JPH04103956A - Kettle body for hot water boiler - Google Patents

Abstract

PURPOSE:To heighten the strength of connection parts by preventing crevice corrosion or stress corrosion cracking which is generated at the connection parts between tube plates and fire tubes, by a method wherein the end part of the fire tube is fixed to the tube plate by caulking, and this fixed part is subjected to brazing. CONSTITUTION:A kettle body 1 is composed of an inner shell 2, an outer shell 3, upper and lower tube plates 4, 5, and a plurality of fire tubes 6, 6, and a water chamber 7 is formed between the inner shell 2, the outer shell 3 and the upper and lower tube plates 4, 5. Each of the fire tubes 6 passes through the water chamber 7, and both ends thereof are separately connected to the upper and lower tube plates 4, 5, and a combustion gas-collecting chamber 9 communicates with an exhaust gas- collecting chamber 13, through the fire tubes 6. Both ends of the fire tube 6, upper and lower, are separately fixed to the tube plates 4, 5 by caulking, and both ends of the inner shell 2, upper and lower, are also separately fixed to the tube plates 4, 5 by caulking, and the tube plats 4, 5 are closely fitted to the inside of the outer shell 3 by pressing. In addition, caulking parts 6A among the fire tubes 6 and the tube plates 4, 5, caulking parts 2A among the inner shell 2 and the tube plates 4, 5, and press fit parts 4A, 5A among the outer shell 3 and the tube plates 4, 5, are subjected to brazing in a vacuum furnace, a reducing furnace, or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a can for a smoke tube type hot water boiler that can be used for hot water supply, hot water heating, etc.

(B) Conventional technology In recent years, in this type of hot water boiler can, stainless steel, which does not require glass lining, has been used for the inner shell, outer shell, upper and lower tube sheets, and flue tubes that form the water chamber. Then, the tube plate and the smoke pipe are joined by welding such as TIG welding or MIC welding. As a result, not only does welding work take a long time and productivity is poor, but also the joints have a gap structure, which makes crevice corrosion more likely to occur, and when austenitic stainless steel is used, There were problems such as stress corrosion cracking being likely to occur due to residual stress.

Therefore, in order to solve the above-mentioned problems, some people have tried brazing the joint between the tube plate and the smoke pipe using nickel solder. Because they are placed in a furnace, they are susceptible to thermal deformation due to the high heat, causing problems such as the joints coming off before they are brazed, and the joints not having sufficient strength.

(c) Problems to be Solved by the Invention The present invention has been made in view of the above-mentioned facts, and it is possible to prevent the occurrence of crevice corrosion and stress corrosion cracking at the joint between the tube plate and the smoke pipe, while also preventing the occurrence of crevice corrosion and stress corrosion cracking at the joint. The purpose is to increase strength.

(d) Means for Solving the Problems The present invention provides a smoke pipe in a water chamber formed between an inner shell, an outer shell, and an upper and lower tube plate, and makes the pipe plate and smoke pipe made of stainless steel. In the case for a hot water boiler, the end of the smoke pipe is fixed to the tube plate by caulking, and this fixed portion is subjected to a brazing treatment.

<*> Effect With this configuration, the gap between the joint between the smoke pipe and the tube plate is covered with the brazing material, which prevents crevice corrosion and removes residual stress due to the high temperature during the brazing process. Therefore, stress corrosion cracking is also prevented. In addition, since the end of the smoke tube is fixed to the tube plate by caulking, there is no need to worry about the smoke tube coming off the tube plate during the brazing process.Furthermore, the mechanical strength of the fixed part is increased by fixing by caulking. Since the connection between the end of the smoke pipe and the tube plate is less susceptible to thermal deformation, the strength of the connection can be significantly increased.

