Overview of floating ring seals and common advantages and disadvantages

Floating ring seals are abbreviated as floating ring seals and are used for shaft seals such as centrifugal compressors, hydrogen-cooled gas turbine generators, and centrifugal pumps.

　　The sealing methods available for medium and high pressure centrifugal compressors are: mechanical seal, labyrinth seal and packing seal. However, because the heat dissipation and lubrication conditions of gas are not as good as liquids, packing seals are only used at small and low speeds. Mechanical seals are difficult to adapt to when the peripheral speed is greater than 40m/s and the temperature is higher than 200°C. Only labyrinth seals and floating ring seals are used. The two most commonly used methods.

　　 Floating ring seal has the following advantages:

　　1) The sealing structure is simple, with only a few simple rings, pins, springs and other parts. The multi-layer floating ring has only a combination of these simple parts, which is less than the mechanical seal parts.

　　2) It is not sensitive to the running state of the machine, and has stable sealing performance.

　　3) The seals are not abraded, the seal is reliable, the maintenance is simple, and the repair is convenient.

　　4) Because the seal material is metal, it is solid and high temperature resistant.

　　5) Multiple floating rings can be used in parallel to form a multi-layer floating ring, which can effectively seal the high pressure above 10MPa.

　　6) It can be used for high-speed rotating fluid machinery of 10000～20000r/min, especially for gas compressors. Its allowable speed is up to 100m/s or more, which is unmatched by other seals.

　　7) As long as the floating ring is made of corrosion-resistant metal material or lined with non-metallic material (such as graphite) with corrosion resistance, it can be used for sealing strong corrosive media.

　　 8) Because there is a liquid film in the sealing gap, the friction power is extremely small, which makes the machine more efficient.

　　The shortcomings of floating ring seals: the manufacturing accuracy of the seals is high. The non-concentricity of the ring, the non-verticality of the end face and the surface roughness have a significant impact on the sealing performance. In addition, this kind of seal cannot be tightly sealed to liquids. Although the gas can be sealed tightly, a complex and expensive automatic fuel supply system is required.