Glossary F

Glossary F

Feet per minute, used as a measure of shaft speed instead of R.P.M. To convert R.P.M. to F.P.M. use the formula 0.262 x R.P.M x diameter (inches)=F.P.M.

Face, Inside:
The surface of the inner case which faces, and is usually in contact with, the fluid being sealed.

Face, Molded Toe:
See Face, Toe.

Face, Outside:
The surface of the seal case, perpendicular to the shaft axis, which is not in contact with the fluid being sealed.

Face, Rib Leading:
The face of the helix seal rib which is closest to the fluid side of the seal.

Face, Toe:
The annular surface of the spring retaining lip.

Face, Trim:
The seal inside lip surface when formed by a trimming operation.

Factor, pv:
An arbitrary term which is the product of face pressure and relative sliding velocity. The term is normally considered to provide some measure of severity of service or seal life.

A solid compounding ingredient which may be added usually in finely divided form, in relatively large proportions, to a polymer.

Finish, Shaft Surface:
See Texture, Shaft Surface.

Thin extrusions of the elastomer formed by extrusion at the parting lines in the mold cavity or vent points.

A rapid change in fluid state, from liquid to gaseous. In a dynamic seal, this can occur when frictional energy is added to the fluid as the latter passes between the primary sealing faces, or when fluid pressure is reduced below the fluid’s vapor pressure because of a pressure drop across the sealing faces.

Flex Point:
Region where the seal lip will flex when the seal element is stretched over the shaft.

Flex Thickness:
The thickness of the region that flexes when the seal element is stretched over the seal.

Flexibility, Cold:
Flexibility of a material during exposure to a predetermined low temperature for a specific length of time.

Fluid Side:
The side of the seal which in normal use faces toward the fluid being sealed.

A saturated polymer in which hydrogen atoms have been replaced with fluorine. It is characterized by excellent chemical and heat resistance.

The ability of a seal lip to maintain a dam when the shaft has vibrations or dynamic runout.

Force, Lip:
The radial force exerted by an extension spring and/or lip of a seal on the mating shaft. Lip force is expressed as force per unit of shaft circumference.

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