×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Vibration
4

Vibration

Vibration

(OP)
Hi
Can anyone explain me about the Electrical Run out in a rotor shaft in simple terms.

RE: Vibration

Do you mean mechanical runout?

RE: Vibration

2
For larger machines, there are often non-contacting proximity probes used to measure shaft vibration.  These probes use a magnetic field across a gap between the probe tip and the surface of the shaft to measure the distance between the probe and the shaft.  This signal can be used to determine the shaft movement (displacement), velocity or acceleration.  In order for this signal to be accurate, the surface of the shaft has to have very low mechanical and electrical run-out. For our spare rotors, we require that the combined run-out is less than 0.00025".  We measure this with a dial indicator for the mechanical run-out and a proximity probe for the electrical. Electrical run-out would suggest variability in the magnetic and electrical properties of the shaft.  If the shaft material is not homogeneous, it will exhibit electrical run-out that will result in inaccuracy in the signal.  Diamond burnishing the shaft can smooth out irregularities in the surface properties in some cases.  Some materials are more prone to electrical run-out than others.  If burnishing does not improve the run-out, the surface needs to be machined back to expose new material that may be more uniform in electrical properties.  You can search for more information on this topic from the manufacturers of non-contacting proximity probes.  Ours are made by Bently-Nevada which is now part of General Electric.  I believe SKF owns another system that used be built under the name of Dymac.   

Johnny Pellin

RE: Vibration

2
Burnishing uniformly work hardens the surface, which can help.  Some have tried micro-peening for a similar purpose.

Some materials can be come magnetized.  Some machining operations can leave the target material non-uniformly magnetized.  This requires de-Gaussing.

Hit the target with a hammer, remove the physical indentation, and it may leave residual stress (looking near heavy shrinks, too).  The probes can be affected by this, too.

Regards,

Bill

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources