Oil seal installation and maintenance of the whole strategy: to create the perfect sealing defense

I. Careful preparation before installation

Before installation, the pretreatment work of oil seal is crucial, it is to ensure that the oil seal in the subsequent work to play a good sealing performance of the foundation. Between the lips of the oil seal should be appropriately coated with lithium ester with molybdenum disulfide, this operation is like a protective film for the “lips” of the oil seal. Molybdenum disulfide has good lubricating properties and prevents dry wear between the lips and the shaft when the shaft is started momentarily. Dry wear will not only quickly wear the lip, but also affect the original lip surplus, and surplus for the sealing effect of the oil seal plays a key role , once the surplus is affected, the sealing performance of the oil seal will be greatly reduced, resulting in lubricant leakage and other issues. After applying lithium ester, assembly should be carried out as soon as possible to reduce the time the oil seal is exposed to the air and prevent the lithium ester from being contaminated with dust and other impurities.
If the oil seal seat with the oil seal installed is not mounted for a while, protective measures must be taken, and it is recommended to cover it with a clean cloth. This layer of cloth is like wearing a protective clothing for the oil seal seat, can effectively prevent foreign matter attached to the oil seal. Once the foreign matter adheres, the oil seal may be scratched during loading, or the seal structure may be damaged during the operation of the equipment, triggering the seal failure. At the same time, apply lithium grease hand or tool must be kept clean, to avoid mixing impurities into the lithium ester, and then contaminate the oil seal, affecting its performance.
Second, the precise control of the installation process

(A) Installation posture and tool selection
When the oil seal is installed, it must be ensured that it is mounted flat, and absolutely no tilting phenomenon. This is just like building a house, the foundation must be leveled, otherwise the house will be tilted or even collapsed. Tilted installation of the oil seal will lead to its uneven force, in the process of equipment operation, the lip and shaft contact can not be maintained uniformly, so that the sealing performance is greatly reduced, and in serious cases will even lead to rapid damage to the oil seal. Therefore, it is recommended to use hydraulic equipment or socket tools for installation. When using hydraulic equipment, make sure that the pressure is stable and uniform, too much pressure may cause excessive deformation of the oil seal, affecting its normal function; when using the sleeve tool, the size of the sleeve should be accurately matched with the oil seal, and when installing, make sure that the sleeve is perpendicular to the seat of the oil seal, and press the seal into it slowly, so as to make sure that the oil seal is installed in place and maintains a good posture.
(II) Lubrication and shaft end treatment before installation
When installing an oil seal, applying fluid or lubricant is an essential step. This is like adding lubricant to the running parts of the machine, which can effectively reduce the friction between the oil seal and the shaft and reduce the degree of wear. Without lubrication, a large amount of heat will be generated when the oil seal and shaft are in relative motion, accelerating the aging and wear of the oil seal and shortening its service life. Meanwhile, rounding off the shaft end and shoulder is also a very critical operation. The sharp edges of the shaft end and shoulder are like a knife, which may scratch the lip of the oil seal and damage the sealing performance during the installation of the oil seal and the operation of the equipment. After rounding, the shaft end and shoulder are smoother, which can let the oil seal be installed smoothly, and when the equipment is running, the contact with the lip of the oil seal is more uniform, which reduces the local stress concentration, thus prolonging the service life of the oil seal.
(C) Strict confirmation of installation direction
When installing the oil seal, make sure that the lip end is facing the side of the sealed oil, which is a rule that can never be violated. The design of the oil seal is directional, and the special structure of its lip end is to better fit the shaft surface and form an effective seal. If assembled in the reverse direction, it is just like holding the umbrella in the reverse direction, which can’t serve as a rain shield, and the oil seal can’t effectively stop the oil from leaking. Moreover, reverse assembly may also cause the oil seal to be subjected to abnormal forces during the operation of the equipment, accelerating its damage. Before installation, the operator must carefully confirm the correct installation direction of the oil seal, you can observe the logo on the oil seal or refer to the product manual to ensure that the installation direction is correct.
(D) Seat hole installation and use of special tools
When the oil seal is installed into the seat hole, a special tool should be used to push it in, which is a key measure to prevent the position of the oil seal from being skewed. Specialized tools can provide uniform thrust for the oil seal, so that it smoothly into the seat hole. If the special tool is not used, and other tools are used to force it in, it will easily cause the oil seal to shift in the seat hole. After the position of the oil seal is skewed, the fit between it and the seat hole is no longer tight and a gap will appear, which creates conditions for oil leakage. Moreover, the skewed oil seal will be subjected to additional stress during the operation of the equipment, accelerating its wear and damage. Therefore, in the installation process, must use specially designed, and oil seals and seat hole size of the appropriate special tools, to ensure that the oil seal is accurately installed in the seat hole.
(E) Protection and installation of special parts
When the lip of the oil seal passes through the thread, keyway, spline, etc., it is easy to cause damage to the lip of the oil seal due to the complex surface shape of these parts and the existence of sharp edges and bumps. To prevent this from happening, various protective measures are required. For example, a thick layer of grease can be applied to these parts to form a protective film and reduce the direct friction between the lip and these parts; a special protective sleeve can also be used to wrap the threads, keyways, splines, etc., to avoid contact between the lip and them. At the same time, when installing oil seals in these special parts, special tools must be used. Specialized tools can provide the appropriate installation force and installation angle according to the characteristics of these parts to ensure that the oil seal lip passes through safely, and the oil seal is installed firmly to ensure that the sealing performance is not affected.
Third, the key points of disassembly and maintenance

