I have to re-analyze a system done years ago by another analyst and placed in operation. It is now intended to replace a number of valves with new ones of a much greater weight. There are a number of hangers (21 to be exact), which not only support pipe but are also used to support heat exchangers, a column, and a pump. For one of the 21 hangers whihc is located on a run of pipe between the pump and HEX, I've been experimenting with the effect on the load CAESAR reports by running through all combinations of free restraint nodes. That is- I start by not releasing the pump nor the heat exch. nozzle nodes, then just the pump, then just the HEX, and finally both. You would expect, other things being equal, that the hanger would carry the most load when both are released, yet that isn't the case. The one that results in the highest load carried by the hanger is when just one equipment node is released (I released all DOF's in all cases). This hanger is located midway between the two pieces of equipment. I guess I'm wondering if any one has any rules of thumb or guidelines when releasing nodes - like how far away from the equipment before it becomes of no value. Or what advantage, if any, there is when the equipment itself is on springs.

The rule of thumb is 5-6 pipe diameters. If your hanger is more than this distance from the nozzle, you shouldn't release it.

Thanks Richard!