Hi, I'm completely new to tis forum, but hope I get in the mood pretty soon!
I'm from Argentina, please excuse my poor english.

My question is quite simple, I've read a lot of discussions and never seemed to get a straight and clear answer to this:

According to API 520, superimposed backpressure is the static pressure at the discharge of the valve the moment it is about to open. Built-up backpressure is the pressure at the discharge of the valve as a result of the flow through it.

My question is: Built-up backpressure is the TOTAL pressure at the discharge of the valve, or just the difference between the total and the original superimposed?

Thank you very much for your comments, Happy Holidays!

Luis

If you go down one page in this forum, you see a topic posted on 24th April 2004 named "backpressures". It shows that although definitions in API RP 520/521 are quite clear, some people don't agree with these definitions.

Definition in API RP 521, section 1.3.6: "built-up back pressure: The increase in pressure in the discharge header that develops as a result of flow after the pressure relief device or devices open."

And in 1.3.3: "back pressure is the sum of the superimposed and built-up back pressures"

So according to API RP 521, built-up back pressure is the difference between the total and the original superimposed.

Thank you gvdlans, I already read the Backpressures topic, that's why I called this one Backpressures II.

And yours is just the straight answer I was looking for. Thank you very much, and Happy Holidays.

Luis