The flow rate of Argon gas is measured in litres per minute (lpm), using a gauge which is attached at top of the cylinder. On this gauge, near the scale, two entities are written. "3.5 Bar" and "20°C". Does this mean that the gauge is calibrated for flow at 3.5 bar pressure and 20°C temperature only?? What is the standard used for this calibration??

[Mike]

21, welcome to the forum.

[clavius]

The flow rate of Argon gas is measured in litres per minute (lpm), using a gauge which is attached at top of the cylinder. On this gauge, near the scale, two entities are written. "3.5 Bar" and "20°C". Does this mean that the gauge is calibrated for flow at 3.5 bar pressure and 20°C temperature only?? What is the standard used for this calibration??

That is exactly what that means. Because any gas will expand and contract with both pressure and temperature, to accurately calibrate something like a flow meter you need to state the conditions under which it was calibrated. That means that at a different temperature (of the gas being measured) and operating pressure (a one liter container at 50 psi holds less gas than a one liter container at 100psi, etc), the calibration will be somewhat different. How much different is a function of the gas and the gauge you are using. In most cases for use on a welder, the difference is insignificant. If the flow rate were very critical one would need a different instrument to meter the gas flow or a flowmeter with a known correction chart so that you could make adjustments for temps and pressures outside of 20C and 3.5 Bar.

[ani.kulkarni21]

That's great. Thanks!!