An O-ring is a circular ring, usually made of elastic rubber. Its size is determined by the inner diameter d1 and the wire diameter d2.
The sealing effect of an O-ring is obtained by elastic deformation of the radial wire diameter d2 in a properly designed groove. This means that the cross section of the circle is compressed into an ellipse, thereby closing the gap between the sealing or contacting surfaces and the bottom of the groove. The resulting surface compression is the key to obtaining the desired sealing effect. The℃of deformation of the O-ring wire diameter mainly depends on the groove depth
An O-ring is a sealing element with a circular cross-section. It is widely used in a variety of mechanical equipment and plays a sealing role at a certain temperature, pressure and different liquid or gas media.
① The sealing part has a simple structure, a compact installation part, and a light weight.
② It has a self-sealing effect, and often only one seal can achieve the sealing effect.
③ The sealing performance is good, and there is almost no leakage when used as a fixed seal. When used as a moving seal, there is only some leakage at a high speed.
④ The friction resistance of movement is very small, and it can also adapt to the occasions of pressure alternation.
⑤ The size and groove are standardized, the cost is low, the product is easy to obtain, and it is easy to use and purchase.
① The friction resistance at startup is large.
② When used as a seal for pneumatic devices, lubricating oil must be added to prevent wear.
③ The processing dimensions and precision requirements of coupling accessories, such as moving surfaces, grooves, gaps, etc. are very strict.
O-type rubber sealing rings are generally sealed by the rebound generated by compression, but as the pressure increases, they are squeezed into the sealing gap and change their shape, as shown in Figure 4-1.
In order to make the O-type rubber sealing ring have a good sealing effect and extend its service life, the gap between the installation groove of the O-type rubber sealing ring and the sealing part must be properly designed. When the gap is too large, the O-type rubber sealing ring squeezes the gap under the action of oil pressure, causing damage, thereby causing leakage. When the working pressure is less than 9.8MPa, a retaining ring is generally not designed. When the pressure is greater than 9.8MPa, the pressure-bearing surface of the O-type rubber sealing ring is easy to be squeezed out, and a retaining ring should be added; if it is under unidirectional pressure, a retaining ring is set on the pressure-bearing surface, and if it is under bidirectional pressure, two retaining rings are set, as shown in Figure 4-2.
Relationship between the hardness of the O-ring and the maximum gap and working pressure of the groove
The size of the sealing gap is related to the pressure level, the hardness of the rubber and the diameter of the cross section of the O-type rubber sealing ring,
The width and depth of the axial sealing groove; the width and depth of the axial sealing groove are shown in Table 4-1-8.
In the rubber material standard, the hardness and compression permanent deformation are the two properties that are most valued. Choosing a rubber material with a small compression deformation is beneficial to the sealing performance, and the hardness is crucial for the pressure resistance and anti-extrusion of the O-type rubber sealing ring. According to domestic standards and practical experience, the maximum compression permanent deformation of rubber at the specified temperature does not exceed 50%. The hardness of the rubber is closely related to the working pressure of the seal. The higher the pressure, the higher the hardness.