Patent Publication Number: US-7901158-B2

Title: Underwater oil storage method and system

Description:
RELATED APPLICATIONS 
     This application is a Divisional patent application of application Ser. No. 11/221,739, filed on 9 Sep. 2005, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an oil storage method and more particularly, to an underwater oil storage method, which keeps the oil tank under the water in a water pool so that the water in the water pool supports the pressure of the oil tank and isolates storage oil from the ground earth by means of the physical characteristic that the specific gravity of oil is lower than water. 
     2. Description of the Related Art 
     An oil storage tank may be mounted above or under the ground. When building an oil tank above the ground, a strong floor construction must be built up on the ground. The floor construction must be strong enough to support the heavy cylindrical or spherical steel shell of the oil tank and the oil stored in the oil tank. A conventional oil tank uses a steel shell to bear the pressure of the oil stored therein. The capacity has a limitation. Further, increasing the capacity of an oil tank will relatively increase the cost. For safety&#39;s sake, a retaining wall must be built around the oil tank(s) such that when oil leaks out of the oil tank(s), leaked oil can still be kept within the retaining wall to prevent contamination or any possible catastrophe. At present time, the capacity of Formosa Petrochemical Corp.&#39;s oil tank is 130,000 square meters (the largest oil tank in Asia Pacific area. This oil tank has a diameter about 86 meters and a height about 24 meters. The steel shell of the oil tank must strong enough to bear the pressure of 24M-depth storage oil and to provide a damping resistance against earthquake grade 6. It took about 2 years to finish the construction of the oil tank after finish of the ground construction. The total cost for this oil tank is about two hundred millions NT dollars. Because this oil tank is exposed to the weather, it must be regularly maintained to remove rust and regularly painted. In case of a leakage of oil, the storage oil must be fully discharged out of the oil tank and cleaned so that a soldering process can be employed to seal the crevice. Maintaining this oil tank is a hard and expensive task. 
     Further, when directly building an oil tank under the ground, the cost is high. In case of a leakage occurred, it is difficult to detect such a leakage, and leaked oil will permeate into the soil to pollute underground water. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished under the circumstances in view. It is therefore the main object of the present invention to provide an underwater oil storage method, which uses water to isolate storage oil from the ground earth by means of the physical characteristic that the specific gravity of oil is lower than water. It is another object of the present invention to provide an underwater oil storage method, which automatically regulates the water level of the water that supports the oil tank, keeping the oil tank in balance. It is still another object of the present invention to provide an underwater oil storage method, which keeps the oil tank under the water in a water pool, preventing contamination of storage oil to the surrounding ground earth, and allowing quick visual inspection upon an oil leakage. 
     To achieve these and other objects of the present invention, the underwater oil storage method includes the steps of a) excavating a cellar in the ground earth and constructing a wall structure in the cellar to form a water pool; b) setting an oil tank having a predetermined shape and volume in the water pool; c) supplying a predetermined amount of water to the water pool; and d) filling the oil to be stored into the oil tank and regulating the amount of water in the water pool subject to the amount of storage oil stored in the oil tank where the oil to be stored has a specific gravity lower than the water filled in the water pool, and the amount of the storage oil filled into the oil tank is less than the volume of the oil tank. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a flow chart of an underwater oil storage method according to the present invention. 
         FIGS. 2A˜2F  illustrate the construction and operation of an underwater oil storage system according to a first embodiment of the present invention. 
         FIGS. 3A˜3F  illustrate the construction and operation of an underwater oil storage system according to a second embodiment of the present invention. 
