I am performing a stress analysis on a replacement tank line for hot crude oil service. All considered piping was found to be within the code allowable. My concern is at the tank line to tank bottom connection. I don't have acceptance criteria as far as allowables go for this connection.

It is a vertical connection that is welded directly to the tank bottom and resembles more of a drain line than the typical API 650 horizontal shell nozzle. Inside a concrete vault, the 36" tank line is connected to the tank bottom by a short radius 90 deg ell and a 48" x 36" reducer. The reducer is welded directly to a 48" opening in one of the bottom plates of the annular bottom ring. There is also a 0.75" thick reinforcing plate at the opening.

Can Ceasar II validate the tank bottom connection loads as acceptable or not? Are there any suggestions on allowables other than rule of thumb? The connection doesn't fit the API 650 nozzle loading critera. WRC 107 is geared toward pressure vessels (not storage tanks?). Any suggestions would be appreciated. Thanks.