Why Water is the Biggest Enemy of Lube Oil

A study by tribology experts indicated a fivefold increase in the operating life for an engine by decreasing the water content in oil. This signifies the extent of damage that water can cause by contaminating the lube oil.

What lies undetected in plain sight can exert some of the most sinister effects on the engine’s components. Water molecules infiltrate fuel and lubricant systems largely through the air and inconspicuous leakage points. They emulsify in oil, invisible to the naked eye, going largely undetected by maintenance engineers and plant operators.

Depending on their concentration, these water molecules can damage your components in a large variety of ways, setting back your asset reliability management system by thousands of maintenance dollars and loss of productivity. As a caution, it would be well worth noting the dangers of this topic to enable the best practices for your oil quality management system.

The holistic oil quality management comprising real-time oil condition monitoring and cleaning of oil to get rid of different contaminants including water helps run your engines most efficiently with a significantly longer operating life.

How Water is Present in the Lube Oil:

Water can be present in the lube oil in various ways, such as:

• Dissolved water: Oil and water are not entirely immiscible. When water levels are below the saturation point, they are invisibly dissolved in the larger volume of oil.
• Emulsified water: This refers to microscopic globules of water dispersed in suspension in the oil after the water content has exceeded the saturation point.
• Free water: Refers to further addition of water that readily settles to the sump’s bottom as a layer in the oil. This is the most destructive state of water contamination.

How Does Water Affect Asset Reliability Management?

There are two interrelated aspects of this:

1. Water vs. Oil
2. Water vs. Mechanical Components

Water vs. Oil

Water initially affects the components of the oil itself. Most oils are made up of a base oil and additive package. Under conditions of high pressure and overheating, which are common in an engine, water acts as a catalyst for the degradation of each of these:

• Base oil: Some synthetic oils react with water, resulting in the destruction of the base oil and the formation of acidic byproducts. These byproducts corrode metal components and cause sludge.
• Additives: Some additives are hydrolyzed by water, resulting in both additive depletion and the formation of acidic byproducts. These acidic by-products can then cause corrosive wear, especially at the Babbitt. This results in sludge and sediment buildup as well.

Additionally, water reduces the viscosity of the oil, which further complicates the asset reliability management of the system.

Water vs. Mechanical Components

Water is relatively incompressible compared to oil. This means pressurized situations, it will maintain its low viscosity, reducing oil film strength, which results in more component wear and tear. Also, when water is exposed to the high pressures in “load zones” near gears and bearings, it causes problems such as:

• Cavitation & Micro-pitting: When water and oil are highly pressured, the water droplets implode at high temperature, and result in explosive micro-jets which cause micro-pitting on the metal surfaces.
• Hydrogen embrittlement: This occurs near the high-pressured rolling element bearing, where some water molecules can be ripped into their constituent ions. The hydrogen ions are absorbed into the metal surfaces, making them brittle.
• Rust: Water reacts with steel surfaces to produce iron oxides.
• Contact Fatigue: Water affects the oil film strength i.e. reducing it. Therefore, the viscosity is reduced, and metal surfaces come in contact with each other, causing more abrasion and spalling.
• Water etching: Water also reacts with acids in the oil to abrade raceways and bearing surfaces.

How to Deal with Water Contamination

Dealing with water contamination is an integral part of the oil management strategy and involves two essential steps—detection and cleaning.

Step 1: Detection

Traditional: methods ranging from the rudimentary “Crackle Test” to a more precise “Karl Fisher Titration” method.

Cutting-edge technology:
Water contamination will not always be detected by periodic off-line oil sampling. With the advent of real-time oil condition monitoring sensors which are now affordable, it is possible to detect the water contamination by trending the oil quality reading along with the oil temperature reading.

Step 2: Cleaning
There are several filtration units, but these cannot remove all types of contaminants. For effective removal of the water from oil, high-efficiency, high-depth cellulose filters work the best. With their deeper path (as high as 114 mm thick) and the highly absorbing nature of their filter element, these filters are the most efficient and cost-effective solution for engine application.

If the contamination level is too high, additional solutions like a Centrifugal Separators, Vacuum Dehydration, and the Bottom Sediment & Water (BS&W) bowls can be used. Use of a high-demulsibility lubricant can also be an option for a more distinct separation of water from oil. 

How Oil Quality Management Affects Engine’s Life

In a study done by Noria Corp., USA, it was learned that if you reduce the water level in the oil from 2500 ppm to 156 ppm, you effectively increase the machine’s operating life (measured in terms of the MTBF—Mean Time Between Failure) by up to 5 times!