Energy supply – protected and flexible

The castle mill in Rochlitz/Saxony has been producing electricity since 1994. For reasons of fish protection, the operator has now invested in the conversion of the inlet to the turbine house and had a new screen installed at the same time. The screen is a cleaning system that removes the floating debris that collects in front of the screen and ensures the water supply to the turbine. After obtaining various offers, the decision was made in favour of a screen system from Erhard Muhr GmbH.
Muhr offers the hydropower plant operator a comprehensive programme of screen cleaners in various types (vertical, horizontal, with different arms ...). The systems are used all over the world and are customised for each individual case. For the project in Rochlitz, Muhr proposed a horizontal rake system from the H-series. The cleaning arm moves horizontally past the screen and pushes the floating debris, which is deliberately left in the river, into the drainage channel. The cleaning arm is attached to a travelling carriage, which is moved by a rack and pinion drive. Propulsion is provided by a direct drive with a 3-kilowatt low-speed motor, which, like the other components, is suitable for underwater operation.
Parallel to the project discussions in Rochlitz, the Muhr engineers developed a new solution for the power supply of the cleaning arm in the H-series. The reason for this was the high installation effort and the festooning system with flat cable that had previously been used. Two power cables and three sensor cables had to be routed to the motor, which is mounted on the cleaning arm. As all standard connection components such as seals and feed-throughs were designed for round cables, connecting the flat cables required a great deal of effort. In addition, the free-hanging cables could become entangled and the resulting cable station required around two metres of space. This prompted the planners to look for an alternative.

Muhr found this alternative in our basic flizz® system. This is a complete solution for supplying energy to moving components in areas such as sewage treatment plants, energy and crane technology. The system consists of an energy chain from our E4.1 modular system, which is filled with the tried-and-tested chainflex® cable and routed safely and smoothly in a weatherproof stainless steel housing. Even when the first basic flizz® was installed on the screen cleaner in Rochlitz, the advantages were obvious. While the fitters on site normally needed a day to install the energy supply system, they were able to complete this task in an hour and a half. And: only 30 centimetres of installation space had to be provided for the "station" of the approximately 15-metre-long movable energy supply system - this not only saves space, but also cable length and therefore copper.
Further advantages from the point of view of the Muhr engineers are the guidance of the energy chain, which is protected on three and a half sides, and the ground-free installation, which prevents the cable from freezing in ice and snow. The basic flizz® is virtually invisible behind the linear drive, but is easily accessible if required. New cables can be added without any problems; it is not necessary to replace the entire cable package as with a festooning system. For these reasons, Muhr now always uses the basic flizz® system for the H-series.
The signal to start the cleaning process is given by two sensors that detect the water level upstream and downstream of the screen. When a defined difference is reached, the system's PLC initiates the cleaning process, which takes just under seven minutes. The situation at the Rochlitz Castle Mill trash rack is monitored by two cameras. This modern technology, together with the long-lasting energy supply system, will contribute to the efficient operation of the hydropower plant for many years to come.