What is the formula to estimate the duration of flow from cylinder pressure, tank factor, and liter flow?

• A. Psi x tank factor / liter flow
• B. Tank factor / (Psi x liter flow)
• C. Psi x liter flow / tank factor
• D. Psi + tank factor + liter flow

Answer: (A)

Estimating how long a cylinder will last hinges on turning the current pressure into a total gas volume and then dividing by how fast you’re using it. The tank factor is the constant that converts cylinder pressure (in psi) into the total liters of gas available. Multiply the pressure by this tank factor to get the total liters, then divide by the liter-per-minute flow to get the duration in minutes. In formula form: duration = (pressure in psi × tank factor) ÷ (liters per minute). This matches the idea of first counting all the gas on hand and then pacing its use. Using any other arrangement—such as dividing by a product, multiplying in a way that mixes units incorrectly, or adding the terms—would not yield a valid time estimate. For example, with 1800 psi, a tank factor of 0.28 L/psi, and a flow of 6 L/min, you get (1800 × 0.28) ÷ 6 ≈ 14 minutes.