Caesar II has a calculation module for Air Fin Exchanger nozzle loads in accordance with API 661. Caesar handles only one nozzle, but API 661 (clauses 4.1.10.2 and 4.1.10.3) covers multi-header and multi-bundle configurations.

I am confused by the wording and the intent of the clauses. Firstly, 4.1.10.2 talks of summing forces and moments for each nozzle on a header and gives limits for the sum. However, as we all know, the resultant moment depends on the applied moments and the applied forces multiplied by their lever arm.

The lever arm depends on the location of the moment axis. API 661 doesn't seem give any guidance on where this should be. Can anyone clarify this?

In addition, the same clause gives numerical limits to these moments and forces. These are independent of nozzle size. Is this sensible?