5 replies to this topic

[A mukherjee]

Hii everyone,
I am studying API 520,but I failed to understand what is actually overpressure.Is it the increase in pressure over the set pressure to attain the full lift or what?Also what is the difference between accumulation & overpressure?Why Maximum allowable working pressure is normally greater than design pressure?

[ankur2061]

Mukherjee,

A very interesting article on relief valves including set pressure, overpressure, design pressure and MAWP is available at "Cheresources" itself.
Have a look at the following link:

http://www.cheresour...asiseeit1.shtml

This article is very instructive.

Regards,
Ankur.

[Root]

Over pressure of system is more than the MAWP and its due to any abnormal condition, eg, over firing, malfunctioning of control valves etc.
to avoid from over pressure, set PSV on MAWP to avoid for any major accident, because if abnormality start and you don't where this will stop.

Toor

[Art Montemayor]

A mukherjee:

PLEASE, PLEASE STOP making multiple postings of the same topic.

I have deleted your other identical topic on this Forum. You make no mention that you have made multiple postings in error, so I assume you did it intentionally. Please stop this practice. If you don't know how to follow the procedures for posting, then read the Forum instructions or ask for help - but please stop the multiple postings. The reason for forbidding this practice is common sense.

Additionally, this thread belongs in the Pressure Relief Forum, since it deals specifically with pressure relief valves - and that is where I am moving it.

Thank you,

[A mukherjee]

Art,
I think there is some mistake.I m making the post about PSV for the first time....
Thnxx Ankur & Toor.
Regards,
Arpan

[fallah]

to avoid from over pressure, set PSV on MAWP to avoid for any major accident, because if abnormality start and you don't where this will stop.

Code allows to have overpressure of 10% above MAWP (21% for fire case). If you set PSV on MAWP,you certainly have overpressure,but if you want not having any overpressure you have to set PSV on a value well below MAWP with adjusting its size such that full lift occurs in MAWP.Of course,in these condition the PSV would have larger size (for the same relief load) and range of operating pressure of relevant vessel would be decreased.

Edited by fallah, 30 August 2010 - 01:34 AM.