JPS61211589A - Expansion pipe joint - 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] [Field of application of the invention] The present invention relates to an expansion pipe joint.

[Background of the invention]

Bellows type expansion joints are used in chemical plants with high temperature structures,
Often used in blast furnaces, etc., 8=l! A fast breeder reactor that uses liquid metal sodium as a coolant is a system that requires structural integrity (reliability). In FIG. 4, liquid metal sodium that has received heat generated in the reactor core LO enters an intermediate heat converter IT having a heat exchanger tube therein as feed sodium. The primary sodium that has entered the middle heat exchanger 11 gives the heat received from the core 10 to the secondary sodium and returns to the intermediate heat exchanger L11.
Exit and return to core 10 again.

The secondary sodium flowing inside the intermediate heat exchanger 11 receives heat from the primary sodium and enters the superheater 12. The secondary sodium entering from the superheater L2 enters the evaporator 13 from the 9-sodium outlet provided at the bottom, and returns to the intermediate heat exchanger 11 again from the evaporator outlet provided at the bottom.

The evaporator 13 and superheater 12 have heat transfer tubes 14 inside. Water or steam flows through this heat transfer f14, and the heat held by the secondary sodium is given to the water or steam through the tube wall.

Here, water is supplied to the heat exchanger tube 14 in the evaporator L3 from the water supply tube L5, which receives heat from the secondary water flowing outside the heat exchanger tube 14 and becomes high-temperature steam.

Since this steam is insufficient in both temperature and freshness, it flows through the heat transfer tube 14 in the superheater L2, becomes superheated steam at a sufficient temperature, and is sent to the high-pressure turbine to drive the turbine.

The high temperature section of a fast breeder reactor having the above-mentioned cooling system is normally operated at about 470C to 530C, and the low temperature section is about 350C to 400C. Austenitic stainless steel is usually used as the structural material for fast breeder reactors due to its compatibility with sodium, but creep characteristics at high temperatures must be considered in strength design. For the structural design of equipment that is used at room temperature, limit creep strain, consider the superimposition of damage due to fatigue and creep, etc.
J-P buckling prevention etc. are added. The conventional structural design standard for room temperature is to set the height, pitch, and plate thickness of the expandable pipe, give pressure and displacement conditions, calculate the generated stress using a simple formula, and examine the fatigue life. It is possible to examine whether the shape is appropriate for the conditions. Regarding the high temperature range, the fc structure design criteria considering the effect of creep mentioned above is in the ASME Code (::ase N-290 standard). It requires a detailed structural analysis using the method and satisfaction of each stress limit and strain limit.

Furthermore, regarding the dimensional tolerance of the bellows, the height of the peak or valley, the wall thickness at the peak, the wall thickness at the bottom of the valley, the length of the peak or valley, the inner diameter of the end of the short pipe at the end, the outer diameter of the peak or valley, Detailed standards are provided for the basic dimensional tolerance 2 and regularity for the width of the crest, the width of the valley, and the length of the short end pipe, respectively.

By the way, in a controlled breeder reactor having a cooling system as mentioned above, one of the important safety issues is that the evaporator 1
The leakage of water in step 3 and the pressure propagation phenomenon caused by the subsequent sodium-water reaction can be mentioned. When the heat exchanger tube 14 in the evaporator 13 breaks and water or steam is spouted into the sodium, the reaction between the sodium and water produces water, sodium oxide, and sodium hydroxide. For example, the amount of water that flows out when a single heat exchanger tube completely ruptures is not more than 20~/a during rated operation, and the severe pressure generated by the reaction is several liters/a.
d It becomes more than g. This pressure rise rises with breath as shown in the graph in Figure 5, and this rise rises by several millimeters (8
) occurs in a very short period of time. This shock pressure wave reaches the intermediate heat exchanger 11 constituting the secondary cooling system and the bellows-type expansion pipe joint 9 in the middle of the piping through which the liquid metal sodium passes.

- 10,000, In the external pressure type piping bellows installed in the secondary cooling system, the above-mentioned ASME Code Ca5e N-
When manufactured according to the dimensional tolerance standard of No. 290, the collapse pressure due to external pressure is smaller than the impact pressure during reaction, as shown in FIG.

