JPS624596B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applicable to, for example, a junction between a coolant purification system (hereinafter simply referred to as CUW system) piping and a water supply system (hereinafter simply referred to as FOW) piping in a nuclear reactor, or a recirculation system. (hereinafter simply referred to as PLR system)
The present invention relates to a pipe joint used at a junction between a pipe and a CUW system pipe, and more particularly to a pipe joint that can effectively prevent thermal fatigue caused by temperature fluctuations of merging fluids.

Conventionally, the one shown in Figure 1 is known as CUW system equipment for nuclear reactors. That is, reactor pressure vessel 1
CUW system piping 2, FDW system piping 3, PLR system piping 4, etc., including a cooler and demineralizer, are connected to the pipe. In this, the internal fluid temperature of the FDW system piping 3 is approximately 230°C, and the internal fluid temperature of the CUW system piping 2 is approximately 190°C, and the temperature difference between the two is approximately 40°C. During normal operation, fluids having such a temperature difference continuously merge at the pipe joint 5 of the FDW system and the CUW system, so that the pipe joint 5 was susceptible to thermal fatigue.

By the way, thermal fatigue generally occurs as a result of a temperature distribution occurring on the cross section when the surface temperature of a certain member changes rapidly, and stress is generated on the cross section due to the difference in thermal expansion of each part. . The magnitude of this stress is caused by heating or cooling rates, material conductivity, specific heat, specific volume, geometry, elastic limits, etc.

Therefore, the basic methods that can be considered to prevent thermal fatigue are: (1) Select a material with high thermal conductivity, high ductility, and a high fatigue limit in order to absorb thermal stress through material deformation.

(2) Minimize the temperature difference between the merging fluids as much as possible.

(3) Ensure operating conditions that keep the number of thermal cycles as low as possible.

(4) In the structure of the confluence section, heat conduction between the two fluids can be carried out smoothly, and temperature fluctuations occurring on the inner wall of the pipe can be kept to a minimum.

As for the material in (1), there are currently no particularly advantageous and economical materials that are used industrially, and this is not a realistic countermeasure. Measures for (2) are also
This is not realistic as it would require major system changes and reduce the thermal efficiency of the entire plant. Also, (3)
Managing the operating conditions of a power plant may seem effective at first glance, but it may not be possible to predict future operating conditions, there are many uncertainties, and it is not practical in terms of ensuring a stable supply of electricity. Not the point. Therefore, the structural measure (4) is considered to be the most realistic, effective, and immediate.

For this reason, various piping joints for preventing thermal fatigue have been considered in the past for use at junctions of high and low temperature fluids. For example, as shown in FIG. 2, a constriction part 13 for restricting the flow rate of the main pipe 11 is provided at the confluence of the main pipe 11, which is one of the inflow pipes, and the branch pipe 12, which is the other,
By causing an increase in the speed of the fluid due to an increase in pressure when the fluid passes through the constriction part 3, the branch pipe 1
This prevents the fluid flowing in from 2 from coming into direct contact with the pipe wall at the branch corner.

However, in this case, even if the speed of the fluid in the main pipe 11 is increased, high-temperature and low-temperature fluids alternately collide with the branch corner 14 between the branch pipe 12 and the main pipe 11 based on flow rate fluctuations, etc. This condition cannot be avoided, and the possibility of localized thermal fatigue remains. In addition, the average flow velocity in the pipe is normally set to about 4 to 5 m/s from the viewpoint of preventing fluid vibration and corrosion progression, and in order to increase this speed with the throttle part 13, the cross-sectional area in the pipe must be drastically reduced. In this case, for an average flow velocity of 4 m/s, to double the pressure, approximately 3 Kg/cm ² g, and 3
Doubling the speed would result in a pressure loss of 8 kg/cm ² g, which would lead to an increase in the size of the pump, and it is unclear how high the speed should actually be to achieve its function.

In contrast, as shown in a part of FIG. 2 or in FIG.
There is also a means to provide 16. That is, small-diameter thermal sleeves 15 and 16 are formed coaxially with the main pipe 11 or the branch pipes 12, thereby preventing the high-temperature fluid and the low-temperature fluid from violently colliding directly with the inner surface of the branch corner portion 14. The structure is designed to prevent this.
However, in this case, the flow of both fluids is obstructed by the thermal sleeves 15 and 16, and the flow inside the pipe becomes a complicated vortex, which reliably prevents fluids with a temperature difference from colliding with the branch corner 14. It is difficult to do so, and it is not possible to reliably prevent thermal fatigue of the tube.

In addition, at junctions such as T-joints and Y-joints, the flow usually collides in a turbulent state and is violently stirred, and the flow is complex, causing high-cycle temperature fluctuations of about 0.1 to 1 Hz on the pipe wall. There is a concern that high cycle thermal fatigue may occur. Also, the branch corner part is exactly
It is a place where stress concentration is high, and the thermal stress reaches several times that of other parts, and it is also the boundary where low-temperature fluid and high-temperature fluid meet, so there is a concern that thermal fatigue will occur under extremely severe conditions. Ru.

