"Rapid fluctuations in pressure" per UG-36?

[mrsteam]

UG-36(3) defines cases when additional reinforcement is not required for nozzles. This however applies to "Openings in vessels not subject to rapid fluctuations in pressure..." Does anyone have a more precise definition? What is considered a rapid fluctuation? Is there a frequency associated to this? How about vessels upstream of a triplex reciprocating pump?

Thank you for your input.

 

[bebe214]

dear mrsteam;

I have seen the contents in a kind of instruction as "~ greater than 1000 cycles of pressure variation exceeding 20% of the design pressure.".

Refer to

http://www.PDHonline.org

(M205)

Best Regards,