JP2002054773A - Pipe joint structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the earthquake resistance in a pipe joint structure fastened by a bolt and nuts via a flange. SOLUTION: In this pipe joint structure for fastening pipes or the pipe and a valve by the bolt and nuts via the flange, a leaf spring absorbing the deformation of the pipe 1 is disposed between the flange 4 outside face and the seating face of the bolt 6 or the seating faces of the nuts 7 and 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe joint structure in which pipes or pipes and valves are fastened with bolts and nuts through flanges, and a pipe is provided between an outer surface of a flange and a bolt seat surface or a nut seat surface. The present invention relates to a pipe joint structure in which an elastic body that absorbs the deformation of the above or a fluid pressure cylinder exhibiting a resistance proportional to the deformation speed is additionally provided.

[0002]

2. Description of the Related Art An external force acting on a pipe which is buried underground and adjacent pipes or pipes and valves are fastened by bolts and nuts via flanges acts on the flanges due to an earthquake. .

[0003] As a conventional countermeasure when an external force that causes the above-mentioned deformation is applied to a pipe buried underground, there are the following measures.

(1) Replacement with a high-strength valve The valve body is made of high-strength cast steel or the like, or the rigidity is improved by increasing the wall thickness or increasing the material strength.
Adopting a high-strength valve with a shape that can reduce stress concentration against external forces due to an earthquake, improves seismic resistance.

(2) Incorporation of a telescopic tube A flexible telescopic tube having a corrugated cross section in the longitudinal direction is incorporated into the pipe between the flanges to be fastened or in the middle of the pipe near the flange to displace the pipe during an earthquake. Is absorbed by a telescopic tube.

(3) Improvement of Flange Strength The flange of the pipe and the flange of the valve are made to have high rigidity and strength so that the strength of the flange portion is higher than the strength of the pipe.

(4) Improving the strength of the entire pipe All the flanges and the pipe main body have sufficient rigidity, strength and displacement absorbing ability.

Alternatively, a bypass pipe is laid as in the live pipe branching method, and a valve is installed there.

[0009]

However, the above-described conventional measures for preventing deformation of a flange portion of a buried pipe due to an external force during an earthquake have the following problems.

(1) Replacement with a high-strength valve In order to replace the valve body from the existing piping, it is necessary to stop the operation of the pipeline or reduce the supply amount of gas or the like supplied in the pipeline. Adversely affect operations.

[0011] In addition, procurement and replacement work of a new valve requires high cost.

In order to adjust the conformity of the seal surface between the existing straight pipe flange and the flange of the new valve, a tightening operation with a torque larger than a set torque may be required.

(2) Incorporation of telescoping pipe In order to incorporate a pipe part having a corrugated cross section in the longitudinal direction into a flange part of an existing valve or a part of a main pipe near the valve, the operation of the pipeline may be stopped. Therefore, it is necessary to reduce the supply amount of gas and the like supplied in the pipeline, which adversely affects the operation.

In addition, work such as cutting or welding existing pipes is required to incorporate the telescopic pipes, which increases the cost of procuring the telescopic pipes and increases the cost for safety curing and replacement work. It costs.

Further, the seismic effectiveness of the telescopic tube is limited by the installation conditions, and it is necessary to take measures against stress concentration for a repetitive load of a normal design.

(3) Reinforcement of Valve / Flange When the pipe including the flange of the existing valve or the flange on the pipe side is individually reinforced, or when the whole is reinforced by parts having high rigidity and strength, the entire structure is required. However, for a displacement control type load such as an earthquake load, the deformation concentrates on the weakest point in the vicinity, which may lead to destruction. In particular, it is difficult to improve the performance of the seal portion only by reinforcement.

Further, since a large amount of cost is required for reinforcing parts and construction, the return on investment as an earthquake countermeasure is not always large.

(4) Renewal of pipes All pipes including flanges of existing valves or flanges on the main pipe side are replaced with pipes having sufficiently high rigidity, strength and displacement absorption capacity. Although useful for ensuring safety, it is not a practical method because the operation of the pipeline is stopped for a long period of time and the cost of renewal is enormous.

