The reasons for the aging of lubricants that cause their periodic replacement are known. Many of the factors that influence lubricant consumption and lubricant change intervals are not in the control zone of most users. However, there are factors that are controllable and industries can capitalize on reducing the costs and risks associated with relubrication.
According to American studies, the actual cost of a lubricant change can exceed 40 times the cost of the lubricant itself. In fact, there are many hidden costs and unknown risks that are evident during the relubrication process and that must be considered.
Among a wide range of risks, let’s look at some of the risks when making a simple lubricant change:
- Introduction of the wrong, mixed or incompatible lubricant
- Introduction of a contaminated lubricant
- Introduction of a stored degraded lubricant (severe additive stratification is a common example)
- Introduction of a defective lubricant (mixture or related formulation)
- Disturbance of sediment and sludge during the lubrication change (known as the fisheye effect and can result in subsequent lubricant blockage and non-lubrication)
- Expel sludge and deposits, causing leakage (disturbance with lubricant clots)
- Dry restart, dirty lubricant is restarted (before the filter can restore cleanliness)
- Malfunctions due to human error during or immediately after a lubricant change (overload, no load, failure to open / close valves, deadhead pumps, etc.)
When we look at the true cost of a lubricant change and the associated risks, there are plenty of financial and operating reasons for the operation to maximize, or at least optimize, the lubricant change interval. When implemented correctly, it can translate into a marked reduction in lubricant consumption, lower maintenance costs and greater machine reliability.
As it is easily understood, the lubricant does not last forever, it ages in a similar way to the human body, hence the need for its replacement. When exposing a lubricant to the most varied elements inside a machine (heat, air, water, glycol, particles, shear, etc.), it can often cause irreparable damage. Additives can prolong the life of a lubricant, but they cannot prevent degradation and aging.
There are several underlying reasons for replacing lubricants:
- Current or imminent loss of lubricant performance (friction control, wear control, deposit control, corrosion control, etc.).
- The lubricant became a carrier for one or more harmful and non-removable contaminants (sludge, glycol, bacteria, acids, etc.).
- I am afraid that the lubricant needs to be changed (for one or both of the first two reasons) without a convenient means of confirmation.
Refer below to the various common and some not so common methods for reducing lubricant consumption and increasing drain intervals. Note that not all methods have practical application in all cases where lubricants are used. However, in cases where drainage intervals can be increased, these have a greater potential benefit, a strategy for success related to the presented methods can generally be constructed.
– Select Lubricants with Long Performance and Long Life:
There are many differences in the durability of lubricants when exposed to the machine’s operating conditions. Therefore, a simplistic strategy is to select lubricants with robust formulations that resist degradation in the target application. The use of high-purity mineral lubricants, oxidation-stable synthetics, improved antioxidant systems, better demulsifiers, robust base additives and long-life dispersants can substantially extend the life of the lubricant. In addition, select lubricants for the applications for which they were formulated. For example, a high-performance engine lubricant can perform better on a diesel engine, but it can quickly fail when used in a hydraulic system.
– Reduce the density of critical exposures that wear down additives and damage base oils:
Most additives are damaged at a rate proportional to the density of exposure to a variety of contaminants and operating conditions. Water, garbage, metallic particles, soot, heat, acids and air are all contaminants that overload the additives and lead to their depletion. Additive depletion is the common precursor for base oil failure, poor machine performance and eventual machine failure.
In addition, mention is made of some examples of reduced exposure density:
- Increase the volume of used oil. The greater the volume of oil, the more total amount of additive protection there is and the more contaminants become diluted. The dilution of the contaminant reduces the severity of wear (activation energy in the case of heat) in both additives and base oil. However, increasing the volume of oil is not a practical option in many applications.
- Keep contamination control under surveillance. Keeping lubricants cooler, cleaner, dry and well protected can substantially extend service life. This is done by restricting the entry of contaminants and quick removal (filtration, refrigerators, separators, etc.). It is important not only to reduce the density of these contaminants, but also the longevity of the exposure.
- Limit exposure to pro-oxidants, free radicals, hydroperoxides and other oils.
The by-products of oxidation accelerate the rate of additive depletion (antioxidants) when the new lubricant is added. In many cases, it is important to wash these pro-oxidants from a machine before adding a new lubricant. Lubricant analysis can alert users to the need for cleaning during a lubricant change.
– Restore Worn Additives:
Depleted additives can be restored in a number of ways to prolong the interval between lubricant changes and avoid wasting healthy lubricant.
These are the two options available to industries:
- Rebuilding additives is the practice of giving certain impoverished additives a boost. Additive reconstruction involves the introduction of an additive concentrate into the lubricant circulation in service. Only certain additives can be rebuilt with adequate success and the practice is generally applied only to machines with large volumes of oil (for example, turbine oil, compressor lubricants and hydraulic fluids). In addition, it should only be done after laboratory tests have confirmed that a lubricant: 1) has not suffered irreparable damage, 2) there are no threatening contaminants that cannot be easily removed (glycol, for example) and 3) the use of an additive supplement has been determined not to impair the performance of other lubricating properties
- When it is inconvenient or risky to change the lubricant, an option is to perform a partial bleed and feed lubricant change. This involves draining a portion (say, a third) of the lubricant volume, immediately followed by the introduction of new lubricant. The drained lubricant removes some of the contaminants and the new one dilutes the remaining contaminants and adds new additive.
– Optimize lubricant change time:
A large amount of lubricant is wasted each year due to premature and unnecessary lubricant changes. In fact, the life expectancy of a lubricant cannot be predicted accurately due to the numerous factors that induce aging and resist aging. No lubricant or software specialist can predict the need for a lubricant change. Therefore, users are faced with changing the lubricant before any end-of-life lubricant condition is expected (a wasteful and risky practice) or to periodically analyze the lubricant to monitor advancing life (a much better practice). Analyzing the lubricant using routine lubricant analysis is a much more practical and reliable alternative.
– Small Leaks:
Leakage does not really trigger the need for a lubricant change, but it certainly results in unnecessary lubricant consumption through the repeated addition of replacement oil. Fortunately, oil in good condition and uncontaminated can have an incredible positive impact in reducing lubricant leakage. Likewise, leakage is often associated with excessive entry of contaminants, which, of course, shortens the life of lubricants.
From the above, there are many opportunities to reduce the frequency of lubricant change and the associated costs and risks. All involve some form of intervention, transforming past practices into new practices that prolong the life of the lubricant. Precision lubrication deals with the selection of the correct intervention action (s) to systematically achieve the intended objective at the lowest possible cost and risk for the industry. In this case, less lubricant consumption, increasing the space between lubricant changes.