JPH059593Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention is designed to prevent crack propagation caused by low-temperature brittle fracture in cylindrical storage tanks that store low-temperature liquefied gases such as liquefied petroleum gas and liquefied natural gas. The present invention relates to a low temperature storage tank equipped with a side plate having a welded joint structure.

(Prior Art) As shown in Fig. 3, a conventional low-temperature cylindrical flat-bottom storage tank has a circular flat bottom plate, a cylindrical side plate vertically installed near the periphery of the bottom plate, and an upper end of the side plate. A spherical roof plate is provided in series with the section to form a sealed shape, and a low temperature liquid such as low temperature liquefied gas is stored inside. In this case, the side plates are formed by stacking rectangular flat steel plates like brickwork and welding them together.

Although not shown, the inner tank and outer tank in the case of a double-shell cylindrical storage tank, the inner tank, middle tank, and outer tank in the case of a triple-shell cylindrical storage tank with a suspension deck, and the horizontal cylindrical storage tank. Similarly, the side plates of the peripheral wall are formed by forming a rectangular steel plate into a ring body and then welding the ring body in the axial direction.

Cracks caused by low-temperature brittle fracture in this low-temperature cylindrical storage tank originate from welding defects, defects at the removal site of assembly jigs, fatigue cracks from these, and even impact scratches from the outside. It is generated and propagated by stress and the load of the stored liquid.

(Problems to be solved by the invention) In the conventional low temperature cylindrical storage tank, the side plate is a cylinder made by welding together rectangular flat steel plates, and the weld line is parallel to the axis of the cylinder of the low temperature storage tank, i.e. It is formed in a direction perpendicular to the circumferential direction where the main tensile stress is exerted, which is the direction in which cracks tend to propagate, so once a brittle crack occurs, it can easily propagate along the weld line. It has some problems.

In addition, in the conventional example, the side plate is made of a material with good low temperature characteristics.
For example, should it be made of JIS G3127 9% nickel steel, or should a low-temperature material such as JIS G3126 aluminum killed steel and a material with good low-temperature properties be used alternately, or should a low-temperature material be layered with a material with good low-temperature properties? Alternatively, a weld metal with good low-temperature properties is used to form the welded joint, thereby preventing the occurrence of cracks due to low-temperature brittle rupture and suppressing the propagation of cracks. These structures and methods have problems that make them uneconomical.

(Means for solving the problem) This invention is a low-temperature cylindrical storage tank with a welded structure consisting of a side plate in which a ring body formed of a flat steel plate is connected in the axial direction. The axial joint between the side steel plates is a welded joint structure that is inclined with respect to a straight line parallel to the axis of the storage tank to prevent crack propagation due to low-temperature brittle rupture, thereby providing a low-temperature storage tank that solves the above-mentioned problems. The purpose is to

(Function) Since the weld line of the side plate is oblique to the direction in which cracks in the cylindrical storage tank tend to propagate, that is, it is diagonal to the straight line parallel to the axis, cracks due to low-temperature brittle rupture occur in the direction in which they tend to propagate. Because there is a base material in an adjacent area that has better toughness than the weld, it cannot easily spread.

(Example) An example of this invention will be described in detail with reference to the drawings. FIG. 1 is an overall perspective view of a low temperature flat bottom cylindrical storage tank according to this invention.

In the figure, 1 is a side plate, 2 is a side steel plate, 3 is an axial joint, 4 is a circumferential joint, 5 is a bottom plate, and 6 is a roof.

The low-temperature flat-bottomed cylindrical storage tank has a side plate 1 formed into a ring body by welding side steel plates 2 and 2 together in a vertical direction near the periphery of a circular flat bottom plate 5, and an upper edge of the side plate 1. A sealed roof 6 is welded to the tank to form a flat cylindrical sealed storage tank.

The side steel plate 2 is made of a low-temperature material, such as a carbon steel plate for low-temperature pressure vessels (JIS G3126), or a material with relatively good low-temperature properties, such as a 2.5% to 3.5% nickel steel plate (JIS G3127). As shown in the figure,
It is formed into a parallelogram with a straight line 7 parallel to the axis and an inclination angle of α degrees.

