Selection principle of O-ring inner diameter

When selecting O-ring, first of all, try to select the new national standard. Bai with wire diameter of 2.65 and 3.55 is the most common. When the outer diameter is more than 30 and the structure size allows, try to select 0-ring with wire diameter of 3.55 to achieve greater compression and contact area.

The materials of O-ring mainly include NBR and FKM, which are more suitable for high temperature. In addition to the material, the O-ring is an important indicator of its hardness, which is generally represented by shore hardness.

From about 60 to 90, the higher the number Du, the higher the hardness. Under the same pressure, the higher the hardness is, the stronger the ability to resist zh extrusion (deformation or even tearing) (right figure). Therefore, the O-ring with higher hardness should be selected.

The materials used for O-ring are nitrile rubber, carboxylic acid nitrile, fluororubber, ethylene propylene rubber, hydrogenated nitrile rubber, silicon rubber, chloroprene rubber, fluorosilicone rubber, polyurethane, chlorohydrin rubber, butadiene styrene rubber Dao rubber, butyl rubber, natural rubber, ethylene / ethylene propionate rubber, polyacrylic ester rubber, perfluoro rubber, etc.

The performance indexes of the same kind of rubber vary greatly due to different formulations. So it is not accurate to simply fill in NBR or NBR-40 in the material column. The Ministry of materials and chemical industry has special standards for O-rings.

The choice of O-ring hardness is very important. For example, the hardness of water pump turbine in a power station is 70 (Shore) seal ring, which is often peeled off or even cut horizontally. After that, 85-90 (Shore) seal ring is used, the effect is ideal.

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