Wuxi Ruike Machinery Parts Co., Ltd. brings you information on rubber seals: the role and correct application of O-rings.
What are O-ring rubber seals?
An O-ring is a moderately compressed, O-shaped (circular) seal installed in a rubber seal groove. It can be used as a seal for various fluids such as oil, water, air, and gases. There are two types of uses: static and dynamic.
Correct usage of O-rings
2.1 Selection of cross-sectional diameter
With a certain compression ratio, a larger cross-sectional diameter results in less deformation. Using an O-ring with a larger cross-sectional diameter can provide a stable seal. Especially when used as a dynamic seal, a larger cross-sectional diameter can prevent twisting.
2.2 Use under high pressure
O-rings function due to the compressive stress of the material. Additionally, they provide a sealing effect due to the pressure of the sealing fluid. Therefore, the endpoint of pressure should be considered theoretically. In practical applications, the O-ring inevitably experiences the pressure of the sealing medium fluid, maintaining its function without being squeezed in.
Thus, the actual pressure resistance of the O-ring is determined by the relationship between the mechanical strength of the material (represented by hardness) and the clearance. When the retainer ring receives pressure from both directions, it can be installed on both sides of the O-ring simultaneously. When receiving pressure from one direction, a retainer ring is installed on the opposite side of the pressure. There are three types of retainer rings: ring type, bevel type, and spiral type. From a functional perspective, the ring type is preferred. In terms of ease of installation, the bevel and spiral types are more convenient.
2.3 Different uses of O-ring rubber seals
① Cylindrical static seal
Even when using O-rings and groove dimensions according to JIS specifications, there may be sagging into the inner diameter of the groove due to the combination of dimensional tolerances. Please avoid O-ring biting during installation.
② Planar static seal
Planar static seals can be divided into two types: those that accept internal pressure and those that accept external pressure. For internal pressure applications, the outer diameter D of the O-ring is used in principle, while for external pressure applications, the inner diameter d of the O-ring is used.
Since the extrusion rate is usually not a problem during installation, consider the elongation of the bolt and the deformation of the flange surface after receiving pressure, which may be greater than that of the cylindrical static seal. In such cases, due to the lack of adherence to the wall, sometimes wear or fallout may occur due to pressure changes. Please avoid using it.
When the inner diameter is relatively large (Φ 150 or more) and the cross-sectional diameter is relatively thin (Φ 3 or less), there may be situations where the O-ring flies out, clamps, or a portion of the O-ring is trimmed, as shown in Figure -5. To prevent the O-ring from flying out in such cases, a thicker cross-sectional diameter can be used.
In applications that accept internal pressure, when the D dimension is relatively small (approximately Φ 30 or less), there may be situations where the installation is not suitable. A slightly larger D dimension (approximately 0.2 to 0.3mm) may be more convenient.
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