JPS5916535B2 - How to fix the tube to the tube plate in a shell tube heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for fixing tubes to a tube sheet in a shell-tube heat exchanger.

More specifically, the present invention relates to a fixing method in which a tube tube having a large number of fins protruding from its inner peripheral surface is mechanically expanded using a tube expander and then fixed to a tube plate of a shell.

Conventional heat exchangers have a large number of fins protruding from the inner circumferential surface of the tube in order to improve heat exchange. When the tube is expanded and fixed to a tube sheet, the fins at the expanded portion are shaved off by the expansion and turn into metal powder, which enters the inside of the tube.When used in a refrigeration system, the metal powder prevents rotation of the bearing part of a compressor, etc. There was a problem in that it bit into the sliding part or the sliding part between the cylinder and the zero piston, damaging the rotating part.

That is, when expanding the tube mechanically, as shown in FIGS. 8 and 9, a tube expansion jig of a tube expansion machine 05 consisting of a tapered tube expansion mandrel M and a frame F supporting a plurality of rollers R is used. The frame F is inserted into the expanded tube part of the finned tube C whose inner surface has been processed, and the mandrel M is rotated and moved forward, and the forward rotation of the mandrel M causes the roller R to revolve while rotating on its own axis. The tube C is expanded by moving outward and fixed to the tube plate P. During this expansion, the planetary rotation of the roller R, which revolves while rotating, causes the fins protruding from the inner surface of the tube C to expand. The pipe is expanded while crushing H and generating metal powder D15.

However, in order to solve more problems than before, the inner surface of the expanded portion of the tube C is ground by reaming or the like before expansion, and the inner surface is scraped off together with the fins H, as shown in Figure 10. However, as the number of machining steps increases, the processing cost increases, and the wall thickness of the tube becomes thinner, which causes problems in terms of strength, especially when a copper tube is used.

Also, when expanding the tube and fixing it to the tube sheet, in order to avoid problems such as stress concentration and corrosion, it is necessary to
The pipe is expanded from a position 3m/m outward to the end of the tube, and the pipe expansion machine is equipped with a pipe expansion allowance adjustment mechanism, and this adjustment mechanism adjusts the pipe expansion length according to the wall thickness of the tube sheet. Therefore, it was necessary to adjust the tube expansion length using the adjustment mechanism each time the tube plate wall thickness changed.

Therefore, the present invention was invented in view of the above-mentioned conventional problems.The main purpose is to expand the tube without generating metal powder without having to grind the expansion part of the tube in advance, and to avoid high costs due to an increase in the number of machining operations. Another object of the present invention is to provide a fixing method that solves the above problems and strength problems, and another object is to provide a fixing method that allows the tube expansion length to be easily set without having to adjust the tube expansion length using a tube expander.

That is, in the present invention, a cylindrical piece having an outer diameter slightly smaller than the diameter of an imaginary cylinder connecting the inner tips of the fins is inserted into the portion of the tube fixed to the tube plate, and a tube expansion mandrel and a tube expansion mandrel are inserted into the inside of this piece. The tube expansion jig consisting of a plurality of rollers arranged radially and supported by a frame is inserted into the mandrel, the mandrel is rotated forward, and the rollers are rotated and revolved while pressing the inner surface of the piece. expanding the tube together with the piece;
The piece is fixed to the expanding end of the tube and at the same time the tube is fixed to the tube plate, and the insertion amount of the piece is set at the insertion rear end of the cylindrical piece. By providing the restricting body, the expansion length of the tube can be easily set using the piece.

Embodiments of the fixing method of the present invention will be described below based on the drawings.

The heat exchanger shown in Figs. 1 and 2 is a shell and type evaporator, and has a cylindrical shell 1 having a water inlet pipe 1a and a water outlet pipe 1b, a tube plate 2 at the front, and a rear cover at the rear. 3 are each fixed by a fixing means such as welding, a large number of U-shaped tubes 4 are installed inside, and the open ends of the tubes 4 are connected to the tube plate 2.
A plurality of through holes 2a formed in the tube plate 2 are inserted into the tube plate 2, and a plurality of buttfuls 5 are attached to the middle part of the tube plate 2. The disposed front cover 7 is fixed with fixing means such as screws, and each chamber divided by the partition plate 6 is connected to a liquid pipe contact pipe 8 with a small diameter and a gas pipe with a large diameter. tube 9
This is the one with the .

