A drying system can only maintain quality but it cannot improve the quality of paddy. When a dryer produces poor quality paddy it is therefore important to compare the paddy from the dryer with a reference sample from the same batch that was dried under controlled conditions, e.g. in an air-conditioned room, or in the shade by spreading a thin layer and frequently mixing. Otherwise it is difficult to tell whether the low quality is caused by quality reduction that occurred before drying, e.g. during field drying, or in the drying system. Underneath some problems with mechanical dryers, their potential causes and possible solutions are explained.
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Problem
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Potential cause
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Possible Solutions
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Long drying time
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Ineffective fan
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Fan testing, replace fan
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Reduced airflow from turbulences or high resistance of air distribution system
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Clean perforated sheets, bigger plenum chamber and air ducts,
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Low temperatures
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Increase temperature within acceptable limits
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Uneven drying
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Too high air temperature in fixed bed dryers
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Reduce air temperature, Mixing after initial drying
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Improve temperature control
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High fuel consumption
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Ineffective fan or air-distribution system
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Improve air distribution system, use fan with higher efficiency
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Air-flow rates too high
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Reduce air flow rate to normal levels (smaller fan)
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Low germination rate
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Too high drying air temperatures
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Reduce air temperature
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Low germination potential of paddy
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Dry 1kg of the same crop in the shade, make germination test and compare with machine dried sample
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High number of broken grains
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Moisture gradient, re-wetting after drying
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Reduce delays in drying, don't do field drying, dry immediately after harvesting
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Feeding of grain with different MC, re-wetting of dryer grain fractions
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Mix grain during drying in batch dryers
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