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Basic knowledge of PTFE oil seal
Source:未知|Popularity:0|release date:2020-11-27 15:36:30
At present, nitrile rubber and fluoroelastomer materials are widely used. The former is low in cost, but its temperature resistance and sealing performance is poor, and the leakage is more serious; the latter’s temperature resistance and sealing performance have been significantly improved, but the cost is higher. And it still has some unfavorable commonalities of ordinary rubber materials: such as poor wear resistance, short service life, and particularly sensitive to the eccentric response of the shaft, leakage phenomena are still relatively common.
Filled with polytetrafluoroethylene (PTFE) oil seal instead of lip-shaped rubber oil seal, successfully solved the problem of water and oil leakage of rubber skeleton oil seal.
1. Advantages of PTFE oil seal material
Polytetrafluoroethylene (PTFE), also known as Teflon or Plastic King, is a copolymer of tetrafluoroethylene monomer. It has the following advantages:
(1) Chemical stability: Almost all chemical resistance, strong acids, strong bases or strong oxidants and organic solvents will not work on it.
(2) Thermal stability: The pyrolysis temperature is above 400°C. Therefore, PTFE can work normally in the temperature range of -200℃～300℃.
(3) Antifriction property: The friction coefficient of PTFE material is extremely low, only 0.02, which is 1/40 of rubber.
(4) Self-lubricity: The surface of the PTFE material has outstanding self-lubricity, and almost all viscous substances cannot adhere to its surface.
2. Filling modification of PTFE oil seal
Pure PTFE is not wear-resistant. To make it practical, it must be filled and modified. We use two methods: one is inorganic filling modification, adding glass fiber, carbon fiber, graphite, molybdenum disulfide, etc. to the PTFE. The other is organic filling modification, adding polyphenylene ester, polyphenylene sulfide, etc. to the polytetrafluoroethylene (suitable for water purification, food, medicine sealing). Through filling modification, the wear resistance of polytetrafluoroethylene is increased by 2000 times, and the rigidity and thermal conductivity are increased, so that the oil seal can meet the long life requirement.
3. The principle of PTFE sealing
The PTFE oil seal lip is drawn into a horn shape during processing. Since the PTFE has the memory shrinkage ability after being drawn, the friction heat generated during work will cause the lip to shrink continuously, so the help of a spring is not needed. , It will hug tightly on the shaft, prevent it from having a gap with the shaft surface, and compensate for wear.
4. The advantages of PTFE oil seal
Polytetrafluoroethylene (PTFE) oil seal has the following advantages compared with rubber oil seal:
1). The rubber oil seal adopts a sharp lip compressed by a spring, and the contact surface with the shaft is only 0.3-0.5mm wide. The PTFE oil seal adopts a spring-free wide lip dynamic structure, and the contact surface with the shaft has a width of 5-7mm. Maintain a sufficient oil film, and is not sensitive to the eccentricity of the shaft, and can still work normally under the working condition of 0.4mm radial runout.
2). The inner wall of the PTFE oil seal is engraved with a thread groove opposite to the shaft rotation. When the shaft rotates, an inward thrust is generated to prevent the fluid from flowing out. This thrust is so high that it can seal the fluid pressure of 1.0MPa (single lip) and 3MPa (double lip), and the rubber oil seal is only 0.03MPa.
3). The PTFE oil seal has excellent anti-friction properties, and is especially suitable for oil-free or oil-less work. Even if it is restarted after a long-term shutdown, it can immediately have low friction characteristics.
4). PTFE oil seal is especially suitable for high-speed rotating applications, and the speed can reach 30m/s.
5). Teflon oil seal can be leak-free.
Five, PTFE oil seal application
PTFE oil seals are mainly used in air compressors, engines, gearboxes, motors, pumps, air conditioners, mixers, automated precision machinery, robots, chemical processing equipment, pharmaceutical and food processing equipment, etc., especially suitable for traditional rubber oil seals. Satisfying application.
