JPH1078201A - Heat transfer tube steady rest fittings - Google Patents

Abstract

(57) [Summary] [Problem] There is no unwelded portion at the joint between the heat transfer tube and the steady rest which causes cracks, material costs can be reduced, welding is easy, and automatic welding can be applied. Provide a possible heat transfer tube steady rest. Kind Code: A1 Abstract: In a steadying metal fitting for a heat transfer tube which is attached to the surface of a heat conducting tube 1 and 1 'to maintain a distance between adjacent heat conducting tubes within a predetermined range, the steadying fitting is a first portion 2a,
2b, 2c and second portions 2a ', 2b', 2c '. One end of each of the first portions 2a, 2b, 2c has a heat transfer tube 1, 1 so that there is no unwelded portion which may cause a crack. ′, And the other end of the first portion 2a, 2b, 2c
a ', 2b' and 2c 'are welded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steady rest provided between heat transfer tubes of a boiler.

[0002]

2. Description of the Related Art Many heat transfer tubes for exchanging heat are arranged in a combustion gas passage of a boiler. FIG. 3 schematically shows a structure of a heat transfer tube of such a boiler. Between these heat transfer tubes 1, there is provided a steadying metal fitting 2 for suppressing the swing of the heat transfer tubes in the furnace width direction and in the front-rear direction due to the deformation of the flow of the combustion gas, the gas pressure or the temperature difference. ing.

The purpose of arranging the steady rest 2 between the heat transfer tubes 1 is to suppress the run out to make the flow of the combustion gas uniform, to keep the heat load in the furnace width direction constant, and to make the heat sink 7 and 7 'at the header 7 and 7'. It is to suppress the progress of fatigue or creep fatigue damage due to excessive bending stress at the joint between the nozzle and the heat transfer tube 1. Therefore, the steady rest 2 is arranged so as to prevent relative movement and contact between the heat transfer tubes 1 or to partially support the load of the heat transfer tubes 1.

FIG. 4 is a view showing an example of a conventional steady rest 2 and its joining to the heat transfer tubes 1 and 1 ', and FIG. 5 is a view showing details of a joining portion.

[0005] In FIG. 4, the distance between the heat transfer tube 1 and the heat transfer tube 1 ′ is maintained within a predetermined range by the steady rest 2. Such a steady rest 2 is usually formed by welding from the outside of the steady rest 2 to form a weld 3.
Attach to heat transfer tubes 1, 1 '. In this case, since it is extremely difficult to weld from the inside of the steady rest 2 due to restrictions on the shape and dimensions of the steady rest 2, the unwelded portion 5 is provided on the gap 4 side inside the steady rest 2. Occurs.

[0006] Since such an unwelded portion 5 becomes a so-called notch, when a load is applied to this portion,
Stress concentration occurs, and as shown in FIG. 5, cracks 6 are likely to occur in the welded portions (base material of heat transfer tube, weld heat affected zone, weld metal, and steady rest). For example, during boiler operation, heat transfer tube 1
1 'is cooled to a predetermined temperature by the internal fluid, but the end of the steady rest 2 is heated by the combustion gas and rises to a temperature close to the ambient temperature. In the case of being restrained by the steady rest 2 or the heat transfer tubes 1, 1 ', etc., a thermal load is generated at the welded portion of the steady rest 2. Further, even when these heat transfer tubes swing in the furnace width direction or the front-back direction, a bending moment is generated at the welded portion between the heat transfer tubes 1 and 1 ′ and the steady rest 2.

When such a thermal load or bending moment acts on the unwelded portion 5, a crack 6 is generated due to stress concentration, and depending on the direction in which the load or moment acts, there is a possibility that the crack 6 will propagate into the tube wall of the heat transfer tube 1. is there.

The crack 6 originating from such an unwelded portion 5
As one of the methods for preventing the heat transfer tube from being damaged due to the generation and progress of water, there is a method disclosed in Japanese Utility Model Laid-Open No. 63-97005. In this method, another tube is provided outside the heat transfer tube, and a steady rest is provided on the outside tube. According to this, even when a thermal load or a bending moment acts on the steady rest welding part, the heat conducting pipe is not directly joined to the heat transfer pipe, so that the heat transfer pipe is subjected to the heat load acting on the steady rest fitting. And is not directly affected by bending moment. However, since the steady rest is heated to a temperature close to the ambient temperature, it is necessary to make the material of the steady rest excellent in high-temperature oxidation resistance or to design the operating temperature to be limited. Materials having excellent resistance to high-temperature oxidation are generally expensive, and there is a problem in that the time and cost required for processing and mounting the steady rest are increased. Another problem is that the outer tube acts as a coating on the inner tube, preventing heat exchange.

Another method for preventing damage to the heat transfer tube is disclosed in Japanese Utility Model Laid-Open No. 62-185305. In this method, a steady rest is formed integrally with the heat transfer tube on the surface of the heat transfer tube. The connection between the heat transfer tubes is
This is performed by connecting the steady rest provided on the heat transfer tube using a pin. In the heat transfer tube having this structure, no unwelded portion is generated between the heat transfer tube and the steady rest, so that a crack due to the unwelded portion does not occur or propagate.

