Sag Mill Syncronis Motor high axial vibration non drive end bearing 2

[Robbie59]

On site we have a Sag Mill Driven by a 5500KW Motor. We have a vibration issue right across the Mill. The highest vibration is 30mm/sec RMS axial on the motor non drive end bearing.(White metal Bearing)
The gear mesh frequency is 4200 CPM. The dominant frequency is 2400 CPM. We can not relate this to anything on the Mill or drive train but with the high energy vibration the number 1 suspect is the 5500 Kw motor but need something to confirm this
The vibration has high energy vibrating platforms etc. Where ever I take velocity measurements the dominant frequency is 2400 CPM . Measurements on the pinion bearings motor bearing , trunion bearings, the concrete foundations etc.
As mentioned the highest measurement is the motor non drive end axially 30mm/sec . This is a synchronis motor 200RPM . 200RPM 30 pole motor 50Htz

We have inspected pinion bearings ,the air clutch, covers removed from motor for a visual check. Nothing found.The pinion and girth gear yes are worn but thermo graphic and visual visaul indicates this is not the issue.

I believe the vibration is coming from the motor possibly at a coil pass frequency which I have read has high energy vibration.
I am in a very isolated ara and hard to get access to specialists.
I am trying to get the name plate information and hoping someone has photographed it in the past
Have a look at the attachment with spectrum and an overall model of the Mill Vibration
Has anyone had a similar experience. Is it possible to have a coil pass pass frequency of 200 x 12 to = 2400CPM .
Very hard to get information about this motor. It is a GE Canada Electric motor . I have attached a data sheet.
I would appreciate any feed back or indications where to look.
Find the 12 x 200 RPM shaft speed we find the issue
All help would be highly appreciated

 

[Robbie59]

I did believe and was convinced that the 2400 cpm frequency was coming from the motor. I also received expert advice it was the motorEven now I cannot relate the air clutch to this 2400 cpm frequency, only the cracking in the drum effected shaft stiffness and contributed to a torsional vibration. This is baffled me,, but all part of learning and want to share the experience.

 

[Skogsgurra]

A very good and illuminating thread, it is. And it makes me feel old, tired and wise. On 5 Nov 14 03:37 I said: "Do not be led astray by indicated frequencies and "math logic"!

What I mean is that many of us feel that we should use, and need to use, all that math that we once learned in school. And, when results and conclusions don't fit the real world, we often assume that our tinking is wrong and then we stop thinking at all.

Most mechanical guys are wrench and sledge and don't care about math. So, we are sitting ducks, easily convinced that everything mechanical is good and Electric is to blame. and therefore need to do a lot of work that is totally unnecessary. That's why I said "Do not be led astray by indicated frequencies and "math logic"!


Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[Robbie59]

Scoggsgurra - I remember your comments during this thread,, and proven to be right.

I did want the clutch changed in the early period of this vibration issue as it was common to both the motor and Sag Mill drive and high vibration was at both ends of the drive train. But informed nothing is wrong with the clutch

Looking then for the mystery 2400 CPM and concentrating on the motor. The motor was fine but did correct the air gap on the exciter

This was along thread and been a learning curve for myself. At the same time I hope all have learnt as well

Again thank you to all contributors

 

[melspuds]

This Thread is a good read for anybody interested in vibration analysis.
Very informing and interesting but also very long thread.
Dave