Abstract:
The present invention is an apparatus with flexible membrane for oil storage and transportation, comprising of outer wall, installation opening, blocking cover, oil inlet, oil outlet and breathing orifice. The membrane is arranged in outer wall and fixed in the installation opening or the fixing part of outer wall. The rest of membrane is separated from outer wall. Valve and quick coupling are arranged in both oil inlet and oil outlet. The chamber made of membrane stores the oil in a sealed condition to let the breathing take place outside the membrane so as to prevent direct breathing of oil with air, reduce breathing loss, protect the environment, minimize oxidation of oil, prevent water from entering oil and improve the quality of oil. Also, it prevents oil vapor from mixing with air to improve the safety of storage and transportation as well as reduce the risk of fire and explosion. The flexible structure of the membrane facilitates the resistance to impact and other outer forces. According to the type of materials to be stored, different membranes can be chosen to store and transport liquid chemicals under low and ordinary pressure. This way of storage and transportation not only is environmental-friendly, safe and energy-saving, but also eliminates most of current oil vapor pollution.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an apparatus for storage and transportation of oil under low and ordinary pressure, and more particularly to oil storage and transportation technology. 
       BACKGROUND ART 
       [0002]    Currently, the transportation, storage and use of oil involve procedures including pipeline delivery, transportation of railway oil tank car and automobile oil tank car, tanker transportation, oil depot storage, gas station storage, etc. Since the floating-roof technology is adopted in the oil depot storage, over 90% breathing loss of oil is reduced. However, large and small tank breathing still happens in other procedures, resulting in evaporation loss and quality degradation of oil as well as environmental pollution. Also, large and small tank breathing may even lead to a high risk of fire and explosion. 
         [0003]    The breathing loss shall in the following be further described with gasoline as an example. 
         [0004]    According to  Gasoline and Oil Gas Emission Control Standard for Oil Product Sales Industry  by the Safety and Environmental Protection Bureau of China Sinopec Group Corporation, gasoline suffers around 1% loss during such procedures as railway oil tank and automobile oil tank transportation, oil tanker storage, gas station storage; annual consumption of gasoline in China is over 50 million tons, with a loss of more than 500,000 tons. As oil price exceeds 7000 yuan/ton at present, the cost amounts to more than 3.5 billion yuan, excluding the loss of apparatus (automobile) oil tank. 
         [0005]    Also, oil vapor pollutes environment. With most gas stations situated around urban areas, each certain unit of oil vapor is able to pollute air of 2000 times the volume of said oil vapor. Generally, during the process of transportation and sales, 50 million tons of gasoline will produce oil vapor of at least 5 times the volume of the gasoline, amounting to 340 million cubic meters. This means that 680 billion cubic meters of air will be polluted. Since oil vapor reacts with toxic gas in the air under the radiation of ultraviolet ray, more toxic pollutants will be produced and do more harm to human body as well as destroy the ozone layer (the oil vapor recycling reform in Beijing has been completed before the 2008 Olympic Gaines). Moreover, oil vapor increases the possibility of fire and explosion which is more destructive to ecological environment. 
         [0006]    Through large and small tank breathing, the water vapor in the air enters the storage tank and becomes liquid water when interior temperature decreases, which then adversely affects the quality of oil products. 
         [0007]    Besides gasoline, there are many other highly volatile products such as solvent oil, naphtha, aviation kerosene, light diesel oil, crude oil, etc. The evaporation of these oil products result in greater loss and more severe environmental pollution. 
         [0008]    Although some tank cars, gas stations and storage depots may recycle the oil vapor through adsorption, condensation and absorption or membrane separation, the recycling needs large investment, consumes energy resources and is not efficient. A set of recycling equipment for a storage depot is as expensive as 5˜15 million yuan and one for a gas station 0.3˜1 million yuan. According to the operation of installed equipment in Taiwan and the Mainland China, the recycling equipment has a high failure rate and a high maintenance fee; most of the recycled oil vapor is of no use but to be burnt. Moreover, oil vapor, mixed with air, can be of greater danger during transportation. Therefore, the fundamental and most efficient way to solve the problem is to deal with at the very beginning of the generation of oil vapor. 