However, the production of such a heat transfer tube has the following problems. That is, when a conventional heat transfer tube having a uniform wall pressure is used, the tube is bent into a predetermined shape, then appropriately welded to assemble a coil, and then a steadying bracket is welded to a predetermined position of the coil. . On the other hand, in the case of using a heat transfer tube integrally formed with the above-mentioned steady rest, firstly, a required bending process is performed on the heat conducting tube not provided with the steady rest, and after assembling to a certain extent, a predetermined shape of the heat conducting tube is used. The position is cut, and a heat transfer tube integrally formed with a steady rest is attached to the cut portion by welding. Therefore,
There is a problem that the number of processing steps increases.

Further, since the pins connecting the anti-vibration fittings are not cooled by the medium flowing in the heat transfer tube, there is a problem that the temperature rises to the ambient temperature and is liable to burnout.

Further, when replacing the defective portion of the heat transfer tube to which the conventional steady rest is welded, the heat transfer tube is cut to include the defective portion after the steady rest is temporarily cut off from the heat transfer tube. After removal, a new heat transfer tube is welded and attached to that location, and a steady rest is welded to this tube. Since such an operation is performed in a narrow place, it is extremely difficult to perform high quality welding. In addition, since automatic welding cannot be applied, the operator is forced to work for a long time in a narrow part.

[0013]

As described above, in the steady rest 2 of the prior art, there is a problem that a crack 6 starting from the unwelded portion 5 is likely to be generated. In addition, as a countermeasure for this problem, in the case where the portion of the heat transfer tube to which the anti-sway fitting is attached has a double structure, it is necessary to use a material having excellent resistance to high-temperature oxidation. There is a problem that the time and cost required for processing and mounting the fastener are increased, and that heat exchange is hindered. Further, in the case where the heat transfer tube and the steady rest are integrally formed, there is a problem that the number of assembling steps is increased, and a pin connecting the steady rest is susceptible to burnout or the like. Further, there is a problem that the working conditions of the welding operation when replacing the defective portion of the heat transfer tubes 1 and 1 'are poor, the welding operation is difficult, and automatic welding cannot be applied.

An object of the present invention is to solve the above problems,
Eliminates the unwelded part at the joint between the heat transfer tube and the steady rest that causes cracks, reducing material costs.
Heat transfer tube is not hindered, does not use connecting pins that are susceptible to burnout, etc., facilitates welding work, and can apply automatic welding to welding work at the time of replacement. To provide metal fittings.

[0015]

In order to achieve the above object, according to the present invention, a steadying fitting for a heat transfer tube which is attached to the surface of a heat transfer tube and maintains an interval between adjacent heat transfer tubes within a predetermined range is provided. One end of the first portion is divided into a first portion and a second portion, and one end of the first portion is welded to the heat transfer tube so that there is no unwelded portion causing a crack, and the other end of the first portion is Is welded to the second portion.

In this case, the first portion and the second portion can be formed of different component materials.

In this case, it is also possible to divide the second part into at least two or more small parts in the longitudinal direction, and to weld the divided small part of the second part to the first part. is there.

[0018]

Embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a side view and a sectional view showing a first embodiment of a steady rest according to the present invention.

In this embodiment, the steady rest 2 is connected to the first portions 2a, 2b, 2c and the second portion, respectively.
2a ', 2b', and 2c '. That is, first, the first portion 2a is welded to the heat transfer tube 1 from the outside. Further, the first portion 2b is welded to the heat transfer tube 1 'from outside. Further, the first portion 2c is welded to the heat transfer tube 1. In this case, the height of the first portions 2a, 2b, 2c in the direction of the adjacent steady rests is set small enough to allow the welding torch to enter the gap 4 between the steady rests. For this reason, since welding work can also be performed from the gap 4 side inside the steady rest 2, fillet welding is performed from both sides of each steady rest to form the welded portion 3.

Next, a second part 2 for maintaining the pipe spacing is provided.
a 'is welded and joined to the first portion 2a to form a weld 3'. In this case, an appropriate groove processing is performed on the welded portion in advance. This welding may be one-side fillet welding as shown in FIG. 1 or may be double-side welding. Hereinafter, similarly, the second portion 2b 'for maintaining the tube interval is welded to the first portion 2b to form a welded portion 3', and the second portion 2c 'for maintaining the tube interval is similarly formed. Is welded to the first portion 2c to form a weld 3 '.

First parts 2a, 2b, 2c according to the present invention
Is simple in shape and small in size, so that automatic welding which has been difficult to apply conventionally can be performed, and disadvantages associated with an increase in welding locations can be sufficiently compensated.

The material of the steady rest 2 is the material of the target heat transfer tube (in a normal boiler, the material of the heat transfer tube is appropriately selected according to the operating temperature. Generally, carbon steel, low alloy steel, or austenitic stainless steel tube is used. ) Together with the usage conditions. In this case, the heat transfer tube is cooled by the internal fluid, whereas the steady rest 2 is hardly cooled and has a high temperature close to the ambient temperature. Therefore, in general, a high-grade material having better high-temperature oxidation resistance than the heat transfer tube is used. use. The welding of both is performed by selecting a welding material suitable for the material of the steady rest 2.