From the above, when the conventional type bellows 9 shown in Fig. 3 is used in the secondary cooling system of a fast breeder reactor, it buckles and collapses due to the impact and pressure waves caused by the sodium-water reaction accident in the evaporator 13. there is a possibility. Therefore, a structure is required in which the impact pressure generated within the evaporator 13 is not applied to the external pressure type bellows 9 installed in the secondary cooling system piping.

The structure of a conventional bellows-type expansion pipe joint 9 is as shown in FIG.

That is, among the piping 3.4, the end of the piping 3 is included inside the other piping 4 as an IJ-pro. The end portion of the pipe 4 has a swollen shape to form a bellows chamber 7, and the end thereof slidably contacts the pipe 3 via a sliding seal 4a. A bellows L is installed between the middle of the sleeve 6 and the fc valley short pipe 2 provided on the end side of the pipe 4. With such a structure, it is natural that the pipes 3 and 4 will slide against each other due to thermal expansion, but the shock pressure wave that propagates inside the pipes 3 and 4 will enter the bellows chamber 7. This causes an accident of buckling and collapsing. Furthermore, if there is a joint without bellows l, excessive pressure will be directly applied to the seal 4a, which is dangerous. In any case, piping 4 and sleep 6
It is necessary to prevent impact pressure from entering between the

[Purpose of the invention]

An object of the present invention is to provide an expansion pipe joint that is highly reliable under high pressure.

[Summary of the invention]

A basic feature of the present invention is an expansion pipe joint in which a sleeve is included inside, characterized in that a distal end portion of the sleeve has a lower rigidity than the other portion of the sleeve. According to this, the impact pressure within the pipe can be absorbed and prevented from propagating in the joint direction with deformation, preferably elastic deformation, of the bellows.

[Implementation sequence of the invention]

Figure 2 shows the cooling system of the fast breeder reactor illustrated in Figure 4 (s1 practical structure of the present invention, showing in detail the bellows expansion joint 9 to be installed). Figure 1 shows a straight line with a relatively simple structure.
This shows the composition of the f star. The bellows 1 is connected to the short pipe 2 and absorbs the thermal expansion displacement of the pipe f4 connected to the short pipe 2. The pipe 3 is arranged along the inside of the bellows L as f4.
It is extended inward as a sleeve 6, connected to the bellows I, and connected to the short tube 2 to form a pipe joint. 4a is a sliding seal. In the sleeve 6 extending from the pipe end connected to the pipe 3 of this pipe fitting to the inside of the pipe 4 connected to the other pipe end, the rigidity of the sleeve tip 5 is higher than that of the other part 19 of the sleeve. less than rigidity. The difference in rigidity can be achieved by providing a difference between the materials of the tip portion 5 and the material of the other portion 19. Possible ways to give this difference include changing the amount of material or using metallographic treatments such as heat treatment.

According to this embodiment, when the fc# impact force generated by the sodium-water reaction in the evaporator 13 propagates in the direction of the arrow in FIG. 1, impact pressure is applied to the sleep tip 5. . Then, since circumferential stress is applied to the tip portion 5, it expands in the radial direction as shown in the wJz diagram. Here, since the elastic modulus E of the sleep tip 5 is sufficiently small, the tip 7 of the sleep 6 gradually comes into contact with the inner wall of the pipe 4, and the impact pressure is applied to the bellows chamber 7 where the bellows 1 is installed.
As shown in FIG. 2, the flow path 16 for the fluid 8 in the piping 3 and the fluid 18 in the bellows chamber 7 can be completely closed before the fluid propagates to the inside. Therefore, the impact pressure within the pipe 3 does not propagate to the bellows chamber 7 surrounding the outside of the bellows 1, and it is possible to prevent the bellows 10 from buckling and collapsing due to the impact pressure.

