Anatomy of an Oil Filter


That is the second a part of a sequence of “anatomy” classes inside Equipment Lubrication. On this challenge, the oil filter shall be examined to uncover its practical and efficiency traits. A number of different associated subjects may even be mentioned, together with finest practices for oil filter utilization, potential filter failure modes, components for correct filter choice and the right way to keep an put in filter.

By definition, an oil filter’s primary position is to cleanse oil from damaging contaminants inside a machine equivalent to an engine, transmission, hydraulic system and different oil-dependent methods. Within the case of automotive oil filters, canister-type filters are the most typical. This filter configuration was most definitely accountable for the superior efficiency of oil filtration expertise.

In 1922, Ernest Sweetland invented the primary oil filter gadget for cars. It was named the “Purolator,” which was quick for “pure oil later.” The spin-on filters widespread in as we speak’s automotive trade have been launched within the Fifties and have been nearly an ordinary by the early Nineteen Seventies.

Other than the automotive trade, oil filtration is an integral a part of gear inside all kinds of industries, together with aerospace, energy technology, oil refining, manufacturing, mining, and many others. Though most present oil filter designs are available in canister or cartridge varieties, a number of variations in measurement, filter media, dirt-holding capacities and movement preparations can be found. Because of this, it will be important that filters and filtration methods are chosen to satisfy the wants of the appliance and with price, efficiency, ease of use and environmental circumstances in thoughts.

Oil Filter Varieties

Oil filters will be characterised by the strategy by which the contaminants are filtered or the strategy by which the oil flows by means of the housing. One approach used to manage contamination in filters is thru surface-type media. That is the kind of filter utilized in cars. In depth-type filters, the filter media are designed to carry a lot greater ranges of contamination and supply a extra circuitous path for lubricant contaminants to grow to be trapped.

Different potential contamination management strategies embrace magnetic and centrifugal filtration. Magnetic filtration makes use of rare-earth magnets or electromagnets to draw and acquire ferrous particles because the oil passes by means of a magnetic flux area. Centrifugal filtration works by integrating a quickly rotating cylinder to provide a centrifugal pressure for contamination separation from the oil.

Oil filters may also be categorized by the oil movement design. As its identify implies, a full-flow filter will draw all the oil by means of the filter media. Then again, a bypass filter solely requires a fraction of the oil movement for enough movement charges inside the system. The applying’s oil movement and contamination management necessities will decide which design is the best choice. One other various is the duplex filter system, which incorporates two side-by-side filters in parallel to permit one of many filters to get replaced throughout uninterrupted operation.

With typical canister-type filters, it’s normal for oil to movement from the skin in. Which means that the oil travels by means of the cylindrical filter media from the outward-facing floor into the internal core. Nevertheless, in some instances the movement route is reversed, with the oil coming into the filter by means of the core and pushed outward by means of a singular pleat design. That is supposed to enhance movement dealing with and distribution in addition to scale back filter ingredient measurement.

Filtration Mechanisms and Filter Media

A filter’s main operate is to take away and retain contaminants as oil flows by means of the porous part known as the media. The media function beneath a number of forms of filtration mechanisms, together with:

  • Direct Interception and Depth Entrapment – Particle blockage on the media because of the particles being bigger than the taken passages inside the media.

  • Adsorption – The electrostatic or molecular attraction of particles between the particles and the media.

  • Inertial Impaction – Particles are impacted onto the filter media by inertia and held there by adsorption because the oil flows round.

  • Brownian Motion – This causes particles smaller than 1 micron to maneuver irrespectively of the fluid movement and ends in the particles being adsorbed by media in shut proximity. It’s a lot much less prevalent, particularly in viscous fluids.

  • Gravitation Results – These permit a lot bigger particles to settle away from fluid movement areas when there may be low movement.

As well as, filter media will be designed to seize particles by means of two distinct strategies:

  • Floor Retention – Contaminants are held on the floor of the media. This offers a chance for the contaminant to grow to be trapped because it is available in contact with the media floor.

