JPH0612163B2 - Boiler suspended element tube support structure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a boiler, and more particularly to a structure for supporting a suspended element tube in a large boiler.

2. Description of the Related Art In a large boiler, as a method of supporting a suspended element tube, there are a method of supporting it with a high crown and a method of supporting it with a pipe puller without supporting it with a high crown.

FIG. 6 shows a conventional structure in which a suspended type element tube is supported by a high crown, 1 is an element tube, 2 is a boiler ceiling tube, 3 is a high crown, 4 is an end bar, 5
Is a skin casing, and 6 is a suspension rod connected to the end bar 4. Further, 7 is a terminal pipe, 8 is a header, and 9 is a suspension rod connected to the header 8.

In such a structure, the weight of the suspended element tube 1 is transmitted from the high crown 3 through the end bar 4 to the suspension rod 6 and is supported thereby. Further, the own weight of the terminal pipe 7 connected to the element pipe 1 is supported by a suspension rod 9 installed in the pipe puller 8.

Needless to say, the element pipe 1 is located inside the furnace with the ceiling pipe 2 as a boundary, and the terminal pipe 7 is located on the ceiling surrounding side. Since the high crown 3 has a high rigidity, the ceiling pipe 2 and the high crown 3 cannot be directly seal-welded, so that the skin tightness is maintained by using the skin casing 5.

On the other hand, FIG. 7 shows a structure for supporting the suspended element tube without using a high crown, and the same parts as those in FIG. 6 are designated by the same reference numerals.

In this structure, the weights of the suspended element pipe 1, the terminal pipe 7, and the header 8 are all supported by the suspension rod 9 installed in the header 8. A seal box 10 is installed at a position where the element pipe 1 penetrates the ceiling pipe 2 and is loosely sealed. That is, the element tube 1 is not completely restrained by the seal box 10 but can be moved in the vertical direction. This is the terminal tube 7
If it is completely restrained because there is no flexibility, the temperature difference between the terminal pipes that occurs when the boiler is started and stopped causes excessive thermal stress at the base of the nozzle welding part of the header 8. This is because Further, since the seal box 10 has a loose seal structure, in order to prevent the high temperature gas of the furnace from flowing into the ceiling enclosure side from here, the ceiling enclosure is pressurized so that the sealing air leaks from the ceiling enclosure side to the furnace side. ing.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention By using the high crown shown in FIG. 6, the high crown 3 is expensive, and a crack is easily generated in the skin casing 5 provided for sealing. There is a problem that the high temperature gas of the above may leak to the ceiling side.

Further, in the case where the high crown shown in FIG. 7 is not used, it is necessary to pressurize the ceiling surrounding portion, so that the ceiling surrounding must be firmly constructed, and thus there is a problem that the weight increases. . In addition, a special expansion has to be used in the joint between the ceiling enclosure and the furnace, and there is a problem that the efficiency of the boiler is reduced due to air leakage to the furnace side.

The present invention has been made to solve such a problem.

Means for Solving the Problems In the present invention, a suspended element pipe that penetrates a ceiling pipe portion of a boiler and is provided inside a furnace, and a terminal pipe that is connected to the suspended element pipe and is located in a ceiling enclosure In a structure for supporting a suspended element tube of a boiler having a header for supporting the terminal pipe and a suspension rod for supporting the header, the length of the arm of the terminal pipe supported by the one header Is set so that the moment generated in the header due to the own weight of the terminal pipe and the suspended element pipe and the moment generated in the header due to the temperature difference between the terminal pipes are within the allowable value. By making the penetrating part of the suspension type element tube a rigid seal structure, the conventional problems are solved.

In effect the unit, although the self-weight of the element pipe and the terminal pipe is supported by pipe pulling, and the moment M _d that occurs the nozzle welded portion of the pipe pulling by these own weight, tube based on the temperature difference between the terminal pipe cross Considering the moment M _t generated in the headstock welded portion with the arm length of the terminal pipe as a parameter, the moment M _d due to its own weight is small if the arm length is short, and the moment M _t due to the temperature difference is opposite. Since the shorter the arm length, the larger the arm length. Therefore, the optimum arm length of the terminal tube is set in order to keep both moments M _d and M _t within the allowable value.

EXAMPLE An example of a supporting structure for a suspended element tube of a boiler according to the present invention will be described in detail below with reference to FIGS. 1 to 5C. In addition, in these figures, FIG.
Since the same parts as those in FIG. 7 are designated by the same reference numerals, the description thereof will be omitted.

In the present invention, while supporting the self-weight of the suspension type element pipe without using a high crown by a heading, by rigidly coupling the penetrating portion of the ceiling pipe portion of the suspension type element pipe,
It is intended to provide a structure that does not pressurize the ceiling.

The conditions that such a structure should satisfy are the following two points.

1) Being able to support the own weight of the element pipe, etc.

2) The temperature difference between the terminal pipes should not cause excessive thermal stress in the headstock welds.

Thus, FIG. 1 shows a model for the above discussion.
Further, the moment M _d generated in the nozzle welded portion 11 of the header 8 by its own weight W and the moment generated in the header welded portion of the header due to the temperature difference ΔT = T ₁ −T ₂ between the two terminal pipes A and B. A simplified model for obtaining M _t is shown in FIGS. 2 and 3.

In FIG. 2, the strain energy U acting on the nozzle due to its own weight W is expressed by the following equation (1).

