Factors Affecting The Service Life of Slewing Bearing

1. The slewing bearing has a good service life only if its structure is designed reasonably.

2. Slewing bearing is processed by forging, heat treatment, turning, grinding and assembly. The rationality, quality and stability of each processing technology will also affect the service life of the rotary table bearing.

3. The material will also affect the rotary table bearing, but at present, the slewing bearing material has been greatly improved, and the impact on the slewing bearing is also slowly reduced.

4. The bearing capacity of the slewing bearing will also affect its service life. The slewing bearing has different bearing capacity due to different manufacturing processes and materials. If it exceeds this range during operation, it will cause damage to the rotary table bearing, which will affect the service life of the machine.

5. Friction is a key factor for all machines, and the wear caused by friction is the main factor leading to the reduction of service time of slewing bearing.

Precautions in use

1. Fill lubricating grease regularly

The slewing bearing should be filled with grease regularly. The filling time is different according to different types of slewing bearing. Ball type: add lubricating grease every 100 hours of operation; b: Roller type: add lubricating grease every 50 hours of operation;

2. Cleaning and inspection

The sundries on the surface of the slewing bearing should be removed frequently during use. After the slewing bearing has been operated for 100 hours since installation, the pre-tightening force of the bolts should be checked. After that, it should be checked every 500 hours, and it must be maintained with sufficient effort. Also check whether the sealing strip of the slewing bearing is aged, cracked, damaged or detached. If one of these conditions occurs, replace the sealing strip in time to prevent debris and grease loss in the raceway. After replacement, apply corresponding grease to avoid jamming or rusting of the roller body and raceway.

3. Troubleshooting in time

Pay close attention to the operation of the slewing ring during use. In case of sudden increase in noise, impact and power, stop the machine immediately for inspection until all faults are eliminated, and disassemble it for inspection if necessary.

4. Do not touch water

During the use of the slewing bearing, it is forbidden to wash the slewing bearing directly with water to prevent water from entering the raceway and causing rust; Strictly prevent hard foreign matters from approaching or entering the meshing area, so as to avoid tooth injury or unnecessary trouble.

How to prolong the service life of slewing bearing

In heavy applications with frequent rotation, the common failure of large diameter bearings is a common case of premature failure. In large rotating equipment such as cranes, excavators and tunnel boring machines, slewing ring bearings must simultaneously deal with complex load spectra, including various combinations of thrust, radial and overturning moment loads.

Fortunately, there is a simple way to protect your investment in these custom-designed bearings. It is called periodic maintenance, which can prevent 96% of slewing bearing failures. In order to maximize the bearing life, only the following four techniques should be followed: raceway and gear lubrication, bolt torque inspection and seal inspection, and four warning signals for potential bearing problems should be alert.

Bearing lubrication

Bearings shall be lubricated regularly with heavy extreme pressure grease. Shoot the accessories around the bearing circumference freely according to the interval recommended in the operation manual.

Slow rotating equipment or oscillating applications (such as backhoes, excavators, cranes) should be relubricated approximately every 100 hours of operation. For fast moving or continuously rotating equipment (such as trenchers and boring machines), more frequent lubrication may be required - once a day or even every eight hours.

When adding grease, rotate the bearing to spread the grease throughout the grease. Pump it in until you see the old grease squeeze through the seal; This is called clearing. The purged grease will carry contaminants out of the bearing. Rub a little between your thumb and forefinger. If you feel gravel or metal debris, there may be a bearing problem.

Grease tends to dry for a long time, thus forming condensation in the bearing. You can avoid this situation by introducing grease at least every six months, even if the equipment is idle.

Gear lubrication

Most large bearings have gear teeth that need lubrication, which are different from the requirements of the bearing itself. Because the meshing action of the teeth often extrudes the lubricant, the gear should be lubricated every eight hours on the equipment with slow rotation or intermittent rotation, and more frequently on the equipment with fast or continuous rotation. A small amount of grease should be introduced at the meshing point between the gear and pinion.

Sealing element

The seals on the bearings should be visually inspected regularly to ensure that they are intact. Many people ignore the importance of seals, but they are very helpful in preventing bearing raceway pollution.

Bolt

Torque check of bolts should be part of any routine maintenance procedure. The frequency of these checks depends on the severity of the service. Vibration and shock often loosen bolts, but regular torque inspection and tightening will help to maintain an appropriate preload level.

The mounting bolts should be tightened to the proper level and checked regularly to ensure proper preload. Improper pretensioning of bolts may lead to failure, equipment damage and, more importantly, injury to workers.

Bolt creep is another factor that should be monitored. The tightened bolts tend to creep or elongate over a period of time, thus reducing the preload. High temperature will also increase bolt creep, so this should be taken into account when formulating the torque inspection plan.

4 warning signals for bearing problems

Regular maintenance is helpful to prevent premature failure, but even the most faithful bearing will eventually show signs of wear. In order to extend their service life, please look for these common signs and take corrective measures according to the instructions.

Clearances or clearances in bearings usually indicate raceway wear. The new bearing is equipped with specific clearance to compensate for slight unevenness in the installation structure. Wear will greatly increase this clearance. In the machinery that drives the boom, the enlarged free play on the boom length enables it to swing back and forth under the load, thus reducing the "stiffness" in the extended boom. Use a dial indicator to check the bearing clearance, which measures the tilt of the structure when the boom is loaded.

Grinding, popping or clicking noises from bearings usually mean that there may be insufficient lubrication and/or excessive wear or loose bolts in the raceway. As mentioned earlier, lubricating bearings and purging lubricants are good methods to check metal particles.

An increase in torque or binding may mean uneven wear of the raceway. If the rotating torque of the bearing increases significantly or the bearing has tight spots, the load may be distributed unevenly. For example, for an excavator, the operator may feel the swing resistance and find that the swing of the upper boom exceeds the position where it should stop by one or two inches. At the advanced stage of wear, the bearing will burst and crack when the machine is digging and swinging.

The concave raceway is usually the result of bearing overload or repeated heavy load. Even a slight overload will cause the bearing race to sag, and the sag starting from 1/1000 inch will almost always become larger. The same is true for uneven loads. Using the boom and undercarriage at the same position each time for lifting (for example, using an excavator to dig at the roadside) will cause the bearing race to sag near the uneven load. If possible, change the approach angle from one job to another.

Less wear means less cost

By monitoring the symptoms of bearing wear and carrying out regular preventive maintenance, you can significantly reduce the possibility of premature bearing failure. This in turn minimizes costs, because it can keep the equipment running efficiently and avoid costly downtime and maintenance failures.