Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/136253
LESSONS IN LUBRICATION Best Practices for Oil Filter Usage This example of a depth-type filter has an element that requires oil to pass through 114 millimeters of filter media for maximum particle filtration. (Courtesy Triple R) chances for the particles to be trapped along with the adsorptive and Brownian movement effects being more predominant in depthtype filters. While these characteristics are beneficial, depth-type filters tend to have higher differential pressure across the media as a result of the increased flow restriction from the deeper filter media. Filter Media Types and Dirt-Holding Capacity In the September-October 2012 issue of Machinery Lubrication, Wes Cash explained how the porosity of the filter media plays a role in how well the filter can retain captured particles. This is known as the dirt-holding capacity. As pore size goes down, to maintain a low differential pressure across the media, the pore density must go up to account for the oil volume in contact with the surface. The filter depth and size also influence the dirt-holding capacity. Another factor is the filter media material. There are three primary types of filter media: 1.Cellulose — Comprised of wood pulp with large fibers and an inconsistent pore size. 2.Fiberglass (Synthetic) — Comprised of smaller, man-made glass fibers with a more consistent pore size. 3.Composite — Comprised of a combination of cellulose and fiberglass material. Cellulose media are advantageous because they can absorb some water contamination. However, these types of media tend to fail more rapidly than synthetic media in acidic and harsh oil conditions. Nevertheless, the primary reason synthetic filter media are preferred is their more consistent porosity and smaller fiber size, which contributes to higher dirt-holding capacity and longevity of the filter. Understanding the Beta Rating Oil filters are rated by a technique called the beta rating. In his Machinery Lubrication article "Understanding Filter Efficiency and Beta Ratios," Jeremy Wright explained the methodology behind the beta rating in more detail. In short, the beta ratio is calculated by dividing the number of particles larger than a certain size upstream of the filter by the number of particles of the same size downstream of the filter. Every filter will have multiple beta ratios for different particle size limits such as 2, 5 or 10 microns. 52 | May - June 2013 | www.machinerylubrication.com Storage — Filters can fail long before they are to be used for their intended purpose. Therefore, proper filter storage and handling are essential. Ensure filters are kept clean, cool and dry, and always follow the first-in/first-out rule. Installation — Even if a filter installation seems simple and routine, refer to the manufacturer's recommendations for proper procedures. A classic mistake is over-tightening. Most recommendations suggest that a three-quarter turn after seal contact is optimal. Over- or under-tightening can inhibit the seal's longevity and effectiveness. Confirm that connections, seals and ducts are fitted appropriately and are free of contaminants. Avoiding Pre-fill — In most cases, you do not want to pre-fill your oil filters before installation. In diesel engines, it is recommended that a pre-lube system be installed instead in order to counteract changes from dry-start conditions. Choosing Correctly — Many filters and filter housings are designed to be interchangeable, so just because a particular filter fits doesn't mean it is the correct filter. Make sure each filter is replaced with the right filter. This may not necessarily be the one found on the machine, as an incorrect filter might have been used during the last filter change. Training — Proper training must be conducted for all personnel involved with changing filters. Remember, a task that seems straightforward to most people may not be for a new employee. Filter Failure Modes Channeling — During high differential pressures, filter media passages can enlarge to a point where unfiltered oil can pass through without an efficient contaminant capture. In addition, any particles that were previously contained within the filter in line with the enlarged passage may now be set free. Fatigue Cracks — In cyclic flow conditions, cracks can form within the filter media, allowing a breach of oil to pass through unfiltered. Media Migration — Media fibers can deteriorate and produce new contaminants made up of filter material. This may be caused by improper placement of the filter housing or an inadequate fitting of the filter, which can generate damaging vibrations. Embrittlement from incompatible oils or extremely high differential pressures can also result in media disintegration. Plugging — During operation, filter media can become fully plugged by exceeding the dirt-holding capacity. Plugging can occur prematurely if excessive moisture, coolant or oxidative products like sludge are present. Factors for Proper Oil Filter Selection Structural Integrity — Arguably the most critical factor, structural integrity relates to a filter's ability to prevent the passage of oil through an unfiltered flow path. The International Organization for Standardization (ISO) has established procedures for testing fabrication integrity, material compatibility, end load and flow fatigue. These tests can reveal defects such as improper sealing of seams and end caps or breaks in the media from highflow conditions, as well as the effects of high temperatures on the filter element. Contamination (Dirt-Holding) Capacity — This refers to the