Reservoir tank for storing a liquid

A reservoir tank comprises a tank body and a double bottom. The tank body is constituted of a roof, a tank bottom plate and a tank wall. The roof and the tank bottom plate are fixed to the tank wall by welding. The double bottom includes a double bottom plate and a rim, which are fixed to each other by welding. A leakage liquid outlet is formed at one side of the double bottom plate on which reinforcement ribs are arranged in a lattice state. Cutouts are formed in the reinforcement ribs. The double bottom plate has a declivity so that the leakage liquid outlet is positioned at the lowermost level. The rim is provided with three detection ports. Upon welding the tank wall to the rim, the inside of the double bottom becomes an airtight state.

This Non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No(s). 2003-199167 filed in Japan on Jul. 18, 2003, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a reservoir tank for storing a liquid, and in particular to a reservoir tank whose bottom structure is improved.

2. Description of the Related Art

There is a reservoir tank for storing a liquid. It is necessary to seal the inside of the reservoir tank in order to prevent the stored liquid from leaking. If the bottom of the reservoir tank corrodes due to deterioration and so forth, the liquid is likely to leak therefrom. For the purpose of preventing the stored liquid from leaking out of the reservoir tank, various ideas are conceived regarding a bottom structure of the reservoir tank, such as described in Japanese Patent Laid-Open Publication No. 9-272991, for example. The Publication No. 9-272991 relates to an electric anticorrosion method for an outer surface of a tank bottom plate to be placed on an asphalt sand. With respect to this method, linear insoluble electrodes are arranged on the asphalt sand in a lattice state. A conductive material is laid over the whole surface of the asphalt sand so as to cover the insoluble electrodes. Further, a sand layer is formed on the conductive material. The insoluble electrode is connected to a plus side of a DC power supply and the tank is connected to a minas side thereof to supply a predetermined anticorrosive current to the outer surface of the tank bottom plate.

However, as for the electric anticorrosion method of the above-noted publication wherein an external power-supply system is adopted for the outer surface of the bottom plate of the outdoor tank, it is necessary to lay the linear insoluble electrodes on the asphalt sand, on which the reservoir tank is placed, in the lattice state. Thus, there arise problems in that an installation operation takes a lot of labor and the cost increases. In a case of the outdoor-type reservoir tank having a large size, it is impossible to transfer it through a general rode. Therefore, welding for assembly is performed at a place for setting the reservoir tank. Sometimes it is impossible to deal with the reservoir tank such as described in the above-noted Publication No. 9-272991. Further, it is difficult to externally check the liquid leaking out of the bottom. In case the liquid leaks out of the bottom, there arises a problem in that the leakage liquid pollutes the underground.

SUMMARY OF THE INVENTION

In view of the foregoing, it is a primary object of the present invention to provide a reservoir tank adapted to prevent underground pollution to be caused by a liquid, which has leaked out of the bottom thereof.

It is a second object of the present invention to provide a reservoir tank adapted to securely retrieve a leakage liquid.

In order to achieve the above and other objects, the reservoir tank according to the present invention comprises a tank body and a double bottom. The tank body stores a liquid. The double bottom is fixed to the bottom of the tank body. It is preferable that the double bottom has an airtight structure and a declivity. Further, it is preferable that the double bottom is provided with a port for detecting gas concentration.

In a preferred embodiment, the double bottom comprises a reinforcement member for supporting a tank bottom plate of the tank body. The reinforcement member is formed with a cutout through which the leakage liquid is allowed to move. Moreover, it is preferable that the double bottom has an outlet for discharging the leakage liquid accumulated in the double bottom. The tank is preferable to be a large-sized outdoor tank of which the tank body is directly fixed to a base.

According to the reservoir tank of the present invention, the liquid having leaked from the tank body is accumulated in the double bottom so that the liquid is prevented from flowing out of the reservoir tank. Since the double bottom has the airtight structure, the leakage liquid is surely prevented from flowing out of the reservoir tank all the more.

The double bottom has the declivity so that the leakage liquid is easily discharged to the outside. Since the double bottom is provided with the port for detecting gas concentration, it is possible to confirm whether or not the liquid leaks from the tank body to the double bottom. Moreover, since the double bottom has the outlet for discharging the leakage liquid of the double bottom, the leakage liquid, which is accumulated in the double bottom, is easily discharged to the outside.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

As shown inFIG. 1, a reservoir tank2according to the present invention comprises a tank body3and a double bottom4attached to the bottom of the tank body3. The reservoir tank2is of an outdoor type. The tank body3has a cylindrical shape and stores a liquid6of various solvents, heavy oil, oil and so forth. As to the solvents, there are methylene chloride, methyl acetate, acetone, methyl formate, dioxoran, cyclopentane and so forth. The reservoir tank2has a capacity of 50 KL or more, and preferably 100 KL or more. The reservoir tank2is assembled at an installation place. However, the present invention is applicable to the other reservoir tank to be assembled in a small factory.

