Maintenance

At the first sign of oil discoloration or contamination, replace with new oil. Rapid discoloration is caused by bearing wear, often from vibration or thrust. Change oil as required to keep clean.

When assembling the bearing, it is possible to foul the rings so that they will not turn freely. Check ring operation by rotating shaft by hand after assembly

Oil Seals

The 680, and 800 frames use fixed labyrinth oil seals. The oil seals should be centered radially on the shaft and set so that the radial clearance is uniform on all sides.

The 500, 580 and 1120 frames use self-centering oil seals that can accommodate small radial movements in the shaft. These floating labyrinth seals should be free to move radially in the bearing housing. A jammed seal could lead to bearing overheating and poor vibration due to excessive seal rubbing during operation.

The primary purposes of the oil seal are:

1.To prevent the entrance of dirt into the bearing cavity.

2.To retain the oil in the bearing cavity.

3.To provide pressure regulation in the bearing cavity.

To achieve these purposes it is necessary that a specific diametrical clearance of oil seal to shaft be held. The cooling fans of the motor tend to create suction or pressure in the bearing cavity, which, if large enough, will push or draw oil mist out along the shaft. The 500, 580 and 1120 designs are equipped with a close fitting air seal that serves as a barrier against excessive pressure or suction inside the bearing.

 

Standard oil seal clearances

Frame

 

Diametrical Clearance

500

 

0.009 to 0.014 inches

580

 

0.015 to 0.019 inches

680

 

0.015 to 0.019 inches

800

 

0.015 to 0.020 inches

1120

 

0.004 to 0.008 inches

The bearing cavities and oil seals on the 680 and 800 frame designs are vented to the outside air in order to keep the bearing cavity pressure as close to atmospheric as possible. For these designs, it is

important that the piping and venting for these oil seals be kept clean.

NOTE

When a sleeve bearing becomes worn and requires replacement, the labyrinth oil seal should also be replaced.

Bearing Clearance Too Large

The clearance between the journal and the bearing will permit the journal center to be slightly below the bearing center. With the motor operating, the presence of the oil film between the journal and the bearing will cause the shaft to rise slightly.

Too large a bearing clearance or clogged oil return holes in the bearing will permit excessive oil to seep out the ends of the bearing. This seepage, combined with the rotation of the shaft, will create an oil mist inside the bearing cavity that will tend to leak through the oil seals. Excessive pressure in a force feed lubrication system can also cause an oil mist to build up.

Cavity Pressures

Motors are sensitive to the amount of pressure or vacuum existing in the bearing cavity. The table below shows the maximum allowable oil cavity pressure or vacuum in terms of plus or minus inches of water:

Frame

Drive End

Non-drive

End

 

 

500

±0.12

±0.12

580

±0.12

±0.12

680

±0.12

±0.12

800

±0.12

±0.12

1120

±0.12

±0.12

For the correction of a high or low reading it is important that:

1.The parts and joints around the bearing cavity and oil seals are sealed.

2.Condensation drains, piping, sight gauges and breathers are functioning properly.

3.Auxiliary equipment extending into close

proximity of the motor bearing housings is shielded from the oil seals to prevent a transfer of air from inside to outside the motor. (ex. motor coupling)

4.All fixed oil seals are centered properly on the shaft.

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