From Essential Rubber Formulary: Formulas for Practitioners

9.1 Introduction

Oil seals and "O" rings are used in all hydraulic systems, pumps, pistons, pipe connections, etc. An oil seal used for sealing a rotating member is called a rotary seal. "O" rings are also used for a similar purpose. Oil seals are used to protect shafts and bearings from ingress of dirt and foreign matter and egress of oil or grease. An oil seal generally consists of an outer circular metal part and an inner flexible member that does the actual sealing and is bonded to the metal part by chemical adhesive agents. The sealing member is made of rubber, either synthetic or natural as the case may be. The sealing lip of the flexible member is prepared by cutting away the flash that forms at the sealing edge during molding. A fine sealing edge provides adequate pressure on the shaft to prevent leakage.

The "O" rings are light and flexible and under compression they deform to follow the component parts to be sealed. "O" rings have a long life. They provide effective sealing under constant or varying pressure, high vacuum, and high or low temperatures. Rubber "O" rings have a circular cross section. In the molding of "O" rings, the flash line at 180 is avoided and the same is preferably provided at 45 on the cross section so that the sealing face is smooth. This is achieved using a proper mold design.

Natural rubber seals and rings are suitable for air, acetylene, cold ammonia gas, alcohols,...

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Products & Services
Dynamic Seals
Dynamic seals include oil seals, hydraulic and pneumatic seals, exclusion seals, labyrinth seals, bearing isolators, and piston rings. They create a barrier between moving and stationary surfaces in applications such as rotating shafts and pistons rings.  This is a general search form; more detailed search forms are available.
Bearing Isolators
Bearing isolators are dynamic seals designed to protect bearings from outside contaminants.  They are comprised of a rotor (rotating) and stator (stationary) member.
Back-up Rings
Back-up rings or anti-extrusion rings are washer-like devices used to prevent seals from extruding through gaps while under pressure. Seals are installed in the downstream side of the gland.
Hydraulic Seals and Pneumatic Seals
Hydraulic seals and pneumatic seals include piston seals, rod seals, U-cups, vee, cup, and flange packings.

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