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O type ring

O-type sealing ring refers to the rubber ring with an "O" section. It is a widely used hydraulic and pneumatic transmission system. Mainly used for mechanical parts under static conditions to prevent the leakage of liquid and gas medium. In some cases, the O-ring can also be used as a dynamic sealing element for axial reciprocating motion and low speed rotation motion. It has the advantages of simple structure, convenient installation, low cost, easy maintenance and diverse materials. Can be used as oil, water, gas and other kinds of fluid seal. According to different conditions, different materials can be selected respectively to adapt to it.

From the point of view of the sealing principle, O sealing ring is a kind of extrusion seal, the basic working principle of extrusion seal is to rely on the elastic deformation of the seal, the contact pressure on the sealing contact surface, the contact pressure is greater than the internal pressure of the sealed medium, there is no leakage, and on the contrary, there is leakage.

Method of marking

O-ring specification representation method: Inner diameter * Wire diameter (ID*C/S)

Optional criteria: GB3452.1 series, AS568 series, JIS B 2401 series

★Note: Non-standard specifications can be customized


Why choose Yifang

Trust authentic Yifang

1. The realization of our strong partnership with our customers depends on the following basic aspects: material suitability, innovation strength, strict quality management and rich experience in functional integration. Our company has a number of sets of molds and a huge database of raw materials, with enough experience to deal with the sealing problems in various media and various working conditions.

2. When purchasing, sealing parts are sometimes purchased as class C materials according to their importance and function. In fact, sealing parts should belong to Class A materials. Hydraulic pneumatic valve seal is the core component of this technology.

3, Since the company put into operation, the reliability of the technology, the efficiency of the system, the environmental solution and the solid partnership with the customer have driven the company to continue to develop, through the additional features provided by various seals to demonstrate its expertise in functional integration, Yifang has fully demonstrated that it has enough experience to deal with the interaction between seals and various media, lubricants.

Our raw material advantage

Close cooperation with DuPont, JSR, Dow Corning, and a large raw material formula database, so that our raw material properties are relatively stable, product quality control, independent rubber formula design capability enables us to meet the actual needs of customers to a greater extent.

Our product inspection and quality control

Inspection of incoming materials

All raw materials shall be tested before storage, and the corresponding physical property report of raw materials shall be issued and compared with the physical property report of raw materials. The two physical property reports shall be stored only if the test values are consistent.

Inspection of mold

After mold development or mold cleaning, we will check the full size of the mold to ensure that the product quality of each cavity is consistent.

In-process inspection of products

In the process of product production, inspection personnel regularly inspect semi-finished products to ensure the rationality of the process and control the defective rate within a reasonable range.

Quality control

The quality department will make a spot check on the appearance of each batch of products.

Complete inspection of finished products

The optical inspection machine can ensure that the appearance and size of the product are 100% qualified.

Complete inspection of finished products

The optical inspection machine can ensure that the appearance and size of the product are 100% qualified.

Technical Requirements

Working condition

Working pressure: 0~70Mpa(A retaining ring is required for high pressure)

Speed: The maximum reciprocating speed can reach 0.5m/s and the maximum rotating speed can reach 2.0m/s

Temperature of service: -60℃~320℃ 

Medium of operation: All kinds of lubricants, liquids and gases

The relationship between material hardness and working pressure

The hardness of O ring is directly related to its pressure resistance. In general, the higher the hardness of the O-ring, the better its resistance to high pressure.

Hardness (Shaw A)/degree 50±5 60±5 70±5 80±5 90±5
Working pressure static seal/Mpa ≤ 0.5 110 2050
Working pressure (reciprocating movement,
speed ≤0.2m/s) /Mpa ≤
0.5 1 8 16 24

Different temperature ranges of synthetic rubber

Various synthetic rubber materials can meet the operating temperature of O-ring under different conditions. According to the working condition of the product, the O-ring rubber material suitable for its temperature can be selected.


