The requirements for sealing rings in dynamic sealing mainly lie in material properties, structural adaptability, dynamic stability, environmental resistance, as well as installation and maintenance. The following is a detailed introduction:
Material performance requirements
Elasticity and resilience
The sealing ring needs to have high elasticity and resilience to ensure a tight fit with the sealing surface under dynamic working conditions, compensate for the gap caused by vibration, eccentricity or wear, and maintain an effective seal. For instance, in the sealing of rotating shafts, elastic materials can absorb the vibration of the shaft and prevent leakage.
Mechanical strength
The sealing ring needs to withstand dynamic pressure, friction and medium impact, so it must have sufficient tensile strength, tear strength and wear resistance. For instance, in reciprocating motion sealing, the sealing ring needs to resist the repeated compression of high-pressure media to prevent damage.
Medium resistance
The material of the sealing ring should be compatible with the sealing medium (such as oil, water, chemical solvents, etc.) to prevent swelling, dissolution or performance deterioration. For instance, fluororubber (FKM) is suitable for high-temperature fuel environments, while silicone rubber (VMQ) is appropriate for low-friction and aging-resistant applications.
Temperature resistance
The sealing ring needs to maintain stable performance in high-temperature (for example, the engine lubricating oil temperature can reach 150℃) or low-temperature (for example, the liquid nitrogen system can reach -196℃) environments, and avoid hardening, embrittlement or softening.
Structural adaptability requirements
Sealing lip design
The shape (such as V-shaped, U-shaped, Y-shaped) and Angle of the sealing lip need to be optimized according to the movement mode of the sealing surface (rotational, reciprocating) and the pressure direction to balance the sealing force and friction force. For instance, Y-shaped sealing rings are suitable for high-pressure reciprocating motion, and their double-lip structure can provide bidirectional sealing.
Installation space
The cross-sectional dimensions and compression ratio of the sealing ring should be matched with the installation groove to avoid excessive compression causing excessive friction or insufficient compression leading to leakage. For example, the compression ratio of O-rings is usually controlled at 15%-30%.
Dynamic balance
For rotary seals, the sealing ring needs to be designed through dynamic balance to reduce the vibration and wear caused by centrifugal force. For example, in the sealing of high-speed spindles, the center of mass of the sealing ring needs to coincide with the rotational axis.
Dynamic stability requirements
Low coefficient of friction
The sealing ring needs to reduce dynamic friction, minimize energy loss and heat generation, and extend the sealing life. For instance, polytetrafluoroethylene (PTFE) coatings can significantly reduce the coefficient of friction.
Anti-extrusion property
The sealing ring needs to be prevented from being squeezed into the sealing gap under high pressure, which could lead to wear and leakage. For example, in a high-pressure hydraulic cylinder, a support ring needs to be set on the back of the sealing ring.
Wear compensability
The sealing ring needs to compensate for wear through the self-lubricating property of the material or structural design (such as spring loading) to maintain the contact pressure on the sealing surface. For example, a lip seal with a spring can automatically compensate for lip wear.
Requirements for environmental resistance
Aging resistance
The sealing ring needs to resist aging caused by environmental factors such as ultraviolet rays, ozone and thermal oxidation to maintain stable performance. For example, ethylene propylene rubber (EPDM) has excellent ozone resistance.
Corrosion resistance
The sealing ring needs to maintain its performance in corrosive media such as acids, alkalis and salts to prevent the contamination of the medium by metal corrosion products. For instance, perfluoro rubber (FFKM) is suitable for highly corrosive chemical environments.
Weather resistance
Sealing rings used outdoors need to resist ultraviolet rays, extreme temperature and humidity changes to avoid performance deterioration. For example, silicone rubber sealing rings have stable performance within the range of -60℃ to 200℃.
Installation and maintenance requirements
Easy installation
The sealing ring should be easy to install and replace to reduce downtime and maintenance costs. For example, segmented sealing rings can reduce the installation difficulty.
Status monitoring
The sealing ring needs to support online condition monitoring and provide early warnings of failure risks through technologies such as leakage detection and temperature sensors. For example, in the main pump seal of a nuclear power plant, it is necessary to monitor the leakage volume and temperature in real time.
Maintainability
The sealing ring needs to support regular maintenance, such as lubrication, cleaning and adjustment, to extend its service life. For example, in a hydraulic system, the oil and sealing rings need to be replaced regularly.
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