Flexible metering technology was sought by a large energy supply company in the U.K. for its northern hydropower dam. Improved equipment was needed for a wood chip system recently installed to curb pollution in the dam. Accumulated wood chips are transported to a designated storage area via a series of chain conveyors that require robust measurement technology, including an indicator that functions as a full detector in the transfer chutes in order to quickly detect a blockage with the wood chips.

Together with the subsidiary UWT (UK) Ltd in Shrewsbury, a safe solution was found after several tests with oscillating probes that work according to the vibration principle. The Mononivo MN 4020 with tube extension was installed in the transfer chutes to reliably detect wood chips. The bulk density of the chips is 450 g/l, process temperature is up to 80° C (176° F) and process pressure is around 0.8 bar (11.6 psi). Source: UWT GmbHCorrosion is relatively severe and required a detector with a high surface quality. With the adjustable sensitivity and the small 1 inch connection threads, the stainless steel single rod probe could be perfectly configured to the application. Optimal for use in wood chips and wood shavings is the fact that, due to the design, no material can accumulate on the sensor arm, which prevents faulty switching in the long term.

The vibrating rod is stimulated to vibrate by piezo elements. Material in contact stops the vibration, causing a change in voltage in the piezo elements that is registered electronically. The vibration also provides some self-cleaning of the level probe.

With the installation of the corrosion-resistant min/max detectors, the process flows in the hydroelectric power plant could be optimized quickly and easily in terms of overfill protection of the wood chip system.