Outdated technologies often lead to high maintenance costs. A cement plant operator had this problem with its bucket elevators. After analysis by Beumer Customer Support, it was clear that it was not the entire plants that needed to be replaced, but only components. "Right from the start, our three bucket elevators were causing problems," says Frank Baumann, plant manager at a medium-sized cement company in Erwitte near Soest in North Rhine-Westphalia. "We use a central chain bucket elevator as a circulating bucket elevator for the vertical mill and two belt bucket elevators for silo feeding for the production of blast furnace cements," explains Baumann. The central chain bucket elevator on the vertical roller mill was already unusually loud at the start of operation. In addition, chain vibrations were occurring on both sides. Although the original supplier made several improvements, a high level of wear was already apparent after a short period of operation. "We had to have the systems serviced more and more frequently," says the plant manager.

Modernization can pay off

Due to the frequent downtimes on the vertical roller mill bucket elevator, those responsible approached Beumer in 2018. The system provider supplies bucket elevators itself, modernizes them as required and also optimizes existing systems from other suppliers. "For cement plant operators, the question often arises in cases like this as to whether a completely new plant or a possible conversion would be the more economical and expedient measure," explains Marina Papenkort, Area Sales Manager in Customer Support at the Beumer Group. "With our Customer Support, we help our customers to meet future performance and technology requirements as part of modernizations and conversions in a cost-efficient manner," says Papenkort. Typical requirements include increased performance, adaptation to changed process parameters, new materials, optimization of availability and extension of maintenance cycles, maintenance-friendly design and reduced noise levels. In addition, all new developments with regard to Industry 4.0, such as belt monitoring or continuous temperature monitoring, are incorporated into the conversions. Beumer offers everything from a single source, from technical design to on-site assembly.

Cost-effectiveness and availability play a decisive role for customers, as conversions are often an interesting alternative to new construction. In modernization measures, as many components and structures as possible are retained - in many cases including the steel construction. This alone reduces material costs by around 25 percent compared to new construction. In the specific case of the cement manufacturer, the bucket elevator head, the chimneys, the drive unit and the bucket elevator base could be reused. With less assembly work, the downtime is usually also shorter. This enables a faster return on investment compared to a new build.

Heavy duty for coarse-grained material

"We converted the central chain bucket elevator into a high-performance belt bucket elevator type HD (Heavy Duty)," reports Papenkort. As with all Beumer belt bucket elevators, belts with rope-free zones are used to which the buckets are attached. Another important aspect is the belt clamp connection: With all Beumer steel cord belts, the rubber on the steel cord ends is first removed. The technicians split the ends into individual strands in the U-shaped piece of the belt clamp connection, twist them and cast them with white metal. This joint is completely hardened after a very short time and the belt is ready for use.

To ensure stable belt tracking and a long service life, Beumer has replaced the existing drive pulley linings with specially adapted ceramic linings. They are crowned for stable straight running. The maintenance-friendly design makes it possible to replace the individual segments of the shell lining through the inspection flaps. This means that it is no longer necessary to replace the entire drive drum. The shell linings are rubberized - with inserts made of solid ceramic or steel, depending on the conveyed material.

The buckets are adapted to the crowned shape of the drive pulley and lie flat. This increases the service life of the belt. The result is smoother running and less noise. Depending on the intended use, the user receives the buckets in a suitable design, for example with a rubber bottom or made of stainless steel. The proven HD technology scores points with a special bucket connection: an extended back plate, mounted flush, prevents coarse-grained material from penetrating between the bucket and belt. With HD technology, the buckets are provided with tear-resistant forged segments and screws on the back of the belt.

For permanently correct belt tension, Beumer installed an external parallel tensioning device without product contact, which ensures that the tensioning drum can only move in parallel. The tensioning bearing is designed as an internal bearing in a completely encapsulated construction. The bearing housings are filled with oil. The HD technology also includes the maintenance-friendly rod drum with hardened, screwed-in rods. The tensioning drum is designed with a double deflector cone, which reliably prevents damage to the belt caused by jammed bulk materials. "With this modernization, we were able to increase the availability of our vertical roller mill circulating bucket elevator and are significantly more competitive in the long term," says Frank Baumann happily. "Compared to a new investment, we were also able to reduce our costs and we were up and running much faster." Completely satisfied with the conversion, the cement manufacturer also commissioned the optimization of the other two bucket elevators in terms of conveying capacity.

The article appeared in materialfluss 6/22.