The present invention has been made to solve the above-mentioned problems of the prior art, and is intended to improve the seismic performance of piping at low cost without interrupting the operation of the pipeline. It is an object of the present invention to provide a pipe joint structure that can be used.

[0020]

A first joint structure of a pipe according to the present invention is a joint structure of a pipe in which pipes or pipes and valves are fastened with bolts and nuts through flanges. An elastic body that absorbs deformation of the pipe is arranged between the surface and the nut seating surface. Further, the elastic body is constituted by a disc spring. Further, the elastic body is constituted by a coil spring. Further, the elastic body is covered with a protective case. Further, in the second joint structure of a pipe according to the present invention, in a joint structure of a pipe in which pipes or pipes and valves are fastened with bolts and nuts via flanges, a piston rod has a bolt hole on an outer surface of one flange. And a disc spring is disposed inside the cylinder on the flange side with respect to the piston of the hydraulic cylinder, and a male screw provided at the end of the piston rod is connected to the other end. When the nut is screwed together from the flange side to fasten both flanges, and when an external force accompanied by deformation acts on the flange, a fluid proportional to the deformation speed is exhibited while flowing fluid through the through hole provided in the piston. It is like that.

In the joint structure for a pipe according to the present invention, an elastic body such as a disc spring or a cylindrical coil spring that absorbs deformation of the pipe is arranged between the outer surface of the flange and the bolt or nut seat. Therefore, elastic deformation is small with respect to a normal design external force, and large deformation can be absorbed with a low load increase rate against an earthquake external force.

Further, the load sharing ratio does not increase with respect to the compressive force as in a general bolted body, and the displacement absorbing ability can be exhibited only with respect to the tensile force.

Even if the gasket changes its surface pressure due to repeated deformations and impacts due to repeated loads and impacts during an earthquake, a part of the compression deformation accumulated in the spring is released to reduce the required surface pressure. Can be maintained.

In addition, the same surface pressure as the existing surface pressure of the flange gasket seal surface can be maintained even under a normal design load other than the time of an earthquake, so that high joint performance can be obtained.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings, taking as an example a case where a pipe and a valve are fastened with bolts and nuts via flanges.

FIG. 1 is a sectional view showing a first embodiment of a pipe joint structure according to the present invention. In this joint structure, a flange 2 of a pipe 1 and a flange 4 of a valve 3 are connected to a gasket 5
A threaded bar (hereinafter referred to as a double-threaded bolt) 6 having male threads at both ends and nuts 7 and 8
The outer surface 2a of the flange 2 of the pipe 1
A plurality of (six in FIG. 1) coned disc springs 11 are arranged between the screw nuts 6 at the center thereof through the washers 9 and 10 between the nut and the seating surface 7a of the nut 7. I have.

In FIG. 1, one bolt
Although only nuts are shown, a plurality of bolts are arranged along the circumferential direction of the flange, and a disc spring 11 is arranged on each of the bolts.

As the disc spring 11, a commercially available product standardized in JIS B 2706 is used. Regarding the spring constant, which is the ratio of the load to the deflection of the disc spring 11, design data has been published, and how many disc springs 11 are stacked in the same direction (this is called the number of parallel pieces). An arbitrary spring constant can be set by setting the number of stacked disc springs 11 as one unit, changing the direction of the disc springs 11 alternately and stacking them (this is referred to as the number of series).

In order to improve the deformation absorbing performance at the time of earthquake resistance, arbitrary deformation can be absorbed by arranging the required number of disc springs 11 continuously in series.

An example of the data of the spring constant of the disc spring 11 is as follows.
As shown in FIG. In FIG. 2, the straight line connecting the circles is shown in FIG.
As shown in (a), one series in parallel 1 (only one disc spring)
In FIG. 3 (b), the straight line connecting the spring constants in the case of is the spring constant of two parallel series 1 (two disc springs are stacked in the same direction), and the straight line connecting the 3C shows the spring constants of the series 1 of the parallel 3 (three disc springs 11 are stacked in the same direction). Thus, the disc spring 11
Are stacked in the same direction, the spring constant increases in proportion to the number of disc springs 11.

