Refined Bypass Filtering and Wear Metal Masking Concerns

Background

Some oil labs and manufacturers advise against using refined or bypass filter systems on lubricated equipment. They fear that bypass filter systems, which can remove contaminates as small as 1 micron in diameter, can "mask or hide" the accumulation of metal generated from equipment wear. Typically, routine oil tests measure the concentration levels of metals or elements to determine when the oil needs to be serviced. These levels, usually measured in parts per million (ppm), indicate when equipment wear has occurred, alerting the user to service the oil. If increases in concentration levels or wear trends are not visible or "masked," they claim equipment damage may occur since oil sample results could cause the user to continue using the oil beyond its practical use.

Sampling and Wear Challenges

Lubrication oil reduces bearing friction, transfers heat, and safeguards components from wear and corrosion. However, impurities can adversely affect its ability to perform these functions. Air, water, unburnt particles, soot, and debris are common impurities that affect lubrication oil. Over time, these contaminants can render the lubricant ineffective. To identify and address these impurities, oil sampling and testing are essential. The most used test for identifying impurities is spectroscopy, which involves an inductively coupled plasma (ICP) instrument to measure the concentration of metals such as iron or copper in the oil. These metals may indicate wear on an engine due to abrasion between moving parts. However, the ICP instrument can only detect impurities that are less than 3-4 microns in size, which can be problematic since the most damaging particles are typically between 4-10 microns in size and may be missed by this method.

Spectroscopy Testing Limitations

Equipment wear can create harmful particles larger than 4 microns in size. To prevent this issue, experts recommend filtering oil down to 1 micron. However, some people mistakenly believe this method might hide potential problems caused by larger particles being continuously crushed between moving parts, leading to lower concentration trends of particulates. To avoid this problem, it is crucial to use additional tests such as particle counting, ferrous density analysis (ferrography), and patch microscopy to detect larger particles and measure the activewear in equipment. Relying solely on spectrographic data can result in inaccurate conclusions about the machine's health. Elemental spectrometers are devices designed to detect particles like iron (Fe) or silicon (Si) present in oil. However, these instruments may need help identifying particles outside their detection limits. This can happen if the particles are too large (above 10-15 microns) or small (below 3-4 microns). As a result, the user may fail to detect these harmful particles and can only observe the small ones. A spectrometer measures large particles ground between moving parts as Ppm concentration levels. Therefore, it is considered a lag indicator as it measures damage already occurring.

The Problem with Manufacturer Filters

Equipment users and laboratories relying on primary filter equipment from a manufacturer should be aware of the limitations of spectroscopy and the primary filter's capability to remove the particles that cause the most damage. The primary flow filters can only eliminate particles larger than 10-15 microns, whereas particles in the 4-10 microns size tend to get stuck between moving parts. The distance between these moving parts or the oil's film thickness is only 3-5 microns, so equipment operators must enforce stricter limits for wear metals to prevent further damage. All these factors lead to more frequent oil changes. Therefore, applying lower limits for "wear metal ppm" is crucial to ensure the equipment's longevity and performance.

Bypass filters are a Paradigm Shift

Advanced filtering systems, known as "high-purity" bypass filters, can remove contaminants as small as 1 micron. However, operators must adjust their approach to oil sampling, key indicators, and condemning limits. High-purity filter systems' ability to slow contamination trends is often misinterpreted as "masking" or "hiding" equipment wear. Operators who depend on a less capable manufacturer primary filter may need to be more accustomed to seeing these gradual trends, especially with extended oil hours, and might mistakenly interpret it as masking the

problem. To address this concern, a particle count test (ISO 4406) can be more effective in detecting the current serviceability of the oil. This test measures the most damaging particle sizes, ranging from four to greater than 14 microns. Additionally, the ferrography test, which measures the percentage of large particles and visually magnified pictures of the oil, becomes essential as it validates what a spectroscopy cannot. These additional tests measure particulates of the most damaging size (i.e., 4 to 10 microns) and provide contamination trends or a "lead" indicator since it measures these harmful particle sizes as they occur in the oil, helping to determine when to change it.

Combined, they allow operators to predict better the oil's serviceability rather than merely react to it. By adding an advanced filter system to the equipment and using a combination of tests, oil service intervals can be extended, even with higher than recommended spectroscopy concentration levels. In simpler terms, it removes the most damaging particles to sizes that fit within the film thickness between the moving parts (3-5 microns) or non-wear levels.

The Masking Concern Debunked

Installing a high-purity bypass filtering system is an excellent way to filter your equipment's oil to a level that is not typical with regular filters. If you solely rely on the manufacturer's primary filter, you might misinterpret the lower spectroscopy contamination trends as masking or hiding potential equipment wear. While a spectrograph test is essential, it only measures the after-effects of damage, leaving the equipment operators unaware of the damaging particles (4-10Microns) that can lead to frequent oil changes. In contrast, a high-purity bypass filter can remove harmful particles down to 1 micron, which makes spectroscopic readings less critical and more of an assurance of what a particle count tells you. Removing the most damaging particles within the film thickness (3-5 microns) can reduce wear metal to "non-wear" levels, resulting in improved preventive maintenance schedules, longer equipment life, less downtime, and reduced costs for equipment managers.