Rajesh,
Most of machine vibrations I have encountered are not due to piping. Big machines like turbine, big pumps etc are too massive and piping loads in itself are really trivial, considering the inertia of the machine (with foundation). Of couse exception are bad piping design, but again, these are really exceptions.
I appreciate your concern regarding equipment vibration. I always believe that the root cause for these vibration is not stand-alone piping design but the system in itself. Hence reducing static load in equipment nozzle may not be the correct solution.
Pankaj.
<a href="/group/PipingDesign/post?postID=EgsyRvDVyBmm9YJnNbsjBOR-wYQuwJ3Jk247Ml6YjR3Mr35esQcu1FoRwCZmwZdicofdn0OCo_LUim-oRjmTYA">Rajesh.Balapure@ril.com</a> wrote:
Dear Pankaj,
Thanks for your reply,
There are lot of theories ,hypotheses,conjectures,hunches,feelings on how
the piping loads affect the rotary equipment performance for which keeping
the vibration levels within limits is an absolute requirement.We do not
want to have a theoretical discussion on this issue but we are looking
for any real experience on the effect of piping loads on machine
performance(i.e.Vibration levels of the machine ).
If you are having such inputs please let us know.
P.S.
"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".---->Your statement in a way justifies the concern
of vibration levels increasing with machine loads.
Regards,
Rajesh V Balapure
Pankaj Mandal
<man45039@yahoo.c To:
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Sent by: Subject: RE: [PipingDesign]
->Nozzle loads on Rotating Equipments
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07/02/2005 02:33
PM
Please respond to
PipingDesign
Rajesh,
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.
<a href="/group/PipingDesign/post?postID=EgsyRvDVyBmm9YJnNbsjBOR-wYQuwJ3Jk247Ml6YjR3Mr35esQcu1FoRwCZmwZdicofdn0OCo_LUim-oRjmTYA">Rajesh.Balapure@ril.com</a> 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.
Regards,
Rajesh V Balapure
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[Non-text portions of this message have been removed] Received on Mon Jul 04 04:41:00 2005
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