Stabilizing in extreme conditions with Nord-Lock® Steel Washers

Nord-Lock wedge-locking washers secure bolted joints even when exposed to severe vibration and dynamic loads.

When solutions are implemented by large-scale mines to prevent bolt loosening from intense vibration, it proves their capabilities in other sectors. At the Spence mining operation in northern Chile, steel versions of Nord-Lock’s wedge-locking washers were implemented to secure a critical machine asset under extreme conditions, ensuring reliable performance and improved safety.

Located in Chile’s Atacama Desert, Spence is a copper mine with an annual output of just over a quarter of a billion tons. According to Andreina Pérez, Sales Engineer for Nord-Lock in Latin America, the company connects to such mining operations through third-party distributors. And in the fall of 2024, one distributor that was a direct supplier to Spence was asked about solutions for securing bolted connections experiencing excessive vibration.

An environment prone to extreme vibrations

Like many modern mines, Spence processes minerals on-site and utilizes a large semi-autogenous grinding (SAG) mill to break up large pieces of ore. Spence’s SAG mill is powered by a massive gearless mill drive (GMD) system that’s directly mounted to the mill’s shell. GMDs deliver immense torque with mechanical simplicity and generate extreme vibrations. By October of 2024, the GMD at Spence was vibrating intensely enough to continually loosen the bolts on its rotor cover, requiring frequent maintenance.

As Pérez explains, loose bolting on vital machinery like Spence’s GMD not only disrupts operations but also poses a danger to workers and the machine itself.

“Providing an effective solution would avoid downtime costs for maintenance but also potential damage to the equipment, because this part of the application is a critical point to take care of,” she says.

Significantly improved safety and efficiency

Based on the distributor’s recommendation, Spence replaced all conventional washers on the GMD’s rotor cover – as well as the stator generating the magnetic field to drive the GMD rotor – with Nord-Lock® NL 64 Steel Washers. The wedge-locking design maintains clamp force to secure bolted joints against unintentional loosening, while the steel composition provides additional durability and corrosion resistance.

“Since installation, we have had no issues with bolt loosening, which has significantly improved equipment operation and safety,” says a spokesperson for Spence. “We would recommend this product to any mining operation seeking reliability and efficiency.”

However, Pérez argues that success at Spence proves the effectiveness of Nord-Lock’s washers in non-mining sectors as well.

“The fact that the washer was a solution proves its effectiveness and reliability,” she says. “But there’s no single application, and there’s no sole industry for it. It’s a product that will also work in other industries where most requirements are less demanding.”