The present invention was developed in view of the above circumstances, and is capable of suppressing subtle temperature fluctuations that occur at the confluence of fluids with different temperatures to the lowest possible level, thereby reducing the causes of thermal fatigue at the confluence of both fluids. The purpose is to provide piping joints that can make a significant contribution.

The piping joint of the present invention is a piping joint for merging fluids that causes temperature changes, which is composed of a branch pipe part and a main pipe part. (b) a rectifying tube having a small diameter, a closed tip, and protruding coaxially into the main pipe; A plurality of rectifying holes are opened along the axial direction of the pipe section, are formed in at least half of the downstream side, and have a total cross-sectional area equivalent to the cross-sectional area of the branch pipe section. ,(c)
A rectifying plate having a plurality of rectifying holes is provided on the upstream side of the main pipe, and (d) a thermal sleeve is provided at the branch corner of both the inflow pipe and the main pipe.

In a preferred embodiment of the present invention, the distal end of the rectifying cylinder is integrally formed with the other inflow pipe part, and the base end whose diameter is gradually enlarged is slidable on a tapered part formed on the inner surface of one inflow pipe part. It is assumed that it came into contact with.

Further, one inflow pipe section integrally includes a thermal sleeve whose one end is located upstream of the rectifying tube and downstream of the branch corner section.

Further, the other inflow pipe portion integrally includes a thermal sleeve whose one end is located upstream of the flow straightening hole of the flow straightening tube and located downstream of the branch corner portion. Furthermore, at least one of the inflow pipes is integrally provided with a flow regulating hole having a plurality of flow regulating holes having different hole diameters in the pipe radial direction on the upstream side of the branch corner portion.

An embodiment of the present invention will be described below with reference to FIG.

In the figure, 21 is one side of the inflow pipe section, that is, a branch pipe, 22 is the other side of the inflow pipe section, that is, the main pipe, and 23 is the outflow pipe section. At the branch corner of this piping joint,
A rectifier tube 24 having a smaller diameter and having a closed tip protrudes coaxially from the branch tube 21. The distal end of the rectifying pipe 24 is integrally formed with the main pipe 22, and the proximal end 25 whose diameter is gradually expanded is slidably abutted on a tapered portion 26 formed on the inner surface of the branch pipe 21. Further, a plurality of rectifying holes 27 communicating with the outflow pipe portion 23 are bored in the peripheral wall of the rectifying pipe 24 so that the total cross-sectional area of the holes is equal to the cross-sectional area of the branch pipe 21 . The flow straightening hole 27 is shaped to open along the axial direction of the outflow pipe portion 23, and is opened approximately half way on the downstream side.

Further, the main pipe 22 integrally includes a thermal sleeve 29 whose one end is located upstream of the rectifying cylinder 24 and downstream of the branch corner portion 28 .

Further, the branch pipe 21 integrally includes a different thermal sleeve 30, one end of which is located upstream of the flow straightening hole 27 of the flow straightening cylinder 24 and downstream of the branch corner portion 28.

Furthermore, the main pipe 22 integrally has a current plate 31 on the upstream side of the branch corner portion 28. This rectifying plate 31 has a plurality of rectifying holes 32 having different hole diameters in the radial direction of the main pipe 22. Note that the rectifying hole 32 has a larger diameter on the center side of the main pipe 22 than on the outer peripheral side. The opening area ratio of the rectifying hole 32 to the main pipe 22 is preferably 0.466, for example, when the Raynozzle number (Re) is about 10 ⁶ .

With such a configuration, the branch pipe 21 and the main pipe 2
When two fluids having different temperatures are allowed to flow into the pipe 2 and join together, pipe wall fatigue can be prevented by the following action. That is, the fluid flowing in from the main pipe 22 (in the flow direction F) has a shape with a good flow rate distribution, as shown by the imaginary line A in FIG. Fluid flows to the branch corner portion 28 through a thermal sleeve 29 provided on the main pipe 22 in a non-contact manner.

On the other hand, fluid flowing into the branch pipe 21 (inflow direction f)
The water passes from the rectifier tube 24 to the outflow pipe section 23 side through the rectifier hole 27 with a good flow rate distribution as shown by the imaginary line B. The fluid flowing from this rectifying hole 27 is
The branch pipe 21 is prevented from contacting the branch corner portion 28 by the thermal sleeve 30 .

Therefore, when the fluid flowing from the main pipe 22 and the branch pipe 21 passes through the branch corner part 28, the fluid flows through the outflow pipe with a good flow distribution shape as shown by the imaginary line C in FIG. The liquid will flow out to the section 23. That is, both the fluid flowing in from the main pipe 22 and the fluid flowing in from the branch pipe 21,
Since they merge in a good flow rate distribution shape as shown by A and B, the flow rate distribution shape in the outflow pipe section 23 as a sum of them also has good characteristics as shown in C.