(A) Carefulness in disassembly
When disassembling the oil seal, the operator must always maintain a high degree of concentration and caution. The inner surface of the cavity and the surface of the shaft are like the key components of precision instruments, once bruised, it will have a serious impact on the performance of the whole equipment. For example, the chamber surface bruises may destroy the stability of the fluid flow inside the equipment, resulting in uneven pressure distribution; shaft surface bruises may change the dynamic balance of the shaft, so that the equipment in the operation process produces intense vibration and noise, accelerating the wear and tear of the equipment. Therefore, when disassembling the oil seals, appropriate tools should be used, such as special disassembly pliers or pry bars, and the operation should be gentle, slow, avoid the use of brute force to prevent any damage to these critical surfaces.
(ii) Principle of oil seal replacement
Used oil seals, even if the appearance looks intact, can never continue to use, must be replaced with new oil seals. This is because the oil seal will be affected by various factors in the process of use, such as temperature changes, chemical corrosion of the oil, friction brought about by the high-speed rotation of the shaft. These factors will make the material of the oil seal gradually aging, lose elasticity, and the lip will gradually wear out, resulting in a decline in sealing performance. Even if no obvious damage can be seen from the appearance, its internal structure has actually changed and it can no longer provide a reliable sealing effect. Continuing to use the old oil seals is like continuing to drive a vehicle on a bridge that has already had cracks, which may be dangerous at any time, and will lead to oil leakage, which not only wastes the oil resources, but also may pollute the working environment, and even lead to equipment failure. Therefore, in order to ensure the normal operation and sealing performance of the equipment, this replacement principle must be strictly followed.
(C) shaft surface repair treatment
When the shaft surface bruising or corrosion, it must be repaired in a timely manner. Shaft surface bruises will form uneven traces, these traces will destroy the good contact between the oil seal and the shaft, resulting in seal failure; corrosion will make the shaft surface material deterioration, strength reduction, further affecting the performance of the equipment. For minor bruises, grinding can be used to smooth out the raised parts and restore the shaft surface to smoothness; for deeper bruises, welding repair is required, followed by grinding and polishing treatment. For the rusted parts, first use rust remover to remove the rust, and then according to the degree of corrosion, choose the appropriate repair method, such as spraying antirust paint, plating and so on. After repairing the shaft surface, its roughness and hardness and other parameters must meet the requirements of the equipment to ensure that the new oil seal can be installed and work normally.
(D) Installation skills of new oil seals
When installing new oil seals, using shims to avoid the original friction marks is an important skill. The old oil seal will form specific friction traces between its lip and the shaft surface during the working process, and these traces will make the microstructure of the shaft surface change. If a new oil seal is installed directly in its original position, friction will continue in these already worn areas, resulting in increased wear and shorter service life of the new seal. The use of gaskets can separate the new oil seal from the old traces of friction, so that the new oil seal can establish good sealing contact in the new parts of the shaft surface, reducing wear and prolonging the service life of the oil seal. The material of the gasket should have good abrasion resistance and flexibility, and the thickness should be moderate. When installing the gasket, make sure that the gasket fits flat on the surface of the shaft and fits tightly with the new oil seal, so that it can give full play to its function.