Impact huller for grain products

• What was needed: drylin® R Flange bearing; dryspin® Flange threaded nut
• Requirements: the bearings are exposed to abrasive dusts and dirt, and the customer was also looking for a durable, lubrication- and maintenance-free solution
• Industry: foodstuffs
• Success for the customer: high-maintenance recirculating ball bearing guides can be avoided by using drylin® bearings; the new iglidur® A160 material is highly resistant to media, fulfils the strict FDA requirements for hygiene and safety and is self-cleaning; the operating costs for the customer are minimal

Machines for grain are Streckel & Schrader's speciality. Since its foundation, the company has focussed on the design and continuous further development of processes for processing grain and pulses. One of the new developments is the GG1 centrifugal huller. It is used in the food industry to hull oats, spelt, sunflower seeds and similar grain products.
The GG1 centrifugal huller works with the impact method. In this process, the husk of the product is loosened by the impact against an impact body. The machine uses a cylindrical impact ring which the grain hits at the optimum angle and gently separates from the core. An integrated, adjustable quantity dosing system is used to ensure that the product quantity is distributed homogeneously. Ring-shaped wear zones occur on the peeling ring due to the impact of the product. In order to distribute this wear evenly and thus increase the service life of the wear-resistant part, the developers decided in favour of an automatic control system.
Large quantities of abrasive dust and corresponding abrasion are a particular challenge for all components in the peeler, including the bearing. This is because dust and dirt adhere to the bearing, which in practice can lead to poor, rough running and to damage and blockage of the bearing. The recirculating ball bearing guides that were initially used therefore had to be cleaned regularly and re-lubricated and maintained with a lubricating oil approved for the food industry to ensure reliable and smooth running. A new and, above all, maintenance-free solution was therefore required.

In their search for an alternative solution, the design engineers came across our plastic plain bearings. A total of four drylin® R flange bearings are used in the new centrifugal peeler on two drylin® steel shafts. This was the first time in the peeling mill that the use of a recirculating ball bearing guide could be avoided. The bearings are fitted with a plain bearing film made from the tribo-polymer iglidur® A160. The material is highly resistant to media and fulfils the strict FDA requirements for hygiene and safety in the food industry. Thanks to its blue colour, the material is also optically detectable. Integrated channels in the sliding film ensure that the bearing is self-cleaning. Dirt and dust cannot adhere to the bearing. The soft and therefore flexible sliding film also allows for greater manufacturing tolerances. Thanks to the use of base polymers, reinforcing fibres and solid lubricants, the iglidur® sliding elements are not only lubrication-free, but also particularly wear-resistant.
The solutions in the centrifugal peeler also showed a clear improvement in running compared to metallic recirculating ball bearing guides, because the plastic bearings have a larger contact surface and the iglidur® material also absorbs the vibrations. So that the impact ring can be adjusted in height, not only the bearings are used on the shafts. A dryspin® flange threaded nut made of the tribo-polymer iglidur® R also ensures smooth and vibration-damping adjustment on a trapezoidal threaded spindle. iglidur® R has a very low coefficient of friction in dry operation, good abrasion resistance and is very cost-effective. The smooth running is particularly important, as resonances can be transmitted into the housing and thus impair the electronics. In addition, precise adjustment ensures even wear of the skiving ring.

Once the peeling ring is worn, it can be easily replaced without tools, thus reducing machine downtimes. The wear plates, like the bearing, can be easily replaced in a few simple steps once the centrifugal peeler has been used to a high degree. "In terms of maintenance and costs, the new solution is significantly simpler and more economical than previous solutions on the market," says Streckel enthusiastically. To date, 25 GG1 centrifugal peelers are already in use on four continents. The company would also like to rely on the Tribo polymers for future projects in order to save on maintenance and costs.