Underground Mining Scalers - What They Are and What Roof Scaling Machines Are Used For

After drilling and blasting, the roof, walls and face of an underground excavation are not immediately stable. Cracked layers, loose fragments and unstable rock blocks may remain in the roof and walls, partially attached to the surrounding rock mass. This creates a risk of uncontrolled detachment and falling material that can injure personnel or damage equipment. Scaling is the mechanical removal of this material before any further work begins in the area. Machines built for this purpose, underground mining scalers, are standard equipment in underground mines that carry out drilling and blasting.

What is scaling and how does it differ from roof bolting

Scaling is the removal of loose, cracked or unstable rock from the roof, walls and face of an excavation, usually carried out right after drilling and blasting. Roof bolting is a different process: it reinforces the rock mass by installing bolts that tie weaker layers to more stable strata. Scaling physically removes the hazard, bolting stabilizes what remains.

In a typical work cycle, scaling is carried out before bolting - hazards are removed first, then the remaining rock mass is stabilized. This sequence can vary depending on a mine's work organization and procedures.

Scaling can be done manually with a scaling bar, but in larger mining operations, dedicated scaling machines are standard. They keep the operator at a safe distance from unsupported rock and reduce the time needed to prepare an excavation for further work.

Why scaling matters for safety

Loose rock detaching and falling is one of the fundamental hazards in underground mining, alongside gas, fire and machine-movement hazards. The risk increases with mining depth: stresses in the rock mass grow, rock structure changes, and the roof and walls are subjected to greater loads.

Systematic scaling:

• removes hazards before people or machines enter the excavation,
• reduces the risk of rock falls,
• creates safe conditions for subsequent bolting and roof support work,
• reduces downtime caused by ground-instability incidents.

The extent of scaling required also depends on the quality of earlier work. Precise drilling and controlled blasting produce a better roof, wall and floor geometry, reducing the number of irregularities and loose rock fragments that must be removed afterward. Scaling is therefore not a process detached from the rest of the mining cycle - its scope depends, among other things, on the accuracy of the preceding drilling and blasting.

How mechanized scaling works

A mining scaler is a self-propelled machine fitted with a hydraulic breaker, a pick, or a rotary cutter head mounted on a boom. The operator guides the tool along cracked or loose sections of rock, breaking the material free so it falls safely to the floor, where it is cleared separately.

Typical sequence of work:

1. Positioning - the machine trams into the excavation and is positioned under the section to be worked on.
2. Condition assessment - the operator assesses the condition of the roof and walls from a safe position, using visibility from the cabin, cameras or other observation systems, and identifies areas requiring scaling.
3. Scaling - the working tool (breaker, pick or cutter head) breaks loose or cracked rock free.
4. Post-scaling check - the treated surface is checked again to confirm the hazard has been removed. On machines fitted with an inspection basket, this can be carried out using the basket, in line with the mine's procedures.
5. The area is then released for further operations such as bolting, shotcreting or production work.

Some scalers have two booms: one working boom (breaker, cutter head) and a second with an inspection basket, allowing the scaling function to be separated from inspection. Remote control is also standard equipment - the operator can control the breaker or cutter head from outside the cabin, using a wireless control panel, while remaining behind a laser barrier that marks out the working zone.

Construction and typical equipment of a mining scaler

A mining scaler combines a self-propelled chassis with a hydraulically operated boom and interchangeable working attachments. Typical design elements include:

• one or two hydraulic booms (working boom and/or boom with inspection basket),
• interchangeable working tool: hydraulic breaker, pick or rotary cutter head, selected according to rock hardness,
• operator's cabin or inspection basket meeting FOPS requirements, protecting against falling material,
• diesel, electric or dual power source, depending on the mine's ventilation and infrastructure,
• remote control of the working tool from outside the cabin,
• depending on configuration: a laser barrier marking out the working zone, cameras, a footage and operating-parameter recorder (a so-called black box), and an interface for collision avoidance system integration.

Types of underground mining scalers

The primary criterion for selecting a scaler is the working tool - chosen according to rock hardness and sensitivity to vibration. A second important criterion is the machine's configuration (number of booms) and reach, matched to the height and width of the excavation.

Mine Master scalers

Mine Master manufactures underground mining scalers for the mechanized removal of loose and cracked rock. Below are details of two models, each dedicated to different rock conditions.

Roof Scaler 2.0SB

A twin-boom machine with a Montabert SC22 hydraulic breaker on the working boom and an inspection basket (meeting FOPS requirements, for two people) on the second boom. Designed for hard rock and low-profile excavations - minimum tramming height is 2.0 m. The breaker can be operated from the cabin or remotely, from a wireless panel, with the operator remaining behind a laser barrier. Diesel power or connection to an electric network.

Depending on mine conditions, both tramming and boom operation can be performed using the diesel engine or an electric network - the choice of power source is not fixed to tramming or working specifically, it depends on the infrastructure available in a given excavation.

Roof Scaler 2.3D

A machine for soft rock, including rock salt and potash, where using a hydraulic breaker would be undesirable due to vibrations affecting the rock structure. Fitted with a rotary cutter head or a pick, selected as needed. Coverage of up to 9.0 m in height, with the ability to work 0.5 m below floor level - allowing scaling of the roof, walls and floor of the excavation. Remote control from outside the cabin via an external panel.

Applications - examples

Safety and design development

Scalers work directly beneath unsupported rock, which is why safety features are an integral part of the design, not an add-on:

• FOPS-certified cabin and basket - protect the operator and inspection personnel from falling material.
• Laser barrier - marks out the working zone during remote operation.
• Remote control of the working tool - the operator runs the breaker or cutter head from outside the cabin.
• Collision avoidance system interface - Mine Master scalers can be connected to any supplier's collision avoidance and overspeed control system already in use at a given mine.
• Cameras and machine data recorder - provide visibility around the machine and record operating parameters for analysis.

The latest Roof Scaler 2.0SB units, delivered in 2026 to a customer in Zimbabwe, are additionally fitted with a lidar system that monitors the danger zone around the working tool. If the system detects a person entering that zone while the machine is operating, it automatically locks out the working functions. This change comes from the client's years of operating experience and illustrates how feedback from the mine shapes later versions of the design.

Choosing a scaler - what to consider

When selecting a scaler for a specific excavation, the key factors are:

• rock hardness and sensitivity to vibration (breaker vs. cutter head),
• excavation height and width (reach, minimum tramming height),
• required scope of work (roof only, or also walls and floor),
• available power infrastructure (diesel, electric network),
• integration requirements with safety systems already used at the mine.

Machine configuration (boom reach, working tool, tramming height, power source, safety package) can be adapted to the geology and organizational requirements of a specific mine. Mine Master delivers both standard models and projects developed jointly with clients and technology partners, such as J.H. Fletcher.

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