Manifold: a conductor with multiple connection ports, generally made from a
solid block of metal with internally drilled passageways to minimize the amount
of piping required.
Manifold (lube systems): two or more injectors in the same mounting assembly.
Master divider valve (lube systems): in a series-progressive system, the first
divider downstream from the pump; or the first divider value in a lubrication
zone. Output is directed to secondary divider valves and/or lubricant points.
Measuring valve (lube systems): component that dispenses a measured amount
of lubricant to a point of lubrication.
Mechanical seal: a dynamic interfacial spring-loaded mechanical device
consisting of a stationary face component in a housing and a rotating face
component on the shaft. Sealing takes place between the two flat sealing faces
perpendicular to the shaft axis.
Mechanical stability: see shear stability.
Median life: approximately five times the L10 (rating) life of a bearing.
Micron: 10-6 m; one millionth of a meter.
Mineral oil: originally, the name given to petroleum because it occurs as a
mineral, to distinguish it from oil obtained from animal and vegetable sources;
more commonly, a lubricant made from petroleum.
Mineral seal oil: a cut between kerosene distillate and gas oil, widely used as a
solvent or penetrating oil.
Mineral spirits: highly effective solvents derived from petroleum or coal (see
Mixed base crude/intermediate base crude: crude oil, neither predominantly
paraffinic or napththenic in character, found in the Mid-Continent and other
Mixed base grease: usually refers to a mixture of greases formulated with
sodium and calcium soaps, though other combinations are available; though
such compounding offers modest benefits, it is not sufficient to make them multipurpose
Mixed film/imperfect film lubrication: lubrication in which the lubricant film is
not continuous over the bearing area.
Mixed film lubrication – lubrication accomplished by a combination of a viscous
fluid compounded with boundary and/or extreme pressure additives. Example
– worm gears.
Mobility: analogous to fluidity, the property of a lubricating grease that permits
flow under pressure, as in centralized grease dispensing systems. Mobility is
evaluated by low-temperature testing that simulates winter field conditions.
Mold oil: oil that ensures easy separation of a ceramic, glass, metal or other
object from the mold in which it is cast (see form oil).
Molybdenum (“moly”) disulfide: often wrongly termed “molysulfide”; a dark
powder used as a dry film lubricant in oxidizing atmospheres, at temperatures of
up to 800°F, to reduce friction under boundary conditions. A natural material,
moly disulfide is processed to remove abrasives, produced in micronic particle
sizes and made available as a paste, an additive for greases, a dispersant in oil or
a bonded dry-film coating.
Motor: technically, an electric motor; in hydraulics, a device that converts fluid
power into rotary mechanical force (torque) and motion.
Motor oil/multi-grade oil: an engine oil that meets the requirements of more
than one SAE viscosity grade classification, formulated with viscosity index (VI)
improvers; “W” indicates winter grade.
MSDS: acronym for “Material Safety Data Sheet”, available for all raw materials
and products; includes handling, storage and waste treatment practices
recommended for safety.
Multi-purpose greases: greases with good mechanical shear stability, capable of
operating throughout a wide temperature range and functioning in the presence
of water, readily pumpable over long distances; such greases can be used in any
type of bearing served by a centralized system (see lithium base grease and
Multi-stage pump: centrifugal pumps with two or more impellers mounted on
the same shaft; the discharge from one impeller is conducted to the suction eye of
the next impeller, etc.
Multi-state compressor: compressor that directs air through a series of two or
more cylinders during compression; “inter-cooling” denotes cooling as the air
passes between cylinders.
Mutagenicity: tendency of a substance to cause genetic mutations under long term exposure.