Oil seal is a common term for sealing components, simply put, it refers to the sealing of lubricating oil. It is a mechanical component used to seal grease (oil is the most common liquid substance in transmission systems, and also refers to general liquid substances). It isolates the parts that need lubrication in the transmission components from the output components, so as not to allow lubricating oil to leak. The sealing components used for static and dynamic sealing (usually reciprocating motion) are called oil seals.
The representative form of oil seal is TC oil seal, which is a double lip oil seal with self tightening spring completely covered by rubber. Generally speaking, oil seal refers to this type of TC skeleton oil seal
classification
Oil seals are generally divided into single type and assembled type. The assembled type allows the skeleton and lip material to be freely combined and is generally used for special oil seals.
Oil seals can be classified into various forms and different names based on their sealing function, characteristics, structural types, working conditions, and sealing mechanisms. However, it is customary to refer to rotating shaft lip seals as oil seals, and static seals and dynamic seals (usually reciprocating motion) as seals.
The representative form of oil seal is TC oil seal, which is a double lip oil seal with self tightening spring completely wrapped in rubber. Generally speaking, oil seal refers to this type of TC skeleton oil seal.
Functional purpose
Engine: crankshaft - crankshaft front and rear oil seals valves - valve oil seals (engine repair kit O-ring) (distributor oil seal, water pump oil seal, balance shaft oil seal, oil pump oil seal...); Camshaft - Camshaft oil seal; Transmission: Transmission - front and rear oil seals, shift lever oil seals (transmission repair kit O-ring) (transfer case - front and rear oil seals); Rear axle: Half axle - Rear axle oil seal differential - (front) rear angle arrow oil seal Rear wheel oil seal Front wheel oil seal Steering gear oil seal (steering gear repair kit O-ring) Direction booster oil seal (front half axle oil seal).
Any part of the operating body box that has liquid lubricating oil and is connected to the outside requires oil seals. Some are rubber, some are metal, and most are steel reinforced rubber, such as crankshaft rear oil seal, transmission front and rear oil seal, left and right half shaft oil seal, main reducer front oil seal, air compressor crankshaft oil seal, etc.
Note
1. Preparation and precautions before startup
a, Conduct a comprehensive inspection of the mechanical seal, as well as the installation of auxiliary devices and pipelines, to ensure that they are complete and meet the technical requirements.
b, Perform a static pressure test before starting the mechanical seal to check for any leakage. If there are many leaks, the cause should be investigated and efforts should be made to eliminate them. If it is still ineffective, it should be disassembled, inspected, and reinstalled. The general static pressure test pressure is 2-3 kilograms per square centimeter.
c, Rotate the pump towards the turning wheel and check if it is light and even. If the turning gear is difficult or stationary, the assembly dimensions should be checked for errors and the installation should be reasonable.
2. Installation and shutdown
a, Before starting, the sealed chamber should be filled with liquid. When transporting solidified media, steam should be used to heat the sealed chamber and melt the media. Before starting, it is necessary to turn the car to prevent sudden starting from causing the soft ring to break.
b, For mechanical seals that utilize the pump's external sealing oil system, the sealing oil system should be started first. Stop the oil sealing system after parking.
c, After the hot oil pump is shut down, the cooling water for the sealing chamber and end face seal cannot be stopped immediately. The cooling water should be stopped only when the oil temperature at the end face seal drops below 80 degrees to avoid damaging the sealing parts.
3. Operation
a, If there is a slight leakage after the pump is started, it should be observed for a period of time. If the leakage does not decrease after running continuously for 4 hours, the pump should be stopped for inspection.
b, The operating pressure of the pump should be stable, with pressure fluctuations not exceeding 1 kilogram per square centimeter.
c, During the operation of the pump, the phenomenon of vacuum should be avoided to prevent dry friction and seal damage on the sealing surface.
d, The sealing condition should be checked regularly. During operation, when the leakage exceeds the standard, the heavy oil should not exceed 5 drops/minute and the light oil should not exceed 10 drops/minute. If there is still no improvement trend within 2-3 days, the pump should be stopped to check the sealing device.