Design of structure

Standard table of dimensional tolerance: Unit (mm)

Standard tolerance table of inner diameter
Inner diameter (ID) The tolerance(±)
≤2 0.1
2.01-10 0.13
10.01-20 0.19
20.01-30 0.26
30.01-40 0.34
40.01-50 0.41
50.01-60 0.48
60.01-70 0.55
70.01-80 0.61
80.01-90 0.69
90.01-100 0.76
100.01-125 0.82
125.01-140 0.99
140.01-155 1.09
155.01-175 1.19
Standard tolerance table of inner diameter2
Inner diameter(ID) The tolerance(±)
175.01-200 1.33
200.01-250 1.49
250.01-280 1.82
280.01-330 2.01
330.01-360 2.33
360.01-400 2.52
400.01-440 2.78
440.01-470 3.05
470.01-500 3.32
500.01-530 3.41
530.01-560 3.6
560.01-600 3.78
600.01-630 4.03
630.01-650 4.22
650.01-670 4.34
Standard table of line diameter tolerance
Wire diameter(CS) The tolerance(±)
- 2.00 0.08
2.01 – 3.00 0.09
3.01 – 4.00 0.10
4.01 – 5.00 0.12
5.01 – 7.00 0.15
7.01 – 10.00 0.20
10.01 – 15.00 0.25
15.01 – 25.00 0.35

The design of the trench

The O-ring in the groove will deform under the drive of medium pressure, and the edge part of the O-ring will flow into the clearance position to achieve the O-ring sealing function. The greater the pressure on the O-ring, the greater the deformation of the O-ring, the better the sealing effect of the O-ring will be. When the pressure on the O-ring exceeds its bearing limit, the O-ring will be squeezed into the gap, resulting in the failure of the O-ring seal. The design of O-ring groove must be reasonable.

Clearance of extrusion

The maximum allowable extrusion clearance gmax is related to the system pressure, O-ring section diameter and material hardness. Generally, the higher the working pressure is, the smaller the maximum allowable extrusion clearance gmax is. If the clearance g exceeds the allowable range, the O-ring will be extruded or even damaged.

Compression permanent deformation

Another index to evaluate the sealing performance of O-ring is the compression permanent deformation of the selected material. Under the action of pressure, as an elastic element of the O-ring, elastic deformation, as the pressure increases, there will be permanent plastic deformation. The compression permanent deformation d can be determined by the right equation:


Where: b0- original thickness (i.e. section diameter W) b1- thickness under compression b2- thickness after release


In general, to prevent permanent plastic deformation, the maximum compression allowed for O-rings is about 30% in static seals and 20% in dynamic seals.


Compression rate and filling rate setting

E (%):Ratio of compression

T(mm):Compression margin (T=W-H)

W (mm):O-ring cut diameter

H(mm):Depth of groove

n (%) :Rate of filling

G (mm):Width of groove


Compression ratio setting

Scope of use:8%-30%(dynamic seal: 8%-20%; Static seal: 15%-30%)


Setting of filling rate

Scope of use:max90%, design target value 75%


Recommended dimensions for O-ring grooves

Standard table of dimensional tolerance: Unit (mm)

Diameter of section w Radial dynamic and static Axle seal only The radius of
Width of groove
g0+0.2 Retaining ring
Retaining ring
circler r
1.20 0.801.40 -- 0.65 1.40 0.20 -
1.25 1.001.80 -- 0.851.80 0.20 -
1.52 1.20 1.90 2.90 3.90 1.00 2.10 0.20 0.20
1.78 1.45 2.20 3.60 5.00 1.20 2.40 0.40 0.20
1.80 1.452.20 2.605.00 1.202.40 0.40 0.20
1.90 1.652.50 3.905.30 1.402.500.50 0.30
2.40 2.002.90 4.305.70 1.70 3.20 0.50 0.30
2.62 2.253.10 4.505.90 1.903.60 0.60 0.30
3.50 3.104.20 5.607.00 2.704.80 1.00 0.40
3.53 3.104.20 5.607.00 2.704.80 1.00 0.40
5.33 4.706.20 7.909.60 4.307.10 1.20 0.40
5.70 5.006.70 8.4010.10 4.60 7.701.20 0.60
7.00 6.10 8.20 10.70 13.20 5.80 9.50 1.50 0.60
8.40 7.509.70 12.2014.70 6.9011.70 2.00 0.60
If a large expansion is required, the trench width can be increased by 20%

★ Extrude

The seal has a ragged edge, usually on the low pressure side.
Cause of
The gap is too large; Too much pressure; Material hardness or elasticity is too low; The groove space is too small; The clearance size is irregular; The grooves are too sharp; The seal is not the right size.
The Solution
Reduce the gap size, choose higher hardness or elasticity of materials, reasonable groove design.

★ Crimping seal

The seals show obvious crimp.
Cause of
Due to installation, the movement speed is too low, the material is too hard or too elastic, the surface treatment of the seals is not uniform, the groove size is not uniform, the groove surface is rough, and the lubrication is insufficient.
The Solution
Correct installation, choose high elastic type materials, choose self-lubricating materials, appropriate groove design and surface finish, try to use support rings.

