Tank Nozzle Allowable Loads

Because these forces and moments are interactive with each other, it is the stress engineer's job to tell you what loads he has and for you to to check the tank for them. If the tank cannot support these loads, the pipes must be re-routed so as to reduce the load till the tank can support them, or, you must reinforce the tank.

It is not completely true that you cannot give maximum values for each force and moment but each would be in the absence of the other forces and moments and could not all be used together.

It is much better to check for real loads than to calculate hypothetical strengths.

Humbly suggest that the client be informed that sound engineering advice requires bellows to be fitted for multiple reasons.

You indicate some static and semi dynamic loads that you are considering, but what also about thermal expansion (and how that wil be accomodated) betweent he pipe network and the tank.

What also about the static differences between tank full and tank empty condition?

What also about ground movement during earth tremmors and such?

What about differential movement from each of the nozzles? (Especially during opening and closing sequences for high flow in one branch and not the other.)

I'm NOT a pipe or tank expert, but there are multiple reasons that an expansion bellows would be REQUIRED (Not just recommended) in the situation you have described.