Volume and pressure 1

[Classy68Cat]

I found this site and was looking for some help. The local gas companies are calling wanting us to help them with pressuring their lines for testing. Can anyone give me a formula for determining volume in pipe. An example would be: They want to use nitrogen to pressure their line to 50 psi, in 6 inch pipe, and the length is 500 feet. How would you detemine the amount of cubic feet of nitrogen required?
And could that formula work on any size pipe and length?

 

[JStephen]

Cross sectional area times length = volume.

Pi/4 x ID^2 x L with all dimensions in feet.

Use ideal gas law to convert atmospheric cubic feet to pressurized cubic feet if req'd (at low pressures, that is).

I'm not that familiar with purging. But wouldn't you have to run nitrogen through the line a while first? IE, wouldn't you waste quite a bit of it before pressuring up?

 

[quark]

(([Π]xD²xL)/4)x(P/Pa), where P is absolute pressure required, Pa is atmospheric pressure, D is internal diameter and L is length.

In your example this will be,

3.142x0.5²x500x64.7/(4x14.7) = 432 cu.ft at atmospheric pressure.

You can use this approximate formula for any length.

Regards,

 

[quark]

This is second time in this week that I made simultaneous posting

 

[25362]

The opening formula given by quark is OK. Be careful in using consistent units for absolute pressures and pipe dimensions.