The following is a brief explanation of some commonly used seal related terminology.

Cryogenic: Extremely low temperature (less than -250 deg F) applications.

Dynamic: Seal applications in which parts are moving, that is rotating, reciprocating or both.

Elastomer: An elastic polymer, rubber like.

Extrusion Gap: The opening between the outer shaft diameter and the housing bore through which excessive pressure could push the seal material.

Flange: A thin section radial extension on a seal, usually from the heel side, used to clamp the seal and prevent rotation.

Frictional Load: The amount of frictional force applied to dynamic system by the seal. This is usually calculated as “break away” and “running” friction.

Gland: The seat in which the seal is mounted. This can be a groove in a shaft for a piston seal or a housing counterbore for a rod seal.

Hastelloy®: A nickel based alloy that has higher corrosion resistance than 302 and 316 stainless steel.

Heel: In a spring actuated type seal, it is the side opposite the pressure face of the seal.

Piston Seal: A seal designed to mount onto a shaft or rod and move linearly with the shaft, sealing against the housing bore.

PTFE: Polytetrafluoroethylene- originally called and often referred to as Teflon®.

PV Rating: A unitless number derived by multiplying the speed of a rotating shaft in feet per minute by the pressure in pounds per square inch that is used primarily in bearing applications to compare different polymers wear

Rod Seal: A seal designed to mount in a housing gland and seal against a rotating or reciprocating rod.

Spring Cavity: The seat in a polymer seal jacket that captures the energizer spring.

Surface Finish: The smoothness of the surface against which the seal will ride or seat, generally called out in microinches.

Torque Requirement: The amount of torque a system needs to overcome the seal friction and rotate the shaft.