5. PTFE oil seal installation requirements
The design of PTFE oil seal installation and installation position can refer to NOK oil seal VAJ type or CFW-Simmerring oil seal B2PT type.
PTFE oil seal is a product with high technical content.
Filled with polytetrafluoroethylene (PTFE) oil seal instead of lip-shaped rubber oil seal, successfully solved the problem of water and oil leakage of rubber skeleton oil seal.
1. Advantages of PTFE oil seal material
Polytetrafluoroethylene (PTFE), also known as Teflon or Plastic King, is a copolymer of tetrafluoroethylene monomer. It has the following advantages:
(1) Chemical stability: Almost all chemical resistance, strong acids, strong bases or strong oxidants and organic solvents will not work on it.
(2) Thermal stability: The pyrolysis temperature is above 400°C. Therefore, PTFE can work normally in the temperature range of -200℃～300℃.
(3) Antifriction property: The friction coefficient of PTFE material is extremely low, only 0.02, which is 1/40 of rubber.
(4) Self-lubricity: The surface of the PTFE material has outstanding self-lubricity, and almost all viscous substances cannot adhere to its surface.
2. Filling modification of PTFE oil seal
Pure PTFE is not wear-resistant. To make it practical, it must be filled and modified. We use two methods: one is inorganic filling modification, adding glass fiber, carbon fiber, graphite, molybdenum disulfide, etc. to the PTFE. The other is organic filling modification, adding polyphenylene ester, polyphenylene sulfide, etc. to the polytetrafluoroethylene (suitable for water purification, food, medicine sealing). Through filling modification, the wear resistance of polytetrafluoroethylene is increased by 2000 times, and the rigidity and thermal conductivity are increased, so that the oil seal can meet the long life requirement.
3. The principle of PTFE sealing
The PTFE oil seal lip is drawn into a horn shape during processing. Since the PTFE has the memory shrinkage ability after being drawn, the friction heat generated during work will cause the lip to shrink continuously, so the help of a spring is not needed. , It will hug tightly on the shaft, prevent it from having a gap with the shaft surface, and compensate for wear.
4. The advantages of PTFE oil seal
Polytetrafluoroethylene (PTFE) oil seal has the following advantages compared with rubber oil seal:
1). The rubber oil seal adopts a sharp lip compressed by a spring, and the contact surface with the shaft is only 0.3-0.5mm wide. The PTFE oil seal adopts a spring-free wide lip dynamic structure, and the contact surface with the shaft has a width of 5-7mm. Maintain a sufficient oil film, and is not sensitive to the eccentricity of the shaft, and can still work normally under the working condition of 0.4mm radial runout.
2). The inner wall of the PTFE oil seal is engraved with a thread groove opposite to the shaft rotation. When the shaft rotates, an inward thrust is generated to prevent the fluid from flowing out. This thrust is so high that it can seal the fluid pressure of 1.0MPa (single lip) and 3MPa (double lip), and the rubber oil seal is only 0.03MPa.
3). The PTFE oil seal has excellent anti-friction properties, and is especially suitable for oil-free or oil-less work. Even if it is restarted after a long-term shutdown, it can immediately have low friction characteristics.
4). PTFE oil seal is especially suitable for high-speed rotating applications, and the speed can reach 30m/s.
5). Teflon oil seal can be leak-free.
Five, PTFE oil seal application
PTFE oil seals are mainly used in air compressors, engines, gearboxes, motors, pumps, air conditioners, mixers, automated precision machinery, robots, chemical processing equipment, pharmaceutical and food processing equipment, etc., especially suitable for traditional rubber oil seals. Satisfying application.
5. PTFE oil seal installation requirements
The design of PTFE oil seal installation and installation position can refer to NOK oil seal VAJ type or CFW-Simmerring oil seal B2PT type.
PTFE oil seal is a product with high technical content.