Speed necessary for move ring in a Sleeve Bearings

[petronila]

Dear all

We was made maintenance in a horizontal 7500 KW generator mounted in sleeve bearings, once the job was finished we move the machine with the help of two belts and DC motor, the motor´s power was not enought to speed the generator up to 750 rpm only to 100 RPM, but we note a little smoke getting out from the D.E oil chamber and the rings don´t move, we think this was caussed due to the speed was not enought to create the proper OIL condition to push the rings.

The rotor weight is 15000 Kg.

Thanks for the Inputs

Carlos

 

[waross]

The rings should move freely at any speed even less than 1 RPM. They are probably jammed mechanically.

Bill
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"Why not the best?"
Jimmy Carter

 

[fredt]

Sleeve bearings require the shaft to be rotating at a certain minimum speed in order to create a hydrodynamic oil film. If rotational speed is too low there will be metal to metal contact. Having said that - 100RPM should be enough to create that film in most cases.

Fredt

 

[waross]

The rings carry the oil up to the shaft. The oil doesn't move the rings (or I have also seen small chains).
We usud to have to start a set of four motor generator sets every night.
Each set had three horizontal single bearing 1300 HP generators and two 1050 HP generators. We would install the seven foot long coupling wrench and out foreman at about 240 lbs. would hang his whole weight from the end of the wrench. I was next at about 220 lbs. When I jumped up and hung beside the foreman, the set would start to rotate slowly. About two rotations would be enough for the oil to start working into the bearings and rotating the set then became progressively easier. Somewhere between 50 and 100 RPM we would have a good oil film establish and energize the motor. Just three more sets to go.
The point is, if the shaft is moving, the oil pickup rings should be moving.

Bill
--------------------
"Why not the best?"
Jimmy Carter