With 130 employees, Lemke produces over 10,000 tonnes of marzipan, persipan, nougat and hazelnut and almond preparations annually. Its customers are companies in the confectionery industry, which then process these products further. The export share is 30%, whereby the majority is exported to Scandinavia, Poland and Ukraine.
In the past, the almonds were transported to the individual processing machines with pneumatic pressure conveying and conveyor belts. The company's own technology department has developed continuously and implemented several production systems, eventually switching to Mink claw technology for the generation of the vacuum. The first pneumatic conveying system was planned and commissioned in 2006.
The disadvantage of pressure conveying is that rotary feeders had to be attached to the silos to prevent the pipes and/or the silos from becoming blocked. However, the rotary feeders caused a high level of breakage in the almonds. In addition, the conveying speed was too high in pressure conveying, so that more almonds were broken in the pipe corners. From an economic point of view, the energy requirements for generating the necessary compressed air were excessive.
The maintenance of the mechanical conveyor belts was complicated, and they did not form a closed system. As a result, the products came into contact with the environmental air, which was not ideal when it came to hygiene. The engineers in the planning department at Lemke therefore considered how the products could be transported more efficiently and in a closed system.
The initial impressions of the Busch Mink claw vacuum pump, installed to generate the necessary vacuum, were already extremely positive. Thanks to the conveying of the almonds by vacuum, the transportation causes considerably less wear on the materials. Even so, more than twice as much material can be conveyed with a vacuum pump than previously with pressure conveying. Rotary feeders on silos and other containers are no longer necessary.
Therefore, the company has installed a conveying system that transports the almonds hygienically in a closed system and reduces almond breakage. As a result, operating costs have been reduced considerably as there is no longer a need to generate compressed air for pressure conveying and the energy requirement for the rotary feeders has been omitted. Moreover, Mink vacuum pumps provide an extremely high level of efficiency thanks to their non-contact compression, which is reflected in the low power consumption compared to other vacuum pumps.
Following these initial experiences, virtually all the conveying systems at Lemke have been converted to vacuum conveying. There are now twelve Mink vacuum pumps in use on various conveying systems. Given three-shift operation round the clock, the individual conveying systems are in use on average 80% of the time. When a conveying system is switched off, material remains in the pipes thanks to the plug conveying. This has the advantage that material can be provided again immediately when the system is started up again.
For Sven Hell, Managing Director at Lemke, it is important that only identical vacuum pumps are used in his business, and that they can be replaced quickly in the event of a breakdown. He considers the rapid service from Busch, which runs its own service workshop in Berlin as another advantage of using Busch technology.
The most important aspect for Marco Feuer, a project manager at Lemke and responsible for the conveying systems, is the reliability of the Mink vacuum pumps. Since commissioning the first pumps in 2006, there has not been a single fault, let alone a breakdown, in any of the Mink pumps. As well as that, these vacuum pumps are virtually maintenance-free.
It was not until 2010, after four years' running time in a three-shift operation, that maintenance was carried out on the vacuum pumps for the first time. This maintenance consisted of the usual once a year replacement of a filter that is installed directly upstream from each Mink vacuum pump to protect the pumps against the intake of solids.
The low requirement for maintenance and the economical operation of a Mink vacuum pump are linked to its design principle. Mink claw vacuum pumps compress the intake air through two rotors with a claw profile rotating in opposite directions. The claw profiles are shaped so that they intake, compress and then expel the air again with a single rotation. In the process, the claws do not come into contact either with each other or with the cylinder in which they are rotating. There is therefore no friction and so no wear in the interior of the pump.
Moreover, users can dispense with operating fluids such as oil for lubricating or cooling. The claw pair is synchronised by an oil-lubricated gear separated from the compression chamber. This gear oil has to be changed every 20,000 operating hours, which represents an oil-change interval of four to five years given the operating conditions at Lemke.