Performance and Precautions of Metal Bellows Mechanical Seals

The design of welded metal bellows mechanical seals is generally balanced, so its ability to withstand pressure on the end face compared to the influence of specific pressure is small. Welded metal bellows mechanical seals are not only suitable for non-hydrocarbon media, but also for flashing hydrocarbon media. Its service life is greatly improved compared to ordinary mechanical seals, so it has a higher performance-to-price ratio.

Performance characteristics of metal bellows mechanical seals

Bellows are sealing elements that integrate elastic elements, auxiliary seals, and torque transmission mechanisms (ordinary seals do not have this kinetic energy), and the way of torque transfer is unique to bellows mechanical seals. The specific pressure on the end face is uniform, and it has the characteristics of high temperature resistance and good followability. The dynamic rings do not have auxiliary sealing rings, thereby reducing a leaking point and reducing the friction resistance of the dynamic ring, which improves the followability of the dynamic ring. There are two commonly used bellows: pressurized and welded. Pressurized bellows are produced by elongating and forming thin-walled tubes by pressure machines or hydraulic molds. Welded bellows are made by welding thin film sheets inside and outside (more commonly used). Compared with pressurized bellows, welded metal bellows mechanical seals have the following advantages:

  • Due to the large radial stiffness of the bellows and the variety of manufacturing materials, welded bellows have a wider range of applications for pressure and temperature.

  • Welded bellows can be used as springs with precise working characteristics.

  • The torsional rigidity is relatively large.

  • The fatigue limit is long.

  • The size is compact.

Precautions for using metal bellows mechanical seals

The metal bellows mechanical seal has a wide range of applications, from low temperature to high temperature, from neutral media to corrosive media, from low speed to high speed, and from common to harsh working conditions. Bellows include rubber bellows and serpentine sleeves, plastic bellows, and metal bellows. Rubber bellows and serpentine sleeves are used as auxiliary seals for low-load mechanical seals; plastic bellows are used as auxiliary seals for strong corrosive medium mechanical seals; and metal bellows are used for high temperature, high pressure, and low temperature medium mechanical seals, as both auxiliary seals and elastic components.

Metal bellows mechanical seals should have a large elasticity, strength, and rigidity, and can be used in occasions with pressures up to 7 MPa, applicable to both high and low temperature operations, withstanding temperatures ranging from -240°C to +650°C, and the thickness of the film is not greater than (< 0.4 mm), which requires that the bellows material has high corrosion resistance and can be used in neutral media.

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