  • Depth Retention – Contaminants are held both on the floor of the media or inside the labyrinth of passages inside the “depth” of the filter media. This creates a number of alternatives for contaminants to grow to be trapped.

The graph under reveals how depth-type filtration is extra environment friendly in capturing smaller particles when in comparison with surface-type filters. This may be attributed to the deeper media offering extra probabilities for the particles to be trapped together with the adsorptive and Brownian motion results being extra predominant in depth-type filters. Whereas these traits are useful, depth-type filters are inclined to have greater differential strain throughout the media because of the elevated movement restriction from the deeper filter media.

Particle measurement retention traits of

depth-type and surface-type filter media.

Filter Media Varieties and Grime-Holding Capability

Within the September-October 2012 challenge of Equipment Lubrication, Wes Money defined how the porosity of the filter media performs a job in how nicely the filter can retain captured particles. This is called the dirt-holding capability. As pore measurement goes down, to take care of a low differential strain throughout the media, the pore density should go as much as account for the oil quantity in touch with the floor. The filter depth and measurement additionally affect the dirt-holding capability. One other issue is the filter media materials. There are three main forms of filter media:

  1. Cellulose – Comprised of wooden pulp with giant fibers and an inconsistent pore measurement.

  2. Fiberglass (Artificial) – Comprised of smaller, man-made glass fibers with a extra constant pore measurement.

  3. Composite – Comprised of a mixture of cellulose and fiberglass materials.

Cellulose media are advantageous as a result of they will soak up some water contamination. Nevertheless, most of these media are inclined to fail extra quickly than artificial media in acidic and harsh oil circumstances. Nonetheless, the first motive artificial filter media are most well-liked is their extra constant porosity and smaller fiber measurement, which contributes to greater dirt-holding capability and longevity of the filter.

This instance of a depth-type filter has a component that requires

oil to cross by means of 114 millimeters of filter media

for max particle filtration. (Courtesy Triple R)

Understanding the Beta Score

Oil filters are rated by a method known as the beta ranking. In his Equipment Lubrication article “Understanding Filter Effectivity and Beta Ratios,” Jeremy Wright defined the methodology behind the beta ranking in additional element. In brief, the beta ratio is calculated by dividing the variety of particles bigger than a sure measurement upstream of the filter by the variety of particles of the identical measurement downstream of the filter. Each filter may have a number of beta ratios for various particle measurement limits equivalent to 2, 5 or 10 microns.

Greatest Practices for Oil Filter Utilization

Storage – Filters can fail lengthy earlier than they’re for use for his or her supposed objective. Subsequently, correct filter storage and dealing with are important. Guarantee filters are saved clear, cool and dry, and at all times observe the first-in/first-out rule.

Set up – Even when a filter set up appears easy and routine, seek advice from the producer’s suggestions for correct procedures. A basic mistake is over-tightening. Most suggestions recommend {that a} three-quarter flip after seal contact is perfect. Over- or under-tightening can inhibit the seal’s longevity and effectiveness. Verify that connections, seals and ducts are fitted appropriately and are freed from contaminants.

Avoiding Pre-fill – Generally, you don’t want to pre-fill your oil filters earlier than set up. In diesel engines, it’s endorsed {that a} pre-lube system be put in as a substitute in an effort to counteract modifications from dry-start circumstances.

Selecting Appropriately – Many filters and filter housings are designed to be interchangeable, so simply because a selected filter matches doesn’t imply it’s the appropriate filter. Ensure that every filter is changed with the proper filter. This may increasingly not essentially be the one discovered on the machine, as an incorrect filter might need been used over the past filter change.

Coaching – Correct coaching should be carried out for all personnel concerned with altering filters. Keep in mind, a process that appears easy to most individuals will not be for a brand new worker.

Filter Failure Modes

Channeling – Throughout excessive differential pressures, filter media passages can enlarge to a degree the place unfiltered oil can cross by means of with out an environment friendly contaminant seize. As well as, any particles that have been beforehand contained inside the filter according to the enlarged passage could now be let out.

