- The relationship between a moving body and the speed of sound
in that locality which can vary with temperature, altitude and
there fore pressure.
- A type of seal less pump that is pretty much limited to
pumping clean lubricating liquids. Similar in concept to a canned
- Uses magnetic materials rather than springs to keep the lapped
seal faces together. Limited to non corrosive fluids because of
- 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
- Another name for the hard face in a mechanical seal. It can be
either rotating or stationary.
- 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.
- 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.
- Used in mechanical seal designs to eliminate the need for a
- A breakage of the metal caused by the bending and flexing of a
metal part beyond its endurance limit.
- 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.
- 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.
- When one liquid mixes or blend with another liquid. Same as
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
- A single color light used with an optical flat to read seal
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Link to Mc Nally home page