Size grading

Roller size grader

With the Limas Roller size grader, a flow of potatoes can be divided at any required size. Furthermore, the flow of potatoes can be split up into as many fractions as required.

Principle of grading: The main feature of the grader is its unique rollers. These have a spiral thread that increases in both pitch and depth along the length of the rollers.

Rollers with spirals are arranged alongside each other and synchronised so that the spirals form a square hole between them. This hole becomes larger as it progresses along the rollers. At some point along the rollers, this square hole will be large enough for a particular potato size to fall through.

It is also possible to place a dividing profile between the rollers so that the grading holes become triangular instead of square. The triangular shaped openings give a more regular grading, with respect to weight, if the potato sample has a mixture of round and oval potatoes.

Method of Operation: Potatoes are fed by a conveyor, elevator etc. onto a distributing/equalising table at the beginning of the grader. This guides the potatoes to the grading area between the rollers in an even flow. Each potato is carried along by the spiral until the hole below it is large enough for it to fall through.

Potatoes also turn vertically lengthways into the holes so that they are graded on their diameter. Dividers are placed below the rollers to collect the sizes between the points required. The position of these can be adjusted along the rollers to easily set/change the size ranges collected.

The grader has several advantages over current grading technology:

  • Very gentle to the product.
  • Easy to clean and maintain.
  • Available for different potato sizes and with different numbers of rollers depending of the capacity.
  • Extremely accurate due to the continuously varying size of the grading hole
  • Simple to adjust the grading sizes, even minor changes while running in production.