Mobile concrete spraying units – or shotcrete machines – used in mining are leveraged for the rapid and safe reinforcement of rock in underground adits, mines and tunnels.
Their primary purpose is to stabilise tunnels and shafts by precisely applying shotcrete to the exposed rock. They often operate in confined spaces under extremely rough conditions. High-performance inertial sensors like German specialist ASC’s low-noise accelerometers help optimise the longevity and performance of these specialty vehicles supporting successful mining projects.
Specialty vehicles for underground mining
Unlike truck-mounted concrete pumps used in standard building construction, underground vehicles are significantly lower to the ground, more manoeuvrable (often equipped with articulated chassis) and built to be more robust so they can navigate tight spaces. Typically, concrete spraying units combine an all-terrain carrier vehicle with a flexible, remotely controlled spray arm, a high-performance concrete pump and mechanisms for the application and dosing of setting accelerators. This allows the concrete not only to be pumped, but also to be sprayed in layers onto walls and ceilings.
Before a new specialty vehicle goes into serial production, however, manufacturers rigorously evaluate prototypes through elaborate test series both in the lab and the field. These trials help optimise the dimensioning of components, select appropriate materials and improve damping measures to keep the impact of vibrations to a minimum. This process is vital, as a long service life is of particular importance for machinery and vehicles subjected to high levels of stress. In addition, to meeting customer expectations in terms of performance, quality and longevity, vehicles, equipment and components must be continuously improved and innovated.
The demands placed on these vehicles continue to increase as mining operations become deeper, more automated and more productivity driven. Operators expect maximum machine availability while minimising maintenance requirements and unplanned downtime. As a result, manufacturers place greater emphasis on understanding the dynamic loads acting on the vehicle throughout its entire operating cycle. Detailed vibration analyses during development provide valuable insights that enable engineers to optimise structural design, reduce fatigue on welded joints and mechanical assemblies and improve overall durability before production even begins.
Compact sensors for optimal vehicle tuning
In these nuts-and-bolts testing and innovation cycles, producers of shotcrete machines can rely on the quality of robust yet precise and flexible sensors from ASC.
“The pumping and spraying process induces shocks and vibrations in the structure and chassis of these machines,” says Renate Bay, ASC Sensors general manager. “This gets compounded by the uneven ground, potholes and other obstacles when the carrier vehicle drives to and around the underground mining sites.”
To precisely record and evaluate these impulses in the product development process, triaxial ASC 5511LN accelerometers are installed on the prototype frame and in other places.
The ASC 5511LN accelerometer is based on proven MEMS technology and the capacitive operating principle. It comes with a broad measurement range of 2-400g. The integrated electronic circuitry enables a differential analogue voltage output (±4V FSO) and flexible power supply from 6 to 40VDC. All LN (Low Noise) accelerometers by ASC feature an outstanding signal-to-noise ratio, which is essential for demanding measurements of smallest frequencies and amplitudes in all three degrees of freedom.
An advantage of the compact sensor design is the ability to install accelerometers close to critical components, allowing engineers to capture highly localised vibration signatures. Measurements from multiple sensor locations can then be correlated to create a comprehensive picture of how forces propagate through the vehicle during driving, pumping and spraying. Not only does this data validate simulation models; it also shortens development cycles by enabling targeted design improvements and reducing the need for costly prototype iterations.
“Based on precise measurements, despite the harsh environmental conditions typically prevalent in underground mining sites, the magnitude, duration and direction of forces occurring during the driving, pumping and concrete spraying process can be accurately determined,” says Bay. From that, the medium and long-term effects of these loads on the vehicle and all critical components are calculated. This helps select and verify damping methods and materials, to ensure operational safety of the machine overall and to protect its onboard electronics.
Driving reliability underground
As underground mining projects become increasingly demanding, vehicle manufacturers must balance performance, reliability and cost while meeting ever-higher expectations for machine uptime. High-quality inertial measurement technology provides the data needed to make informed engineering decisions, transforming vibration from an unknown variable into a measurable design parameter.
By accurately characterising real-world operating conditions, ASC’s low-noise accelerometers enable engineers to develop shotcrete machines that are more durable, easier to maintain and better equipped to withstand years of continuous operation in some of the world’s harshest environments. Ultimately, precise vibration measurement is not simply a tool for testing – it is a key enabler for building the next generation of safer, longer-lasting and more productive underground mining equipment.
For more information visit: www.asc-sensors.de
