The preferred method of measuring shielding gas supply is:

The preferred method of measuring shielding gas supply is:

• A. Kilograms per square centimetre (pounds per square inch).
• B. Kilograms per minute (pounds per hour).
• C. Litres per minute (cubic feet per hour).
• D. Surface metres per minute (surface feet per hour).

Answer: (C)

Shielding gas protection depends on how much gas actually flows to the weld per unit time. Expressing this as a volumetric flow rate lets you specify how many litres pass a point each minute (or an equivalent in cubic feet per hour). This directly relates to how well the weld is shielded, regardless of the cylinder’s pressure or gas density. Measuring by mass flow (kg/min) can be misleading because changes in cylinder pressure or gas density don’t necessarily reflect how much gas reaches the weld area. Pressure alone doesn’t tell you the volume flowing through the nozzle, and a unit like surface metres per minute has no physical meaning for gas flow. So the standard method is volumetric flow rate—litres per minute (or CFH)—to ensure consistent shielding.

Shielding gas protection depends on how much gas actually flows to the weld per unit time. Expressing this as a volumetric flow rate lets you specify how many litres pass a point each minute (or an equivalent in cubic feet per hour). This directly relates to how well the weld is shielded, regardless of the cylinder’s pressure or gas density. Measuring by mass flow (kg/min) can be misleading because changes in cylinder pressure or gas density don’t necessarily reflect how much gas reaches the weld area. Pressure alone doesn’t tell you the volume flowing through the nozzle, and a unit like surface metres per minute has no physical meaning for gas flow. So the standard method is volumetric flow rate—litres per minute (or CFH)—to ensure consistent shielding.