Maintenance

Sleeve Bearings

CAUTION

Maintain proper oil level.

Failure to do so may cause improper lubrication of motor resulting in damage to the equipment.

Follow lubrication instructions carefully. Avoid adding oil while unit is running.

Motors with sleeve bearings are shipped without oil. A rust-inhibiting film is applied at the factory to protect bearing and journal surfaces during shipment. Before attempting to operate any sleeve bearing motor, the following steps must be performed.

1.Visually inspect the bearing condition. Oil ring inspection ports and drain openings in the housing are normally provided for this purpose.

2.Check for any accumulation of moisture. If oxidation is discovered, all traces of it must be removed before motor is put in service, which will require disassembly.

3.Flush all oil piping. Fill bearing reservoirs to normal level. Fill to mark indicated on gauge or to center of gauge. See the table below for recommended grades of oil.

4.Rotate shaft several turns by hand to distribute oil over bearing parts. Make sure oil rings rotate freely.

Recommended Grades of Turbine Oil

Motor Speed

Oil Viscosity at 100°F

ISO

Grade

 

 

 

 

 

3600 or 3000 RPM

140 - 160 SSU

32

1800 & slower

300 - 350 SSU

68

 

 

 

NOTE

The oil viscosity at operating temperature is very important in selecting proper oil and may vary in different climates.

It is important to maintain the correct oil level, as lack of lubrication is often the cause of bearing failure.

Inspect oil level and oil ring operation frequently. Oil ring operation can be observed through the sight glass mounted at the top of the bearing capsule. Oil rings should be perfectly round, free of burrs or rough edges, turn at constant speed and carry a noticeable amount of oil to the top of the journal. Failure of the oil ring to turn freely may be caused by:

1.Ring out of round (should be round to 0.062 inch)

2.Fouling on a projection of the bearing bushing.

3.Ring not balanced (heavy side will tend to remain down).

4.Adhesion to guide slot (trapezoidal section reduces adhesion).

5.Oil too cold or viscous, or oil level too high.

6.Shaft not level – oil ring tends to bind.

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.

Force Feed Lubrication

Oil is metered through an orifice in oil inlet line to allow the proper amount of lubricating oil to enter the bearing. Conventional oil rings are also supplied with the motor to insure temporary bearing lubrication in the event the force feed oil supply should fail. It is important to check oil flow frequently. Lack of lubrication may cause bearing failure.

Checking Sleeve Bearing Clearance

Excessive clearance can cause rapid bearing failure, and decreased air gap between stator and rotor at the bottom of the motor. Diametrical sleeve bearing clearances for the 500 and 580 frame motors are in the range of 1.7 to 2.7 mils per inch of bearing diameter. Diametrical sleeve bearing clearances for the 708, 788, and 880 frames are in the range of 1.0 to 2.0 mils per inch of bearing diameter.

An accurate check of bearing clearance is obtained with micrometer measurements of the shaft journal and bearing bore.

Bearing Replacement

Antifriction Bearings

For typical antifriction bearing configuration, see Figures 3 and 4.

Replacement bearings may be of a different manufacturer but must be equal to the originals used in the motor. When ordering bearings specify as follows:

1.The complete A.F.B.M.A. (Anti-Friction Bearing Manufacturers’ Association) bearing number from the motor nameplate.

2.Identifying numerals and manufacturer stamped on the bearing.

3.Bearing tolerance class, i.e. - A.B.E.C.-1 (Annular Bearing Engineers’ Committee Tolerance Class One).

4.Internal radial clearance, i.e. – A.F.B.M.A.-3 (Clearance Class Three).

5.Electric motor quality.

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