O-RING
An elastomeric seal of homogeneous composition molded in one piece to the configuration of a torus with circular cross section; more simply, a round ring with a round cross section.
OD
An abbreviation for "Outside Diameter", used to denote the outside dimension of a packing set (usually equal to the stuffing box bore).
OEM
Abbreviation for "Original Equipment Manufacturer".
OFFSET
The radial distance between the axis of the seal bore and axis of shaft rotation.
OIL SEAL
A seal designed primarily for the retention of oil.
OIL SWELL
The change in volume of a gasketing product resulting from contact with oil.
OMNI-DIRECTIONAL STRENGTH
Strength in all directions.
OPERATING PRESSURE/VACUUM
The temperature at which the system generally will operate during normal conditions.
OUTER CASE
The outer thin-wall rigid structure of the lip-seal assembly which contains the inner case, the primarily-seal ring, the spring parts, and the secondary seal.
OUTER COVER
The outside ply of material in a multiplelayer joint.
OUTSIDE LIP ANGLE
The angle between the outside lip and the axis of the seal case.
OVA
Abbreviation for "Organic Vapor Analyzer", a device used to measure the concentration of volatile organic compounds (VOCs) in the vicinity of a stuffing box, flange, or any seal. An OVA is sometimes referred to as a "sniffer".
OXIDIZER
See "Strong Oxidizer".
OZONE CRACKING
Surface cracking or cracks caused by exposure to an atmosphere containing ozone.