The extraction of chalk presents a challenge for machines and conveyors: large quantities of dust and dirt make their life difficult, especially for the bearings (Fig. 1). Therefore these have to be regularly lubricated, which in the case of kilometre-long conveyors, however, is not possible manually. For this reason, at its plant on the German island of Rügen, the Vereinigte Kreidewerke Dammann KG relies on automatic lubricant dispensers from SKF (Fig. 2). These ensure a regular supply of lubricant and therefore prevent premature failure of the bearings.
The chalk was formed a good 70 mill. years ago from the residues of algae, protozoa and roots. Today chalk is a sought-after raw material and extracted especially in Europe at numerous sites – including at Klementelvitz on the island of Rügen in the Baltic Sea. Here is the Rügen Chalk Works, one of three production sites owned by Vereinigte Kreidewerke Dammann KG. The company employs modern technology to produce fine, coarse and fertilizer chalks in different qualities, which are specifically processed for different applications.
Before the chalk can embark on its journey to customers in industry and agriculture, first the huge slabs have to be broken out of the interior of the earth by huge machines. Large rotary trommels separate the chalk slabs from other rocks. The material is then dried and transported further on belt conveyors. This is not an easy undertaking, then as fine as the chalk itself is, the tougher the working conditions are for the machines. The enormous volumes of dust and dirt produced make condition monitoring and maintenance very difficult.
Especially for lubrication of the machine bearings, the Chalk Works is a really tough job. In the past, premature failure of the bearings frequently occurred on account of a lack of lubricant. Manual relubrication of the kilometre-long conveyors was simply impossible on the vast operating site. Huge additional costs were the result as well as the realization that another solution was urgently needed.
First contact for the Chalk Works was the contract partner of SKF for Maintenance Products (Mapro), the company August Kuhfuss Nachf. Ohlendorf GmbH based in Braunschweig. The team around Managing Director Martin Ohlendorf (Mapro contract dealer) was quickly able to come up with a promising solution: “First we sketched the entire operation and determined the necessary lubricating points. Then it quickly became clear that only an automatic system could remedy the situation,” explains Ohlendorf. A total of 480 points were identified by the experts – quite a high number (Fig. 3).
The LAGD series lubricators developed by SKF, which are sold under the brand name System 24, were proven to be particularly suitable. The automatic single-point lubricators consist of a transparent reservoir (Fig. 4) and a cartridge containing an electrochemical gas cell. Once the internal batteries are activated, gas pressure is generated and the piston in the lubricator pushes the grease or oil into the application (Fig. 5). The dispensing period can be adjusted from one month to one year, and installation is possible without any tools. The lubricators are also dust-tight, water-proof and ATEX-approved for zone 0 and ensure in many applications that the lubrication points are supplied fully automatically with the correct amount of lubricant.
The specialists from August Kuhfuss Nachf. Ohlendorf adjusted each and every lubricator to the specific lubricating point. Following exact setting of the lubrication rate and the materials used, installation could begin. Thanks to the easy installation, this was quickly completed despite the high number of lubricating points. After just seven days, the complete operation at Rügen Chalk Works had been fitted with System 24. The result is impressive: “The bearings failures have been reduced by almost 30 % since then – and we have registered hardly any premature failures,” Martin Ohlendorf sums up.
The time required for maintenance is much shorter thanks to the new devices. System 24 enables simple visual functional control as well as fast replacement of the lubricator. In addition, it is guaranteed that content is sufficient at the set point in time. In the meantime, the company’s second site, the chalk plant in Söhlde, Lower Saxony, has also been equipped with SKF lubricators.