Before getting into details, it’s of foremost importance to understand what a “bearing” actually is. Bearings are mechanical components in machines that help to provide rotation, when and where it’s required. Hence, a bearing is crucial in any machine to provide movement. Now that we understand the functionality of a bearing, let’s move on to important factors to consider while selecting a bearing for high temperature environments.
Environments that cross limits of standard operating temperatures and pressures require bearings that can withstand these outer forces and still perform safely and efficiently. Examples of such volatile surroundings can be found in steel production, kilns, heat treatment furnaces, and automotive paint baking ovens. Furthermore, butterfly valves, high pressure turbines and nuclear energy plants also capitalize on bearings that can ensure no failures when they are in operation. Bearings built in order to handle such environments not only are of essence for the machines, to complete their functionalities, but they also tend to contribute to reduce industrial waste by having longer durability.
Importance of using a high temperature bearing
Carter Manufacturing produces high precision bearings for multiple types of machines that need standard operating temperature to function. These bearings are built from chrome steel (52100). These can also be altered and customized as per the requirements of individual applications. The heat range for the performances of these bearing is between 120°C (248°F) to 150°C (302°F). But when the temperature gets higher and crosses this limit, it results in the stiffening of the bearing leading them toward breakage and causing them to fail prematurely. Fortunately, advanced heat treatment processes have been devised for such circumstances. With such advance treatments, the bearings can withstand temperatures up to 330°C (626°F).
Despite this achievement, other components must also be brought into perspective. It must be kept in mind that adequate lubricant is required for the bearings to function in high temperature scenarios. There will always be a potential threat that the specified radial internal clearance within bearings can be eradicated at high temperatures because of the incompatibility of coefficient of thermal expansion, rings, shafts, balls and housing.
Tips to select the best high temperature bearing configuration
High temperature bearing configuration also plays a vital role in the performance of the bearing. In high temperature and high pressure environments, few other elements also play a significant role like bearing configuration, load capacity, speed and temperature ratings. Ultimately all these determinants decide how effectively and efficiently will the bearing function for a particular application. Hybrid and ceramic bearings have proven to give the best results when the machines surpass the 330°C temperature mark. Other steel bearings like M50, BG42, and XD16N can be classified as hybrid bearings that deliver remarkable results at higher speeds. Materials like silicon nitride, silicon carbide and zirconia are known to hold up well against temperatures ranging between 500°C to 1200°C. To increase the operating torque, a thick grease is used, which is available in dry and solid lubricant form. The dry form is known as WS2 and MoS2 while the solid lubricant form is known as graphite solid fill.
Other elements to consider when choosing a high temperature bearing
Apart from the factors mentioned above, fits and tolerances are also elements to be mindful of. Keeping the high temperatures in perspective, it is of much significance to ensure that the bearing design must work in coordination with optimum shaft and housing fit. The coefficient of thermal expansion of all the parts involved in the application determine the fit of the bearing requiring it to be loose or tight as per the application.
Moreover, it is essential to ensure that the yield stress of the bearing material falls below the hoop stress of the bearing. The bearing internal clearance can vary with the fit at operating temperature, which too is crucial to be monitored. It is to be noted when keeping all things in planning that some ceramic bearings are sensitive to the rate of temperature fluctuations.
Carter is touching new highs by creating advanced materials to produce special bearings to work in high temperature environments. While other standard bearings fail to bring out the desired results, bearings manufactured by Carter, in Europe, give excellent performances whilst conforming to ISO standards. These are ideal for high temperature environments and can optimize the productivity of difficult applications.
As per research, there is a gap in the market for the growth of high temperature bearings. Applications like ultra-high vacuum require the operator to carry out the “bake-out” process at high temperature so the materials are in coalition to make sure the threats of “outgassing” are curtailed. Whilst all this is being taken into consideration the ultimate goal of maximizing system performance is fully met. In order to meet the demands of more extreme temperature applications, Carter manufactures completely customizable ceramic and hybrid bearings, which can help customers, reach their goals, without any compromises on efficiency and durability in extreme temperatures.