Grading and Sorting Lines for Potatoes, Garlic and Onions

Impianti di lavorazione e selezione patate, aglio e cipolla



Processing lines for potatoes, garlic and onions have specific requirements, therefore it is necessary to study the various stages of processing and identify the best solution according to the needs of the customer.



  1. Product input
  2. Stem removal (garlic and onions only)
  3. Pre-calibration
  4. Washing and brushing
  5. Selection and drying up
  6. Mechanical calibration
  7. Electronic calibration
  8. Packaging

1. Product imput

sistema ingresso carote In the current system regarding the collection of the product are mainly used bins (containers) made of hard plastic with a range that can vary from 400 to 600 kg.

The input of the product in the processing line can take either place in water (A) or on a dry surface (B), in each machine responsible for receiving is possible to install the tilter caissons.

A. Input in water

macchine selezione carote Deschargment of product in water is indicated when the crop is not too dirty and is accompanied by a few small stones. It usually takes place in tanks which depending on the required production may be of different models.
The machine, suitable for procesing a large volume of product, allows, thanks to a device of blowers and pumps, to perform an action of real pre-cleaning. The small stones and debris sink to the bottom of the tank and are vented outside through an auger.
Not being provided transmission organs in movement in the water, nor tapes or carpets for sampling, the risk of breakage is very limited compared to traditional solutions. The product is channeled towards the exit by the movement of water and collected by means of a showel.
The system is particularly suitable for those who have problems with hard debris (such as clay) and a yield of up to 30 t/h.

ingresso in acqua carote Designed for a medium-high quantity of product, this machine is equipped with a conveyor belt with a metal slatband system which permits the advancement and the elevation of the product to the next machine. The small stones and debris sink to the bottom and are vented outside through an auger.
If designed for a low amount of product, is instead equipped with a conveyor belt with a plastic slatband system which permits the advancement and the elevation of the product to the next machine.

B. Input on a dry surface

ingresso a secco carote Emptying the product on a dry surface occurs when the crop is very dirty and is accompanied by small stones. It usually takes place in hoppers that, depending on the required production or type of packaging (crates, boxes, jumbo bags) can be of different models:
The machine is available in different lenghts and therefore for different amounts of material. The product is moved by a conveyor belt driven by lateral chains suitably protected and provided of open sides for the containment of the product.
If the machine was placed in floor it would be possible to unload the product directly inside the dumper truck.

impianto svuotamento secco

The machine is made up of a square shaped support structure made of painted iron equipped with eight-adjustable pedestals which four sides are mounted suitably coated in soft rubber. The bottom is equipped with an anti-clogging system composed of alternately motorized oscillating blades.
It is possible to equip this machine with a filling structure, called zig-zag , which avoids the “abuse” of the product, in this case the filling is carried out through an elevator belt.
The zig-zag is primarily a support structure made of steel to which are suitably fixed rubber straps which allow the sliding of the product on them until it reaches the bottom of the bunker. To facilitate the storage of the product it is possible to mount fans for inside air circulation. In the presence of very unclean product is advisable after this first phase to insert a digger.

sterratore a rulli elicoidali o dischi in gomma

  • Alternated assembly coil spring rollers (Fig. A)
  • Rubber disks (suited for delicate products) (Fig. B)

NOTE: Both solution provides separation between potatoes and grass and/or soil, before it enters the pre-calibration.

2. Stem removal (garlic and onion only)

macchina per sgambatura aglio cipolla It involves a machine which automatically cuts off the top of the stem of the garlic or onion. In the lower part of the machine there is a conveyor belt which takes the cutted stalks out from the machine.

3. Pre-calibration

The pre-calibration pahse for potatoes involves the use of a system composed of rollers and driven by a motor, equipped with a device for adjustment ensuring to work on a wide range of sizes (from 35 mm to 50 mm). The calibrating rollers in addition aside from ensuring the selection of the product, also allow its advancement up to the output chute to another machine.

precalibratura patate
NOTE: It is possible to make de-soiling and pre-calibration in a single machine.

