A desiccant is a dehumidifying agent that induces or sustains a state of dryness in its vicinity. It adsorbs and holds particles of water to itself. Over time, the desiccant breaks down and loses its effectiveness. This causes increased energy consumption within the compressed air system due to lower compression efficiency, air leakage, and/or pressure variability.
Fortunately it’s possible to monitor desiccant quality. Some of the more common methods are listed below.
Indicating Silica Gel
Indicating silica gel is a silica gel bead that changes color when the product has reached the end of its useful life. The gel granules are dark in color, usually a deep cobalt blue, when dry. The beads gradually become paler, turning pink as the granules are saturated with moisture. Typically, the color changes as the desiccant goes past 8% moisture levels by weight. Once the product has turned pink it is time to replace the desiccant.
Relative Humidity Indicators
Relative humidity indicators are another quick way to test compressed systems for moisture. Working on a principle similar to silica gel, relative humidity indicators contain beads that begin to change color at 10% RH. The beads become clear at 15% RH, indicating damaging moisture in the compressed air system.
Relative humidity indicators can be recharged hundreds of times before they need to be replaced, making them an economical choice for monitoring compressed air systems.