bearing removal and installation

8/8/2019 Bearing Removal and Installation

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Inspection during non-operation

o Start the job by arranging the working area and making it clean.

o Clean the external surfaces.

o Disassemble the equipment parts and note the order.

o Clean and inspect all parts

o Check the lubricant for impurities by rubbing a little between fingers.

The type of impurities may indicates seal or bearing damage.

o Cover the machine, after disassembly, to prevent entry of dirt

o And moisture.

o Cover bearings and seating with waxed paper or plastic sheet if

o work is interrupted.

o Wash the bearing, using paint brush and white spirit.

o Dry with a clean lint-free Cloth or compressed air (taking care

that no bearing components start rotating).

o Inspect the raceways, cage and rolling elements for damage,

scoring, pitting or discoloration.

o If the bearing is undamaged it should be re-lubricated according

to instructions.

o

If the bearing is damaged, replace.


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Bearing removal

o If the bearing is to be removed, it is advisable to mark it to show its relative mounted position, so the bearing

should be reinstalled in the same position.

o Arrange for a suitable stop or support for the shaft to be protected from damage and always treat the bearings

carefully.

Interference fit on the shaft

a. If the bearing has an interference fit on the shaft, use puller or press.(press is preferred)

b. Load should be applied only to the inner race.

The best way of removing a bearing mounted on a cylindrical Shaft seating is to use a press. Make sure thatonly for the bearing rings with the interference fit.


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If a suitable puller or press is not available a soft metal drift with rounded pointmay be used this should be applied to the inner ring face.

Take great care with this method not to damage shaft or bearing.

Interference fit in the housing

If the bearing has an interference fit in the housing, for example in a wheel,it can be dismounted by using a mounting dolly or a length of tubing.

Apply blows evenly distributed around the end face.

The ends of the tube should be flat and free from burrs.

Use a soft metal drift with rounded point if there is an integral shoulder betweenthe bearings.

The inner ring assemblies of self-aligning ball bearings and spherical rollerbearings can generally be swiveled so that a puller can be used.

Bearing installed on sleeve.


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Self-aligning ball bearings and spherical roller bearings are often mounted on adapter or withdrawal sleeves.

The advantages of using a sleeve are that the shaft seating does not need such accurate machining, and mounting anddismounting are made easier.

.

Adapter sleeve removal

1) Mark the position of the sleeve on the shaft.

2) Disengage the bent tab of the locking washer from the lock nut slot.

3) Unscrew the lock nut a few turns.

4) Place a mounting dolly or a length of tubing against the nut and apply sharp, evenly distributed blows untilthe bearing becomes loose.

If the bearing is mounted on a smooth shaft or if there is no spacer sleeve between the bearing and shaft shoulder, the tool should be

applied to the inner ring instead.

Withdrawal sleeve removal.


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1) For small and medium sized bearings, the sleeve may be removed

using a nut similar to that used for adapter sleeves.

2) Remember to lubricate the thread and the lock nut face

2) Tighten the nut using a hook or impact spanner until the bearing

becomes loose.

Inspection of removed bearings.

1. Wash the bearing using paint brush and white spirit, then dry carefullyusing a clean lint-free cloth or compressed air (taking care that no bearingelements start rotating).

2. Inspect bearing raceways, rolling element and cage for any signs ofdamage or discoloration (discoloration may indicates bearing overheat).

3. Spin the outer ring listening for any abnormal sound.

4. For bearings with a shield or seal on one side the total bearing should be cleaned, dried, inspected and handled in thesame way as bearings without seals.

However, never wash a bearings wit seals or shields on both sides. They are sealed and lubricated for life and shouldbe replaced if you suspect bearing or sealing damaged.

5. If the bearing appears damaged, disassemble it and try to determine the reason for the damage.

Diagnosis of bearing faults

Bearing defects can be found out from the loading patterns on the inner race, outer race and the rolling elements.


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Any abnormal operation of bearings will be indicated on the loading pattern.

Not all patterns and marks are signs of bearing damage. Bearings will show loading patterns from normal operation also.

Normal wear pattern for rotating shaft (Fixed housing) with radial load.

The pattern is even on the inner race all the way round, but only on the bottom side on the outer race.

Abnormal pattern for too tight fitted shaft

Rotating shaft (fixed housing) with radial load.

The pattern is all the way round on both races, but the pattern is slightly wider on the bottom of the outer race because of theradial load.

Abnormal pattern for oval compression on the outer race.

Rotating shaft (Fixed housing)

The pattern is even all the way round on inner race. The pattern is only where the pressure is on the outer race.

Abnormal pattern indicating misalignment between shaft & housing.

Rotating shaft/Fixed housing.


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The pattern is even all the way round on inner race, but the pattern on the outer race will change sides from top tobottom.

Normal wear pattern for Correctly aligned thrust bearing.

The pattern is even all the way round on both the top and the bottom race.

Abnormal pattern for races misaligned to each other.

Rotating top race fixed bottom race.

The pattern is even all the way round on the top race, but is wider at load bearing side on the bottom race

Abnormal pattern for races eccentric to each other- Rotating top race /fixed bottom race.


