Water-absorbing filters are the only safe way to prevent free water from escaping into your system/equipment. The elimination of water in oils will reduce rust, corrosion, wear, fuel degradation and other kinds of damage.
This type of pollution can be caused by the humidity in the air, leakage from cooling systems or process water, or leakage of seals and chemical processes
Water may be in a dissolved state and in a free state. All oils can absorb some water. At the oil's saturation point, it will start forming water droplets, also called "free water". Temperature and pressure can influence when the oil meets its saturation point, and free water appear.
Both types are harmful to for the fluid and the hydraulic system. Free water must be avoided and removed if present. The level of dissolved water must be kept as low as possible
There are several ways to remove water. For example: separation, water absorption filter, cellulose filter, coalescing filter, centrifuge, and vacuum dehydration.