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Cartridge mechanical seal (stationary ring eccentric)-
by：Lepu Seal
2021-03-13
Cartridge mechanical seal (stationary ring eccentric)
2019-09-05
Cartridge mechanical seal (stationary ring eccentric):
Abstract: In view of the poor working conditions of the end face of the mechanical seal of the vertical top drive polymerization reactor, dry friction and boundary friction and greater end face wear, the characteristics and design basis of the eccentric mechanical seal are analyzed, and the design basis is put forward. The improved kettle uses a mechanical seal with a eccentric static ring structure.
In engineering applications, vertical top-driven polymerization reactors are rarely fully operated. The mechanical seal of this type of reactor is actually a gas medium seal. Due to the pressure in the kettle, the leakage of gaseous medium is outflow type. Even if there is lubricating oil (atmospheric pressure) in the sealed cavity area, it is very difficult for lubricating oil to enter the friction surface to form a liquid film for lubrication and sealing. Therefore, the working conditions of the end face of the seal are relatively bad, mostly in the state of dry friction and boundary friction, and the end face wear is relatively large. In order to make the liquid film between the seal end faces of this type of mechanical seal play a good lubrication and sealing effect, it is necessary to comprehensively consider the medium characteristics, pressure, temperature and slippage and expand along the crystal. Therefore, from the results of fracture analysis, metallographic inspection and material analysis, it can be considered that the cracking of the methanol condenser plate is stress corrosion cracking.
The plate fracture occurs at the bottom of the second sealing groove, where the manufacturing stress and deformation are the largest, and the working temperature is also the highest. The plates always bear tensile stress. 9 The working medium of the condenser is 99% methanol and contains CI, S plasma and a small amount of water'under the action of tensile stress' the protective film on the surface of titanium and titanium alloys will be damaged. These damages are difficult to repair by themselves, which accelerates corrosion. Due to the existence of stress, cracks are formed and rapidly grow. The hydrogen generated by corrosion is absorbed by the plate. Under the action of stress, hydrogen migrates to grain boundaries and structural defects, which weakens the grain boundaries and causes cracks to grow along the grain.
The alpha phase in the condenser plate is caused by plastic deformation during the plate pressing process. Research shows that the alpha phase of pure titanium with close-packed hexagonal lattice is generally stable. Under the condition of large deformation, due to the lattice The slip produced martensite alpha phase, which is extremely sensitive to stress corrosion, which can be
For factors such as dynamic speed, in addition to selecting proper end-face specific pressure, reasonable lubrication structure and improving the surface quality of the friction pair, it is also necessary to improve the sealing structure and adopt a structure that strengthens the lubrication conditions, such as end-face eccentricity, end-face slotting, and Hydrostatic lubrication, etc.
The sealing mechanism of eccentric structure
The mechanical seal of the vertical top drive polymerization reactor is a hydrodynamic mechanical seal. When the seal shaft rotates, the lubricating liquid produces fluid wedge dynamic pressure on the seal end face and squeezes between the end faces to form a layer of end face liquid film to provide sufficient lubrication and cooling to the seal end face
Through crystal cracking occurred. However, in a methanol solution containing a small amount of water, due to the effects of H2O and H2S, intercrystalline cracking will occur, especially when the mass fraction of hydrochloric acid in the water is within a certain range, the rate of splitting will be greatly improved.
Conclusion
The cracking of the plate of the crude methanol condenser is mainly the stress corrosion cracking caused by the working medium. The martensite phase in the structure promotes the cracking of the plate. Therefore, the plate under this working condition should not be selected from titanium or titanium alloy. To avoid equipment failure.
1115.html,
Introduction to the scheme of mechanical seal auxiliary system-scheme 13 Introduction to the scheme of mechanical seal auxiliary system-scheme 14
2019-09-05
Cartridge mechanical seal (stationary ring eccentric):
Abstract: In view of the poor working conditions of the end face of the mechanical seal of the vertical top drive polymerization reactor, dry friction and boundary friction and greater end face wear, the characteristics and design basis of the eccentric mechanical seal are analyzed, and the design basis is put forward. The improved kettle uses a mechanical seal with a eccentric static ring structure.
In engineering applications, vertical top-driven polymerization reactors are rarely fully operated. The mechanical seal of this type of reactor is actually a gas medium seal. Due to the pressure in the kettle, the leakage of gaseous medium is outflow type. Even if there is lubricating oil (atmospheric pressure) in the sealed cavity area, it is very difficult for lubricating oil to enter the friction surface to form a liquid film for lubrication and sealing. Therefore, the working conditions of the end face of the seal are relatively bad, mostly in the state of dry friction and boundary friction, and the end face wear is relatively large. In order to make the liquid film between the seal end faces of this type of mechanical seal play a good lubrication and sealing effect, it is necessary to comprehensively consider the medium characteristics, pressure, temperature and slippage and expand along the crystal. Therefore, from the results of fracture analysis, metallographic inspection and material analysis, it can be considered that the cracking of the methanol condenser plate is stress corrosion cracking.
The plate fracture occurs at the bottom of the second sealing groove, where the manufacturing stress and deformation are the largest, and the working temperature is also the highest. The plates always bear tensile stress. 9 The working medium of the condenser is 99% methanol and contains CI, S plasma and a small amount of water'under the action of tensile stress' the protective film on the surface of titanium and titanium alloys will be damaged. These damages are difficult to repair by themselves, which accelerates corrosion. Due to the existence of stress, cracks are formed and rapidly grow. The hydrogen generated by corrosion is absorbed by the plate. Under the action of stress, hydrogen migrates to grain boundaries and structural defects, which weakens the grain boundaries and causes cracks to grow along the grain.
The alpha phase in the condenser plate is caused by plastic deformation during the plate pressing process. Research shows that the alpha phase of pure titanium with close-packed hexagonal lattice is generally stable. Under the condition of large deformation, due to the lattice The slip produced martensite alpha phase, which is extremely sensitive to stress corrosion, which can be
For factors such as dynamic speed, in addition to selecting proper end-face specific pressure, reasonable lubrication structure and improving the surface quality of the friction pair, it is also necessary to improve the sealing structure and adopt a structure that strengthens the lubrication conditions, such as end-face eccentricity, end-face slotting, and Hydrostatic lubrication, etc.
The sealing mechanism of eccentric structure
The mechanical seal of the vertical top drive polymerization reactor is a hydrodynamic mechanical seal. When the seal shaft rotates, the lubricating liquid produces fluid wedge dynamic pressure on the seal end face and squeezes between the end faces to form a layer of end face liquid film to provide sufficient lubrication and cooling to the seal end face
Through crystal cracking occurred. However, in a methanol solution containing a small amount of water, due to the effects of H2O and H2S, intercrystalline cracking will occur, especially when the mass fraction of hydrochloric acid in the water is within a certain range, the rate of splitting will be greatly improved.
Conclusion
The cracking of the plate of the crude methanol condenser is mainly the stress corrosion cracking caused by the working medium. The martensite phase in the structure promotes the cracking of the plate. Therefore, the plate under this working condition should not be selected from titanium or titanium alloy. To avoid equipment failure.
1115.html,
Introduction to the scheme of mechanical seal auxiliary system-scheme 13 Introduction to the scheme of mechanical seal auxiliary system-scheme 14
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