What is an O-Ring?

What are O-Rings in connectors? Why are they used?

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- everything RF

Jul 7, 2022

O-rings are loops of elastomer that have a circular cross-section and are designed to be seated in a groove (narrow depressions) between two or more parts forming a seal at the interface. In RF connectors, O-rings are used to seal the connection point against temperature changes, fluid (liquids/gas) leaks including chemicals & pressure variations and to secure the connector in place.

O-rings are made of elastic polymers with properties that make them a crucial component of many precision-engineered devices. They are naturally springy and their tendency to return to their original shape when the cross-section has pressure exerted on it makes them one of the most economical and reliable methods of making a strong seal in an RF connection. The O-ring is placed into a groove to secure them in place and then compressed between two surfaces. The squeezed O-ring does not have any more clearance to move and it blocks the pathway of the liquid or gas that may try to pass through small openings.

RF connectors are used in many types of industries and dangerous environments, they are susceptible to several types of liquids, gases, pressure and temperature changes etc. They are used by different machinery in almost all industries and hence prone to liquids and gases that may seep through to the connection point and disrupt RF signals that pass through it or cause short circuits that may damage equipment. They are also prone to various types of chemicals that may corrode the connectors. RF connectors are also used in underwater machinery, airborne vehicles (like planes, helicopters etc.) parts and even in space (satellites, space stations etc.). In such scenarios, they may undergo major changes in pressure and temperature which may cause the connector to loosen or even disconnect.

O-rings in RF connectors are usually found in the Male (M) components around the opening of the segment that is inserted in the Female component (See above image). These O-rings help seal and secure the connection point so that the connector does not loosen up due to vibrations or movement of parts. The connection is sealed from liquid or gas leakage completely by the tightly secured O-ring. The elastomers that are used to make O-rings are also unreactive with most chemicals and hence protect the connection point from corrosion. When RF connectors with O-rings are connected, the connection point is sealed inside an exceptionally resistant chamber. The sealed chambers due to O-rings have been tested to withstand up to 5,000 psi (34 MPa) of pressure and cope with temperatures as low as -100°C or as high as 316°C depending upon the seal hardness and gland clearance.

O-rings are available for almost all kinds of RF connectors and in different sizes, materials and thicknesses that selected based on the desired application. They are one of the simplest, yet highly critical, precision mechanical components ever developed.