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Filtration Glossary of Terms


Anti-Drain Gasket/Valve Prevents oil from flowing back out of the oil filter, through the inlet holes, when the engine is shut off.
Absolute Rating Particle size in micrometers removed at a given efficiency under a manufacturer’s defined test condition.
Absorption The process of a fluid being taken into the pores of media.
Axial seal (Air) Utilize a gasket to maintain a seal on the outlet end of the air cleaner housing.
Beta Ratio The ratio of the number of particles of a given size and larger upstream of a filter to the number of particles of the same size and larger downstream.
Bottom Assembly Assembles tapping plate and bottom ring.
Bottom Ring Provides a groove for the sealing gasket and a flange for lockseaming to the filter body.
Bubble point Pressure drop in inches of water required to expect the first steady stream of bubbles from a horizontal disc of wetted filter medium, or a filter cartridge immersed in liquid.
Bubble point Test A common, nondestructive method used to test the integrity of cartridge construction to compare relative porosities of filter media or to monitor product consistency as a quality control method.
Capacity The amount of contaminant that will be collected on a filter before specified restriction level is reached.
Center tube Provides structural support to the center of the media to prevent media collapse.
Collapse Pressure Pressure across a filter cartridge, great enough to cause it to collapse.
CFM Measurement of air flow in cubic feet per minute.
Dust Concentration Expresses the mass of dust in a specified volume of air.
Dust Holding Capacity The weight of a contaminant fed to the filter during a test to reach a predefined Terminal pressure drop.
End Cap / End Disks Encloses the filtration media on its ends.
External Gasket Creates seal with engine mounting base when installed.
Filtration Efficiency That fraction of suspended particles retained by the filter.
Filtration The ability of the filter medium to remove particles from the fluid stream
Filter Body / Can   Outer shell of the filter
Filter Life The duration, measured in time or volume, that a filter can operate effectively between replacement and / or cleaning.
Filter Cartridge Assembly consisting of the filter media, end disks/cap, adhesive and centertube.
Flow Rate Measure of the amount of fluid passing through the filter. This is always a variable of filter area, porosity, contamination and differential pressure.
Media Material that removes contaminants
Media Migration Contamination of the effluent by fibers or other material of which the filter is constructed.
Non-Woven A porous web or sheet produced by mechanically, chemically or thermally bonding together polymers, fibers or filaments.
One-Stage Air Cleaner Dust removal system for intake air with a filter element only.
Overall Efficiency (Air) The percentage of contaminant removed from intake air.
Permeability The property of a filter medium that permits a fluid to pass through under a pressure differential.
Pore Size Filters are rated according to the size of particles they can remove. Particles which are bigger than indicated pore size, are removed. Smaller particles pass through the media. The size of particles is measured in micro-meters or "microns" one micron being equal to one-millionth of a meter or one-thousandth of a millimeter.
Pressure drop Pressure on the clean side minus pressure on the dirty side. It can also be called as the difference in pressure between two points, which is usually measured between inlet and outlet service of the filter housing.
Primary Air Filter / Outer Element Element that removes around 99.9% of the air’s dust.  The air flows through the primary filter first.
Radial Seal (Air) Utilizes urethane end caps to maintain a seal on the inner diameter of the filter and the outside area of the outlet tube.
Relief Valve / Bypass Valve Relieves excess differential pressure.
Restriction   Resistance to flow.
Retainer / Spring Exerts pressure on the filter cartridge to the bottom assembly, maintaining an internal seal.
Safety (Secondary) Air Filter / Inner Element Optional filter that protects the engine during service of the primary filter and in case of a leak in the primary filter.
Tapping Plate   Portion of the filter that contains the threads.
Two-Stage Air Cleaner Dust removal system for intake air with a built-in pre-cleaner and an element.
Upstream Side The feed side of the filter
Viscosity A measure of the resistance to flow of a liquid. Viscosity of a liquid varies appreciably with changes in temperature.
Filtration   Lubricants
Coolant   Gasket Maker
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