         FIG. 4  is a schematic sectional view of an underwater oil storage system according to a third embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 1 and 2A , an underwater oil storage method in accordance with the present invention includes the steps of: 
     a) excavating a cellar in the ground earth  10  and constructing a wall structure  20  in the cellar to form a water pool  30 , where the wall structure  20  is a continuous concrete wall set in the horizontal bottom and upright peripheral sides of the cavity formed in the ground earth  10  for protection and isolation; 
     b) setting an oil tank  40  in the water pool  30  and directly supporting the oil tank  40  on the bottom wall  31  of the water pool  30 , where the oil tank  40  can be a metal, concrete or plastic container or a container made of any of variety of oil-proof materials subject to a predetermined size and has an oil access port  41  at the top side thereof and at least one bottom port  42  at the bottom side thereof in communication with the inside space of the water pool  30  for allowing water to flow through the bottom port  42  between the water pool  30  and oil tank  40 ; 
     c) supplying a predetermined amount of water W to the water pool  30 , where water W can be city water, sea water, industrial waste water that is kept in the water pool  30  by the wall structure  20 ; said predetermined amount means that an auto fluid supplying and adjusting mechanism is provided to control the amount of water W in the water pool  30  subject to the type of oil tank  40  and the volume of oil stored in oil tank  40 ; and 
     d) filling oil O into oil tank  40  through oil access port  41 , where oil O can be raw petroleum, gasoline, mineral oil, animal oil, vegetable oil, or any of a variety of chemical fluids of specific gravity smaller than 1; the filling amount of oil O is less than the volume of oil tank  40  so that oil O filled in oil tank  40  does not flow out of oil tank  40  into the water pool  30  and then float on water W in the water pool  30  outside the tank  40 . 
     Referring to  FIGS. 2B and 2C , because the specific gravity of oil O (normally about 0.9) is smaller than the specific gravity (1) of water W, oil O will float on water W in oil tank  40  when filling oil O into oil tank  40  through oil access port  41 , and water W will be gradually forced out of oil tank  40  into the water pool  30  subject to the increasing of the filling amount of oil O. Because the volume of the water pool  30  is constant, filling oil O into oil tank  40  causes increasing of the water level in the water pool  30 . The invention further provides a spare water tank  50  at one side of the water pool  30  on the same level. A connecting pipe  51  is horizontally provided between the water pool  30  and the spare water tank  50  near the top side. When the water lever in the water pool  30  surpassed a predetermined high level, water W flows out of the water pool  30  into the water tank  50  through the connecting pipe  51  for further use. 
     Referring to  FIGS. 2D˜2F , when pumping oil O out of oil tank  40  through oil access port  41  for use, the amount of oil O is oil tank  40  is gradually reducing, the water level of water W in oil tank  40  is gradually increasing to lift oil O in the water tank  40 , and the water level of water W in the water pool  30  outside oil tank  40  is gradually lowering. At this time, the spared water can be guided from the water tank  50  into the water pool  30 . According to this embodiment, an auto water control system  52  which is formed of a water pump and a water level sensor is provided for detecting the water level of water W in the water pool  30  and automatically pumping water W out of the water tank  50  into the water pool  30  when the water level of water W in the water pool  30  dropped below a predetermined range. Therefore, the amount of water W in the water pool  3  and oil tank  40  is automatically adjusted subject to the amount of oil O in oil tank  40 , enabling water W to support the gravity weight of oil tank  40  and to keep oil tank  40  in balance. 
     As indicated above, the invention uses water W in the water pool  30  to isolate oil O from the ground earth and to support the gravity weight of the oil tank  40  and oil O contained in the oil tank  40  and to keep the oil tank  40  in balance by means of the physical characteristic that the specific gravity of oil O is smaller than water W. 
     In an application example of the present invention, the oil tank  40  in the water pool  30  has the depth of 24 meters. When the water tank  40  is filled up with oil O of specific gravity 0.9, the oil level of oil O in the oil tank  40  is 2.4 meters above the water level of water W in the water pool  30 . At this time, water W supports and sets off 90% of the pressure, and the oil tank  40  bears only the other 10% of the pressure. Therefore, when designing the material strength of the material for the oil tank  40 , it needs only to consider the pressure of oil O of depth 2.4 meters but not the pressure of oil O of depth 24 meters. When storing oil O of specific gravity 0.99, water W in the water pool  30  supports and sets off 99% of the pressure, and the water tank  40  bears only 1% of the pressure. Therefore, the invention breaks the conventional concept of constructing an oil tank with thick steel plate members. When constructing an oil tank of volume 130,000 square meters (Height 24M×Diameter 86M), it needs only to build up a concrete wall structure of Height 24M×Length 76M×Width 76M (saving about 10M×10M ground area). By means of binding reinforcing steel wire rods, setting molding forms, pouring concrete, and removing molding forms after setting of concrete, the desired wall structure  20  is built up, and the designed oil tank  40  can then be set in the water pool  30  thus formed. Further, using plastic or stainless steel plate members to construct the wall structure  20  instead of concrete accelerates the construction speed. 
