Dear Friends,

I want clarify the Pump nozzle connection with piping.

I am doing a Piping stress analysis of Centrifugal Pump for one Contractor.
The problem is due to lack of flexibilty in pipe routing, the nozzle loads on pump is very high and it not even satisfies the API-610, Appendix - F criteria.

I considerd the pump nozzle connection to be rigid (Anchor), since the design temperature of the line is only 180 deg farenheit. So, to reduce the nozzle load, our Contractor insisting me to remove the anchor and replace it with displacement such as follows,

DX=0, DY=0, DZ=0 and Rx, Ry & RZ are left blank. Due to this the nozzle load reduced lower than allowable loads.

But from my point of view its wrong, if we leave blank the Rx, Ry & RZ, it means it is free to rotate. But in actual practice is not correct, since in our case the pump exp can only take place only in one direction with negligible value. But our Contractor insisting me to submit the report as he preferred above and he also says that with the same condition he already prepared a stress report.

But still, i am not satisfied with his point. I need the clarification from the Coade friends as early as possible.

You are correct, leaving the rotations blank means they are "free". This is incorrect for a nozzle. Nozzles provide restraint in all six degrees of freedom. While the restraint may not be rigid, it certainly isn't "free".

From the information you provided, your pump is going to be overloaded.

Thank you very much Mr. Richard Ay for your quick and excellant response.

Again, this just goes to show that just about any system can be "coded" to show that it passes or that it fails. Becoming a stress engineer is about understanding which is most realistic.

Definite credit to you, Paldex, for being suspicious of the contractor's "solution."