Pipeline Flow Rate Calculator

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Pipeline Flow Rate Calculator

Calculate volumetric flow based on pipe diameter and fluid velocity.

Enter the internal diameter (ID)
Average speed of the liquid
Please enter valid positive numbers for both fields.
Calculation Results
Flow Rate (GPM – US Gallons/Min):
Flow Rate (CFS – Cubic Feet/Sec):
Flow Rate (LPM – Liters/Min):
Flow Rate (m³/h – Cubic Meters/Hour):
Cross-Sectional Area (sq. ft):
function calculatePipelineFlow() { // Get DOM elements var diameterInput = document.getElementById("pipe_diameter"); var velocityInput = document.getElementById("fluid_velocity"); var errorMsg = document.getElementById("calc_error"); var resultsDiv = document.getElementById("calc_results"); // Get values var diameterInches = parseFloat(diameterInput.value); var velocityFtSec = parseFloat(velocityInput.value); // Validation if (isNaN(diameterInches) || isNaN(velocityFtSec) || diameterInches <= 0 || velocityFtSec * 60 for Liters/Min var flowLPM = flowCFS * 28.3168 * 60; // 1 CFS = 101.941 m3/h var flowM3H = flowCFS * 101.941; // Display Results document.getElementById("res_gpm").innerText = flowGPM.toFixed(2) + " GPM"; document.getElementById("res_cfs").innerText = flowCFS.toFixed(4) + " ft³/s"; document.getElementById("res_lpm").innerText = flowLPM.toFixed(2) + " L/min"; document.getElementById("res_m3h").innerText = flowM3H.toFixed(2) + " m³/h"; document.getElementById("res_area").innerText = areaSqFt.toFixed(4) + " ft²"; resultsDiv.style.display = "block"; }

How to Calculate Pipeline Flow Rate

Understanding the volumetric flow rate of a liquid through a pipeline is a fundamental requirement in fluid mechanics, civil engineering, and process plant design. Whether you are sizing a water pump, designing an irrigation system, or monitoring an industrial chemical process, knowing the relationship between pipe size, velocity, and flow rate is essential.

This calculator determines the Volumetric Flow Rate (Q), which is the volume of fluid which passes per unit time.

The Flow Rate Formula

The calculation is based on the fundamental continuity equation for incompressible fluids:

Q = A × v

Where:

  • Q = Volumetric Flow Rate (e.g., cubic feet per second or GPM)
  • A = Cross-sectional Area of the pipe
  • v = Average Velocity of the fluid

Calculation Steps

To perform this calculation manually, follow these steps:

  1. Convert Diameter to Radius: If you have the Inner Diameter (ID) in inches, divide by 2 to get the radius, then divide by 12 to convert inches to feet (since velocity is usually in ft/sec).
  2. Calculate Area: Use the formula A = π × r².
  3. Multiply by Velocity: Multiply the Area (sq. ft) by the Velocity (ft/sec) to get the Flow Rate in Cubic Feet per Second (CFS).
  4. Convert Units: Multiply CFS by 448.831 to convert to US Gallons Per Minute (GPM).

Example Calculation

Imagine you have a 4-inch schedule 40 pipe (approximate ID of 4.026 inches, simplified to 4.0 for this example) with water flowing at a velocity of 5 ft/sec.

  • Diameter: 4 inches = 0.333 feet.
  • Radius: 0.1667 feet.
  • Area: π × (0.1667)² ≈ 0.0873 sq. ft.
  • Flow Rate (CFS): 0.0873 sq. ft × 5 ft/s = 0.4365 cfs.
  • Flow Rate (GPM): 0.4365 × 448.831 ≈ 196 GPM.

Typical Velocity Ranges

When designing piping systems, maintaining appropriate fluid velocity is crucial to prevent erosion (if too fast) or sediment buildup (if too slow).

  • Water Mains: 2 to 5 ft/sec
  • Industrial Suction Lines: 2 to 4 ft/sec
  • Industrial Discharge Lines: 4 to 9 ft/sec
  • Slurry/Solids: Higher velocities required to keep solids suspended.

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