How to choose o-ring for your mechanical seal?

O-rings are widely used in a variety of dynamic and static sealing applications because of their low manufacturing cost and ease of use.

Most countries have established series of product standards for O-ring seals, among which American Standard (AS 568), Japanese Standard (JIS B 2401), and International Standard (ISO 3601/1) are more general.

Sealing mechanism:

The O-ring is an automatic two-way sealing element. The radial and axial pre-compression of the mounting imparts an initial sealing capability to the O-ring itself. It increases as the system pressure increases.

 

Performance parameter:  

static seal Dynamic seal
Working Pressure Without a retaining ring, up to 20MPa;

With a retaining ring, up to 40MPa;

Up to 200MPa when using special retaining rings。

Without a retaining ring, up to5MPa;

Higher pressure when there is a retaining ring

working speed The maximum reciprocating speed is up to 0.5m/s and the maximum rotating speed is up to 2.0m/s
Temperature General occasion:-30℃~+110℃;Special rubber:-60℃~+250℃;Rotating occasion:-30℃~+80℃

 

1 Working medium and working conditions

When selecting O-ring materials, the compatibility with the working medium should be considered first. It is also necessary to consider the working conditions such as pressure, temperature, continuous working time and operating cycle of the seal. If used in a rotating environment, the temperature rise due to frictional heat must be considered. Different seal materials have different physical and chemical properties.

2 Sealed form

According to the type of load, it can be divided into static seal and dynamic seal; according to the sealing use, it can be divided into hole seal, shaft seal and rotary shaft seal; according to its installation form, it can be divided into radial installation and axial installation. For radial mounting, the deviation between the inner diameter of the O-ring and the diameter d2 to be sealed should be as small as possible for the seal of the shaft; for the seal of the hole, the inner diameter should be equal to or slightly smaller than the diameter d1 of the groove.

Mechanical seals o ring.jpg

When installing axially, consider the direction of pressure. For internal pressure, the outer diameter of the O-ring should be about 1-2% larger than the outer diameter d3 of the groove; for external pressure, the inner diameter of the O-ring should be about 1 to 3% smaller than the inner diameter d4 of the groove.

1.Cheap, can be used in low cost media
2.Simple, monolithic groove design reduces part and design costs
3.Compact design with small part shape
4.Installation is extremely simple, reducing errors
5.Suitable for solving many sealing problems, such as static seals, dynamic seals, single-acting or 6.double-acting seals. Many compounds are available and compatible with most fluids.

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