Problem and Reason
The main factors causing oil seal leakage
Poor sealing of oil seals is the main factor causing oil leakage. When the shaft wears out and forms grooves, even if a new oil seal is replaced, it cannot be sealed. This is because the contact pressure between the oil seal lip and the shaft decreases, resulting in a small interference fit between the oil seal lip diameter and the shaft diameter after installation.
Taking the S195 diesel engine crankshaft oil seal as an example, the main reasons for its poor sealing are analyzed as follows:
① Poor quality of oil seal manufacturing;
② Poor quality of shaft or bearing;
③ Improper use and maintenance;
④ Improper installation;
⑤ Improper storage can cause adverse effects due to environmental pollution.
Countermeasures for oil leakage caused by inadequate sealing of oil seals
1. Master and identify the basic knowledge of counterfeit products, and choose high-quality and standard oil seals.
2. During installation, if the outer surface roughness of the shaft diameter is low or there are defects such as rust spots, rusting, fuzzing, etc., it should be polished smooth with a fine sandpaper or oilstone; Apply clean engine oil or lubricating grease to the corresponding position of the oil seal lip or shaft diameter. Apply sealant to the outer ring of the oil seal, wrap the keyway on the shaft with hard paper to avoid scratching the lip of the oil seal, and use a special tool to rotate and press the oil seal inward. Do not forcefully hit or punch it to prevent deformation of the oil seal or breakage of the spring and failure; If lip curling, spring detachment, and oil seal misalignment occur, they must be removed and reinstalled. It should be noted that when the shaft diameter is not worn and the oil seal spring has sufficient elasticity, do not tighten the inner spring without authorization.
3. Oil seals used in machinery generally work under harsh conditions, with large temperature differences, high levels of dust, and frequent machine vibrations that constantly change the stress conditions of the components. Therefore, it is necessary to regularly inspect, maintain, and upkeep them.
4. Serious wear of shaft diameter and bearings; Oil seal rubber aging or spring failure should be repaired and corresponding components replaced in a timely manner.
5. Timely troubleshooting of components or assemblies that generate abnormal heat; Avoid mechanical overspeed and overload operation to prevent the temperature rise of the oil seal lip, rubber aging, and early wear of the lip.
6. Regularly check the oil level. If there are too many impurities in the oil, such as alloy powder or metal shavings, it is necessary to completely replace the oil with a new one. The brand and quality of the changed oil should meet the requirements of the season. It is recommended to add Maitre Super Sealing Compound&Lubricant to the engine oil. It is an excellent gearbox additive that can form an inert material film on the components. It can slow down oil seal leakage, extend the service life of oil sealed gears, and reduce gearbox noise. The use of Maitre Super Sealing Lubricant will not pollute or deteriorate the oil.
Usage guide:
① When the lubricating oil volume of the reducer is ≤ 7 liters, the amount of lubricating oil added per liter is 20-30ml;
② When 7-15 liters, the addition amount is 15-20ml per liter of lubricating oil;
③ When the volume exceeds 15 liters, the addition amount is 10ml per liter of lubricating oil;
7. Temporarily unused oil seals should be properly stored to prevent them from getting stained with oil, dust, or direct sunlight.
8. When the shaft diameter wears into a "V" - shaped groove, causing a decrease in contact pressure between the new oil seal lip and the shaft and unable to seal the oil, displacement can be used to compensate
Advantage
1. The oil seal structure is simple and easy to manufacture. Simple oil seals can be molded in one go, and even the most complex oil seals have a simple manufacturing process. Metal skeleton oil seals can also be formed by stamping, bonding, inlaying, molding and other processes to combine metal and rubber into the required oil seal.
2. Oil seals are lightweight and require minimal consumables. Each type of oil seal is a combination of thin-walled metal and rubber parts, which consumes very little material, so the weight of each oil seal is very light.
3. The installation position of the oil seal is small, the axial dimension is small, it is easy to process, and it makes the machine compact.
4. Oil seals have good sealing function and a long service life. Has certain adaptability to machine vibration and spindle eccentricity.
5. The oil seal is easy to disassemble and easy to inspect.
6. Oil seals are cheap in price.
