How to dump to 50% of vessel's design pressure

[seuenergy]

Hi all,

In API 521, section 4.6.6 states:" For pool fire exposure, this generally involves reducing the equipment pressure from initial conditions to a level equivalent to 50% of the vessel's design pressure within approximately 15 min."
I am wondering how we could get 50% of design pressure if the set pressure is little lower than design pressure. Thanks for your reply!

 

[The Obturator]

The API 521 (2020) Paragraph 4.6.6 that you reference does end with the statement "Depressurising disposal systems are discussed in 5.3.3". Maybe have a read of that.

Since you posted in the safety/relief valve forum, be also aware that Pressure-relief Valve manufacturers of old, did catalogue the availability of their spring operated pressure relief valves, fitted with a top (cap) mounted air motor that allowed the user to make the PRV to act as a dump valve. ie., open and stay open at pressures below set pressure. I'm sure they could do it now, and also with a pilot operated valve by having a solenoid fitted, that is if any of todays companies are willing to look at it properly rather than give you a AI type answer of 'it's not in the catalogue'.

 

[shvet]

the set pressure is little lower than design pressure.

The set pressure of what? A rupture disk or an ESD?
Are you confusing the PSV blowdown pressure with the pressure vessel depressuring?
More details = better answers