vacuum breaker

[oilngas5356]

This question may not be related to safety relief valve but I decided to put it on here since I believe people with this experience would be better able to answer this question.

I am just wondering how a vaccum breaker is different than conservation vent or vacuum relief valve and how it is sized. The origin of my thought came from a problem that I came across. I am working on a catalyst storage drum which has a design vacuum of 5 psi external. This drum is not an API 2000 vessel. It is an ASME SEC VIII vessel with a design pressure of 32 psig and operting pressure of 25 psig. However, it was noticed that the vessel can see a vacuum of 9 psi when its closed after catalyst loading and remains closed for a certain period and that means it requires vacuum protection. I believe conservation vent are specially for low pressure tanks so we need a vacuum breaker which can be used in certain situation. However to me it seems like it works the same way as a conservation vent. But I wonder if it can be sized the same way using API 2000 table for thermal inbreathing.

Any opinion on the situaion and vacuum breaker is greatly appreciated.

 

[djack77494]

Excellent question oilngas. Your vessel must follow Sec.8 rules and not those for API tanks. Though there are similarities in the methods, there are also differences which must be respected. The Vacuum Relief Valve that you will need to specify is NOT likely to be constructed like a conservation vent; it will more likely resemble a PSV.