Glossary of Compressed Air Terms :: O :: Glossary Index A B C D E F G H I J K L M N O P Q R S T U V W X Y Z O.D. A measurement. Outside diameter. OEM Original equipment manufacturer. Off gas Air or vapor given off or expelled as a byproduct or result of an operation or treatment process. Oil aerosol A suspension of fine solid or liquid particles in a gas. Oil bath filter A labyrinth type filter having the active surfaces continuously splashed with oil. Most pollutants are absorbed by the oil which when circulated releases its pollutants, which sink by gravity to the bottom of the oil pan. Oil free compressor A positive displacement air compressor which has no oil injected into the compression chamber for lubrication, cooling or sealing Oil system Consists of a vessel which is a combination of oil sump and oil separator, an oil cooler and an oil filter. Operating pressure The gauge pressure at which a pressure vessel is maintained in normal operation. Operating pressure burst Above this pressure, the system may rupture or burst. Orifice An opening such as a hole or vent. An opening through which air can pass, or a restricted opening placed in a pipe line to provide a means of controlling or measuring flow. OSHA Occupational Safety and Health Administration. Overhung type centrifugal compressor A single inlet compressor with the impeller or impellers mounted on an extended shaft of the driver. Overpressure accumulation The permitted increase in pressure developed after the valve has opened. Usually expressed in percentage, ie.; 3% accumulation (A.S.M.E. Code, Section I). Flows through safety/relief valves are officially determined at these overpressure conditions. Glossary Index A B C D E F G H I J K L M N O P Q R S T U V W X Y Z