Tapered Roller Bearings
single row, matched
- Absorption of high axial and radial forces
- Available in various preload classes
- Absorption of overturning moments from both sides
Matched single row tapered roller bearings feature angular raceways of inner and outer ring and a resulting force-transferring contact angle. Due to this, an axial load always induces a radial load and the other way around, which is why tapered roller bearings are always combined with a second bearing. Paired, they can in addition to radial forces also absorb axial and combined forces and are particularly suitable for medium to high speeds. Single row tapered roller bearings can be disassembled which facilitates a separate assembly of inner and outer ring.
Dimensions and Tolerances
KRW supplies single row tapered roller bearings with normal tolerance (PN) in accordance to DIN 620-2 (Tolerances for roller bearings) and ISO 492 (Radial bearings - Dimensional and geometrical tolerances). All other deviating or special tolerances must be specified with the order.
The general dimensions of the single row tapered roller bearings are standardised by ISO 355 (Tapered roller bearings - Boundary dimensions and series designations) and DIN 720 (Rolling Bearings - Tapered roller bearings). Inch bearings conform to ANSI/ABMA Standard 19.2 (Tapered Roller Bearings - Radial Inch Design).
Matched single row tapered roller bearings are separable and non-latching bearings. In addition to high radial forces, they can absorb single-sided axial forces as well as, in combination with a second mirror-image arranged bearing, two-sided axial forces. For combined bearing sets there is a distinction between O-, X-, or tandem arrangement based on pressure line contact. Bearings in X-arrangement are less suitable for the absorption of moment loads while the O-arrangement is very rigid and only allows small overturning clearance. For tandem arrangements, the pressure lines of two bearings run in one direction which results in only single-sided absorption of axial forces.
X-, O-, and tandem arrangement for tapered roller bearings
Roller profiling and tension distribution of tapered rollers in comparison. Left without profiling, right with profiling
Due to the logarithmic profiling of the tapered rollers, damaging edge tension and resulting premature failure are avoided.
The bearing clearance is chosen by the customer and application and is adjusted by the manufacturer with a spacer ring.
By default, matched single row tapered roller bearings by KRW are equipped with a rolling element riding solid brass window-type cage (suffix: MP) or a rolling element riding steel plate cage. Other cage designs are available on request or chosen for specific applications and labelled accordingly on the bearing.
|A||Modified internal design|
|B||Modified internal design, contact angle 20°|
|X||Bearings with boundary dimensions adapted to ISO standards|
Compensation of Angular Misalignments
Single row tapered roller bearings are of limited suitability for compensation of misalignments. The admissible misalignment between inner and outer ring depends on the bearing size, the internal bearing design, the clearance fit, and the acting of forces and moments. Misalignments cause harmful movement of the rolling elements and produce additional stresses in the bearing which reduce its operating life.
KRW distinguishes between kinematic limiting speed nG and thermal reference speed nth. The kinematic limiting speed is a practical mechanical limit value and is based on the mechanical fatigue strength of the rolling bearing as a function of its installation situation and lubrication. The limit speed must not be exceeded even under optimum operating conditions without prior consultation with KRW.
The thermal reference speed represents the equilibrium between the heat generated in the bearing by friction and the heat flow dissipated. It is standardised in DIN ISO 15312 (Rolling bearings - Thermal reference speed).
Admissible Operating Temperatures
The admissible operating temperature of a bearing is limited by cage material, dimensional stability of the bearing components (ball race and rolling elements), as well as lubrication. By default, KRW bearings are stabilised up to 200°C (S1). KRW provides roller bearings for higher operating temperatures on request.
For dynamically loaded bearings
The service life formula according to ISO 281 L10 = (C/P)p for dynamically loaded bearings requires an equivalent load (P) from constant direction and size. To calculate P, calculation factors and the ratio of axial and radial load are required.
Equivalent Dynamic Bearing Load P
The equivalent bearing service life for the tapered roller bearings depends on the ratio Fa/Fr. The equivalent dynamic bearing load can, differing from the ISO 281, be determined only for one rolling element row using the following formula:
|P||equivalent dynamic load||[kN]|
|Fr||dynamic radial force||[kN]|
|Fa||dynamic axial force||[kN]|
|e||calculation factor, see chart||[-]|
|Y1||calculation factor, see chart||[-]|
|Y2||calculation factor, see chart||[-]|
For statically loaded bearings
Dynamic dimensioning loses its validity for bearings rotating at very low speeds (n x dm ≤ 4000 mm/min). The static load safety factor S0 is calculated as follows:
|S0||static load safety factor||[-]|
|C0||static load rating (from bearing chart)||[kN]|
|P0||equivalent static bearing load||[kN]|
|dm||mean bearing diameter [dm = (D+d)/2]||[mm]|
Static load capacity
|F0r||max. radial static force||[kN]|
|F0a||max. axial static force||[kN]|
|Y0||calculation factor, see bearing chart||[-]|
Minimum Radial Load
A minimum load is required for the reliable operation of a rolling bearing. If the minimum load is not reached, slippage may occur. The minimum radial load for tapered roller bearings is roughly assumed to be 2% of the static load rating C0 of the bearing. If the value falls below this value, please consult KRW Application Technology.