Oil seal is an important component in agricultural machinery, which is a product used to seal the lubricating medium. Its main functions are: to prevent oil leakage and protect bearings; Prevent dust, dirt, and moisture from soaking into the bearing from the outside. So the quality of oil seals will directly affect the lifespan of bearings. Oil seal leakage can cause a decrease in the amount of lubricating oil, affecting the normal operation of the machinery. Some oil seals have a lifespan of up to a year, a few months, or even three to five days, and are scrapped due to oil leakage due to poor sealing. This situation seriously affects the efficiency of agricultural machinery, not only increasing fuel consumption and production costs, but also polluting the environment.
1. Classification and usage requirements of oil seals
Oil seals generally include annular oil seals, bowl shaped oil seals, spring folding oil seals, and floating oil seals. The oil seal must be properly maintained during repair, assembly, and use.
(1) Annular oil seals (including rubber rings and felt ring oil seals) are generally used at low speeds. Due to prolonged use and lack of oil, the felt ring oil seal is prone to wear, hardening, burning, and oil leakage, and should generally be replaced; If the rubber ring oil seal is worn or hardened during use, it should be replaced.
(2) Bowl shaped oil seal Bowl shaped oil seal plays a sealing role by clamping it onto the journal with a spring. At present, most rubber oil seals are made of iron core and rubber pressed together. Oil seals can leak due to wear, hardening, rupture, loss of elasticity, rough surface of the journal, and large radial runout. If there is oil leakage due to spring relaxation, the spring can be taken out, unscrewed at the interface, and the large end can be cut off to a suitable section for reassembly or directly screwed into an additional section for continued use; If the oil seal is cracked or hardened at the bowl mouth, it should be replaced with a new one.
(3) Spring type folding oil seal The main feature of spring type folding oil seal is that the spring is the main component of the oil seal. In a free state, the inner diameter of the spring type folding oil seal lip is smaller than the shaft diameter and has a certain amount of interference. After installation, the interference pressure of the oil seal blade and the contraction force of the self tightening spring generate a certain radial force on the rotating shaft. When installing the oil seal, rotate the oil seal inward and press it in. Do not forcefully hit or punch it to prevent the oil seal from deforming or crushing the spring and causing it to fail; If there is lip flange, spring detachment, and oil seal deviation, it must be removed and reinstalled.
(4) Floating oil seal Floating oil seal is often used for planetary reducers in the walking part of agricultural machinery, which dynamically seals the end face of this component and has high reliability. Floating oil seals generally consist of a floating ring made of ferroalloy material and a matching nitrile rubber O-ring seal. Floating rings are used in pairs, one rotating with the rotating component and the other relatively stationary.
2. Requirements for replacing a new oil seal
(1) The iron shell of the oil seal should not have any dents, and the leather cup should be tightened inside the shell without looseness; The surface of the leather bowl should be smooth and flat, without any oil leakage.
(2) There should generally be a gap of 0.5 mm between the oil seal pressure ring and the edge of the cup, but it should not be greater than the radius of the spring.
(3) Before installation, the oil seal of the hard leather bowl should be heated to 40-50 ℃ in spindle oil, animal oil, or a mixture of 50% engine oil and 50% kerosene to soften. The oil seal of the soft leather bowl should be soaked in engine oil or spindle oil before installation.
(4) The journal of the oil seal installation should be smooth, flat, and free from scratches and scratches, otherwise it should be polished smooth and clean; When the journal wear exceeds 1mm, it should be repaired to the standard size. When installing the oil seal, the journal should be coated with engine oil or gear oil to prevent dry friction from damaging the oil seal.
(5) The oil seal housing should be tightly placed in the oil seal seat, and there should be no oil leakage at its contact point. It is not allowed to squeeze the oil seal housing during pressing.
(6) When installing the oil seal, to prevent oil leakage, the bowl mouth should be facing the direction of the oil leakage; If the main purpose is to prevent dust from entering the bearings, the bowl mouth should face the side that is prone to dust ingress.
3. Solution to Oil Seal Leakage
3.1 The main reasons for oil seal leakage
(1) The oil seal itself is damaged and the spring of the oil seal is loose.
(2) There is a large amount of axial forward and backward movement, which is called displacement pump oil.
(3) Improper operation during assembly can cause distortion and deformation of the oil seal, even causing the self tightening spring of the oil seal to fall off and lose, resulting in oil leakage. Failure to pay attention to cleanliness during installation can cause impurities and dust to enter the oil seal, causing accidental wear of the oil seal.
(4) Agricultural machinery often exceeds the speed limit, causing the working speed of the rotating shaft on which the oil seal is installed to exceed the adaptive speed of the oil seal, resulting in oil leakage from the oil seal.
3.2 Solution
(1) Oil seals with self tightening springs, such as oil seal cups that are not damaged, are mostly due to loose springs in the oil seal and loss of contraction ability. At this point, the spring of the oil seal can be removed, and the spring can be "broken open", with an appropriate length (approximately 3-5 mm) removed from the large end of the spring. Then twist the spring in the direction of breaking force, insert the small end into the large end, and then use your hand to drive forward. After repairing, reinstalling the spring into the oil seal can solve the oil leakage caused by spring relaxation.
(2) Oil leakage caused by large axial movement. This needs to be done by moving the front and back axially to see if there is too much clearance. If there is a large amount of axial movement, it is necessary to remove the shaft end with adjusting shims appropriately to reduce the thickness. If the fixed nut at the shaft end is loose, tighten the nut. If the sealing gasket of the original shaft end cover is too thick, make an appropriate amount of thinning.
(3) During installation, if the outer surface of the journal has low roughness or defects such as rust, rust, and burrs, it should be polished smooth with a fine sandcloth or oilstone; Apply clean engine oil or lubricating grease to the corresponding position of the oil seal lip or journal. Apply sealant to the outer ring of the oil seal, wrap the keyway area on the shaft with hard paper to avoid scratching the oil seal lip. Use a special tool to rotate the oil seal inward and press it in. Do not forcefully hit or punch it to prevent the oil seal from deforming or breaking the spring and causing it to fail; If there is lip flange, spring detachment, and oil seal deviation, it must be removed and reinstalled. It should be noted that when the journal is not worn and the oil seal spring has sufficient elasticity, do not tighten the inner spring without authorization.
(4) For components that generate abnormal heat, the fault should be promptly resolved to avoid mechanical overspeed and overload operation, in order to prevent the temperature of the oil seal lip from rising, rubber aging, and early wear of the lip.
2023 New Week VAFEM product Recommendation:
Agricultural bearings：
Agricultural machinery requires better seals for contaminated conditions, provisions for misalignment, and economical mountings for shafts and housings. VAFEM offers bearings for disc harrows, planters, mowers, rakes, all types of balers, tillage, seeding and forage harvester equipment, combines, cotton pickers/stripers, and other agricultural equipment like silo unloaders and grain elevators.
We also offer a complete line of insert ball bearings, shaft mounted with either tapered adapters or locking collar or set screws. Our proven seal designs include low torque shields to heavy-duty triple lip seals. Disc harrow bearings are also available with either round, square, or hexagonal bores. All bearings are available with or without re-lubrication holes.
https://www.vafem.com/products/Agricultural-Bearings/775.html
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