1. Field of the Invention
The present invention relates to a systems and methods for sealing trunnions, and more particularly to systems and methods for sealing trunnions of ball tube mills for pulverizing materials.
2. Background of the Related Art
Ball tube mills are used in material size reduction processes, such as grinding coal or other minerals. A typical ball tube mill includes a large, cylindrical drum that rotates along its axis, supported by a trunnion on each end. As the drum rotates, a mass of balls and coal or other material mix in the bottom of the drum, which reduces the particle size of the coal or other material. Particles that are fine enough become airborne and are vented out of the drum for use in further processes such as coal combustion. New coal or other material enters through the ends of the drum to replace the airborne particles leaving the ends of the drum.
In order to move material between the rotating drum and related stationary components such as a coal piping system, for example, the rotating drum typically connects at each end to a stationary inlet/outlet box via a trunnion seal. The trunnion seal allows passage of material between the rotating drum and the stationary inlet/outlet box while discouraging or preventing material from escaping into the surroundings. It is advantageous to form the best possible seal between stationary and rotating components, as the fine particles involved can readily escape if the seal is inadequate. When operating a ball tube mill, the trunnion seals wear down and eventually need to be replaced. This can be exacerbated by the fact that the rotating axis of the mill tends to move downward as its bearings wear with use. Replacing the trunnion seals typically requires removing the inlet/outlet box from foundation blocks under the trunnions, which results in significant downtime.
Such conventional methods and systems generally have been considered satisfactory for their intended purpose. However, there still remains a continued need in the art for a trunnion seal that has an improved service life and is easier to install and remove. The present invention provides a solution for these problems.
The subject invention is directed to a new and useful trunnion seal for a ball tube mill. The trunnion seal includes a stationary ring component configured to be mounted around an inlet/outlet passage of a ball tube mill. A flexible pad seal is joined to the stationary ring component. The pad seal includes a first annular sealing surface. A mill head extension ring is configured to be joined to a rotational mill head proximate to and substantially concentric with the stationary ring component. The mill head extension includes a second annular sealing surface sealingly engaged with the first annular sealing surface of the flexible pad seal. The first and second annular sealing surfaces form a seal to discourage passage of particles within the mill passing into the surrounding air.
In one aspect of the invention, the trunnion seal can further include a seal sleeve joined to the stationary ring component and having an outward facing seal face around the circumference thereof for engagement to an inward facing seal face of the mill head extension ring. At least one of the inward facing seal face of the mill head extension ring and the outward facing seal face of the stationary ring component can be grooved. An air seal channel can be defined between the seal sleeve, pad seal, and stationary ring component. It is contemplated that the second annular sealing surface can be generally convex, concave, flat, or any other suitable shape.
The invention also provides a trunnion seal ring for a ball tube mill. The seal ring includes an outer ring component configured to be mounted to an outer wall of a stationary inlet/outlet box of a ball tube mill. The outer ring component includes an outer filler body defined along a chord of a circle defined by the inner circumference of the outer ring component. An inner ring component includes an inner filler body defined along a chord of a circle defined by the inner circumference thereof. The inner ring component is joined to the outer ring component substantially concentrically with the inner and outer filler bodies defining a filler having a substantially triangular cross-sectional profile.
In another aspect, the inner and outer ring components are configured to be assembled into a ball tube mill by positioning the inner ring component partially into the ball tube mill so the inner ring component is substantially concentric with the ball tube mill, then inserting the outer ring component axially outside the inner ring component and into alignment therewith, and bolting the inner and outer ring components together. The inner ring component can include a circular seal sleeve configured to extend from an inward portion of the inner ring component into an interior passage of a ball tube mill.
The invention further provides a trunnion seal assembly for joining a stationary inlet/outlet box of a ball tube mill to a rotational interior of the ball tube mill. The trunnion seal assembly includes an outer ring component, an inner ring component, a flexible pad seal, and a mill head extension ring substantially as described above. The inner and outer filler bodies define a filler having a substantially triangular cross-sectional profile. The outer ring component includes an axially outward base of the triangular profile and the inner ring component includes an axially inward apex of the triangular profile.
In another aspect, the trunnion seal assembly includes a stationary ring component configured to be joined to an outer wall of the inlet/outlet box radially outward of the outer ring component. The stationary ring component can include a plurality of circumferential sections configured to be separated and joined for installation and removal around the outer ring component. In yet another aspect, the inner ring component, outer ring component, pad seal, and mill head extension ring can be configured and adapted to be installed and uninstalled between a rotational portion of a ball tube mill and a stationary inlet/outlet box leaving the inlet/outlet box in place.
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 the trunnion seal in accordance with the invention is shown in
Ball tube mills are used in material size reduction processes, such as grinding coal or other minerals.
When operating a ball tube mill, eventually the seals of trunnions 101 need to be replaced. This can involve removing inlet/outlet boxes 122 from foundation blocks 102 under trunnions 101, which results in significant downtime, as discussed above.
Trunnion bearing ball tube mills (“btm's”) employ a trunnion seal at each end that prevents fine particle dust from escaping. Originally, a split seal configuration 10 was employed, which is shown in
With continued reference to
Trunnion seal 100 includes a trunnion ring 106 having a seal sleeve 105. Trunnion ring 106 is fixed with respect to stationary ring component 112, since trunnion ring 106 and stationary ring component 112 are both fixed to outer wall 120 of inlet/outlet box 122. Seal sleeve 105 has an outward facing seal face around the circumference thereof for engagement to an inward facing seal face of mill head extension ring 118, as indicated in
An air seal channel 124 is defined between trunnion ring 106 (including seal sleeve 105), pad seal 114, and stationary ring component 112. Air seal channel 124 contains seal air which prevents or reduces pulverized coal or other materials from escaping. The annular sealing surface of mill head extension ring 118 is generally convex, as shown in
With reference now to
Inner ring component 108 is joined to outer ring component 110 substantially concentrically with inner and outer filler bodies 128/130 defining a filler 126 having a substantially triangular cross-sectional profile, as shown in
The two-part construction of trunnion ring 106 allows installation and removal thereof without the need to remove inlet/outlet box 122 from foundation block 102, as will be described in greater detail below. This is an advantage over conventional trunnion rings, for which the corresponding inlet/outlet box 122 is removed during installation and removal.
As shown in
Referring now to
Outer ring component 110 is then positioned between inlet/outlet box 122 and inner ring component 108 (from any suitable direction including vertically as shown in
Since the inlet/outlet box assembly does not have to be removed to accommodate the installation of the components of trunnion seal 100, approximately two days of maintenance labor per seal are saved during installation or replacement of trunnion seals. And where there are two seals per ball tube mill, the total savings is approximately four days of maintenance labor per mill, which means four days less of lost generation capability. These advantages result from the two-part construction of trunnion ring 106, which can be positioned laterally into place one part at a time as described above, and removed by the reverse process.
The methods and systems of the present invention, as described above and shown in the drawings, provide methods and systems with superior properties including improved service life and ease of installation and removal, leading to reduction of downtime for ball tube mills. 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 invention.
This application claims priority to U.S. Provisional Patent Application Ser. No. 60/968,784 filed Aug. 29, 2007, which is incorporated by reference herein in its entirety.
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Number | Date | Country | |
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60968784 | Aug 2007 | US |