SKF

Always well lubricated, even under extreme conditions

The process of extracting chalk represents a major challenge for machinery and conveyor systems. Large quantities of dust and dirt create difficult conditions for the machines and, in particular, for their bearings (Fig. 1). Therefore, the bearings need to be lubricated regularly. However, because the conveyors are usually more than a kilometre in length, it is almost impossible to do this manually. For this reason, Verei­nigte Kreidewerke Dammann KG (Fig. 2) chose automatic lubricators from SKF for its plant on the island of Rügen. The lubricators ensure a regular supply of lubricant and prevent premature bearing failure.

Chalk is used for a wide variety of purposes, including as an ingredient of feed and fertiliser in the agricultural industry, a filler in road construction, a filter material in environmental engineering systems, an additive in plastic production and for marking lines on sports pitches. Chalk developed around 70 million years ago from the remains of algae, single-cell organisms and roots. Nowadays, chalk is a sought-after raw material and is extracted at many locations in Europe in particular, including at Klementelvitz on the Baltic island of Rügen. This is home to the ­Rügen chalk quarry, one of three production sites belonging to Vereinigte Kreide­werke Dammann KG. Using the latest technology, the company produces fine chalk, coarse chalk and lime for fertiliser in a variety of grades which are intended for different purposes.

Before the chalk can set out on its journey to customers in industry and agriculture, the slabs of rock have to be extracted from the ground by huge machines. Large rotary drums separate the slabs of chalk from the other rock. Then the chalk is dried and transported away on conveyors. This is not an easy job. Because the chalk itself is fine, the conditions for the machinery are very tough. The huge volume of dust and dirt produced during the process makes monitoring the condition of the machines and maintaining them very difficult.

Lubricating the machines’ bearings is one of the main challenges at a chalk quarry of this kind. For this reason, premature bearing failures often occurred at the Rügen plant. It was simply no longer practical to lubricate the bearings of the very long conveyors on the huge site manually. As a result, the company incurred significant costs and came to the conclusion that a different solution was urgently needed.

First of all, the chalk quarry contacted ­August Kuhfuss Nachf. Ohlendorf GmbH, a company based in Braunschweig, which has a good reputation for selling technical products and also for servicing machinery. Both of the company’s areas of expertise are particularly relevant to the maintenance and lubrication products made by SKF (known as SKF Maintenance Products or MaPro). As Kuhfuss is a “Preferred MaPro Partner” of SKF, its experts have in-depth knowledge of maintenance tasks. This allowed Managing Director M­artin Ohlendorf’s team to come up with a promising solution within a very short time.

“Firstly, we drew a diagram of the entire plant and located the lubrication points. It soon became clear that the only option was an automated lubrication system,” explains Ohlendorf. A total of 480 critical lubrication points were identified by Ohlendorf’s specialists (Fig. 3). The large number meant that only a highly efficient and reliable system would be suitable.

The lubricators from SKF’s LAGD series, which go under the brand name System 24, proved to be the ideal choice. These automatic single-point lubricators consist of a transparent container and a cartridge (Fig. 4) with an electrochemical gas cell. When the lubricator is activated, the internal batteries are connected and the gas pressure builds up until the piston moves, pushing the grease or oil into the component (Fig. 5). The dispensing period can be set to anything between a month and a year. In addition, the lubricators can be fitted without tools. They are also dust-tight and waterproof, are ATEX approved for zone 0 and supply lubrication points automatically with the right quantity of lubricant in a variety of applications.

The specialists from August Kuhfuss Nachf. Ohlendorf GmbH adjusted every individual lubricator to the specific lubrication point. After the precise quantities of lubricant and the materials had been identified, the installation work could begin. Because the lubricators are easy to fit, they could be installed very quickly, despite the large number needed. Within only seven days, the engineers had equipped the entire plant at the Rügen chalk quarry with System 24 lubricators.

The results of their efforts are clear. “There are now hardly any premature bearing failures,” says Martin Ohlendorf. “This means that the number of bearings needing replacement has dropped by around 30 %.” In addition, the new lubricators have significantly reduced the time needed to maintain the many lubrication points. This is partly due to the fact that System 24 allows for a simple visual function check and the quick replacement of the lubricator. Importantly, users can be sure that the content of the lubricator will last until the end of the predefined dispensing period.

Vereinigte Kreidewerke Dammann KG has commissioned Martin Ohlendorf and his team to equip a second site, the chalk quarry in Söhlde in Lower Saxony which has a total of 200 lubrication points, with the SKF lubricators.

www.skf.de

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