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Dongguan Minz Rubber & Plastics Co., Ltd.

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O-ring seal selection factors

Release time:

2019-05-27 12:30

Source:

O-ringselection factors
 
Factors to be considered in the selection of O-ring

1, working medium and working conditions in the specific selection of O-ring material, we must first consider the compatibility with the working medium. The working conditions such as pressure, temperature, continuous working time and operation cycle of the seal shall also be comprehensively considered.
If it is used in rotating occasions, the temperature rise caused by frictional heat must be considered. Different seal materials have different physical and chemical properties.
 
2, the sealing form according to the load type can be divided into static seal and dynamic seal; according to the sealing use can be divided into hole seals, shaft seals and rotary shaft seals; according to its installation form can be divided into radial installation and axial installation. For radial installation, for shaft seals, the deviation between the inner diameter of the O-ring and the diameter d2 to be sealed should be as small as possible; for hole seals, the inner diameter should be equal to or slightly less than the diameter d1 of the groove.
Axial installation, to consider the pressure direction. Under internal pressure, the outer diameter of the O-ring seal should be about 1 ~ 2% larger than the outer diameter d3 of the groove; under external pressure, the inner diameter of the O-ring seal should be about 1 ~ 3% smaller than the inner diameter d4 of the groove groove. Other factors affecting sealing performance
1. Hardness of O-ring The hardness of O-ring material is an important indicator for evaluating sealing performance. The hardness of the O-ring determines the compression of the O-ring and the large groove to allow the extrusion gap. Since the nitrile seal of Shore A70 can meet most of the use conditions, if no special instructions are made for the sealing material, the nitrile rubber of Shore A70 is generally provided.
 
2. The extrusion gap is large, and the allowable extrusion gap gmax is related to the system pressure, the cross-sectional diameter of the O-ring seal and the material hardness. Generally, the higher the working pressure, the smaller the value of the large allowable extrusion gap gmax. If the gap g exceeds the allowable range, it will cause the O-ring to be extruded or even damaged.
 
3. O-ring seal is used as a rotating shaft seal. O-ring seal can also be used as a rotating shaft seal with low speed rotating movement and short operating cycle. When the circumferential speed is lower than 0.5 m/s, the O-ring can be selected according to the normal design standard. When the circumferential speed is greater than 0.5 m/s, the phenomenon that the elongated rubber ring will shrink after being heated must be considered. Therefore, the sealing ring is selected to make its inner diameter about 2% larger than the shaft diameter sealed by it, and the above phenomenon can be avoided. After the sealing ring is installed in the groove, the sealing ring is radially compressed, and the O-shaped sealing ring forms a trace corrugation in the groove, thereby improving the lubrication condition.

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