Metal fusion bonding – Process – With supplementary mechanical joining
Reexamination Certificate
1999-05-27
2001-02-20
Ryan, Patrick (Department: 1725)
Metal fusion bonding
Process
With supplementary mechanical joining
C228S115000, C228S126000
Reexamination Certificate
active
06189768
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The apparatus and process of the present invention relates to connecting a specific heating tube to a surrounding external sleeve. More particularly, the present invention relates to an improved design method for providing a seal tight connection between an air preheater tube and an external sleeve surrounding the tube.
2. General Background of the Invention
In the design of an air preheater tube utilized in heat exchange systems, there is normally provided an APH (air preheater tube) which is positioned within an external sleeve, there being a sealing engagement between the tube and the external sleeve. In order to increase the strength of the connection between the tube and the external sleeve, yet maintain its flexibility and resistance to thermal shock, it is necessary that there be provided a specific gap of less than 0.005 inches between the tube and the external sleeve. One of the problems confronted in this particular type of a process of forming such a seal, is the fact that if the tube is expanded to seal against the inner surface of the surrounding sleeve, then there may result in a less than smooth-straight inner surface of the tube. Therefore, when heated gases carrying particles travel through the tube opening, the result may be the build up of carbon or the like material within the recesses or non-straight portions of the tube which are not conducive to efficient operation of the heat exchange system. Therefore, there is a need in the art for a system and apparatus whereby the tube and the surrounding sleeve may be formed in such a manner as to provide a less than 0.005 inch gap between the surface of the tube and the surface of the surrounding sleeve, yet while maintaining the inner surface of the tube smooth and straight so as to avoid any particle build up on the inner surface of the tube.
In a patentability search conduced on this apparatus and process, there have been cited several patents which may be pertinent to this invention, and these are being submitted herewith in the prior art statement filed.
BRIEF SUMMARY OF THE INVENTION
The apparatus and process of the present invention solves the problems in a simple and straight forward manner. What is provided is a process and apparatus that would hydraulically compress the external sleeve onto the inner APH tube, without deforming the inner surface of the APH tube during the process. The system would include a heating tube of the type having a continuous wall portion and a bore therethrough; a sleeve positionable around the heating tube, the diameter of the sleeve slightly larger than the diameter of the heating tube; a contracting assembly securably atop the end portions of the heating tube and the surrounding sleeve; an insert positionable within the bore of the tube, for defining a non-compressible member along a portion of the inner wall of the tube; a contour ring moveable along the outer surface of the sleeve for compressing the sleeve wall against the tube wall to define a sealable gap between a portion of the sleeve and a portion of the tube. In the process for securing a seal between the heating tube and the surrounding sleeve, there would be provided a heating tube of the type having a continuous wall portion and a bore therethrough; next, positioning a sleeve around the heating tube, the diameter of the sleeve slightly larger than the diameter of the heating tube; then placing a contracting assembly securably atop the end portions of the heating tube and the surrounding sleeve; providing a contour ring along the outer surface of the sleeve, the segmented contour ring carried by the contracting assembly; positioning an insert within the bore of the tube, for defining a non-deformable member along a portion of the inner wall of the tube; and then moving the contour ring along the outer wall of the sleeve to compress the sleeve wall against the tube wall at a point opposite the position of the tube insert, for forming a sealable gap between a portion of the sleeve and a portion of the tube.
Further, the contractor assembly would include a circular collar member wherein there is secured a pair of handle members for securing the assembly onto the upper portion of the sleeve to be contracted wherein there is provided a plurality of wedge shaped contour rings housed within a diverging frustrum portion which are secured to a cylindrical coupling mandrel. There is further provided two rubber toroidal o-rings to assist in maintaining the assembly shape when placing the compression assembly onto the outer sleeve. The mandrel portion includes a threaded shaft member which is utilized to pull the mandrel and contour rings as hydraulic pressure is applied via, for example, a hand pump. As pressure is increased, the shaft and mandrel are pulled towards the converging end of the frustrum housing, which attempts to pull the contour rings. Because of the shape of the contour rings, the rings are forced to rotate slightly as they are pulled, thereby applying a normal force to the sleeve which is compressed as the resulting stress exceeds the material's yield strength. The tube insert member comprises three conical wedges, a setting screw and flat washer. When tightened, the screw attempts to push the washer into the smaller diameter formed by the wedge ends, which applies an expansive force to the wedge member. By doing so, this would secure the insert into the tube inside diameter, which increases the tube rigidity during compression of the sleeve and reduces sleeve spring back thus reducing the residual gap. Prior to the assembly of the contractor being placed on the sleeve, the puller bar of the tensioner would be loosened such that the tool can be assembled on the sleeve neck to be contracted. The axial push of the stud would engage the wedge rings when contracting the sleeve member so that loosening of the puller bar would not be excessive. The wedge ring member would be released only to enable assembly of the tool on the sleeve neck so that the operation would go forward at that point.
In operation, the tube and sleeve ends would be prepared by cleaning the outer diameter of the tube and the inner diameter of the surrounding sleeve; the sleeve would be positioned around the tube. Next, the tube and sleeve ends would be flushed and aligned with one another. Pressure would be released and the hydraulic pump would be connected to the compression assembly. The tube insert would be positioned within the tube end and the setting screw tightened until the pieces firmly held the compression devices in place against the inside of the tube. The compression assembly would be placed over the sleeve and manually held in place utilizing the handles. Hydraulic pump pressure would be increased to approximately 4,000 p.s.i. and held for two minutes. Then it would be increased to 9,000 p.s.i.g. and held for two minutes and finally increased 14,000 p.s.i.g. and held for two minutes. The pressure would be slowly released, and the compression device would be detached from the tube also removing the insert. The residual gap would be checked with a feeler gauge and the recompression would be done a second time if necessary. This process would be completed for each additional tube.
Therefore, it is a principal object of the present invention to provide a process for engaging a sleeve around a heating tube, and to make the surfaces of the tube to a specified sealing gap, without affecting the smoothness or straight inner tube surface.
It is a further object of the present invention to provide an assembly which is positioned on a tube sleeve which has been set upon a tube, so that when the assembly is utilized for mating the surfaces of the tube, an insert within the tube is expanded for preventing any warping of the tube surface as the tube sleeve is compressed there against;
It is a further object of the present invention to provide a process and assembly for forming a specified gap of about 0.005 inches between the outer surface of a tube and the inner surface of a tube sl
Lewis David
Murray Wallace
Porowski Janek
Skiff Marvin
Columbian Chemicals Company
Garvey, Smith, Nehrbass & Doody LLC
Pittman Zidia T.
Ryan Patrick
LandOfFree
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