       SUMMARY OF THE INVENTION 
       [0009]    In order to reduce the breathing loss during the transportation of oil products by storage depot tank, railway and road tank, gas station tank, equipment oil tank and other devices as well as solve the entailed problems related to environment, safety and quality, the present invention provides an apparatus with membrane for storage and transportation of oil. 
         [0010]    The general structure of the present invention comprises outer wall  1 , installation opening  3 , sealing cover plate  5 , oil inlet  6 , oil outlet  7 , access opening  13  and breathing orifice  10 . A membrane  2  is arranged inside outer wall  1  and fixed thereto at the installation opening  3 , oil inlet  6  or oil outlet  7 . The rest part of membrane  2  is separated from outer wall  1 . Oil inlet  6  and oil outlet  7  are arranged on the top or bottom of the tank, and both are provided with valve  15  and quick coupling  22 . A chamber  12  formed by membrane  2  seals and stores oil, while most part of membrane  2  expands or shrinks as a function of large and small tank breathing. 
         [0011]    In microscopic view, evaporation is the departure of liquid molecules from the liquid surface. When liquid molecules collide with each others during irregular movement, greater kinetic energy is obtained by some molecules. Given the kinetic energy of such molecules is larger than that needed to overcome the gravitation between liquid molecules to fly out of the liquid, these molecules will become vapor. 
         [0012]    Covering the liquid surface with a flexible membrane can block the liquid molecules from escaping, thus preventing the oil from contacting the air. Then oil breathing takes place outside the membrane and oil vapor will not be mixed with the air. By doing so, the storage and transportation of oil can be energy-saving, environmental-friendly and safe without risks of fire or explosion. Also, the membrane helps to maintain the quality of oil as it prevents oxidation and mixture with water. The flexible structure of the membrane will facilitate the oil&#39;s resistance to external forces like crash. 
         [0013]    By applying the present invention to transportation tank car, gas station oil tank and automobile tank, a closed storage and transportation (use) of oil can be achieved. By preventing direct breathing of oil and air, this way of storage and transportation eliminates oil vapor pollution and enhances safety. 
         [0014]    There are three elements contributing to the breakout of fire disaster in an oil depot, that is oil vapor, air and kindling material. When the said membrane is covered completely over the oil surface, the air is blocked from the oil. Therefore, the risk of fire danger is largely reduced and safety of tank car, oil tank and fuel tank greatly improved. 
         [0015]    When a flexible membrane is used to cover the oil surface during transportation and storage, breathing takes place outside the said membrane and the oil vapor is thus prevented from contacting air. Among others, the benefits of this invention are exemplified as follows: 
         [0016]    Direct breathing of oil vapor and air is prevented, thus protecting the environment. 
         [0017]    The transportation and storage conditions of oil in gas stations are improved so as to protect the personal health of attendant. 
         [0018]    Energy is saved as breathing loss is prevented. 
         [0019]    Safety is heightened by separating oil vapor from air. 
         [0020]    The quality of oil is maintained as the loss of volatile fraction is avoided. 
         [0021]    Oxidation is prevented from adversely affecting the oil quality, as oil is separated from air. 
         [0022]    The condensed water and rainwater in the air are prevented from contacting the oil to maintain oil quality. 
         [0023]    A membrane with strong anti-sticking capability may be used to reduce attachment of sediments for convenience to clean. 
         [0024]    A membrane with good corrosion resistance may be used to reduce repairing work and minimize chances of repairing. 
         [0025]    When several membranes are used, the tank can store several kinds of oil, with the volume of each kind of oil adjustable and transportation efficiency improved. 
         [0026]    The flexible membrane can improve the resistance to impact and prevent leakage in case of damage to tank body. 
         [0027]    The investment in modifying oil vapor recycling and bottom oil storage is reduced. 