In FIG. 2, the straight line connecting the marks ● is
A straight line connecting the spring constants of one parallel series 4 (alternately changing the direction and overlapping four) shown in FIG. 3D and a cross mark is shown in FIG. (2 in the same direction
The spring constant is shown assuming that one disc spring 11 is one unit, and these are alternately changed in direction and stacked in four rows. When the directions of the disc springs 11 are alternately changed and overlapped, the spring constant decreases in inverse proportion to the number of rows to be overlapped. That is, when the directions of the disc springs 11 are alternately changed and overlapped, the amount of deformation or displacement absorption for the same load increases as compared with the case where the disc springs 11 are overlapped in the same direction.

Therefore, when high rigidity is required for the flange joint, the disc springs 11 are stacked in the same direction,
When it is desired to increase the deformation amount or displacement absorption amount as much as possible, the disc springs 11 may be alternately changed in direction and stacked.

As described above, the disc spring 11 having a simple shape is
An arbitrary spring constant can be obtained by changing the direction and the number of sheets and variously combining them, so that application to various types of flange joints becomes possible.

Normally, the tightening force of the double-threaded bolt 6 is designed with an allowable stress in consideration of a sufficient safety factor with respect to the yield strength and tensile strength of the bolt material. I will not do it.

The elastic body of the disc spring structure in the actual design
The behavior of the bolted joint against external force is shown in the graph of FIG.
Can be explained by Optional double threaded thread at flange joint
Focusing on the bolt 6, both flanges 2 on the pipe 1 side and valve 3 side
And 4 are tightened members, and the bolt holes are double-threaded bolts.
6 is considered as a fastener penetrated, and the shaft of both screw bolts 6
Tensile force F_p, On both flanges 2 and 4, which are members to be tightened
Compression force F_pAre generated and balanced. This fastening body
When a tensile external force W is applied to both bolts 6
It is extended and the tensile force F _bIs added, but
External tension W and tension F_bIs the elongation of the tightened member
Spring constant C of bolt and nut system including flexible body_bAnd
Angle θ representing a constant_b, The compression spring constant C of the tightened member_c
And the angle θ representing the spring constant_cFrom the following (1)-(3)
It can be obtained by an equation.

[0036]

(Equation 1)

[0037]

(Equation 2)

[0038]

(Equation 3)

[0039] The ratio of the tensile force F _b and the tensile force W to be added to the bolt shank phi, from it is called out force ratio, the inner and outer power ratio phi between the (1) and (3), ( 4) It can be obtained by the equation.

[0040]

(Equation 4)

[0041] That is, as the spring constant C _b of the fastening member is reduced, so that the sharing ratio for the external force is reduced.

Therefore, if an elastic body such as a disc spring 11 is arranged in the fastening body as in the joint structure of the pipe of the present invention, a large increase in the load against external force can be minimized while absorbing a large displacement as the fastening body. can do.

The material of the disc spring 11 may be a corrosion-resistant material such as stainless steel or a shape memory alloy, depending on the application. The periphery of the disc spring 11 may be densely filled and covered with a natural rubber or a synthetic rubber, or a polymer material allowing a large elastic deformation. As a result, the plurality of disc springs 11 are integrated into one part, so that transport, storage and construction are extremely easy.
In addition, even if it is repeatedly deformed, it can also function as a retainer that keeps the relative positions of the individual disc springs 11 and the arrangement with respect to the bolt 5 constant. In addition, by utilizing the viscoelastic deformation resistance, the force acting on the fastening part can be reduced.

Further, with respect to an external force, a characteristic is obtained in which the compression elastic modulus of rubber is superimposed on the spring constant of the disc spring 11, so that the deformation absorbing characteristics of the entire fastening body can be designed more variously. Become.

By joining the abutting surfaces of the apexes of the disc springs 11 to form a hermetically sealed space having a diamond-shaped cross section, it is possible to reduce the resistance due to the consolidation of the rubber in this portion. When filling the disc spring 11 with rubber, the rubber enters the space having a rhombic cross section,
It is also possible to avoid a situation where the filling process is difficult.

FIG. 5 is a sectional view showing a case where the disc spring 11 is covered with the protective case 12 in the pipe joint structure according to the first embodiment of the present invention. In this way, by covering the disc spring 11 with the protective case 12, the disc spring 11 can be protected from damage due to external force, and in the underground buried portion, etc., the infiltration of the soil in the surrounding ground can be prevented,
The stable displacement absorption performance of the disc spring 11 can be maintained. In this case, the washer 10 shown in FIG. 1 is unnecessary, and the protective case 12 itself also serves as a washer.

