Rotary sifters from Zeppelin Systems Plant Engineering have been tried and tested over many years in the processing of powdery bulk material. They are used as protective screens behind silos, downstream from bag filling stations and containers, and as inline sifters. To further enhance food safety, the sifters have now undergone another revision with a particular focus on hygienic design.
Rotary sifters are used in many applications, including protecting downstream components, loosening agglomerates and controlling sifted material. The strengths of RS rotary sifters (RS 3 or RS 7, for a rated power of three or seven metric tons per hour) from Zeppelin Systems are particularly evident in the food industry. This compact machine is not only suitable for a wide range of flours, but also for processing tea, dextrose, cocoa, starch, milk and egg powder. It has also proven a highly valued and reliable partner in the plastics industry over many years, for example in the processing of PVC powders or chalk.
Rotary sifters are generally designed for high throughput and a long service life. This is ensured by the balanced drive shaft, which together with the robust, low-vibration housing design guarantees quiet, low-wear operation. In addition, the feed screw and hammer plates are mounted on both sides. Among other elements, the hammer plates are also bolted or welded to the drive shaft, depending on the machine generation. In the event of damage to the hammer plates or the pre-screen, the shaft can still be repaired without the entire shaft needing to be replaced. Each machine comes with a sealing gas unit as standard. Coarse material collection containers can be equipped with a fill level sensor.
How does it work exactly?
Sifters have an integrated screw conveyor which feeds the product into the screen through the inlet housing. The fitted motor drives the feed screw, pre-screen and hammer plates. The screw carries the product into the sifter drum. There, rotating paddles in the chamber accelerate its motion and swirl the product through the screen. The high speed throws the product particles against the screen fabric, increasing the chances of the fine material passing through the screen. Rotary sifters have a sifter drum, which can be made of stainless steel or plastic. If a plastic sifter drum is used, it is advisable to use a stainless steel pre-screen as this protects the sifter drum against coarse and large contaminants and possible damage. In addition, this distributes the product more evenly on the screen cylinder, which in turn extends the sifter’s service life.
Zeppelin Systems has optimized: Dust deposit minimization
The rotary sifter has now undergone a thorough overhaul, with the emphasis on hygiene aspects. The redesigned housing and frame are immediately striking. The support frame is now equipped with a round tube instead of the previous square version, meaning there is little chance of dust accumulation – and if dust does accumulate, it is easy to remove. Zeppelin Systems has also done without the external reinforcement ribs on the fine material hopper. The number of screws in the process area has generally been reduced. The remaining screws in the product area are secured against loss with Loctite threadlockers.
A new standard: Stainless steel inlet housing
In addition, the sifters are now only supplied with stainless steel inlet housing as standard. This is key for the food industry, as this sector tends to avoid aluminum due to suspected health hazards. The support frame has also been optimized such that the rotary feeder can be connected to the fine material hopper. A transparent container with quick-release fasteners ensures dust-free removal of coarse material, further enhancing cleanliness in the workplace.
During operation, the sifter impresses with its short cleaning times and quick and straightforward screen replacement, while the sifter drum also enables fast and easy cleaning. There is the option of installing a pneumatic blower to achieve and maintain cleanliness on the top of the main screen – this reduces product deposits and facilitates maintenance, as the screen can also be easily changed or replaced here without significant product accumulation.
A variety of measures guarantee safety
The wide range of sifter drum variants in different materials, with different mesh and slit widths or perforation diameters, offers a very high level of flexibility. A plastic screen, perforated plate (with round or square perforations) or stainless steel slit screens are used, for example, depending on the requirements and industry.
Plastic sifter drums are subject to natural wear, and over time this can cause the screen fabric to tear – whether due to fatigue or exposure to sharp-edged coarse material. Holes in the fabric can cause coarse material and foreign objects to enter the bulk material.
A tear in a plastic screen is easily detected and affected batches can be identified and rejected at an early stage, meaning that this version is of particular interest to companies with hygiene-sensitive products. Replacing a polymer screen with a stainless steel one is straightforward, even on older sifter models.
For detection of possible tears in polymer screens, there is the option of equipping the sifter with an automatic sifter drum monitoring system (Screen-D-Tect®). This continuously monitors the condition of the conductive screen fabric during operation. To achieve this, the longitudinal threads of the fabric are coated with carbon so that the fabric can be monitored based on the electrical resistance of the sifter drum. If there is a tear in the screen, this resistance changes abruptly, enabling the product to be immediately blocked. If visual inspections are performed on a daily basis, an entire day’s batch would have to be blocked instead.
Detect fragments immediately
Zeppelin Systems also offers a new, blue-colored screen fabric, which enables immediate detection of filter fragments in the sifted material. This enhances operational and product safety, as abrasion or wear can also be reliably and quickly detected. In addition, a magnetically detectable version made of ferritic stainless steel is available as an option for stainless steel drums.
The sifter drum itself can also be easily inspected via the lateral inspection opening, while safety switches installed on the maintenance door and inspection cover deliver optimum safety for the operator and system. The rotary sifter is of course also available in a version compliant with ATEX Directive 2014/34/EU.
Reliable and safe production of kosher products?
Zeppelin Systems creates solutions!
Thanks to a very high degree of protective screening against insects/insect parts, rotary sifters from Zeppelin Systems offer a new level of safety in the production of kosher and halal products. This is proven by studies conducted jointly by the American Institute of Baking (AIB), Zeppelin Systems, and customers. During these studies, various batches were examined in which foreign material was mixed into the sifted material. The foreign material varied in type (e.g. glass, paper, plastic, stones or hair), size (e.g. starting at a thickness of 1 mm) and shape (oval, round, etc.). In a further series of tests, insects (e.g. tribolium confusum – flour beetles) were placed into to the supplied material. All tests were carried out on the RS7 rotary sifter in the in-house test facility at the Rödermark site. The sifted flour and flour from the inside of the screen were then sifted by hand and analyzed. Each test was repeated three times. The results were clear: The sifting result was so clean that the rotary sifter from Zeppelin Systems sailed through the tests, more than meeting the AIB’s strict quality requirements! We Create Solutions!
Conclusion: The completely overhauled rotary sifters from Zeppelin Systems not only ensure excellent productivity, but also safety in the food industry. Alongside the new design and easy-to-clean sifter drum, warning concepts for torn screens such as the new blue sifter fabric or proven Screen-D-Tect® also guarantee high-quality products.
