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A direct-acting brake applies force through a simpler arrangement with fewer mechanical connections. This can reduce maintenance time and reduce the chance of failure overall.
Direct-acting systems can also make routine tasks such as replacing pads and adjusting the air gap faster and easier. That matters on a mill where every additional hour of maintenance affects production, and in an industry where equipment rarely operates under ideal conditions. Mills may sit at high altitude, in extreme heat or cold, and far from a major service center. Dust, moisture, ice and limited access can turn small design differences into significant operational concerns.
The true cost of grinding mill brake selection
The vast size, power and throughput of gearless grinding mills make them central to mineral processing but also mean that any unplanned stoppage can be both costly and potentially dangerous.
For that reason, decisions about mill design tend to focus on the largest and most visible equipment: the mill itself, the motor, the drive and the bearings. Yet some of the most important decisions involve systems that receive far less attention during procurement. The braking system is one key example of this.
In many projects, the mine operator may not select it directly, but instead choose it as part of a wider mill package supplied by an original equipment manufacturer( OEM). The specification may leave room for different brake technologies, and the operator may not know which design has been chosen – or what that decision could mean over the mill’ s working life.
More than a parking brake
Large grinding mills typically operate around the clock. As such, the brake isn’ t used much on a day-to-day basis and instead comes into play predominately under two specific conditions.
The first is during regular maintenance, when the mill needs to be securely locked in position while personnel work inside on tasks such as liner replacement. Here, the brake must hold a vast, uneven load at the required angle and prevent any unintended movement.
The second situation is when a power failure or lubrication fault interrupts the supply of oil film to the mill’ s bearings. If this happens, the window for stopping the mill safely before the bearing runs dry is very narrow – typically just 8-12 seconds.
As such, the brake is not simply an accessory that holds the mill during planned work. It is a system that helps to protect people, production and one of the most valuable assets in the processing line.
Two approaches to the same task
There are two common designs for mill brakes: scissor-style and direct-acting brakes.
The scissor brake uses a series of mechanical links and joints to apply the braking force. It is an established technology and, in many cases, carries a lower initial price. That can make it attractive when an OEM must meet a performance specification while keeping the overall package commercially competitive.
However, the additional joints, links and moving parts can make the brake more complex to inspect and maintain. They also introduce more possible failure points. If a critical link or joint fails, the brake may lose its ability to operate completely.
Closing the information gap
The tension between scissor and directacting brakes reflects a wider issue in capital projects.
While scissor brakes typically carry a lower purchase price, they can prove considerably more expensive when viewed through the lens of total cost of ownership. With major mines often reporting costs of more than $ 100,000 per hour of unplanned downtime, the improved reliability and ease of maintenance associated with a directacting brake can quickly outweigh the initial savings offered by a lower-cost system. Operators can close this gap by becoming more involved in the brake specification. They should ask which technology the OEM intends to use, how it could fail, how long routine maintenance takes, what environmental protection it needs and what technical support will be available near the site.
Consultants and suppliers also have a role. By discussing braking technology earlier, they can help project teams understand that two compliant systems may carry very different long-term risks. Regal Rexnord, for example, draws on its wider mining and powertrain expertise through Svendborg Brakes™, whose direct-acting brakes are designed to offer a simpler, more fault-tolerant alternative to traditional scissor mechanisms, while making routine tasks such as brake-pad replacement and air-gap adjustment easier to carry out.
The aim should not be to mandate one solution for every mill. Site conditions, bearing design, maintenance strategy and commercial needs all differ. Rather, the aim is to make the choice visible and ensure that operators can assess it against the needs of the site over the full working life of the mill.
A grinding mill’ s brake may represent a small part of the total project cost, but it carries a much larger share of the operational risk. Operators should know which system they are buying – and what that choice may mean long after the mill enters service.
International Mining | OCTOBER 2026 39