The Importance of Keeping Lubricants DryStratson
The Importance of Keeping Lubricants Dry
Water is everywhere and tends to get into everything. Plants, animals, and people need water to live, however water is not desirable in lubricants. Let us look at how water gets into equipment, the damage it does, how to test for water and how to keep it out of your lubricants and equipment. The Importance of Keeping Lubricants Dry is often underestimated.
There is water in the air and it is more apparent on humid days or near large bodies of water such as lakes or oceans. As equipment operates it generally will heat up and then cool down when turned off or on a low load cycle. During the cool down the equipment will draw in air through breathers or openings. If the breathers are clogged it will draw air in through the seals and gaskets. As the air cools water condenses into droplets and enters the lubricant. Totally enclosed systems will have a surge tank to handle expansion and contraction of the fluid, seals must be well maintained on these units to prevent water from entering. Many manufacturing, industrial and construction sites will have wash downs and frequent clean out procedures with steam or water that can enter through seals, gaskets, and other openings.
As little at 1000 ppm (0.1%) water will shorten the life of a bearing by 80% or more. Water will promote or cause a variety of issues in greases, oils, and equipment. Oil can hold 1 to 600 ppm of dissolved water that is not visible nor separate out easily. Aged oil can hold up to 2000 ppm (0.2%) of dissolved water depending on the age and viscosity.
Saturated water is visible in the oil as a haze, and free water will generally be on the bottom of the sump, tank or any low areas. Water can displace oil or grease on a metal surface and cause corrosion, it can also break down EP and AW additives to form sulfuric or phosphoric acids that will raise the acid number of the lubricant and promote corrosion of all metals.
Most lubricants have anti-oxidants to help provide longer service life, water will promote oxidation that will not only shorten lubricant life it will generate sludge and varnish. Water is very polar so it will solubilize any polar compounds like oxides, spend additives, particles, and carbon fines to form sludge balls and emulsions that can clog filters, oilways, glands, and orifices.
Temperature below freezing
When the temperature drops below freezing, as little as 500 ppm (0.05%) water can restrict flow, cause pump starvation, plug valves and filters. This can result in pump failures, erratic operation, excessive noise, and poor performance. Rolling elements rely on an oil’s viscosity to develop a protective oil film. Water can emulsify with oil or grease lowering the viscosity to where the film may rupture and cause metal to metal contact leading to excessive wear. Under high pressure water will vaporize into steam and may explode out of the contact area. In some cases, there may be enough pressure to damage valves and pumps, rupture hoses, and damages seals. Finally, water lowers the oil’s interfacial tension which reduces its ability to release air, causing aeration and foam. It only takes a 1000 ppm of water to turn a bearing sump into a bubble bath. The introduction of air increases oxidation, increases heat, causes cavitation, and interferes with oil flow.
Test for water in a system
There are several ways to test for water in a system. The visual method can detect water over 1000 ppm and is easy to perform. Pull a sample of oil from the sump or tank, if it looks milky or hazy it maybe air or water. If it is still hazy after sitting for an hour or so then it is water. Pull a sample from the bottom and put into a clear container, water will settle to the bottom after a time depending on the quality and age of the oil. Grease will have a milky appearance when water has emulsified with it.
The crackle test can be performed where ever there is a heat source and a metal container or pan. Heat the pan to 266F or 130F, the pan should not be glowing red but hot enough that a drop of water dances across it letting off steam. Put a large drop of oil on the hot pan and observe. Bubbles rapidly forming indicate water, a crackling sound indicates over 500 ppm of water.
Many oil testing labs will use Infrared Spectrometry to determine the presence of water. This test can only determine water content over 0.1% (1000ppm) so most reports will read “<0.1% water”.
Karl Fischer test
The Karl Fischer test requires specialized equipment and chemicals but can test water levels down to 10 ppm.
The Calcium Hydride test is another field test that can be run. A known amount of oil is put into a sealed container with the calcium hydride, shaken and the amount of hydrogen gas evolved is equal to the amount of water present.
Best way to protect your equipment
The best way to protect your equipment is to prevent water from getting into the system. Use a good desiccant in the breathers and replace as needed. Seals and gaskets should be kept in good condition, keep lids and other openings closed always. Check your fluid often and run oil analysis periodically. Store all your lubricants inside if possible, even a sealed plastic pail left outside for as little as a few weeks could have water in it. Remove water from sumps, tanks, and low areas frequently, many of these are designed with drains or sump pumps for this purpose. Performing a system flush when changing oil will help remove water from valves, lines, hoses and low areas.
SWEPCO gear, hydraulic, compressor, and turbine oils are all designed to separate water rapidly for easy removal.
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Southwestern Petroleum Corporation®