JPS6199794A - Piping joint device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention provides a method for connecting a boiler water supply pipe at a heater outlet and a bypass pipe that bypasses a heater in a plant such as a stage end of thermal power and nuclear power generation or chemical equipment. This is an example. The conventional type of such piping joint device is the 6th one.
This will be explained with reference to FIGS. 8 to 8.

FIG. 6 shows a plant having two series and three stages of heaters and a series heater bypass system, where the water supply pump discharge pipe 1 branches into two water supply pipes 2A, 2B and a bypass pipe 3.
Each water supply pipe 2A, 2B has three heaters 5A, 6A between the large mouth valves 4A, 4B and outlet valves 8A, 8B, respectively.
7A:5[3°6B and 7B are interposed in series. Moreover, the self-supply water pipes 2A and 2B join together on the downstream side of the outlet valves 8A and 8B to form a water supply main pipe 9. A bypass valve 10 is interposed in the bypass pipe 3, and the bypass pipe 3 intersects the water supply main pipe 9 at right angles, as shown in FIGS. 7 and 8.

According to such a configuration, during rated operation, the boiler water supply is
The water is supplied from the water supply pump discharge pipe 1 to each of the water supply pipes 2A and 2B at a ratio of 50%, and the water is supplied to the first heater 5A.
, 5B, second heater 6A.

6B and third heaters 7A and 7B, respectively,
They are combined and transferred to a boiler (not shown) by the main pipe 9. In this state, since the bypass valve 10 connected to the bypass pipe 3 is closed, there is no confluence of fluids with a problematic temperature difference.

Here, for example, the heater 5B of the water supply pipe 2B.

If a failure such as tube breakage occurs in either of 6B and 7B, the large mouth valve 4B and outlet valve 8B are closed to shut off the water supply pipe 2B, and the bypass valve 1011 is closed.
In this heater bypass operation, the feed water passing through the bypass pipe 3 flows into the boiler without being heated, and the temperature of the feed water drops by that amount, causing the turbine In some cases, it may be necessary to limit the load on the system. Therefore, in order to raise the temperature of the water supply as much as possible, 75% of the total amount of water is supplied to the water supply pipe 2A side.
It is common practice to allow 25% of the water supply to flow through the bypass pipe 3 side. In this case, the water that has flowed into the water supply pipe 2A passes through the inlet valve 4A, is heated by the first heater 5A, the second heater 6A, and the third heater 7A, and then flows into the main pipe 9. On the other hand, the feed water flowing through the bypass pipe 3 is not heated as it is, and the bypass valve 10 reduces the flow rate to 25
%, it flows into the main pipe 9. Here, a fluid confluence section (pipe joint device) with a problematic temperature difference occurs. As shown in FIG. 7, when the flow rate of the low-temperature fluid a is faster than the flow rate of the high-temperature fluid in the main pipe 9, the flow of the fluid at this confluence part is reversed while impeding the flow of the high-temperature fluid. It collides with the inner circumferential surface, goes around the inner circumferential surface on the near side (165 times to 2 times the inner diameter of the main pipe 9 from the confluence part)
．． 0x position). On the other hand, the flow of high-temperature fluid 1 repeatedly collides with low-temperature fluid a at the same position.
The heated fluid and the low-temperature fluid a, that is, the fluid that passes through the bypass pipe 3 without being heated, do not mix quickly, creating a turbulent flow while generating vortices, resulting in a turbulent flow during normal operation. The warmed main pipe 9 is rapidly cooled by the inflow of the low-temperature fluid a from the bypass pipe 3, and the unmixed fluid with this temperature difference flows into the main pipe 9.
By contacting the inner circumferential surface of the main tube 9, the metal temperature of the inner circumferential surface of the main tube 9 changes repeatedly from high temperature to low temperature and from low temperature to high temperature. It is known that this phenomenon causes thermal stress to act on the inner circumferential surface of the main tube 9, causing thermal fatigue cracks to occur in terms of RH. This has been confirmed through experiments, and the main tube 9
The position where this change is drastic changes depending on the number of Ray nozzles of the inner flow and the flow of the bypass pipe 3 on the side of the branch pipe. In the experiment, the positions X where the metal temperature changes are concentrated in a range of about 1.5 to 2.0 times the inner diameter of the main pipe from the confluence part to the downstream side of the water supply main pipe 9.

Traditionally, plants were evaluated through experiments like this! However, this is a very difficult analysis, and it is economically impossible to create and experiment with the same model plant as the actual plant each time, so the results of other experiments cannot be used to compare the state of the plant. Since it is corrected to suit the situation, it is inevitable that it will deviate from the actual situation. Other methods include attaching thermal sleeves to high-risk areas to protect the inner peripheral surface of the pipe, but this method requires a complicated structure and requires a lot of man-hours, making it expensive. There was a drawback.

[Purpose of the invention]

In view of these points, an object of the present invention is to provide a highly safe piping joint device that can reliably prevent thermal fatigue cracks with a simple structure.