★ Permanent compression deformation

The contact surface of the seal presents planar permanent deformation.
Cause of
Too much pressure; High temperature; The material has not been cured; The permanent deformation rate of the material is too high; The material expands excessively in a chemical medium.
The Solution
Select materials with low deformation rate; Suitable groove design; Verify that the material is compatible with the medium

★ Installation damage

Part or all of the seal presents a neat wound.
Cause of
Grooves and other parts edge and corner sharp, seal size is not suitable. The hardness or elasticity of the seal is too low; There is dirt on the surface of the seal.
The Solution
Clear sharp edges and corners; Groove design is more reasonable; Select the right size seal; Choose a seal with greater elasticity and hardness.

★ Excessive compression

The contact surface of the seal is deformed in plane and may be accompanied by cracks.
Cause of
Unreasonable design; The deformation of the material due to heat and chemical medium, or due to excessive pressure is not taken into account.
The Solution
The design of grooves should take into account the deformation of materials due to temperature and chemical media.

Hot corrosion

The high temperature contact surface of the seals shows radial cracks, and some materials may become soft or shiny due to high temperature.
Cause of
The material cannot withstand high temperatures, or temperatures that exceed the expected temperature, or temperatures that change too quickly and too frequently.
The Solution
Choose materials with high temperature resistance, and reduce the sealing surface temperature as much as possible.

★Electrical corrosion

The seal is faded, and a powdery substance remains on the surface. There are corrosion marks on the side without contact with the medium.
Cause of
Chemical reactions produce electrolysis, splash erosion (ions impact on the surface of the structure to cause material loss), scorching, groove design is not reasonable, sealing materials and media are incompatible.
The Solution
Select the appropriate material for the medium, lower the exposed area, and check the groove design.

★ Wear and tear

Wear occurs in all or part of the sealing area of the seal, and particles of worn material can be found on the sealing surface.
Cause of
The sealing surface is not smooth enough, the temperature is too high, the dirt with strong wear is infiltrated, the sealing parts have relative movement, and the sealing parts are not thoroughly treated on the surface.
The Solution
Use the recommended groove finish, use self-lubricating materials, and remove parts and environments that cause wear and tear.

★ Pressure blasting

The surface of the seal presents bubbles, pits, scars; When the pressure is high, the material absorbs the gas in the medium. When the pressure is suddenly reduced, the gas absorbed by the material quickly escapes. Cause the sealing skin to burst.
Cause of
The pressure changes too fast and the hardness and elasticity of the material are too low.
The Solution
Choose materials with high hardness and high elasticity to reduce the speed of decompression.

★ Chemical corrosion

Chemical corrosion can cause various defects of seals, such as foaming, cracking, small holes or fading, and sometimes chemical corrosion can only be measured by instruments.
Cause of
The material does not conform to the medium or the temperature is too high.
The Solution
Choose materials that are more resistant to chemical media.

★ Loss of gas precipitated material

This defect is often difficult to detect, and seals often appear as reduced section size.
Cause of
Improper curing of materials, high vacuum sealing requirements, low hardness of materials, or the use of materials with plasticizers.
The Solution
Avoid using materials with plasticizers and ensure that the seals are properly vulcanized to minimize leakage.

★ Pollution.

There is a foreign body in the section of the seal.
Cause of
The production process is polluted by the environment, and the materials are corroded or reacted. The materials are non-semiconductor industry grade materials.
The Solution
Indicate the cleanliness of production and packaging requirements, strengthen the environmental control of the production, transportation and use of seals.

Yifang quality service

We cherish your every online inquiry, have to ask the answer, with a professional attitude, intimate service.


Professional response to customer problems, put forward the sealing scheme. We have professional technical personnel to provide customers with selection, design and other aspects of technical support. And can try our company's product samples for selection. Yifang aims to provide effective sealing for customers worldwide


Respect customers, take the initiative to serve. Keep your word, to meet the needs of customers for the purpose. Strict control of product quality and delivery time. Prevent defective products from being sent to customers.


Follow up and visit customers, actively respond to customers' questions, and patiently answer customers' questions when using products. If the product quality problems can be implemented return system.

Our customers

At present, the main customers are: Dongfeng Second Automobile, Baoshide, Covus Robot, Hitachi, Dong-A Corporation, Kojima Corporation, Jiangsu Dongcheng Tools and other companies supporting the production of rubber products.




Address: Yangsha East Road, Chengbei Industrial Park, Huilong Town, Qidong City

Tel: +86-513-83691098 83698000

Fax: +86-513-83698018 83691798

E-mail: yfxs@ntrubber.com

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