Sealing materials are the basis for achieving leakage prevention. Commonly used materials such as nitrile rubber (NBR), fluororubber (FKM) and polyurethane (PU) each have their own characteristics and applicable scenarios. Nitrile rubber has low cost and good oil resistance, and is suitable for conventional hydraulic systems; fluororubber has excellent high temperature resistance and chemical corrosion resistance, and performs outstandingly in high temperature and strong corrosion environments; polyurethane is known for its high wear resistance and high strength, and is suitable for high pressure and high frequency reciprocating motion conditions. In addition, new composite materials such as the combination of polytetrafluoroethylene (PTFE) and rubber have both low friction coefficient and good sealing performance. By accurately selecting materials according to the working pressure, temperature, medium and other conditions of the hydraulic cylinder, the sealing performance and service life are guaranteed from the source.
A single sealing structure is difficult to meet the needs of complex working conditions, and multiple structures are often used for collaborative design. The lip seal structure forms a seal by relying on the interference fit between the lip and the sealing surface. Its self-tightening effect can enhance the sealing effect as the pressure increases. It is often used for piston rod sealing. The O-ring has a simple structure and low cost. It fills the gap by extrusion deformation and is widely used in static sealing and some dynamic sealing scenarios. The combined seal integrates the advantages of multiple materials and structures. For example, the Gly ring is composed of a polytetrafluoroethylene slide ring and a rubber elastomer, which not only reduces friction resistance, but also can withstand high pressure, significantly improving the reliability and service life of the seal. The combination of different sealing structures can provide adaptation solutions for different parts of the hydraulic cylinder (cylinder, piston, piston rod).
In order to cope with the pressure changes during the operation of the hydraulic cylinder, the sealing structure needs to have pressure self-adaptation capability. The sealing design assisted by elastic elements (such as springs and rubber bodies) can automatically adjust the contact pressure between the seal and the sealing surface when the pressure fluctuates. For example, a spring-loaded slide ring is set in the piston seal. When the system pressure decreases, the spring provides additional pressure to ensure the sealing surface fits; when the pressure increases, the slide ring is further compressed under the action of the medium pressure to enhance the sealing effect. This design can not only effectively prevent leakage, but also reduce the wear of the seal caused by excessive extrusion and extend its service life.
The wear of the seal is a key factor affecting the service life. The wear rate can be reduced by optimizing the friction characteristics of the sealing structure. On the one hand, low-friction materials and surface treatment technologies are used, such as coating a molybdenum disulfide lubricating layer on the surface of the seal or performing surface polishing to reduce the friction resistance with the moving parts; on the other hand, a reasonable sealing gap and contact area are designed to avoid abnormal wear caused by over-tightening or over-loosening. In addition, setting a lubrication groove or introducing a self-lubricating material in the sealing structure can form a stable lubricating film, reduce frictional heat generation and wear, and thus improve the durability of the seal.
Complex working environments (such as high temperature, humidity, and dust) will accelerate the aging and failure of seals. For high-temperature environments, high-temperature resistant materials are selected and the heat dissipation structure is optimized to prevent the seal from softening or aging due to high temperature; in humid and dusty environments, auxiliary protective structures such as dustproof rings and waterproof sealing sleeves are added to block the invasion of external impurities and prevent impurities from causing scratches or wear on the sealing surface. At the same time, the sealing structure is treated with anti-corrosion, such as using a stainless steel sealing gland or galvanizing or nickel-plating metal parts to enhance its corrosion resistance and ensure that it can maintain high efficiency and anti-leakage performance in harsh environments.
The performance of the sealing structure depends on high-precision manufacturing and assembly. In the machining process, the inner hole cylindricality and surface roughness of the hydraulic cylinder cylinder, piston and other parts are strictly controlled to ensure that the sealing surface is flat and smooth and reduce the risk of leakage. During the assembly process, follow the standardized operating procedures to control the installation stress of the seal to avoid deformation or damage of the seal due to improper assembly. At the same time, advanced detection technology (such as sealing test and pressure test) is used to fully inspect the assembled hydraulic cylinder to timely discover and correct potential leakage hazards and ensure the reliability of the sealing structure.
With the development of industrial intelligence, it has become a trend to integrate sensors in the sealing structure to realize leakage monitoring and life prediction. Pressure sensors and flow sensors can monitor the working parameters of the hydraulic cylinder in real time. Once abnormal pressure fluctuations or flow leakage occur, the system will immediately alarm and locate the leakage position. In addition, big data analysis and machine learning algorithms are used to analyze the wear data and working environment data of the seals, predict the remaining service life of the seals, and perform maintenance or replacement in advance to avoid equipment failures caused by seal failure, further improving the operating safety and reliability of the hydraulic cylinder.