(Summary of the Invention) The present invention provides a pipe joint device for merging high-temperature fluid and low-temperature fluid, in which a branch pipe that intersects at an acute angle with the flow direction of the fluid in the main pipe and supplies one of the fluids is arranged in a substantially tangential direction of the main pipe. It is characterized in that a small-diameter merging pipe for supplying the other fluid is inserted into the center of the main pipe close to the merging position.

[Embodiments of the invention]

The present invention will be explained below with reference to embodiments shown in the drawings.

1 to 3 show a first embodiment of the present invention, in which a branch pipe 11 is connected to the outer periphery of a main pipe 9 by welding. The connecting direction of the branch pipe 11 to the main pipe 9 intersects with the flow direction of the fluid in the main pipe 9 at an acute angle θ, and the fluid supplied from the branch pipe 11 into the main pipe 9 is It is located approximately in one direction along the length F of the main pipe 9 so that the fluid flows spirally within the main pipe 9. In addition, branch pipe 11
An opening 12 that matches the inner diameter of the branch pipe 11 is formed on the circumferential surface of the main pipe 9 inside the connecting portion.
The axis of the branch pipe 11 coincides with the axis of the branch pipe 11.

Furthermore, the inner circumferential surface of the opening 12 on the center side of the main pipe 9 is provided with a tapered longitudinal section for deflecting the flow in the branch pipe 11 corresponding to the center side of the main pipe 9 in the circumferential direction of the main pipe 9. shaped protrusion 13
is protrudingly provided in a planar arc shape, and the welding part continuous to this protrusion 13 is also formed in a j-pa shape and an arc shape so as to follow the protrusion 13.

On the other hand, the main pipe 9 has an end wall 14 that is closed upstream of the joining position with the branch pipe 11.
A center hole 15 is formed in the center hole 15, and from this center hole 15, a bypass pipe 3, which is a confluence pipe that supplies fluid into the mother @9, is connected.
is coaxially inserted into the main pipe 9, and is attached to the main pipe 9 by welding.
He has finished 2i1.

The outer diameter of the bypass pipe 3 is much smaller than the inner diameter of the main pipe 9, and the tip of the bypass pipe 3 reaches near the merging position.

In this embodiment, in particular, the branch pipe 11 supplies high-temperature fluid 11, and the bypass pipe 3 supplies low-temperature fluid a. This is because the temperature inside the main pipe 9 is raised to a high temperature by high-temperature fluid during normal operation.
Even during bypass operation, high-temperature fluid is supplied from the branch pipe 11 to protect the inner peripheral surface of the main pipe 9 from rapid cooling.

Next, the operation of the embodiment described above will be explained.

When the high-temperature fluid from the branch pipe 11 flows into the main pipe 9, it gathers near the inner peripheral surface of the main pipe 9 due to the protrusion 13 of the main pipe 9 and flows in a spiral shape, and this flow is directed to the main pipe 9 by the centrifugal horn. A high fp2 fluid layer is formed on the inner peripheral surface of the tube.

On the other hand, the bypass pipe 3, which is a merging pipe, is inserted and fixed coaxially into the main pipe 9 up to the point where it joins the branch pipe 11, so that the flow of the low-temperature fluid a has no noise. It forms and flows into the main pipe 9 of large cross section.

However, this will not be the generally known rapid expansion trend. This is because a cylindrical layer is formed near the inner circumferential surface of the main pipe 9 by the high-temperature fluids under the same pressure state, and no pressure drop occurs when the low-temperature fluid a flows into the main pipe 9. The low-temperature fluid a does not have a rapid flow velocity drop, and the main pipe 9
Flows straight through the center of the axis.

Conventionally, at this junction, the high-temperature fluid and the low-temperature fluid alternately contact the inner circumferential surface of the main pipe 9, causing damage because the high-temperature fluid and low-temperature fluid do not mix completely, leading to thermal fatigue cracks. However, according to this embodiment, in the vicinity of this confluence, the four fluids such as ``B'' and ``B'' are completely separated, and the high-temperature fluid is The centrifugal force of the fluid forms a cylindrical layer of eight immersed bodies near the inner circumferential surface of the main tube 9, so that the low-temperature fluid a flows onto the inner circumferential surface of the main tube 9. There is no contact. In other words, the inner peripheral surface of the main tube 9 is protected by the high temperature fluid. On the downstream side, the low-temperature fluid a will eventually come into contact with the main pipe 9, but due to the presence of high-temperature fluid around the fluid, it will gradually warm up as it flows.
When the low-temperature fluid comes into contact with the main pipe 9, the low-temperature fluid a is no longer one that would give a thermal shock to the main pipe 9. Furthermore, the cylindrical gap 16 between the main pipe 9 and the bypass pipe 3 is filled with high-temperature fluid during normal operation, and even when the low-temperature fluid a flows in from the bypass pipe 3, the inserted bypass pipe 3 It is maintained by itself and does not come into direct contact with the main tube 9, and no flow wraparound occurs because the n-shaped gap 16 is filled with a high 4 fluid bs.

