T-Blog, Your Bearing Wikipedia

Dynamic and static load ratings for spherical plain bearings are important for understanding the life of a bearing, but what do each specify? Read on to learn more about these important classifications. Dynamic Load Rating for Spherical Plain Bearings Dynamic load rating is used for calculations when the spherical plain bearing is subjected to dynamic stress. It represents the load, constant in magnitude and direction, under which a basic rating service life, expressed as a sliding distance, will be attained for continuous oscillating movement at a defined sliding velocity and at room temperature. This rating presupposes that the load acting on radial and angular spherical plain bearings and on rod ends is purely radial and that the load acting on spherical plain thrust bearings is purely axial and acts centrically. Dynamic stresses occur when tilting, oscillatory or rotational movements are made under load as well as micro-sliding movements under alternating loads, e.g. resulting from vibration, or loads which alternate at high frequency. The various types of dynamic stress often occur in combination. The values of load ratings are always dependent on the definition used. It is therefore not always possible to make direct comparisons with load ratings published by other…

We have assembled a wide variety of frequently asked questions (FAQs) about bearings (e.g. ball bearings, roller bearings, plain bearings, linear bearings) and bearing related products (and bearing services too). Just refer to the question you’re interested in below and you will be taken to a remarkably succinct, straight-forward, and accurate answer: Q1: Can bearings be refurbished? Yes, but it depends… Generally speaking, for small bearings it is uneconomical to attempt to refurbish a bearing product. However, for larger size bearings (6 inch bore and above) there potentially could be economic gains. In particular, bearings such as slewing rings, cylindrical roller bearings, and spherical roller bearings are candidates for refurbishing. But beyond the accumulated wear there are many other factors involved in this financial decision including maintenance cycles, lubrication, MTBF, environmental considerations and more. Q2: What’s The Difference Between Bearing Seals And Shields? Seals and shields are both in place to keep contaminants out of a bearing. In order of effectiveness, the enclosures that are offered are as follows: metal shields, rubber non-contact seals, Teflon non-contact seals, and rubber contact seals. Not surprisingly, as the sealing performance is increased, the torque required to turn the bearing will also increase due…

1) High carbon chromium bearing steel High carbon chromium bearing steel specified in JIS is used as a general material in bearing rings (inner rings, outer rings) and rolling elements (balls, rollers).Their chemical composition classified by steel type is given in “Table 13-1 Chemical composition of high carbon chromium bearing steel”.Among these steel types, SUJ 2 is generally used. SUJ 3, which contains additional Mn and Si, possesses high hardenability and is commonly used for thick section bearings.SUJ 5 has increased hardenability, because it was developed by adding Mo to SUJ 3.For small and medium size bearings, SUJ 2 and SUJ 3 are used, and for large size and extra-large size bearings with thick sections, SUJ 5 is widely used.Generally, these materials are processed into the specified shape and then undergo hardening and annealing treatment until they attain a hardness of 57 to 64 HRC. 2) Case carburizing bearing steel (case hardened steel) When a bearing receives heavy impact loads, the surface of the bearing should be hard and the inside soft.Such materials should possess a proper amount of carbon, dense structure, and carburizing case depth on their surface, while having proper hardness and fine structure internally.For this purpose, chromium steel…

Since the characteristics of materials used for cages greatly influence the performance and reliability of rolling bearings, the choice of materials is of great importance. It is necessary to select cage materials in accordance with required shape, ease of lubrication, strength, and abrasion resistance. Typical materials used for metallic cages are shown in Tables 13-3 and 13-4. In addition, phenolic resin machined cages and other synthetic resin molded cages are often used. Materials typically used for molded cages are polyacetal, polyamide (Nylon 6.6, Nylon 4.6), and polymer containing fluorine, which are strengthened with glass and carbon fibers. Koyo

In shipping bearings, since they are covered with proper anti-corrosion oil and are wrapped in antitarnish paper, the quality of the bearings is guaranteed as long as the wrapping paper is not damaged. If bearings are to be stored for a long time, it is advisable that the bearings be stored on shelves set higher than 30cm from the floor, at a humidity less than 65%, and at a temperature around 20℃. Avoid storage in places exposed directly to the sun’s rays or placing boxes of bearings against cold walls. Koyo

