After purchase or installment of a grain dryer it is important to evaluate its performance. This is usually done by conducting a drying test. Drying tests are important because actual performance data is often different from rated performance that is provided by the manufacturer. The following is a general procedure for evaluation of a grain dryer.
Drying Test
Paddy rice of a known source should be selected with grain MC that is typical for grain harvested in the area. The paddy should be cleaned so there are very few impurities (straws, etc) in it.
Before loading the material, mix the paddy and take at least 10 samples of the paddy of 10g each to determine variance in moisture content. In addition, sample 500g of wet paddy for laboratory analysis. If possible, take the entire weight of the paddy before loading.
Load the paddy and start the dryer. Measure the time that it took to load the dryer. Note the time that it takes to dry the paddy down to 14% MC. If possible, measure power consumption with a watt meter and measure fuel consumption with a flow meter. Alternatively, fuel consumption can be estimated by taking the initial weight or volume of the fuel and the final fuel weight after drying is completed.
During the drying process, measure drying air temperature with a thermometer at different locations in the dryer. After drying is completed, take the weight of the entire batch of dried grain. Also, take at least 10 samples of 10g for moisture content and one 500g sample for laboratory analysis.
Laboratory Analysis
Conduct a milling analysis of the pre-dried and post-dried sample that includes at least crack detection, milling yield, head rice recovery and discoloration .
Reporting
Calculate the following data to characterize the performance of the dryer:
Average and standard deviation of the moisture content before and after drying.
Total weight loss of paddy
Drying rate (%/h)
Increment in broken grain (i.e. percentage of broken grains before drying minus percentage of broken grains after drying)
Increment in cracked grain (i.e. percentage of cracked grains before drying minus percentage of cracked grains after drying)
Electric power consumption
Fuel consumption