     Because the oil tank  40  is set in the water pool  30  under the ground, it is not necessary to build up an additional retaining wall to protect the oil tank  40  against earthquake or any human beings&#39; destruction behavior. Because the oil tank  40  is set under the ground, it is safe against human beings&#39; destruction behavior, and storage oil O is free from the effect of the surrounding weather. Further, no lightning arrester or the like is necessary. In case of an earthquake, water W in the water pool  30  absorbs shock waves. Because the oil tank  40  bears a small pressure, the manufacturing cost of the oil tank  40  can be greatly reduced. 
       FIGS. 3A˜3F  show an alternate form of the present invention. According to this embodiment, the oil tank, referenced by  40   a  has an oil access port  41  at the top side, however the oil tank  40   a  has no port at its bottom side. Further, racks  43  are fixedly provided at the bottom wall of the oil tank  40   a  and supported on the top side of the bottom wall  31  of the water pool  30 , allowing water to flow through the bottom side of the oil tank  40   a , however storage oil O is prohibited from passing out of the oil tank  40   a  into water W in the water pool  30 . When filling storage oil O into the oil tank  40   a , water W is simultaneously filled into the water pool  30  by means of the control of the auto water control system  52 , and therefore the water level of water W in the water pool  30  and the oil level of oil O in the oil tank  40  are synchronously raised (see  FIGS. 3A˜3C ). On the contrary, when pumping oil O out of the oil tank  40   a  for use, the auto water control system  52  automatically pumps water W out of the water pool  30  into the water tank  50 , keeping the water pressure of water W in the water pool  30  in balance with the pressure of the oil tank  40   a  (see  FIGS. 3D˜3F ). 
     In additional to the aforesaid big scale design, the invention is also applicable for a relatively smaller scale design for use in, for example, a gas station. According to the third embodiment of the present invention shown in  FIG. 4 , a top cover  21  is covered on the wall structure  20  to close the water pool  30 ; the oil tank  40   b  is fixedly supported on a rack  43 ′ (or racks  43 ′) above the bottom wall  31  of the water pool  30  against floating of water W in the water pool  30 , having an oil access port  41 , which is comprised of an oil inlet pipe  41   a  and an oil outlet pipe  41   b  that are respectively upwardly extending from the top side of the oil tank  40   b  to the outside of the top cover  21 , and an air pipe  41   c  equipped with a relief valve (not shown) and upwardly extending to the outside of the water pool  30  for discharging of air when the air pressure in the oil tank  40   b  surpassed a predetermined level. The functioning of this embodiment is substantially similar to the aforesaid second embodiment with the exception that the water lever of water W in the water pool  30  surpasses the elevation of the top side of the oil tank  40   b , i.e., the oil tank  40   b  is constantly kept under water W. 
     Preferably, the oil tank  40   b  is mounted on the rack  43 ′ in a tilt angle, having a recessed water reservoir portion  44  at the lowest area on the inside and connected to an external water sensor  45  by a connecting line. In case water W leaks in the oil tank  40   b , leak-in water will be accumulated in the recessed water reservoir portion  44  and detected by the water sensor  45 , and a repair work can be quickly employed to prevent a further damage. In case the positive pressure type oil tank  40   b  has a damage and oil O leaks out of the oil tank  40   b , leaked oil O will float on water W, and the worker in the gas station can easily find the problem and take the necessary measure to eliminate the problem. Same as the aforesaid various embodiments of the present invention, this embodiment uses water W to isolate storage oil O from the ground soil, preventing pollution to the surrounding earth. Further, water W is used in the water pool  30  to support the oil tank  40   b  and the pressure of the storage oil O in the oil tank  40   b.    
     In general, the invention provides an underwater oil storage system, which uses water to support an oil tank and storage oil in the oil tank and to keep the oil tank in balance, presenting contact of storage oil with the ground earth. 
     Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.