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  2. Article: Industrial Screening of Fatty Confectionery: Production to the Limit

Industrial Screening of Fatty Confectionery: Production to the Limit

Rising raw material and energy prices are putting manufacturers of confectionery under greater and greater pressure. High quality and hygiene standards on the one hand and the increasing pressure of costs on the other require a high level of process safety as well as maximally profitable production. An ongoing project by the Ludwigshafen-based screening technology specialist J. Engelsmann AG shows how profitability and productivity can be sustainably increased in the industrial screening of fatty products.

A supplier of ingredients for chocolate and baked goods installed a vibration screening machine to separate out its products: almond and hazelnut meal, nut preparations and chopped almonds. Within a short time, however, recurring problems with the screening performance and the quality of the sieved material had surfaced. The machine’s ball-cleaning system not only damaged the product to be sieved, but was also pushed to its limits when cleaning the mesh. The sieves repeatedly became clogged by the fatty products within relatively short periods of time (roughly every 20–30 minutes), which meant they had to be cleaned very regularly. This was linked to the next problem: the closed design and the stacked sieve decks made the vibration screening machine very difficult to dismantle and clean without significant effort. The resulting long stoppage times even led to supply shortages. The confectionery maker therefore decided to install a different type of screening machine.

As well as protecting the product while screening without detracting from its quality or consistency, the new machine had to ensure the required production quantities with the highest possible level of equipment availability.

Long-stroke screening machine with limit-stop frees up the mesh

Thanks to the implementation of numerous screening technology projects in the confectionery industry, the Engelsmann engineers knew about the problems of screening fatty products. Due to the high throughput and the particularly precise and protective separation (selectivity up to 98%), they settled on using a long-stroke screening machine of the freely swinging type for a machine solution. A performance test under the specified conditions in the company’s own pilot station soon provided the result: a limit-stop screening machine specially designed to the required specifications could solve the existing deficits. The freely swinging screening machine with limit-stop is used everywhere where a ball-cleaning system is pushed to its limits when cleaning the mesh, or where care needs to be taken to avoid damage to the product through abrasion of the balls.

In order to meet client needs, the limit-stop screening machine was constructed with an open design without a cover, with direct access to the sieve deck. Six successively arranged sieve inserts with mesh sizes of 0.1 to 10mm and a total area of 1.5m² ensure continuous screening with a throughput of 1.0 metric tons per hour in four fractions. The sieve trough is mounted on a support frame of square tube and suspended in four low-wear plastic springs. The drive system moves the frame, equipped with push-rods, together with the sieve trough in a horizontal, straight, oscillating motion. The trough follows the frame with a delay, so that it strikes the frame as it oscillates back. To cushion the impact, the frame is equipped with four replaceable plastic limit-stops. The impact on the limit-stop releases product stuck in the mesh and cleans the mesh without leaving residue.

Save cleaning time, increase production time

The open design allows the mesh to be cleaned while screening is in progress without having to switch the machine off. If required, released product remains can be simply swept off the sieve insert with a brush. The sieve trough itself can also be cleaned with minimal effort by using the mounted quick-release clamps to dismantle the sieve inserts arrested by with pressure bars. Cleaning intensity can be configured through the limit-stop system without using tools. The freely oscillating screening system with the sieve trough limit-stop makes it possible to keep the mesh open for almost 60 minutes, double the time that was previously possible. This increases the cleaning intervals and significantly reduces stoppage times. The greater equipment availability allows the client to increase production time and thus achieve a sustainable increase in productivity.

Low-energy use with lower lifecycle costs

To conserve resources when operating the machine, the 850kg limit-stop screening machine is equipped with a specially developed oscillating drive. Driven by an electric motor that transmits its force with a V-belt onto an oscillating mass provided with push-rods, it is exactly matched to the mass of the sieve trough. The drive train (wave and flywheel) weighs about as much as the trough including the product. The motor drives the mass for about 15 seconds with full rated current, and then keeps it oscillating at only 10–20 percent of rated current. The electrical energy is thus converted into rotational energy, stored in the flywheels and gradually released. Thanks to the equal-mass oscillating drive, not only is little energy consumed (0.75 kW for 1.5m²), but oscillations going out of the machine are also largely avoided. Unlike with the use of a motor unit, the oscillating drive is subject to only very little wear, which results in low use of materials and maintenance costs.