GB2028195A

GB2028195A - Method and apparatus for removing a tube from a hole in a plate

Info

Publication number: GB2028195A
Application number: GB7929302A
Authority: GB
Original assignee: MAN Maschinenfabrik Augsburg Nuernberg AG
Current assignee: MAN AG
Priority date: 1978-08-23
Filing date: 1979-08-22
Publication date: 1980-03-05
Also published as: CS207736B2; JPS5531299A; DD146014A1; GB2028195B; ZA794443B; IT1122729B; DE2836791A1; FR2434004B3; NL7906311A; IT7924983A0; SE7907023L; FR2434004A1

Abstract

A method of removing a tube from a hole in a plate comprising cutting the inner surface of the tube helically to an adequate depth to form a shear line, separating an initial portion of the tube from the wall by ripping along the shear line, pulling the initial portion out of the hole and securing it to rotatable winding means (4), and rotating the winding means whereby the tube is ripped along the shear line, removed from the wall of the hole, and wound on the winding means (4). Fig. 1 shows a tap for making the helical cut. <IMAGE>

Description

SPECIFICATION Method and apparatus for removing a tube from a hole in a plate The present invention relates to a method and apparatus for removing a tube from a hole in a plate, e.g. of a heat exchanger.

The tubes of heat exchangers can suffer damage for instance, from vibrations. This necessitates the removal of defective tubes from the tube plates and replacement by sound tubes.

In the case of tube plates of great thickness, e.g. with thicknesses of 1 00 mm or more, the removal of defective tubes expanded into the tube plates presents difficulties because, on the one hand, commerical tube extractors designed for the removal of tubes from relatively thin tube plates are not suitable, and, on the other hand, drilling of the expanded tube ends carries a high risk because even a slight runout of the drill would be liable to render the tube plates unfit for use.

An object of the present invention is to provide a method and apparatus for removing a tube from relatively thick tube plates without difficulty.

The invention provides a method of removing a tube from a hole in a plate comprising cutting the inner surface of the tube spirally or helically to an adequate depth to form a shear line, separating an initial portion of the tube from the wall by ripping along the shear line, pulling the initial portion out of the hole and securing it to rotatable winding means, and rotating the winding means whereby the tube is ripped along the shear line, removed from the wall of the hole, and wound on the winding means.

The invention further provides apparatus for carrying out the method described above and comprising a cutting tool with a spindle formed with cutting teeth for cutting a shear line in the tube, and a guiding pilot, means for separating an initial portion of the tube from the wall, and rotatable winding means having means for clamping the initial portion thereto, for ripping the tube along the shear line and winding the ripped tube.

The invention will now be described with reference to an embodiment shown schematically in the accompanying drawing, in which Figure 1 is a plan view of a cutting tool; Figure 2is a section along the line ll-ll in Fig. 1 and Figure 3 is a longitudinal section through a rotatable mandrel with a clamping device.

In the drawing a cutting tool 1 is formed as a threading tap with cutting teeth 2 and a long guiding pilot 3 at the tip of the cutting spindle. Thanks to the long pilot, skewing of the cutting spindle is avoided. The height h of the cutting teeth 2 is less by a preset amount than the wall thickness of the tube to be removed from the tube plates. The height of the cutting teeth is selected so that the cutting depth of the helix is such that the cut produced functions as a shear line. As a rule, a tube wall thickness of a few tenths of a millimeter is chosen which is left untouched by the cut. An axially-locatable ring 7 is arranged on the shaft of the cutting tool 1 which extends outwards from the tube end.

The ring 7 is adjusted according to the thickness of the tube plate so as to ensure that the tube (tube end) is cut over the correct length.

The starting piece of the tube end so cut is separated, for instance, by means of a chisel from the wall of the hole and pulled out of the hole somewhat, and this will at the same time cause the shear line to be separated in this region. This narrow initial strip is then clamped onto a rotatable mandrel 4, rod or similar device by means of a ring 5 which is slid on and clamped to the mandrel.

By turning the mandrel 4 about its longitudinal axis, removal of the tube end from the wall of the hole is effected in the form of a narrow strip with the shear line being ripped, and the narrow tube strip so separated is wound on the mandrel.

When the two tube ends have been peeled off the wall of the hole in the form of strips in the region of the tube plates, the defective tube can be readily withdrawn and replaced.

The above-described method offers special advantages when applied to relatively thick tube plates. In principle, however, it can also be applied where thin tube plates exist.

The tubes to be replaced may be defective heating or cooling tubes in pressurized heaters or coolers.

