Silicone O Rings Resistant to Frictional Heat in Rotating Applications

Features O-rings are widely used in various dynamic and static sealing applications due to their low manufacturing cost and ease of use.

Standards Most countries have developed a series of standards for O-rings, among which the American standard (AS568), Japanese standard (JIS B 2401), and international standard (ISO 3601/1) are more commonly used.

II. Factors to be Considered for O-ring Selection

1. Working medium and working conditions When selecting the materials for O-rings, their compatibility with the working medium shall be first taken into consideration. Besides, the pressure at the seal, temperature, continuous working tine, operating cycleand other working conditions shall also be considered. In rotating applications, the temperature rise caused by frictional heat must be considered. Different sealing materials have different physical and chemical properties. See Chemical Property Table of Rubber Materials.

2. Seal types The seal types can be divided into static seal and dynamic seal by load type;: or piston seal, shaft seal and rotary shaft seal by sealing purpose; and the mounting types can be divided into radial mounting and axial mounting. For radial mounting of shaft seal, the deviation between the inside diameter of the O-ring and the sealed diameter d2 should be as small as possible: while of piston seal, the inside diameter should be equal to or slightly smaller than the diameter dl of the groove.

III. Other Factors Affecting the Sealing Performance

1. O-ring hardness The hardness of O-ring material is one of the important indexes to evaluate the sealing performance. It determines the compression of the O-ring and the maximum allowable extrusion gap of the groove. If there is no special requirements for the sealing material, 70 Shore A nitrile rubber is generally used as it can meet most of the use conditions. The hardness requirements shall be specified if sealing material of other hardness is required.

2. Extrusion gap The maximum allowable extrusion gap max is related to the system pressure, O-ring cross-sectional diameter and material hardness. Generally, the higher the working pressure, the smaller the maximum allowable extrusion gap Emas. If the gap g exceeds the allowable range, the O-ring will be extruded or even damaged.

3. Compression set Another index to evaluate the sealing performance of O-rings is the compression set of the selected material. Under the action of pressure, the O-ring. as an elastic element, produces elastic deformation, or even permanent plastic deformation as the pressure increases.