Air Compressor Fill Time Calculator

Air Compressor Fill Time Calculator

An air compressor fill time calculator helps you estimate how long it will take for your air compressor to fill its tank from a starting pressure to a desired final pressure. This is crucial for planning tasks, understanding compressor efficiency, and ensuring your equipment meets your operational needs.

How It Works

The calculation is based on several key factors:

• Tank Volume: The size of your air tank (typically measured in gallons or liters). A larger tank requires more air to fill.
• Starting Pressure: The current pressure inside the tank before the compressor starts filling (measured in PSI – pounds per square inch).
• Desired Pressure: The target pressure you want to reach in the tank (measured in PSI).
• Compressor CFM: The compressor's Free Air Delivery (FAD) rate, measured in Cubic Feet per Minute (CFM). This indicates how much air the compressor can deliver at a given pressure. Higher CFM means faster filling.

The calculator determines the total volume of "free air" (air at atmospheric pressure) needed to increase the tank's pressure by the desired amount. This total volume is then divided by the compressor's CFM rating to give you the estimated fill time.

Formula Used

The core principle involves calculating the volume of air at atmospheric pressure required to achieve the pressure change within the tank. The simplified formula used is:

Fill Time (minutes) = [Tank Volume (gallons) * 0.133681 * (Desired Pressure - Starting Pressure)] / [Compressor CFM * Atmospheric Pressure (approx. 14.7 PSI)]

Where 0.133681 is the conversion factor from gallons to cubic feet.

Example Scenario

Imagine you have a 30-gallon air tank. It currently has 20 PSI of air, and you want to fill it to 120 PSI. Your air compressor has a Free Air Delivery (FAD) rating of 5 CFM at 90 PSI.

• Tank Volume: 30 gallons
• Starting Pressure: 20 PSI
• Desired Pressure: 120 PSI
• Compressor CFM: 5 CFM

Using the calculator below, you would input these values to get an estimated fill time. This helps you know if your compressor is adequate for your needs or if you need to wait a certain amount of time before starting a task.

Air Compressor Fill Time Calculator

function calculateFillTime() { var tankVolume = parseFloat(document.getElementById('tankVolume').value); var startPressure = parseFloat(document.getElementById('startPressure').value); var endPressure = parseFloat(document.getElementById('endPressure').value); var compressorCFM = parseFloat(document.getElementById('compressorCFM').value); var resultDiv = document.getElementById('fillTimeResult'); // Validate inputs if (isNaN(tankVolume) || tankVolume <= 0) { resultDiv.innerHTML = "Please enter a valid Air Tank Volume (must be a positive number)."; return; } if (isNaN(startPressure) || startPressure < 0) { resultDiv.innerHTML = "Please enter a valid Starting Pressure (cannot be negative)."; return; } if (isNaN(endPressure) || endPressure <= 0) { resultDiv.innerHTML = "Please enter a valid Desired Pressure (must be a positive number)."; return; } if (endPressure <= startPressure) { resultDiv.innerHTML = "Desired Pressure must be greater than Starting Pressure."; return; } if (isNaN(compressorCFM) || compressorCFM <= 0) { resultDiv.innerHTML = "Please enter a valid Compressor CFM (must be a positive number)."; return; } // Constants var GALLONS_TO_CUBIC_FEET = 0.133681; // 1 gallon = 0.133681 cubic feet var ATMOSPHERIC_PRESSURE_PSI = 14.7; // Standard atmospheric pressure at sea level // Calculate the volume of free air needed // V_free_air = Tank_Volume_cu_ft * (P_end_gauge – P_start_gauge) / P_atm var tankVolumeCuFt = tankVolume * GALLONS_TO_CUBIC_FEET; var pressureDifference = endPressure – startPressure; var volumeOfFreeAirNeeded = tankVolumeCuFt * (pressureDifference / ATMOSPHERIC_PRESSURE_PSI); // Calculate fill time in minutes var fillTimeMinutes = volumeOfFreeAirNeeded / compressorCFM; // Convert total minutes to minutes and seconds var minutes = Math.floor(fillTimeMinutes); var seconds = Math.round((fillTimeMinutes – minutes) * 60); // Handle rounding for seconds (e.g., 60 seconds becomes 1 minute) if (seconds === 60) { minutes++; seconds = 0; } resultDiv.innerHTML = "Estimated Fill Time: " + minutes + " minutes and " + seconds + " seconds."; }