Here, E and I represent the Young's modulus and the second moment of area of the terminal tube 7, respectively.

The deformation angle θ of the weld head 11 is It is given by, but from the condition that this is 0, the following formula
(2) is led.

Now, if l ₁ = l ₂ , And the moment increases in proportion to the arm length l ₁ of the terminal tube 7.

Further, in FIG. 3, the amount of free heat deformation due to the temperature difference ΔT is given by αl ₂ ΔT. Here, α represents the coefficient of linear expansion of the terminal tube 7.

On the other hand, in equation (1), the displacement δ is Which is consistent with αl ₂ ΔT.

from now on, Is guided. Substituting equation (2) into this leads to equation (3) below.

Now, if l ₁ = l ₂ , And the moment becomes smaller in proportion to the arm length l ₁ of the terminal tube 7.

That is, when the length of the arm of the terminal pipe is made smaller with respect to its own weight, the stress generated in the pipe head nozzle welded portion is smaller, but it becomes larger against the temperature difference. Therefore, in order to keep the generated stress within the permissible value for both the self-weight and the temperature difference, there is an optimum arm length.

It should be noted that although the axial force and the shearing force other than the above bending moment act on the nozzle base welded portion, the bending moment is predominant and will be omitted.

Bending stresses σd and σt are generated by the moments M _d and M _t , and these are represented by the following equations (4) and (5).

_{σd = M d / Z ... (} 4), σt = M t / Z ... (5) where, Z is shows a section modulus of the terminal pipe 7.

These generated stresses should be within the following allowable values.

1) With respect to its own weight σd1.5Sh 2) With respect to thermal stress σt1.25Sc + 0.25Sh where Sh: allowable stress of the terminal tube at the design temperature Sc: 〃 at room temperature, respectively.

For the actual hanging type element, the arm length l ₁ is 250 ~
It has been confirmed that both equations are satisfied when the distance is 500 mm.

FIG. 4 shows a specific configuration of the present invention, in which 1 is a suspended element tube, 2 is a ceiling tube, 7 is a terminal tube, and 8 is a terminal tube.
Is a pipe head, 9 is a suspension rod, and 12 is a seal box. The weights of the element pipe 1, the terminal pipe 7 and the header 8 are supported by a suspension rod 9, and a portion where the element pipe 1 penetrates the ceiling pipe 2 is completely sealed by a seal box 12. Further, the terminal tube 7 is provided with an appropriate flexibility so that its own weight can be supported and a temperature difference between the terminal tubes 7 occurring at the time of starting or stopping the boiler can be absorbed. Furthermore, the length of the arm of the terminal pipe 7 supported by one pipe puller is adjusted by the weight of the terminal pipe 7 and the suspended element pipe 1
The moment M _d generated at the nozzle welded portion and the moment M _t generated due to the temperature difference are set to lengths suitable for being within the respective allowable values.

The structure of the portion where the suspended element pipe 1 penetrates the ceiling pipe 2 is shown in FIGS. 5A to 5C. That is, in FIG. 5A, the sleeve 13 is fixed to the element pipe 1, and the rectangular seal box 12 is welded to the sleeve 13 and the ceiling pipe 2. Also, FIG.
The only difference is that a semicircular seal box 12a is used instead of the rectangular seal box 12 in FIG. Further, FIG. 5C shows the seal boxes 12, 12a.
The sleeve 13 is directly welded to the fins 14 of the ceiling pipe 2 without using.

EFFECTS OF THE INVENTION As described in detail above, according to the present invention, there is no risk that high temperature gas on the furnace side will leak to the ceiling enclosure side. Further, since it is not necessary to pressurize the ceiling enclosure, the ceiling enclosure can be made lighter, there is no air leak from the ceiling enclosure side to the furnace side, and there is no fear of lowering boiler efficiency. Further, since no high crown is used, it is economically advantageous.

[Brief description of drawings]

FIG. 1 is a model diagram shown in order to examine the conditions required for the present invention, and FIG. 2 is a simplified model diagram for obtaining the moment M _d generated in the header portion welded portion by its own weight. FIG. 3 is a simplified model diagram for obtaining the moment M _t generated by the temperature difference, FIG. 4 is a configuration diagram showing an embodiment of the present invention, and FIGS. 5A to 5C are seals in FIG. FIG. 6 and FIG. 7 are sectional views showing a specific example of the box portion, and FIGS. 6 and 7 are views showing two examples of a conventional suspension type element tube support structure. 1 ... Suspended element pipe, 2 ... Ceiling pipe, 7 ... Terminal pipe, 8 ... Pipe fitting, 9 ... Suspension rod, 11 ... Pipe welded part, 12 ... Seal box.

Claims (1)

[Claims] 1. A suspension type element pipe which is provided inside a furnace by penetrating a ceiling pipe part of a boiler, a terminal pipe which is connected to the suspension type element pipe and which is located inside a ceiling, and which supports the terminal pipe. In a structure for supporting a suspended element pipe of a boiler having a header and a suspension rod supporting the header, the arm length of the terminal pipe supported by the one header is determined by The moment generated in the header due to its own weight with the shaped element pipe and the moment generated in the header due to the temperature difference between the terminal pipes are set within the allowable value, and the ceiling pipe part and the suspended element pipe A supporting structure for a suspended element tube of a boiler, characterized in that a penetrating portion has a rigid seal structure.