PETKUS Gravity Table G40 - The next Generation


Founded in 1852 PETKUS was the first company worldwide to specialize in the design and production of seed sorting and cleaning machines. The focus on continuous improvement and development throughout the changing decades has led to its standing as a traditional and reputable force in Thuringia. After two years of research and in cooperation with scientists PETKUS has landed a coup with its new Gravity Table G40. The objective of the new design was to achieve the best possible separation effect and a cleaning efficiency of nearly 100%. To achieve this goal, research was conducted with state-of-the-art fluid mechanics simulation tools.

Sorting by weight

PETKUS gravity tables are applied where product of different weights need to be separated and are usually utilized as last process step in grain and seed processing plants. Their main task is to separate diseased grains, fractional parts or debris from the good / healthy grains. Due to the different specific weight of the individual grains, the sorting can be performed easily. The new PETKUS Gravity Table G40 is characterized by an almost 100% pure sorting result in grain and seed. This has a positive effect on two important aspects: the efficiency in the seed business and in terms of healthy grain in the food industry.
With the new Petkus Gravity G40, the mechanical selection already begins in the front section – shortly after filling. The adjustment of the flags or fins directs the material to be sorted already when fed into the inlet zone. The so-defined direction of the grain movement makes a mechanical separation and an increased flow rate possible from the start. The fins and the unique secondary zone ensure a high sorting efficiency and separation effect.
Also important for an optimal separation result is the height of the product layer on the sorting table. The vibrating table surface of the gravity table must be filled continuously and consistently, so that the surface is always completely covered. This is achieved by setting the flaps at the outlet.
Besides the mechanical separation the vibration of the working surface and the resulting micro throws perform an additional separation. The newly developed secondary zone ensures that the poor (light) grains do not reenter the main separation zone. This way the clearly defined separation zones can already be seen on the sorting table.
The length of the gravity table has been exactly calculated so that the heavy grains – the good ones – have enough time to separate themselves from the bad. The setting of the table has an enormous impact on the performance respective the quality of the goods to be separated. The longitudinal inclination determines the performance of the sorter, while the lateral inclination is responsible for the quality of sorting.

Optimizing the air distribution

PETKUS developers and designers have improved the air distribution so that an optimal ratio between levitation force and gravity arises. Equipped with a new aerodynamic system that not only increases the performance but also the precision of the separation. Due to the new design of the fan and the table surface a laminar and therefore a consistent air flow is produced, whose speed and pressure is consistent at every point of the table surface. 
The PETKUS Gravity Table G40 is equipped with three high-performance fans, each of which is responsible for an individual zone: input, sorting and exit. At the input the air flow is precisely controlled by an innovative iris – similar to a camera – and is the key controller for each individual fan. A new type of sieve diffuser on the fans ensures a homogeneous air distribution. Modified perforated plates optimize the air speed profiles within the three separation zones.

Installation and Ease of Operation

A key optimizing factor was the reduction of the frame’s vibration. For this purpose it was necessary to reduce the forces acting at the foundation to achieve a complete mass balance. This was done by decoupling the air distributor box from the machine frame. The new PETKUS Gravity Table G40 is characterized by a very smooth, almost vibration-free operation and as such it does not require a large foundation for the installation.
The completely electrically controlled inclination adjustment contributes to a significant operation. A large number of setting parameters can be stored on the touch panel to allow for faster adaption when changing products.
Accessibility and serviceability were also seen as key development factors. The cover can be easily opened by means of gas springs and because of the open structure there is limited adherence of dust and light materials. The reduced cleaning effort therefore allows for a longer run time.