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Bearing installation and removal

Date:May 13,2014

I. Preparations before Installation
Overhauling for Shaft
1. Test eccentricity, bend and diameter variation (ellipse) of journal.
2. Check surface roughness of journal.
3. Test shaft shoulder verticality and fillet radius at the root of shaft shoulder.
4. Test the size of journal with a micrometer or a dial indicator.
Overhauling for Shell Bore
1. Test the ellipse and cylindricity (taper) of shell bore.
2. Test verticality between shell bore and shoulder.
3. Test abrasion loss and axiality of shell bore.
II. Installation Methods of Rolling Bearing
Rolling bearing can be installed mechanically, hydraulically and heatedly. For small-sized (<80mm) bearing with cylindrical bore, when the fit is not too tight, it can be installed only by gentle beating with a hammer; it had better to use a soft steel sleeve with spherical surface in installation; if the fit is tight, it is necessary to use a sleeve on the ring (internal or external) of bearing, but never directly beating the bearing ring with a hammer. The hydraulic installation method is good for reduction of installation or dismounting force, and is suitable for small or large-sized bearing with tapered hole; heating installation method is suitable for tight fit bearing with cylindrical bore, or occasion when the mechanical method is unfeasible.
During installation, pressure should be directly applied on the ring end face in tight fit, but not transmitted by the rolling body, or that will cause pressing marks on the work surface of bearing and impacts on the normal work, or damage the bearing. As the cage, sealing ring, dust cap and some parts of bearing are easy to deform, the pressure can not be applied on these parts in installation or dismounting, should be uniformly applied on the perimeter of ring end face to press the ring in, it is forbidden beating the bearing end face with a hammer or other tools, or causing damages. In the event of smaller interference, it is available to press the ring end face with the sleeve at ambient temperature and beat to press the ring in with a hammer. In mass installation, it is allowable to use a hydraulic machine, but making sure the outer ring end face and shoulder end face of shell are tightly pressed without clearance.
III. Running Checkup and Maintenance after Installation of Rolling Bearing
Running Checkup after Installation
Whether the bearing is installed correctly or not is directly related to its lifespan and the precision of main machine. If the installation is improper, the bearing will vibrate, have large noise, low precision and quick temperature rise, but also has the risk of getting dead and burnt-out; conversely, the correct installation can ensure precision and greatly prolong the lifespan. Therefore, it is necessary to test it after installation.
Key test items as following:
1. Check installation position;
2. Test radial play;
3. Test the tight fit of bearing with shaft shoulder.
Bearing Maintenance
It is our ultimate goal to let bearing operate safely, however, that can not be ensured only by quality of bearing, there are some factors affecting the lifespan of bearing, mainly including environment, appropriate lubrication and maintenance plan and monitoring to the bearing conditions.
At operating environment, it has to keep the correct alignment work of bearing and avoid extremely high temperature, moisture and pollution so that the equipment can show the optimal work state. It is the key to have appropriate lubrication and maintenance and monitoring to conditions of bearing for keeping the maximum lifespan of bearing.
1. Monitoring
You have to test and monitor the service behavior of bearing regularly at fixed point for running machine commonly by means of listening, touching and smelling one fixed point at the bearing box. Once there is noise, peculiar smell or abnormal temperature rise, it is obliged to shut down and check it.
2. Lubrication
In daily maintenance, it is essential to replace or supplement lubricant for bearing regularly. Mostly, the damage of bearing is caused by incorrect lubrication mode or inadequate lubrication, therefore, it is very important to replace and supplement lubricant at regular intervals. According to statistics, it is common to use lubricating grease in above 90% bearing lubrication. So it is crucial to supply reliable and suitable lubricating grease.

 ⅣThe Disassembly of Antifriction Bearing

The disassembly of bearings should be carried out as carefully as the installation. During disassembly, it should prevent damaging axles or bearing seats. It should re-install or re-process bearings after disassembly in a careful way. For these parts should be preserved for losing effectiveness analysis, it should notice that never damage the bearings and parts. Through long-term running bearings, it is extremely difficult to disassemble from the main machine, especially the interference fit bearings, with different operation. Therefore, it should take easy disassembly in the first consideration during the design. It is very important to design those tools easy to disassemble according to demands. During the disassembly, to learn how to disassemble, the order and matching requirements according to the diagram can keep the precise disassembly.

During the disassembly, it should use the suitable puller to pull out the bearing, not knock on the bearing with a chisel or a mallet. If it is needed to use the disassembled bearing again, it should select the suitable disassembly tools. When disassemble the interference fit ferrule, it should add the tension force on the ferrule. It is not allowed to deliver the disassembly force through the rolling element. Otherwise, both the rolling elements and the rolling aisle will be crushed.

Normal disassembly bearing method:

Mechanical method

Mechanical method is a traditional way to disassemble the matching bearing, with the most application.

Heating method

Heating method is suitable for short cylinder rolling bearings.

Hydraulic method

 

Hydraulic method is suitable for inner bore bearings with tapers or suitable fit pieces. It requires presetting the oil hole and the oil groove.

The normal disassembly sequence: Firstly, try to use interference fittings to add out-tension force to the ferrule (normally inner ferrule). If it cannot touch the inner ferrule, pull the outer ferrule. Centering the puller and stamping axles (if it is not centered firstly), pull out the bearing through rotating the puller with implementing acting force.
Safety Problems during the Disassembly
1. Striking Bearing

It is possible to damage the smash of bearing tramp steel pieces. The internal bearing may adopt fragility pieces and the debris of steel pieces may cause series damage.

2.Gas Cutting Bearing
If cutting the bearing with gas, it may cause grease fire or explosion. The gas generated from burning sealing elements can damage the lung while the melting sealing elements may burn the skin. For these reasons, please wear PVC gloves to do the treatment. It is not suggested to gas cut the bearing.
3.Fluorinated bearing
Viton can generate hydrofluoric acid above high temperature (about 300℃) that are extremely harmful for human and the smelting materials can burn out the clothes and skin.
4.The Lowest-level Protection Device in the Non-recommended Method
When the non-recommended method is employed, it should ensure to wear the following protection devices: safe musk, safe glasses, full protective clothing and gloves.
5.Sealing Cautions
Disassemble all sealing ferrule before gas cutting

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