Periodic and thorough maintenance and inspection are indispensable to drawing full performance from bearings and lengthening their useful life. Besides, prevention of accidents and down time by early detection of failures through maintenance and inspection greatly contributes to the enhancement of productivity and profitability. Cleaning Before dismounting a bearing for inspection, record the physical condition of the bearing, including taking photographs.Cleaning should be done after checking the amount of remaining lubricant and collecting lubricant as a sample for examination. A dirty bearing should be cleaned using two cleaning processes, such as rough cleaning and finish cleaning.It is recommended that a net be set on the bottom of cleaning containers. In rough cleaning, use brushes to remove grease and dirt. Bearings should be handled carefully. Note that raceway surfaces may be damaged by foreign matter, if bearings are rotated in cleaning oil. During finish cleaning, clean bearings carefully by rotating them slowly in cleaning oil. In general, neutral water-free light oil or kerosene is used to clean bearings, a warm alkali solution can also be used if necessary. In any case, it is essential to keep oil clean by filtering it prior to cleaning.Apply anti-corrosion oil or rust preventive grease on…

It is important for enhancing productivity and profitability, as well as for accident prevention that abnormalities in bearings are detected during operation.Representative detection methods are described in the following section. 1）Noise checking Since the detection of abnormalities in bearings from noises requires ample experience, sufficient training must be given to inspectors. Given this, it is recommended that specific persons be assigned to this work in order to gain this experience.Attaching hearing aids or listening rods on housings is effective for detecting bearing noise. 2）Checking of operating temperature Since this method utilizes change in operating temperature, its application is limited to relatively stable operations.For detection, operating temperatures must be continuously recorded.If abnormalities occur in bearings, operating temperature not only increase but also change irregularly.It is recommended that this method be employed together with noise checking. 3）Lubricant checking This method detects abnormalities from the foreign matter, including dirt and metallic powder, in lubricants collected as samples.This method is recommended for inspection of bearings which cannot be checked by close visual inspection, and large size bearings. Koyo

In selecting bearings, the most important thing is to fully understand the operating conditions of the bearings. The main factors to be considered are listed below: 1.Installation space Bearing can be installed in target equipment When a shaft is designed, its rigidity and strength are considered essential; therefore, the shaft diameter, i.e., bore diameter, is determined at start.For rolling bearings, since wide variety with different dimensions are available, the most suitable bearing type should be selected. 2.Load Load magnitude, type and direction which applied(Load resistance of bearing is specified in terms of the basic load rating, and its value is specified in the bearing specification table.) Since various types of load are applied to bearings, load magnitude, types (radial or axial) and direction of application (both directions or single direction in the case of axial load), as well as vibration and impact must be considered in order to select the proper bearing. The following is the general order for radial resistance ;(deep groove ball bearings < angular contact ball bearings < cylindrical roller bearings < tapered roller bearings < spherical roller bearings) 3.Rational speed Response to rotational speed of equipment in which bearings will be installed(The limiting speed for bearing…

Bearings with diameters between 36 and 169 in. typically cost a lot and have long lead times, forcing end users to keep spare bearings on hand or face extensive downtime should a bearing fail. Therefore, it can make sense to replace a bearing before it degrades. Bearings removed this way often make good candidates for repair or refurbishment. But what qualifies a bearing as repairable? How are repairs carried out? And what kind of results should users expect? Upon receiving a bearing for repair, our company evaluates it and gives the customer a detailed report that suggests one of several approaches. These range from cleaning, verifying clearances, and relubricating the bearing, to replacing major components such as inner or outer races and rolling elements. After cleaning the bearing, we first check the raceway’s integrity by looking for excessive wear or damage. We also measure the surface hardness and perform advanced ultrasonic backscattering to determine the hardened-case depth. These measurements are critical when we must regrind the raceway because enough of the hardened case must remain to support the anticipated ball and roller loads. When customers provide precise loads, we can simply calculate the needed minimum effective-case depth (ECD), usually measured…

Massive rotors in hydroelectric generators, large ball mills, rolling mills, large electric motors, and steam and gas-turbine generators normally operate with great efficiency on oil films in sleeve and thrust bearings. But trouble arises when rotational speed is too low, as it is at starting and stopping, to generate a complete oil film. Then frictional drag and wear increase with metal-to-metal contact between the bearing and rotating shaft. So, how do engineers minimize friction and wear at low speed? The answer is hydraulic lift with pockets that provide oil-film lubrication by lifting a slow-turning shaft off its bearing surface. At low speeds, an auxiliary pumping system with typical pressures of 1,000 to 4,000 psi can float the rotor on an oil film. Once rotational speed reaches the 20 to 30-rpm range, a hydrodynamic bearing operating-fluid film is usually established and can take over the bearing task from the lift pump. To use additional hydraulic lift, designers must carefully calculateoil-feed rates, oil pressures, and bearing lift height. Although the authors suggest engineers follow the general guidelines that follow in both journal and thrust bearings, consulting manufacturer data for specific recommendations is also important. Journal bearings In sleeve journal bearings, pressurized hydraulic…