Removing water and moisture from lubricating oil

Since the sources of water contamination are so numerous and ubiquitous, eliminating all sources of moisture can be very difficult. Removing water from oil can also be a challenging task, but there are several methods available. Each method has advantages and disadvantages, so each must be carefully evaluated for the particular application. Some of the common methods for removing water from oil include:

Settling/Evaporation

• Natural - gravity acts on the water to separate it from the oil, and water escapes from the fluid via natural evaporation.
• Inexpensive.
• Least effective of known methods.
• Properly designed reservoir is required.
• Only free water is removed.

Centrifuging (Centrifugal Separation)

• Only the free water form of water is removed to about 20 ppm by weight, above the saturation point.
• Entrained gases aren't removed.
• Emulsified water content tends to increase.
• Dirt and other solids are removed.
• Additives can be removed by this method.

Coalescing Filters/Screens

• Only free water is removed.
• A coalescing cartridge filter is used to separate the water from the oil.
• Additives can be removed by this method.
• Only effective for narrow ranges of viscosity and specific gravity.
• Some manufacturers claim "No removal of additives."

Filter/Dryers

• Cartridge-type filters that use super-absorbent materials to soak up water.
• Dissolved water isn't removed.

Vacuum Treating (Vacuum Dehydrating)

• The wet lubricant is heated in a vacuum to separate the water.
• Additives usually aren't removed from the lubricant, since it is a chemical separation.
• Dissolved, emulsified, and free water can be removed.
• When combined with effective filtration media, capable of being a highly effective lubricant purification system.

Gas Sparging/Air Stripping

• The chemical separation principle of air stripping is used.
• Dissolved, emulsified, and free water are removed.
• Additives are not removed.
• Nitrogen or air can be used.

Attention to detail is paramount in achieving cleanliness levels that produce large improvements in machine life and availability. When it comes to machine life, lubricant cleanup has proven to be one of the simpler and more cost-effective methods of achieving measurable improvement. Don't wait for contaminants to destroy your machines. Clean up your oil and keep it clean.