The digging rollers consisting of spirals allow the separation of most of the dirt from the product , while the adjustable calibrating rollers guarantee the elimination of those products considered not suitable because too small (up to a diameter of 50 mm).

4. Washing and brushing

Depending on the type of debris that covers the product, the washing stage may be carried out using two different systems,

precalibratura caroteWhen the product is covered by thick layers of debris like clay (very attached to the crop) the product requires to be soaked in water before is cleanes with the help of brushes, the most suitable machine for this kind of process is the washing machine.
In this machine, thanks to the rotation of the drum and to a special spiral welded inside the drum, the product is washed and it advances to reach the chute output combined with the brushing machine.

lavaggio spazzolatura patate aglio cipolla
NOTE: It is available in different versions accordingly to the amount of processed product.
doppio cestello

It is also equipped with a double drum ( for a processing up to 30 t/h).

precalibratura patate aglio cipollaFor small quantities of product with the same type of debris.

For normal ground product not very dirty is suggested a washing procedure through the use of a washing machine.

This machine has a cylindrical drum, on which is inserted a tube distributor for water. The drum is divided in 3 sectors: a first part constructed with tubes spaced between them to allow the outflow of water and debris in the tank below, a central part completely coated with polyethylene brushes for cleaning the product, and a final part same as the first one. The product enters the drum, advances thanks to the rotation of the cylinder and is brought out via a special slide. Available in two versions depending on the quantity of the product that has to be processed.

5. Drying up and selection

impianti asciugatura patate

In order to dry up the crop is possible to insert in the line a roller carpet with an air duct. In this model is mounted a burner for the heating of the air that is ventilated over the crop  blowing in the opposite direction of the one in which the product is being transported. Regarding the economic consumption that invoves the application of the burner and the remarkable space taken up by the crop in order to dry, in recent years it is preferable to lengthen the end of the brushing machine after the washing machine in order to remove excess water but leaving the potato slightly moist.

Concerning the selection, a visual selection will take place with the help of a rolling carpet. In this pahse, the product advancing on wheels is inspected by operators located on both sides of the bank. The defective product or not suitable for market is removed by operators, while the conforming product goes to the following grading systems.

impianti selezione caroteFor those who wish is possible to insert , in place of the visual selection, a special machine for the automatic selection which does not require the help of personnel. This machine can reach high processing  capacities and the only role of the operator will be to adjust the settings.

6. Mechanical calibration

After the visual selection, the product is selected from the vibrating sizer for a maximum of five gauges.

impianti calibratura patateThis machine is composed of a steel coated structure on which are mounted vibrating structures inside which are fixed rubber networks of different measurements (the smallest knitted or crocheted to the larger ones). The product advances thanks to the vibration, on the surface of the networks and when it passes through the holes and it falls on the tapes below placed in correspondence of each network. A system of motorized levers allows to release any blocked hole in the network.

NOTE: For potatoes with an elonged shape it is better to have a diameter calibration  with an oscillating rollers grader.

calibratura caroteimpianti calibratura caroteThis machine is suitable for the processing of potatoes with a maximum diameter of 125 mm. It is equipped with a mechanical adjuster in order to operate on any diameter and of a rolling carpet that allows the product to spread out evenly. The movable rollers rotate and rise gradually in guides on either side . The product then slides on the tape below only if in the desired size.

7. Electronic Calibration

As an alternative to mechanical calibration, it is possible to perform an electronic calibration that offers the following advantages:

  • Improved accuracy in the weight of the gauges;
  • More flexibility in outputs;
  • Data management;
  • Traceability management.
  • Possibility of internal and external vision of the crop (color, quality internal and external non-invasive control)

8. Packaging

riempitrici di sacchi jumbo

Ex. Filler jumbo bags.
After calibration the product can be conveyed via tapes towards the caissons for storage, towards the benches for manual packaging or directly to the weighing and packaging machines.

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