The quarry's operator Ernst Krebs in the far north between Hamburg and Kiel is very diversified. Owner Caren Krebs and her son André operate several gravel quarries, and the company portfolio includes demolition and recycling work, earthwork, road-building and also a transport and logistics section.
The company's machinery was to be extended in 2021 by a new screening plant. The requirements included that the plant had to be flexible, above all, and perform in the gravel quarry just as well as on the recycling site – which is not an easy task. Whereas sand and fine-grained material are processed in the gravel quarry, in the recycling of rubble and railway ballast Krebs processes almost everything. This includes topsoil which is often particularly cohesive. The screening plant therefore has to deal with stone material ranging from very fine to very coarse as well as with all degrees of contamination.
André Krebs took his request to his contact partner at Wirtgen Germany, Henning Lüdtke, with whom he has been working together from many years. After hearing the task description, it was clear to Lüdtke that this would be the ideal application area for Kleemann's new MOBISCREEN MSS 802i EVO which is designed for high flexibility and productivity.
The machine was not yet available on the German market, but Lüdtke found an unconventional solution. He offered André Krebs a pilot series model of the plant for coarse materials, an offer that Krebs accepted.
"Even though it was bit like buying a pig in a poke," said Krebs. "There were hardly any documents on the product." Over the years, however, Kleemann had build up a really high level of trust at the company: "In our gravel quarries and in recycling we have already been using Kleemann machines for a long time with real conviction. I was therefore fully confident that this machine would also do a good job. And based on the description from Henning Lüdtke I knew: this is exactly the machine that we need here."
Krebs was not disappointed: "It's simply obvious here that Development once again looked exactly at what makes work more effective in practice. Everything is so much quicker, set-up times are shorter and output is higher."
The flexibility begins with the large feed hopper. The hopper rear wall and the filling aids can be folded variably so that loading from different heights, from both sides and from the rear can proceed in an optimum manner. The screen surface change is comparatively easy even in the lower deck because the screen casing can be placed completely in horizontal position. The screening parameters can be adjusted precisely and even conversion, for example from three to two final grain sizes, is uncomplicated.
Transport from one work site to another is fast: the discharge conveyors can be folded in – without the disassembly of parts. The stepless driving control means the plant can also be moved precisely into position.
From a safety point of view, with the MOBISCREEN MSS 802i EVO all relevant functions can be operated from a safe distance.
"Everything is set up practically and logically," said Krebs. "For example, the display can be plugged in at different points on the machine. The user is always near the function currently being executed – a real advantage."
The blind operation of levers arranged remotely from the component to be folded is a thing of the past. Apart from the increased safety, this also simplifies operation during set-up and service. The numerous well-through-out details all add up to make the plant user-friendly and thus safer.
After a few months of practical testing, the screen for coarse elements was able to demonstrate its qualities. Krebs says that one of the real challenges for his company's operation is gravel extraction.
"We have to deal with a lot of sand with a relatively small proportion of stone," he adds. "This means that the side discharge conveyor for fine grain has a real tough job. Other screening plants would soon reach their limits. This is no problem for the new plant," André Krebs is glad to say.
Kleemann says that the screen casing can be set over 20% steeper than many other screens for coarse elements on the market, and this guarantees a great cutting effect for the separation of fine material such as sand and a significantly higher output.
The company says: "All in all, the entrepreneur is completely satisfied with the new acquisition, and has already ordered a further plant."