Three sealing problems of metal bellows and solutions

Metal bellows are multi-functional thin-walled housing components with horizontal undulation and flexibility. Due to the action of external forces and torque, it will produce a combination of axial, angular and horizontal displacement.

Softness and sealing properties.

It has been widely used in machinery, aerospace, petrochemical, electric power, automobile, shipbuilding, nuclear industry and other industries.

In a metal bellows valve, the process fluid between the valve shaft and the body can be moved axially, creating a dynamic seal.

Due to the movement of the valve stem, the metal bellows are compressed and stretched, and the valve stem is sealed in the use of the valve to achieve zero leakage, thus ensuring the loss of pipeline media, preventing the leakage of flammable, explosive and harmful media, and ensuring the stability of the environment and personnel.

The life of metal bellows under moving conditions refers to the short movement cycle or cycle time that can ensure normal movement.

To return the bellows from full open to full closed, and then use the stem full open motion process.

The main factors affecting the life of bellows are bellows structure, geometric parameters, pressure, stroke (displacement). Temperature, material, manufacturing process, working medium, etc.

The use of bellows mechanical seal is investigated, and the failure seal is analyzed from the aspects of structural design, material and help system configuration.

The end face of the sealed friction pair is seriously worn.

Due to the high viscosity and poor fluidity of the residual oil, the residual oil medium contains granular and powdered coke, and coke will inevitably appear around the friction pair, which is very harmful to the friction pair.

When the coke enters the seal end face, the high-speed rotation of the friction pair will tighten the seal end face and cause damage.

When the polymer and impurity particles enter the end face of the friction pair, the sealing surface will wear and eventually lead to the failure of the seal leak.

Bellows assembly loses elasticity.

In practical use, a large amount of compression is usually used to contact the seal of the bellows to achieve the sealing function under high temperature and high pressure. Therefore, the specific pressure of the end face of the seal is greatly increased, the end face of the friction pair is seriously worn, and a lot of friction heat is generated.

If the friction heat cannot be taken away immediately, at a long high temperature, the stiffness and elasticity of the bellows will gradually decline or disappear, that is, the elasticity is lost.

The higher the temperature, the greater the load and the faster the elastic loss.

If the bellows lose elasticity, the seal face is immediately opened at medium pressure, resulting in a large amount of leakage.

Washing oil and cooling water consumption is very large.

In order to stop the temperature rise and burning of the seal, external cleaning and cooling measures must be taken to reduce the increase in friction temperature and stop the poor seal caused by burning, heat cracking and aging.

Therefore, a large amount of cleaning oil and cooling water must be consumed, and the operation cost is high.

Now, some Chinese manufacturers also use first and second layers of tetrafluoroethylene rings outside the rubber O-ring.

This structure not only solves the problem of poor elasticity of tetrafluoroethylene seals, but also solves the problem of deformation and deterioration of rubber seals.

This paper analyzes the characteristics of spring type mechanical seal and metal bellows mechanical seal, and the test conditions of compressor metal bellows mechanical seal.

It is recommended to popularize metal bellows mechanical seals in the refrigeration industry.

In the refrigeration industry, the wide application of metal bellows mechanical seals not only has practical significance, but also has long-term economic benefits.

Metal bellows mechanical seal is a new technology in our country.

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