As an essential component in the industrial field, seals are like tiny gears in precision instruments. Although they may seem insignificant, they play a crucial role in ensuring the normal operation of equipment, preventing leaks, and maintaining production safety. There are various types and functions of seals, each with its unique design and applicable scenarios. Below, we will provide you with a detailed introduction to common types of seals. Static seals are mainly used between relatively stationary joint surfaces to prevent fluid or gas leakage.
Common static seals include the following:
1. Gasket sealing: Gasket sealing is one of the most commonly used forms of static sealing, which can be divided into non-metallic gaskets, metal gaskets, metal composite gaskets, and wound gaskets according to material differences. Non metallic gaskets, such as asbestos gaskets, rubber gaskets, polytetrafluoroethylene (PTFE) gaskets, etc., have good flexibility and corrosion resistance, and are suitable for sealing scenarios with low pressure, room temperature, or corrosive media. Metal gaskets, such as copper gaskets, aluminum gaskets, stainless steel gaskets, etc., have high strength and high temperature resistance, and are suitable for high-pressure and high-temperature environments. Metal composite gaskets, such as metal coated gaskets and corrugated metal composite gaskets, combine the advantages of metal and non-metal materials, with excellent sealing performance and pressure bearing capacity. Spiral wound gaskets are made by alternately winding metal strips and non-metallic materials (such as graphite and PTFE), with excellent elasticity and resilience, and can be used for sealing under various pressure and temperature conditions.
2. O-ring seal: O-ring is a circular annular seal with a circular cross-section, which is widely used in various static and dynamic sealing applications. Its materials are rich and diverse, including rubber, fluororubber, silicone rubber, polytetrafluoroethylene, etc. The O-ring has a simple structure, easy installation, and reliable sealing, and can adapt to various media and pressure conditions.
3. Flat sealant: Flat sealant is a liquid or semi-solid sealing material that forms a sealing layer by being applied between two mating surfaces. It has excellent filling and adhesion properties, which can fill the unevenness and small gaps of the joint surface. Flat sealant is suitable for low pressure, room temperature, or situations that require quick installation. Dynamic seals are used between components that move relative to each other.
Common types of dynamic seals include:
1. Mechanical seals: Mechanical seals rely on the tight fit between elastic elements and sealing end faces to achieve sealing, with low leakage, long service life, and strong adaptability. They are widely used in shaft seals of pumps, compressors, mixers, and other equipment. According to different structural forms, it can be divided into single end mechanical seals, double end mechanical seals, balanced mechanical seals, and unbalanced mechanical seals.
2. Packing seal: Packing seal achieves sealing through the tight fit and frictional resistance between the packing and the shaft (or rod). Its structure is simple, easy to install, and cost-effective, suitable for low-pressure, room temperature, or media containing solid particles. Common filler materials include asbestos rope, carbon fiber, polytetrafluoroethylene, etc. To improve sealing performance and extend service life, packing seals generally use multi-layer combinations and pre tightening devices.
3. Lip seal: Lip seal achieves sealing by the contact pressure and fluid dynamic effect between the sealing lip and the shaft (or rod), with low friction resistance, good sealing effect and strong adaptability. It is widely used in the piston rod sealing part of hydraulic cylinders, cylinders and other equipment. Its materials are diverse, including rubber, polyurethane, polytetrafluoroethylene, etc. According to different structural forms, it can be divided into one-way lip seals, two-way lip seals, lip seals with dust rings, etc.
4. Combination seal: Combination seal combines multiple sealing forms together to achieve better sealing effect and adapt to more complex working conditions. In the field of oil drilling and production equipment, common forms of combination seals include the combination of mechanical seals and packing seals, as well as the combination of lip seals and O-rings.
Other types of seals:
1. Rotary oil seal: mainly used for sealing rotating shafts, it can effectively prevent lubricating oil leakage and block external pollutants from entering. Common materials include nitrile rubber (NBR), fluororubber (FKM), and polytetrafluoroethylene (PTFE). Some high-end products use metal skeleton reinforced structures and are widely used in transmissions, engines, industrial gearboxes, wind power spindles, etc.
2. Skeleton sealing: It usually integrates multiple sealing lips and dust-proof structures, suitable for heavy-duty conditions such as engineering machinery axles, agricultural machinery wheel hubs, mining equipment, etc. It has strong resistance to sediment and impact, and a long service life.
3. Hydraulic seals: including piston seals, rod seals, guide rings, V-shaped cloth oil seals, etc. The materials are mostly polyurethane (PU), polytetrafluoroethylene (PTFE) composite rubber, which can withstand high pressure (up to 40MPa) and frequent reciprocating motion in hydraulic cylinders, injection molding machines, and metallurgical equipment.
4. Pneumatic seal: applied to pneumatic systems, which have low pressure but fast operating frequency. Common forms include piston seals, rod seals, buffer seals, etc. The material is mostly nitrile rubber (NBR), which plays a role in the drive units of cylinders, robotic arms, valve control, and other aspects of automated production lines.
5. Combination gasket: Suitable for static sealing connections, such as pipeline flanges, heat exchangers, etc. The material is usually composed of metal, nitrile rubber, polytetrafluoroethylene, etc. The temperature resistance range can cover -65 ℃ to+260 ℃. Different types of seals have their own characteristics in terms of material, structure, and performance, and are suitable for different working conditions and industry needs. In practical applications, it is necessary to select sealing components reasonably based on specific working conditions such as pressure, temperature, medium characteristics, and equipment movement mode to ensure efficient and stable operation of the equipment and prevent leakage and other problems.