subject: Labyrinth cartridge seal, and centrifugal compressor applications [print this page] Labyrinth cartridge seal having a shell and a plurality of sleeves having corresponding portions to prevent axial and radial movement therebetween and particularly a labyrinth cartridge seal for use in a compressor for compression of a gas, such as oxygen, which restricts leakage of pressurized gas to a drive mechanism such as an oil lubricated gear box, to thereby reduce the likelihood of explosions.
In one embodiment, the labyrinth cartridge seal includes a shell comprising a passageway therethrough, and four spaced-apart, concentrically aligned sleeves, axially and radially supportable along the passageway and generally sealable with the shell to define three separate chambers around the shaft. The shell has three ports, each one opening onto a different one of the three separate chambers for venting or receiving a supply of buffering gas. Also disclosed is a compressor incorporating such a labyrinth cartridge seal.
In an integrally geared centrifugal compressor, pressurized gas tends to leak axially along the rotating shaft of the compressor and into the driving mechanism such as an oil lubricated gear box. Cartridge seals provide safe operation of the compressor by properly sealing, venting, or buffering the pressurized gas from the oil lubricated gear box. In compressors for compressing gas such as oxygen, oil used for lubricating the gear box must be isolated from the oxygen to prevent fires.
The illustrated prior art cartridge seal 10 while suitable for its intended purpose includes a number of drawbacks. The fabrication of cartridge seal 10 is labor and time intensive due to the required drilling and deburring of the ports. In addition, increasing the number of ports to increase the flow areas between the shaft of the compressor and sleeve for venting or providing a buffering gas reduces the strength of the sleeve and/or shell.
Therefore, there is a need for labyrinth cartridge seals comprising a shell and a plurality of sleeves using a minimum amount of sealing material and having corresponding portions to prevent axial and radial movement therebetween, which reduce the labor, time, material, and/or cost required for fabrication, and which provide increased areas for venting or receiving a buffering gas to isolate a gas being compressed from the drive mechanism of the compressor.
Pursuant to the present invention, the shortcomings of the prior art are overcome and additional advantages provided by a labyrinth cartridge seal having a shell and a plurality of sleeves having corresponding portions to prevent axial and radial movement therebetween. The sleeves can be fabricated from various materials suitable to sealing a variety of gases while minimizing the amount of material used. Such a labyrinth cartridge seal is particularly suitable for use in an oxygen compressor which requires costly seal materials in order to restrict the leakage of the pressurized oxygen to a drive mechanism, such as an oil lubricated gear box, to thereby reduce the likelihood of fires.
In one embodiment of the present invention, a labyrinth cartridge seal includes a shell having a passageway through the shell and a least one port opening onto said passageway, and at least two sleeves each of which has an inner surface along which a shaft of a compressor can be positioned. Each of the sleeves and the shell have corresponding portions which complementarily engage each other to radially, and axially support the sleeves in fixed, spaced-apart positions along the passageway to define a chamber around the shaft with the port opening into said chamber. Increased flow areas between the sleeves can be made by cutting annular grooves in the shell to increase the size of chambers 42, 44, and 46.
The shell may include at least two, spaced-apart, inwardly extending annular portions which define a portion of the passageway. The sleeves may each include at least two outwardly extending spaced-apart, annular-shaped portions between which one of the inwardly extending annular-shaped portions of the shell is received. Desirably, the shell comprises a first half and a releasably attachable second half, and the sleeves comprise unitary sleeves.
In another embodiment of the present invention, a labyrinth cartridge seal includes a shell comprising a passageway therethrough, and four spaced-apart, concentrically aligned sleeves, axially and radially supportable along the passageway and generally sealable with the shell to define three separate chambers around the shaft. The shell has three ports, each one opening into a different one of the three separate chambers.
Another embodiment of the present invention relates to a compressor for pressurizing a gas, in which the compressor comprises a shaft, a drive mechanism attached to a first end portion of the shaft for rotating the shaft, an impeller attached to a second end portion of the shaft for pressurizing the gas, and a casing for supporting the shaft and the drive mechanism. A labyrinth cartridge seal as described above is disposed between the shaft and the casing for restricting the flow of pressurized gas along the shaft toward the drive mechanism.
The present invention is described in detail with reference to use in a compressor, it will be appreciated by those skilled in the art that the labyrinth cartridge seal may be effectively utilized in turbines and/or in devices for compressing gases other than oxygen, e.g., for limiting contamination of pressurized gas with oil. In addition, the labyrinth cartridge seal may be used in compressors having one or more compression stages, e.g., compressors having a first impeller attached to one ends of a rotatable shaft and a second impeller attached to the other end of the rotatable shaft.
Labyrinth cartridge seal, and centrifugal compressor applications
