Dirt is all around us and while it may be critical for the plants to grow, it is not as warmly received in our machines. However, when we begin thinking about contamination, this is not just limited to dirt particles. Contaminants are anything that enters a system which should not be there or is considered foreign to that system.
In the lubrication world, contaminants can be classified into three categories: Gases, Liquids or Solids. Typically, all these contaminants can enter the lubricants at different stages of storage and handling or if there is an internal / external leak in the lubrication system. During these times, contaminants may get into the system without the operators knowing of their intrusion and can cause substantial damage to components.
Gases as contaminants
While gases may not seem like a large impact contaminant, they can cause serious harm to your machines. Usually, air (oxygen) is one of the most prevalent gaseous contaminants and since it is present all around us, it is a bit difficult to ensure that it doesn’t enter our systems. The presence of oxygen is usually not that dangerous unless it is coupled with other factors such as heat or other contaminants such as water.
If we have trapped air bubbles in our lubricants, this can also lead to microdieseling in our lubricants. In this process, the insides of our components can experience cavitation. On the other hand, the oil will undergo degradation often resulting in the presence of soot, tars and sludge due to the air bubbles collapsing. When the air bubble collapses, this can produce temperatures in excess of 1,000°C which leads to the degradation of the oil.
Other gases which can enter the lubrication system may be ‘process’ gases (such as carbon dioxide, nitrogen or even ammonia). Normally, a lot of the process gases are non-reactive with the lubricants. However, there may be some cases where these gases can be a catalyst to initiate other reactions within the lubricant (given specific conditions). As such, the ingression of any gas should always be considered a contaminant and then deemed harmful or not based on its nature.
Liquids as contaminants
In lubrication systems, liquids as contaminants or foreign material tend to be more prevalent than gases. Two of the most common liquid contaminants are water and fuel depending on the system. Both water and fuel have detrimental effects on the lubricant affecting its viscosity and by extension initiating damage to the internal components.
Water should never be present in any lubricant! However, it can exist in three different states if it is present. It can be free, dissolved or emulsified. Free water usually settles out at the bottom of the sump while dissolved water remains in solution with the oil (often leading to oxidation) and emulsified water exists where the oil has a hazy or milky appearance. In the emulsified state, water is most dangerous as it degrades the oil quickly and affects the pressure and lubrication properties of the oil.
Additionally, water can cause an increase in the viscosity of the oil. This can lead to additional energy being required for components to work harder leading to inefficient systems. It can also cause leeching of particular additives rendering the oil ineffective in its functions of protecting the components.
On the other hand, fuel dilution often occurs in diesel engines. Typically, this is a ‘process’ liquid getting into the lubricant. When fuel enters lubricants, it can decrease its viscosity causing the oil film to be thinner than it should. As such, the lubricant no longer provides protection between the two component surfaces and this often leads to wear.
While water and fuel are the major liquid contaminants, they are not the only ones which exist. Other lubricants can also be considered liquid contaminants especially if the wrong lubricant is mixed in with the intended lubricant. This is especially true for hydraulic oils being mixed with engine oils where the combination can be catastrophic as not all additives are compatible.
Solid contaminants
Solids are the most common type of contaminant as ingression of these particles occurs the most frequently during storage and handling of lubricants. Dirt is not the only solid contaminant for lubrication systems. In fact, many lubrication systems exist in industrial / manufacturing environments where there may be very fine particles (such as cement or even flour) which can easily enter these systems if they are left open to the environment.
In lubrication systems, it is easy to think that all solid contaminants come from external sources of ingression. However, internal sources may also be present. Usually, these can be in the form of wear particles which are internally generated due to inadequate lubrication, alternative forms of wear or even the production of solid deposits due to chemical reactions within the oil.
Whether solid contaminants ingress externally or internally, they can cause severe damage to the components in the form of wear or even creating blockages in very small clearances. Abrasive wear is one of the most common types associated with solid contaminants. However, cracks and fatigue wear can also occur from the presence of these contaminants. Depending on the type of solid contaminant, this can also act as a catalyst for degradation in the lubricant.
Whether it’s gaseous, liquid or solid, contamination is not an ally to any machine. If it is foreign to your lubricant system or doesn’t belong there, then it contaminates your system. Stay tuned for the second part of this series, where we talk some more about ways to identify and prevent contamination.
Thank you Sanya Mathura with Strategic Reliability Solutions Ltd for sharing this informative and educational article with us!
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Lubrication by Diana Pereda