Running continuously for 24/7 or standing idle for months on end, these are the two extreme conditions with which the world's longest plastic energy chain operates. At the lignite-fired power station in Tušimice, Czech Republic, the roller energy chain system with a travel length of 615m has been achieving this for ten years now without missing a beat.
In normal operation, lignite (brown coal) is extracted from the opencast mine and conveyed directly into the power station. However, if coal production is interrupted for any reason, supplies must continue to keep generating energy. The operators of the power station, the ČEZ Group, do this by stockpiling large quantities of coal nearby.
At Tušimice the coal is stored in a long heap on the periphery of the power plant site, which theoretically could be used to fuel the power station for a full week. To pile the coal automatically on the heap, a 'stacker' is used. To supply the stacker with energy, data and media, the ČEZ Group opted for an energy chain system from igus.
The project was managed by Hennlich, a stocking distributor for igus based in the Czech Republic. At the Tušimice power station the 5050RHD energy chain is used. The 'R' in the name stands for 'rollers'.
“By using a roller, the coefficient of friction on long travels drops dramatically, when the upper run of the chain runs on the lower run,” explained Frank Schlögel, Head of Engineering Projects at igus. "Because of the lower friction, up to 57% of the required drive energy can be saved. Which, of course, is all the more important on record-breaking travels like this one."
With his project engineering team, Frank Schlögel supervises special projects around the globe and accompanies customers closely along every step. From the first design and detailed planning stages up to installation and even maintenance.
Before the igus energy chain system was installed at Tušimice, a cable drum was used. During the cold Czech winter, the cables froze up time and again, which could result in failures and unplanned shutdowns. These problems have been a thing of the past for ten last years.
Working with Hennlich, igus developed a complete package for the application. Since then, only regular visual inspections have been carried out. Over the entire period, just ten crossbars have been replaced, a job done in a few seconds, not counting the inspection walk along the 615m travel.
In addition to this energy chain system, two more systems are installed at this site - one is a 400m travel, the other is 150m. The two systems supply the 'reclaimer', which removes the coal from the pile and transfers it to the conveyor belt that runs to the power plant.
Inside the energy chains are various chainflex cables from igus, which have been developed specifically for use in energy chains. In addition to the chainflex motor and control cables, a fibre optic cable is used for data transmission.
“Bus cables are out of the question for these long travels, as the signal strength would be degrade too much," said Frank Schlögel. A water hose is also routed in the chain together with a heating cable that prevents the water from freezing inside the hose. The water hose is needed for the sprayer at the end of the stacker. When the coal is mined and piled up onto the heap, there is a lot of dust. This is counteracted by continuous spraying.
Since commissioning, electronic monitoring has been carried out on the energy chain systems in Tušimice. By measuring the push/pull forces of the chains continuously, if the forces become too high, the system can be shutdown automatically. This can happen when debris enters the system, for example.
In recent years, igus has further developed this form of 'condition monitoring', or isense as it is known and today offers machine builders modules for monitoring and predictive maintenance as an additional safeguard. Under the 'smart plastics' range, this includes break (isense EC.B) and push/pull (isense EC.P) monitoring modules. In the event of a chain break, the system can be switched off, so that further damage is avoided.
To complement this the abrasion monitoring module (isense EC.W), measures the wear of the energy chain continuously to provide a reliable indication of the remaining service life of the system. This enables a planned replacement of the system without sudden failures.
Admittedly, the stacker moves only at a moderate speed. About 20 minutes are needed to cover the 600m. And every now and then the system is not used for a whole month. But when the time comes and the coal needs to be conveyed to the heap or needed from there, the operator can trust that the system will work reliably with the igus energy chains regardless of the season. Even in these harsh conditions and after more than ten years.