JPS6331634B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for constructing a double shell tank having a PC outer tank, and more particularly, an outer tank formed of prestressed concrete (PC).

Conventional construction methods for double-shelled tanks with a PC outer tank of this type include those shown in Figures 3 to 5. That is, to explain the construction method shown in FIGS. 3a, b, and c, the PC outer tank side wall 2 is constructed on the foundation 1, and tension work is also performed. Then the above PC
Inside the outer tank side wall 2, construction of the bottom cold insulation 3, assembly and welding of the inner tank 4, and inspection are performed. At this time, the bottom cold insulation work, the inner tank welding work, the loading and unloading of equipment for inspection, and the entry and exit of workers will all be performed from the upper part of the side wall of the PC outer tank.

According to this method, (a) the metal work for assembling and welding the inner tank is performed after the civil engineering work for the side walls of the PC outer tank, resulting in poor staffing efficiency due to the changeover of different types of construction work, and a long construction period. There is a drawback.
(b) Because the inner tank, bottom cold insulation work, and equipment for inspection are all carried out through the side wall of the PC outer tank,
This is extremely inconvenient and not only affects the construction period but also poses a danger to workers.

Next, to explain the construction method shown in Fig. 4 a, b, and c, first, the inner tank bottom cold insulation 3 construction is performed on the foundation 1, and after assembling and welding the inner tank 4 on top of this,
Work is carried out on the PC outer tank side wall 2 on the outside of this, and tension work is also carried out on this, the outer tank roof is completed, and as part of the prescribed inspection, cold insulation work on the sides and roof is performed.

According to such a method, (a) the metal work for the inner tank construction is carried out, and then the civil engineering work for the PC outer tank side wall construction work is carried out, which reduces the efficiency of personnel allocation due to switching between different types of construction work. The disadvantage is that the construction period is long and the construction period is long. (b) PC after completion of inner tank construction
As a result of the civil engineering work, a considerable amount of civil engineering work was carried out between the inner and outer tank side walls, including the transport, installation, and removal of formwork for concrete pouring.
It is necessary to widen the space between the inner and outer tanks.

This means that the tank needs to be made 1.5 to 2.0 m from around 1 m in a normal tank, and the cold storage space is larger than necessary, which not only increases the cooling cost but also increases the diameter of the PC outer tank. Civil engineering costs will increase dramatically. In addition, the volume of the cold storage space between the inner and outer tanks becomes large, the amount of nitrogen gas filled in this space becomes large, and the capacity of the breathing tank for adjusting the gas pressure inside the cold storage space becomes larger than necessary. It is extremely uneconomical. (c) As the PC civil engineering work will be carried out after the inner tank construction is completed,
Civil engineering work on the outer tank may damage the outer surface of the inner tank, which is undesirable.

Next, to explain the construction method shown in Fig. 5 a, b, c, and d, the roofs 5 and 6 are first assembled and welded on the foundation 1, and then the inner tank side wall 4a and the PC outer tank side wall 2 are welded in parallel. After the both side walls 2 and 4a are completed, the roofs 5 and 6 are lifted to a predetermined position and completed, and after predetermined inspections are performed, the side and roof insulation work is carried out.

According to such a method, (a) the inner tank side wall and the PC side wall are constructed in parallel after the roof is assembled, so the construction of the inner and outer tanks becomes complicated and the construction period becomes longer.
(b) There are concerns regarding safety management. In other words, due to the complexity of the construction work, equipment necessary for constructing the inner tank must be brought in and taken out over the outer tank wall. (c) Since the construction work is carried out by appropriately combining both side wall works, it is not economical as there will be a shortage of hands for either of the works. (d) Generally speaking, there is a high possibility that the construction of the inner tank wall will take place slightly earlier than the PC wall, and as in the previous example shown in Figure 3, the gap between the inner and outer tank side walls will be larger than necessary, resulting in the same problem as above. It comes with drawbacks. (e) If we consider only the civil engineering work, there will be a long period of roof work (3 to 4 months for large tanks) between the foundation work and the PC outer tank work, and civil engineering work will be interrupted during that time. Therefore, it is inefficient in terms of equipment operation and personnel allocation.

The present invention has been made to solve the problems of the prior art as described above, and eliminates the drawbacks of the conventional technology by using extremely rational construction methods. The metal work, bottom cold insulation, inner tank bottom plate, and inner tank side plate work were carried out and completed, eliminating the complication of work on the inner and outer tank side walls.
The aim is to provide a construction method that shortens the construction period and has a large economic effect.

Examples of the construction method of the present invention will be explained with reference to FIGS. 1a, b, c, and d as follows. As shown in FIG. 2B, in the process of assembling the outer tank side wall 11a on the foundation 10 without tension, a construction opening 12 as shown in FIG. 2 is formed in the lower part of the outer tank side wall 11a.

From the concrete on both sides of the construction opening 12,
The PC wire 17 and sheath 18 for circumferential tension are partially protruded in preparation for connection when the opening is closed. Since it is difficult to add the PC wire 17, it is necessary to set the PC wire 17 to a predetermined length and wind it, or to wrap the predetermined length into the sheath 1 when closing.
8 all at once. Further, a part of the PC rod 19 and the sheath 20 for emergencies in the vertical direction are made to protrude from the upper edge of the opening 12, and only the sheath 20 is buried in the lower part of the opening 12. The PC rods 19 can be connected by coupling or welding, and the opening 12 can be closed at a later date without any problem. The equipment necessary for constructing the roofs 13 and 14 is brought in through this opening 12 for construction, and while continuing the construction of the outer tank side wall 11a on the foundation 10, the roof 1
Perform the ground assembly of 3 and 14.