Now, regarding the bellows type expansion joint 9 of typical material and shape used in fast breeder reactors, the possibility of elastic deformation of the above-mentioned sleep tip will be considered. The tip side material is austenitic stainless steel, which is a typical structural material with lower rigidity than Inconel materials for other parts. Let the length be t=150m. Assuming that the temperature of the sleep tip 5 during operation is 500C, its elastic modulus is E=16200 Kq/m2. Here, it is assumed that the sleeper mounting portion is a rigid body, and a pressure P=25 Kf/d is applied to the entire sleeper tip as shown in FIG. Considering the sleep tip 5 as a cantilever beam, the radial displacement amount δ of the sleep tip 17 can be expressed by the following equation.

Here ■ is the moment of inertia of area, in this case I =
1' 0.4 m'. Therefore, the amount of displacement of the sleep tip 17 is δ-94m, and it is possible to obtain a deformation that is light enough to close a gap of several tens of degrees, which is the typical distance between the sleep tip 5 and the f4. can. In addition, the maximum stress α of sleep 6 caused by I# positive impact pressure,
,,1 occurs near the sleep attachment part, and its magnitude is V,,''-5kCg/1II12 in this case. Therefore, the sleep tip 5 deforms within the elastic range. Ninth, the impact pressure wave sleeps at the tip 5
After passing through, the sleep tip 5 separates from the piping 4 and returns to its normal position, allowing it to fulfill its original function of preventing pressure loss and preventing the generation of second lotion. As described above, since the sleeper 6 can be used without being plastically deformed, there is no need to replace the sleeper 6, which is very economical in terms of plant operation.

According to the above embodiment, before the shock pressure generated due to the sodium-water reaction in the evaporator L3 propagates to the bellows chamber 7 where the bellows l is installed, the fluid 8 in the distribution f3 and the bellows chamber 7 The flow path 16 of the fluid L8 can be closed, and buckling collapse of the external pressure type bellows 9 due to impact pressure can be prevented.

The structure of the bellows-type expansion joint 9 shown in FIG. 5gt is almost the same as that of the second embodiment shown in FIG.
The plate thickness decreases from 1 to 17. In this embodiment, the rigidity of the sleeve tip portion 5 is small and it is easy to elastically deform compared to the case where the thickness of the sleeve tip portion 5 is constant. Regarding the amount of elastic deformation of the sleep tip 17 when pressure is applied to the entire sleep tip 5, the embodiment shown in FIG. 6 is about four times larger than the embodiment shown in FIG. Since the acting force between the tip portion 5 and the pipe 4 is larger than that shown in FIG. 1, it is easy to close the flow path 16 between the fluid 8 in the distribution f3 and the fluid 18 in the bellows chamber 7.

In the third embodiment shown in FIG. 7, the sleeve 6 is composed of a plurality of cylinders having a constant thickness, and the thickness of the cylinders decreases from the sleeve attachment part side to the tip end side. In this embodiment, the stiffness of the sleeve tip 5 is smaller than that in the case where the plate thickness is constant, so that it is easily elastically deformed. In addition to Figure 7, there are multiple plate thicknesses! It is also possible to decrease the number r in stages. In this embodiment, the thickness of the plate decreases stepwise, so that the reverse machining of the sleeve tip 5 is easy.

In the fourth implementation row, FIG. 8 is attached to the sleep tip 5 of FIG. 1,
This figure shows a bellows-type expansion pipe joint 9 provided with a slit 20 that is open at 10,000 mm along the axial direction of the sleeve. In the embodiment shown in FIG. 8, the sleeve 6 has a cylindrical shape, but when the sleeve tip 5 is elastically deformed, it is difficult to be restrained in the circumferential direction and is easily elastically deformed. When the impact pressure propagates between the fluid 8 in the pipe 3 and the fluid 18 in the bellows chamber 7, a flow path is opened through the slit 20, but the orifice effect reduces the pressure and causes the impact pressure to increase. does not propagate directly into the bellows chamber 7. The ratio of the pressure increase in the bellows chamber 7 to the pressure increase due to the impact pressure in the piping 3 can be considered to be approximately equal to the ratio of the flow path area of the slit 20 portion and the flow path area of the piping 3. The slit width is sufficient.

