Troubleshooting mechanical dryers

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.


Potential cause

Possible Solutions

Long drying time

Ineffective fan

Fan testing, replace fan

Reduced airflow from turbulences or high resistance of air distribution system

Clean perforated sheets, bigger plenum chamber and air ducts,

Low temperatures

Increase temperature within acceptable limits

Uneven drying

Too high air temperature in fixed bed dryers

Reduce air temperature, Mixing after initial drying

Improve temperature control

High fuel consumption

Ineffective fan or air-distribution system

Improve air distribution system, use fan with higher efficiency

Air-flow rates too high

Reduce air flow rate to normal levels (smaller fan)

Low germination rate

Too high drying air temperatures

Reduce air temperature

Low germination potential of paddy

Dry 1kg of the same crop in the shade, make germination test and compare with machine dried sample

High number of broken grains

Moisture gradient, re-wetting after drying

Reduce delays in drying, don't do field drying, dry immediately after harvesting


Feeding of grain with different MC, re-wetting of dryer grain fractions

Mix grain during drying in batch dryers