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Plant Engineering Calculator

Updated Sep 18, 2026

Compressed Air Pipe Velocity Calculator — SCFM, Pressure & Bore

Convert free-air flow to approximate line-condition flow and velocity using absolute-pressure ratio, pipe inside diameter and temperature ratio.

Live calculationWorking shownPrivate in browser

Inputs

Results

Line flow 66.3 ACFM
Area 0.0218 ft²
Velocity 50.6 ft/s
Velocity 15.43 m/s
Velocity diagnostic: Above the 30 ft/s distribution screen used in DOE/ORNL compressed-air sizing guidance.
More actions

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Formula

Qline=Qfree×Patm/Pabs×Tline/Tstd; V=Qline/A.

Your calculation, step by step

These steps use the values currently entered above so the result can be checked independently.

  1. 1.Absolute line pressure = 100.000 + 14.696 = 114.6960 psia; temperature ratio = (30.00 + 273.15)/(20.00 + 273.15) = 1.03411.
  2. 2.Line-condition flow = 500.00 × 14.696/114.6960 × 1.03411 = 66.2504 ACFM.
  3. 3.Pipe ID = 2.0000 in ÷ 12 = 0.166667 ft; area = πD²/4 = 0.021817 ft².
  4. 4.Velocity = 66.2504 ft³/min ÷ 60 ÷ 0.021817 = 50.6116 ft/s = 15.4264 m/s.

How to use this calculator

  1. Enter measured or design values using the units shown beside each field.
  2. Review the live results and the substituted calculation steps before using the estimate.
  3. Check the assumptions below, then continue to a related calculator when the next engineering decision needs another model.

Worked example

500 SCFM at 100 psig occupies far less line volume than 500 actual CFM; pressure correction prevents a misleading velocity.

Assumptions and limits

  • Ideal-gas scaling is used for screening.
  • Pressure varies along a real line; use a pressure-drop model for final distribution sizing.
  • Use actual inside diameter and review velocity together with pressure drop; DOE/ORNL guidance uses low header velocities to limit distribution loss.

How to interpret the result

Treat the primary result as an engineering screening value, then use the secondary outputs to understand scale, energy or operating impact. Confirm site measurements, equipment limits and applicable standards before making a design or control change.

Questions engineers ask

Why is SCFM converted before pipe velocity is calculated?

SCFM is referenced to standard conditions, while velocity depends on actual line volume. The owner scales free-air flow by absolute pressure and absolute temperature before dividing by the pipe’s actual inside area.

Why must I enter inside diameter rather than nominal pipe size?

Velocity depends on flow area, and nominal size is not the same as actual bore. Schedule/material changes the inside diameter; use the real internal diameter from the pipe/tube specification.

What velocity should a compressed-air header target?

Project guidance varies, but DOE/ORNL compressed-air pipe-sizing material uses low design velocities to limit pressure drop and gives 20 ft/s as a typical header design target with 30 ft/s as an upper distribution screen. Final sizing should still be pressure-drop based.

Continue the calculation

Use the next calculator in the same engineering workflow instead of restarting from search.

compressed air pressure dropair compressor cfmcompressed air storage capacity
Methodology. MAXScanner shows the governing formula, entered values and calculation outputs so the estimate is auditable. The calculator is a screening aid; assumptions and equipment-specific limits remain part of the engineering review.