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RUNOUT (SHAFT)
Same as Gyration. When expressed in inches alone or
accompanied by abbreviation “TIR” (total indicator reading), it
refers to twice the radial distance between shaft axis and axis of
rotation.
SEAL
Any device used to prevent the passage of a gas or liquid.
SERVICE
Operating conditions to be met.
SHAFT
Rotating member within cylinder; not in contact with walls.
SHRINKAGE
Decreased volume of unit caused by air drying after immersion
in fluid.
SIZE, ACTUAL
Actual dimensions of the O-Ring, including tolerance limits.
SIZE, NOMINAL
Approximate size of O-Ring in fractional dimensions.
SPECIFIC GRAVITY
The ratio of the weight of a given substance to the weight of an
equal volume of water at a specified temperature.
SPRUE MARKS
Marks left on the surface of a rubber part, usually elevated, after
removal of the sprue.
SQUEEZE
Cross-section diametral compression of O-Ring between bottom
surface of the groove and surface of other mating metal part in
the gland assembly.
STATIC
Stationary application such as a gasket.
STATIC SEAL
Seal designed to work between parts having no relative motion.
STRESS
Force per unit of original cross-sectional area required to stretch
a specimen to a stated elongation.
SUN CHECKING
Surface cracks, checks, or crazing caused by exposure to direct
or indirect sunlight.
SWELL
Increased volume of unit caused by immersion in fluid.
TEMPERATURE RANGE
Lowest temperature at which rubber remains flexible and highest
temperature at which it will function.
TENSILE STRENGTH.
Force in pounds per square inch required to cause the rupture of
a specimen of a rubber material.
TERPOLYMER
A polymer consisting of three different monomers chemically
combined.
THIOKOL
A synthetic rubber of the polysulfide type.
THERMAL EXPANSION
Expansion caused by increase in temperature. May be linear
and volumetric.
TORQUE
The turning power of a shaft.
TRIM
The process involving removal of mold flash.
TRIM CUT
Damage to mold skin or finish by too close trimming.
UNDER-CURE
Degree of cure less than optimum. May be evidenced by
tackiness, loginess or inferior physical properties.
VOIDS
The absence of material or an area devoid of materials where
not intended.
VISCOSITY
A manifestation of internal friction opposed to mobility. The
property of fluids and plastic solids by which they resist an
instantaneous change of shape, i.e, resistance to flow.
VOLUME CHANGE
Change in volume of a specimen which has been immersed in a
designated fluid under specified condition of time and
temperature. Expressed as a percentage of the original volume.
VOLUME SWELL
Increase in physical size caused by the swelling action of a
liquid.
VULCANIZATION
A thermo-setting involving the use of heat and pressure and
which results in greatly increased strength and elasticity of
rubber-like materials.
WIDTH
Radial dimension. For packing rings or sets the term “packing
space” is preferred.
WIPER RING
A ring employed to remove excess fluid, mud, etc., from a
reciprocating member before it reaches the packing.