JPS5919229B2 - Construction method of flat bottom cylindrical tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of constructing flat bottom cylindrical tanks such as floating roof tanks, dome roof tanks, low temperature double shell tanks, etc.

For storing large quantities of liquids such as petroleum, LPG, and LNG, flat-bottomed cylindrical tanks such as large floating roof tanks and single or double shell dome roof tanks are generally used.

The current construction method for this type of flat-bottom cylindrical tank is that the annual plate is assembled on the foundation (bottom cold insulator) constructed at the tank construction site, and then the side plates and bottom plate are welded. be.

With this construction method, it is impossible to inspect the welding points between the annular plates, the welding points between the annular plate and the side plate, and the welding points between the annular plate and the bottom plate using radiation.
There are disadvantages in that it is almost impossible to confirm the presence or absence of internal defects in the welded part, and on the other hand, the corner part has the disadvantage that large bending stress due to hydraulic pressure acts locally on the side plate, and when the side plate is welded, the annular This is a serious structural weakness, such as welding distortion that tends to cause the plate or bottom plate to warp upward, making it susceptible to structural damage, and the above-mentioned construction inspection shortcomings exacerbate this structural weakness. It was hot.

The causes of these problems are that the welding between the annual plates and the welding of the annual plate and the side plate is done on the foundation, so the welds cannot be inspected by radiation; Fillet welding or group welding as a welding method is not necessarily complete penetration welding. It is.

The present invention was made in view of these circumstances, and it eliminates the drawbacks of the conventional method by simple and rational construction methods.
In particular, it is possible to inspect the welds between the annular plate and the side plates, which could not be done with conventional methods, resulting in defect-free welded joints, and by performing complete penetration welding on each weld, the accuracy of inspection is improved. At the same time, the purpose is to reduce the welding strain that causes the annular plate or bottom plate to warp upward, and to strengthen the tank corner.
Example Temporary frames 2 are placed at appropriate intervals on the foundation 1 constructed at the construction site of a flat-bottomed cylindrical tank such as a floating roof tank or a dome roof tank to match the designed diameter of the tank. .

Next, after placing the annular plate 3 on the pedestal 2, the annular plates are butt-welded on both sides (or equivalent one-sided welding), and this welded part is sequentially radiographically inspected for defects in the welded part C. Inspect for the presence of defects, and if there are any defects, perform repair welding at the location and re-inspect the location.

In order to ensure smooth inspection, it is desirable that the welded joints between the annular plates 3 are not located on or near the pedestal 2. In addition, it is optional whether the inspection of the welded part is carried out after all the annular plates 3 are joined to obtain the ring-shaped bottom body A, or whether it is carried out sequentially after welding and after the welding has cooled down. The timing of the inspection is not specified. After all the welding and inspection of the annular plate 3 have been carried out in this way and the ring-shaped bottom body A has been obtained, or while forming the bottom body A, the lowermost side plate is 4 is stood upright, and its lower edge and the bottom body, ie, the upper surface of the annular plate 3, are welded together by complete penetration welding means.

When the side plates 4 are sequentially welded to form a ring shape in this manner, joint welding between each side plate 4 is performed by a conventional method, and this portion is also welded by butt welding on both sides.

Then, welding inspections are carried out between the side plates, the annular plates, and between the side plates, but this inspection can also be carried out after all welding is completed as described above, or it can be carried out sequentially after cooling the welded parts without waiting for completion. It is optional to do so. Complete penetration welding of the annular plate 3 and side plate 4 and radiographic inspection were completed in this way, and the resulting ring-shaped tank corner body B was lowered onto the foundation 1 by removing the pedestal 2 in the manner described later. After that, a side plate 4 and a bottom plate 5 of the next stage are butt-welded to this tank corner body B using a conventional method to construct a flat-bottomed cylindrical tank C such as a floating roof tank or a dome roof tank.

The annular plate 3 and the bottom plate 5 are welded by penetration welding using a backing metal or by lap welding. In addition, in order to lower and place the completed tank corner body B from the top of the mount 2 onto the foundation 1, it was either lowered using a jack, or a temporary suspension pedestal was set up, and the whole body was suspended and supported. In a tank with a roof, either remove all the frames 2 and lower the tank, use a vertically expandable frame 2 and lower it while gradually reducing the size, or remove the frames. Any method can be used, such as erecting the roof to the ground and lowering the tank using the roof as a support, or, in the case of low-temperature double shell tanks, temporarily installing a bracket on the side plate of the outer tank and lowering the tank while hanging from the bracket.

In addition, as shown in Figure 4, the lowermost side plate is welded to the annular plate in advance, inspected and made into a block, and this block body is transported to the site and melted onto the frame as described above. It is also possible to obtain tank corners by joining by welding.

The welding inspection of the above-mentioned annual plates can be easily done by installing the welded joints away from the pedestal. If it is impossible to insert the film, the mount is removed by jacking up or the like and a prescribed inspection is carried out, and after the inspection, the mount is restored and installed again.

As described above, the present invention is to assemble and weld the annular plates to each other and the annular plates and the lowermost side plate on a frame placed on the foundation surface to obtain a ring-shaped tank corner body. Therefore, following welding, non-destructive inspection using radiation etc. can be smoothly performed in the same state, and
Since it can be carried out accurately and defects in welds can be found and repaired appropriately, quality control of tank corners can be completely controlled and fatigue cracks from welds can be prevented. be.

In addition, the ring-shaped tank corner body obtained by welding and inspection while floating on the foundation surface can be lowered and installed on the foundation while using the center part of the foundation as a work space. , which has the advantage of improving work efficiency.

In addition, since at least the annular plate and side plate are welded by complete penetration welding, the above-mentioned internal defect inspection is easy, and the bath contact area is strengthened.
It has excellent features such as further improved prevention of fatigue cracks.

[Brief explanation of the drawing]

Fig. 1 is a cutaway perspective view of the main part showing how the annular plate and side plate are connected, Fig. 2 is a longitudinal sectional front view of the same as above, Fig. 3 is a partial longitudinal sectional front view of the tank, and Fig. 4 is an example. FIG.

Claims (1)

[Claims] 1. Welding and inspecting the annual plates together, inspecting the welding between the annual plate and the lowest side plate, welding and inspecting the side plates together on a frame installed on the foundation constructed at the tank construction site, and inspecting the annual plates. For welding the plate and side plate,
A ring-shaped tank corner was constructed using complete penetration welding, and then the frame was removed using the center of the foundation as a work space, and the ring-shaped tank corner was lowered onto the foundation. A method of constructing a flat-bottom cylindrical tank, characterized in that the side plates are then sequentially welded to the side plates by a conventional method, and the periphery of the bottom plate is welded to the inner periphery of the annular plate by a conventional method.