"It seems as though the gear drives on the conveyors experience more water contamination problems in the spring and the fall than during other parts of the year. They are not directly exposed to rain, they don’t have coolers, and they operate continuously. What do you suggest to fix this problem?"
There are several generalities offered in the conditions described, and it is probably time to start measuring and charting some factors. Areas of the country with the highest rates of relative humidity will experience this more frequently.
First, verify that there are no human factors involved, particularly involving operators or housekeepers with a high-volume wash hose.
Second, try measuring the operating temperature of the equipment between the coldest and the hottest part of the day during the spring and fall. Also, watch the weather news for the dew point for every day. Regardless of whether it is operating or not, if the equipment temperature falls below the dew point, then condensation can occur. If the temperature is this low, then the moisture is not going to be driven off very quickly.
Third, for large sumps, install a valve and start each day with a drain-and-inspect routine. Open the valve and slowly drain off any accumulated water. Measure the amount and log it with the other factors. Make note of the sumps that seem to be susceptible to moisture.
Fourth, once the offenders have been identified, replace the vent filters with desiccant-type air breather filters. If this has been done already and the problem still exists, then consider installing a low-pressure air purge into the sump headspace. If you can maintain a positive pressure head, then water from atmospheric humidity will be eliminated. However, be conservative with your air pressure. Central air is expensive, and a small drain can contribute to a significant increase in embedded operating cost.
There are several methods to determine water content. These can be differentiated based on whether the content of water in dissolved form is measured or the absolute water content is determined, i.e., besides measuring dissolved water, free water also is taken into account. Common techniques include FTIR and the Karl Fischer method. In practice, simple screening tests are also used in order to make a rough estimate of whether water is contained. Among the most frequently used tests are a visual assessment, the crackle test and the shaker method.