         [0028]    The present invention can be well applied to ordinary storage tank, tank car and device oil tank. It prevents most of current oil vapor pollution and prevents sinking of floating roof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1  shows the general structural view of the present invention; 
           [0030]      FIG. 2  shows the structure of composite membrane of the present invention; 
           [0031]      FIG. 3  shows in detail the structure of the composite membrane of the present invention; 
           [0032]      FIG. 4  shows the structure of fixing the membrane on the installation opening with bolts; 
           [0033]      FIG. 5  shows the structure of fixing membrane on flanges of oil inlet and outlet with bolts; 
           [0034]      FIG. 6  shows the structure of fixing membrane with adhesive; 
           [0035]      FIG. 7  shows the structure of fixing membrane with bolts; 
           [0036]      FIG. 8  shows the structure of fixing membrane using bolts and adhesive; 
           [0037]      FIG. 9  shows the structure of Embodiment 1 (Tank Car  1 ); 
           [0038]      FIG. 10  shows the structure of Embodiment 2 (Tank Car  2 ); 
           [0039]      FIG. 11  shows the structure of Embodiment 3 (Horizontal Tank); 
           [0040]      FIG. 12  shows the structure of Embodiment 4 (Device Oil Tank  1 ); 
           [0041]      FIG. 13  shows the structure of Embodiment 5 (Device Oil Tank  2 ); 
           [0042]      FIG. 14  shows the structure of Embodiment 5 (Device Oil Tank Equipped with Oil Gun); 
           [0043]      FIG. 15  shows the structure of Embodiment 6 (Membrane Coverage Replacing Inner Floating-roof Oil Tank); and 
           [0044]      FIG. 16  shows the structure of Embodiment 6 (Membrane Coverage Replacing Outer Floating-roof Oil Tank). 
       
    
    
     LIST OF REFERENCES 
       [0045]      1 —Outer Wall;  2 —Membrane;  3 —Installation Opening;  4 —Fixed Part of Membrane;  5 —Sealing Cover Plate;  6 —Oil Inlet;  7 —Oil Outlet;  8 —Output Oil Pump;  9 —Output Oil Pump Cover;  10 —Breathing orifice;  11 —Safety Valve;  12 —Oil Storage Chamber;  13 —Access Opening;  14 —Leakage Detection Sensor;  15 —Valve;  16 —Insulation Layer;  17 —Floater;  18 —Discharge Hose;  19 —Discharge Pipe;  20 —Oil Tank Filling Pipe;  21 —One-way Valve;  22 —Quick Coupling;  23 —Top Access Cover Plate of Oil Tank;  24 —Oil unloading port of Oil Tank;  25 —Quick coupling of Oil Gun;  26 —Oil Gun;  27 —Oil Gun Air Port;  28 —Separate Space;  29 —Sewage drain pipe ;  30 —Rainwater Pipe;  31 —Rainwater Exit;  32 —Bolt;  33 —Conductive Gasket;  34 —Liquid Level Sensor;  35 —Flange;  36 —Conductive Adhesive;  37 —Inner Layer of Composite Membrane;  38 —Middle Layer of Composite Membrane;  39 —Outer Layer of Composite Membrane;  40 —Access Valve. 
       DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0046]    The present invention will be further described in the following embodiments with reference to the drawings. 
       Embodiment I 
       [0047]    Tank Car  1  (membrane fixed on the bottom and top): as shown in  FIG. 9 , comprising outer wall  1 , installation opening  3 , sealing cover plate  5 , oil inlet  6 , oil outlet  7 , access opening  13  and breathing orifice  10 . Oil inlet  6  is arranged on the top of the tank and oil outlet  7  in the bottom of the tank. Membrane  2  is arranged inside outer wall  1 , while insulation layer  16  is arranged between outer wall  1  and membrane  2 . Insulation layer  16  clings to outer wall  1 , and membrane  2  is fixed on installation opening  3  and flange  35  of bottom oil outlet  7 . The rest part of membrane  2  is separated from insulation layer  16 . Valve  15  and quick coupling  22  of tank car are arranged in both oil inlet  6  and oil outlet  7 . 
         [0048]    Under normal operation temperature, membrane  2  is quite flexible with resistance to folding, corrosion of oil and impurities in the oil and oil temperature; the membrane is also non-inflammable, airtight and with anti-static quality. Such requirements of the membrane can be satisfied by modifying (e.g. use black lead or carbon black to increase electric conduction) such oil-proof materials as fluoroplastics, polyurethane, nitrile rubber, ethylene-vinyl alcohol copolymer, polyvinylidene chloride, nylon and silastic or by forming a composite membrane(e.g. Multi-layer Composite Co-extrusion Membrane) together with other materials (e.g. polyethylene).  FIG. 3  shows the structure of composite membrane consisting of inner layer  37 , middle layer  38  and outer layer  39  Inner layer  37  is resistant to corrosion of oil and impurities and is anti-static; middle layer  38  can block the air and outer layer  39  is resistant to wear, heat, water, ozone and ultraviolet rays. A composite membrane can be made of 3, 5, 7 or 9 layers of membranes or can be a single layer of membrane, for example modified fluorplastic membrane, which embodies all the said features. Membrane materials can be chosen based on the type of materials to be stored. 