(f) Example Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

In Figures 1 to 4, (1) is a can of a hot water boiler, and this can (1) has an inner shell (2) and an outer shell (3).
, consists of an upper and lower tube plate (4 x 5) and a plurality of smoke pipes (6) (6), an inner body (2), an outer body (3), and an upper and lower tube plate (4).
) and (5) to form a water chamber (7). A combustion chamber (8) is formed within the inner shell (2).
) and a combustion gas collecting chamber (9) is formed below the water chamber (7). (10) is a lower refractory material that closes off the bottom of the lower tube sheet (5), (11) is an upper refractory material that closes off the top of the combustion chamber (8), and (12) is a material that penetrates the upper refractory material (11). A downward-facing burner facing the top of the combustion chamber (8), (
13) is an exhaust collection chamber provided above the water chamber (7);
4) is a water supply port provided at an intermediate height position or below the water chamber (7), and (15) is a hot water supply pipe connected to the upper part of the water chamber (7). The inner shell (2), the outer shell (3), and the upper and lower tube plates (4)
> (5) and the plurality of smoke pipes (6) (6) are all made of stainless steel, and the smoke pipe (6) is in the shape of a hollow pipe. This smoke pipe (6) is the water chamber (7)
It penetrates through and its both ends are connected to the upper and lower tube plates (4) and (5), respectively, communicating the combustion gas collection chamber (9) and the exhaust gas collection chamber (13). The upper and lower ends of the smoke pipe (6) are fixed to the tube plates (4) and (5) by caulking, respectively.
In addition, the upper and lower ends of the inner body (2) are also each equipped with a tube plate (4) (
5) is caulked and fixed to the tube plate (4>
(5) is press-fitted inside the outer shell (3). Furthermore, the caulking part (6A) between the smoke pipe (6> and the tube plates (4) and (5)), the caulking part (2A) between the inner shell (2) and the tube plates (4) and (5), and the outer shell (3) and tube plate (4) (5)
The fitting portions (4A) and (5A) are brazed using a vacuum furnace, reduction furnace, etc., as shown in FIG. (A) shown in FIGS. 2 and 3 indicates a brazing material such as nickel, copper, or brass.

In addition, to fix the caulking, prepare string extension protrusions by bead processing near the ends of the smoke pipe (6) and inner body (2), respectively, and use the edges of the tube plates (4) and (5) to insert the string extension protrusions. A method is adopted in which the end portions of the smoke pipe (6) and inner body (2) inserted into the pipe are expanded respectively before the ogin and brazing process.

In the hot water boiler body (1) described above, the burner (12
), the combustion gas descends along the inner wall surface of the inner shell (2) and enters the combustion gas collection chamber (9). Then, the combustion gas in the combustion gas collection chamber (9) is reversed and the smoke pipe (6
6) and enters the exhaust collection chamber (13). The exhaust gas that has undergone heat exchange is discharged to the outside through the exhaust pipe.

In this way, when heat exchange occurs between the combustion gas and the water in the water chamber (7), the water that flows into the water chamber (7) from the water inlet (14) becomes hot water and flows through the hot water pipe (15). Sent to the usage department.

According to the embodiment described above, the outer shell (3) and the tube plate (4) (s)
Fitting part (4A) (5A) with inner shell (2> and tube plate (4)
(5> and the caulking part (2A), and the smoke pipe (6) and the tube plate (
4) Since the gaps between the caulked parts (6A) and (5) are all filled with the brazing material (A), it is possible to prevent the occurrence of crevice corrosion at these joints. In addition, since the brazing process is performed using a vacuum furnace or reduction furnace,
During the brazing process, the can body (1) is approximately 900 to 120
Since it will be placed under a high temperature of 0 degrees Celsius, residual stress will be removed by this high temperature, and the occurrence of stress corrosion cracking can also be prevented. Furthermore, since both ends of the smoke pipe (6) and both ends of the inner body (2) are fixed to the upper and lower tube plates (4) and (5) by caulking, the smoke pipe (6) and the inner body (2) are fixed during the brazing process. 2) will not come off from the tube sheets (4) and (5), and the mechanical strength is increased by caulking, making these connections less susceptible to thermal deformation, greatly increasing the strength of the connections. It is something that can be done.

(G) Effects of the Invention Since the present invention is constructed as described above, it is possible to prevent the occurrence of crevice corrosion and stress corrosion cracking at the joint between the tube plate and the smoke pipe, and also to Since these connections are caulked to the plate, there is no need to worry about them coming off during the brazing process, and they are also less prone to thermal deformation, greatly increasing the strength of the connections and increasing durability. can be improved.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a can body showing an embodiment of the present invention, Fig. 2 is an enlarged sectional view of the main part, Fig. 3 is an enlarged sectional view of the caulked part between the smoke pipe and the tube plate, and Fig. 4. 1 is a sectional view of a hot water boiler using a can body according to an embodiment of the present invention. (1)... Can body, (2)... Inner shell, (3)...
・Outer body, (4) (5)...Tube plate, (6)...Fume tube, (6A)...Caulking part, (7)...Water chamber,
(a) Brazing material.

Claims (1)

[Claims] (1) A smoke pipe is installed in the water chamber formed between the inner and outer shells and the upper and lower tube plates, the tube plate and the smoke tube are made of stainless steel, and the end of the smoke tube is connected to the tube plate. 1. A can for a hot water boiler, characterized in that an end of the smoke tube is caulked and fixed to a tube plate, and this fixed portion is subjected to a brazing treatment.