This article provides features of cleaning grains and pulses, by manual and motorised way. © Labour saving technologies and practices. FAO 2007
Traditional threshing methods often leave a lot of trash mixed with the grains and pulses. Separating the trash can be very labour intensive.
Traditional cleaning is carried out by winnowing or sieving and sometimes a combination of the two:
· winnowing: in windy areas the threshed crop is tossed up into the air, using forks, spades or baskets and the grain and pulses fall vertically while the less dense chaff and straw are blown to one side.
· sieving: further cleaning is carried out using sieves, made of open-weave baskets or a wire mesh, to remove soil, stones and any metal objects (such as nails and screws). The removal of the latter is important, particularly when mechanised milling is to be undertaken, as they can damage the milling screens.
Features of cleaning grains and pulses
Simple wooden or steel enclosed fan mills using sieves and screens makes more efficient use of manual power, operated either by hand or pedal power. Output ranges from around 150 - 300 kg per hour.
Motorised threshers often include the winnowing and cleaning process.
Specialised motorised cleaners range from the simple to the complex; some also grade the seed at the same time. Many are mobile and can be used by contractors. Quoted outputs range from 1 - 4 tonne per hour for motors of around 3 kW.
· Labour saving: reduces labour bottlenecks at peak periods, particularly motorised equipment.
· Livelihood resilience strengthening: clean, undamaged and pest and disease free produce at the correct moisture content fetch higher prices when sold or assists with preparing the seed for storage or planting. Grading of grain or pulses is required for sale and for selecting appropriate seed plates for mechanised planting.
· Livelihood diversification: income generating opportunities if motorised equipment operated by community group or contractor.
· Equipment: manually operated equipment is robust and relatively easy to fabricate, maintain and repair.
· Skills: manually operated equipment is simple to operate.
· Labour: the modest increase in work rates with manually operated equipment may not justify cost of equipment.
· Livelihood: text
Equipment: some cleaning equipment may be required for only a short period during the year and lies idle for most of the year.
· Cost and risk: relatively high cost for private ownership and hence relatively high financial risk.
· Skills: motorised equipment requires some specialist skills in use and maintenance of machine.
· Risk: may fail if hire services are introduced into an area where there is insufficient demand to pay for contractual and community-owned services.
· Infrastructure: motorised equipment requires adequate supporting infrastructure.
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