Although the protective case 12 shown in FIG. 5 is not a sealed type that completely covers the disc spring 11, the protective case 1 is used to ensure the thorough displacement absorbing performance of the disc spring.
2 may be a closed type.

FIG. 6 is a sectional view showing a second embodiment of the pipe joint structure of the present invention. This joint structure is
The flange 22 of the valve 23 and the flange 24 of the valve 23 are put together via a gasket 25 and fastened with double screw bolts 26 and nuts 27 and 28. The outer surface 22a of the flange 22 of the pipe 21 and the seating surface of the nut 27 A cylindrical coil spring 31 whose center is penetrated by both screw bolts 26 is disposed between the coil spring 27 and washers 29 and 30.

In FIG. 6, one bolt
Although only nuts are shown, a plurality of bolts are arranged along the circumferential direction of the flange, and a cylindrical coil spring 31 is arranged on each of them.

The cylindrical coil spring 31 is specified in JIS B 2704 and includes a spring steel, a hard steel wire or a stainless steel wire,
It can be selected from many materials such as a shape memory alloy depending on the application. In designing the cylindrical coil spring 31, along with the material properties, the wire diameter, the coil diameter, the number of turns,
An arbitrary spring constant can be set by appropriately selecting dimensional conditions such as height.

Further, by arranging the cylindrical coil springs 31 having different spring constants in series or concentrically in parallel, it is possible to set more various spring constants.

Also in the case of the pipe joint structure of this embodiment, the circumference of the cylindrical coil spring 31 may be filled and covered with natural rubber or synthetic rubber, or a polymer material which allows a large elastic deformation. . Thereby, since the compression elastic modulus of the rubber is superimposed on the spring constant of the cylindrical coil spring 31 with respect to the external force, the deformation absorption characteristics of the entire fastening body can be designed more variously. In addition, by utilizing the viscoelastic deformation resistance, the force acting on the fastening part can be reduced.

FIG. 7 is a sectional view showing a third embodiment of the pipe joint structure of the present invention. This joint structure is
A pneumatic cylinder 43 is disposed on the outer surface of the flange 42 so that the piston rod 43a passes through the bolt hole, and a disc spring 44 is disposed inside the cylinder 42 closer to the flange 42 than the piston 43b of the pneumatic cylinder 43. Then, a nut 47 is screwed into a male screw provided at the end of the piston rod 43a from the flange 46 side of the valve 45,
Via a gasket 48 both flanges 42 and 46
When an external force accompanied by deformation is applied to the flange, the resistance is proportional to the deformation speed while flowing air through the through hole 43c provided in the piston 43b.

In the joint structure of this pipe, when the disc spring 44 is subjected to a displacement to be compressed by an external force, in addition to the elastic deformation of the disc spring 44, the volume compression elasticity of the air in the pneumatic cylinder 43 and the through-hole 43c This reduces the force acting on the fastening part due to the viscous resistance associated with the outflow of air.

Further, a hydraulic cylinder may be employed in place of the pneumatic cylinder 43. In this case, the elasticity and the viscous deformation resistance of the fluid are strengthened more than the air, and the force acting on the fastening part can be further reduced.

In the description of the embodiment of the present invention, the bolt has been described as an example of a through bolt. However, when connecting the valve and the piping, there is no space between the valve body and the flange. This is because it is difficult to insert the bolt into the bolt hole with the hexagon bolt specified by the normal JIS.

Therefore, it goes without saying that hexagon bolts are sufficient for fastening the flanges of the pipes.
When using a hexagon bolt, a disc spring or 11
The cylindrical coil spring 31 may be arranged not only between the flange and the nut seat but also between the flange and the bolt seat. Further, the material of the bolt and the nut may be a corrosion-resistant material such as stainless steel or a shape memory alloy. Further, the nut may be subjected to a loosening prevention treatment by a double nut or the like.

