Glossary O


  • Outside diameter.


  • Original equipment manufacturer. The pump or seal company, not the distributor of the products.

Oil analysis

  • A sensible preventative maintenance technique to check the oil for solids, water etc.

Oil life

  • Lubricating oil has a useful life of about thirty years at thirty degrees centigrade if it is not contaminated.

Oil mist

  • A lubrication system where oil and air are mixed and sent into the pump bearing case. Not friendly to the environment.

Operating length

  • Measured after the seal has been compressed the proper amount. The measurement is usually made from the face of the stuffing box.

Optical flat

  • A high quality glass lapped flat on one side and used with a monochromatic light to read seal face flatness.

O-ring groove

  • The space into which an O-ring is inserted. Dynamic O-ring grooves use a different dimension than static O-ring grooves.


  • Occupational and Safety Health Act. Government regulations that affec the sealing business. OSHA 1910 is one of the more important that impacts the training of seal mechanics and operators.

Over hung impeller

  • Not supported with bearings on either side of the impeller.


  • Combines with carbon to form carbon monoxide or carbon dioxide. The oxidizers attack all forms of carbon including the seal face and any black O-rings in the system.


  • Created by oxygen atoms combining with oxygen molecules in a high energy atmosphere .Will prematurely age Buna rubber. Ozone forms in the shop as a result of the sparking of electric motor brushes.