Glossary of Pump Terms: M
Mach number
The relationship between a moving body and the speed of sound
in that locality which can vary with temperature, altitude and
there fore pressure.
Magnetic drive
A type of seal less pump that is pretty much limited to pumping
clean lubricating liquids. Similar in concept to a canned pump.
Magnetic seal
Uses magnetic materials rather than springs to keep the lapped
seal faces together. Limited to non corrosive fluids because of
the magnets.
Magnetite
Iron oxide ( Fe3O4). A protective coating the forms on iron pipe
to prevent further rapid corrosion. Usually black or maroon in
color. Can be very destructive to mechanical seal components until
the oxide stabalizes. We often find these iron pipes in new hot
water systems
Mating ring
Another name for the hard face in a mechanical seal. It can be
either rotating or stationary.
Mean Diameter
The middle diameter. Usually refers to the center of the seal
face. The term is commonly used with metal belows seals to describe
the middle diameter of the bellows plate.
Mechanical seal
A positive sealing device used to seal all fluids (liquids and
gases). The primary seal is a set of lapped seal faces that are
installed perpendicular to the shaft.
Metal bellows
Used in mechanical seal designs to eliminate the need for a dynamic
elastomer.
Metal fatigue
A breakage of the metal caused by the bending and flexing of
a metal part beyond its endurance limit.
Micro Organisms
Used in a variety of chemical processes. Can cause corrosion
of stainless steel if they penetrate the passivated layer and
attack the carbon content of the stainless steel.
Minimum flow
A condition that can cause excessive heat inside the pump volute.
A temperature rise of 10?C (18?F) across the operating pump is
considered excessive. Normally caused by throttling a pump discharge
valve.
Miscible
When one liquid mixes or blend with another liquid. Same as soluble.
Modulus of elasticity
Refers to the stiffness of the material. The higher the modulus
the stiffer the shaft. Most pump shafts have similar modules numbers.
Also called Young's modulus. The relationship of stress to strain.
If seal faces have a high modulus they are less likely to distort
under pressure.
Moment of inertia
Referring to rotation about an axis. In the pump business it
refers to a formula that describes the shape of the shaft. A solid
shaft would have a different moment of inertia than a hollow shaft.
Monochromatic light
A single color light used with an optical flat to read seal face
flatness.
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