As described above, in this embodiment, the high-temperature fluid is flowed in from the branch pipe 11 and used as a protective fluid because the fluid during normal operation of this line is a high-temperature fluid and the metal temperature of the main pipe 9 is 8-8. This is because it is heated by Even if the bypass operation is shifted to 1) in this state, the metal temperature of the main tube 9 will hardly change if configured as in this embodiment. Therefore, thermal stress due to fluid temperature difference does not occur in the main pipe 9 of the confluence section, which is this pipe joint device, and the occurrence of thermal fatigue cracks can be completely prevented. In addition, in carrying out the present invention, g
19. It is necessary to provide a certain degree of straight pipe section as the shape of the downstream piping of this piping joint device so as not to disturb the flow described above.

4 and 5 show a second embodiment of the invention 'II'
b, and as described in FIG. 6, it has the configuration of the conventional example, and the two water supply pipes 2A, 2 [3 and the bypass pipe 3 are joined at the same place, and the re-water supply pipes 2A, 2B are It is connected to the main pipe 9 in exactly the same way as the branch pipe 11 in the embodiment of FIGS. 1 to 3. In addition, re-water supply pipe 2A,
2B are fixed at positions symmetrical with respect to the center of the main pipe 9.

On the other hand, the connection configuration of the bypass pipe 3 to the main pipe 9 is also the same as in the first embodiment.

According to the above-described configuration, during operation, the supply water passes through each heater and is heated, and 44 fluids flow in from the re-supply pipe 2A and the water supply pipe 2b, and after merging, the fluid spirals in the nearby main pipe 9. The water gradually flows in a straight line along the main pipe 9 and flows to the boiler.

In this state, there is no flow from the bypass pipe 3, so the main pipe 9 is filled with high-temperature fluid.

Furthermore, a high-temperature fluid is also applied to the annular gap 16 of the main pipe 9 and the bypass @3m, and the temperature of the inner peripheral surface of the fIi pipe 9 is raised to a high temperature by the high-temperature fluid.

Next, when the flow of water supply pipe 2A or 2B in one row is cut off in order to shift to bypass operation, the low temperature fluid a flows from the bypass pipe 3 to the main pipe 9, but the flow of high temperature fluid No matter which water supply pipe 2 is cut off, the flow will be in a spiral shape similar to that during normal operation, and a layer will be formed near the inner circumferential surface of the main pipe 9 due to centrifugal force, and the low-temperature fluid a will flow from the main pipe 9. This will protect the inner peripheral surface of the tube 9. This state corresponds to the flow at j'3 in the embodiments of FIGS. 1 to 3 described above. Furthermore, in the annular gap 16 formed by the main pipe 9 and the bypass pipe 3 inserted into the main pipe 9,
The 4'12 R body 16 is filled and prevents the bypass pipe 3 from coming into contact with the inner circumferential surface of the main pipe 9 by going around from the outflow part.

In addition, in this second embodiment, there are two water supplies of 1!2A.

2B is connected to the main pipe 9, but three or more water supply pipes may be connected. Furthermore, the connection method is not limited to the illustrated welding, but may also be cast or forged.

(Effects of the Invention) As explained above, the pipe joint device according to the present invention is a pipe joint device that joins a high temperature fluid and a low 6A fluid.
A branch pipe that intersects at an acute angle to the flow direction of the fluid in the main pipe and supplies one fluid is connected almost tangentially to the main pipe, and a small-diameter merging pipe that supplies the other fluid is connected to the center of the main pipe. Since it is inserted near the confluence position, one fluid forms a spiral near the inner peripheral surface of the main tube to protect the inner peripheral surface of the main tube from the other fluid with a different temperature. can,
Thermal fatigue I (I cracks) can be prevented from occurring on the inner circumferential surface of the main pipe downstream of the merging part, allowing safe operation.

[Brief explanation of the drawing]

FIG. 1 is a wIIgi plane view showing the first embodiment of the piping joint device according to the present invention, FIG. 2 is a sectional view of a corresponding portion taken along line II-I in FIG. 1, and FIG. 4 is a longitudinal sectional view showing the second embodiment of the present invention, and FIG. Figure 7 is an enlarged sectional view taken along the line ■ in Figure 6, and Figure 8 is a cross section of a corresponding portion taken along the line ■-■ in Figure 7. It is a diagram. 2A, 2B... Water supply pipe, 3... Bypass pipe, 5, 6
゜7... Heater, 9... Main pipe, 11... Branch pipe, 1
3... Protrusion, 16... Annular gap, a... Low temperature fluid, b... High temperature fluid.

Claims (1)

[Scope of Claims] 1. In a piping joint device for merging high-temperature fluid and low-temperature fluid, a branch pipe that intersects at an acute angle with the flow direction of the fluid in the main pipe and supplies one of the fluids is arranged approximately tangentially to the main pipe. A piping joint device characterized in that a small-diameter merging pipe for supplying the other fluid is inserted into the center of the main pipe to the vicinity of the merging position. 2. The piping according to claim 1, wherein the main pipe at the connecting portion of the branch pipe is provided with an arc-shaped projection for deflecting the fluid in the branch pipe in the circumferential direction of the main pipe. fitting device.