Heat Exchanger hydrostatic shell test pass but tube hydrostatic test fails ? 2

[erkuts]

Hello,

I would like to ask a question about hydrotesting.

We have a fixed tubesheet heat exchanger in our facility and it pass shell hydrostatic test at 9 bar but it fails when we test tubes at 9 bar.

Pressure gage decreases and we observe a leakage shell drain. What is your recommendation? Which point we are missing ?

Best Regards,

 

[Dhurjati Sen]

You have got into a vicious cycle of repeated shell test and subsequent tube test. Check for roll leaks, seepage from any plug, etc.

DHURJATI SEN

 

[JR97]

erkuts,

When you perform the shell test the tubes are in compression. They are in tension for the tube test. Was the shell test performed before the tube test? If so, it is possible the tube survived in compression but failed the second test when put in tension. The other scenario I can think of is the leak is closed by the compression force to the point leakage is too small to detect. In either case, you may have success locating the leak by re-running the shell test at a lower pressure where the failed tube(s) will allow water to pass without being fully compressed.

JR97

 

[erkuts]

Hello,

Thank you for advice.
As you mention, we decreased tube test pressure and started tube test with 4 bar and increased it to 8 bar step by step. It leaked at 8 bar.

We will perform rolling works in the tubesheet. I hope, rolling will be solution for us.

Best Regards,

 

[Dhurjati Sen]

Dear erkuts,

Since this is a free forum, I am an irregular visitor here so sorry for the delay. I want to add to my earlier post.

Look, why should we carry out hydro-test of old exchangers at the pressure of as new condition?

Why are we unnecessarily causing plastic deformation to the tubes after so many years of service by testing them at that pressure?

Instead, we can always test them at the MAXIMUM OPERATING PRESSURE (not mawp) or the DESIGN PRESSURE.

These are technical issues but rarely taken by engineers. The managers need to be convinced.

Hope you are out of the vicious cycle by now.

Cheers.

DHURJATI SEN