JPH06106345A - Stress reduction welding structure of pressure vessel - Google Patents

Abstract

PURPOSE:To embody the stress reduction welding structure of a pressure vessel being excellent in the economics, by which a local bending stress is scarcely developed in weld zones of each shell, respectively in end plate structures of both ends, and accordingly, plate thickness of each shell can be decreased, and also, troublesome surface working and an inspection are obviated. CONSTITUTION:In a pressure vessel 7 in which both ends of a cylindrical shell 1 are closed up by an end plate structure formed by a toroidal shell 2 and a spherical shell 4, this pressure vessel is provided with an outer joining weld zone 3 for connecting the cylindrical shell 1 and each toroidal shell 2, respectively, and an outer joining weld zone 5 for connecting the toroidal shell 2 and each spherical shell 4.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a stress-reduced welded structure for a pressure vessel.

[0002]

2. Description of the Related Art As a pressure vessel, a conventional pressure vessel, for example, FIG.
As shown in the side view, from the overall viewpoint of workability, volumetric efficiency, and pressure resistance, both ends of the cylindrical shell 01 are closed by the end plate structure formed by the toroidal shell 02 and the spherical shell 03, respectively. , Widely adopted.

However, in such a structure, when the pressure vessel receives the internal pressure p, a bending stress is generated in the welded portion of each shell having a discontinuity of curvature, which overlaps with the film stress and a high stress locally exists. Therefore, it has the following drawbacks. (1) When designing according to design standards, the required size for allowable stress increases. (2) The required size for fatigue strength increases. (3) Troublesome surface processing and inspection are required.

[0004]

SUMMARY OF THE INVENTION The present invention has been proposed in view of such circumstances, and local bending stress is unlikely to be generated in the welded portions of each shell in the end plate structure at both ends. An object of the present invention is to provide a stress-reduced welded structure for a pressure vessel which can reduce the thickness of shell and which is economical and requires no complicated surface processing or inspection.

[0005]

Therefore, according to the present invention, in a pressure vessel in which both ends of a cylindrical shell are closed by an end plate structure formed of a toroidal shell and a spherical shell, respectively, the cylindrical shell and the toroidal shell are And an external welding portion for connecting the toroidal shells and the ball shells, respectively.

[0006]

According to this structure, an externally welded portion connecting the cylindrical shell and each toroidal shell,
By providing an external welding portion that connects each of the toroidal shells and each of the ball shells, the bending moment generated in each welding portion in which the curvature of each shell is discontinuous and the bending moment in the opposite direction are respectively applied to each welding portion. Since it is generated in the part, the following action is performed. (1) Bending stress generated in the welded part is reduced, and it is possible to prevent an increase in plate thickness. (2) The fatigue strength of the welded part is improved, and it is possible to prevent an increase in plate thickness, and it becomes unnecessary to perform troublesome surface processing and inspection.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. First, in the side view of FIG.
1 is a cylindrical shell having a radius a and a plate thickness t ₁ and receiving an internal pressure p, 2
Is a toroidal shell of 1 pair of front and rear with a thick plate thickness t ₂ than the plate thickness t ₁ of the cylindrical shell 1 while being welded by the respective outer alignment welds 3 to the front and rear ends of the cylindrical shell 1. 4 is the front end of the toroidal shell 2 at the front end,
Externally welded part 5 to the rear end of the toroidal shell 2 at the rear end
Together are welded by, before and after a pair of spherical shell having a thin plate thickness t ₃ than the thickness t ₂ of the toroidal shell 2, 6
Is a pair of front and rear end plate structures formed by the toroidal shell 2 and the ball shell 4 in cooperation with each other, and 7 is a pressure vessel formed by the cylindrical shell 1, each toroidal shell 2 and each ball shell 4 in cooperation with each other. .

In such a structure, as shown in the vertical sectional view of FIG. 2, when the internal pressure p acts on the pressure vessel, the end portion of the cylindrical shell 1, that is, the external welding portion 3 is pulled by the inner surface, A bending moment M ₂ that causes compression on the surface is generated, and this magnitude is M ₂ = P when the misalignment amount e and the in-plane force P
It becomes e / 2. On the other hand, considering the shearing force Q ₀ and the bending moment M ₀ acting on the cylindrical shell 1 from the toroidal shell 2 as shown in the side view of FIG. Meissner,
S. P. According to Teimo Schienko's approximation theory, radius a / plate thickness t
_{When 1} is larger than 30, the portion of the toroidal shell 2 transmitting the bending moment can be handled as a part of the cylindrical shell 1, so there is no extreme difference in plate thickness between the cylindrical shell 1 and the toroidal shell 2. In this case, since the shearing force Q ₀ causes the same amount of rotation on both sides of the externally welded welded portion 3, the bending moment M ₀ can be regarded as almost zero.

