API TANK ROOF NOZZLE

Hi,
I am doing analysis of line connected to API tank.The tank is 8m in diameter.
The line which I am analysing is 8" PSV line and nozzle is located on tank roof. As tank diameter is less than 36m,Appendix P of API 650 is not applicable in my case.
In absence of any allowable nozzle loads , I forward calculated loads on nozzle for confirmation to tank vendor.The tank vendor replied that"API Code does not give any guide line for the nozzle load verification located on the roof, and it is the industrial practice not to apply any concentrate load on the tank roof".
Please give me suggestion/advise how to proceed....

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.