JPS6226393Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a ballast tank in an offshore storage tank structure for flammable liquids.

Generally, offshore storage tanks for flammable liquids such as petroleum have a double shell structure at the bottom and sides.
This tank is constantly filled with seawater to form a ballast tank, and in the event of an oil fire inside the storage tank, the ballast tank has the function of a water-sealing tank that cuts off heat and prevents the disaster from spreading to other storage tanks. It's set. In the huge offshore stockpiling tanks used for this purpose, especially when the tank is empty, the water seal exerts great pressure on the tank's surrounding wall, so the ballast tank requires a lot of steel, and This may lead to higher costs. Therefore, in order to solve this problem, as shown in FIG.
2, the ballast tank is divided into a plurality of parts, and ventilation pipes 56, 57, 58 leading to the outside of the tank are arranged at the top of each compartment 53, 54, 55.
It has been proposed to reduce the water head pressure of the tank, reduce the amount of steel used, and provide the ballast tank with a permanent water seal function (see Japanese Utility Model Application Publication No. 55-52495). However, with this method, if a hole were to develop in the inner shell of the double shell structure and a leakage accident of the stored liquid occurred, there is a risk that the stored liquid would leak out of the ballast tank through the vent pipe.

This invention was made in view of the above points, and aims to provide a ballast tank in which stored liquid will not leak out of the tank even if a hole is made in the inner shell.

To achieve this purpose, the ballast tank of this invention has a plurality of ventilation pipes extending from the top of the offshore storage tank structure to each compartment, and penetrating each partition wall and entering the compartment below from the same wall. It is characterized in that it is provided with an open tube that projects in a hanging shape and whose upper end is open to the side of the structure.

The vent pipe serves to vent gas from each compartment, release gas when water is injected into each compartment, and detect leakage of flammable liquid into each compartment. The diameter of the vent pipe may be relatively small. On the other hand, the open pipe serves to release gas from each compartment and to release water when water is poured into each compartment. Therefore, the diameter of the open pipe is made large enough so that there is no problem with water discharge.

The protruding length of the open pipe is determined in consideration of the amount of flammable liquid leaked if the inner shell is punctured and the time required to establish measures to prevent the liquid from leaking.

As described above, the ballast tank according to this invention includes a plurality of ventilation pipes extending from the top of the offshore storage tank structure to each compartment, penetrating each partition wall and hanging down from the same wall into the compartment below. Since the structure has a protruding open pipe whose upper end opens to the side of the structure, when the water level in each compartment becomes higher than the protruding lower end of each open pipe, the air in each compartment cannot be discharged from the open pipe. It can be freely released from the vent pipe. Also, in the unlikely event that the inner shell is punctured, flammable liquid will leak into the compartment and collect there, and this liquid will gradually push the water level down until the water level reaches the bottom of each protruding end of the open tube. Until this point, leaked liquid cannot flow out of the open tube. Therefore, sufficient measures can be taken to prevent the flammable liquid from flowing out during this time, and the liquid can be reliably prevented from flowing out.

Examples of this invention will be described in detail below.

In Figure 2, a box-shaped storage tank structure 1 for storing flammable liquids such as petroleum at sea has a double shell structure with both side walls, both end walls, a bottom wall and a horizontal bulkhead, and is filled with seawater. As a result, the structure is used as a ballast tank. Both the inner and outer shells 2 and 3 of the ballast tank have a pressure-resistant structure.
Horizontal partition walls 4 and 5 are provided in each of the ballast tanks on both side walls, both end walls, and the transverse bulkhead at a height of about 1/3 and about 2/3 from the top, respectively. Divided into compartments 6, 7, and 8.

Inside the ballast tank, there are three vertical ventilation pipes 9, 10, 11 extending from the top of the structure 1 to the compartments 6, 7, 8, respectively, and the upper end opens to the side of the structure and the lower end is a partition. A required protrusion length l ₁ , which penetrates the walls 4 and 5 downward into each compartment 7 and 8, respectively.
_Two protruding open pipes 12 and 13 are provided.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of a part of a storage tank structure showing a conventional example, and FIG. 2 is a vertical sectional view corresponding to FIG. 1 showing an embodiment of this invention. 1... Storage tank structure, 2, 3... Inner and outer shell of ballast tank, 4, 5... Horizontal partition wall, 6, 7, 8...
Compartment, 9, 10, 11...ventilation pipe, 12, 13...
Open pipe, l ₁ , l ₂ ... protrusion length.

Claims (1)

[Scope of utility model registration request] In an offshore storage tank structure 1 in which a ballast tank is divided into a plurality of compartments 6, 7, and 8 by horizontal partition walls 4 and 5, each compartment 6,
a plurality of ventilation pipes 9, 10, extending to 7, 8, respectively;
11, and open pipes 12, 1 that penetrate through the partition walls 4, 5, respectively, project downwardly from the walls into the compartments 7, 8 below, and have their upper ends open to the sides of the structure 1.
A ballast tank characterized by having 3.