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Analysis of Seal Leakage of Roller
by：Laike
2020-07-18
The heavy wheel is an important load-bearing component of the crawler construction machinery (commonly referred to as the 'lower roller'). It is composed of a roller body, a supporting shaft, left and right support seats, and sealing components. The support shaft is fixed on the trolley frame through the left and right support seats, and there is a press-fitted bushing in the bore of the wheel body to rotate with the support shaft. A sealing assembly is installed between the rotating wheel body and the fixed left and right support seats to maintain the support shaft Sealed with lubricating oil in shaft sleeve and other parts. The sealing assembly is composed of a pair of double-cone metal material sealing rings and two nitrile rubber fixed compression rings. The rubber ring is installed in the sealing seat of the wheel body and the support seat respectively. Since the metal seal ring bears the squeeze of the rubber ring to ensure that its annular blade belt is tightly engaged during rotation, the seal is a floating seal type.
roller is an important load-bearing component of crawler-type construction machinery (commonly known as 'lower roller'), which consists of roller body, shaft, left and right bearing seats and sealing components and other components. The support shaft is fixed on the trolley frame through the left and right support seats, and there is a press-fitted bushing in the bore of the wheel body to rotate with the support shaft. A sealing assembly is installed between the rotating wheel body and the fixed left and right support seats to maintain the support shaft Sealed with lubricating oil in shaft sleeve and other parts. The sealing assembly is composed of a pair of double-cone metal material sealing rings and two nitrile rubber fixed compression rings. The rubber ring is installed in the sealing seat of the wheel body and the support seat respectively. Since the metal seal ring bears the squeeze of the rubber ring to ensure that its annular blade belt is tightly engaged during rotation, the seal is a floating seal type.
In 1995, our factory produced supporting wheels for a company's excavator. The company provided foreign production drawings, and the floating oil seal components were imported from abroad. During the installation test, it was found that some of the rollers leaked oil at the floating oil seal. After many inspections, analyses and tests, it was finally found that the tapered angle of the company's floating seal assembly and its seat ring mouth was significantly smaller than that produced by our factory. The angle of other types of oil seals; through drawing calculations, the compression of the rubber ring is too large.
We believe that the tapered angle of the floating oil seal is small, which reduces the jump of the floating seal ring engagement ring caused by the external impact of the roller, improves the axial force of the seal engagement surface and keeps its axial force independent of the system shaft. It is beneficial to make the gap larger and change sharply. However, the sealing cone angle becomes smaller, it is easy to cause the rubber ring to skew on the cone surface when the roller is assembled, and the compression amount of the sealing seat on the rubber ring is increased, it is more difficult to ensure the correct position of the sealing engagement blade in the assembly. Analysis of the relevant data of some advanced companies in the world shows that the oblique angle of the cone surface of the floating oil seal becomes smaller, which is a development trend in design.
Based on the above analysis, we have taken two measures:
(l) The parameters of the originally designed floating oil seal sealing ring, such as the taper and the taper angle of the rubber ring seat, remain unchanged, and the compression of the sealing rubber ring is appropriately changed with the simplest design changes.
( 2) Improve the assembly process and add special tools to ensure the correct position of the floating oil seal rubber ring on the sealing ring cone surface and the correct position of the sealing seat installed to ensure the correct engagement of the two sealing ring cutting edges.
After strict assembly according to the above measures, no matter whether it is a test or an installed use, no leakage is found.
We believe that in order to improve the service life of the floating seal assembly of the rollers of the construction machinery walking mechanism, foreign companies reduce the tapered angle of the sealing ring and the tapered angle of the rubber ring seat, theoretically and practically It is advantageous to see it, but if the assembly cannot be guaranteed to be accurate in place during the manufacturing process, it will go against the wish.
If the assembly of the floating seal assembly is incorrect, the factory will perform airtightness inspection at the static original position, but due to the elasticity of the rubber ring, the airtightness inspection pressure cannot reach the equivalent value when the pressure does not reach a considerable value. There will be no leakage. After a certain period of time, due to the frictional heating of various parts and the increase of the internal cavity pressure to a certain value, the rotating meshing position due to the elastic force of the rubber ring makes the blade belt at this point. The instantaneous leakage; if the rotation stops under this condition, the leakage at the meshing point is not instantaneous but serious oil leakage occurs, and continues until the pressure of the inner cavity drops to a certain value and the elasticity of the rubber ring reaches a new balance. stop.
