JPS5935723B2 - Internal grooving tool for expanded tubes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tool for internally grooving expanded tubes.

The heat transfer section of a pressure vessel such as a boiler or heat exchanger is composed of a large number of heat transfer tubes arranged in parallel. However, it is common practice to expand the tube diameter from the inside using a so-called expand band, and then fix the outer wall of the tube in a dense layer to the hole in the tube sheet.

That is, this state is as shown in FIG. 1, and in the upper half of the figure, when the heat exchanger tubes 4 are expanded by forming adjacent holes 3 in the insertion holes 2 of the tube sheet 1, The lower half is 5
This is a case where the heat exchanger tube 4 is expanded directly into the insertion hole 2, and the end of each tube is expanded in a trumpet shape with a size of around 10 to 15 mm, and it is difficult to extract the heat exchanger tube 4 from the insertion hole 2. In the former case, it is necessary to greatly deform the piece inward by the amount of insertion into the groove 3, while in the latter case it can be pulled out more easily.

8. Here, the dimensions related to the expanded part shown in Fig. 1 are as follows: the tube diameter is 38 to 5QI771, and the thickness of the tube sheet is 30mm.
~150 years old.

Now, when such boilers, heat exchangers, etc. are used for a long period of time, the inner and outer surfaces of the heat transfer tubes may corrode, or
Alternatively, foreign matter may accumulate, resulting in a reduction in the heat exchange effect and, eventually, rupture, making it necessary to replace such heat exchanger tubes, for which the expansion band must be removed.

At this time, if the tube diameter of the heat transfer tube is about 25 mm or less, it can be pulled out by force, but if the tube diameter is about 38 to 100 mm, it cannot be removed so easily.

Particularly when the insertion hole has a groove as described above, it is difficult to remove it because a part of the thickness of the heat exchanger tube is sunk in.

Conventionally, in such cases, the thick part of the expanded band is cut in one or several places in a straight line along the axis by gas melting, and this part is crushed and deformed. I try to pull it out, but even if I try to cut a groove for the thickness of the heat exchanger tube, there is a risk that the insertion hole in the tube plate will be damaged by the gas flame, so this is not desirable. Even if the heat exchanger tube is left as is and replaced with a new heat exchanger tube and expanded again, it will be impossible to maintain airtightness from now on because the damage is a groove in the axial direction.

This invention is an attempt to improve the above-mentioned drawbacks of the conventional technology, and its purpose is to insert a chisel and a guide fitting into the thick walled part of the expanded heat transfer tube from the inside along the axis. It is an object of the present invention to provide a tool for mechanically cutting grooves using a tool.

In order to achieve this object, the present invention uses a guide jig that is fitted completely inside the end of the heat exchanger tube, and a chisel that is inserted into the guide groove of the guide jig. The grooves are cut by driving the grooves with an air hammer or the like.

Here, the groove cutting is performed so that the wall thickness of the tube end is as deep as possible, and the insertion hole is absolutely not damaged, and the groove shape is such that it has a notch effect that facilitates crushing after cutting the groove. A certain shape, such as a sharp V-shape, is ideal, and the appropriate length of the groove is about the thickness of the tube sheet.

When grooving in this way, the inner diameter of the heat exchanger tube after expansion is determined by the tolerance of the wall thickness of the heat exchanger tube (as much as 30% on the plus side with respect to the nominal dimension, for example, a thickness of 4 mm).
tm) and the tightness of the expander band causes considerable variation, and this variation becomes a play in the guide jig and affects the position of the cutting edge of the guide jig. This ultimately results in a change in the depth of the groove.

As described above, the depth of the groove cutting is as deep as possible without penetrating the pipe wall.

In other words, it is desirable to cut the pipe so that only a small amount of the wall remains, but for practical purposes, the desired thickness after cutting is 0.
, 5 or less is advantageous in order to facilitate the subsequent crushing operation.

Incidentally, the dimensions related to the expanded portion targeted by the present invention are a nominal tube diameter of 38 to 50 mm, and a tube plate thickness of approximately 30 to 150 mm.

Hereinafter, one embodiment of the method of this invention will be described in detail with reference to FIGS. 2 to 5.

In these FIGS. 2 to 5, the same reference numerals as in FIG. 1 indicate the same or corresponding parts.

FIG. 2 shows an exploded perspective view of the tool of this embodiment.

8 in FIG. 2, the reference numeral 5 represents a guide jig.

