14 November 1997

Smartening up samples

By Robert Harris

POOR grain quality is widespread this year. But there is much growers can do to improve samples to meet contract requirements and ensure best prices, according to grain cleaner makers.

How hard grain has to be cleaned depends on:

&#8226 Grain quality in the barn.

&#8226 Market specification.

&#8226 The availability and price of discounted payments for grain which fails to meet that specification.

Provided the extra income generated covers screenings losses and the cost of the operation, it is worth doing, says Ian Turner, general sales manager for Glos-based Law-Denis Engineering.

Grain destined for high quality markets offers the best paybacks, says Terry Marwood of Westrup in Wetherby, N Yorks. Milling wheat premiums are about £25/t for group 1 and nearly £10/t for group 2 varieties. Malting barley is worth about £16/t more than feed.

Quality boost

Many cleaners on farm are identical to those used by merchants, and are just as capable of increasing bushel weights and Hagberg values, or reducing screenings and admixture – in the right hands.

All too often, cleaners are not used correctly so perform poorly, says Mr Turner.

Both reciprocating and rotary sieves are available. The former are usually found on machines of 20t/hour or less capacity, rotary sieves on larger models. Small 20t/hour models cost about £12,000, rising to £25,000 for 100t/hour machines.

"But be careful, especially in a year like this. Output can halve when cleaning a bad sample, and by a fifth when grading malting barley to a tight specification."

Good aspiration is a must, Mr Turner adds. "Buy a mainline aspirator which will remove trash like light weed seeds as well as dust. It can improve bushel weight and appearance markedly."

Plenty of sieve area is important. Heavier or bigger trash is retained on a large-holed sieve while grain falls through onto smaller-holed sieves. Good grain is retained on these, but screenings fall through.

The lower the bushel weight, the greater the gain, says Mr Marwood. In ADAS trials with a Kamas SAC 1500 machine, wheat at 65.8kg/hl was improved by 5.1kg/hl after cleaning. But wheat at 75.8kg/hl only improved by 0.3kg/hl.

Visually, the amount of material removed may seem much higher than it actually is, he adds. "Screenings contain light chaff and straw which contribute little to the total weight removed."

Operators must match settings to the job, Mr Turner advises. "Too often, they try to make do with one set of screens."

Standard issue for wheat and barley are 4.5mm x 25mm for the large sieve, and 2.1mm x 25mm for the small ones. "Those are fine for most grain. But when you are dressing malting barley or milling wheat, you need to change."

Screens cost about £300. "A couple of rejected loads could cost you at least that." For malting barley a 2.3mm x 20mm sieve is a good choice. Although it removes slightly more grain than strictly necessary, it allows faster throughput while ensuring the final sample still meets the UK standard of 2.25mm.

The optimum sieve to dress milling wheat varies, he points out. "It depends on the sample, and how much grain you are prepared or need to sacrifice to make an acceptable job."

Sieve selection

Earlier ADAS work suggests careful sieve selection can improve Hagberg falling numbers by removing impurities, says Mr Marwood. "But it can be reduced if small grains are removed. The bottom sieve slots should be no bigger than 2mm and sufficient, but not excessive aspiration should be used to retain high Hagberg grains."

Both grain throughput and the amount of wind can be altered on aspirators. "Dont expect last years settings to work with this years grain – you are dealing with a different commodity," says Mr Turner.

"Check bushel weight and appearance, and have occasional samples checked in a laboratory or by the buyer."

Gravity tables can also be used to improve grain, notably bushel weights and therefore Hagberg in milling wheat. Cost and throughput make mobile units the best approach, says Mr Turner.n

GRADED GRAINS

&#8226 Poor grain can be improved.

&#8226 Best returns from premium-carrying grain.

&#8226 Standard aspirator/sieve cleaners adequate.

&#8226 Improved bushel weights, less admixture, better Hagbergs.

&#8226 Choose right sieves and settings.