O – ring design knowledge set

Feb 06
2017

First, O-shaped rubber seal is a circular cross-section of the sealing element, it is widely used in a variety of mechanical equipment, at a certain temperature, pressure and different liquid or gas medium to play the role of sealing, and other seals Ring, has the following advantages:
①, sealing parts of a simple structure, the installation site is compact, and lighter weight.
②, a self-sealing effect, often only a seal will be able to complete the sealing Groove and compression
The compression ratio of O-shaped rubber seal for fixed seal is generally 15-25% (this data is the empirical data), 10 ~ 12% for reciprocating motion and 3 ~ 5 for rotary motion. % Of the compression rate, commonly used O-shaped rubber ring compression and groove size shown in Table 4-1-9 cnc drill effect.
③, good sealing performance, used as a fixed seal almost no leakage when used as a sports seal, only at higher speeds when some leakage.
④, the movement friction resistance is very small, also can adapt to the pressure change situation.
⑤, size and groove has been standardized, low cost, easy to use, easy to use and outsourcing.
Compared with other seals, there are the following three problems:
①, the starting friction resistance.
②, used as a pneumatic device seal, you must add lubricants to prevent wear.
③, the coupling parts, such as sports surfaces angle bending machine, grooves, gaps and other processing size and precision requirements are very strict.
Structural Design Principle of O – ring Rubber Seal
Because O-ring seals are used in a variety of trenches, the mounting trenches are listed in Table 4-1-3.

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Pressure and seal clearance
O-ring rubber seals are generally produced by the rebound of the compression to be sealed, but with the pressure increases, it is squeezed into the seal turbidity gap to produce a shape change, as shown in Figure 4-1

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In order to O-shaped rubber seal with a good seal and extend the service life, O-ring rubber seal must be installed groove and seal the gap between the design of appropriate, when the gap is too large O-ring rubber seal in the oil pressure Under the role of squeeze gap, causing damage, causing leakage. When the working pressure is less than 9.8Mpa generally do not design the retaining ring, when the pressure is greater than 9.8Mpa iron punching machine when the O-shaped rubber ring bearing pressure surface is easy to be squeezed out, should be added ring; if one-way compression in the bearing surface set a block Circle, if the two-way compression will have to set two retaining ring, as shown in Figure 4-2

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O-ring performance standards

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The relationship between the hardness of O – ring and the maximum clearance and working pressure of groove
Sealing gap size and pressure levels, rubber hardness and O-shaped rubber seal section of the diameter of the relevant circumstances, see the following table:

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Groove depth in piston rod seal

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Depth of the groove when sealing the cylinder bore

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Radially seals the depth of the groove
General radial seal groove width; see Table 4-1-5

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Axial Groove Width and Depth of O – Ring Seals with Different Cross – Section
Axial seal groove width and depth; see Table 4-1-8 for axial seal groove width and depth

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The relationship between the hardness of O – ring rubber material and working pressure
In the rubber material standard, the hardness and compression set the most important performance of the two. Select the smaller compression deformation of the rubber material on the sealing performance is beneficial, and the hardness of the O-shaped rubber seal pressure and anti-squeeze is sheet metal punch essential. According to domestic standards and practical experience, the rubber at the specified temperature of the maximum compression deformation of not more than 50%. The hardness of the rubber and seal work pressure is closely related to the higher the pressure, the hardness is higher; see Table 4-1-11

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Note: Rotary movement working pressure is generally not more than 0.4 Mpa, hardness selected in (70 ± 5) degrees; beyond 0.4 Mpa according to a special seal device design.
Groove finish requirements
The smoothness of the trench, the roughness of the trench contact surface, has a significant effect on the sealing effect and durability.
The surface roughness of each mating coupling groove of the seal groove

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Groove and compression
The compression ratio of O-shaped rubber seal for fixed seal is generally 15-25% (this data is the empirical data), 10 ~ 12% for reciprocating motion and 3 ~ 5 for rotary motion. % Of the compression rate, commonly used O-shaped rubber ring compression and groove size shown in Table 4-1-9

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