WHAT IS AN O-RING? An O-ring is a torus, or a doughnut shaped object, generally made from an elastomer, although such materials as plastics and metal are sometimes used. This area will deal entirely with elastomeric O-rings used for sealing purposes ANATOMY OF AN O-RING
BASIC PRINCIPLES OF THE O-RING SEAL
Prevention of the fluid loss or transfer may be obtained by several methods: welding, soldering, brazing or the yielding of a softer material wholly or partially confined between two mating surfaces. This latter method best describes the design principle behind the operation of an O-ring seal. THE FUNCTION OF THE O-RING The elastomer is contained in the gland and forced to flow into the surface imperfections of the glands and any clearance available to it, creating a condition of "zero" clearance and thus effecting a positiveblock to the fluid being sealed. The pressure which forces the O-ring to flow is supplied by mechanical pressure or "squeeze." generated by proper gland design and material selection and by system pressure transmitted by the fluid itself to the seal element. In fact, the classic O-ring seal may be said to be "pressure assisted" in that the more system pressure, the more effective the seal, until the physical limits of the elastomer are exceeded and the O-ring begins to extrude into the clearance gap This condition can usually be avoided by proper gland design, material selection, and the use of Parbak backup rings. STATIC AND DYNAMIC O-RING SEALING APPLICATIONS O-ring seals are generally divided into two main groups. Static seals, in which there is little or no relative motion between the mating surfaces; and dynamic seals, which must function between surfaces with definite relative motion, such as the seal on the piston of a hydraulic cylinder. Of the two types, dynamic sealing is the more difficult and requires more critical design work and materials selection. The most common type of dynamic motion utilizing an O-ring sealing system, is reciprocal motion as found in hydraulic cylinders, actuators and the like.
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For
those unfamiliar with sealing technology, we have provided this brief section to assist
you in understanding the O-ring, its basic design principles, and the many sealing
functions an O-ring may be expected to perform when properly specified and installed.
An O-ring seal is a means of closing off a passageway
and preventing an unwanted loss or transfer of fluid. The classic O-ring seal consists of
two elements, the O-ring itself, and a properly designed gland or cavity to contain the
elastomeric material. The illustration below shows a typical O-ring seal. 