Altra designs overload protection for bespoke universal joints

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The pressures on recycling plants to maintain a constant throughput of materials are immense, and one of the toughest jobs in the industry is the shredding of metal parts. The torque required to rip the metal into small pieces is massive and rotor jams are relatively common. One metal recycler found that the damage to the drive train caused by excessive torque generated during these jams was too costly. Fortunately Altra Couplings was able to engineer a bespoke, overload protection system.

A major international metals recycler was suffering from recurring damage to the motors and universal joints caused by torque overload when the shredder rotors jammed caused by an un-shreddable obstruction. During a jam the torque generated was so excessive that damage was being caused to the components within the drive train, such as the universal joint bearings and even the motor itself. In these instance not only could the repair bill be very costly, but the downtime could be considerable while the obstruction was cleared and the drive train repaired or replaced. In total, up to 48 hours of downtime was required each time the rotors jammed.

In an effort to save on maintenance costs and reduce downtime, the site manager turned to Ameridrives, a division of Altra Couplings, to see if its engineers could design a solution. As one of world’s largest manufacturers of industrial couplings, Altra Couplings is able to develop bespoke systems for most industries which incorporate reliability with reduced operation costs.

Having assessed the application, Altra’s engineers set about designing an overload protection system into the universal joints which would protect the vital components within the drive train in the event of a jam. An Americarden U3440 universal joint was modified to incorporate a shear pin overload device. When a rotor jam occurs, and torque reaches in excess of 533,000Nm, the pins shear, disengaging the driven end of the universal joint from the driving end and protecting the components from expensive damage.

This also meant that, after clearing the jam, a maintenance crew can replace the pins and have the shredder operational in less than 4h – reducing downtime by over 95 per cent.

In fact, the savings the savings made by reducing the maintenance and repair costs, plus cutting downtime, are so significant that the initial cost of the device was paid for after the first overload. The systems has been so successful that it has since been rolled out for use on shredders at all of the company’s other locations.

For more details about bespoke overload protection design, please visit

26 November 2014

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