GB/T 24609-2023 Rolling bearings - Thermal speed rating - Calculation
1 Scope
This document defines the thermal speed rating for oil bath lubricated rolling bearings and defines calculation principles for the determination of this parameter. The parameter determined in accordance with this document applies to rolling bearings of the given series and sizes of standard design or of a design that, from a frictional point of view, can be related to a standard design bearing.
In most cases of standard assembly, the permissible temperature determines the maximum operating speed. Heating of the assembly is then generated by the bearing.
Thrust ball bearings are excluded from this document as kinematic effects do not allow the thermal speed rating defined in this document to be applied.
Note 1: In Annex A mean values for the coefficients f0r and f1r are given - f0r for calculating viscous losses of oil bath lubricated bearings and f1r for calculating frictional losses of bearings.
Note 2: Explanatory notes on the limiting criterion are given in Annex B.
Note 3: In Annex C the reference conditions for grease lubrication are defined. The reference conditions are chosen such that the thermal speed rating for grease lubrication is identical to that for oil bath lubrication.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 76 Rolling bearings - Static load ratings
Note: GB/T 4662-2012, Rolling bearings - Static load ratings (ISO 76:2006, IDT)
ISO 1132-1 Rolling bearings - Tolerances - Part 1: Terms and definitions
Note: GB/T 4199-2003, Rolling bearings - Tolerances - Definitions (ISO 1132-1:2000, MOD)
ISO 5593 Rolling bearings - Vocabulary
Note: GB/T 6930-2002, Rolling bearings - Vocabulary (ISO 5593:1997, IDT)
ISO 5753-1 Rolling bearings - Internal clearance - Part 1: Radial internal clearance for radial bearings
Note: GB/T 4604.1-2012, Rolling bearings - Internal clearance - Part 1: Radial internal clearance for radial bearings (ISO 5753-1:2009, IDT)
ISO 15241 Rolling bearings - Symbols for physical quantities
Note: GB/T 7811-2015, Rolling bearings - Symbols for physical quantities (ISO 15241:2012, IDT)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1132?1 and ISO 5593, and the following, apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
——ISO Online browsing platform: available at https://www.iso.org/obp
——IEC Electropedia: available at http://www.electropedia.org/
3.1
thermal speed rating
inner ring or shaft washer rotational speed at which equilibrium is reached between the heat generated by the friction in the bearing and the heat flow emitted through the bearing seating (shaft and housing) under the reference conditions
Note 1: The thermal speed rating is one among various criteria which permit comparison of the different rolling bearing types and sizes with regard to their suitability for operation at high speed.
Note 2: Mechanical and kinematic criteria which could lead to further speed limitations are not taken into account by the thermal speed rating.
3.2
reference conditions
conditions for the thermal speed rating related to
a) the mean temperature of the stationary outer ring or housing washer of the bearing, i.e. the reference temperature, and the mean environmental temperature, i.e. the reference ambient temperature;
b) the factors determining the friction losses in the bearing, such as:
——the magnitude and direction of the bearing load;
——the method of lubrication, type of lubricant, its kinematic viscosity and quantity;
——other general reference conditions;
c) the heat flow emitted from the rolling bearing defined as the product of the “heat emitting reference surface area of the rolling bearing” and the “reference heat flow density specific to the rolling bearing”.
Note: The heat emission under the reference conditions is based on empirical values and represents the heat emission of the real bearing arrangement. It is, however, independent of the real design of the bearing arrangement.
3.3
heat emitting reference surface area
sum of the contact areas, between inner ring (shaft washer) and shaft and between outer ring (housing washer) and housing, through which the heat flow is emitted
3.4
reference load
bearing load, determined by the reference conditions, which causes the load-dependent frictional moment
3.5
reference heat flow
heat flow, emitted by thermal conduction through the heat emitting reference surface, and caused by frictional resistance, when the bearing is operating under the reference conditions
3.6
reference heat flow density
reference heat flow divided by the heat emitting reference surface area
3.7
reference ambient temperature
mean environmental temperature of the bearing arrangement under the reference conditions
3.8
reference temperature
mean temperature of the stationary outer ring or housing washer of the bearing under the reference conditions
4 Symbols and units
For the purposes of this document, the symbols given in ISO 15241 and the following apply.
Table 1 - Symbols and units
5 Reference conditions
5.1 General
The reference conditions in this document are mainly based on the operating conditions of the most frequently used bearing types and sizes.
5.2 Reference conditions determining the frictional heat generation
5.2.1 Reference temperatures
Reference temperature of the bearing on the stationary outer ring or housing washer: θr = 70 °C.
Reference temperature of the bearing environment: θAr = 20 °C.
5.2.2 Reference load
5.2.2.1 Radial bearings with contact angle 0° ≤ α ≤ 45°
5 % of the basic static radial load rating C0r as pure radial load.
In the case of a single-row angular contact bearing, the reference load refers to the radial component of that load which causes a purely radial displacement of the bearing rings in relation to each other.
