Water is probably the most intense and complicated form of contaminant when it comes to affecting the functionality of different parts of machines, especially the bearings. That’s mainly because water co-exists with oils in various states and also undergoes different physical and chemical transformations over time.
For the most part, moisture-related damage experienced by both oil and machine ultimately results in an operational malfunction of the bearings. Water has been known to cause severe damage to a variety of machine surfaces, both directly and indirectly. One of the most severe harms done to different equipment by water is the cascading or chain reaction failure.
Water could lead to premature oxidation of the base oil. When these oxides are mixed with more water, it leads to the formation of corrosive acidic fluid. Oxidation can also enhance the overall viscosity of the oil, leading to impeding oil flow and further damage to the bearing. Now, let’s discuss in detail how water causes machine bearing malfunctions:
Also known as hydrogen blistering or embrittlement, this machine bearing failure is regarded as one of the most acute malfunctions by the bearing manufacturers. Typical sources of hydrogen include water, corrosion, electrolysis. Water gets attracted to tiny fatigue cracks present in rollers and balls through capillary forces.
After coming into direct contact with free metal, water breaks down and frees up atomic hydrogen. This leads to additional crack fracture and propagation. It has been observed that high-tensile strength steel is at increased risk of damage in such cases. Mineral oils, sulfur from additives, and environmental hydrogen sulfide could enhance the fracture process as well. Overall, both soluble, as well as free water, pose such risks.
Most of the bearings contain just a small amount of lubricant, thus having a small number of antioxidants. High temperatures surrounded by water and metal particles could consume these antioxidants in no time, resulting in the removal of the oxidative protective environment from the lubricant. This process of oil oxidation leads to corrosion, varnish, sludge, and impaired oil flow.
Both water and air moisture aid in the formation of rust. Water significantly increases the corrosive potential of acids. Elastohydrodynamic EHD oil films are critical to providing bearing lubricant film strength in order to control wear and fatigue of metal surfaces. Pitted and etched surfaces resulting from corrosion on rolling elements and bearing raceways highly disrupt the formation of these critical EHDs. Static fretting and etching also get accelerated by free water.
As already mentioned, water results in the depletion of antioxidants. It also diminishes the performance of some other crucial additives, including rust inhibitors, detergents, demulsifying agents, dispersants, and more. Water has the potential to hydrolyze some additives, agglomerate, or wash them out of the working fluid into puddles. Water can also transform sulfur-phosphorus EP additives into sulfuric and phosphoric acids, increasing an oil’s acid number.
Oil Flow Restrictions
Due to the polar nature of water, it can mop up polar oil impurities such as oxides, particles, dead additives, and carbon resin to produce sludge emulsions. These amorphous suspensions can enter critical oil ways feeding bearings of lubricating oil. When sludge hinders the oil flow, bearing failure is imminent as it regularly suffers a starvation condition.