Relief valve inlet pressure loss

[jon...@sbcglobal.net]

At work I've been requested to verify relief valve capacity for one of
our plants built in the late 1970's. Since the orginal design was
done, spare relief valve, isolation valve and rupture disk have beem
added to the equipment nozzles. These modifications have not always
kept to the ASME recommended practice of keeping inlet losses to 3%.
Has anyone else experienced a similar situation and how has it been
handled?

[Srinivasa Rao, Koyyalamudi]

The best Sizing Standard for Relief Valves are API Recommended Practice
520. Another good resources that is available that had good exaple
calculation to verify and design is Crossby Relief Valve Design Manual.

I guess you could download the same from the following website
http://www.tycovalves-na.com/getlit.asp?lit=ld/CROMC-0296-US.pdf
Regards,
K.S.Rao