Oil seal is an important component in agricultural machinery, which is a product used to seal lubricating media. Its main function is to prevent oil leakage and protect bearings; Prevent dust, dirt, and moisture from entering the bearing from the outside. So the quality of the oil seal will directly affect the lifespan of the bearing. Oil leakage from oil seals can cause a decrease in the amount of lubricating oil, affecting the normal operation of machinery. Some oil seals have a lifespan of as long as one year, as short as several months or even three to five days, and are scrapped due to poor sealing and oil leakage. 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 circular oil seals, bowl shaped oil seals, spring-loaded folding oil seals, and floating oil seals. The oil seal must be properly maintained during repair, assembly, and use.

1.1 Circular oil seals (including rubber ring and felt ring oil seals) are generally used at low speeds. The felt ring oil seal is prone to wear, hardening, burning and oil leakage due to prolonged use and lack of oil, and should generally be replaced; If the rubber ring oil seal wears out or hardens during use, it should be replaced.

1.2 Bowl shaped oil seal Bowl shaped oil seal is sealed by being clamped on the shaft neck by a spring clamp. At present, rubber oil seals are mostly made by pressing iron cores and rubber together. Oil seals can leak oil due to wear, hardening, rupture, loss of elasticity, rough surface of the shaft neck, and significant radial runout. If oil leaks due to spring relaxation, the spring can be removed, unscrewed at the interface, cut off an appropriate section of the large end and reassemble it, or simply screw in an additional section to continue use; The oil seal should be replaced with a new one if the bowl mouth is broken or hardened.

1.3 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 the free state, the inner diameter of the lip of the spring-loaded folding oil seal is smaller than the shaft diameter and has a certain degree of interference fit. 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 it inward and press it in. Do not hit or punch it hard to prevent the oil seal from deforming or squeezing the spring and becoming ineffective; If lip curling, spring detachment, and oil seal misalignment occur, they must be removed and reinstalled.

1.4 Floating oil seal Floating oil seal is commonly used in planetary reducers of agricultural machinery, which dynamically seals the end face of the component and has high reliability. Floating oil seals are generally composed of a floating ring made of iron alloy 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 the new oil seal

2.1 The iron shell of the oil seal must not have any dents, and the leather bowl should be securely fastened inside the shell without any looseness; The surface of the leather bowl should be smooth and even, without any oil leakage.

2.2 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.

2.3 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 it. The oil seal of the soft leather bowl should be soaked in engine oil or spindle oil before installation.

2.4 The shaft neck for installing the oil seal should be smooth, flat, and free of scratches and abrasions, otherwise it should be polished smooth; When the wear of the journal exceeds 1 mm, it should be repaired to the standard size. When installing the oil seal, the shaft neck should be coated with engine oil or gear oil to prevent dry friction from damaging the oil seal.

2.5 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 press fitting.

When installing the oil seal, in order to prevent oil leakage, the bowl mouth should face the direction of oil leakage; If the main purpose is to prevent dust from entering the bearing, the bowl mouth should face the side that is prone to dust.

3. Ways to solve oil seal leakage

3.1 Main reasons for oil seal leakage

(1) The oil seal itself is damaged and the spring of the oil seal is loose.

(2) The axial displacement is large, known as displacement pump oil.

(3) Improper operation during assembly can cause the oil seal to twist and deform, and even cause the self tightening spring of the oil seal to fall off and lose, resulting in oil leakage. Not paying attention to cleaning during installation can cause impurities and dust to enter the oil seal, leading to accidental wear of the oil seal.

(4) Agricultural machinery often drives at excessive speeds, causing the working speed of the rotary shaft with oil seals to exceed the adaptive speed of the oil seals, resulting in oil leakage from the seals.

3.2 Solution

(1) Oil seals with self tightening springs, if the cup of the oil seal is not damaged, are mostly due to the spring of the oil seal becoming loose and losing its ability to contract. At this point, the spring of the oil seal can be removed, and the spring can be "disassembled" by removing an appropriate length (approximately 3-5 mm) at the large end of the spring. Then twist the spring in the direction of breaking force, screw the small end into the large end, and use your hand to push forward with force. After repairing, reinstall the spring into the oil seal to solve the oil leakage caused by spring relaxation.

(2) Oil leakage caused by large axial displacement. This needs to be done by moving the front and rear axis to see if the gap is too large. If the axial movement is large, the shaft end with adjusting shims should be appropriately removed 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, it should be appropriately thinned.

(3) During installation, if the outer surface roughness of the shaft neck 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 neck. 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 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, faults 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.

2024 November 3rd Week FK Product Recommendation:

Insert Bearings：

Insert bearings (SKF Y-bearings) are based on sealed deep groove ball bearings in the 62 and 63 series, but have a convex outer ring and in most cases an extended inner ring with a specific locking device, enabling quick and easy mounting onto the shaft.

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