Since the joint structure of the present invention is configured as described above, an arbitrary spring constant can be set by selecting a combination of spring materials, dimensions / shapes, and arrangements. Is easy. In addition, it is possible to set a non-linear spring characteristic, and a super-elastic characteristic can be obtained by utilizing snap-through deformation. Further, the surface pressure can be secured without resisting the compressive load. In addition, since it is only necessary to replace existing bolts, work with existing construction tools (spanner, torque wrench) is possible, without requiring skill in the work, construction quality control is easy, and Work can be performed without stopping operations. In addition, since there is no interference with the valve body by adopting the double screw bolt, it can be applied to all structures regardless of the valve specifications. Furthermore, it is useful for seismic measures not only for FC valves but also for any flange bolted joints. In addition, normal loosening prevention such as a double nut can be applied, and combination with other quake-resistant structures such as a dash pot is easy. Also,
It is possible to set an arbitrary tightening torque according to the tightening state of the existing valve flange and tightening conditions according to the strength and rigidity of the existing valve and the straight pipe flange. Also, there is almost no restriction on the construction environment and the work speed is high. Simultaneous and continuous work is possible. In addition, there is almost no development element by applying the existing technology, and practical application is possible immediately.

Further, by applying a superelastic material, it is possible to impart better deformation recovery characteristics.

[0060]

According to the present invention, it is possible to absorb a large deformation of a pipe due to an external force due to an earthquake or the like. In addition, to reduce the surface pressure due to the compressive deformation of gaskets due to repeated loads and impacts during an earthquake and the aging, the required surface pressure can be reduced by releasing part of the compressive deformation accumulated in the spring. Can be maintained. Further, the performance of the existing flange gasket with respect to a normal load other than the time of an earthquake can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of a pipe joint structure according to the present invention.

FIG. 2 is a diagram showing an example of spring constant data of a disc spring.

3A and 3B are explanatory diagrams of a stacking method of a disc spring, and FIG.
Is the case of series 1 with one parallel, (b) is the series 1 of two parallels
(C) is a diagram showing the case of a series 1 of three parallels, (d) is a diagram showing the case of a series 4 of one parallel, and (e) is a diagram showing the case of a series 4 of two parallels.

FIG. 4 is a graph showing a behavior of a bolt fastening portion with respect to an external force by an elastic body having a disc spring structure.

FIG. 5 is a cross-sectional view showing a case where the disc spring is covered with a protective case in the pipe joint structure according to the first embodiment of the present invention.

FIG. 6 is a sectional view showing a second embodiment of the pipe joint structure of the present invention.

FIG. 7 is a sectional view showing a third embodiment of the joint structure for piping of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piping 2 Flange 3 Valve 4 Flange 5 Gasket 6 Double screw bolt 7, 8 nut 9, 10 Washer 11 Disc spring 12 Protective case 21 Piping 22 Flange 23 Valve 24 Flange 25 Gasket 26 Double screw bolt 27, 28 Nut 29, 30 Washer 31 Cylindrical coil spring 41 Piping 42 Flange 43 Pneumatic cylinder 43a Piston rod 43b Piston 43c Through hole 44 Disc spring 45 Valve 46 Flange 47 Nut 48 Gasket

Claims (5)

[Claims] In a joint structure of a pipe in which pipes or a pipe and a valve are fastened with bolts and nuts through a flange, elasticity for absorbing deformation of the pipe is provided between an outer surface of the flange and a bolt seat surface or a nut seat surface. A pipe joint structure in which a body is arranged. 2. The joint structure for piping according to claim 1, wherein said elastic body is formed of a disc spring. 3. The joint structure for a pipe according to claim 1, wherein said elastic body is constituted by a coil spring. 4. The joint structure for a pipe according to claim 1, wherein the elastic body is covered with a protective case. 5. A joint structure for a pipe in which pipes or pipes and valves are fastened with bolts and nuts through flanges, a fluid pressure cylinder is provided on an outer surface of one of the flanges so that a piston rod passes through the bolt hole. With the arrangement, a disc spring is arranged inside the cylinder closer to the flange side than the piston of the fluid pressure cylinder, and a nut is screwed into a male screw provided at the end of the piston rod from the other flange side. Both flanges are fastened, and when an external force with deformation is applied to the flanges, a fluid is circulated through a through hole provided in the piston, and a resistance proportional to the deformation speed is provided. Joint structure.