RE: [PipingDesign] ->Nozzle loads on Rotating Equipments

From: <Pankaj>
Date: Sat Jul 02 2005 - 05:03:00 EDT


Your statement "There are concerns that the vibration levels of the machine can be increased with high piping loads"- is not fully correct. Piping loads on rotating equipment are mostly static in nature. Piping, in itself, do not vibrate. In some cases like pump cavitation, slug flow or other flow related issues causes vibration in piping. In extreme cases, due to poor design, eigen frequency of piping comes in proximity to the natural frequency of the rotating equipment (with foundation) and this causes vibration in the system.

Now, regarding piping load on rotating equipment nozzles, the real concern is casing distortion. Since these are precision equipment, gap between casing and impellers are small and a small local distortion in casing could result in performance failure. Also, overall stability of the equipment needs to be considered.

I agree that in some cases codes, specially API610, gives nozzle allowables that are hard to justify. Like pump allowable for a discharge pressure of 150psi is same as 1500psi. A higher pressure (discharge) pump should have a stronger casing and hence should be able to sustain higher load. But code has no such provision.

That's it in a nut shell. You are right. Lots of literature is already available and one should go through it for further details.

Best regards,
Pankaj Mandal. wrote:

Dear group members,

A lot has been said &discussed (& also huge amount of literature available ) about the piping loads on the nozzles of the rotary equipment.There are concerns that the vibration levels of the machine can be increased with high piping loads.We have come across many machine vibration problems which were supposed to be caused by piping loads on the nozzles but finally the problems were found to be else where.

   I would like to know from the team members about your "actual experience "on the effect of piping loads on the vibration of the rotary equipment.

Rajesh V Balapure

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[Non-text portions of this message have been removed] Received on Sat Jul 02 05:03:00 2005

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