Pipe size for nitrogen gas 1

[ben3929]

Need help to calculate pipe size for nitrogen gas (from tank to pressure regulator). known values are inlet pressure from tank 1500 psig, length of pipe from tank to pressure regulator 300 ft, flow rate 600 SCFM (17000 slpm), assume 5% pressure drop for fittings, pipe end will be connected to pressure regulator to reduce pressure to 1000 psig. I calculated dia. 1" pipe and need to make sure this is correct.

 

[georgeverghese]

Max pressure drop (and noise) in the line from tank to regulator should be when the tank is at its lowest permissible operating pressure, which is ??

 

[ben3929]

Assume the inlet pressure from tank is constant. There is another pressure regulator at the tank station.

 

[georgeverghese]

N2 gas flowrate 1200kg/hr at approx 100barg,rho=118kg/m3

For 1.5inch, v=2.4m/sec, dp = 18kpa/100m; For 1inch, v= 8.3m/sec, dp = 425kpa/100m

dp for 1inch is excessive, go for 1.5inch

 

[hacksaw]

I come up with NPS 1-1/2" as well, at 1" you have 6.5 psi per hundred feet

 

[ben3929]

Thanks for your response, both.
I am sure if I understand the math correctly, if possible would you show how you come up with 1.5" pipe diameter.

 

[georgeverghese]

You will find the expression for pressure drop in incompressible single phase fluid flow in any Uni / college textbook on fluid hydraulics. Also from Crane TP 410. This selection based on unit pressure drop constraints. You may be still okay with 1inch provided you are sure of all fitting losses.

 

[hacksaw]

Crane 410, Marks, Perry's, or std text book(s) is a good start

Flow Meter Sizing Calculation
Meter : Pipe Flow Calculation

***** PROCESS DATA *****
Pressure 1500.0 psig ( 1514.7 psia )
Process Temperature 80.0 Deg F
Ambient Pressure 14.696 psia ( 0 ft. m.s.l. )
Latitude 45.0 Degrees Lat. N
Base Conditions 14.696 psia , 32.0 Deg F
Molecular Weight of gas 28.010
Specific Gravity 0.967
Specific Volume 0.135 cu.ft./lb
Z Factor (Redlich-Kwong) 0.990
Z Factor @ Base Conditions 0.999
Isentropic Exponent 1.752
Viscosity 0.019 centiPoise
Speed of Sound(Approx) 1142.1 ft/s
Pipe Reynolds No. 573585 | 573585
Pipe Velocity(ft/s) 7.5 | 7.5

***** FLOW DATA *****
Flow 600 SCFM
Pipe Reynolds No. (Rd) 573585 | 573585
Mean Fluid Velocity (Pipe) 7.5 | 7.5 Ft/Sec
Line Loss 0.68 | 0.68 Psi / 100 ft
Friction Factor (f) 0.0207| 0.0207
Pipe i.d. (D) 1.6100 Inches