In the present invention, since the steady rest 2 is divided into a first part 2a, 2b, 2c and a second part 2a ', 2b', 2c ', the material of both parts is reduced. Can be selected separately. In other words, only the second portions 2a ', 2b', and 2c 'exposed to higher temperatures can be made of a material having higher resistance to high-temperature oxidation, thereby reducing the amount of expensive materials used. be able to. For example, when the heat transfer tube is a high-temperature superheater and the material is austenitic stainless steel, the first portions 2a, 2b,
2c is a plate material of the same material, and the second portions 2a ', 2b',
If 2c 'is a cast of 50Cr50Ni, the amount of the latter can be reduced to about half as compared with the conventional technology, and the material cost can be greatly reduced.

Further, the steady rest 2 is connected to the first portion 2.
a, 2b, 2c and the second portions 2a ', 2b', 2c ', the second portion 2a for maintaining the space between the tubes when a portion of the heat transfer tube requiring replacement occurs. ', 2
The b 'and 2c' are cut off from the first portions 2a, 2b and 2c, and then the heat transfer tube is cut so as to include the defective portion and replaced with a new one. In this case, if the first portions 2a, 2b, and 2c to be newly welded to the newly installed heat transfer tubes are welded in advance, semi-automatic MIG welding and the like can be applied even in a narrow place in the actual furnace, so that efficient work is performed. Becomes possible. Therefore, the working time can be reduced, and the burden on the worker and the number of man-hours can be reduced.

FIG. 2 is a side view and a sectional view showing a second embodiment of the steady rest according to the present invention.

In this embodiment, the first portions 2a, 2b, 2c to be welded to the heat transfer tube and the second portions 2a ', 2b', 2c 'divided in the longitudinal direction of the heat transfer tube are respectively welded. I do. Although the figure shows a case where the second part is divided into two parts, the second part may be divided into three parts or more.

Thus, the second parts 2a ', 2b',
When 2c 'is divided, each part can be reduced in size, so that the material used for the steady rest 2 can be saved and the weight can be reduced. Further, since the welding length is shortened, the working time can be reduced. Also in the second embodiment, as in the first embodiment, it is possible to use a higher-grade material than the heat transfer tube for the second portions 2a ', 2b', 2c '. Semi-automatic MIG
Application such as welding is also possible.

[0029]

According to the present invention, the steady rest is formed of the first portion and the second portion, and the welding of the first portion to the heat transfer tube is performed outside and inside the first portion. Therefore, there is an effect that the unwelded portion which causes the crack is eliminated.

Further, the first portion has a simple shape, a small size, and can be applied to automatic welding, so that there is an effect that work efficiency can be improved.

Further, since only the second portion exposed to a higher temperature can be made of an expensive material having higher resistance to high-temperature oxidation, the material cost can be reduced.

If a portion of the heat transfer tube that needs to be replaced occurs, the first portion is welded to the newly installed heat transfer tube in advance, so that semi-automatic MIG welding or the like can be performed even in a narrow place in the actual furnace. Since the present invention can be applied, efficient work can be performed, work time can be reduced, and the burden on the worker and the number of man-hours can be reduced.

Also, the heat transfer tube at the mounting part of the steady rest
Since there is no heavy structure, there is an effect that heat exchange is not hindered.

Further, there is an effect that a connecting pin which is susceptible to burning or the like is not used.

[Brief description of the drawings]

FIG. 1 is a side view and a cross-sectional view showing a first embodiment of a steady rest according to the present invention.

FIG. 2 is a side view and a sectional view showing a second embodiment of a steady rest according to the present invention.

FIG. 3 is a diagram schematically showing a structure of a heat transfer tube of the boiler.

FIG. 4 is a cross-sectional view showing an example of a conventional steady rest and its joining to a heat transfer tube.

FIG. 5 is an enlarged view of a portion A in FIG. 4;

[Explanation of symbols]

 1, 1 '... heat transfer tube 2 ... steady rest fitting 3, 3' ... welded part 4 ... gap 5 ... unwelded part 6 ... crack 7 ... header 2a, 2b, 2c ... first part 2a ', 2b', 2c ': second part

Claims (3)

[Claims] An anti-sway fitting for a heat transfer tube attached to a surface of a heat transfer tube to maintain an interval between adjacent heat transfer tubes within a predetermined range, wherein the anti-sway fitting is a first part, a second part and a second part. One end of the first portion is welded to the heat transfer tube such that there is no unwelded portion causing a crack, and the second portion is welded to the other end of the first portion. A heat transfer tube steadying bracket. 2. A heat transfer tube fitting according to claim 1, wherein said first portion and said second portion are formed of different component materials. Steady bracket. 3. The steady rest according to claim 1, wherein said second portion is divided into at least two or more small portions in a longitudinal direction, and said second portion is divided into at least two small portions. A part for welding a heat transfer tube, the part being welded to the first part.