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Clearing the air about flters An examination of the components that keep vehicles running cleaner By Bob Weber and Dan Pike To operate at peak efciency, vehicles need clean flters to prevent contaminants from entering fuel, engine or air conditioning systems. Particles can cause poor performance and shorten the lifespan of the vehicle. When these flters should be replaced depends on many factors, such as vehicle maker’s recommendations and the environment in which the flter operates. Terefore, routine inspection of the flters’ condition is crucial. Te following article on flters was compiled by Bob Weber, a contributing writer for our sister publication, Auto Service Professional, and writen by Dan Pike, group executive, Filter Manufacturers Council (FMC) and vice president, membership and members services, Automotive Afermarket Suppliers Association.
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t’s time to clear the air about flters — those automotive components which keep your customers’ vehicles running clean. Here is a brief overview of motor vehicle fltration products, which include flters for the engine, oil, cabin air and transmission.
Filters: It’s what’s inside that counts Any discussion of motor vehicle flters begins with flter media — the material inside the flter which captures dirt and foreign particles. Filter manufacturers use many diferent types of media for various fuids and environmental extremes. Te most common used flter media are cellulose-based and glass. Cellulose media is manufactured with fbers of various sizes. On the top layer of the media, the fbers are fufed up, rather than compacted down. When fuid and contaminants pass through the media, many particles collect on the fufy fbers on the surface and don’t travel further into the flter. Glass media was developed to be utilized in hydraulic systems because it has low fow restriction at high fltration efciencies. Tese low-fow resistance properties are benefcial in hydraulics where cold oil is being forced through the media and when fltration in the 3 to 5 micron range is desired. Glass media has a drawback regarding capacity. Typically, glass media has the same pore size and same fber diameter through the entire sheet. Te media can be manufactured to be very efcient, but then it is so tight that it has very litle life or capacity. Synthetic media is making inroads in replacement flters. In most lube, fuel and air flter applications, cellulose media remains the beter choice. As with glass, the reason largely relates to capacity, or flter life. A brief description of the
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There’s more to a flter than meets the eye. The type of media used substantially affects the flter’s performance.
fltering process illustrates this. Te process of fuids and contaminants collecting on the fufy fbers of cellulose flter’s surface is called “adsorption.” Te particles adhere to the surface fbers and don’t travel farther into the flter. The more adsorption a media applies, the more small particles can be separated before they reach the small pore spaces on the screen side of the media. Tis keeps these small particles from plugging the media. Cellulose media typically is thicker than synthetic. Te thicker the media is, the more time the particles spend traveling through it. Each time the fuid changes direction around a fber, the momentum keeps particles traveling in the same direction they were going and they are driven into the fbers. Tis particle separation is called “impingement.” As with adsorption, the more impingement that a media applies, the more particles are separated without plugging the tight pore space on the screen side. Synthetic media does separate some particles with adsorption and impingement, but the smooth fbers can’t hold the particles in place. Ofen they are washed of with the fuid traveling through the media. Synthetic media primarily uses the particle separation technique called “direct interception.” Direct interception is simply separating particles by passing the fuid through pore spaces that are small enough to catch them. However, once all pores are flled with the contaminant, the flter is plugged and its life is over. Because cellulose media is beter at adsorption and impingement, it can remove more contaminants than glass or synthetic media without plugging pore spaces. Can a synthetic media be created with the benefts of cellulose
MTD May 2014
