How to choose the correct O-ring specification?

The correct selection of O-ring specifications requires consideration of the following key factors:
1, Material selection
The material of the O-ring determines its properties such as oil resistance, chemical corrosion resistance, high and low temperature resistance, and wear resistance. Therefore, when selecting O-ring materials, it is necessary to understand the specific requirements of the usage scenario, including medium type, temperature range, pressure conditions, and service life. Common O-ring materials include natural rubber (NR), chloroprene rubber (CR), ethylene propylene diene monomer (EPDM), hydrogenated nitrile rubber (HNBR), silicone, fluororubber (FKM/VITON), fluorosilicone rubber (FLS), polyurethane (PU), styrene butadiene rubber (SBR), acrylic rubber (ACM), and polytetrafluoroethylene (PTFE). Choosing the appropriate material based on actual needs is crucial.
2, Size selection
The dimensions of O-rings include inner diameter, outer diameter, and wire diameter. When selecting dimensions, it is important to pay attention to the matching of the inner diameter and wire diameter.
Inner diameter selection:
When an O-ring is used for a shaft, an O-ring with an inner diameter slightly smaller than the shaft diameter should be selected to ensure a tight fit and stable sealing effect.
When an O-ring is used for a hole, a slightly larger inner diameter O-ring can be selected to prevent deformation during operation.
Wire diameter selection:
Following the guidance of the new national standard, select wire diameter sizes that meet the standard, such as common specifications such as 2.65mm and 3.55mm.
When the outer diameter of the O-ring exceeds 30mm, if the structure allows, it is recommended to choose a wire diameter of 3.55mm to obtain greater compression and contact area.
3, Tolerance considerations
The specification tolerance of O-ring mainly includes inner diameter tolerance and wire diameter tolerance. The selection of tolerances needs to be determined based on actual dimensions and precision requirements. Generally speaking, the larger the size, the greater the tolerance. Therefore, when selecting O-rings, it is necessary to ensure that the dimensional tolerances of the selected specifications meet the actual requirements.
4, Compression selection
The compression amount of O-ring has a significant impact on its sealing effect. The correct compression amount can ensure that the O-ring can tightly fit onto the shaft or hole after assembly, forming an effective seal.
Compression coefficient: The compression coefficient of an O-ring is usually determined by its hardness. The higher the hardness, the less compression is required; The lower the hardness, the greater the compression. Therefore, when selecting O-rings, it is necessary to determine the appropriate hardness based on the actual working pressure and sealing requirements.
Compression calculation: Based on the hardness of the O-ring and the actual working pressure, the required compression can be calculated. Generally speaking, the compression amount should be controlled within a certain range to ensure that the O-ring can fit tightly without losing elasticity due to excessive compression.
5, Other precautions
Work environment: Consider the working environment of O-rings, such as temperature, humidity, vibration, etc., which may affect the sealing effect and service life of O-rings.
Installation requirements: Understand the installation requirements of O-rings, including installation methods, installation tools, and precautions during installation, to ensure that O-rings can be installed correctly and play their sealing role.
Service life: Select O-rings with appropriate service life according to actual needs and usage scenarios. At the same time, regularly check and maintain the condition of the O-ring during use, and replace aging or damaged O-rings in a timely manner.
The correct selection of O-ring specifications requires comprehensive consideration of material, size, tolerance, compression, and other relevant factors. By carefully analyzing and comparing different options, it can be ensured that the selected O-ring meets practical needs and has good sealing effect and service life.