Oil seals are generally divided into monomer type and assembly type. Assembled type is that the frame and lip material can be freely combined, and they are generally used for special oil seals.
From the sealing function, characteristics, structure type, working state and sealing mechanism of oil seals, it can be divided into various forms and different names. However, it is customary to call the rotary shaft lip seal ring oil seal, static seal and dynamic seal (generally reciprocating motion). ) Seals are called seals.
The representative form of the oil seal is the TC oil seal, which is a double-lip oil seal with a self-tightening spring covered with rubber. Generally speaking, the oil seal often refers to this tc skeleton oil seal. For a schematic diagram of the skeleton oil seal, refer to the figure.
Commonly used materials for oil seals are: nitrile rubber, fluorine rubber, silicone rubber, acrylic rubber, polyurethane, polytetrafluoroethylene and so on.
1. Nitrile rubber (NBR) It has good heat resistance, wear resistance, resistance to various lubricating oils, greases, oil and gas mixtures, etc., and the applicable temperature is -30 to 120 degrees Celsius, but it cannot be used in phosphate ester hydraulic oils and gear oils containing extreme pressure additives. Used in medium, stable performance in gasoline and mineral oil with low aniline point.
2. Polyacrylate rubber (ACM) Excellent oil and heat resistance, abrasion resistance, ozone resistance, UV radiation resistance, especially resistance to lubricants, gear oils, motor oils, engine oils, petroleum hydraulic oils, etc. containing extreme pressure fluids, suitable for -30~150 degrees Celsius Scope work.
3. Fluorine rubber It is resistant to aging, heat and oil, and is suitable for almost all lubricating oils, fuel oils and gasolines. It is not easy to harden in oils containing extreme pressure additives, but it has poor cold resistance and high temperature wear resistance, and large permanent compression deformation. The temperature is -20~250 degrees Celsius.
4. Silicone rubber With outstanding resistance to high and low temperature, it can be used for a long time at 150 degrees Celsius without performance changes; it can be used continuously for 10000h at 200, and it can maintain its unique flexibility and ozone resistance within the working temperature range of -70~260. Weather and other advantages.
5. PTFE It has outstanding chemical stability, thermal stability, friction reduction and self-lubricity, and its cracking temperature is above 400. Therefore, it can work normally in the temperature range of -200~300 degrees Celsius. In addition to free fluorine and alkali metals, it has excellent corrosion resistance to chemicals, solvents, hydroxides and acids.
Nitrile rubber and fluoroelastomer materials are widely used oil seals. The former is low in cost, but the temperature resistance and sealing performance are 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, particularly sensitive to the eccentric response of the shaft, etc. Leakage is still common.
PTFE oil seal is a product with high technical content, and it is the future direction of oil seal development. When selecting the material of the oil seal, the compatibility of the material to the working medium, the adaptability to the working temperature range, and the ability of the lip to follow the rotating shaft during high-speed rotation must be considered.
Generally, the temperature of the lip of the oil seal is 20~50℃ higher than the temperature of the working medium when the oil seal is working, and attention should be paid when selecting the oil seal material. The working range of the oil seal is related to the material used in the oil seal: -40~120℃ when the material is nitrile rubber (NBR), -30~180℃ for acrylic rubber (ACM), and -25~300℃ for fluorine rubber (FPM).