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How To Size O Ring Seals
Sep 13, 2018

O-ring is a kind of rubber seal with a circular cross section. Because its cross section is O-shaped, it is called O-ring seal, also called O-ring. It began to appear in the mid-19th century when it was used as a sealing element for steam engine cylinders.


Because of its low cost, simple manufacturing, reliable functionality, and simple installation requirements, O-rings are the most common mechanical design for sealing. O-rings are subjected to pressures of tens of megapascals (thousand pounds). O-rings can be used in static applications or in dynamic applications where there is relative motion between components, such as the shaft of a rotary pump and the piston of a hydraulic cylinder.


Determine the size of the O-ring. If it is a static seal, it can generally be confirmed as follows: the bottom diameter of the groove / 1.04 (the elongation is calculated as 4%) = the inner diameter of the O-ring; the groove depth * 1.2 (the compression ratio is calculated as 20%) =O-ring wire diameter; considering the compression of the O-ring cross section will be spread out, the groove width is generally about 1.3 times the wire diameter. Of course, it is necessary to consider the working conditions of the seal.


The size of the o-ring groove is the outer diameter of the ring, which is 5/5.5/6/7/8/9, etc. When selecting, try to use the O-ring with large section. In the case of the same clearance, O-type The volume of the seal that is forced into the gap should be less than the maximum allowable value