JPH0547924Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a device for preventing overheating at the gas inlet end of a heat transfer tube such as the smoke tube of a fire tube boiler, and in particular to an overheating prevention device using a ceramic ferrule.

[Conventional technology]

For example, in a smoke tube boiler, as shown in Figure 2,
The combustion gas G is designed to flow from the furnace tube 1 through the smoke tube 2 into the smoke tube 3, which is a heat transfer tube. Because the cooling effect of the canned water 4 is small and because it receives radiant heat from the wall 2a forming the smoke chamber, it is easily overheated. Therefore, large thermal stress is generated at the gas inflow end 3a as the boiler starts and stops, and as a result, the gas inflow end 3a
There is a risk that the attachment portion 6 between the tube plate 5 and the tube plate 5 may become loose or crack, resulting in water leakage.

Therefore, conventionally, as shown in Figure 3,
Ceramic ferrule 7 with flange 7a
It is usual to fit and attach the gas inflow end side portion of the smoke pipe 3 to prevent overheating of the gas inflow end 3a. Incidentally, by filling a heat-resistant adhesive 8 between the ferrule 7 and the smoke pipe 3 or between the flange 7a and the tube plate 5, the ferrule 7 is prevented from falling off due to combustion vibrations.

[Problems that exchange attempts to solve]

However, in such an overheating prevention device, the flange 7a of the ferrule 7 gets in the way, making it impossible to visually recognize the mounting portion 6 of the gas inlet end 3a from the outside.

Therefore, during regular boiler inspections,
Unless the ferrule 7 is removed, it is not possible to check for water leaks or cracks.

As described above, since the ferrule 7 is fixed to the smoke pipe 3 or the tube plate 5 with the adhesive 8, the ferrule 7 must be destroyed in order to be removed. As described above, it is extremely uneconomical to destroy the expensive ceramic ferrule 7 and replace it with a new ferrule every time a periodic inspection is performed.

This invention was made in view of these points,
To provide an overheating prevention device for a gas inflow end of a heat transfer tube, which can effectively prevent overheating of the gas inflow end of the heat transfer tube, and allows the presence or absence of a water leakage point or a crack generation point to be easily confirmed without removing a ferrule. The purpose is to

[Means to solve the problem]

The overheat prevention device of the gas inflow end of the heat transfer tube of the present invention, which solves this problem, has a straight cylindrical ceramic ferrule fitted into the heat transfer tube with a predetermined amount L protruding from the gas inflow end. , the protrusion length L is set to 1/10D to 1D with respect to the heat transfer tube diameter D.

[Effect]

The overheating prevention effect of the gas inlet end by the ferrule is the same as in the conventional device described above. especially,
In the device of the present invention, the protruding portion of the ferrule from the gas inflow end has a protruding length L of 1/10D to
By setting it to 1D, the same effect as the ferrule flange in the conventional device can be achieved. This has been confirmed by experiment.

In addition, since the ferrule has a straight cylindrical shape, the attachment part of the gas inlet end can be seen from the outside without removing the ferrule, making it easy to check for water leaks or cracks. .

〔Example〕

Hereinafter, the configuration of the present invention will be specifically explained based on the embodiment shown in FIG. This embodiment relates to an example in which the present invention is applied to an overheating prevention device at the gas inlet end of a smoke tube of a smoke tube boiler as shown in FIG.

The overheating prevention device shown in FIG. 1 is constructed by fitting and attaching a straight cylindrical ceramic ferrule 17 into a smoke tube 3, which is a heat transfer tube, with the ferrule projecting a predetermined amount L from its gas inlet end 3a. Although not shown, a heat-resistant adhesive is filled between the smoke pipe 3 and the ferrule 17. Also, Ferrule 17
The inner diameter corner of the protruding end face is chamfered at the rounded portion 17a.

The protrusion length L of the ferrule 17 from the gas inflow end 3a is appropriately set in the range of 1/10D to 1D with respect to the heat transfer tube diameter D. By the way, according to experiments, if the protrusion length L is shorter than 1/10D, the overheating prevention effect cannot be effectively achieved, and if it is larger than 1D, the inflow and flow of the combustion gas G cannot be performed smoothly. was confirmed.

[Effect of idea]

According to the present invention, overheating of the gas inlet end of a heat transfer tube such as a smoke pipe can be effectively prevented.

Moreover, since the ferrule has a straight cylindrical shape without a flange or the like that hides the attachment part at the end of the heat exchanger tube, it is easy to check for water leaks or cracks without removing the ferrule. I can do it. Therefore, periodic inspections of the smoke tube boiler can be carried out without destroying the ferrule, and the ferrule can be used for many years.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of the overheat prevention device at the gas inflow end of a heat exchanger tube according to the present invention, FIG. 2 is a cross-sectional view showing the main parts of a smoke tube boiler, and FIG. FIG. 2 is a sectional view showing a conventional device. 3... Smoke pipe (heat transfer tube), 3a... Gas inflow end,
17...Felur.

Claims (1)

[Scope of utility model registration request] A straight cylindrical ceramic ferrule is fitted into the heat transfer tube with a predetermined amount L protruding from the gas inlet end of the heat transfer tube, and the protrusion length L is 1/10D to 1D relative to the heat transfer tube diameter D. An overheat prevention device at a gas inlet end of a heat transfer tube, characterized in that: