7 replies to this topic

[sirooseven7]

One of our field operator recently performed a pressure test to determine if there is a leak in one of our heat exchangers. He closed both sides of the tubes and pressured it to 400 psig. He says that the pressure held for over an hour and therefore he does not believe there is any leak. However, I have recently gotten the sample for the inlet and outlet of the heat exchanger and they are very different (which tells me that there may be a leak).

 

My question is: is it possible that he has done the test incorrectly and thus failed to detect the leak?

 

Any advice would be much appreciated.

 

Thank you,

[shantanuk100]

Hi Siroo,

 

Could you give more detail as to the type of exchanger, fluids involved, and what you found on both shell and tube that made you think a leak might be happening ?

 

Regards,

Shantanu

[breizh]

Hi ,

Can you enlight us about the leak test ?  Can you share your SOP ?

Was it a water leak test ? Did he use calibrated pressure Gauges? What was the precision of the measurement ? 

 

Hope thsi helps

 

Breizh

[sirooseven7]

Thanks for the reply. What I am told is that the operator closed off the entire tube side with some flanges. He then pressurized it with Nitrogen to 400 psig. His thinking is that if there is a crack/leak, the pressure should decrease over time. I believe he does have a calibrated pressure gauge but I am not sure.

 

This is a natural gas treating process. We have low Btu residue gas coming into the tube side and inlet gas with high Btu content entering the shell side of the HEX. I suspected that there is a leak and asked for a sample of the inlet residue gas and outlet residue gas. The Btu of the inlet is 1200 Btu/ft3 and the outlet is 1300 Btu/ft3 (they are supposed to be the same).

 

Thank you,

[fallah]

Siroo,

 

As appeared the leak test has been done at ambient temperature and 400 psig, but you fail to tell us about the operating and design pressure/temperature of the tube side. Then please provide these info...

[sirooseven7]

Hi Fallah,

 

The tube side is design to handle up to 1000 psig from -30F to 90F.

[fallah]

 

The tube side is design to handle up to 1000 psig from -30F to 90F.

 

Siroo,

 

Then it's not so strange having leakage in real process conditions with the pressures well above 400 barg and the temperature well below ambient temperature; i.e. the conditions well different than those under which the leak test has been performed...!

[breizh]

Hi ,

There is a typo on fallah's reply ( Pressure unit is PSIg) .  Using 400 PSI g N2 to perform the test is quite scarry ! Safer to use water and  handpump , better control and easy to visualize the leaks .

 

I still remember a fatality occuring during air pressure test , the shell burst .....!

 

My view .

 

Breizh

Edited by breizh, 26 April 2016 - 07:39 PM.