Holcim relies on drive technology from NORD Drivesystems

Holcim Ltd, with its headquarters in Switzerland, is one of the largest construction material producers worldwide with around 80,000 employees and production facilities in about 70 countries. Its products include additives of different aggregates along with cement, gravel and concrete. For a good 10 years, the corporation has been represented in Croatia with six concrete factories, a cement plant and three quarry systems. From the beginning, Holcim Croatia has mostly used drive solutions from NORD Drivesystems for the belt conveyor systems used in these facilities.

At the Sumber and Ocura quarries in Croatia, large stones are removed through explosions, transported through conveyor belts between the working floors and bunkers to the preparation facility, then crushed in stone crushers and graded to maximum grain sizes 3.3, 8.8, 16 and 32 mm. After this, they are transported to the storage site through conveyor equipment. Different technologies are available for the transportation of the various materials, which each have their own challenges. The conveyor belts that transport the larger rocks must overcome inclines of up to 25° and minerals up to 250 μm in size are conveyed with bucket elevators. Fixed on a double or central chain, a sprocket chain or on a belt, large cup-shaped containers made of steel or plastic are continually loaded with material.

Screw conveyors are also used, with a helical screw running in a trough to transport the goods over several metres. Gravity and friction of the transported material on the trough walls make sure that the material does not rotate with the conveyor screw, but rather is continually transported longitudinally. If the friction on the wall is small with a high degree of filling, the material will only rotate at right angles to the screw axis and is not transported. Thus, with a vertical transport, wall friction must be created through centrifugal force, which requires high rotations in the order of 250 to 400 rpm. The conveyed material can then be transported horizontally, inclined at an angle or moved vertically. All of this conveyor equipment is powered by NORD drive systems.

“We value the drive technology from NORD due to its high reliability and efficiency. Service and delivery availability are also the best. For good reason, we have been operating NORD products in our quarries for more than 10 years without experiencing problems,” said Nenad Mackic, facility manager in the Sumber quarry.

Variable-speed geared motors with frequency inverters are used for the small bucket elevators, while unregulated single-speed geared motors provide the higher performance required for larger systems. Because of the mass to be transported, gentle startup via a fluid coupling is essential, while a back stop prevents the conveyor equipment from running backwards. With an efficiency of about 95%, the gear units are available in shaft-, foot- or flange-mounted versions to suit the application. The maximum capacity is up to 200 kW with a maximum torque of 50,000 Nm.

In the Holcim cement plant in Koromacno on the coast of Istria, NORD geared motors have also been used for more than 10 years. The plant produces an average of around 500,000 t of cement per year; the maximum capacity is up to 750,000 t. Cement is produced according to a continual drying process, primarily using natural resources. The raw materials (normally limestone, clay, sand and iron ore) are mined in quarries, and after the extraction, a crusher mills the raw materials. In the cement plant, all raw materials are crushed and simultaneously dried together in a mill. The raw material resulting from this process is then fired into clinker in a kiln at temperatures of about 1450°C and then cooled to 200°C. The clinker is then crushed in a mill together with gypsum or anhydrite, yielding the finished cement product.

NORD drive solutions are used for all transportation and conveyor tasks in cement production. Some of the drives are designed for operation in explosive environments according to ATEX Zone 21 or 22. Primarily, mid-sized geared motors are used: helical, parallel and bevel geared motors up to 45 kW, mostly with protection class IP55, depending on the respective task.

Robert Tencic, head of purchasing, and Teodor Gobo, head of maintenance, of Holcim Croatia are very happy with the performance of the NORD products.

“We particularly value the high delivery availability and reliability, the very good price-performance ratio, the good service and the unique quality of the NORD products,” they said.

This is reason enough for Holcim to sign a three-year-contract, which says that Holcim will exchange older gear motors - independent of the brand - with NORD drive solutions in all factories in Romania, Bulgaria, Hungary, the Czech Republic, Slovakia and the countries of the former Yugoslavia.