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1. Cautions

As kind of precision components, antifriction bearing needs to be applied with great care. Being high quality bearings, these bearings will not get the expected effect without proper application.

Cautions of using bearings are as followed:

1. Keep the bearing and its surrounding environment clean.
The tiny dust particles that are invisible to naked eyes will have many adverse affects on bearings. Keep them clean and avoiding any dust into bearings.

2. Use bearings with great care
During the use of bearings, strong impact will produce scars or impress, causing accident.

3. Use bearing special tool
Have to use special tools for bearings, no alternative taking.
4. Avoid bearing rust
During the bearing operation, sweat hands will cause rust. Operate bearings with clean and dry hands; try to use gloves and be careful of aggressive gas.

2. Installation

The correct installation of bearings has direct influence on precision, life span and performance of bearings. Design and assembly department have to be studied carefully before bearing installations and operation. Standard operating procedure is as follows:

· Clean bearing and relevant parts and components
· Check the precision and size of those relevant parts and components.
· Installation
· Do checking after bearing installation
· Fill lubricant

It is better to open the package until the operation is coming. During grease lubrication, fill lubricant without cleaning bearings. Do not clean bearings during oil lubrication either. However, during oil lubrication, for the bearing for instruments or high speed, it needs to be cleaned with oil for removing rust inhibitor on the bearings. The bearings without rust inhibitor will be placed carefully because they will be rusted easily.

The bearings in the lubricating grease won’t be used directly. The ways of bearing installation will be different according to the various structures, cooperation and conditions of bearings. In the general conditions, they are rotation fixed. The inner ring needs interference fit. Bearing with cylindrical bore needs press machine or hot charging method. For tapered bore bearing, it is better to fasten them on tapered shaft or use adapter sleeve.

During installing on bearing block, clearance fit will be applied. For the interference’s quantity of outer ring, it needs press machine or method of cold, which means installing after cooling. In the occasion of cold installation, using dry ice as coolant, it is better to tale antirust measure because the water in the air will be condensed on the surface of bearing. Installation for bearing with cylindrical bore

Method of pressing-in with press machine
Method of pressing-in with press machine is widely used for inch bearings. As shown in Figure 1, use filling block to bear against inner ring and press it with press machine slowly into the inner ring end for being cling to the shaft shoulder; positively no installing inner ring by using outer ring to bear against filling block because this will cause creasing or crushed on roll away nest. Before installation, grease the fitting surface. In the special condition that needs using a hammer, it is necessary to put filling block on inner ring. This condition will cause damage on bearings easily, which is fit for small interference only. The hammer cannot be used for big interference or big size bearings.

Inseparable bearing such as double row deep groove ball bearing needs to be installed in the condition of interference installation. As shown in Figure 2, press with screw or oil, press the inner ring and outer ring with filling block simultaneously. The outer ring of self-aligning ball bearing will tilt easily. If it is not interference installation, it is better to use filling blocks. For separable bearing such as cylindrical roller bearing, conical roller bearing, you can install outer ring on axle and inner ring on bearing block. Then put the inner and outer rings together with great care avoiding their centers from getting separated. Grudging pressing will cause damage on roll away nest.

Hot charge practice
For large size bearing, it is hard to install because it needs great force. So hot charge practice is widely used for large size bearing. Heat bearing in the oil to make it expanded, and then install it into axle. This method can save working time and avoid undeserved stress.
The heating temperature is decided by the size of bearing and the magnitude of interference. Take reference from Figure 3.

Cautions of hot charge are as followed:
· The hot temperature must be under 120℃.
· In order to avoid bearing touching the bottom of oil groove, it is best to put bearing on the metal frame or hoist it.
· During the installation, the temperature reduction will make it hard to install. In order to avoid this, the heat temperature should be 20℃—30℃ above the temperature needed.
· After installation, bearing will be cold and the width will shrink. It is necessary to fasten bearing with spindle nut or other proper method for precluding gap between inner ring and bearing block shoulder.

3. Operation inspection

After installation, in order to check the correctness of installation, there will be an operation inspection. For small size machine, just rotate it with hands to make sure the rotation is smooth. Here listed some normal situations. Do not rotate smoothly because of foreign matters, scars and dents; moment of a force isn’t stable because of poor installation or bad processing of installation seat; moment of a force is too big because of small backlash, installation error and seal friction. Power operation can be applied if there is no problem. For large size machine, cut off power after starting it in an unloaded state, let the machine racing and see if there is vibration or noise and if there is any touch between turning units. Power operation can be applied if there is no problem.

Power operation starts from no-load with low speed. Then it will improve slowly to rated rotating. Inspections in run test are as followed: if there is any unusual sound; the change of bearing temperature; leakage or discoloration of lubricant. If any abnormalities are noticed, operation must be stopped immediately. Check the machine; remove the bearing if needed. Normally, the bearing temperature can be speculated from the outer temperature. The temperature of bearing outing ring measured directly through oil hole will be more accurate. After running, the machine bearing temperature rise gradually. Normally, after 1-2 hours, temperature will be stable. With poor installation, the temperature will increase sharply. The bearing will have an abnormal high temperature. The reasons will be too much lubricant, too small bearing backlash, poor installation and too much friction of sealing arrangement. For the high speed running situation, the inaccurate choice of bearing structure and method of lubrication should be the reason.