Therefore, the tube 4 has a large number of spirally protruding fins 4a formed over its entire length. For example, the tube 4 has an outer diameter of 12.7 mm and a thickness of 0.8 m/m. In this case, the fins 4a have an inclination angle of 300 and a height of 0.
3 m/m, and 60 strips are provided at 6 diagonal intervals all over the inner circumference. Therefore, in the present invention, the tube 4 in the heat exchanger configured as described above is expanded and fixed to the tube plate 2 using a tube expansion jig of a tube expansion machine. This will be explained based on FIGS. 4 to 7.

As the tube expander used in the fixing method of the present invention, the same tube expander as in the conventional method shown in FIGS. 8 and 9 may be used, or other tube expanders may be used.

In this embodiment, as shown in FIGS. 5 and 7, similar to the tube expanding machine shown in FIGS. A pipe expanding machine with a pipe expanding jig consisting of R is used.

The fixing method of the present invention involves forming a cylindrical piece 10 having an outer diameter slightly smaller than the diameter of an imaginary cylinder connecting the inner tips of a large number of fins 4a formed on the inner surface of the tube 4. Before expanding the tube 4 as shown in
into the fixed part to the tube plate 2, and then this piece 10
Insert the tube expansion jig into the inside of the tube to expand the tube 4 together with the piece 10 as shown in FIG.
As shown in the figure, the piece 10 is fixed to the expanded end of the tube 4, and at the same time, the tube 4 is fixed to the tube plate 2.

More specifically, first, the piece 10 is inserted into the portion of the tube 4 fixed to the tube plate 2, and then the piece 10 is
The frame F is inserted into the interior of the piece 10, and the mandrel M is rotated and moved forward. As the mandrel M is rotated forward, the roller R supported by the frame F is moved along the inner surface of the piece 10. The pipe expands the piece 10 by rotating around its axis and moving outward in the radial direction, and as a result of this pipe expansion, the outer circumferential surface of the piece 10 comes into contact with the inner circumferential surface of the tube 4, and the fin 4a
The tube 4 is expanded by crushing the tube 4 in close contact with the tube 4.

At this time, the piece 10 crushes the fins 4a of the tube 4 by expanding the piece 10, so no metal powder is generated as in the conventional case. However, even if metal powder is generated due to the crushing, Since this metal powder is pressed and held between the piece 10 and the tube 4, it does not fly out outside the expanded tube portion.

After the tube has been expanded as described above, the mandrel M is rotated backwards and pulled out toward the front, and the piece 10 remains in close contact with the inner circumferential surface of the tube 4. It turns out.

Therefore, by leaving this piece 10 in place, the portion of the tube 4 fixed to the tube plate 2 is reinforced. However, when expanding the tube 4 and fixing it to the tube sheet 2 as described above, in order to avoid stress concentration and corrosion, the tube 4 is
The expansion length is adjusted to prevent the tube from expanding by ~3m/m.

According to the conventional method, this adjustment is performed by installing a pipe expansion allowance adjustment mechanism in the pipe expansion machine and operating this adjustment mechanism.
If the wall thickness of the tube plate 2 changes, it is necessary to adjust it each time.
Since the present invention uses the piece 10, by providing a restrictor 11 at the insertion rear end of the piece 10 to limit the amount of insertion of the piece 10, adjustment of the tube expansion length can be made unnecessary.

That is, as described above, the tube 4 is expanded by the piece 1.
0, the length of the piece 10 is set in advance according to the wall thickness of the tube plate 2, so that the tube expansion length is determined, and the roller R of the tube expansion machine is There is no need to restrict the insertion position.