         [0049]    If the material to be stored is either chloride nor ethers material, it is recommend using modified fluorplastic membrane or waxing cloth made by for example fiberglass cloth impregnated by modified fluorine coating. When storing water-free oil product, ethylene-vinyl alcohol copolymer, polyurethane, nitrile rubber and modified nylon can be used as the inner layer, ethylene-vinyl alcohol copolymer, polyvinylidene chloride can be used as middle layer to block the air, and modified polythene with carbon black can be used as the outer layer to resist wear, flaming, water, ozone and ultraviolet rays. 
         [0050]    Outer wall  1  of tank car is made of metal or plastic materials with capability of resistance to static electricity (electric conduction). 
         [0051]    Membrane  2  can be fixed in installation opening  3  and oil outlet  7  using bolts or adhesive or a combination thereof, as shown in  FIGS. 4 and 5 . 
         [0052]    If an adhesive is used, membrane  2  should be fixed in installation opening  3  and outer wall  1  around oil outlet  7  using conductive adhesive  36  which is connected to the inner layer  37  of membrane  2  (anti-static layer) and the anti-static layer of outer wall  1  to eliminate static electricity, as shown in  FIG. 6 . 
         [0053]    If a bolt is used, the membrane should be fixed with bolt  32  and conductive gasket  33  so as to eliminate static electricity, as shown in  FIG. 7 . 
         [0054]    If a combination of adhesive and bolt is used, membrane should be fixed using bolt  32 , conductive gasket  33  and conductive adhesive  36  concurrently, as shown in  FIG. 8 . 
         [0055]    If installation opening  3  is fixed with a bolt, membrane  2  is fixed on the installation opening  3  using bolt  32  and conductive gasket  33 ; conductive gasket  33  can be of either single layer or double layer and is connected to the inner layer  37  (anti-static layer) of membrane  2  as well as the anti-static layer of outer wall  1  so as to eliminate the static energy, as shown in  FIG. 4 . 
         [0056]    If flange  35  of oil outlet  7  is fixed using a bolt, membrane  2  is fixed in flange  35  of oil outlet  7  using  32  and conductive gasket  33 ; conductive  33  can be either single layer or double layer and is connected to the inner layer  37  (anti-static layer) of membrane  2  as well as the anti-static layer of outer wall as so to eliminate the static energy, as shown in  FIG. 5 . 
         [0057]    The volume of chamber  12  formed by membrane  2  is not smaller than that of outer wall  1 . The force membrane  2  receives is sufficiently transferred to outer wall  1 , making membrane  2  receive a small force from the time it is empty till its volume reaches safety volume. 
         [0058]    When oil, through quick coupling  22  of tank car and valve  15 , flows from oil inlet  6  and flange  35  into membrane  2  and oil storage chamber  12 , membrane gradually expands till it clings to insulation layer  16 , thus transferring the force to outer wall  1 . The air between membrane  2  and insulation layer  16  is discharged through breathing orifice  10 . 
         [0059]    When oil flows out of membrane  2  through flange  35 , valve  15  and oil outlet  7 , membrane  2  gradually shrinks and the air enters the space between insulation layer  16  and membrane  2  through breathing orifice  10 . 
         [0060]    To oil inlet  6  and oil outlet  7  are provided valve  15  and quick coupling  22  of tank so as to achieve closed oil unloading and receiving. During the whole process of storage, membrane  2  covers the oil surface to prevent volatilization of oil so as to achieve closed storage and transportation of oil. 
         [0061]    When the temperature of oil exceeds the boiling point of fractions of oil product, the formed oil vapor can be stored inside membrane  2  under safety pressure. The combination of membrane and outer wall  1  can withstand saturated vapor pressure under the highest environment temperature to keep balance between vapor and liquid. When temperature declines, the saturated vapor condenses to liquid again. 
