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Steam Pipe Sizing Calculator

Work out steam pipe sizing instantly with clear inputs, formula shown and shareable results.

About Steam Pipe Sizing Calculator

Steam mains are sized on velocity. Mass flow is converted to volume using the specific volume of saturated steam, approximated here as 446 divided by absolute pressure, then divided by the design velocity to get the bore. Saturated steam distribution normally runs 4,000 to 6,000 fpm; wet steam must be kept slower to avoid erosion.

Formulas

Volumetric flow

ft³/min = lb/h x specific volume / 60, specific volume ≈ 446 / absolute psia

Bore

Area = flow / velocity; diameter in = sqrt(4 x area / pi) x 12

Worked example

With the default values below, Steam Pipe Sizing Calculator returns Pipe bore required of 1.41. Change any input above and every figure here is recalculated in your browser.

Inputs used

Steam flowminimum 1 lb/h
1,000 lb/h
Steam pressureminimum 0 psig
100 psig
Design steam velocityminimum 500 fpm
6,000 fpm

Results

Pipe bore required
1.41 in
Steam specific volume
3.888 ft³/lb
Volumetric flow
64.8 ft³/min
Cross-sectional area
1.555 in²

Step by step

  1. 1Values used
  2. 2Volumetric flow
  3. 3Bore
  4. 4Pipe bore required= 1.41 in
  5. 5Steam specific volume= 3.888 ft³/lb
  6. 6Volumetric flow= 64.8 ft³/min
  7. 7Cross-sectional area= 1.555 in²

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Preliminary estimate only. Confirm against steam tables and the applicable pressure piping code before fabrication.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Confirm against steam tables and the applicable pressure piping code before fabrication.

Frequently Asked Questions

How is the Steam Pipe Sizing figure worked out?

ft³/min = lb/h x specific volume / 60, specific volume ≈ 446 / absolute psia. Steam mains are sized on velocity.

Why does higher pressure mean smaller pipe?

Specific volume falls roughly in inverse proportion to absolute pressure, so the same mass of steam occupies far less space and needs less bore at high pressure.

What values do I need to enter?

This calculator takes 3 inputs: Steam flow, Steam pressure, Design steam velocity. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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Steam Pipe Sizing Calculator – Calculate Pipe bore required