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The patter is even all the way round on the top race, but off to one side on the bottom race.

Inspecting shaft and housing before installing a bearing.

The following steps must be taken for preparing the shaft:

Clean, then check the shaft for any damage or burrs.

Check the size of shaft and bearing, using micrometer to ensure correct fit.

Check shaft run-out, using dial test indicator and V blocks.

Check the shaft shoulder for correct seating.


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The shoulder fillet should not prevent bearing from fully contacting shoulder

Housing inspection

The following steps must be taken for preparing the housing:

Clean the housing and check for any damage or burrs.Check housing for correct size or joviality.

Take three readings in different positions, using inside micrometer.

Install anti-friction bearingsThese are several basic rules for installing cylindrical bore bearings:

Never directly strike the rings, cage or rolling elements while installing.Never apply pressure to one ring in order to install the other.

Cold installation

Bearing rings that rotate should have a tight (interference) fit to prevent creeping and turning.Bearing rings that are stationary may be mounted with a loose (transition) fit.

Make sure the bearing is mounted at right angle to the shaft/housing.

a) Small size bearings can be mounted by using hammer.b) Always use a sleeve to the size of the fitting ring (Inner or outer).


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c) Lubricate the shaft journal before fitting.d) The sleeve should have parallel faces and must be burr free.


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a) The use of a press is particularly suitable when small bearings are frequently mounted.

b) Lubricate the shaft journal. Use a sleeve between the bearing and the press.c) The sleeve end faces should be flat, parallel and burr-free.

A hydraulic press is safer and more efficient to use than a mechanical one.

If an interference fit is required for the inner ring, first mount the bearing on the shaft. Then push the shaft with thebearing into the housing.

The bearing with separable rings can be mounted independently. This is especially useful when there is aninterference fit on both rings.

Hot installation


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The force needed to mount a bearing increase rapidly with bearing size. Larger bearings cannot easily be pressedon to a shaft or into housing because of the high mounting force required. Therefore, the bearing, or one bearing ring, isheated before mounting.

Normal mounting temperature of bearings varies from 80 to 90C

Never heat a bearing to a temperature greater than 125C

Using oil bath

Oil baths ensure even heating. Can maintain a bearing at a certain temperature.

Always keep the oil clean to prevent bearing contamination.

Using induction heater

Quick to heat

Automatic cut out at correct temperature.

Avoids over heating.

Using heat rings

Aluminum heating rings, originally designed for dismounting inner rings of cylindrical roller bearings, are alsoEffective for mounting.


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Never heat a bearing using an open flame

Press fit

1. Check the dimensions of the bush and housing and compare with the manufactures recommendations.

2. Bearing and housing surfaces are clean and free of burrs.

3. Lubricate the bush/housing before pressing.

4. Align the bush square and press, in one continuous motion.

5. Measure the inside diameter of the bush to see if it has closed in as a result of the interference fit.

6. Scrape or ream the bush to recommended size.

Shrink fit: The bush is fitted by heating the housing or by cooling the bearing.

1. Check the dimensions of the bush and housing and compare with the manufactures recommendations.

2. Heat the housing uniformly and slowly to about 110 C.

3. Or cool the bush in a deep freeze unit before assembly.

4. Measure the inside diameter of the bush to see if it has closed in as a result of the interference fit.

5. Scrape or ream the bush to recommended size.

Bearing bush clearance measure1- Measure the shaft journal diameter using outside micrometer.

2- Measure the bearing bush inside diameter using the inside micrometer.3- Find the clearance between shaft and bush and compare to the manufacturer

specifications.

Lubrication: The main function of a lubricant is to form a film between the rolling and sliding surfaces of a bearing, sothat metal-to-metal contact is prevented even under heavy load.

1. Lubricant reduces friction and wear.

2. Guards against corrosion and contamination.


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Forms of lubricant

1- Liquid such as Oil2- Semi solid such as Grease.3- Solid such as Graphite.

Grease lubrication

Grease quantity

Bearing should be filled completely With grease, but free space in the housing Should only be partly filled(between 30 and 50%)

Oil lubrication


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Some important properties of a lubricant

1. ViscosityViscosity is the ease with which a liquid flows.Technically, it is a measure of the internal friction of lubricating oil which arises between different molecular layers when a

liquid is set in motion.

2. Consistency is the degree of stiffness of grease.

3. Film forming ability

a) Rotational speedb) Temperaturec) Viscosity

4. Flash point is the Temperature at which the lubricants vapor will ignite when exposed to flame.

5. Fire point is the temperature at which the lubricant burns steadily (slightly higher than flash point).


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Bearing handling and care

a. Always keep bearings in their protective packages till installation time.

b. Coverequipment with plastic, waxed paper or a clean dry lint-free cloth to protect exposed components andun-mounted bearings.

c. Neverinstall a bearing close to Chip-forming or dust producing machinery.

d. Neverapply direct blows to a bearing.

e. Use a length of tubing with a press When mounting


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f. Lubricate with the right amount of the right clean lubricant at the right time.

bearing removal and installation

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