Magnetic

A separator that uses a magnetic field to attract and hold ferromagnetic particles.

Magnetic filter

A filter element that, in addition to its filter medium, has a magnet or magnets incorporated into its structure to attract and hold ferromagnetic particles.

Magnetic plug

Strategically located in the flow stream to collect a representative sample of wear debris circulating in the system: for example, engine scarf, bearing flakes, and fatigue chunks. The rate of buildup of wear debris reflects degradation of critical surfaces.

Manifold

A filter assembly containing multiple ports and integral relating components, which services more than one fluid circuit.

Manifold filter

A filter in which the inlet and outlet port axes are at right angles, and the filter element axis is parallel to either port axis.

Media migration

Material passed into the effluent stream composed of the materials making up the filter medium.

Medium

The porous material that performs the actual process of filtration. The plural of this word is "media".

Metal oxides

Oxidized ferrous particles, which are very old or have been recently produced by conditions of inadequate lubrication. Trend is important.

Micron

A unit of length. One Micron = 39 millionths of an inch (.000039"). Contaminant size is usually described in microns. Relatively speaking, a grain of salt is about 60 microns and the eye can see particles to about 40 microns. Many hydraulic filters are required to be efficient in capturing a substantial percentage of contaminant particles as small as 5 microns. A micron is also known as a micrometer, and exhibited as um

Microscope method

A method of particle counting which measures or sizes particles using an optical microscope.

Mineral oil

Oil derived from a mineral source, such as petroleum, as opposed to oils derived from plants and animals.

Miscible

Capable of being mixed in any concentration without separation of phases; e.g., water and ethyl alcohol are miscible.

Moly

Molybdenum disulfide, a solid lubricant and friction reducer, colloidally dispersed in some oils and greases.

Multi-grade oil

An oil meeting the requirements of more than one SAE viscosity grade classification, and may therefore be suitable for use over a wider temperature range than single-grade oil.

Multi-pass or re-circulation test

Filter performance tests in which the contaminated fluid is allowed to re-circulate through the filter for the duration of the test. Contaminant is usually added to the test fluid during the test. The test is used to determine the Beta-Ratio (q.v.) of an element.