Sizing of relief valve for LPG bullet

[chen4]

Dear all,
Please help me. I have an issue with basics.

Problem follows:
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Make a spreadsheet for the sizing of relief valve for commercial LPG bullet (mainly propane) using API 520. Temperature of atmosphere where the bullet is kept (above ground) varies from 10°C to 35°C (50°F to 95°F).
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Which procedure in API 520 should I use?
>procedure for liquid OR
>the procedure for vapor-liquid?

As u know, in API 520, different procedures are given for - critical, sub-critical flow, liquid relief, sizing for two phase liquid or vapor etc. So I am confused:-(
The LPG bullet would be filled 85% of their water capacity, the remaining space being taken up with vapor (as I read from some websites).

(I already made the spreadsheet for various conditions given in API 520. But I need to choose which procedure to use specifically for LPG bullet )

If I haven't given enough info to solve the problem, please let me know.

[Nephilim]

This depends on the overpressure scenario's you have identified and quantified, for fire you would use the vapour sizing equations but for overfilling you would use the 2-phase equations.

[mobek]

So, was this part of your job/work or you're doing it for school or for fun?