The α degree angle needs to be an angle that can suppress crack propagation due to low temperature brittle rupture. For example, when using carbon steel plates for low temperature pressure vessels, the α degree angle is 15 degrees or more.
Form at 45 degrees.

It goes without saying that when using nickel steel plates, etc., which are less prone to crack propagation due to low-temperature brittle rupture, the lower limit value of the inclination angle α can be set to a value smaller than 15 degrees, taking into consideration that crack propagation is less likely to occur. stomach.

Further, the upper limit of the inclination angle α is preferably set to about 45 degrees in consideration of the economical efficiency of cutting the side steel plate 2, welding, etc.

As mentioned above, the side plate 1 when carbon steel plate material for low-temperature pressure vessels is used is a parallelogram-shaped side plate steel plate 2 with an axial joint 3 inclined at an angle of 15 to 45 degrees with respect to the straight line 7, and a circumferential joint. They are welded and joined so that 4 is a horizontal line perpendicular to straight line 7, and stacked in multiple stages to form a cylindrical shape.

In this case, the welding material used for welding the axial joints 3 and circumferential joints 4 of the side plate 1, which are made of carbon steel plates for low-temperature pressure vessels, is a material with good low-temperature properties, such as 1.5% to 11% nickel ( It is desirable to obtain a weld metal containing Ni).

Although this embodiment concerns a single-shell flat-bottomed cylindrical storage tank, the joints 3 in the axial direction of the side plates of the inner tank and outer tank of the double-shelled cylindrical storage tank shown in FIG. The same applies to the side plate axial joint of a triple-shelled cylindrical storage tank with a wall deck, and also to the circumferential wall axial joint 3 of a horizontally placed cylindrical storage tank shown in FIG.

(Effects) Since this invention is constructed as claimed in the utility model registration based on the above-mentioned embodiment, the cracks associated with low-temperature brittle rupture are obliquely in contact with the weld line where the cracks tend to grow. In other words, a crack that occurs in a low-toughness region of an inclined weld propagates almost perpendicular to the circumferential direction where the main tensile stress acts, and immediately enters the upper and lower adjacent base metal parts with good toughness and is stopped.
The propagation of large-scale cracks is suppressed, making it possible to provide a practical low-temperature storage tank that can minimize damage.

In addition, there is no need to use expensive steel plates that have exceptional low-temperature brittle crack propagation arresting properties for the side plate material, and there is no need to use expensive steel plates that have exceptional low-temperature brittle crack propagation arresting properties. It also has excellent practical benefits.

[Brief explanation of the drawing]

Fig. 1 is an overall perspective view of a low-temperature single-shell flat-bottom cylindrical storage tank according to this invention, Fig. 2 is an expanded enlarged view with part of the side plate shown in Fig. 1 removed, and Fig. 3 is a conventional example. An explanatory diagram of crack propagation due to low-temperature brittle rupture in a flat-bottomed cylindrical storage tank. Fig. 4 is an explanatory diagram showing an application example of a low-temperature double-shell flat-bottomed cylindrical storage tank. Fig. 5 is an explanatory diagram showing an application example of a horizontal cylindrical storage tank. It is a diagram. 1... Side plate, 2... Side steel plate, 3... Axial joint, 7... Straight line parallel to the cylinder axis, α... Inclination angle of the axial joint with respect to the straight line parallel to the cylinder axis.

Claims (1)

[Scope of utility model registration request] In a low-temperature cylindrical storage tank with a welded structure consisting of side plates in which flat steel plates are joined to form a ring body and the ring bodies are connected in the axial direction, the axial direction of the parallelogram-shaped side steel plates forming the ring body is A low-temperature storage tank characterized in that the joint has a welded joint structure that is inclined with respect to a straight line parallel to the axis of the storage tank so as to suppress crack propagation due to low-temperature brittle fracture.