10 replies to this topic

[reyeaj]

 

 

I am student in practice at a Colombian company.  I need to calculate a volume required to doing a leak test in a pipeline of 175 m length and 6 inches of diameter.  The leak test will be at 6,000 psig.  I would like to know the volume of nitrogen I need for the leak test.

 

Thank you for any cooperation.

 

Álvaro Reyes

[Art Montemayor]

^Alvaro:

 

^{I don't know why you would leak test the pipe with high pressure nitrogen rather than using a hydotest (with water).  If you have to do it as you propose, then I would advise you to do it through a sub-contractor who is prepared to undertake such a test.  I believe you could do it using the services of a Colombian compressed gas company - such as Praxair, Air Liquide, BOC, etc.   The way that such a test would be done is using a supply of liquid nitrogen in a portable container, a high pressure cryogenic piston displacement pump, and an ambient vaporizer.  A cryogenic piston pump can easily reach the 6,000 psig test pressure.}

 

^{However, such a pump isn't readily available to just anyone.  That's why you have to make arrangements with a local compressed gas company who would have access to such specialized equipment.  Testing with compressed gases is a very touchy and risky operatio.  I would not do what you propose unless it was absolutely the only acceptable manner.  That type of test requires a lot of safety training an precautions prior to attempting it.  Testing with water is a lot safer and easier - except that you have to dry the tested pipe afterwards.}

[reyeaj]

Art Montemayor

 

 

i apologize  the pressure is not 6000 Psi is 600 Psi, the Company uses nitrogen for its leak test, I need to calculate  how much nitrogen should be compressed to 600 psi in pipe.

[Bobby Strain]

You can easily determine the quantity by simply getting the nitrogen density from a readily available Mollier chart. 

 

Bobby

[reyeaj]

Art Montemayor

 

you are right, the subcontractor will do the leak test , but i need to give them the calculation of volume

[reyeaj]

Bobby

 

the problem is the following, i need calculate nitrogen's volume, that i could compress in the pipe  

 

my solution 

 

i found density of Nitrogen to 600 psi and 30 °C, i know pipe's volume  and I found the mass of equation(density=mass/volume) but i do not know calculate, how much nitrogen that can i compress in the pipe 

[Art Montemayor]

^Alvaro:

^{Bobby is correct. The easiest way is to obtain the density of the nitrogen at the conditions you want to test to.  You do this by going to:}

^{http://webbook.nist....hemistry/fluid/}

^{There, you will find the density of nitrogen at your compressed conditions.  You multiply this density by the pipe's volume.  You now have the mass of nitrogen in the pipe at test conditions.  You multiply this mass by the specific volume of nitrogen at the other (standard?) condition that you want to measure it at.}

^{It is that easy.}

[samayaraj]

Please find attached the excel sheet for nitrogen flow calculation.

 

 

Hope this helps you

 

Regards,

Samayaraj

Attached Files

•  Sam Nitrogen flow calc.xlsx   10.6KB   260 downloads

[Art Montemayor]

I believe Sam's calculations are wrong and I am attaching here a Rev1 to his workbook where my detailed calculations are shown.

 

 Sam Nitrogen flow calc Rev1.xlsx   13.39KB   641 downloads

[reyeaj]

Sr.  Montemayor

 

 

thank you so much, you solved my problem. you were right, the problem was very easy

 

Greetings from  Colombia

[samayaraj]

Dear Mr. ART,

 

Thanks for your valuable comment. I made a small mistake. I've attached the corrected excel sheet and i found the quantity nearly equal as you calculated.

 

 

 

Regards,

Samayaraj

Attached Files

•  Sam Nitrogen flow calc Rev2.xlsx   15.49KB   558 downloads