Gas Compressor Power calculator
What it costs to put the pressure back that the line just took.
Oil & Gas · Interactive Engineering Model
Pipeline Pressure Drop Calculator
Outlet pressure · Velocity · Erosional limit
Change the duty and see how close the line is to a limit, not just how much pressure it loses. Outlet pressure from the isothermal flow equation, with the friction factor taken from the flow itself and the acceleration term solved by iteration rather than dropped.
Throughput at standard or contract conditions.
Length of the segment between the two pressure points, with no station in between.
Actual bore, not the nominal size. Capacity scales close to the two-and-a-half power of it.
Absolute pressure at the start of the segment.
Start from an example: 100 MMSCFD through 100 km of 590 mm line at 70 bar a →
Advanced parameters5
- —Outlet pressure
- —Pressure drop
- —Drop as a share of inlet
- —Drop per kilometre
- —Velocity at outlet
- —Erosional limit at outlet
- —Velocity at inlet
- —Mass flow
- —Reynolds number
- —Friction factor
Move a parameter and the line answers: the pressure left at the far end, how fast the gas is moving when it gets there, and whether the duty can be carried at all.
The link carries the figures you entered, in the part of the address that is never sent to a server.
Change one assumption at a time. The model updates from the same calculation used for the reported result.
Try this
Increase throughput while keeping the line and inlet pressure fixed. Follow the pressure profile until the requested duty can no longer be carried as a steady-state solution.
How the model works
- The dutyA standard flow of gas becomes a mass flux once the bore is known. That flux, not the volume at standard conditions, is what the line has to carry.
- The lossPressure falls along the line as friction takes its share. The curve bends because the gas expands as it goes, so it moves faster the further it travels.
- The limitAt the outlet the gas is least dense and fastest. The marker there is the API RP 14E screening velocity — hydraulics that work on paper can still erode the line.
- No solutionPast a certain duty the line cannot carry the flow from this inlet at all. The model says so rather than reporting an outlet of zero, and the scene stops with it.
Need a production-ready pipeline model?
We can extend this calculation to real elevation, compressor stations, operating telemetry and your actual pipeline data.
Calculation basis 5 steps · view the method →
Mass flow = standard flow × density at 0 °C and 101.325 kPa—Reynolds number = mass flux × diameter ÷ viscosity—Friction factor from Swamee-Jain on that Reynolds number and the relative roughness—P₁² − P₂² = G²·Z·R·T·(f·L/D + 2·ln(P₁/P₂)), solved for P₂ by iteration—Velocity at the outlet, where the gas is least dense and therefore fastest—
Assumptions & limitations Screening estimate for hydraulic checks and capacity questions · 8 assumptions →
This is a screening calculation for steady, isothermal, single-phase gas in a horizontal line of constant bore. It excludes elevation change, liquid holdup and two-phase flow, heat transfer with the ground, fittings and valves, compressor station effects, transient and packing behaviour, and any real-gas treatment beyond a single Z. Design, rating and regulatory work require a proper hydraulic model and the applicable pipeline code — this figure is for orientation only.
- Steady, isothermal, single-phase gas flow in a horizontal line of constant internal diameter.
- Elevation change is ignored, which matters on hilly terrain and for dense gas.
- Liquid holdup and two-phase behaviour are not modelled; any condensate changes the answer substantially.
- Gas properties — Z, molecular weight and viscosity — are taken as constant along the segment.
- Fittings, valves, bends, station piping and metering losses are excluded.
- The erosional velocity uses API RP 14E with C = 100 in field units, a rule of thumb rather than a limit derived for your service.
- Transient and line-pack behaviour is out of scope: this is a steady-state answer.
- Where the flow cannot be carried from the given inlet pressure, the tool reports that there is no steady-state solution rather than an outlet of zero — and near sonic conditions this model stops being applicable well before that point.
Worked examples
- 100 MMSCFD through 100 km of 590 mm line at 70 bar a
Open with these figures → - Doubling the throughput to 200 MMSCFD
Open with these figures → - The same duty through a 400 mm line instead
Open with these figures →
What this model reveals
More throughput does not always mean simply a little more pressure drop. As pressure falls, the gas expands and accelerates, which changes the loss along the line. Eventually the requested duty may no longer have a valid steady-state solution from the available inlet pressure. The useful question is therefore not only how much pressure the line loses, but how close the operating point is to a physical limit.
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