Energy
Steam Pressure Drop Calculator
Estimate steam-line pressure drop, outlet pressure, velocity and friction factor from flow rate, pressure, pipe diameter and length.
Calculation assumes dry saturated steam at the entered inlet pressure.
Optional additional equivalent length for valves, elbows and fittings.
0.045 mm is a common engineering estimate for commercial steel pipe.
Estimated Pressure Drop
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Preliminary Darcy–Weisbach pressure-loss estimate using inlet steam properties.
Pressure drop
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Pressure drop
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Pressure drop per 100 m
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Estimated outlet pressure
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Steam velocity
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Steam density
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Reynolds number
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Darcy friction factor
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Total equivalent length
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Method:
Steam density is estimated from an embedded saturated-steam specific-volume table:
ρ = 1 / v
Steam velocity is:
V =
ṁ ÷
(ρA)
Reynolds number is estimated from:
Re =
ρVD ÷ μ
using an approximate saturated-steam dynamic viscosity of 1.3 × 10⁻⁵ Pa·s for preliminary calculation.
Darcy friction factor is calculated using:
f = 64 / Re
for laminar flow, and the Swamee-Jain approximation for turbulent flow:
f =
0.25 /
[log₁₀(ε/(3.7D) + 5.74/Re⁰·⁹)]²
Pressure drop is then estimated from Darcy–Weisbach:
ΔP =
f × (L/D) ×
(ρV² / 2)
where total equivalent length includes the straight pipe length plus the entered fitting allowance.
This is a simplified preliminary calculation that uses inlet steam density throughout the line.
Steam is compressible, so density increases as pressure falls. For large pressure drops, long pipelines, high velocities, superheated steam or critical-flow conditions, a full compressible-flow steam calculation should be used.
Final piping design should also consider condensate drainage, steam quality, water hammer, erosion, noise, insulation, fittings and applicable piping codes.