the present invention will be further described in the following embodiments with reference to the drawings . tank car 1 ( membrane fixed on the bottom and top ): as shown in fig9 , 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 . 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 ). fig3 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 . 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 . outer wall 1 of tank car is made of metal or plastic materials with capability of resistance to static electricity ( electric conduction ). membrane 2 can be fixed in installation opening 3 and oil outlet 7 using bolts or adhesive or a combination thereof , as shown in fig4 and 5 . 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 fig6 . 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 fig7 . 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 fig8 . 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 fig4 . 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 fig5 . 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 . 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 . 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 . 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 . 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 . 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 . 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 . 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 . 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 . 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 . 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 . 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 . tank car 2 ( membrane fixed in the bottom ): as shown in fig1 , 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 . 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 . 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 . other structures are arranged similar to or the same as those described in embodiment i . 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 . horizontal oil tank : as shown in fig1 , 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 . 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 . outer wall 1 is made of metal or plastic materials with a capability of resistance to static electricity ( electric conductivity ). if necessary , insulation layer 16 can be arranged in the same manner as in embodiment i . the fixing manner of membrane 2 in installation 3 is the same as those described in embodiment 2 . other structures are arranged similar to or the same as those described in embodiment i . apparatus oil tank 1 ( oil - out pump arranged inside oil tank ): as shown in fig1 , 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 . 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 . conventional oil gun needs adaption to facilitate oil filling of the tank . as shown in fig1 , conventional oil filler is engineered into quick coupling 26 and discharge pipe is engineered into air port switch 27 . 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 . 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 . 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 . 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 . when pressure in oil tank is over high , safety valve 11 starts to work in order to decrease pressure . 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 . apparatus oil tank 2 ( oil - out pump outside the oil tank ): as shown in fig1 , 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 . after closing access valve 40 , oil pump 8 can be repaired through access opening 13 . 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 . other structures are arranged similar to or the same as those described in embodiment i . membrane cover replacing inner floating - roof storage tank : as shown in fig1 , 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 . membrane is fixed with adhesive and bolt in membrane fixing section 4 on outer wall 1 . see corresponding part in embodiment i for details . for details of membrane 2 materials and composite membrane structure , see embodiment i . 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 fig2 . 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 . 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 . 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 . 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 . membrane coverage replacing outer floating - roof storage tank : as shown in fig1 , 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 . 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 . other structures are arranged similar to or the same as those described in embodiment i . 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 . 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 .