Use the echoscope to check the bearing turn sound. It is abnormal if there is strong metal noise, unusual sound, and irregular sound and so on. The reasons will be poor lubrication, bad precision of axel or bearing shaft block, bearing damage and foreign intrusion. The reasons and solutions are as followed: Form 1.

Form 1

PS:

For medium, large cylindrical roller bearing, low noise motor ball bearing, during grease lubricant, especially in winter and low temperature situation, there is problem about NianGa sound. Generally, the NianGa sound happens, the temperature won’t rise, and won’t impact the fatigue life, grease life.

4. Demolition

During the preventive maintenance and replacement, bearing needs to be removed. After demolition, if it needs reusing, inspection, or research, it is best to demolish it with great care. Be careful not to damage bearing and relevant parts, especially the interference fitted bearing which has difficulty operation. In the design process, easy being demolished should be prior considered. Designing and producing demolition tools is very important. During demolition, in order to get a perfect demolition working, the worker should research hardly demolition method, demolition sequence and matching requirements of bearings.

(1) Demolition of outer ring

Demolition of interference fit outer ring, as shown in Figure 10. Before operation, set several screwed holes around bearing block which are used as bolts for installing and demolition. In ordinary time, cover blind plugs on these screwed holes. As shown in Figure 11, separable bearings such as tapered roller bearing, set several kerfs around bearing block shoulder; use filling block; demolish bearing with press machine or demolish with slight tapping.

(2) demolition of bearing with cylindrical bore

It is easy to demolish inner ring with press machine. Be careful to make sure to let the inner rings succeed to the tension. (Figure 12)

What’s more, puller issued usually, as shown in Figure 13, 14. Whatever which kind of tools to be used, the jaw must be stuck on the inner ring end. In order to use the puller conveniently, it is best to take shoulder size into consideration, or process groove in the shoulder, Figure 14.

Demolition of big size bearing adopts hydraulic method. Through the oil hole in the bearing, push high pressure oil to fitting surface. For bearing with big width, puller can be used for demolition operation simultaneously.

Inner ring demolition for NU and NJ cylinder roller bearing can take induction heating method. This method can do local heating in a short time which make inner ring expanded (15). When there are several kind of bearings being installed, induction bearing method will be taken.

5. Examination and reparation for bearing

(1). Cleaning for bearing:

During the examination and reparation for demolished bearings, first record the bearing appearance to check the residual stock of lubricant; then take samples, clean bearing. Normally, cleaner would be petrol and kerosene. The cleaning for bearing would be roughly cleaning and precision cleaning. Put metal net in container on order to avoid touching dirt in the container directly. Roughly cleaning, the bearing will damage the rolling surface if bearing rotating with dirt. Remove lubricating grease and sundries with brush. After basic cleaning, then turn into precision cleaning. Precision cleaning, clean bearing carefully while make it rotating in the cleaning oil. What’s more, the cleaning oil should be changed frequently for making sure cleaning.

To estimate whether the demolished bearing can be used again, careful examination should be taken. The status of racy way, rolling surface and fitting surface; wear pattern of retainer; whether the bearing clearance increase; whether there is any damage or exception which would make the size accuracy down. For those small non-separable ball bearings, hold the inner ring with one hand; rotate the outer ring to check whether the process is smooth. For those TRB separable bearings, check respectively for rolling element and outer ring race way.

Big bearings, which can make it rotated with hands, examine the appearance of rolling element, race way, retainer and file side face. The more the importance the bearing has, the more careful examination should be made. To estimate whether the bearing can be used again, those relevant factors such as damage degree, mechanical behavior, importance, operation condition, examination period should be taken into consideration. Bearings having the following defects cannot be used again:

· chips or crazing on inner ring or outer ring or rolling element or retainer
· cracks on rolling element or collar
· obvious scratches on rolling element or flange or rolling element
· obvious damage on retainer; obvious looseness on rivet;
· rust or scars on race way or rolling element;
· serious creasing or bruising on race way or rolling element;
· obvious creep on inner circle diameter face or outer circle diameter face;
· discoloration because of overheating;
· for bearings in lubricating grease, serious damage on seal ring or shield;

6. Maintenance and examination

(1) maintain, examination and fault treatment

To keep the rolling bearing original performance and use it in good condition for a long period, maintain and examination should be applied periodically to avoid stoppage, make sure perfect turnover and improve efficiency and benefit.

Make maintain periodically according to machine operation condition and performance standard. Monitor operation condition; added or replace lubricant; remove and check regularly.

Notices for maintenance are as followed: condition of turn sound, vibration, temperature and lubricant.

During operation, any abnormal situation happens; take reference from Form2; find reasons; take measures.

Items about after demolition, take reference from examination and reparation for bearing above.

(2) damage and countermeasures of bearings

Generally speaking, using bearing correctly, the bearing can achieve fatigue life. However if some early damage happens, the bearing can’t be used again. Unlike the fatigue life, this kind of damage is called fault or accident. The reasons would mostly be inconsiderateness of installation, using and lubrication; foreign intrusion; under research about bearing and bearing block.

Damage condition of bearing such as craze of roller bearing rings flange, the reasons would be lubricant starvation, improper brand, defect of structure for oil extraction, foreign intrusion, error of bearing installation or too big bend, or caused by all the reasons above.

Therefore, it is hard to find out the real reason only according to research about bearing damage. However, the same accident can be prevented with enough knowledge about machines, process conditions, outer structure; clear knowledge about conditions of before and after accident; good analysis of damage conditions and relevant reasons. Damage reasons and countermeasures are as followed Form 2