Volume of Nitrogen for Leak Testing

[shaff]

I need to leak test a 10" - 100 meter long pipe at 20 Barg with Nitrogen

What is the volume of nitrogen required for this leak test.

Any calculation basis will be much helpful

Thanks

shaff

 

[LittleInch]

Try 20 times the internal volume - You won't be far off and gives you the answer in standard volume.

This is pretty basic gas law stuff.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[quark]

21

 

[racookpe1978]

Yeah. I'd go 21x, if not 22x or 23x, the original internal volume. The gas will expand (cool) from the compressed gas tank, and you want at least 15 psig extra to force the N2 to "flow" into the pipe.

Does your procedure require any purge to get rid of the residual air in the original pipe and equipment? (Remember you will need to add all vent and drain lines, valves, tanks, pumps, filters, ...)

 

[LittleInch]

My guess is the OP is just trying to see how many bottles he needs so whether it is 20, 21 or 25 doesn't really make much difference...

Racookpe - Did you mean contract instead of expand?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[racookpe1978]

Well, let me think about it.

If the original poster wants to leak test a pipe originally filled with air at 0 bar (gage), then he's going to connect a high pressure room temperature HP bottle of N2 up right?

Then that bottle's gas will expand into the low-pressure pipe, drive out the old low pressure air (at 1-4 psig over ambient pipe pressure) until he stops purging the N2 out. With the purge valve now shut, then I figured the HP N2 bottle's gas would expand into the pipe and equipment volume until the pressures equalize. The bottle's gas and the pipe's gas would now be cooler than before since all of the heat of compression (from bottle pressure to equalized pressure) of the gas in the pipe would almost immediately be lost through the pipe walls and supports and the pipe thermal mass.