In addition, if a liner made of steel or the like is to be installed on the inner surface of the PC concrete outer tank, it is of course necessary to install the bottom liner first.
In addition, as shown in Fig. 1c, the annular part cold insulation 21, which is a part of the bottom cold insulation, the inner tank annular plate 22, and part of the lower part of the inner tank side plate were constructed.
This may be done prior to the erection of the roofs 13 and 14.

After the roofs 13 and 14 are completed, the bottom cold storage and the inner tank bottom plate are assembled, but depending on the construction, the necessary equipment may be brought in in advance and assembled at a later date. The equipment that can be used for constructing the inner tank side wall 15a is left behind, the others are carried out of the outer tank through the construction opening 12, and instead, the equipment necessary for constructing the inner tank side wall 15a is brought in through the construction opening.

Next, as shown in c, the inner tank side wall 15a is constructed using a conventional construction procedure, and is completed. The used equipment is carried outside through the construction opening 16 provided in the inner tank side wall 15a and the construction opening 12 in the outer tank side wall 11a, and then the roofs 13 and 14 are lifted.
One roof 14 is attached to the upper end of the inner tank side wall 15a, and the other roof 13 is attached to the upper end of the outer tank side wall 11a.

Then, move all the equipment to both construction openings 12 and 1.
6, open both openings 12 and 16 by d.
Close like. The opening 16 of the inner tank is closed by welding in the usual manner. As mentioned above, the opening of the outer tank was closed by connecting a new sheath with a coupling or welding to the sheath that had been made to protrude from the concrete in advance, and also by making it protrude in advance.
Connect new PC rods to the PC rods by coupling, welding, etc., insert these PC rods and PC wires into the sheath, connect reinforcing bars back and forth, and then pour concrete using appropriate formwork. This is done by In the case of an outer tank whose inner surface is lined, the lining can of course be completed. Thereafter, a pressure test and an airtightness test were conducted on the inner tank 15, while tension was applied to the outer tank side wall 11a using PC wires and PC rods, and an airtightness test was conducted on the outer tank 11.
3, 14 and side cold insulation work, all construction work is completed.

The tension on the outer tank side wall 11a is determined by the airtight test,
This can be done after the roof and side cold insulation work is completed. In addition, a liner may be placed on the inner surface of the outer tank side wall 11a to provide secondary storage capacity in the event that the stored liquid flows out from the inner tank to improve liquid tightness. It is used in place of formwork or is placed after concrete is poured.

In this way, the present invention constructs the roof on the foundation while constructing the PC outer tank wall, and constructs the inner tank side walls after the roof is assembled on the ground.
There is almost no complication between civil engineering and metal work, there is no construction work left unoccupied, and personnel allocation can be done rationally, making it possible to significantly shorten the construction period. In addition, the construction of the inner tank will be carried out concurrently with the construction of the PC wall, but the construction of the inner tank wall will be carried out after the construction of the PC wall is completed or after the construction of the PC wall.
This is done in a way that follows the construction of the wall.
There only needs to be enough space between the PC wall and the inner tank metal work, and unlike conventional methods, the outer tank diameter does not need to be increased more than necessary.This reduces cold storage costs, PC wall costs, and breathing tank costs. It has excellent features such as being able to reduce capacity.

[Brief explanation of the drawing]

Figure 1 a, b, c, d is a flowchart of the construction method of the present invention, Figure 2 is a perspective view of the main parts of the same, Figure 3 a, b,
c, FIGS. 4a, b, and c, and FIGS. 5a, b, c, and d are flowcharts of conventional construction examples, respectively.

Claims (1)

[Claims] 1. When constructing a flat-bottom cylindrical double-shell tank whose outer tank side wall is made of prestressed concrete (PC), an opening for construction was created at the bottom of the outer tank side wall in the process of assembling it on the foundation without tension. Then, the PC rod and sheath for vertical tension were partially protruded from the concrete above and below the opening, and
The sheath for the PC wire for circumferential tension is made to protrude from the concrete on both sides of the opening, and a part of the concrete reinforcement is made to protrude, and equipment necessary for assembly, such as the inner tank, is placed through the construction opening. The construction of the inner and outer tank roofs was carried out on the foundation inside the outer tank side walls, and at the same time, the assembly work of the PC outer tank side walls was continued, and the ground assembly of the inner and outer tank roofs was carried out. After completion, the bottom was kept cool and the bottom plate of the inner tank was installed as appropriate, and then the inner tank side wall construction work was completed, and the equipment brought in was carried outside through the construction opening on the outer tank side wall. after,
Connect a new sheath to the sheath that was previously provided in the construction opening protruding from the concrete, insert the newly connected PC rod and the PC wire that had been set to a predetermined length, and then move it back and forth. Connect the reinforcing bars, then close the opening by pouring concrete using appropriate formwork, and apply a specified tension to the completed outer tank side wall using PC wires, PC rods, etc. A construction method for a double shell tank with a PC outer tank characterized by: