1. Operation under overload. After calculating, a full loaded 12m3 mixer truck’s back supports are bearing the force of 1.32x105N, which means the each drum roller is bearing the force of 7.6x104N. If the truck starts working suddenly, the mixer drum will force the drum roller more than 7.6x104N at that moment. So the drum rollers are working under the overloading condition frequently.

2. Influenced by its own structure. Drum roller normally consists of roller, shaft, seals, bracket and two separated bearings. The demand is very strict on the bearing clearance. During the working, the lock nut will get loose and the bearing clearance will be loose too which will make the bearing eccentric wore and shorten its life.

3. Drum rollers are positioned under the feeding and discharge port. The mixing concrete is easily flowing into the drum roller which will destroy the shaft and bearings.

4. Maintenance hasn’t been done accordingly. According to the maintenance’s requirement, the drum roller has to be lubricated periodically to ensure the drum roller work successfully.

5. The hardness between the drum track ring and drum rollers is mismatching. The ideal condition between the kinematic pair of track ring and drum rollers should be---After one week’s operation, the friction surface between the drum track and drum roller should be very bright. After the cold hardening, the surface hardness of the drum track ring should be more than HB230. When the drum track ring rotates one circle, the drum rollers will rotate