1. A method of removing a tube from a hole in a plate comprising cutting the inner surface of the tube spirally or helically to an adequate depth to form a shear line, separating an initial portion of the tube from the wall by ripping along the shear line, pulling the intial portion out of the hole and securing it to rotatable winding means and rotating the winding means whereby the tube is ripped along the shear line, removed from the wall of the hole, and wound on the winding means.

2. A method of removing a tube from a hole in a plate, substantially as herein described with reference to the accompanying drawing.

3. Apparatus for carrying out the method as claimed in claim 1 or 2, and comprising a cutting tool with a spindle formed with cutting teeth for cutting a shear line in the tube, and a guiding pilot, means for separating an initial portion of the tube from the wall, and rotatable winding means, having means for clamping the initial portion thereto, for ripping the tube along the shear line and winding the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Method and apparatus for removing a tube from a hole in a plate The present invention relates to a method and apparatus for removing a tube from a hole in a plate, e.g. of a heat exchanger. The tubes of heat exchangers can suffer damage for instance, from vibrations. This necessitates the removal of defective tubes from the tube plates and replacement by sound tubes. In the case of tube plates of great thickness, e.g. with thicknesses of 1 00 mm or more, the removal of defective tubes expanded into the tube plates presents difficulties because, on the one hand, commerical tube extractors designed for the removal of tubes from relatively thin tube plates are not suitable, and, on the other hand, drilling of the expanded tube ends carries a high risk because even a slight runout of the drill would be liable to render the tube plates unfit for use. An object of the present invention is to provide a method and apparatus for removing a tube from relatively thick tube plates without difficulty. The invention provides a method of removing a tube from a hole in a plate comprising cutting the inner surface of the tube spirally or helically to an adequate depth to form a shear line, separating an initial portion of the tube from the wall by ripping along the shear line, pulling the initial portion out of the hole and securing it to rotatable winding means, and rotating the winding means whereby the tube is ripped along the shear line, removed from the wall of the hole, and wound on the winding means. The invention further provides apparatus for carrying out the method described above and comprising a cutting tool with a spindle formed with cutting teeth for cutting a shear line in the tube, and a guiding pilot, means for separating an initial portion of the tube from the wall, and rotatable winding means having means for clamping the initial portion thereto, for ripping the tube along the shear line and winding the ripped tube. The invention will now be described with reference to an embodiment shown schematically in the accompanying drawing, in which Figure 1 is a plan view of a cutting tool; Figure 2is a section along the line ll-ll in Fig. 1 and Figure 3 is a longitudinal section through a rotatable mandrel with a clamping device. In the drawing a cutting tool 1 is formed as a threading tap with cutting teeth 2 and a long guiding pilot 3 at the tip of the cutting spindle. Thanks to the long pilot, skewing of the cutting spindle is avoided. The height h of the cutting teeth 2 is less by a preset amount than the wall thickness of the tube to be removed from the tube plates. The height of the cutting teeth is selected so that the cutting depth of the helix is such that the cut produced functions as a shear line. As a rule, a tube wall thickness of a few tenths of a millimeter is chosen which is left untouched by the cut. An axially-locatable ring 7 is arranged on the shaft of the cutting tool 1 which extends outwards from the tube end. The ring 7 is adjusted according to the thickness of the tube plate so as to ensure that the tube (tube end) is cut over the correct length. The starting piece of the tube end so cut is separated, for instance, by means of a chisel from the wall of the hole and pulled out of the hole somewhat, and this will at the same time cause the shear line to be separated in this region. This narrow initial strip is then clamped onto a rotatable mandrel 4, rod or similar device by means of a ring 5 which is slid on and clamped to the mandrel. By turning the mandrel 4 about its longitudinal axis, removal of the tube end from the wall of the hole is effected in the form of a narrow strip with the shear line being ripped, and the narrow tube strip so separated is wound on the mandrel. When the two tube ends have been peeled off the wall of the hole in the form of strips in the region of the tube plates, the defective tube can be readily withdrawn and replaced. The above-described method offers special advantages when applied to relatively thick tube plates. In principle, however, it can also be applied where thin tube plates exist. The tubes to be replaced may be defective heating or cooling tubes in pressurized heaters or coolers. CLAIMS

3. Apparatus for carrying out the method as claimed in claim 1 or 2, and comprising a cutting tool with a spindle formed with cutting teeth for cutting a shear line in the tube, and a guiding pilot, means for separating an initial portion of the tube from the wall, and rotatable winding means, having means for clamping the initial portion thereto, for ripping the tube along the shear line and winding the ripped tube.

4. Apparatus for removing a tube from a hole in a plate substantially as herein described with reference to the accompanying drawings.