22 March 2002

Making light work of potato & onion sorting

TONG Engineerings product portfolio continues to extend. At a recent open day the company announced two automated quality grading machines – one for onions and another for potatoes – and a system which uses air to dry potatoes after they have been washed. For good measure, there was also the launch of a new box tipping system.

The automation of potato and onion grading has long been the aim of the industry. Its successful development means a vast reduction in labour demands and, it is claimed, a better job. For onions in particular, such a system enables crops with a high percentage of rejects to be sorted.

To sort these crops manually does not make economic sense and the whole crop would generally have to be discarded in respect of the higher value quality market.

Both the France-built MAF Roda Pomone grader – which was designed initially to handle peaches and apples – and the Denmark-sourced Newtec Astro 126 potato quality grader work in similar ways.

Cameras are used to identify blemishes as the crop passes through the machines and those recognised as being an unacceptable standard are rejected away from the main crop.

For the Pomone, onions are fed under the cameras on moving lanes equipped with carrying hands which maintain them at a set distance from each other.

As they pass beneath the cameras they are rotated so that the whole of their surface can be inspected – each onion has its picture recorded 25 times, it is claimed.

The system basically recognises three features – the degree of darkness, lightness and shape; too dark and rot or bruising is present, too light and the outer skin has been torn away, irregular shape indicates onion necking problems. The system can be adjusted so that it responds to lower or higher amounts of crop irregularities to provide control over the required quality.

Once through the camera zone the onions are then weighed so they can be graded into specified weight groups.

Output of the Pomone is about 2t/hour/lane with the ability to operate up to 12 lanes. Price of a two-lane unit is about £75,000.

For the Newtec Astro 126 with its six lanes, potatoes are singled out onto rollers before passing through the camera grading system which identifies size, cuts, green spots, bruising and several other undesirable potato defects. As with the Pomone, the degree of sensitivity to these defects can be pre-set too so that, through three outlets, class A, class B and reject potatoes can be separated.

Capacity is rated at up to 70,000 potatoes/hour for this £119,000 machine. &#42