The fifth interlocking row shown in FIG. 9 shows a bellows-type expansion pipe joint in which the opening amount of the sleeve distal end 5 increases from the other sleeve section 19 side to the sleeve distal end section 17 side. In the real l@ row, the distance between the sleep tip 17 and the pipe 4 is smaller than when the sleep tip 5 and the pipe 4 are parallel, and the flow path is closed in a short time when impact pressure propagates. can do.

The sixth embodiment row shown in FIG. 1θ shows a bellows-type expansion pipe joint 9 characterized in that a protrusion 21 is provided in the middle of the elastically deformable sleeve tip 5. In this embodiment, even if the impact pressure reaches the outside of the sleep tip 5, the flow path is closed by the protrusion 2L, so the impact pressure will not reach the bellows chamber 7 and the bellows l. can prevent buckling collapse. Although FIG. 10 shows only one protrusion 21, a plurality of protrusions 21 may be provided. Providing a large number of protrusions increases the rigidity, so by appropriately changing the material, the rigidity can be reduced.

Furthermore, by using a sleep structure that combines each of the above embodiments, it is possible to more reliably prevent the bellows-type expansion pipe joint 9 from buckling and collapsing due to an impact load.

In each of the above embodiments, the sleeve is attached to the side of the pipe 3 where the bellows 1 is provided, but the sleeve can also be attached to the other pipe 4.

Although each of the above embodiments describes the case where an external pressure type bellows is used in an expansion pipe joint, it is also applicable to an expansion pipe joint using an internal pressure type bellows.

Further, although each of the above embodiments describes a straight pipe type expansion joint, it is also applicable to a hinge disk expansion joint, a universal star expansion joint, and various other expansion joints.

〔Effect of the invention〕

According to the present invention, in an expansion pipe joint, the flow path of internal fluid from the pipe to the joint structure can be closed or the flow path area can be reduced, so that the impact pressure propagating inside the pipe is loaded into the joint structure. This has the effect of preventing the bellows from buckling and collapsing.

[Brief explanation of the drawing]

ST diagram is a vertical sectional view of the external pressure type bellows type expansion pipe joint of the first embodiment of the present invention, FIG. A vertical cross-sectional view of a conventional external pressure type bellows type expansion joint, Figure 44 is a system configuration diagram of an atomic couplet equipped with a bellows type expansion joint,
Figure 5 shows the impact pressure change diagram due to the sodium-water reaction accident and the collapse pressure of the external pressure type bellows, and Figure 6 shows the second example of the present invention.
FIG. 7 is a vertical cross-sectional view of the external pressure type bellows type expansion pipe joint of the third implementation row of the present invention, and FIG. FIG. 9 is a vertical cross-sectional view of an external pressure type bellows type expansion pipe joint of the fifth embodiment of the present invention, and FIG. FIG. 2 is a longitudinal cross-sectional view of an external pressure type bellows type expansion pipe joint according to an embodiment. l...Bellows, 5...Sleep tip, 6...
Sleep, 9...Bellows type expansion pipe joint, 17...
Sleep first part, 19...Sleep other part, 20...
- Slit, 21... protrusion.

Claims (1)

[Scope of Claims] 1. An expansion pipe joint that includes a sleeve inside, characterized in that a distal end portion of the sleeve has a lower rigidity than the other portion of the sleeve. 2. The expansion pipe joint according to claim 1, wherein the sleeve has a shape in which a distal end portion thereof is thinner than other portions. 3. The expansion pipe joint according to claim 1, wherein the sleeve has a shape in which the plate thickness gradually decreases toward the tip. 4. The expansion pipe joint according to claim 1, wherein the sleeve has a shape in which the sleeve has a slit along the axial direction of the sleeve that is opened at the front end of the sleeve. . 5. The expansion pipe joint according to claim 1, wherein the sleeve has a shape in which a diameter of the sleeve at the tip thereof is larger than a diameter of the sleeve at the other portions. 6. The expansion pipe joint according to claim 1, wherein the diameter of the distal end portion of the sleeve gradually increases toward the distal end. 7. The expansion pipe joint according to claim 1, wherein the sleeve has a protrusion on the outer periphery of the distal end portion.