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Glossary S


Glossary S

Scoop Trim:
A trimmed surface which is concave.

Scoring:
A type of wear in which the working surface is grooved.

Scratch:
A shallow discontinuity in the seal material whereby no material is removed.

Scuffing:
Metal surface degradation resulting from adhesive wear.

Seal, Bonded:
Design feature of a type of radial lip seal. The heel of the sealing element is attached (bonded) to the seal case by an adhesive during the molding operation.

Seal, Birotational:
A rotary shaft seal which will seal fluid regardless of direction of shaft rotation.

Seal, Dynamic:
A seal which has rotating, oscillation, or reciprocating motion between it and its mating surface, in contrast to stationary-type seals, such as a gasket.

Seal, Helix:
An elastomeric hydrodynamic lip seal having helical ribs on the outside lip surface.

Seal, Hydrodynamic:
A dynamic sealing device which utilizes the viscous shear and inertia forces of the fluid, imparted by a helically grooved O ribbed seal lip, to generate a pressure differential that opposes fluid flow.

Seal, Lip:
An elastomeric seal which prevents leakage in dynamic and static applications by reason of controlled interference between the seal lip and the mating surface.

Seal, Mechanical:
Any material or device that prevents or controls the passage of matter across the separable members of a mechanical assembly.

Seal, Radial:
A seal which exerts radial sealing pressure in order to retain fluids and/or exclude foreign matter.

Seal, Radial Lip:
A type of seal which features a flexible sealing member referred to as a lip. The lip is usually of an elastomeric material. It exerts radial sealing pressure on a mating shaft in order to retain fluids and/or exclude foreign matter.

Seal, Shaft:
Generally considered to be a lip seal or an oil seal but a broad definition could include any sealing device mounted on a shaft or sealing a shaft.

Seal, Split:
A seal which has its primary sealing element split, approximately parallel with the shaft axial centerline. Typically used where conventional installation methods are impractical or impossible.

Seal, Unirotational:
A seal designed for applications having a single direction of shaft rotation.

Seal, Unitized:
A seal assembly in which all components necessary for accomplishing the complete sealing function are retained in a single package.

Sealer, Case OD:
A coating applied to the case O.D. to prevent leakage between the seal case and the housing bore.

Sealing Capacity:
The difference in leakage rates of a hydrodynamic seal and a nonhydrodynamic seal when tested on a shaft with a spiral groove that tends to pump oil out of the sump when the shaft is rotating.

Section, Flex:
The portion of a seal lip which is bounded by the head and heel section of a lip seal. Its primary function is to permit relative motion between the seal lip and the case.

Section, Head:
The portion of a lip seal which is generally defined by the inside and outside lip surfaces and the spring groove.

Section, Heel:
The portion of a lip seal which is attached to the seal case and bounded by the flex section and the outside face.

Set, Compression:
The deformation which remains in rubber after it has been subjected to and released from a specific percent compression for a definite period of time at a prescribed temperature. Compression set measurements are for the purpose of evaluating creep and stress relaxation properties of rubber.

Set, Permanent:
The residual unrecoverable deformation in an elastomeric part after the load causing the deformation has been removed.

Shaft Diameter:
The outside diameter of the shaft at the location where the seal is mounted.

Shaft Finish:
The relative roughness, usually expressed in micro inches, of the outside diameter of the shaft. The smaller the number, the smoother the finish.

Side, Air:
The side of a seal which in normal use faces away from the fluid being sealed.

Silicone:
A type of elastomer having a basic polymer of dimethyl polysiloxane, with various attached vinyl or phenyl groups.

Slant, Seal:
The difference between the maximum and minimum axial dimensions from the seal-lip contact linen to the outside face of the case.

Sleeve, Wear:
A replaceable metal ring, generally used in assemblies to eliminate expensive shaft replacement caused by grooving that may occur at the seal-shaft interface.

Slinger:
A washer-like device used for imparting radial momentum to a liquid in order to keep the latter away from the sealing interface. Often incorporated into a wear sleeve.

Speed, Surface:
The linear velocity calculated from the shaft rotational speed using the nominal shaft diameter.

Spiral Trim:
A trimmed surface which has a spiral pattern.

Spring Axial Position:
The axial distance between the projected intersection of the inside and outside lip surfaces and centerline of the spring coil diameter (center plane of the spring) with the spring in position and the seal located on the shaft.

Spring, Finger:
A spring consisting of a multiple number or cantilevered elements located circumferentially on a ring. It can be designed to produce either a radial or an axial force.

Spring, Garter:
A helically coiled wire with its ends connected to form a ring. It is used in tension for maintaining a radial sealing force between the sealing element of a radial lip seal and a shaft.

S.T.B.M.:
Shaft to Bore Misalignment, the amount by which the shaft is off center, with respect to the bore’s center.

Stability, Dimensional:
The ability to retain manufactured shape and size after having experienced the combination of operating stresses and temperatures.

Step Trim:
A trimmed surface having a discontinuity perpendicular to the contact line.

Stick, Slip:
A friction related phenomenon where the sealing element tends to adhere and rotate with the shaft surface momentarily until the elastic characteristics of the sealing element overcome the adhesive force, causing the seal lip to lose contact with the rotating shaft long enough to allow leakage. This cycle repeats itself continuously and is normally associated with non-lubricated/boundary lubricated conditions.

Sump Temperature:
The temperature of the fluid contained within the machinery sump.

Surface, Contact:
The portion of the seal lip which circumferentially contacts the shaft to form the seal-shaft interface.

Surface Contamination:
Foreign matter on the seal surface.

Surface, Inside Lip:
The inside truncated conical surface of the lip, the minor diameter of which terminates at the contact point.

Surface, Outside Lip:
The outside truncated conical surface of the lip, the minor diameter of which terminates at the contact point.

Surface Speed:
The linear velocity calculated from the shaft rotational speed, using the nominal shaft diameter.

Surface, Trimmed Seal:
The lip surface formed by a knife cutting operation to develop the contact line.

Synthetic Rubber:
Synthetic elastomers made by polymerization of one or more monomers.

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