         [0062]    In top installation opening  3 , safety valve  11  is arranged to discharge the oil vapor produced by fractions with low boiling point when the pressure is excessively high. As the discharged oil vapor contains no air, its treatment is quite safe and convenient. 
         [0063]    Insulation layer  16  is arranged to reduce the effects of sunshine and air temperature on tank temperature. The necessity of arrangement of insulation layer  16  is based on the differences of sunshine and temperature in the area as well as needs of oil product. When it is unnecessary to keep the temperature, the insulation layer  16  can be omitted. 
         [0064]    The shallow soil temperature in China is normally under 20° C. If oil depot is built underground, measures taken to insulate heat can prevent oil temperature from reaching its boiling point. 
         [0065]    If a variety of oils (e.g. different grades of gasoline and diesel oil) need to be transported at the same time, several installation openings  3  can be provided in one tank car to install several membranes  2  and oil outlets  6 / 7 . The volume of each chamber can be adjusted as required. 
         [0066]    A leakage detection sensor  14  can be arranged between insulation layer  16  (outer wall  1  if insulation layer  16  is not arranged) and membrane  2  to detect whether there is any oil leakage. 
         [0067]    Liquid level sensor  34  can be arranged inside oil storage chamber to detect the liquid level, measure the volume of oil and prevent overflow of oil. 
         [0068]    Access opening  13  is arranged on the top of tank. Besides maintenance, the access opening  13  allows personnel to operate inside the tank to unload any residual oil as well as observe loading process when receiving oil so as to avoid over-loading. 
       Embodiment II 
       [0069]    Tank Car  2  (membrane fixed in the bottom): as shown in  FIG. 10 , comprising outer wall  1 , oil inlet and outlet  6  (a combination of oil inlet  6  and oil outlet  7 ) in the bottom of car and breathing orifice  10 . Membrane  2  is arranged inside outer wall  1 , and insulation layer  16  is arranged between outer wall  1  and membrane  2 , with insulation layer  16  clung to outer wall  1  and membrane  2  fixed in the flange  35  of oil inlet and outlet  6 . The rest part of membrane  2  is separated from insulation layer  16 . In oil inlet and outlet  6 , valve  15  and quick coupling  22  of tank car are arranged. 
         [0070]    In installation opening  3 , a safe discharge system is arranged consisting of safety valve  11 , floater  17 , discharge hose  18  and discharge pipe  19 . When the pressure is over high, the system discharges oil vapor produced by fractions of low boiling point, with floater  17  keeping safety valve  11  floating on the liquid surface when oil vapor is produced. Since the discharged oil vapor contains no air, its treatment is safe and convenient. 
         [0071]    The fixing manner of membrane  2  in oil inlet and outlet  6  is the same as that of membrane  2  in oil outlet  7  in Embodiment I. 
         [0072]    Other structures are arranged similar to or the same as those described in Embodiment I. 
         [0073]    As for a newly-built tank car, access opening  13  can be arranged in oil inlet and outlet  6  and flange  35  of oil inlet and outlet  6  can be arranged on access opening  13 . In this case, the whole membrane  2  can be taken out through access opening  13  for maintenance, while breathing orifice  10  still remains on the top, facilitating oil breathing. 
       Embodiment III 
       [0074]    Horizontal Oil Tank: as shown in  FIG. 11 , comprising outer wall  1  of tank, installation opening  3 , blocking cover  5 , oil inlet  6 , oil outlet  7 , access opening  13 , and breathing orifice  10 . Oil inlet  6  and oil outlet  7  are both arranged on top of the tank. Membrane is arranged inside outer wall and fixed in installation opening  3 , with the rest part of membrane  2  separated from outer wall  1 . Valve  15  and quick coupling  22  of tank car are arranged on both oil inlet  6  and oil outlet  7 . 
         [0075]    In the lower part of oil outlet  7 , oil-out pump  8  and oil-out pump cover  9  are arranged. Oil-out pump can also be arranged outside oil tank. 
         [0076]    Outer wall  1  is made of metal or plastic materials with a capability of resistance to static electricity (electric conductivity). 
