Mechanical seal with barrier fluid circulation system

An improved mechanical seal is provided, wherein an annular inner flange extending

from a gland plate having inlet and outlet openings is provided with a series of notches between the inlet and the outlet openings, the notches running in the direction of rotation of the shaft around which the seal is attached. The annular inner flange extends inwardly toward and close to the shaft. A series of axial notches made in the rotary sleeve of the seal, extending beneath the stationary seal assembly further increases pumping efficiency, and may be used to circulate barrier fluid without the notches in the flange. A recess in the flange at the outlet opening may used to further increase circulation efficiency.

Mechanical seals are used to provide a seal between various components on a rotating shaft. Such seals take many different forms. In the field of cartridge mounted seals are mechanical seals which have at least one set of contacting seal faces, one rotary face and one stationary face, the rotary face being driven by its connection to a sleeve which is mounted nonrotatably to the shaft. The entire cartridge seal unit is installed by simply sliding the sleeve and the attached seal components onto the shaft and fixing the sleeve in place (usually with set screws). A gland plate is provided for supporting the stationary seal face. The gland plate is usually bolted to the housing (such as a pump housing) through which the shaft extends. If two sets of seal faces are provided on either side of the gland plate, the seal is known as a double or tandem seal.

In double or tandem seals, and in some specialized applications of single cartridge mounted seals, a barrier fluid is circulated through the seal during operation. Barrier fluid, such as a water-ethylene glycol mix, enters and exits through the gland plate. The fluid circulating within the seal provides lubrication for the sealing faces as well as coolant for the seal. The barrier fluid also can help absorb vapor leakage of process fluids, protecting the environment. In a double seal the pressure is greater in the seal than in the process stream. In a tandem seal the pressure of the process stream is greater than in the seal. Various devices have been designed to utilize the rotation of the shaft to induce a pumping action from within the seal to circulate the barrier fluid. In some mechanical seals an impeller has been added to the interior design of the seal for circulation of barrier fluid. The addition of an impeller is not possible in many cartridge designs as it results in too much bulk in the seal, increasing the overall size of the seal and prohibiting installation of the device in many applications requiring very small seal components.

Both of the patented devices described above have also exhibited a limited ability to adequately circulate the barrier fluid. There is an increased concern by those in the mechanical seal industry in circulating barrier fluid at a greater flow rate to all internal seal components, thus making the seals function more efficiently and for a longer period of time.

Accordingly, it is an object of this invention to provide a mechanical seal with a barrier fluid circulation system which utilizes the dynamics of the rotating shaft to circulate barrier fluid at a greater flow rate.

It is another object of this invention to provide a mechanical seal with a barrier fluid circulation system which more efficiently circulates barrier fluid within the seal.

It is still another object of this invention to provide a mechanical seal with a barrier fluid circulation system which accomplishes some or all of the above objectives and does not increase overall seal size.

Therefore, an improved mechanical seal is provided, wherein an annular inner flange extending from a gland having inlet and outlet openings is provided with a series of notches between the inlet and the outlet openings, the notches running in the direction of rotation of the shaft around which the seal is attached. The annular inner flange extends inwardly toward and close to the shaft. A series of axial notches made in the rotary sleeve of the seal, extending beneath the stationary seal assembly further increases pumping efficiency, and may be used to circulate barrier fluid without the notches in the flange. A recess in the flange at the outlet opening may used to further increase circulation efficiency.

It is a further object of this invention to provide a mechanical seal with a barrier fluid circulation system which accomplishes some or all the above objectives while maintaining an annular inner flange on the gland on which seal components can be mounted.

Mechanical seal with barrier fluid circulation system

By: Oliver

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