Material or article handling – Cylindrical bar handling device – Heat exchanger tube bundle handling device
Reexamination Certificate
2001-05-25
2004-05-04
Krizek, Janice L. (Department: 3652)
Material or article handling
Cylindrical bar handling device
Heat exchanger tube bundle handling device
C414S495000, C414S497000, C414S498000, C414S541000
Reexamination Certificate
active
06729833
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a lifting and moving device. More particularly, the present invention relates to an apparatus and a method for removing and installing horizontally disposed heat exchanger bundles.
Heat exchangers are used in chemical processing plants, such as petroleum refineries and distilling facilities for absorbing heat created by high temperature reactions. These heat exchangers utilize long metal tubes arranged in a cylindrical bundle. The bundle is generally heavy and may vary in diameter and length. For example, often these bundles may average one to six feet in diameter, twelve to twenty-four feet long and may have a weight of two to forty tons. Further, the preceding diameter, length, and weight may be exceeded.
An individual bundle is typically inserted into a horizontally disposed shell and coupled to an inlet and an outlet in the heat exchanger system which typically has multiple bundles. To facilitate heat exchange, fluid enters into a bundle from its inlet in the heat exchanger thereby flowing through the individual tubes of the bundle and exits via the outlet. Heat exchanger fluid flows through the shell, past the outside of the tubes and the tube and shell fluids may travel through a series of horizontally stacked bundles before being collected for reuse or recycling. During use, the individual tubes of the bundle are subject to fouling and corrosion and also have a limited life. Thus, each bundle in the heat exchanger requires regular maintenance of the individual tubes of the bundle and eventual replacement thereof.
The physical size and weight of the bundles create significant obstacles for maintenance and replacement. For maintenance, the bundle must be removed from its shell by a bundle extractor and often transported to another on-site location or an off-site facility more suited to the work required. A large heat exchanger may have multiple bundles arranged in stacks, one above the other. Thus, the lowest bundle may be contained in a shell a few feet off of the ground while the highest may be over thirty feet above the ground.
Another obstacle is the need to support and balance the bundle as the bundle is pulled from its shell. This problem is compounded by the fact that these bundles vary in length. Thus, a method and apparatus are needed for removing these heat exchanger bundles at a wide variety of heights from ground level while keeping the bundles securely supported as they are pulled from their shells.
A heat exchanger bundle is typically removed from its shell by a pulling car or sled of the extractor that exerts a pulling force on a tube sheet which is fixed to the ends of the tube bundle. Significant force is often required to break the bundle free from its shell due to normal product corrosion between the bundle and tube sheet and the shell. A pulling mechanism such as a winch, hydraulic jack, or screw drive and motors are typically used with the extractor pulling sled to break the bundle free. Once free, the bundle is positioned on a sliding carriage mounted on a frame of the extractor such that the bundle carriage is moved along the frame as the bundle is pulled from its shell. Due to the weight and length of the bundle, the carriage and frame may be tilted to balance the bundle as the bundle is removed.
Different types of equipment have been used to support the carriage and frame of the extractors in their operative position for pulling of heat exchanger tubes bundles. U.S. Pat. Nos. 3,836,015 and 4,053,062 to Travis and U.S. Pat. Nos. 4,869,638 and 5,032,054 to Krajicek et al. disclose an aerial supported carriage and frame for being lifted by a crane and which may be moved off site using the crane or a helicopter. Another approach is mounting the frame to a telescoping column on a truck bed as disclosed in U.S. Pat. No. 4,575,305 to Krajicek et al. and U.S. Pat. No. 5,403,145 to Cradeur et al. Another extractor disclosed in U.S. Pat. No. 5,383,271 to Amuny uses four telescoping cylinders to support and lift the frame. U.S. Pat. No. 5,562,400 to Travis and U.S. Pat. No. 5,564,179 to Amuny disclose extractors that utilize wheels and drive means to provide a self-propelled bundle extractor and have outrigger lifting columns which raise the frame to the height of the bundle shell.
Extractors which require the use of cranes to position the frame at the shell of the heat exchanger bundle are not practical for use in areas with limited clearance between the heat exchanger unit and other structures. Similarly, extractors mounted on truck beds present the same space concerns. In these limited clearance areas, there may not be adequate space to position a crane or truck between the structures. Thus, a mobile extractor that is self-propelled and has a self-contained mechanism for raising and lowering its extractor frame is usually preferred due to the limited clearances between structures.
U.S. Pat. Nos. 5,562,400 and 5,564,179 disclose self-propelled extractors a support frame and carriage that are mounted on wheels with hydraulic cylinders or telescoping lifting columns. The extractor of the latter patent utilizes the lifting columns to raise both the support frame and carriage to the vertical position of the heat exchanger shell; whereas, U.S. Pat. No. 5,562,400 uses the lifting columns to raise only a carriage frame having a pulling sled and skids. Due to the extreme weight of the heat exchanger bundle, which can exceed forty tons, the use of rubber wheels is not practical because they cannot support the weight. Therefore, steel wheels with polyurethane shells are used.
One problem with self-propelled extractors of this type is that the heat exchanger units are typically located outside on asphalt or gravel surfaces which may become soft due to rain or sun exposure such that the steel wheels often dig into the surface as the extractor is moved across the surface or when turning. After the bundle is pulled onto the extractor, the added weight often embeds the wheels into the surface making it impossible for the extractor to move under its own power. As an alternative, a self-propelled extractor may provide for lifting the extractor with a crane such as that disclosed in U.S. Pat. No. 5,564,179. Due to the weight of the extractor and bundle, which may be over sixty-five tons, a large crane is required. Under some union rules, the operation of a large crane requires two workers, an operator and an oiler. However, for the operation of smaller cranes, only one worker is required, the operator. To support two shifts of extractor operations, the added oiler increases the labor costs approximately $6,000 to $8,000 per shift per week.
Another problem with known extractors is that the telescoping columns which lift the support frame and carriage of the extractor to the height of the shell become very unstable when the support frame is near or at the top of its vertical travel due to the progressive upwardly shifting of the extractor's center of gravity. The four telescoping columns usually have to support the entire weight of the support frame carriage and eventually the bundle, e.g. see U.S. Pat. No. 5,564,179. Furthermore, as the bundle is being pulled onto the carriage, the added weight of the bundle to the front of the extractor adjacent the shell shifts the center of mass of the extractor, rendering it unstable. Likewise, as the bundle is being pulled from the shell and onto the carriage, the changing position of its center of mass may tilt the extractor frame such that one of the front or the rear columns may support more weight than the others, which may cause the extractor to tilt or rock. Thus, added precautions must be taken to prevent or compensate for the sudden shifts in weight to prevent the extractor from overturning.
Accordingly, a method and apparatus are needed that provide a heat exchanger bundle extractor apparatus that remains stable when removing or installing heat exchanger bundles at high levels above ground surface. Further, a method and apparatus which can fit into tight spaces
Cichon David E.
Uremovich Michael J.
Wilson Jeffrey L.
Fulbright & Jaworski LLP
Krizek Janice L.
Starcon International, Inc.
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