A global materials company mines, processes and supplies a wide range of industrial minerals. Among its core products is silica, which is produced at several facilities worldwide, including one in France. The site operates a washing plant that is also used to classify the silica sand according to grain size.

Washing is a standard step in silica sand production. It typically removes clay, silt, dust and other fine contaminants adhering to the quartz grains. This is particularly important for achieving the required chemical and physical specifications. During the process, the silica sand is transported as a slurry from one washing stage, or “bath”, to the next. Each bath is designed to separate the material according to particle size by exploiting differences in the settling behaviour of the silica grains in water. The resulting fractions are subsequently discharged into separate bunkers.

Level measurement in the baths plays an important role in controlling the washing and classification process. The measured level provides the operator with the information needed to control the valves regulating the transfer of silica sand slurry from one washing and classification stage to the next.

The customer had previously used older-generation ultrasonic level transmitters, some with displays and others without. In this application, the instruments were affected by typical challenges associated with ultrasonic level measurement, including temperature fluctuations and condensation. The operator was therefore looking to upgrade the washing plant with state-of-the-art level transmitters that would provide reliable and accurate measurement while remaining cost-effective.

The silica producer selected the OPTIWAVE 1540 level transmitter. This compact and cost-effective 80 GHz radar met all the requirements for a quick and straightforward retrofit. The KROHNE device is designed for continuous, non-contact level measurement of liquids containing solids, such as sand slurry.

More than 15 KROHNE radar level transmitters were installed on top of vertical tubes positioned above the washing stages, replacing the ultrasonic level transmitters previously used in these locations. The OPTIWAVE 1540 radars were set up using the existing infrastructure, including the same cabling and process connections, as well as the 4...20 mA range already configured in the PLC.

Unlike ultrasonic level transmitters, the OPTIWAVE 1540 is independent of temperature fluctuations and insensitive to condensation. Thanks to the highly dynamic signal processing of the 80 GHz radar, it provides a fast response time, enabling accurate and reliable measurement. It was mounted at a distance of approximately 1 m / 3.28 ft from the sand slurry. Its flush-mounted DN40 (~1½") lens antenna and narrow beam angle of just 8° allow it to measure directly towards the medium, avoiding false reflections despite the narrow tubing. In addition, an empty spectrum analysis was carried out to identify and filter out potentially interfering signals.

The OPTIWAVE 1540 features secure Bluetooth^® connectivity and was configured using the OPTICHECK Level Mobile app. The app includes preconfigured, application-specific templates to simplify and speed up radar set-up. Commissioning requires only a few basic application parameters to be entered, such as the 4...20 mA range and the distance to the tank bottom. The integrated simulation mode was used to match the values of the previous sensors, ensuring that the valve relay triggers remained unchanged. This allowed the main settings to be checked with the customer and confirmed that the process, including the PLC scaling, continued to operate as before.

The customer benefits from accurate, reliable and long-term stable level measurement for valve control in the washing process, enabling controlled transfer of sand slurry between the individual stages for consistent classification. The OPTIWAVE 1540 requires no regular maintenance and is unaffected by changing temperatures and condensate formation. Its measurement does not drift over time, eliminating the need for recalibration under normal operating conditions.

Unlike the previously used level transmitters, the KROHNE radars feature Bluetooth^® connectivity and a user-friendly app. This enables convenient commissioning and monitoring, as well as on-site verification – an important benefit for the customer. Separate verification tools and process interruptions are not required.

All KROHNE radars can be checked via the app using a single mobile device. Routine checks can therefore be carried out faster and more safely at the push of a button. With OPTICHECK technology integrated into the device (OPTICHECK technology built-in), the OPTIWAVE 1540 offers a range of diagnostics that continuously monitor device health and process conditions. The diagnostic data are stored in the device and used to generate standard verification reports, which can then be saved in the control room. The entire verification procedure takes just a few minutes.