Siemens Medallion 1200 Instruction Manual download pdf (Page 21)

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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

580 frame motors use fixed, labyrinth oil seals to

close off the bearing cavity. The 500, 880, SH400,

SH450, and SH560 frame motors utilize floating type

oil seals to close off the bearing cavity. The primary

purposes of the oil seal are:

1. To prevent the entrance of dirt in to 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 a

suction or a pressure in the bearing cavity, which, if

large enough, will push or draw oil out along the

shaft. The close fitting oil seal gives a pressure drop

across it and minimizes the differential pressure.

Standard oil seal clearances

Frame

Diametrical Clearance

500

0.008 to 0.015 inches

580

0.014 to 0.020 inches

880

0.003 to 0.008 inches

SH400

0.003 to 0.008 inches

SH450

0.003 to 0.008 inches

SH560

0.003 to 0.008 inches

Besides using close clearances to correct differential

pressures, some oil seals are vented to the

atmosphere. It is important that the piping and

venting for these oil seals be kept clean.

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.

NOTE

When a sleeve bearing becomes worn and requires

replacement, the labyrinth oil seal should also be

replaced.

Bearing Clearance Too Large

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 which 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

+3.00, -0.12

580

±0.12

+3.00, -0.12

880

±0.12

±0.50

SH400

±0.12

±0.50

SH450

±0.12

±0.50

SH560

±0.12

±0.50

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 the motor

must be sealed to prevent a transfer of air from

inside to outside the motor.

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Siemens Medallion 1200 Instruction Manual Page 21

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