Pressure to leave in the tank to prevent contamination.
Please enter valid positive numbers for all fields.
Available Gas Volume
0 Liters
Time Remaining (Minutes)
0 min
Time Remaining (Formatted)
0 hr 0 min
function calculateDuration() {
// Get Input Elements
var volInput = document.getElementById("cylWaterVolume");
var pressInput = document.getElementById("currentPressure");
var residInput = document.getElementById("safetyMargin");
var flowInput = document.getElementById("flowRate");
var errorDisplay = document.getElementById("errorDisplay");
var resultsDiv = document.getElementById("resultsSection");
// Get Values
var waterVolume = parseFloat(volInput.value);
var currentPressure = parseFloat(pressInput.value);
var residualPressure = parseFloat(residInput.value);
var flowRate = parseFloat(flowInput.value);
// Validation
if (isNaN(waterVolume) || isNaN(currentPressure) || isNaN(residualPressure) || isNaN(flowRate) ||
waterVolume <= 0 || flowRate <= 0) {
errorDisplay.style.display = "block";
resultsDiv.style.display = "none";
return;
}
// Logic check: if current pressure is less than residual, time is 0
if (currentPressure 0) {
formattedTime += hours + " hr ";
}
formattedTime += remainingMins + " min";
document.getElementById("resFormatted").innerHTML = formattedTime;
}
Understanding Gas Cylinder Flow Rates
Calculating how long a gas cylinder will last is a critical task in medical settings (oxygen therapy), welding, scuba diving, and industrial applications. Knowing the remaining time ensures that operations can be completed safely without running out of essential gas supplies.
The Formula for Cylinder Duration
The calculation of cylinder duration is based on the relationship between the cylinder's internal volume (water capacity), the pressure of the compressed gas, and the rate at which the gas is being consumed. The standard formula used in this calculator is:
Cylinder Water Capacity: This is the actual physical volume of the metal cylinder if it were filled with water. This is distinct from the amount of compressed gas it holds.
Current Pressure: The pressure reading from your regulator gauge, measured in Bar. (Note: 1 Bar ≈ 14.5 PSI).
Residual Pressure: It is standard safety practice never to drain a cylinder completely. Leaving 20-50 Bar ensures that moisture and contaminants do not enter the cylinder.
Flow Rate: The rate at which gas is being released, measured in Liters Per Minute (LPM).
Common Cylinder Sizes and Capacities
While cylinder naming conventions vary by region (e.g., US vs. EU standards), knowing the water capacity allows for universal calculation. Below are common medical oxygen cylinder sizes:
Cylinder Type
Water Capacity (Liters)
Approx. Gas at 137 Bar
D Size
~2.9 L
~400 Liters
E Size
~4.7 L
~640 Liters
F Size
~9.4 L
~1,288 Liters
M / G Size
~23.0 L
~3,150 Liters
Example Calculation
Let's say you have an E-size cylinder (4.7 Liters water capacity) showing a pressure of 100 Bar on the gauge. You are administering oxygen at a flow rate of 4 Liters per minute, and you want to leave a safety margin of 20 Bar.
Determine Usable Pressure: 100 Bar – 20 Bar = 80 Bar.
Calculate Available Gas: 4.7 Liters × 80 Bar = 376 Liters of Oxygen.
In this scenario, you have approximately 1 hour and 34 minutes of gas remaining before you reach your safety limit.
Why Use a Safety Margin?
The "Safe Residual Pressure" input in our calculator is crucial. If a cylinder is completely emptied (0 Bar), the internal environment matches the external atmospheric pressure. This allows air, moisture, and dust to enter the cylinder, which can cause internal corrosion or potential hazards during refilling. Always plan to change cylinders before they hit zero.