Therefore, by providing the limiter 11 on the piece 10, it is possible to eliminate the need for the operation of adjusting the tube expansion length, improve the workability of the length, and solve problems caused by adjustment errors. In the above fixing method, two or more annular grooves 2b may be provided on the inner circumferential surface of the through hole 2a formed in the tube sheet 2 as shown in FIG. 4, or an adhesive may be applied to the inner circumferential surface in advance. By doing this, even stronger fixation can be obtained.

That is, when the tube 4 is expanded, the thick part of the tube 4 flows into the annular groove 2b and can be fixed in a crimped state, so that the tube 4 can be tightly attached to the inner surface of the through hole 2a and can be fixed even more firmly. By adding the fixing function of adhesive, it can be fixed even more firmly.

Furthermore, the annular groove 2b can be used in combination with an adhesive, thereby further increasing the fixing strength. As described above, the present invention is configured such that a tube having a large number of fins protruding from its inner peripheral surface is expanded through a piece, and the piece is fixed to the expanded portion of the tube, and at the same time, the tube is fixed to a tube plate. As a result, even if the inner surface of the tube is ground before expansion and the fins of the tube are not ground down, no metal powder is generated due to crushing of the fins during expansion.
Moreover, even if metal powder is generated, the metal powder is sealed between the outer surface of the cylindrical piece and the inner surface of the tube. This completely eliminates the conventional problem of damaging equipment such as the sliding parts of the compressor, and since no grinding is required, there is no increase in the number of machining steps and high costs.

Moreover, according to the present invention, the piece is expanded, the piece and the tube are integrated, and both are fixed to the tube plate, so that the piece remains even after the tube expansion, so that the tube can be expanded. Not only can the strength of the piece compensate for the decrease in strength due to tube expansion, but also the strength of the expanded end of the tube can be increased. In this configuration, by providing a restrictor on the piece, the length of the tube expansion tube can be set, which eliminates the hassle of having to install a tube expansion allowance adjustment mechanism in the tube expander and adjusting it every time the wall thickness of the tube sheet changes. It can be omitted.

[Brief explanation of the drawing]

Figure 1 shows an example of a heat exchanger to which the method of the present invention is applied.
2 is a side view with the front cover omitted, FIG. 3 is a front view of only the tube with part omitted, and FIGS. 4 to 7 are explanatory diagrams for explaining the method of the present invention. , Fig. 4 is a cross-sectional front view before pipe expansion, Fig. 5 is a cross-sectional front view during pipe expansion, Fig. 6 is a cross-sectional front view after pipe expansion, Fig. 7 is an enlarged cross-sectional side view during pipe expansion, and Fig. 8 is a cross-sectional front view before pipe expansion. Figures 1 through 10 are explanatory diagrams showing a conventional fixing method. 2...Tube plate, 4...Tube, 4a.
...Fin, 10...Cylindrical piece, M
...Pipe expansion mandrel, F...Frame, R...Roller.

Claims (1)

[Scope of Claims] 1. Expanding a tube with a large number of fins protruding from the inner peripheral surface using a tube expansion jig consisting of a tube expansion mandrel and a plurality of rollers arranged radially on the mandrel and supported by a frame, A method of fixing a tube to a tube plate in a shell-tube heat exchanger in which the tube is fixed to a tube plate of a shell, the method comprising: a virtual cylinder connecting the inner blade tip of the fin to a portion of the tube fixed to the tube plate; A cylindrical piece having an outer diameter slightly smaller than the diameter of is inserted, the tube expansion jig is inserted into the inside of this piece, the mandrel is rotated forward, and the roller is rotated while pressing the inner surface of the piece. The shell-tube heat exchanger is characterized in that the tube is expanded together with the piece while rotating, and the piece is fixed to the expanded end of the tube and at the same time the tube is fixed to the tube plate. How to fix the tube to the tube plate. 2. The device according to claim 1, characterized in that the cylindrical piece to be inserted into the fixed portion of the tube plate is provided with a limiter at the insertion rear end thereof to limit the amount of insertion of the piece. A method of fixing tubes to tube sheets in shell-tube heat exchangers.