Vessel for Hydrotest over MAWP

[jm2024]

Hello all.

I have designed two electric immersion heaters per Appendix 41 of Section VIII div I. Design pressure is 2500 psi at 700°F. Hydrotest pressure per UG-99(b) is 5372psi. The customer was hoping for us to use one of their vessels in order to hydrotest the heaters. Their vessel's MAWP is 2660psi at 700°F. The vessel cannot be taken above the stamped MAWP, correct? I have run calcs for the vessel that show it will not fail at the 5372psi. However, since it's stamped for 2660psi, nothing will allow us to go beyond that, right? We would need to re-rate in order to use it?

Thanks for any input.

 

[goutam_freelance]

Asper VIII-1 clause UG-98, each MAWP has a coincident temperature. Also, the MAWP can be specified for more than one temperature condition.

So, if the Inspector certifies the MAWP at room temperature(after calculation) in addition to the existing MAWP at operating temperature, then if the new MAWP is equal to or more than 5372 psi, then it will be possible to subject the vessel to 5372 psi.

But in principle, your statement is correct; additional certification will be needed.

 

[jt1234]

Your focal point is the hydrotesting, not the MAWP. That means you shall ask customer what is the hydrotest pressure for the vessel. If it is below 5372 psi, you shall not use that vessel to do hydrotest unless you want to redesign your heater to lower the test pressure to match vessel's.
If this is a new vessel and has not been hydrotested, you shall ask vessel fabricator to agree upon using higher test pressure to match 5372 psi, not you to run the calc saying to your customer it will not fail. Doing that you will be liable for any thing goes wrong.