Pipe flow calculators
Calculator Description
This is a calculator for calculation of the pressure drop due to friction for known pipe diameter and flow rate of natural gas in pipeline. Applicable for underground and aboveground pipelines with internal pressures between 1 and 100 bar.

Calculate:
 Pressure losses due to friction
 Velocity at both upstream and downstream end of pipeline
 Volumetric flow rate at upstream and downstream end of the pipeline at actual pressure

Input:
 Pressure on the start or on the end of pipeline
 Inside pipeline diameter
 Weight or volumetric flow rate at standard conditions
 Pipeline length
 Natural gas density
Calculator Features
 Applicable for underground and aboveground natural gas pipelines with internal pressure over 1 bar and less than 100 bar and gas lines longer than 1 m
 Input can either be weight or volumetric flow rate on standard conditions (p=101325 Pa, T=288,15 K)
This calculator is a convenient tool for calculation of flow in natural gas pipelines. You can calculate and select inside pipeline diameter, or you can calculate weight or volumetric flow rate as well as pressure losses due to friction.
For other gases than natural gas, compressible flow calculator should be used.
In calculator, gas stream is considered as compressible and isothermal, meaning that density of gas is changing along pipeline due to friction and pressure losses, but temperature stays constant. This kind of flow is possible in long underground pipelines, as heat from the ground is absorbed by flowing fluid and therefore temperature of fluid is not changing even though pressure drops. Also, in order to have this kind of flow, pressure should not change significantly in short distances, like in valves and other local resistances including tees, elbows, reducers and other fittings.
As flow is considered compressible, the calculator can be used for high and medium pressure gas lines. The pressure should be higher than 1 barg on the downstream end and lower than 100 barg on the upstraem end.
For low pressure gas lines when density is not changing significantly, pressure drop calculator for noncompressible flow should be used.
The calculator does not include calculation of pressure losses due to local resistances created in the pipe fittings and valves and changes in pressure as a result of change in pipeline height.
Calculated volumetric flow rates are at standard conditions  pressure of p = 101325 Pa and absolute temperature of T= 288.15 K. In calculation results volumetric flow rates at actual pressures on the upstream and downstream end of pipeline are presented, as well as actual velocities.
Gas velocity in underground pipelines should not be higher than 20 m/s. Higher velocities can lead to significant pressure change, making it possible to reach choked flow conditions at pipeline downstream end.
For high velocity and choked flow with or without local resistances, like valves, fittings, etc., you should use gas discharge calculator.
Please tell me what do you think about this calculator
Q: Calculate pressure drop of natural gas in 1000 m long pipeline with 82.5 mm internal pipe diameter. Gas flow rate is 1000 m^{3}/h at standard conditions. Gas temperature is 288 K and density 0.78 kg/m^{3}
A: Calculation setup:
Input values:
q = 1000 m^{3}/h
L = 1000 m
D = 82.5 mm
p_{1} = 16 bar (irrelevant)
T = 288 K
rho = 0.78 kg/m^{3}
Q: Calculate flow rate of natural gas in 1000 m long pipeline with 50 mm internal pipe diameter. Gas pressure drop is 0.2 bar. Gas temperature is 288 K and density 0.78 kg/m^{3}.
A: Calculation setup:
Input values:
L = 1000 m
D = 82.5 mm
p_{1} = 16 bar (irrelevant)
p_{1} – p_{2} = 0.2 bar
T = 288 K
rho = 0.78 kg/m^{3}
Q: Calculate pressure drop of natural gas in 10000 m long pipeline with 200 mm internal pipe diameter. Gas flow rate is 6000 m^{3}/h at standard conditions. Gas temperature is 288 K and density 0.78 kg/m^{3}.
A: Calculation setup:
Input values:
q = 6000 m^{3}/h
L = 10000 m
D = 200 mm
p_{1} = 6 bar (irrelevant)
T = 288 K
rho = 0.78 kg/m^{3}
Equation used for natural gas pipeline calculation (Renouard equation):
Read more about used theory on compressible gas flow theory page.
If you experience problems with calculator start try to find answers on instructions page.
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