oohhh....
PSV on a tank roof??????? i hope the nozzle is close to the tank wall!!!
that sound wrong! are you sure its not a vac breaker or breather???
Whilst i agree that for large tanks, roof nozzles are a bad thing, the vendor has put on one!!!!!
I would review the requirement for roof mounted PSV (or any nozzles) and then inform the vendor that either he provides some reasonable allowables (no matter how low), or you take your buisness elswhere.............
8m is not a large tank.
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Best Regards