Document / Project Reference
Single Phase Gas Hydraulics
Darcy-Weisbach · Swamee-Jain · Real-Gas Density · Mach Screening
Screening-level calculation — not a code-compliant design document
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INPUT PARAMETERS
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  |  Hazem ElMancy — Gas Hydraulics
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HYDRAULICS

Single Phase Gas Hydraulics

Single-phase gas line hydraulics using Darcy-Weisbach friction, Swamee-Jain friction factor, real-gas density, Mach number, rho-v-squared and industry best-practice service checks.

Crane TP-410API RP 14ESwamee-JainGPSA
All Calculators
Input Parameters
Flow & Operating Conditions
Must be > 0
Mass flow basis; not Sm³/h or MMSCFD.
Must be > 0 absolute
Absolute pressure basis only. Convert barg/psig before entry.
Required; absolute temperature must be > 0 K
Must be > 0
Pipe Selection
Must be > 0
Screening defaults only; confirm project piping class and vendor data.
Default clean commercial carbon steel.
Must be ≥ 0
Fittings / Minor Losses
Fitting / ItemQtyK eachK totalRemove
ΣK0.000
Minor losses are added as ΔPK = ΣK × ρv²/2 using calculated gas density and line velocity. K-values are screening defaults; use project/vendor values for final design.
Gas Properties
Must be > 0
Must be > 0
Must be > 1
Must be > 0
Manual gas-property mode. Enter MW, Z, k and viscosity from validated project basis, gas-mixing tool, HYSYS or UniSim.
Service Check
Industry best-practice velocity, Mach, rho-v² and ΔP/km screening only.

Enter parameters and click Calculate.

Methodology

  • Gas density: ρ = P·MW/(Z·R·T), using absolute pressure and Kelvin temperature.
  • Velocity from actual volumetric flow: Q = ṁ/ρ, v = Q/A.
  • Darcy-Weisbach friction pressure drop: ΔP = f·(L/D)·(ρv²/2).
  • Friction factor: Swamee-Jain explicit approximation for turbulent flow; laminar flow uses f = 64/Re.
  • Mach number screening: a ≈ √(k·Z·R·T/MW), Mach = v/a.

Assumptions

  • Steady-state, single-phase gas; no liquid entrainment.
  • Isothermal, constant-density screening using inlet pressure and temperature.
  • Acceptable for preliminary line sizing where ΔP/P_in is low, typically below about 10%.
  • Pressure input is absolute. Gauge pressure must be converted before entry.
  • Flow basis is mass flow, not standard volumetric flow.
  • Gas properties may be entered manually or estimated from embedded gas-mixing composition. PR/SRK use vapor-root Z only with kij = 0 and are screening-level, not rigorous flash calculations.

References

  • Crane TP-410: Flow of Fluids Through Valves, Fittings, and Pipe.
  • API RP 14E: Offshore Production Platform Piping Systems.
  • Swamee & Jain (1976): explicit equations for pipe-flow problems.
  • GPSA Engineering Data Book and Perry's Chemical Engineers' Handbook.