US2014264A - Sealing device for storage tanks - Google Patents

Description

Sept. ,10, 1935. T J; c. PATRICK 5 2,014,264

` sEALING DEVICE FOR STORAGE TANKS A Filed Sept. 29, 1930 2 Sheets-Sheet 1 lill:

Sept. l0, 1935.

J. C. PATRICK SEALING DEVICE FOR STORAGE TANKS Filed Sept. 29, 1930 2 Sheets-Sheet 2A 72067212072' fase/2% Patented sept. 1o, 1935 lUNITED vsTATlzs PATENT OFFICE sEALlNG EvIcE Foa s'roaAGE TANKS Joseph C. Patrick, Kansas City, Mo. Application September 29, 1930,*'Seria1 No. 485,231`

1o claims. (ci. zzo-26)' The present invention relates to improvements in sealing devices, more particularly intended for use with storage tanks for volatile liquids such as petroleum oils, solvent liquids, and the like, and

5 for materials for use in the construction of suchv seals.

In order that the invention may be fully under-,- stood, it is described herein in connection with certain' specieembodiments thereof, illustrated l by the accompanying drawings, in which:

Figure l is a sectional view of a tank or container provided with a form of sealing device in accordance with the present invention;

, Fig. 2 is a broken sectional View through a storl age tank provided with a modified form of sealing device in accordance with the present invention; and Fig. 3 is a broken section View through a modifled, semi-rigid form of construction in accord- 20 ance with the present invention; and v Fig. 4 is an enlarged sectional view of a portion of the construction shown in Fig. 3;

Fig. 5 is a sectional view through a further mod-- ication of a semi-rigid embodiment of my inven- 25 tion; and

Fig. 6 is a horizontal sectional View of the form of construction shown in Fig. 5.

A sealing device in accordance with the present invention is illustrated in a simple form in Fig. l 30 of the drawings. As shown in this figure, the numeral l0 designates a tank or container in which a supply of a Vvolatile liquid, such as gasoline, crude petroleum, benzol, alcohol, or other Volatile solvent is stored. A movable seal or dia- 35 phragm for the tank or container is provided by the gas-filled, laterally expansible chamber or balloon l l, suitably formed of a flexible, impervious and chemicallyresistant material, preferably of the character hereinafter more fully set forth.

40 The balloonor chamber II is provided with an inilation pipe I2 having a suitable valve I3, .through which the iiexible container can be filled with gas. Although air may be employed, I prefer to use an inert gas which does not burn or 45 support combustion, such as carbon dioxide, nitrogen, helium or the like. Ordinarily, I prefer to use a gas, such as carbon dioxide, heavier than air so that in the event of leakage, or of breakagenof the sealing chamber in case of re or the like, the' 50 inert gas will settle and form a re damping or extinguishing blanket upon the surface of the material in the tank.

I In the preparation of the exiblematerial for the construction of the sealing member, it is 55 necessary to employ a exible material which will their physical properties.

adequately satisfy the very severe requirements of continuous use. It must be impervious to the gases or vapors of the materials contained in the tank, as well as to moisture and other constituents of the atmosphere. It must be substantially 5 wholly unaffected bythe liquid in the'tank and by the gases and vapors given off thereby, both chemically and physically. It must be ductile, laterally extensible, resistant to abrasion, and highly flexible, so as to be capable of an almost indefinite 10 amount of ilexure. It must not age or become brittle on the one hand, or soften and swell on the other hand. Materials proposed hitherto for the surface, such as rubber, hardened or tanned gelatin, casein compounds, bituminous or resinous mixtures or the like have been found entirely inadequate, as they fail to satisfy a considerable number or all of the `essential requirements.

