Patent Application
20130146695
1. Field of the Invention
The present invention relates to journal assemblies, such as in pulverizers, and more particularly to seals for protecting journal bearings.
2. Description of Related Art
A variety of devices and methods are known in the art for reducing particulate size of raw materials. Of such devices, many are directed to pulverizing coal for use as a fuel. In coal-fired furnaces, for purposes of improved and more efficient ignition, it is preferred to pulverize the coal to a fine powder before introducing it into the furnace for combustion.
In operations that use coal for fuel, finely-ground coal particles or “fines” are desirable for efficient operation, yielding higher combustion efficiency than stoker firing, as well as rapid response to load changes. Using coal fines for combustion also produces less nitrous oxide (NOX) emissions and keeps oversized loss-on-ignition (LOI) unburned coal particles from contaminating the marketable ash byproduct of the combustion chamber. Thus, it is common practice to supply raw coal to a device, such as a pulverizer, that will reduce the size of the coal to particles within a desirable range prior to being used for combustion.
Coal pulverization involves systematically comminuting coal to a desired size, e.g., a fine powder, prior to introduction into a coal-fired furnace. Conventional coal pulverization systems include ball tube type mills, high-speed attrition type pulverizers, and vertical roller type mills.
Traditional bowl mill pulverizers are shown and described in U.S. Pat. No. 3,465,971 to Dalenberg, et al., and U.S. Pat. No. 4,002,299 to Skalka, which describe the construction and operation bowl mills suitable for use in coal fired power generation systems. As taught by the patents above, a typical bowl mill includes a body portion in which a grinding table is mounted for rotation, a plurality of grinding rollers that roll against the grinding table to grind coal therebetween, coal supply means for feeding raw coal to the interior of the bowl mill, and air supply means for supplying an air flow to the interior of the bowl mill, which entrains airborne pulverized coal particles for combustion.
In such a bowl mill, the coal enters the bowl mill and is pulverized between the grinding rollers and the grinding table. After being pulverized, the coal particles are thrown outwardly by centrifugal force whereby the particles are fed into a stream of air that is entering the bowl mill. The stream of air, which now contains pulverized coal particles, flows through a tortuous path that is established in part by the positioning of a suitably supported deflector means within the bowl mill. As the stream of air and coal particles flows along the aforementioned tortuous path, the sharp turns effect the separation of the coarse coal particles from the air stream. These coarse coal particles are then returned to the grinding table for further pulverization, while the fine coal particles are carried out of the bowl mill in the air stream. The capacity of each bowl mill of the type described above can be on the order of 100 tons per hour of coal. As the industry has pressed for greater and greater capacity, the size of typical bowl mills has increased in an effort to meet the demand.
With increased size have come issues related to stress and wear. More specifically, prolonged operation of conventional bowl mills can only last as long as the service life of the weakest components. The pulverizer journal systems typically employed in conventional bowl mills have suffered from coal infiltrating the bearings in the journal assembly and causing damage to said bearings that reduce their operational life.
The result of this phenomenon is that the bearings often require replacement earlier than the other major components of a typical journal assembly. In order to replace the journal bearings, downtime is required. Thus it is often the case that downtime is incurred due to the bearings per se. The more frequently the need arises to replace the journal bearings, the more the resulting downtime adds up in the long run. Thus, there is a significant need for improvements in the service life of bearing support for journals on which pulverizer rolls are mounted.
Due to this phenomenon, there is still a need in the art for journal assemblies that allow for improved sealing and protection of bearings in order to prevent unwanted media from infiltrating the journal assembly and damaging the internal components. There also remains a need in the art for such journal assemblies that are easy to make and use. The present invention provides a solution for these problems.
The subject invention is directed to a new and useful brush seal assembly for sealing a journal assembly. The brush seal assembly includes a base flange configured and adapted to be mounted to a journal head, e.g., in a vertical pulverizer. A cylindrical skirt is mounted to the base flange and extends in an axial direction from the base flange. A seal mounting ring is mounted to the skirt opposite the base flange, and an annular brush seal is mounted to the seal mounting ring. The brush seal is configured and adapted to seal between the skirt and a journal housing.
In certain embodiments, the seal mounting ring is a first clamping ring, and the brush seal is removably mounted between the first clamping ring and a second clamping ring. The first clamping ring can be mounted to an inward surface of the skirt. The second clamping ring can be removably mounted, e.g., bolted, to the skirt for clamping the brush seal between the first and second clamping rings.