Therefore, according to this embodiment, the merged fluids with different temperatures flow out with a good flow distribution shape, so that the flow rate of each inflow fluid changes due to the occurrence of polar vortices, etc., resulting in an unmixed state. There is no risk of the mixture coming into contact with the branch corner 28, and the mixture is well mixed and flows through the tube with an average temperature distribution. Therefore, there is no risk of temperature change occurring in the branch corner portion or the side surface portion 28A opposite thereto, which is effective in eliminating the risk of generating excessive thermal stress in this portion and suppressing fatigue. .

Note that, as in the embodiment described above, the tip of the rectifying tube 24 is integrally formed with the main pipe 22, and the proximal end 25 whose diameter is gradually expanded is slidably abutted on the tapered part 26 formed on the inner surface of the branch pipe 21. If this is done, the fluid flowing in from the main pipe 22 will pass through the tip of the integral connection structure of the rectifying cylinder 24 to the main pipe 22.
can be held in a fixed state without the risk of vibration. In addition, the rectifying cylinder 24 is caused by the fluid flowing in from the branch pipe 21.
Fluid pressure applied to the straightening tube 24 applies a pressing force in the outer circumferential direction to the base end 25 of the rectifying cylinder 24, but since the base end 25 is in contact with the tapered portion 26, it is in a pressed and fixed state, and vibrations etc. There is no risk of this occurring. Note that if the base end 25 of the rectifying cylinder 24 is configured to abut against the tapered part 26 of the branch pipe 21, even if the rectifying cylinder 24 thermally expands due to temperature changes, the abutment position will be automatically adjusted and the heat will be removed. Stress generation can be reliably prevented.

Further, as in the embodiment described above, the flow straightening hole 27 of the flow straightening cylinder 24 is shaped along the axial direction of the outflow pipe portion 23,
If it is opened at least half way on the downstream side, the two fluids will flow in along the axial direction of the outflow pipe section 23 and mix, so that the generation of vortices can be more reliably prevented.

In addition, as in the above embodiment, the thermal sleeve 2
9 and 30 on each inflow pipe section 21 and 22 to prevent the fluid from coming into direct contact with the branch corner section 28.
This makes it possible to more reliably prevent the temperature change described in No. 8.

Furthermore, if the main pipe 22 is provided with the rectifying plates 31 having the rectifying holes 32 of different diameters as in the embodiment described above, the flow rate distribution shape of the inflowing fluid can be made good in advance (see virtual line A), and the rectifying effect can be improved. becomes more certain. Although not shown, the current plate 31 may be provided on the branch pipe 21.

In the above embodiment, the rectifying tube 24 is arranged along the axis of the branch pipe 21, but the rectifying tube 24 does not necessarily have to be arranged in this way. The same effect can be achieved as well.

As described above, the present invention protrudes coaxially from one side of the inflow pipe at the branch corner of the inflow pipe with a rectifying cylinder having a smaller diameter and a closed end, and the outflow pipe is attached to the peripheral wall of the rectifying cylinder. Multiple rectifying holes communicating with the pipe are drilled so that the total cross-sectional area of the holes is equal to the cross-sectional area of the inflow pipe, which reliably prevents the generation of a large amount of unmixed vortex fluid at the branch corner. Therefore, when fluids with different mixing ratios are combined, it is possible to prevent the risk of fatigue caused by thermal stress due to temperature changes at the branch corner, for example, in the coolant purification system of a nuclear reactor. It is effective not only for the equipment but also for various other piping equipment, and the reliability of the pipe line configuration can be improved.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an example of a piping system incorporating a piping joint, Figs. 2 and 3 are partial sectional views showing the configuration of a conventional piping joint, and Fig. 4 is a part showing an embodiment of the present invention. FIG. 21... One side of the inflow pipe section (branch pipe), 22... The other side of the inflow pipe section (main pipe), 23... Outflow pipe section, 24
... rectifying cylinder, 25 ... base end of rectifying cylinder, 26 ... taper part, 27 ... rectifying hole, 28 ... branching corner part, 29, 30 ... thermal sleeve, 31 ...
Rectifying plate, 32... Rectifying hole.

Claims (1)

[Claims] 1. In a piping joint for merging fluids that causes temperature changes, which consists of a branch pipe section and a main pipe section, (a) a pipe with a diameter smaller than this from one of the branch pipe sections to the branch corner section of the branch pipe section, and A rectifying tube whose tip end is closed and protrudes coaxially into the main pipe, and
(b) communicating with the outflow pipe section on the peripheral wall of the straightening tube;
and is opened along the axial direction of the outflow pipe portion and is formed in at least a half of the downstream side,
Further, a plurality of rectifying holes having a total hole cross-sectional area equivalent to the cross-sectional area of the branch pipe portion are bored, (c) a rectifying plate having a plurality of rectifying holes is provided on the upstream side of the main pipe, and ( d)
A piping joint characterized in that thermal sleeves are provided at branch corners of both the inflow pipe and the main pipe.