Optimizing the Service Life Of A Conveyor Belt Drive

Besides the oil seals, shaft-hub connection, and the lubricant used, the key factors in determining the service life of an industrial gear unit are the rolling bearings, the loads placed on them, and the gearing’s load capacity for reliably transferring the torque.

These loads primarily result from the torques and the radial and axial forces that affect the output shaft of the gear unit during operation and are consequently transferred to the bearings. Other factors that influence the bearing service life are the type of gear oil, the oil level in the gear unit, and the application’s ambient conditions. When optimizing the service life of a gear unit to suit a given application, you need to consider the bearing service life as well as the power loss in the gear unit.

Bearing Service Life

The bearing service life corresponds to the number of revolutions or operating hours that a bearing can withstand at a constant speed without sustaining damage – and without material fatigue.

According to the ISO 281 standard, the nominal bearing service life L_10h is the service life achieved by 90% of bearings tested under the same conditions. In this context, figure 10 stands for a failure probability of 10% and is calculated from the dynamic load rating C_r and a dynamically equivalent load P.

To calculate the reference value for nominal bearing service life L_10r as per ISO/TS 16281, the load of the individual rolling elements, the tilting of the bearing rings, the forces caused by the thermal expansion of the materials, and crossover influences from other gear unit stages are taken into account alongside the dynamic load rating C_r.

Power Loss in The Gear Unit

Due to hydraulic effects in the gear unit oil, and due to the seal, gearing, and bearing, there is a certain percentage of loss in gear units during the conversion of rotational speed and torque on the output side compared to the drive power delivered by the motor. To optimize a gear unit for an application, it is important to cut down this power loss P_loss as much as possible.