As shown inFIG. 2, the tank body3is constituted of a roof8, a tank bottom plate9and a tank wall10. This tank wall10has a three-part structure and is constituted of a first wall11, a second wall12and a third wall13. The first wall11is the lowermost part, and the third wall13is the uppermost part. The second wall12is the intermediate part and is fixed to the first and third walls11and13by means of welding. The first wall11is constituted of four wall segments11ato11d. The second wall12is constituted of four wall segments12ato12d. The third wall13is constituted of four wall segments13ato13d. Vertical welding lines of the respective wall segments11ato13dare alternately arranged so as to prevent the adjacent welding lines from continuing in a vertical direction. The roof8is fixed to an upper side of the wall segments13ato13dby means of welding. The tank bottom plate9is fixed to a lower side of the wall segments11ato11d.

The roof8has a taper shape going down toward the edge thereof. The wall segment11aof the tank body3is formed with a maintenance opening16to which a flange17is fitted so as to cover it. When the inside of the tank body3is checked and cleaned, the flange17is detached. Incidentally, the roof8may be vertically moved, instead of attaching to the tank wall10, depending on an amount of the liquid6stored in the tank body3.

An inlet pipe18is attached to the roof8. The inlet pipe18is inserted into the tank body3. The liquid6is injected into the tank body3through the inlet pipe18. An outlet pipe19is attached to the wall segment11d. The outlet pipe19is welded to a through hole20(seeFIG. 2) formed in the wall segment11d. The outlet pipe19is connected to various manufacture lines via flanges, which are not shown, to transport the liquid6. By the way, each of the inlet pipe18and the outlet pipe19is provided with a valve which is not shown. By opening the valve, it becomes possible to inject and transport the liquid6. Meanwhile, although an illustration is omitted, various attachments of a thermometer, a pressure gauge and so forth are fixed to the tank body3and are covered with a heat-retention member, a protective cover and so forth as need arises.

As shown inFIGS. 3 and 4, the double bottom4comprises a double bottom plate21and a rim22being as a side wall, which are fixed to each other by means of welding. A left side of the double bottom plate21is provided with a leakage liquid outlet24for discharging the accumulated liquid6to the outside. The leakage liquid outlet24is connected to a discharge pipe31described later. The double bottom plate21is provided with a plurality of reinforcement ribs25arranged in a lattice form. The reinforcement ribs25are provided with cutouts25afor leading the liquid6, which is accumulated in a region surrounded by the reinforcement ribs25, to the leakage liquid outlet24. A number and a shape of the cutouts25amay be properly changed. Incidentally, a number of the reinforcement ribs25may be properly changed on condition that the double bottom plate21is reinforced.

The rim22is formed with three detection ports27for detecting the liquid6leaking from the tank body3. The detection ports27are positioned at intervals of 120 degrees, for example. A checking pipe28(seeFIG. 1) is welded to the detection port27. A cap29is fitted to the checking pipe28and is detached at the time of inspection to insert a gas concentration meter and so forth. In this way, it is possible to confirm whether or not the liquid6leaks from the tank body3to the double bottom4. It is needless to say that the number of the detection ports27may be properly changed.

As shown inFIGS. 4A and 4B, the double bottom plate21is adapted to have a declivity in a slope direction A so that the leakage liquid outlet24is positioned at the lowermost level. In this embodiment, a ratio of the declivity is 1/100 and is preferable to be 5/1000 to 3/100. In virtue of the declivity, the liquid6having leaked from the tank body3to the double bottom4is concentrated at a left side (side of the leakage liquid outlet24) of the double bottom4.

The double bottom4is fixed to a concrete base30made in the outdoors. The concrete base30has a cutout through which the discharge pipe31passes to connect with a recovery pit33. An exit of the discharge pipe31is provided with a valve32. By opening this valve32, the liquid6accumulated in the double bottom4flows into the recovery pit33to retrieve the liquid6. By the way, instead of the discharge pipe31, a recovery port may be formed in the rim22. The recovery port is usually closed with a flange or the like, and is opened by detaching the flange to retrieve the liquid6.

After assembling the double bottom4on the concrete base30, the tank body3is built on the double bottom4such as described above. The first wall11of the tank body3is fixed to the rim22of the double bottom4by means of welding. Thereupon, the inside of the double bottom4becomes an airtight state.

As just described, the double bottom4is fixed to the bottom portion of the tank body3and the inside of the double bottom4is sealed. Thus, in case the liquid6leaks from the tank body3, the leakage liquid is accumulated in the double bottom4and is prevented from leaking to the outside of the reservoir tank2. Further, by inserting the gas concentration meter and so forth into the detection port27formed in the double bottom4, it is possible to confirm whether or not the liquid6leaks from the tank body3to the double bottom4. Since the leakage liquid outlet24is formed in the left side of the double bottom plate21and is connected to the discharge pipe31, the liquid6accumulated in the double bottom4is gathered into the recovery pit33through the discharge pipe31.