vibration severity check for rotating machines...

in dynamic balancing of rotating machines, we have a vibration severity chart (courtesy of balmac) where we could refer for our judgement. now, is this chart we are currently using is applicable to be a reference for the completely assembled operational rotating machines? that is, the machine were mounted on different foundations and bases(i think it would not applicable to use the chart).
anyone could give the "standard tables for admissible vibration for different rotating machines" with corresponding capacity rating whether dc/ac motors, ac/dc generator on different bases and foundation
s.
thank you very much..
ill appreciate much your comments and suggestions..

 

[dgallagher]

Here is a useful spec to start with: ISO 10816

Regards,
Dave G.

http://www.reliabilitydirect.com

 

[powerjunx]

dave..
how aboutISO 2372(E) and IEEE standard 1068? cuold you further elaborate the importance with this standard?

thanks..
fbjavier

 

[electricpete]

IEEE1068 has some specific balance requirements intended for motors requiring high reliability for petrochem industry. It allows only 0.08 ips while mounted either rigidly or resiliently for 1200,1800,3600rpm machines. (lower limit for lower speed machines). These are bearing housing measurements by accelerometer (not shaft rider or prox probe).

In contrast NEMA MG-1 allows 0.15ips while resiliently mounted and 0.12 while rigidly mounted. (By the way I strongly recommend you specifiy rigid mounted test espcially for 2-pole machines). Once again we're talking bearing housing.

And all of the above limits are applied to a new machine during purchase. In fact during any purchase or repair the customer is welcome to specify whatever they feel is appropriate for either a blanace spec or a vib spec (providing the machine will be run at the factory).

As far as machinery in the field... have you heard of the Rathbone chart. There are endless variations published by every manufacturer of vib monitoring equipment. Sorry I don't have a link.

I think that in general most limits will be expressed as a velocity limit which does not depend upon the machine size. Something like precision is <0.1ips for 20hp or 2000hp motor. Good is <0.2 ips. Rough is >0.3 ips. This excludes reciprocating machines and of course every machine has it's own personality.

A good vibration program will not look at magnitude but will examine the spectral content for signs of specific problems and trends. For example on critical equipment you had better jump on a bearing before it gets you to the rough range. It likely won't influence overall readings at all in it's early stages but is easily detected by it's distinctive patterns.