Diesel Fuels & Diesel Fuel Systems
The service life of the fuel injection system, valves, pistons, rings, liners and bearings. Even when fuel is handled very carefully, foreign particles will find their way in during handling or storage. Foreign particles could be paint flakes, dust, sand, rust or microbiologic particles. •
Clean fuel is necessary for dependable engine performance. Engine filters protect the fuel injection pumps and nozzles and should never be removed or bypassed. The comparison in Figure 7 demonstrates the very tight clearance in the fuel system and the size of visible particles.
Sizes of Particles
Figure 7 Primary filters will extend engine filter and transfer pump life. Water and sediment traps can be included upstream of the transfer pump, but pump flow must not be restricted. Filter Micron Ratings Caterpillar specifies actual filter capability, rupture strength, the capacity for holding dirt, flow resistance, filter area, etc.
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Application and Installation Guide
Caterpillar does not specify filter or filter paper by micron rating. Micron ratings are easily confused for the following reasons: The test for micron ratings is not repeatable at different labs. One manufacturer may give a rating of 10 microns (0.00039 in.), another at 2 microns (0.000079 in.) and a third may rate a particular filter media (paper) at 15 microns (0.00059 in.). • There is no consistent relationship between micron rating and actual filtration efficiency. The entire filter needs to be tested, not just the media (paper). • The micron rating does not show what happens to a filter over time. The test provides no information about how a filter will stand up under continual use. Micron ratings are overemphasized; a 10-micron filter will not always stop a 10-micron particle. Many reputable filter manufacturing firms are drifting away from micron ratings to more conclusive tests. Smaller micron ratings are not necessarily better. •
If all other factors (area) were equal, a smaller micron number media (paper) has a severe drawback: it has less capacity before plugging and needs to be replaced more often. The size of the pores in the paper needs to be balanced against the costs of the filter replacements. Common questions are: ©2005 Caterpillar® All rights reserved.