In the wrong state of assembly, there will also be local blade surfaces during operation due to increased friction and wear due to pressure ambassadors, and at the same time, heat is rapidly generated, resulting in reduced viscosity of the lubricating oil and increased wear of each rotating pair.
The above analysis shows that, in addition to advanced design and high-quality parts processing and production, a high-quality component, correct and perfect assembly is very important.
roller is an important load-bearing component of crawler-type construction machinery (commonly known as 'lower roller'), which consists of roller body, shaft, left and right bearing seats and sealing components and other components. The support shaft is fixed on the trolley frame through the left and right support seats, and there is a press-fitted bushing in the bore of the wheel body to rotate with the support shaft. A sealing assembly is installed between the rotating wheel body and the fixed left and right support seats to maintain the support shaft Sealed with lubricating oil in shaft sleeve and other parts. The sealing assembly is composed of a pair of double-cone metal material sealing rings and two nitrile rubber fixed compression rings. The rubber ring is installed in the sealing seat of the wheel body and the support seat respectively. Since the metal seal ring bears the squeeze of the rubber ring to ensure that its annular blade belt is tightly engaged during rotation, the seal is a floating seal type.
In 1995, our factory produced supporting wheels for a company's excavator. The company provided foreign production drawings, and the floating oil seal components were imported from abroad. During the installation test, it was found that some of the rollers leaked oil at the floating oil seal. After many inspections, analyses and tests, it was finally found that the tapered angle of the company's floating seal assembly and its seat ring mouth was significantly smaller than that produced by our factory. The angle of other types of oil seals; through drawing calculations, the compression of the rubber ring is too large.
We believe that the tapered angle of the floating oil seal is small, which reduces the jump of the floating seal ring engagement ring caused by the external impact of the roller, improves the axial force of the seal engagement surface and keeps its axial force independent of the system shaft. It is beneficial to make the gap larger and change sharply. However, the sealing cone angle becomes smaller, it is easy to cause the rubber ring to skew on the cone surface when the roller is assembled, and the compression amount of the sealing seat on the rubber ring is increased, it is more difficult to ensure the correct position of the sealing engagement blade in the assembly. Analysis of the relevant data of some advanced companies in the world shows that the oblique angle of the cone surface of the floating oil seal becomes smaller, which is a development trend in design.
Based on the above analysis, we have taken two measures:
(l) The parameters of the originally designed floating oil seal sealing ring, such as the taper and the taper angle of the rubber ring seat, remain unchanged, and the compression of the sealing rubber ring is appropriately changed with the simplest design changes.
( 2) Improve the assembly process and add special tools to ensure the correct position of the floating oil seal rubber ring on the sealing ring cone surface and the correct position of the sealing seat installed to ensure the correct engagement of the two sealing ring cutting edges.
After strict assembly according to the above measures, no matter whether it is a test or an installed use, no leakage is found.
We believe that in order to improve the service life of the floating seal assembly of the rollers of the construction machinery walking mechanism, foreign companies reduce the tapered angle of the sealing ring and the tapered angle of the rubber ring seat, theoretically and practically It is advantageous to see it, but if the assembly cannot be guaranteed to be accurate in place during the manufacturing process, it will go against the wish.
If the assembly of the floating seal assembly is incorrect, the factory will perform airtightness inspection at the static original position, but due to the elasticity of the rubber ring, the airtightness inspection pressure cannot reach the equivalent value when the pressure does not reach a considerable value. There will be no leakage. After a certain period of time, due to the frictional heating of various parts and the increase of the internal cavity pressure to a certain value, the rotating meshing position due to the elastic force of the rubber ring makes the blade belt at this point. The instantaneous leakage; if the rotation stops under this condition, the leakage at the meshing point is not instantaneous but serious oil leakage occurs, and continues until the pressure of the inner cavity drops to a certain value and the elasticity of the rubber ring reaches a new balance. stop.
In the wrong state of assembly, there will also be local blade surfaces during operation due to increased friction and wear due to pressure ambassadors, and at the same time, heat is rapidly generated, resulting in reduced viscosity of the lubricating oil and increased wear of each rotating pair.
The above analysis shows that, in addition to advanced design and high-quality parts processing and production, a high-quality component, correct and perfect assembly is very important.
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