Polymer bearings manufacturer Vesconite Bearings reported last month that, after more than nine months of operation underground, a Vesconite bearing installed on a large underground jaw crusher at the Palabora copper mine was still performing to requirements and “has been instrumental in overcoming premature wear and shaft damage on the crusher”.

The company added that even when steel entered the ore stream and damaged other crusher components, the Vesconite bearing remained undamaged.

It noted that, initially, bronze bearings were selected for the application. However, during initial 24-hour testing, the bronze bush and shaft experienced pickup – or metal transfer from the bearing to the shaft – causing excessive noise and bearing wear.

Although the bronze bearings were supplied with dedicated grease lubrication, the small oscillating movement was insufficient to distribute the lubricant effectively across the bearing surface, creating a scenario in which conventional lubrication could not adequately protect the full bearing area, Vesconite Bearings pointed out.

Its Vesconite solution was subsequently evaluated as a replacement bearing material.

Because the crushers were critical to the underground mine’s operation, the Vesconite material underwent a “stringent evaluation” before being accepted.

The original bearing groove design and lubrication specification were retained, and the Vesconite bearings were machined to the required interference fit and running clearance. The bearings were cooled with dry ice for three to four hours before they were installed on the crusher.

“The cooling caused the bearing to contract sufficiently to overcome an interference fit of about 1.4 mm, allowing it to be slid into position without the heavy equipment that would otherwise have been required.”

The crusher was tested for three weeks.

Reportedly, crusher operation was significantly quieter and when the shaft was removed for inspection there was no significant bearing wear beyond bedding-in wear and no wear on the shaft.

This demonstrated an important advantage of Vesconite solutions in applications where lubrication is difficult to distribute.

Vesconite’s self-lubricating properties allowed the bearing to continue operating successfully despite the grease not being spread across the entire bearing surface. Further, the material’s slightly increased running clearance and lower hardness compared with bronze enabled the operator to accommodate the slight housing misalignment without requiring the housing to be line bored.

“This historical application illustrates the importance of selecting bearing materials based on actual operating conditions rather than relying solely on conventional choices,” the company commented.

In this case, the combination of very high loads, limited oscillation, difficult lubrication, deep-underground access and the consequences of equipment downtime created conditions in which Vesconite offered advantages over the bronze bearings.

For the Palabora crusher, the result was a quieter bearing operation, extended wear life and a bearing that can be installed and maintained without heavy equipment in one of the world’s most demanding mining environments, the company concludes.