[ICE Chips] Answers to Your Toughest Question

We have trouble with mold inside our two outside flour silos when the weather changes. I also have noticed that there are some very small insects on the top of the silos and on the breather socks. Currently, a contractor cleans the silos, but it has become too expensive. I want our own employees to clean them, but they really don’t want to. What we can do?

Your problem is far too common with outdoor bulk systems. During the unloading process, the temperature of the flour increases. When the weather changes, the head space inside the silo cools and often causes condensation to form. I’ve witnessed extreme cases of three inches of wet flour on the top of the silo. The result was an ongoing problem with line separation or when breather bags ruptured. Because of the condensation, mold develops. This creates a very unpleasant situation.

The most common insects found in this situation are flat grain beetles (Criptolestes pusilus) and psocids. The challenge with these insects is that the numbers can become extremely high before they are noticed. Also, both types can pass through a 30-mesh sifter screen, which is commonly used in flour sifters. The good news is that maintaining a clean, mold-free condition in the head space will eliminate this problem. Unfortunately, this requires specialized equipment and trained personnel and the unit is out of service for several days while it is properly washed, sanitized and dried. This can become extremely costly.

To successfully eliminate this problem you have to address the root cause, which is moisture. This is accomplished when the humidity level remains at a point where condensation does not form. Repeatedly cleaning the interior will only address the results of the moisture, it will not resolve the issue.

Ultimately, a method that eliminates or reduces temperature changes to acceptable levels or that reduces the relative humidity in the head space will be required. This can be accomplished by enclosing silos in temperature-controlled structures or by installing dehumidifier units to reduce moisture in the head space. Many facilities have had good results with dehumidifier units because they control and remove condensation. AIB