This guide jig 5 has a body part 6 that is fitted inside the tube end of the heat exchanger tube 4, and one end side of this body part 6 has a flange with an outer diameter larger than the inner diameter of the heat exchanger tube 4. Along with establishing Section 7,
A dovetail-shaped guide groove 8 is formed on the negative side of the body through which the flange 7 also passes, and a wedge surface 9 is formed on the other side.

Reference numeral 10 denotes a chisel that can be inserted into the guide groove 8 with one end side force 1, and has a cross-sectional shape that allows the cutting edge 11 to protrude by a predetermined dimension outside the circumferential surface of the body 6, and the insertion depth is limited. It has a restricting flange 12 and a head 13 that can withstand hitting.

Furthermore, 14 is a wedge that is driven into contact with the wedge surface 7.

In the case of this embodiment, as shown in FIGS. 3 and 4, the guide jig 5 is inserted completely inside the tube end of the heat exchanger tube 4, and then the guide jig 5 is inserted between the wedge surface 9 and the inner surface of the tube. By lightly driving the wedge 14 between them, it is positioned at the end of the tube and firmly fixed.

In this state, insert a chisel 1 into the guide groove 8 from the outside of the flange 1.
By inserting the tip of the cutting edge 11 of the tube and hitting its head 13 with, for example, an air hammer (not shown), the expanded thick part of the end of the tube is struck by the tip of the tube into a predetermined area. It is possible to cut over the length and process the cut groove 15 in the same thick part.

FIG. 5 shows a case where the above operation is repeated to form cut grooves 15 at equal angular intervals on the inner circumferential surface of the tube end of the heat transfer tube 4 at four locations. By striking the heat exchanger tube 4, the expanded band portion including the trumpet-shaped portion is crushed as shown by the chain line, and the heat transfer tube 4 can be pulled out from the insertion hole 2 of the tube plate 1.

Here, the location where the cut groove 15 is formed is not limited to many locations, but it is naturally determined by the conditions at the work site.

In addition, the heat transfer tube 4 after expansion has variations in the inner diameter of its end due to tolerances, and there is often a gap between it and the guide jig 5, but this gap can be completely removed by driving the wedge 14. It can be resolved.

In this case, the relative position of the guide jig foot fixed within the tube end of the heat transfer tube 4 with respect to the inner surface of the tube deviates by the amount of play, so the absolute position of the cutting edge 11 of the chisel 10 with respect to the inner surface of the tube also changes. .

In other words, the depth of the cut groove 15 to be cut also changes, so in order to correspond to this and process the cut groove 15 to a predetermined depth, prepare several types of chisels with different cutting edge heights, and use them. It is only necessary to select the gun 10 suitable for use from among them.

As detailed above, according to the present invention, in order to remove the heat exchanger tube that is expanded and fixed in the insertion hole of the tube sheet, a cut groove is formed along the axial direction on the inner surface of the expanded sales tube end. Because it can be mechanically cut, there is no risk of damaging the inner surface of the tube plate insertion hole, unlike conventional gas cutting. Since the guide jig is positioned by its flange and fixed with a wedge, it is possible to stably drive the chisel for cutting, and the cutting groove can be made as wide as possible. It has excellent features such as being able to process deeply, quickly, and accurately, making it extremely easy to remove the heat exchanger tube, and also making the process itself extremely simple and non-hazardous. be.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional side view showing the fixed state of the expanded heat exchanger tube and the tube sheet, Fig. 2 is an exploded perspective view of an embodiment of the tool of the present invention, and Fig. 3 is an expanded section of the same earthen tool. FIG. 4 is a partially cutaway front view of the same, and FIG. 5 is an explanatory diagram showing the heat exchanger tube in a removed state. 1...tube plate, 2...--insertion hole, 4...
... Heat exchanger tube, 5 ... Guide guide 6 ...
・Body part, 7... collar part, 8... guide groove,
9...cuneiface, 10...tagane, 11.
...Blade tip, 13... Head rest 14...
...Wedge, 15...kerf.

Claims (1)

[Claims] 1. A tool for cutting grooves on the inner surface of the expanded tube end in order to replace a heat transfer tube expanded and fixed in a tube sheet insertion hole in a boiler, heat exchanger, etc. It has a body part which is positioned and fitted by abutting one end flange part on the inside of the end part, and one set of U part of this body part has a guide groove,
A guide jig having a wedge surface formed on each side, and a cross-sectional shape that can be inserted into the guide groove from one end side (a7)) so that the cutting edge can protrude by a predetermined amount outside the circumferential surface of the body. A tool for grooving the inner surface of an expanded tube, comprising a chisel and a wedge driven between the inner surface of the tube end and the wedge surface.