Volume flow rate measured in cubic meters per minute (or per
hour)
Mach number
is the ratio of the actual velocity at a given point to the
velocity of sound in the same gas at the conditions existing at
this point. These are known as local conditions.
Man way
An inspection cover or port in an air receiver tank.
MAWP
Maximum allowable working pressure. This data is found on the
pressure vessel nameplate and is the maximum pressure at which the
lowest set safety valve must be set (stamped).
Maximum operating
pressure
The highest operating pressure the system or component is
designed to withstand.
Mayonnaise
The oily condensate discharged by lubricated air compressors.
The name is derived from the appearance of the condensate. Under
normal conditions oily condensate should just be cloudy, like a
small amount of milk in a bucket of water. When a lubricated
compressor goes wrong, then the condensate becomes thick and
sticky. In fact almost identical in appearance to the name it has
been given.
Mechanical
efficiency
The ratio of the indicated power to shaft input.
Media
A mat of fibers that provide a barrier to particles entrained
in the flow of air or gas.
Media migration
Carry over of particles or contaminant from the filter or
other filter materials into the clean side of the air flow.
Medium
Is singular for media and is the material...paper, wire, cellulose or a combination... from which the filter element
is made and which does the actual filtration or separation.
Membrane dryer
Reduce dew point by passing compressed air through a bundle of
hollow membrane fibers; water vapor and a portion of the
compressed air then permeate the membrane walls and vent to
atmosphere
Mesh size
Mesh is the number of openings in a square inch of screen or
sieve. It is equal to the square of the number of strands of metal
or plastic screening per lineal inch. Standard US mesh screen # 16
equates to a 1.19 millimeter particle diameter, mesh size #40 is
0.42 millimeters.
Micron
Micrometer or one millionth of a meter; micron is sometimes
represented in filtration by the Greek letter µ (mu). A
micron is 0.000039". Contaminant particles are measured by micron
size and count.
Micron rating
A measurement applied to filters or filter media to indicate
the particle size at which suspended solids above that size will
be removed.
Millibar
A unit of atmospheric pressure equal to 1,000 dynes per sq.
cm. or about 1/32 in. of mercury.
Mineral oil
The most commonly used lubricating oil for compressors.
MMCFD
Millions of cubic feet per 24 hour.
Modulating control
Compressor controls will run the compressor at varying loads
to accommodate demand variations. Running a compressor at less
than full load results in a drop in compressor efficiency and thus
an increase in operating costs.
Modulating unload
The air compressor continues to run and air supply is matched
to the demand by partial unloading. This can be accomplished by a
regulator controlled floating inlet or by step unloading.
Moisture separator
A unit designed to separate condensate from the compressed air
stream.
Moisture trap
A device designed to enable accumulated liquids to be held for
draining in a compressed air system.
Molecular sieves
A solid adsorbent used for drying compressed air.
Molecular theory
All matter consists of molecules which are in constant motion,
but which are held together by molecular forces. In a solid the
molecules are closely packed and arranged in such a pattern that
the influence of the molecular forces is very strong. This gives
the solid its consistency and form. Molecular motion consists
largely of oscillations around points of equilibrium. In a liquid
the molecules are about as close as in a solid, but they are not
arranged in a lattice and the cohesive forces are weaker. The
molecules are more mobile in relation to each other, whereby the
characteristic liquid phase develops; the liquid accommodated
itself to the walls of the containing vessel, and its free surface
aligns itself horizontally in response to the force of gravity. In
a gas, however, the molecules are farther apart, and they move
freely about each other since the molecular forces are not as
strong. A gas therefore expands through space and mixes with other
gasses present. The total volume of the molecules in a gas is very
small in relation to the volume of the gas. A gas can therefore be
compressed into a small part of its original volume.
Mottling
In spray painting applications, blotches of metallic or mica
particles in a paint film caused by insufficient compressed air
MPCV
Combination minimum pressure valve and check valve.
MSDS
ACRONYM - MATERIAL SAFETY DATA SHEETS
Multistage axial
compressor
A machine having two or more impellers operating in series on
a single shaft and in single casing.
Multistage
centrifugal compressor
A machine having two or more impellers operating in series on
a single shaft and in single casing.
