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Pumps are typically made of metal, as such, they expand at temperature just like the pipe they are connected to. Whether it is an advantage or not, depends on the situation.
That said, you need to be careful in how you model systems around pumps. For example, ANSI pumps are usually supported at the bottom of the case, so you would be inclined to model a rigid element from the centerline down to the base to account for it's expansion. But, we typically modeling piping as though it is supported at it's centerline, even though the support point is at the bottom of the pipe. Take those two together, and you can show a slightly greater expansion of your pump and have it "lift" the closest support, resulting in a overloaded pump nozzle. In such a case, Caesar is going to tell you you have a problem, when you really don't.
On the other hand, I've had 700°F bottoms pumps (API centerline supported) where the nozzle was 10" and the pipe coming at it was 20" with a eccentric reducer. In such a case, ignoring the growth up from the bottom of the pipe (and putting a hard support) could give a non-conservative result for the nozzle load.
There's no one cookie cutter approach. Each pump system has to be examined with a critical engineer's eye to determine how best to model so that the solution you recommend to the client is safe, effective, and reasonable.
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Edward L. Klein
Pipe Stress Engineer
All the world is a Spring