TAPERED ROLLER BEARINGS OPERATING TEMPERATURES

● Operating temperatures   

   Bearingsoperate in awide range of applications and environments.In most cases, bearing operating temperature is not an 

   issue.Some applications, however, operate at extreme speeds or inextreme temperature environments. In these cases, care 

   must be taken not toexceed the temperature limits of the bearing.Minimum temperature limits are primarily based on 

   lubricantcapability. Maximum temperature limits are most often based on material and/or lubricant constraints, but also may

   be based on accuracy requirements of the equipment that the bearings are built into.These constraints/limitations are discussed below.

● Bearing material limitations

   Standard bearing steels with a standard heat treatment cannot maintain a minimum hardness of 58 HRC much above 120° C

   (250° F).Standard  tapered roller and ball bearings are dimensionally stabilized from -54°C (-65° F) up to 120°C (250° F),. Upon 

   request, these bearings can be ordered to higher levels of stability as listed below. 

Fig.1.

   Temperatures exceeding the limits shown in fig1 require special high-temperature steel. Consult your engineer for availability

   of specific part numbers for non-standard heat stability or high-temperature steel grades.Suggested materials for use in balls,

   rings and rollers at various operating temperatures are listed in fig2. Also listed are chemical composition recommendations, 

   hardness recom-mendations and dimensional stability information.Operating temperature affects lubricant film thickness and

   setting, both of which directly influence bearing life. Extremely high temperatures can result in a reduced film thickness that 

   can lead to asperity contact between contacting surfaces.Operating temperature also can affect performance of cages, seals 

   and shields, which in turn can affect bearing performance.Materials for these components and their operating temperature 

   ranges are shown in fig3.

● Lubrication limitations

   Starting torque ingrease-lubricated applications typically increasessignificantly at cold temperatures. Starting torque is not 

   primarily a function of the consistency or channel properties of the grease.Most often, itis a function of the rheological properties

   ofthe grease.The high-temperature limitfor greases is generally a function of the thermal and oxidation stability of the base oil in

   the grease and the effectiveness of the oxidation inhibitors.

● Equipment requirements

   The equipment designer must evaluate the effects of temperature on the performance of the equipment being designed. 

   Precision machine tool spindles, for example, can be very sensitive to thermal expansions. For some spindles, it is important 

   that the temperature rise over ambient be held to 20° C to 35°C (36° F to 45°F).Most industrial equipment can operate at 

   considerably higher temperatures. Thermal ratings on gear drives, for example, are based on 93° C (200° F). Equipment such

   as gas turbines operatescontinuously at temperatures above 100° C(212°F). Running athigh temperatures for extended periods

   of time, however, may affect shaft and housing fits, if the shaft and housing are not machined and heat-treated properly.

   Although bearings can operate satisfactorily up to 120° C (250° F),an upper temperature limitof 80° C to 95°C (176° F to 203° 

   F) is more practical. Higher operating temperatures increase the risk of damage from transienttemperature spikes. Prototype

   testing ofthe application can help define the operating temperature range and should be conducted if possible. It is the 

   responsibility of the equipment designer to weigh all relevant factors and make the final determination of satisfactory 

   operating temperature.Fig 2 and 3 provide standard operating temperatures for common bearing component materials. 

   They should be used for reference purposes only. Other bearing component materials are available on request. 

Fig.2.  Operating temperatures for bearing component materials

Fig.3.  Operating temperatures for bearing component materials