×
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

motor vibration non-repeatability

motor vibration non-repeatability

motor vibration non-repeatability

(OP)
Has anyone experienced non-repeatable motor vibration, with the motor running solo? One sympton is that vibration is much higher initially if it sits for a while. Motor is an 1800 rpm induction motor with presurized lube hydrodynamic bearings.

RE: motor vibration non-repeatability

Hi
Actually, I don't have any experience about this subject. But I like to tell you my opinion. According to the symptom,
I don't expect an electrical problem. I think the lubrication system and bearings must be checked first.
Regards.

Azmi Demirel
azzmi@elk.itu.edu.tr
Welcome
I am handsome but married :-)

RE: motor vibration non-repeatability

you do not give much background but some things to consider:

1.cold and/or hot balance of the driven equipment is bad but the balance correction has been done on the motor such that it is "unbalanced" when not coupled. (if this is the case then why worry about uncoupled vibration.)
2.make sure there is no soft foot conditions anywhere along the train.
3. make sure the motor is dowelled to the foundation! (motor hold down bolts are NOT designed to over come sliding forces on the feet; that's what dowells are for)
(note problem areas 1 & 2 can cause changes in vibration levels as a function of changes at the installation such as cold and hot ambients).
4.oil viscosity in sleeve bearing type motors can greatly influence COLD vibration, coupled or uncoupled. check with your friendly oil supplier on the temperature range of the oil you are using. many outdoor motors are supplied with oil sump heaters for this reason.

RE: motor vibration non-repeatability

Hi,
Motorman, you are right all about an unbalanced system. Maybe I'm wrong but if there is a balance problem, I think the vibration must be repeatable.
Regards,

Azmi Demirel
azzmi@elk.itu.edu.tr
Welcome
I am handsome but married :-)

RE: motor vibration non-repeatability

It should be repeatable unless thermal forces are changing things. The above is not much to go on; we do not even know what the dominating frequency of the vibration is. I suspect the problem is due to oil film instability.

RE: motor vibration non-repeatability

woops- I meant to direct for additional interest to "motor vibration non-repeatability" under Mechanical Engineers/Mechanical Acoustics/Vibration Engineering

RE: motor vibration non-repeatability

(OP)
Latest data showed that non-repeatability was worse with higher amplitudes with cold oil, compared to normal DTE light turbine oil at 115 degree F. design temperature. Motor base vibration was over ½ amplitude at bearings in horizontal direction. As rotor vibration was much worse near the coupling end bearing, with a non-symmetrical orbit, bearing was taken apart and re-assembled. As impact tests on casing during coastdown at slow roll speed showed frequency near 1950 cpm, giving only about 10% margin, motor supports were also stiffened in the horizontal direction - insuring that the rotor/bearing first critical speed remained above operating speed. After re-installing bearing, and checking for soft foot after welding support braces, motor then ran with much lower vibration levels.

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! Already a Member? Login


Resources

White Paper - PLM and ERP: Their Respective Roles in Modern Manufacturing
Leading manufacturers are aligning their people, processes, and tools from initial product ideation through to field service. They do so by providing access to product and enterprise data in the context of each person’s domain expertise. However, it can be complicated and costly to unite engineering with the factory and supply chain. Download Now
White Paper - Medical Device Design Control
Medical device product development is a highly integrated and regulated process. Implementation of a requirements tracking solution requires attention to a variety of nuanced topics. When presented with the task of tracking the many concept relationships in a project of this type, the initial software solution of choice tends to be a two-dimensional text systems. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close