ASME UG-140 System Design in Overpressure Protection 1

[Sawsan311]

Dear All,

reference to the subject post, I would like to enquire your interpretation of ASME SEC VIII UG-140 clauses about the role of system design for overpressure protection, do you agree that:

a) if no PSV is relief on and the system design by ISD or SIF SIL-3 function is to eliminate the overpressure scenario, then we would accept their role only if the pressure resulting from the overpressure scenario would not exceed MAWP ? or would not exceed the corrected hydrotest pressure?
b) if an only if PSV is present while role of system design is reducing its relief requirement , then the code allowable accumulation to be considered shall be 116% irrespective to the scenario.

I am bit confused about UG-140 stating the role of system design when the system pressure is not self limiting and referring to MAWP not being exceeded while at the same time in item (5) stating that the overpressure limit shall not exceed 116% of MAWP and then stating test pressure. Is there a rational behind the 116% being correlated to 130% multiplier for the corrected hydrotest pressure.

Thanks

Regards,

 

[The Obturator]

ASME VIII UG-140 Describes what is known as a HIPPS - High Integrity Pressure Protection System which essentially does away wth pressure relief devices.

I'm no expert on detail but entering ASME VIII HIPPS in a search engine will bring up many discussion papers such as

https://bluefieldsafety.com/2017/08/protection-under-pressure-understanding-hipps/

As for your query on obtaining the hydro pressure, I can only think that 116 MAWP + 30% gives you the typical 1.5 factor for hydrotesting.

Hope this helps.

Per ISO-4126, only the term Safety Valve is used regardless of application or design.