PSV Sizing

[mcompound]

Hi All,

I am trying to size a PSV for a 250 psig pressure vessel discharging into a header. The header has 2 thermal sized PSV discharging into it at 450 psig from other sources. The header routes to a flare stack. The vessel contains mercuptan, which boils at 95F. I don't do much PSV, so I am struggling with this. I know how to calculate the built-up backpressure from pipe friction. I'm not sure about the superimposed from the flare and possibility of other PSV discharging into header. I am also not sure if I should liquid or vapor size. The mercuptan is liquid, but in a fire case it would be vapor I guess?

Has anybody seen any worked examples for a similar situation?

Much thanks

 

[Latexman]

I have not seen examples like these in the public domain, because my company has a strong PSV training program. So, no need. However, your company/client should have PSV sizing records on the 2 thermal PSVs going to the same header and flare. Look at those. Is there another PSV header or two at the site? The unit next door? A site in another state/province/country? If you are lucky, does your unit have a twin somewhere? That's quite common. You should be able to get those records within the same company, if needed. You might meet someone with more PSV sizing experience along the way, maybe a mentor on the subject.


Good luck,
Latexman