Double row tapered roller bearing can bear heavy complex load (radial and axial) and has good rigidity. It can be fixed axially in both directions, with certain axial clearance or preload. They are mainly used in gearboxes, hoist and crane, rolling mills and mining machinery, such as tunnel boring machines. TDO type:  this kind of bearing has a double raceway outer ring and two inner rings, and a spacer between two inner rings. The bearing clearance can be adjusted by changing the thickness of the spacer. Because the axial clearance or preload has been adjusted during manufacturing, they are quick assembly components. These bearings are back-to-back configuration, so the load line is separated from the bearing axis. Because of this, the bearings can be used in a more rigid configuration, allowing for considerable tilting moments. This kind of bearing can bear both radial load and bidirectional axial load, and limit the bidirectional axial displacement of shaft or housing within the range of axial clearance of bearing. (As shown below) TDI type: the bearing of this structure has a double raceway inner ring and two outer rings with two rows of rollers and cage assembly. Double row rollers are arranged face to face. Usually a spacer is arranged between two outer rings. Select the size of the spacer to get a certain axial clearance or preload. (As shown below)

图(1)

图(2)

tolerance

The tolerance of metric double row tapered roller bearing follows to GB / t307.1-1994 / ISO 492-2002. The tolerance value of imperial double row tapered roller bearing conforms to ANSI / ABMA standard.

BEP

Double rows and four rows tapered roller bearing BEP follows JB/T8236-1996, see table below

BEP calculation follow below formula:

Ga=Gr.cotαor Ga=Gr.1.5/e
Ga=axial clearance 
Gr=radial clearance 
α=contact angle 
e=Fa/Fr limit value (see bearing specification)

Permitted misalignment

The misalignment outer ring of double row tapered roller bearing relative to the inner ring can only be borne by roller and raceway. This will cause bearing unbalance loading, which should be avoided.

Minimum load

The double row tapered roller bearing must always bear a certain minimum load, especially when the bearing is running at high speed or the direction of the load under high acceleration or rapid change. The inertia force of roller and cage and the friction of lubricant will have bad effect on the rolling condition in the bearing configuration, and may cause destructive sliding between roller and raceway.

Minimum radial load can be estimated per below formula:
Frm=0.02C
Frm=minimum radial load, kN
C=rated static load (see bearing specification), kN

When starting at low temperature or lubricant viscosity is very high, even higher load is required. The dead weight of the components supported by the bearing plus the external force generally exceeds the necessary minimum load. Otherwise, additional radial load must be applied to the double row tapered roller bearing. The radial preload can be obtained by adjusting the positions of inner or outer rings, this is especially easy for tapered roller bearings.

Equivalent dynamic load

When Fa/Fr ≤ e， P = Fr + Y1Fa
When Fa/Fr > e， P = 0.67 Fr + Y2Fa
Coefficient e, Y1 and Y2 see bearing specification.

Equivalent static load

P0 = Fr + Y0Fa

Coefficient Y0 see bearing specification.