Compressed Air Pipe Sizing Calculator

Inputs

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Compressed-air demand as free-air flow, such as Nl/min or SCFM/FAD.
SCFM
Gauge pressure at the start of the pipe run.
psi
Actual inside diameter, not nominal pipe size.
in
Straight pipe length or equivalent straight length of the run.
ft
Air temperature used for ideal-gas density and viscosity.
C
Equivalent internal roughness. Enter lower values for smooth plastic/copper and higher values for rough steel.
in
Sum of minor-loss K values for elbows, tees, valves, filters and quick-connects.
Screening velocity target used to back-solve pipe ID.
ft/s
Maximum pressure loss allowed over this pipe run.
psi

Results

Default result
Edit inputs
Pipe pressure drop(dp)
0.4802psi
Pass

Darcy-Weisbach at average absolute pressure 0.790 MPa.

Also computed

Pressure-drop utilization(dp / dp_allow)Pass9.459%

Below the entered pressure-drop allowance.

Estimated outlet pressure(P2)99.6psi

Line velocity(v)Pass14.29ft/s

At or below the entered velocity target.

Velocity utilization(v / v_target)54.46%

Required ID by velocity0.7256in

Minimum actual ID to meet the entered velocity target at inlet density.

Required ID by pressure drop0.6156in

Minimum actual ID to meet the entered pressure-drop allowance.

Compressed air pipe sizing previewCompressed-air distribution screenFree-air demand converted to line flow, then checked with Darcy-Weisbach.recommended actual ID18.4 mmpressure-drop limit9%velocity target54%
Method notes 3 notes
  • Free-air flow is converted to mass flow with the ideal gas law, then to actual line velocity at compressed-air density.
  • Pressure loss uses Darcy-Weisbach with Swamee-Jain turbulent friction and an entered sum-K fitting allowance. Density is iterated at the average line pressure.
  • This is a sizing screen only. Final compressed-air systems still need actual pipe schedule/material ID, compressor controls, dryers/filters, leak load, branch diversity, pressure regulators, manufacturer data, noise and plant safety review.

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