Industrial seal self study guide - SKF.com

Glossary of Seal Terms (cont...)
Diameter – A straight line segment passing
through the center of a figure, especially of a circle
or a sphere.
Diameter, Trimmed Lip – The lip diameter in the
free state (no spring) developed by knife trimming
the molded portion of the sealing element to form
the contact line.
Diamond Burnishing – A method of shaft surface
finishing in which the burnishing medium moves
axially.
Double Lip – Use of two sealing elements. One is
usually spring loaded, the other not. However, can
also have two spring loaded lips. Can be opposed
or in same direction.
Duralip - SKF’s special nitrile compound for
extreme abrasion resistance. Recommended
where scale, sand, grit, dirt or other highly
abrasive materials are present.
Duratemp – A special compound based on hydrogenated
nitrile (HNBR) Duratemp offers improved
tensile strength and resistance to heat, abrasion,
hardening in hot oil, ozone and weathering effects.
Dynamic Run-Out (DRO) – The amount by which
the shaft does not rotate around its true center.
Dynamic Seal – A seal which has rotating,
oscillating, or reciprocating motion between it and
its mating surface, in contrast to a stationary-type
seal, such as a gasket.
DIN – “Deutcshes Institute fur Normung” German
standards organization that is a member of
International Standards Organization (ISO).
Eccentricity, Lip I.D. – See: variation, radial wall.
Eccentricity, Shaft – The radial distance which the
geometric center of a shaft is displaced from the
axis of shaft rotation.
Elastomer (Lip Material) – An elastic rubberlike
substance, such as natural or synthetic rubber.
End-Play – A measure of axial movement
encountered or allowed, usually in reference to
the shaft on which the seal lip contacts.
EP lubes – “Extreme Pressure” lubricants which
contain additives to increase the strength of the
lubricant film. These additives can include sulfur,
chlorine, or phosphorus compounds that can attack
the sealing materials.
Exclusion – The prevention of dirt, water and
contaminants from entering the bearing cavity.
Flange – A protruding rim or edge used to
strengthen an object or hold it in place.
Flinger – Synonym: slinger.
Fluid Side – Side of the seal which normally
faces the fluid being sealed.
Fluoroelastomer – A saturated polymer in which
hydrogen atoms have been replaced with fluorine.
It is characterized by excellent chemical and heat
resistance.
FPM – Feet per minute; used as a measure of
shaft speed instead of rpm. To convert rpm into
fpm, use the formula: .262 x rpm x shaft diameter
(inches) = fpm.
Garter Spring – A Helically coiled spring wire with
its ends connected to form a ring. It is used for
maintaining a sealing surface between the sealing
element and a sealing surface.
Glass Bead Blasting – A method of shaft surface
finishing in which the shaft surface dimples.
Grinding Wheel-To-Shaft-Ratio – A number ratio
between grinding wheel rpm and shaft rpm. The
whole number is proportionate to the number of
lead grooves formed in the shaft. For example, at
a 2 to 1 ratio, one groove on the grinding wheel
will form two lead grooves on the shaft surface.
Groove, Spring – A depression formed in the
head of the section of the seal. It is generally
semicircular in form and serves to accommodate
and locate the garter spring.
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