Therefore, only the bending moment M ₁ due to the shearing force Q ₀ is generated at the end of the cylindrical shell 1. This is a moment that is pulled on the outer surface of the cylindrical shell 1 and compressed on the inner surface, and is a moment in the direction opposite to the bending moment M ₂ generated by the misalignment amount e in FIG. 2, so that the cylindrical shell 1 and the toroidal shell 2 have By forming the welded portion as the externally welded portion 3, the bending moment M ₁ can be reduced by the shearing force Q ₀ as shown in the diagram of FIG. 4, and the bending stress generated in the externally welded portion 3 can be reduced. be able to.

Furthermore, when the rate of decrease in stress is examined specifically, as shown in FIG. 1, when the internal pressure p, the radius a, and the plate thickness t ₁ of the cylindrical shell 1, the portions of the spherical shell 4 and the toroidal shell 2 are long. When it can be regarded as an elliptical shell with axis / minor axis = 2, the maximum value of the surface stress in the generatrix direction at the end of the cylindrical shell 1 is calculated by the formula
It is indicated by (1). (Σ _x ) _max = (ap) (2t) ^-1 + 3ap {t [3 (1-ν ² )] ^0.5 } ^-1 ζπ4 ^-1 = 2.172ap (2t) ^-1 (1) Here Where ν = 0.3 (Poisson's ratio), ζ (x) = e ^−x s
inx This is the film stress ap in the generatrix direction where the surface stress is due to the internal pressure p.
It shows that it has reached 2.172 times of (2t) ⁻¹ . Here, considering the bending stress due to the misalignment amount e of the present invention,
This is 1/3 of the damping coefficient by moving away from the misalignment.
As (1/3) × [(ap) / 2] × (e / 2) × (6 / t ² ) = (e / t) × [(ap) / (2t)] .... (2 ) Here, for example, assuming that t ₁ = 37 mm and e = 10 mm, (e / t) × [(ap) / (2t)] = 0.270ap / (2t) ... (3) (Σ _x ) _max − [(0.270ap) / (2t)] = 1.902ap / (2t) ... (4) That is, the maximum value of surface stress (σ _x ) _max is It drops to 88% of that of equation (1).

The same action is also established for the external welded portion 5 which is the joint between the toroidal shell 2 and the spherical shell 4 although the curvatures are different.

According to the structure of the embodiment as described above, an external welding portion for connecting the cylindrical shell and each toroidal shell, and an external welding portion for connecting each of the toroidal shell and each ball shell are provided. By providing the bending moments in the opposite directions to the bending moments generated in the welded portions in which the curvatures of the shells are discontinuous, the following effects can be obtained. (1) The bending stress generated in the welded part is reduced, and it becomes possible to prevent an increase in plate thickness, thus improving the economical efficiency. (2) The fatigue strength of the welded part is improved, it is possible to prevent the increase in plate thickness, and it becomes unnecessary to perform troublesome surface processing and inspection.
Therefore, economic efficiency and reliability are improved.

[0013]

In summary, according to the present invention, in the pressure vessel in which both ends of the cylindrical shell are closed by the end plate structure formed of the toroidal shell and the spherical shell, the cylindrical shell and the toroidal shell are connected to each other. By including the externally welded portion, and the externally welded portion that connects the toroidal shell and the ball shell, respectively, local bending stress is applied to the welded portion of each shell in the end plate structure at both ends. The present invention is extremely useful industrially because it is difficult to generate, and therefore, the plate thickness of each shell can be reduced, and a stress-reduced welded structure of a pressure vessel that is excellent in cost and does not require complicated surface processing or inspection is obtained. It is something.

[Brief description of drawings]

FIG. 1 is a side view and a partially enlarged vertical sectional view showing an embodiment of the present invention.

2 is a partially enlarged vertical sectional view showing a bending moment when an in-plane force is present in the externally welded portion 3 of FIG.

FIG. 3 is a partial side view showing a shearing force and a bending moment acting on the cylindrical shell 1 from the toroidal shell 2 of FIG.

FIG. 4 is a diagram showing bending moment along a generatrix of the cylindrical shell 1 of FIG. 1.

FIG. 5 is a side view showing a known pressure vessel.

[Explanation of symbols]

1 Cylindrical shell 2 Toroidal shell 3 Externally welded part 4 Ball shell 5 Externally welded part 6 End plate structure 7 Pressure vessel a Radius e Difference amount M ₀ Bending moment M ₁ Bending moment M ₂ Bending moment P In-plane force p Internal pressure Q ₀ Shearing force t ₁ thickness t ₂ thickness t ₃ thickness

Claims (1)

[Claims] 1. A pressure vessel in which both ends of a cylindrical shell are closed by an end plate structure formed of a toroidal shell and a spherical shell, respectively, and an external welding portion for connecting the cylindrical shell and the toroidal shell, respectively. A stress-reducing welding structure for a pressure vessel, comprising: an externally welded portion that connects each of the toroidal shells and each of the ball shells.