- Elements that attack carbon. Fluorine, bromine, chlorine,
astatine and iodine.
- A seal face either rotating or stationary. The most common
materials are silicone carbide, ceramic, tungsten carbide,
Stellite, Ni-resist. The hard face must be the wider seal
- Vibtrating in harmony with something near by. This can be a
big problem for bearings in stationary or non running
- A nickel rich, corrosion resistant metal used for mechanical
seal springs and metal bellows because it is not sensitive to
chloride stress corrosion.
- The equivalent height of the liquid. 20° C. water is used
as the standard where 10 meters (33.9 ft.) of water equals one
atmosphere (14.7 psi. or 1 bar). The term head is used instead of
pressure in the centrifugal pump business.
Helium Light Band
- A method of measuring seal face flatness. One helium light
band equals 0.0000116 inches or 0.3 microns. Seal faces are
normally lapped to within three helium light bands of
- 33,000 foot pounds per minute. A common method of measuring
- A method of reducing mechanical seal face loading by reducing
the seal face closing area.
- Occurs any time pressure acts on a seal face area. Force times
distance divided by time is a measurement of work done.
- A petroleum product consisting of hydrogen and carbon.
- Generated at the seal faces because, for all practical
purposes, liquid is not compressible.
- Special geometric features on the seal face that provide lift
by taking advantage of the rotation of one seal face upon the
- A premature fatigue of metal caused by the presence of free
hydrogen. This is a major cause of ceramic breakage in hot water
seal applications, and bearing fatigue if moisture penetrates into
the bearing case.
- An ion formed by the transfer of a proton from one molecule of
water to another. Used to determine the pH of a substance. Each
step increases by a factor of ten.
- Maintains a controlled gap between the seal faces by balancing
the open and closing forces. There is a small amount of leakage
across the faces when the shaft is rotating. Used in some
compressor applications, but not very practical for the chemicals
found in the process industry.
- The delay or lag that causes seal faces to open.
Link to the Mc Nally home page