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What are the characteristics of bellows mechanical seals?
The compensation mechanism is a corrugated tube, in which a sealing ring (moving ring or static ring) and the corrugated tube are made as a whole, there is no auxiliary sealing ring in the middle, so a leak point is reduced; meanwhile, the friction resistance of the compensation mechanism is reduced, and the followability is improved ; For welding metal bellows, the use temperature is not limited by the auxiliary seal; for PTFE bellows seals can be used in corrosive media. The disadvantage of the bellows type mechanical seal is that some bellows have less elasticity, and auxiliary springs need to be added.
Second, what are the types of bellows mechanical seals
The bellows mechanical seal has a wide range of applications, from low temperature to high temperature, from neutral medium to corrosive medium, from low speed to high speed, and from ordinary to harsh working conditions.
All of these can change the elasticity of the bellows by changing the geometry of the bellows (such as inner and outer diameter, wave plate thickness, wave number, etc.) and the elastic modulus of the material.
According to the corrosion performance of the medium, different bellows materials are selected.
For example, for neutral media (oil and water, etc.) with low working pressure and temperature, a simple bellows mechanical seal made of rubber can be selected; in corrosive media (acid or alkali, etc.), corrugations made of tetrafluoride can be selected Tube mechanical seal; at high temperature and high speed, welded metal bellows mechanical seal can be used.
Common failures of metal bellows mechanical sealsCooking Class Story Part One
1) The bellows loses its elasticity under high temperature, and the bellows ruptures under high pressure (such as the above hot water pump).
2 Coking and carbon deposits are prone to occur at the troughs between the wave plates, which makes the bellows lose its elasticity and cannot be compensated, so it cannot be used in pumps for coking, carbon deposits and crystal precipitation.
3) Externally mounted mechanical seal. When the pressure in the sealing cavity exceeds 0.2mpa, the sealing surface can be pushed away. This is because the elasticity of the bellows is small and it cannot withstand the high medium pressure. Therefore, when the pressure is high, the mechanical seal cannot be used.
4) Since the bellows mechanical seal is a balanced structure, it is necessary to calculate the effective diameter and load factor when using it. Otherwise, the operation is unstable in high pressure propane and propylene pumps, and it is prone to "leakage".
Source: Network finishing
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