JPS6133348Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a pipe joint structure, and particularly to a pipe joint structure suitable for preventing thermal fatigue in the thick wall portion of a pipe joint used under high temperature and high pressure. .

In the past, once a boiler started operating, it operated steadily for a considerable period of time under the same operating conditions. Therefore, fatigue analysis due to thermal fatigue has not been considered a problem even when pipe joints with thick-walled parts are used in boiler plant piping.

However, in recent years, boiler plants have increasingly been operated on a daily or weekly basis with overnight or weekend shutdowns due to power supply conditions, and as a result, the number of repeated temperature increases and decreases has increased. Under such conditions, the temperature difference between the inner and outer surfaces of the thick walled portion of the pipe joint becomes large when the temperature changes, and considerable thermal stress is generated. As a result of repeated occurrence of this thermal stress, fatigue failure occurs.

An object of the present invention is to provide a pipe joint structure that can prevent destruction due to thermal fatigue in environments where the pipe joint is used at high temperatures and high pressures and undergoes large thermal changes.

The present invention provides a pipe joint that connects a main pipe and a branch pipe and has a thick wall portion, and a hole is provided in the thick wall portion to allow fluid to flow from one pipe side to the other pipe side. The temperature difference (ΔT) between the inner and outer surfaces of the thick portion is made as small as possible.

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

Figures 1 to 3 show an embodiment of the present invention, showing a T-block pipe joint 1 and a main pipe 2.
It consists of pipes A, 2B, and a branch pipe 3. As shown in FIG. 2, the pipe joint 1 has a shape having thick portions 1A and 1B on the axial side of the main pipes 2A and 2B. This thick wall portion 1A is provided with three holes 4 having one end opening on the main pipe 2A side and the other opening on the branch pipe 3 side, and the thick wall portion 1B has one end opening on the main pipe 2B side. Three holes 4 are provided, each having an opening and the other opening on the branch pipe 3 side.

These holes 4 are formed in advance by drilling holes in the pipe joint 1 which is not connected to the main pipes 2A, 2B and the branch pipe 3 using a drill or the like. Furthermore, by forming the holes 4 in the thick parts 1A and 1B, the strength of the thick parts 1A and 1B themselves becomes slightly lower than when the holes 4 are not provided, so there is no margin in the strength of the thick parts. If not, the thickness of the thick part (indicated by t in FIG. 2) needs to be made slightly larger than the normal thickness by providing the hole 4. The main pipes 2A, 2B and the branch pipes 3 are connected to the pipe joint 1 in which the predetermined holes 4 are formed in this way.
are joined by welding.

In the pipe joint structure as described above, the branch pipe 3
The flow path cross-sectional area of main pipe 2A and main pipe 2B is
Since it is smaller than the total cross-sectional area of the flow passages, when fluid such as steam flows in the direction shown by the arrow in the figure in the main pipes 2A and 2B, the flow velocity in the branch pipe 3 is equal to the flow rate in the main pipes 2A and 2B. faster than the road. Therefore, the fluid in the main pipes 2A, 2B flows through the hole 4 toward the branch pipe 3 due to the dynamic pressure. Therefore, the thick portion 1 is caused by the fluid flowing through the hole 4.
Heat transfer between A and 1B is performed efficiently. Therefore, the temperature difference between the inner and outer surfaces of the thick portions 1A and 1B is reduced, and thermal stress is reduced, so that fatigue failure due to repeated thermal stress can be prevented.

In order to prevent fatigue failure due to thermal stress as described above, it is necessary that fluid flows through the holes provided in the thick portion due to dynamic pressure. Therefore, in the present invention, the pipe joint itself is not limited to a T-type pipe joint, but may be a three-way pipe joint of other shapes. In either case, it is necessary that the cross-sectional area of the pipe on the side through which the fluid flows from the pipe joint is smaller than the cross-sectional area of the pipe on the side through which the fluid is introduced into the pipe joint. Further, the shape, number, diameter, etc. of the holes formed in the thick portion can be appropriately selected in consideration of the strength of the thick portion, heat transfer by the fluid flowing through the holes, and the like.

As described above, according to the present invention, heat is transferred by the fluid flowing through the hole formed in the thick wall part of the pipe joint, so the temperature difference between the inner and outer surfaces of the thick wall part of the pipe joint is reduced. As expected, fatigue failure of pipe joints due to thermal stress can be prevented. Therefore, in order to prevent fatigue failure of pipe joints due to thermal stress, there is no need to create complicated and expensive pipe designs to avoid the use of pipe joints with thick wall parts, and instead of using conventional pipe joints with thick wall parts. The joint can be used as is.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of the present invention, FIG. 2 is a longitudinal sectional view of FIG. 1, and FIG. 3 is a sectional view taken along line A-A' of FIG. 2. 1...Pipe fitting, 2A, 2B...Main pipe, 3...
...branch pipe, 4...hole.

Claims (1)

[Claims for Utility Model Registration] (1) In a pipe joint that connects a main pipe and a branch pipe and has a thick wall portion, fluid is allowed to flow from one pipe side to the other pipe side within the thick wall portion. A pipe joint structure characterized by having holes for circulation. (2) The pipe joint structure according to claim 1, wherein the pipe joint is a three-way joint. (3) The pipe joint structure according to claim 2, wherein the three-way pipe joint is a T-shaped pipe joint.