Fatigue Cracks – In cyclic movement circumstances, cracks can kind inside the filter media, permitting a breach of oil to cross by means of unfiltered.

Media Migration – Media fibers can deteriorate and produce new contaminants made up of filter materials. This can be attributable to improper placement of the filter housing or an insufficient becoming of the filter, which might generate damaging vibrations. Embrittlement from incompatible oils or extraordinarily excessive differential pressures may also end in media disintegration.

Plugging – Throughout operation, filter media can grow to be totally plugged by exceeding the dirt-holding capability. Plugging can happen prematurely if extreme moisture, coolant or oxidative merchandise like sludge are current.


of lubrication professionals say filter plugging is the failure mode seen most often in oil filters at their plant based mostly on a current survey at

Elements for Correct Oil Filter Choice

Structural Integrity – Arguably essentially the most vital issue, structural integrity pertains to a filter’s capacity to forestall the passage of oil by means of an unfiltered movement path. The Worldwide Group for Standardization (ISO) has established procedures for testing fabrication integrity, materials compatibility, finish load and movement fatigue. These exams can reveal defects equivalent to improper sealing of seams and finish caps or breaks within the media from high-flow circumstances, in addition to the results of excessive temperatures on the filter ingredient.

Contamination (Grime-Holding) Capability – This refers back to the quantity of contaminants that may be loaded onto the filter earlier than the filter’s effectivity is restricted.

Strain Loss – This includes the general differential strain misplaced from the filter’s placement on the system. The strain loss shall be influenced by the filter media’s porosity and floor space.

Particle Seize Effectivity – That is the general effectiveness of the filtration mechanisms inside the filter media to extract and retain contaminants from the oil.

System/Atmosphere – The traits of the system and surroundings by which the filter shall be put in should be thought-about, together with the contamination expectations, movement charges, location, vibration, and many others.

Sustaining Put in Filters

The easiest way to forestall filters from reaching their dirt-holding capability is to keep away from contaminants within the system from the start. The less exterior contaminants that ingress, the less contaminants which can be generated internally (particles produce particles). Use the next tips to take care of put in filters:

  • Guarantee correct breathers are put in to forestall contaminants and moisture from getting into the system.

  • Preserve seals and cylinders clear and dry by utilizing applicable wipers and boots.

  • Choose the suitable oil grade and additive package deal to counter contaminant ingression and inside friction.

Analyzing the Filter

A filter not solely is a entice for the machine’s undesirables but additionally a focus of clues as to what’s occurring inside the machine. Particles inside the oil could also be so extremely diluted that sensible evaluation can grow to be a frightening problem. Nevertheless, the particles trapped within the filter could also be so plentiful that they are often simply seen to the bare eye.

Metallic contaminants are a main indication of a difficulty inside the machine. Though some quantity of metallic contaminants will be anticipated, an uncommon quantity needs to be acknowledged by trending the filter’s visible look after every oil change. Slicing open the filter and suspending a robust magnet over it might assist in pulling out the metallic contaminants to extra simply distinguish them.

If the machine is suspected to have a difficulty, the filter shouldn’t be discarded, as this is able to be much like throwing away key items of proof. Keep the filter in the identical situation as when it was eliminated and have it analyzed by the producer or a laboratory.

Filter Disposal

Oil filters are usually not designed to be dumped into any wastebasket. Rising laws by the Environmental Safety Company dictate correct filter disposal. Whereas every kind of oil filter could have its personal necessities, widespread practices embrace oil draining, crushing or incinerating the filter. Many disposal providers or filter distribution facilities will settle for used oil filters at little or no price.



Fitch, E.C., An encyclopedia of contamination management, Eighties

Fitch, E.C., “How you can Choose Fluid Energy Filters,” The BFPR Journal, 1979, 12, 3, 197-201

Erosion Management, Gear World Journal, December 1991

Filtration Handbook, PTI Applied sciences Inc., 1990

Pall Company, Ultipleat SRT Filter Brochure, Nov. 2007

Triple R Oil Cleansing Merchandise, Product Brochure, 2013

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