Feed-hopper level measurement in a cone crusher

A family-owned French company specialises in quarry operations, public works, and materials recycling. Its activities include several alluvial and hard-rock quarries, mobile crushing services, pipeline networks, earthworks, demolition, and the road transport of aggregates. One of the company’s largest plants is located near the Rhône River in the Auvergne-Rhône-Alpes region.

The operator mines alluvial deposits – a mix of sand, gravel, and other river sediments – to produce construction aggregates. The extracted material from the quarry is transported via conveyor belts to the adjacent processing plant, where it is crushed, washed, and processed into rolled sand, road gravel, pebbles, or concrete aggregates. To efficiently reduce the extracted material to the consistent sizes required for construction aggregates, the operator uses a cone crusher. This type of crusher can effectively handle hard, mixed-size material and typically produces finer particles, as the material remains in the crushing chamber for a longer period and is successively reduced to smaller sizes.

Crusher overload or insufficient size reduction due to inappropriate fill levels can directly lead to tremendous spikes in power consumption. Maintaining a constant fill level in the crushing chamber is therefore not only essential to prevent performance issues, inconsistent product sizes, and uneconomically low throughput, but also serves as a key lever for improving the overall energy efficiency of the plant. Accurate level measurement is crucial to keeping energy consumption in the crushing process as low as possible and to minimising the plant’s operational expenditure (OPEX), thereby reducing its long-term carbon footprint.

With this in mind, the quarry operator decided to upgrade the plant to obtain additional information on the crusher feed hopper level and optimise the crushing process on a daily basis. The company was therefore searching for a cost-effective, state-of-the-art level transmitter for cone crusher monitoring. The new instrumentation needed to withstand high vibration and dusty conditions while responding quickly to changing level conditions inside the cone crusher.

KROHNE recommended using the OPTIWAVE 1530 radar level transmitter. The compact 80 GHz radar is dedicated to level measurement in a wide range of mining applications – from crushers and conveyor belts to stockpiles and silos. The cost-effective device features a robust PVDF housing with a front-flush DN70 / 3" antenna design. Its narrow 4° beam angle allows the radar signal to penetrate right into the confined installation space of the feed hopper without false reflections affecting measurement performance. The narrow beam angle makes additional settings, such as the “empty spectrum function” – which is normally used to compensate for potential disturbances caused by obstacles or the feed hopper walls – unnecessary.

Thanks to its high signal dynamics, the radar measures reliably in dusty and vibrating environments. The OPTIWAVE 1530 was installed at a short distance to the feed hopper, directly above the cone crusher, using a mounting bracket supplied by KROHNE from a single source. Commissioning was carried out via Bluetooth^® using the OPTICHECK Level Mobile app on a mobile device. The app, available in multiple languages, includes a configuration assistant with preconfigured templates for a wide range of applications, including crushers. This enabled the operator to set up the device independently, without expert knowledge, by entering only a few parameters such as the measuring distance to the bottom and the measuring range.

The 80 GHz radar also features OPTICHECK technology built-in diagnostics, enabling wireless device verification and health monitoring via a Bluetooth^® connection from a distance. A verification report can be generated at the push of a button when required.

The customer benefits from optimal crusher control and consistent size reduction at maximum throughput. The radar enables the operator to continuously monitor the crusher’s condition and performance, ensuring plant efficiency and contributing to a long-term reduction in the crusher’s power consumption. The OPTIWAVE 1530 enables fast response times in the event of overfilling or underfeeding.

The radar level transmitter delivers long-term stable readings in the demanding environment of a crusher and has proven to be a cost-effective, accurate, and reliable alternative to ultrasonic level transmitters. Unlike ultrasonic sensors, the KROHNE radar is unaffected by dust build-up and operates drift-free, eliminating the need for recalibration. Furthermore, the 80 GHz radar is fully potted, providing robust protection for its electronics against vibration and dust ingress.