NEW Bearing Doctor Mainten ance of Bearings

2 NSK commenced operations as the first Japanese manufacturer of rolling bearings back in 1916. Ever since, we have been continuously expanding and improving not only our product portfolio but also our range of services for various industrial sectors. In this context, we develop technologies in the fields of rolling bearings, linear systems, components for the automotive industry and mechatronic systems. Our research and production facilities in Europe, Americas and Asia are linked together in a global technology network. Here we concentrate not only on the development of new technologies, but...

Bearing doctor 3 Total Quality by NSK: The synergies of our global network of NSK Technology Centres. Just one example of how we meet our requirements for high quality. Partnership based on trust – and trust based on quality NSK is one of the leading companies with a long tradition in patent applications for machine parts. In our worldwide research centres, we not only concentrate on the development of new technologies, but also on the continual improvement of quality based on the integrated technology platform of tribology, material technology, analysis and mechatronics. More about NSK at www.nskeurope.com...

6 Introduction Generally, bearing inspection or housing inspection can identify the cause of the problem. Often the cause is attributable to poor lubrication, improper handling, selecting the wrong bearing, or not enough study of the shaft and housing. Usually the cause can be determined by considering operation of the bearing before the failure, investigating the lubrication conditions and the mounting condition, and carefully observing the damaged bearing itself. Sometimes bearings are damaged and fail both quickly and unexpectedly. Such premature failure is different from fatigue failure which...

Bearing doctor 7 Bearing Handling & Maintenance Precautions for Handling Since rolling bearings are high precision machine parts, they must be handled carefully. Even if high quality bearings are used, their expected life and performance cannot be attained if they are used improperly. The main precautions to be observed are as follows: (1) Keep the bearings and surroundings clean: Dust and dirt, even if invisible to the naked eye, have harmful effects on bearings. It is necessary to prevent the entry of dust and dirt by keeping the bearings and their environment as clean as possible. (2) Handle...

8 Mounting It is advisable to study the bearing mounting thoroughly since the quality of the bearing mounting influences the bearing’s running accuracy, life and performance. It is recommended that the mounting method includes the following steps. ›› Clean the bearing and surrounding parts. ›› Check the dimensions and finish conditions of related parts. ›› Follow mounting procedure. ›› Check if the bearing is mounted correctly. ›› Supply with correct kind and quantity of lubricant. Since most bearings rotate with the shaft, the bearing mounting method is generally an interference (tight) fit...

Bearing doctor 9 Machine size Operating procedure Bearing condition checks Small machine Manual operation. Turn the bearing by hand. If no problems are detected, then proceed to operate the machine. ››Stick-slip (Debris, cracks, dents) ››Uneven rotating torque (Faulty mounting) ›› Excessive torque (Error in mounting or insufficient radial internal clearance) Power operation. Initially start at a low speed and without a load. Gradually increase speed and load to reach rating. Check for irregular noise. Check for bearing temperature rise. Lubricant leakage. Discoloration. Large machine Idle operation....

10 Bearing Performance Factors Bearing Noise During operation, sound detection instruments (stethoscope, NSK Bearing Monitor, etc.) can be used to investigate the volume and characteristics of the bearing rotation noise. It is possible to distinguish bearing damage such as small flaking by means of its unusual yet characteristic noise. Bearing Vibration Bearing irregularities can be analyzed by measuring the vibrations of an operating machine. A frequency spectrum analyser is used to measure the magnitude of vibration and the distribution of the frequencies. Test results enable the determination...

Bearing doctor 11 Selection of Lubrication Bearing lubrication methods are divided into two main categories: grease lubrication and oil lubrication. A lubrication method is adopted that matches the application conditions and application purpose in order to attain best performance from the bearing. Table 3 shows a comparison between grease and oil lubrication. ›› Grease lubrication Grease is a lubricant that is made from base oil, thickener, and additives. When selecting a grease, it is necessary to selecta grease that is suitable to the bearing application conditions. There are large differences...

12 Bearing Performance Factors Replenishment and Replacement of Lubricant (1) Replenishing Interval Even if high-quality grease is used, there is deterioration of its properties with time; therefore, periodic replenishment is required. Figs. 2 (1) and (2) show the replenishment time intervals for various bearing types running at different speeds. Figs. 2 (1) and (2) apply for the condition of high-quality lithium soap-mineral oil grease, bearing temperature of 70° C, and normal load (P/C=0.1). ›› Temperature If the bearing temperature exceeds 70° C, the replenishment time interval must be reduced...

Bearing doctor 13 Operating temperature Speed Light or normal load Heavy or shock load –30 to 0°C Below limiting speed ISO VG 15, 22, 32 (Refrigerator oil) — 0 to 50°C Below 50% of limiting speed ISO VG 32, 46, 68 (Bearing oil, Turbine oil) ISO VG 46, 68, 100 (Bearing oil, Turbine oil) Between 50% and 100% of limiting speed ISO VG 15, 22, 32 (Bearing oil, Turbine oil) ISO VG 22, 32, 46 (Bearing oil, Turbine oil) Above limiting speed ISO VG 10, 15, 22 (Bearing oil) — 50 to 80°C Below 50% of limiting speed ISO VG 100, 150, 220 (Bearing oil) ISO VG 150, 220, 320 (Bearing oil) Between 50% and 100%...