MAWP and Design Pressure

[kunalsj]

I am currently checking an fixed tube heat exchanger design with the help of Compress as per Section VIII .

Since I am restricted to using standard pipes due to availability for Shell and Nozzle material, the MAWP of the said HX is 3 times higher than that of the design pressure and the nozzle flange is the weakest link.

In this case, do I have to carry out the hydro test at 1.3 x MAWP or does the code permit the manufacturer to use a different/lower MAWP?

 

[SnTMan]

kunalsj, you are permitted by UG-99(b), footnote 36 to "not calculate" the MAWP for the vessel, in whch case the design pressure forms the basis for the test pressure. As you presumably have a combination unit you should also see UG-99(e).

Regarding fixed tubesheet exchangers it is my practice, and I'd say a fairly common practice, to set the MAWP for each side of the exchanger to its' design pressure. Due to all the things you don't know. Regardless what the software tells you.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[MikeG7]

If the spec for testing is UG-99(c), then 1.3x calculated pressure (MAP)
Or if you have the choice you can limit MAWP to design pressure and test as UG-99(b) like Sntman says

 

[kunalsj]

Thanks SnTMan & MikeG7.

So to conclude, as per footnote 36, it is not mandatory for the designer to calculate the MAWP of the system. Instead one can limit the MAWP of the system to design pressure and use the same to calculate Hydrotest.

 

[SnTMan]

Correct

The problem with sloppy work is that the supply FAR EXCEEDS the demand