         [0077]    If necessary, insulation layer  16  can be arranged in the same manner as in Embodiment I. 
         [0078]    The fixing manner of membrane  2  in installation  3  is the same as those described in Embodiment 2. 
         [0079]    Other structures are arranged similar to or the same as those described in Embodiment I. 
       EMBODIMENT IV 
       [0080]    Apparatus Oil Tank  1  (oil-out pump arranged inside oil tank): as shown in  FIG. 12 , comprising outer wall  1  of oil tank, oil inlet and outlet  6 , oil outlet  7 , breathing orifice  10 , oil filling pipe  20  and top access cover plate  23  (equivalent to installation opening  3  in function). Oil inlet  6  and oil outlet  7  are both arranged in bottom of oil tank. Membrane  2  is arranged inside outer wall  1  and fixed in the bottom of oil-out pump  8 , the contacting areas of oil inlet  7 , oil-out pump cover  9  and oil unloading port  24  with oil tank. The rest part of membrane  2  is separated from outer wall  1 . One-way valve  21 , safety valve  11  and quick coupling of oil tank  22  are arranged in oil filling pipe  20  of the tank, and oil-out pump  8 , oil-out pump cover  9  and oil unloading port  24  are arranged in the bottom of oil tank. 
         [0081]    Membrane  2  is fixed with bolt in the bottom of oil-out pump  8  and the membrane fixing section  4  of top access cover plate  23 ; the membrane fixing section  4  around oil filling pipe  20  on top of the tank, as shown in corresponding part of Embodiment I. 
         [0082]    See Embodiment I for materials of membrane  2 . 
         [0083]    Conventional oil gun needs adaption to facilitate oil filling of the tank. As shown in  FIG. 14 , conventional oil filler is engineered into quick coupling  26  and discharge pipe is engineered into air port switch  27 . 
         [0084]    During the process of filling apparatus oil tank with oil, the tank is connected with oil gun  35  through quick coupling  26  of oil gun and quick coupling  22  of oil tank, with air port  27  of oil gun reaching into outer wall  1  through breathing orifice  10 . A predetermined amount of oil can be filled, and oil can be filled to safety volume of tank through automatic control. When the filled oil reaches safety volume, the membrane seals air port  27  of oil gun and stops filling. 
         [0085]    When oil enters membrane  2  of oil tank from quick coupling  22  of oil tank through one-way valve, membrane  2  expands, which discharges the air between membrane  2  and outer wall  1  through breathing air  10 ; when oil flows out through oil outlet  7 , membrane  2  gradually shrinks and air enters the space between membrane  2  and outer wall  1  through breathing orifice  10 ; membrane  2  covers the oil surface all the time to prevent volatilization. 
         [0086]    Oil-out pump cover  9  is arranged to prevent membrane from blocking oil-out pump and oil inlet  6  and keeps oil-out pump soaked in oil to reduce its temperature. Oil-out pump cover  9  is of a grid form. 
         [0087]    After oil is discharged through oil unloading port  24 , top access cover plate  23  of oil tank can be opened so as to repair oil-out pump  8 . 
         [0088]    When pressure in oil tank is over high, safety valve  11  starts to work in order to decrease pressure. 
         [0089]    When the apparatus (automobile) is crashed resulting crack on the oil tank, the membrane can prevent oil from spilling out to avoid causing fire and explosion of vehicle. 
       Embodiment V 
       [0090]    Apparatus Oil Tank  2  (oil-out pump outside the oil tank): as shown in  FIG. 13 , comprising outer wall  1  of oil tank, oil inlet  6 , oil outlet  7 , breathing orifice  10  and oil filling pipe  20  of oil tank. Oil inlet  6  and oil outlet  7  are in the bottom of oil tank. Arranged inside outer wall  1 , membrane  2  is fixed in oil inlet  6  near the tank bottom as well as membrane fixing section  4  around the oil filling pipe  20  on top of the tank. The rest part of membrane  2  is separated from outer wall  1 . One-way valve  21 , safety valve  11  and quick coupling  22  of oil tank are also arranged in oil filling pipe  20  of oil tank. Access opening  13  and access valve  40  are also arranged in oil-out pump  8  which is in the exterior of oil tank. 
