Are Your Grain Bins Ready for Winter?

Winter is again making its mark with above average temperatures and a fair number of sunny days. These conditions are great for travelling, but may cause serious problems with grain stored in bins. Check your grain bins! If you don't, you may be in for a nasty surprise.

Cold temperatures are good for long term storage of grains. The problem is that the grain does not cool by merely sitting in the bin in winter. The only way of changing grain temperature is by moving air through the grain mass, a process called aeration. Dry grain sitting in a bin insulates itself from outside air temperatures because of the many air spaces between the individual kernels, and the fact that the kernels are only making point contact with adjacent kernels. Just a thin layer of kernels against the bin wall will actually mimic outside air temperatures.

For successful long-term storage of grain in bins, the grain mass temperature must be kept within 5 C^o of the average outside air temperature. The grain should be cooled every month until about March, then slowly warmed up to match average April air temperatures. If you do not keep grain temperatures within + 5C^o of average outside air temperatures, spoilage problems can result. When temperature differences exceed 5C^o convective air movement will occur, pick up moisture and cause spoilage. Timely and thorough aeration of the bin contents will prevent convective air movement.

The length of time required to completely aerate and cool the grain mass will depend on the airflow rate of your system. This airflow rate, described in cubic feet per minute per bushel (CFM/bushel), is dependent on the bushels of grain in the bin, the depth of grain and the size of fan and motor. See Table 1. Remember, you have to carefully choose when to operate the fan, so that you don't add moisture to the stored grain but do effectively change the temperature.

Bin Check List

1. Turn on the aeration fan.
2. Climb up and look inside the bin. Look for signs of moisture on the underside of the roof. If water droplets or ice are present, you need to aerate your bin. Moisture from the grain has been carried into the attic space and condensed on the roof metal.
3. Sometimes snow can be driven into the top of a storage bin. If there is a light dusting, don't worry. When you run the aeration fan this snow will sublimate and be discharged as harmless water vapour. If much greater amounts of snow are found, shoveling may be required to remove it from the bin.
4. Take a big sniff. Do you notice any off-odours? Your nose will pick up strange odours at very low concentrations. The air should smell like clean grain.
5. Look at the grain surface. Does it look the same as the last time? If it looks dull or off-colour, investigate further.
6. Check the static pressure, or the working pressure of the fan, in the plenum under the aeration floor. Has this pressure changed from last month? If it has gone down, no cause for concern. If the static pressure has gone up, something has increased the resistance of the air as it moves through the grain mass. Investigate deeper into the grain mass.
7. Look for any signs of insect activity.
8. Record your notes in a monitoring logbook. This helps keep track if things have changed in the various bins.

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