2 replies to this topic

[phoenixmoca]

As we all know it is generally recommended that the pressure loss at the inlet of pressure safety valve is less than 3% of set pressure. But while conducting the pressure loss calculation which should be applied, the required capacity or rated capacity?

I agree with the API 520 Part II in which rated capacity is selected. So my question is how to persuade others to follow the requirement of API 520 Part II?

Thank you in advance.

[Pilesar]

As I understand the purpose of the 3% rule, it is designed to avoid relief valve rapidly opening and closing such that it destroys itself. The 3% limit was selected by committee as a guideline that was not originally intended as an inviolable rule for every fluid and relief condition. However, due to lawsuits and legal judgments, relief designs usually go to extraordinary lengths to comply with the rule. There may well be other basis for design that would be perfectly safe. The convincing argument for me is "how would I convince a court jury that I followed recommended industry practice?" This consideration guided me in so many engineering choices I have made. Even where my engineering judgment allowed less conservative selections, the financial risk to my company of lawsuit often dictated final design choices.

[latexman]

But while conducting the pressure loss calculation which should be applied, the required capacity or rated capacity?

I agree with the API 520 Part II in which rated capacity is selected. So my question is how to persuade others to follow the requirement of API 520 Part II?

 

Yes, definitely the PSV rated capacity, because that will be the flow when the PSV is activated.

 

If you are not in a position of authority over "others", then peer pressure.