A calcium-silicate brick and aerated concrete products supplier has installed a level radar measuring system in a 15m high silo containing Perlite, used to make dry lining boards.

Leading calcium-silicate brick and aerated concrete products supplier, Xella, has installed a Krohne Optiflex TDR level radar at its factory in Germany. The instrument was chosen because of its ability to deliver accurate, reliable measurement despite the extremely low dielectric constant of the substance being measured. Xella has installed the Optiflex in a 15 m high silo containing Perlite, an ultra-light powder used in the manufacture of dry lining boards.

The substance is virtually non-conductive with a dielectric constant of just 1.16 - conventional two-wire TDR level meters typically only measure to a dielectric of 1.5.

The Optiflex incorporates a special feature, called tank bottom following mode (TBF).

Rather than using a signal reflected from the material's surface to provide level measurement, this mode detects a return signal emitted from the end of the probe.

Where materials have poor surface reflective properties the level radar is able to 'see through' the product to determine the position of the end of the probe.

Through using this mode the instrument can calculate the precise level of the material from the time taken to detect the signal emitted from the probe.

Because the transit time of the pulse will depend on the dielectric constant of the material, where this is known and programmed into the Optiflex, the instrument is able to accurately calculate the surface level of virtually any material.

When set to automatic mode the Optiflex will switch from standard direct measurement mode to TBF mode, therefore always selecting the best mode of operation depending on the material conditions.

The Optiflex has high signal dynamics and emits sharper pulses that enable it to detect and measure very thin surfaces.

The instrument can also accurately detect level in applications where the surface of the material is agitated or where foam or dust coat the surface.

The Optiflex is available with a range of five measuring probes, from 4m to 35m in length, that make it suitable for use across a broad range of applications.

The instrument is straight-forward to install.

Once the Optiflex has been fitted to the tank and switched on a set-up wizard takes over.

This initiates a self test routine that takes the operator through a series of questions to define the tank and the substance to be measured.