Hi,Our Heat exchangers was designed for 365 PSI MAWP and Constructed as per ASME VIII Div 1. Originaly it was hydro tested at 522 PSI. Now our client request us to test it at 102 PSI of Air. We have a doubt of pressure testing due to stored energy of air in which our exchanger can withstand for all connection. The tube to tube sheet connection is only expansion (by rolling) and tubes inside 1quot; X 1.65 mm WT.If any one can help us mainly for Safety reason at this high pressure at 25 m high elevation at site, it would helpful for us.Thanks,
The common practice for a pneumatic pressure test is to test to 110% of the MAWP. That is very safe and is done all of the time for all kinds of pressure containing equipment. The only concern with a heat exchanger for any type of pressure test is the differential between the shell and tube side. The concern is not the rolled tubes but rather the force on the tube sheet. If you are concerned you can pressure both the shell and tubes as the same time to protect the tube sheet. The only problem with this is the tube to tubesheet connections will not be tested. I am surprised that the original hydro test was only 522 psi rather than 1.5 times 365 or 547 psi. That is the usual code requirement and practice for hydro tests.
You already tested the resistance of the exchanger at 522 psi, if it passed the test with no leaks (I mean 0) at a minimum of two hours, the equipment is ready, I pressume the customer may be concerned by the fact that air may leak through where water molecules could not, this is a valid concern but for this case considering that the initial test was done at almost 5 times more the pressure he now desires test, you can make it with no problems expected. It is better to find now any possible leak than to have to dissasembly the pipe-work and stop production after it is installed.
