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O-ring selection factors

Update:30 Oct 2017
Summary:

1  working medium and working conditions 2  first consi […]

1  working medium and working conditions
2  first consider the compatibility of the product and the working medium, and then consider the seal at the pressure, temperature, continuous working hours, operating cycle and other conditions, the use of rotating occasions also consider the friction caused by the temperature rise
sealed form
For shaft seals, radial mounting shall be such that the deviation between the inner diameter of the O-ring and the diameter of the seal should be as small as possible; the seal for the hole shall be such that its inner diameter is equal to or slightly less than the diameter of the groove. Axial installation, the need to consider the direction of pressure, the internal pressure, O-ring outer diameter should be about 1% -2% outside the groove, the external pressure, the O-ring diameter should be about 1% -3%
4  Other factors that affect the sealing performance
1) Hardness: Determines the amount of compression of the O-ring and the maximum allowable extrusion gap of the groove
2) Extrusion gap: with the system pressure, O-ring diameter and the hardness of the material, the correlation see table
3) Compression permanent deformation: In case of pressure, in order to prevent permanent plastic deformation, O-ring allows the maximum amount of compression in the static seal is about 30% in the dynamic seal is about 20%
4) Precompression: To ensure the sealing of the O-ring in the groove, an initial amount of compression should be reserved, which is typically about 15% to about 30% of the static seal relative to the pre-compression of the cross- In the dynamic seal of about 9% -25%
5) Stretch in compression: For the hole seal, the O-ring is in the stretched state, the maximum allowable amount is 6%. For the shaft seal, the O-ring is compressed along its circumference and the maximum allowable circumference The amount of 3%.

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