Removing Moisture Extends Oil and Equipment Life
Every manufacturing industry creates its own unique environment, resulting in contamination peculiar to that industry, which in turn, requires appropriately designed breathers. Desiccant breathers are particularly useful in environments that contain high dust and humidity levels.
There are a number of ways that contaminants can enter equipment, including poor oil top-up and sampling methods, improper handling practices, inadequate or poorly maintained seals and the lack of breather filters. The abrasive effects that particles have on hydraulic pumps, turbines or gearboxes are obvious. The effects water has on moving parts are much less understood.
Solid, Liquid and Gas
Water can exist in oil in three states: dissolved, emulsified and free. Individual water molecules dispersed throughout oil are considered to be dissolved. New lubricating oil can retain dissolved water at levels between 200 ppm to 600 ppm, and new motor oils can retain three times this amount before any evidence of moisture is evident. The older the oil, the more water it can hold. At some point the oil becomes saturated and the individual water molecules begin to coalesce, creating microdroplets and a cloudy appearance. As the amount of emulsified water in the oil increases, a layer of free water is produced, which settles to the bottom of tanks and sumps.
Once water has mixed with oil, chemical reactions occur between the water, base oil and various additives, including extreme pressure and wear resistance agents, oxidation and rust inhibitors, and viscosity improvers. The chemical reaction is called hydrolysis. Water can accelerate the oil’s aging rate tenfold. These chemical reactions result in varnish, sludge, organic and inorganic acids, surface deposits and polymerization (a thickening of the lubricant). As little as one percent contamination can reduce bearing life by as much as 90 percent. Additionally, vaporous cavitation, the implosion of water vapor within pressurized systems, can produce honeycomb pitting on mechanical surfaces.
How Desiccant Breathers Work
Even though the basic concept for desiccant breathers has been the same for more than 20 years, they have evolved into numerous products that can handle a multitude of applications.
Comprised of a hygroscopic agent—silica gel that can attract and retain up to 40 percent of its weight in water—and a synthetic filter media, desiccant breathers are an important element in an effective preventive maintenance program. They are designed to prevent moisture and particulate contaminants from entering fluid reservoirs as pressures occur through thermal expansion and contraction of the fluid, and through level changes caused by filling and emptying of reservoirs.