Hello dear colleagues,

I have to analyze some pumps on Silent Blocks.
In the past I´ve been modeling it in a simple way as I found in an old guide. A rigid without weight representing the geometry of the pumps to connect suction and discharge, an anchor point in the suction line, closer to the flange as much as possible. I have been doing it this way in some projects and it has worked without a problem so far.
But today someone told me to model the pumps as a rigid but including the weight mass and include the supports of the silent blocks considering also their stiffness.

Any suggestions or ideas?? thanks a lot...

What CAESAR will do is assume you've installed your system perfectly in a zero gravity environment, and then turn gravity on, compressing said blocks, causing everything to deflect.

This is unrealistic - typical work practice is to install the pump and bolt up to it.

I suppose to some degree, the weight of the piping could compress the blocks further, and this would be synonymous with settlement.

I'm not going to say he's wrong, but I've not heard of this practice before, and the net effect is that your calculated nozzle loads will vary as a result.

Where uncertainty exists, models are built to be conservative. Uncertainty is everywhere.
Pipe strain is a major concern in reliable pump operation. A conservative model for equipment, then, would be to assume the pump is more rigid. Higher stiffness gives higher load calculations (F=KX). And that is what you have with your pump modeled as rigid components.
I guess this is where conservative modeling for design collides with the real world of pump installation and alignment. The engineer responsible for that pump will work with the "real" system to get things up and running and here's where those more-resilient blocks may come into play. Load distribution will change if you would model those blocks but I wonder if the rest of the model has sufficient fidelity to the "real world" to matter in this case. I don't hear of much CAESAR II modeling by those engineers who are working with those pumps.
By tweaking the model, CAESAR II can help you identify trends that can be used to manipulate the outcome.
So go ahead and humor that "someone" and run your model again with flexible (and preloaded) "springs" under your pump and see what changes. It may or may not be significant in this situation.