B31.3 vs. API 521

[Patassa]

All, I'm down a rabbit hole trying to understand if there is a conflict between the 10/13 rule for exchanger tube rupture over pressure considerations in 521, allowing me to not install a PSV on the low pressure side, as long as the high pressure side doesn't exceed my corrected hydrotest pressure on the LP side. My issue is this, 521 applies to the upstream and downstream systems (piping) of the low pressure side as well, but the way it's seemingly being applied is that if the high pressure side doesn't exceed the corrected hydrotest pressure of my piping also then I'm OK. However, B31.3 only allows exceedences of up to 1.33x design pressure for a short amount of time, assuming all other conditions are met. I can find no where in 31.3, where I'm told I can overpressure up to the hydrotest pressure. Does anyone know more of the background of how 521 got here and is there any issues with 31.3 in this scenario? Thank you

 

[1503-44]

You certainly cannot overpressure the B31.3 part of the system.

See

https://www.e2g.com/consulting-serv...systems/heat-exchanger-tube-rupture-analysis/

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"