         [0091]    After closing access valve  40 , oil pump  8  can be repaired through access opening  13 . 
         [0092]    Membrane  2  is fixed with adhesive in oil inlet  6  and membrane fixing section  4  around oil filling pipe  20  of oil tank, as described in Embodiment I. 
         [0093]    Other structures are arranged similar to or the same as those described in Embodiment I. 
       Embodiment VI 
       [0094]    Membrane cover replacing inner floating-roof storage tank: as shown in  FIG. 15 , comprising outer wall  1  of oil tank, oil inlet  6  and oil outlet  7 . Arranged inside outer wall  1 , membrane  2  covers the upper part of outer wall  1  of storage tank and is fixed at membrane fixing section  4  in the lower part of outer wall  1 . The rest part of membrane  2  is separated from outer wall  1 . Valve  15  and quick coupling  2  are arranged on both oil inlet  6  and oil outlet  7 . Sewage drain pipe  29  is arranged in the bottom of storage tank and access opening  13  at the edge of tank bottom. Membrane  2  completely covers oil product surface and separates oil product from air with air outside the membrane breathing through breathing orifice  10 . 
         [0095]    Membrane is fixed with adhesive and bolt in membrane fixing section  4  on outer wall  1 . See corresponding part in Embodiment I for details. 
         [0096]    For details of membrane  2  materials and composite membrane structure, see Embodiment I. 
         [0097]    When oil storage chamber  12  is large enough, a composite membrane of 3-5 layers of membranes can be used. The space between membranes are made into separate space  28 , wherein leakage detection sensor  14  is arranged to improve reliability and detection positioning ability for repairing, as shown in  FIG. 2 . When oil product needs insulation to maintain its temperature, separate space  28  is filled with flexible foaming materials (e.g. polyurethane) and inert gas (e.g. nitrogen); when insulation is not needed, separate space  28  is vacuumed. 
         [0098]    Inside the tank, a safe discharge system is arranged consisting of safety valve  11 , floater  17 , discharge hose  18 , discharge pipe  19 . When pressure is over high, said system discharges oil vapor and floater  17  enables safety valve  11  to stay floating on the liquid surface when oil vapor is produced. Since the discharged oil vapor contains no air, it is safe and convenient to burn it. 
         [0099]    Valve  15  and quick coupling  22  are arranged in both oil inlet  6  and oil outlet  7 , to achieve sealed oil unloading and receiving. During the process of oil storage, membrane  2  always covers the oil surface to prevent volatilization of oil. Thus sealed storage and transportation of oil is achieved. 
         [0100]    Sewage drain pipe  29  is used to blow off sewage contained in oil product. It is unnecessary to arrange sewage drain pipe  29  if oil being stored does not contain sewage. 
       Embodiment VII 
       [0101]    Membrane coverage replacing outer floating-roof storage tank: as shown in  FIG. 16 , comprising existing outer wall  1  of storage tank, oil inlet  6  and oil outlet  7 . Arranged inside outer wall  1 , membrane  2  is fixed in vertical wall of outer wall  1  as well as membrane fixing section  4  in the bottom corner. The rest part of membrane is separated from outer wall  1 . Valve  15  and quick coupling  22  are arranged on both oil inlet  6  and oil outlet  7 . Sewage drain pipe  29  is arranged in the bottom of tank, and access opening  13  is arranged in peripheral edge of bottom tank. Membrane completely covers oil surface, and separates oil product from air with air outside the membrane taking part in breathing through the open storage tank top. 
         [0102]    Rain collecting pipe  30  and outfall  31  are arranged in peripheral edge of tank bottom to drain the rain water outside membrane  2 . Rain collecting pipe is a sieve pipe with drilled holes. 
         [0103]    Other structures are arranged similar to or the same as those described in Embodiment I. 
         [0104]    The oil storage apparatus of the present invention also applies to storage and transportation of products other than oil products in low and ordinary pressure, such as methanol, ethanol and other liquid chemicals suitable for storage under low and ordinary pressure. It is also suitable for water transportation. 
         [0105]    The preferred embodiments of the present invention have been set forth in the above passages with drawings and examples. Obviously, the present invention is not limited to the said embodiments. Any modification within the scope of the present invention is not excluded from the protection scope of this invention.