Introduction on O-rings

O-rings are rubber seals with a circular cross-section. Because of their O-sections, they are called O-rings, also called O-rings. It began to appear in the mid-19th century when it was used as a sealing element for steam engine cylinders.

Because of its cheap price, simple manufacturing, reliable function, and simple installation requirements, the O-ring is the most common mechanical design for sealing. The O-ring is subjected to tens of megapascals (thousand pounds) of pressure. O-rings can be used in static applications, but also in dynamic applications where there is relative movement between components, such as the Top quality PTFE Filled With Bronze GuideTapes manufacturer from China shaft of a rotary pump and the piston of a hydraulic cylinder.

Scope of O-ring

O-ring seals are suitable for installation on various mechanical equipment, and play a sealing role in static or moving state under the specified temperature, pressure, and different liquid and gas media. In machine tools, ships, automobiles, aerospace equipment, metallurgical machinery, chemical machinery, engineering machinery, construction machinery, mining machinery, petroleum machinery, plastic machinery, agricultural machinery, and various types of instruments, various types of seals are widely used element. O-rings are mainly used for static sealing and reciprocating sealing. When used for rotary motion sealing, it is limited to low-speed rotary sealing devices. O-rings are generally installed in grooves with a rectangular cross-section on the outer or inner circle for sealing. O-ring seals still play a good role in sealing and shock absorption in the environment of oil resistance, acid and alkali, grinding, chemical corrosion and other environments. Therefore, the O-ring is the most widely used seal in hydraulic and pneumatic transmission systems.

Material classification

Natural rubber N R

(Natural Rubber) Made from latex collected from rubber trees, it is a polymer of isoprene. Has good wear resistance, high elasticity, tear strength and elongation. It is easy to aging in the air, it becomes sticky in heat, it swells and dissolves in mineral oil or gasoline, and it is resistant to alkali but not strong acid. · It is the raw material for making adhesive tape, hose, rubber shoes, and is suitable for making shock-absorbing parts, and products used in hydroxide-containing liquids such as automobile brake fluid and ethanol.

Styrene butadiene rubber S B R

Styrene Butadiene Copolyme is a copolymer of butadiene and styrene. Compared with natural rubber, Styrene Butadiene Copolyme has uniform quality and less foreign matter, but its mechanical strength is weaker. It can be blended with natural rubber.

Butyl rubber IIR

Butyl Rubber is made from the polymerization of isobutylene with a small amount of isoprenes. It retains a small amount of unsaturated groups for vulcanization. Because the movement of steric barrier molecules of methyl group is less than other polymers, the gas permeability is less. It has high resistance to heat, sunlight and ozone, and good electrical insulation; it has high resistance to polar solvents such as alcohols, ketones, and esters, and the general use temperature range is -54~110 ℃.

O-shaped rubber sealing ring is a sealing element with a circular cross-sectional shape. It is widely used in a variety of mechanical equipment and plays a sealing role in a certain temperature, pressure and different liquid or gas medium. Compared, it has the following superior performance:

--Suitable for multiple sealing forms: static sealing, dynamic sealing

Suitable for all kinds of materials, the size and groove have been standardized, and the interchangeability is strong

--Suitable for a variety of movement methods: rotary movement, axial reciprocating movement or combined movement (such as rotary reciprocating combined movement)

--Suitable for many different sealing media: oil, water, gas, chemical media or other mixed media

Through the selection of appropriate rubber materials and appropriate formula design, it can effectively seal oil, water, air, gas and various chemical media. The temperature can be used in a wide range (- 60 ℃~+ 220 ℃), and the pressure can reach 1500Kg/cm2 in fixed use (combined with the reinforcement ring).

--Simple design, compact structure, convenient assembly and disassembly

The O-ring cross-sectional structure is extremely simple, and has a self-sealing effect, and the sealing performance is reliable.

Because the O-ring itself and the structure of the installation site are extremely simple and standardized, it is very easy to install and replace.

--Various materials

Can be selected according to different fluids: nitrile rubber (NBR), fluorine rubber (FKM), silicone rubber (VMQ), ethylene propylene rubber (EPDM), neoprene rubber (CR), butyl rubber (BU), polymer Tetrafluoroethylene (PTFE), natural rubber (NR), etc.

--low cost

- Dynamic friction resistance is relatively small

Pressure and sealing gap

O-shaped rubber seals are generally sealed by the rebound produced by compression, but as the pressure increases, it is squeezed into the seal turbidity and changes in shape

In order to make the O-shaped rubber sealing ring have a good sealing effect and extend the service life, the gap between the installation groove of the O-shaped rubber sealing ring and the sealing part must be designed properly. When the gap is too large, the O-shaped rubber sealing ring is The gap is squeezed under the action, causing damage and causing leakage.

Relationship between the hardness of O-ring rubber material and working pressure

In the rubber material standard, the two properties of hardness and compression set are the most important. Choosing a rubber material with less compression deformation is beneficial to the sealing performance, and the hardness is also crucial to the pressure resistance and squeeze resistance of the O-shaped rubber sealing ring. According to domestic standards and practical experience, the maximum compression set of rubber at a specified temperature does not exceed 50%. The hardness of the rubber is closely related to the working pressure of the seal. The higher the pressure, the higher the hardness.

Groove finish requirements and groove and compression

The smoothness of the groove and the roughness of the groove contact surface have a great influence on the sealing effect and durability.

The compression rate of the O-shaped rubber sealing ring for fixed sealing is generally 15-25% (this data is empirical data), and the compression rate is 10-12% in the case of reciprocating motion, and generally 3-5 in rotary motion % Compression rate.