Onion line can handle 200t/day
By Andy Collings
GRADING onions is virtually a year-round operation at Dennis Clarke Partnerships Metland Farm Centre at Soham, Cambs. Each year sees up to 20,000t of them passing through the companys grading lines – the 2800ha (7000-acre) farm apportions no less than a 400ha/year (1000 acres) for the growing of onions.
"With supermarkets now so scrupulous in their quality demands, we need to produce onions which are well formed, clean and topped," explains onion operation manager, Peter Richard-son.
To be able to achieve this aim DCP recently installed a grading line built by Nicholson of Downham Market, Norfolk which it believes to be one of the largest in Europe. Capable of handling up to 200t/day it incorporates some of the latest technology.
Onions – picklers or ware – arrive from the store by lorry and are tipped onto an elevator which takes them over the first cleaning webs. They then arrive at one of the latest innovations – a high frequency web – which, driven by a fast moving cam, cleans and separates the onions.
"Before we installed this component output of the grading line was running below par," says Mr Richardson. "Good cleaning early on helps the rest of the line to work at a higher speed – particularly the topping unit."
Topping onions accurately at speed is not one of the easiest of operations. They pass along narrow grooves which has air blown down onto it. This turns the onions to put the tops below the grooves. Rotating blades then remove the tops.
After being size graded into five separate lines the onions are stored in boxes before being taken to the packing station.
Up to 20,000t of onions pass up these grading lines each year. DCP based at Soham, Cambs grows over 400ha (1000 acres) of onions, including crops destined for the pickling and quality ware trade.
Nicholson high frequency web is claimed to have increased throughput of the grading line significantly.