importance of vibration measurement?

[nyvens]

hi!
I would like to understand the practical usefulness of vibration measurement. Whether it can be used apart monitoring machine health?
i am considering of using it as a measuring output, for different inputs of shaft surface texture in a shaft- bearing assembly.

i would like to know your opinions and whether it is a good idea.

 

[Tmoose]

shaft-bearing assembly?
hydrodynamic bearing? I don't think much "texture" (surface finish or less than gross geometry) info would make it thru to the bearing housing, or modify how the shaft rotates.

Ball or roller? The inner race is pretty flexible, but even with an interference fit does a good job averaging shaft finish and to an extent, even geometry.

Still might be worth a few trials with shafts of VERY well known geometry.

 

[TPL]

This sounds like an application for a proximity probe (used to measure shaft relative displacement on turbomachinery fitted with fluid film bearings)

Prox probes deliver a voltage that is proportional to the gap between the probe tip and the shaft surface. Typical scale factors are 200mV/mil but other scale factors are available - for machine vibration measuring purposes, the surface area that runs beneath the probe has to be as good as possible in terms of smoothness and material consistency (i.e. no plating < 0.020 inches).

For a surface finish measurement/assessment you would need to turn the shaft slowly (say <<100rpm) - a lathe would be ideal

 

[MotorVib]

Coming for the world of motors and Generators (Genset) I belive that it is the best way to understand the generial health of a system is with vibration. Even with a simple hand held that reads mils, G's or ips over time it will tell you more about the brg. shaft, balance and the coulpling then TC's can. Vibration problem is the load, it plays a big part both loarge loads and changing load tend to increase vibration. Also room temp and machine time also have an effect on the vibration. This is why I belive that I have not see a good system out there that can be used for monitoring machine health. I have worked with a few but changing loads causes problems.

Chris

"In this house, we obey the laws of thermodynamics." Homer Simpson

 

[nyvens]

Tmoose,
U mean if i use ball bearing and measure the vibration (lets say at the bearing) for rotating shafts of different surface finish, i can get different vibration signals?

Does anyone know how suface finish on a shaft play an important role in industry and how it can affect vibration?

thank you guys for tour replies.

 

[Tmoose]

Here is a typical spec for normal shaft and housing fits and finishes for ball/roller bearings.

http://www.tec.nsk.com/Handbook.asp...gnOfShaftsAndHousings/AccuracyAndSurface.html

I think bearing housing vibration measurements would contain virtually no info on shaft geometry or finish within the above specs for a ball or roller bearing machine, and even less on a hydrodynamic/static bearing machine.