In accordance with certain embodiments, the base flange includes an annular flange ring welded to an outside surface of a cylindrical flange skirt. The base flange and first clamping ring can be welded to the skirt, i.e., fabricated, however it is also contemplated that the base flange and first clamping ring can be formed integrally with the skirt.
The invention also provides a journal assembly. The journal assembly includes a journal shaft mounted to a journal head and defining a longitudinal axis. The journal head is configured and adapted to be mounted in a pulverizer. The journal assembly also includes a journal housing mounted for rotational movement relative to the journal shaft. A brush seal assembly as described above is included, wherein the base flange is mounted to the journal head, and wherein the brush seal seals between the skirt and the journal housing.
In certain embodiments, the journal housing includes an upper journal housing mounted for rotational movement relative to the journal shaft, and a lower journal housing mounted for rotational movement relative to the journal shaft. The lower journal housing is mounted to the upper journal housing for common rotation about the journal shaft. The brush seal can seal between the skirt and the upper journal housing. It is contemplated that each of the first and second clamping rings as described above can form a secondary seal with the journal housing. Bristles of the brush seal can be located axially between the first and second clamping rings.
The invention also includes a method of retrofitting a journal assembly. The method includes removing an upper journal head skirt from a journal head and replacing the upper journal head skirt by mounting a brush seal assembly as described above to the journal head. Replacing the upper journal head skirt includes forming a seal with the brush seal between the skirt and a journal housing mounted for rotational movement relative to the journal head.
In certain embodiments of the method, the seal mounting ring is a first clamping ring, and replacing the upper journal head skirt includes removably mounting the brush seal between the first clamping ring and a second clamping ring. Removably mounting the brush seal can include removably mounting, e.g., bolting, the second clamping ring to the skirt for clamping the brush seal between the first and second clamping rings.
These and other features of the systems and methods of the subject invention will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings.
So that those skilled in the art to which the subject invention appertains will readily understand how to make and use the devices and methods of the subject invention without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein:
Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject invention. For purposes of explanation and illustration, and not limitation, a partial view of an exemplary embodiment of a journal assembly in accordance with the invention is shown in
Referring first to
Referring now to
With reference now to
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With reference now to
With continued reference to
Each of the first and second clamping rings 110 and 124 forms a secondary seal with the journal housing. In particular, there is a small air gap between each of the clamping rings 110 and 124 and upper journal housing 114. Bristles of the brush seal 112 are located axially between the first and second clamping rings 110 and 124. Since the bristles directly contact the outer surface of upper journal housing 114, they form a physical barrier, i.e., solid rather than gaseous, in addition to the air flowing through the adjacent air gaps. The bristles provide solid material that serves to deflect incoming particles, thereby sealing the space inside skirt 108 against incoming particles. Since the bristles are not air tight, they also allow for the pressurized air described above to pass through from inside skirt 108 through the air gaps of rings 110 and 124 for additional protection against ingress of pulverized particles.
Referring now to
Those skilled in the art will readily appreciate that any suitable materials can be used without departing from the scope of the invention. For example, the bristles of the brush seal 112 can be made of 304 stainless steel or any other suitable material. As another example, the brush seal assembly components can be made of AR 400 or any other suitable material.
The invention also includes a method of retrofitting a journal assembly. For example, the method can be used to convert a traditional journal assembly as in
The exemplary embodiments described above include a single continuous skirt that surrounds the journal housing through a full 360° circumferentially. However, those skilled in the art will readily appreciate that this is exemplary only, and that any other suitable configuration can be used. For example, the skirt can be designed and manufactured in two (or more) pieces that each surround the journal housing through 180° or less, which pieces could be assembled into place without the need to remove the journal head.
While shown and described above in the exemplary context of joining methods such as welding and bolting, those skilled in the art will readily appreciate that any other suitable joining techniques can be used. Additionally, while casting has been provided as an example for forming integral pieces, those skilled in the art will readily appreciate that any other suitable forming techniques can be used without departing from the scope of the invention.
The methods and systems of the present invention, as described above and shown in the drawings, provide for journal assemblies with superior properties including improved sealing for extended life of journal bearings. While the apparatus and methods of the subject invention have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the spirit and scope of the subject invention.
This application claims priority to U.S. 61/568,436 filed Dec. 8, 2011 which is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61568436 | Dec 2011 | US |