For example, the use of rubber or rubber-impregnated fabrics has been suggested. However, rubber or fabrics impregnated with rubber or compounds consisting predominantly of rubber are rapidly attacked by many liquids and by gases or vapors given oi by them, being dissolved or caused to swell with a marked deterioration in Thus, when used in connection with oils or petroleum products,'par ticularly those containing volatile constituents such as crude oil, gasoline and the like, the rubber is rapidly attacked, partially dissolved and caused to swell and rapidly loses its sealing capacity, its resistance to exure and to abrasion. Furthermore, when used with many petroleum products which contain sulfur compounds or which evolve sulfur-containing vapors of hydrogen sulde, sulfur-dioxide, or the like, the rubber is attacked and caused to age and crack. Other solvent liquids and their vapors likewise vigorously attack rubber and compounds consisting predominantly thereof.

I have found that the requirementsl for the 40 material of a seal of the character described are fully satisfied by the use of a plastic material hereinafter described, as a lm or sheet-forming material or as an impregnating material for a fabi'ic to be used in the construction thereof. 45 This plastic is preferably formed of an organic compound consisting mainly of sulfur combined with organicradicals of the general formula ,CnHzm and which may beA suitably produced by the reaction of polysuldes on derivatives of 50 methylene and .various oleiins such as the dihalides of methylene, ethylene, propylene, butylene and the like, formaldehyde and the homolo- Agous aldehydes, or mixtures thereof. In general,

I prefer to use such polysulde compounds having a soft, rubbery character; these being in general those in which the polysuliide sulfur is.

present in proportion corresponding to at least Sz and preferably to Ss or higher.

In preparing the material for the production of the seal, I prefer to employ a plastic material of the character hereinbefore set forth, or a compound consisting predominantly thereof. In forming such a compound, I may employ various softening agents such as fatty acids and their metallic soaps, small quantities of rubber, of organic sulfur compounds such as a phenol sulfur compound, elemental sulfur, organic nitrogenous compounds, waxes, sulfur carriers, such as lead oxide, zinc oxide and the like together with fillers or pigments such as carbon black, Whiting, clay and the like, or mixtures thereof. The compound is prepared in any suitable mixing device, preferably on rubber milling rolls, and is formed into a sheet or film or preferably rolled or frictioned into the body of a suitable fabric or textile, and is subsequently stabilized by heating to a temperature above 200 F. and preferably of about 287 F.

'A suitable compound for the 4preparation of the sealing material in accordance with the present invention may be prepared as follows:

50 parts' of a soft ethylene polysulde plastic is broken down and softened on mill rolls of the type ordinarily used in mixing rubber. this is added 1 part by weight of the phenol-sulfur compound above referred to; 3 parts rubber, 2.5 parts zinc oxide? 0.125 parts diphenylguanidine; 1 part stearic acid; 0.5 parts paraiiin wax; 0.125 parts sulfur and 5 parts carbon black. I'he compound is milled until thoroughly mixed and forms a smooth, black, highly ductile, plastic mass, which is then sheeted or rolled into a thin film onfa fabric by suitable calendering or frictioning rolls, impregnating and 'coating the fabric and forming a smooth, impervious and highly flexible sheet. The film or coated fabric is stabilized by heat treatment, for example, by heating to a temperature of 287 F. for a period of 40 to minutes. The finished material vis lcut and united to form a container or balloon of the desired shape in any suitable manner. For example, in case a sheet or film of the material is employed, the edges of the properly cut sheets may be lapped and pressed together in a heated press at say 250 to 287 F. to form an impervious union. In the case of a coated or impregnated fabric, the cut fabric is preferably lapped and sewn together and the lapped edges subjected to similar treatment in order to vcause an impervious union between the films of plastic material on the fabric. In this Way, a completely impervious, tight sealing bag or container may be prepared.

A sealing member thus formed, with a continuous film or skin of the organic polysuliide plastic as hereinbefore described, is substantially completely impervious to gases and vapors and is unaffected physically or chemically by the vapors or gases with which it is likely to come in contact in use in connection with the storage thereof. Thus it is unaffected by hydrocarbon vapors or gases, such as those from crude petroleum, volatile petroleum distillates, coal tar products, benzols, toluols and organic solvent liquids in general. It is likewise unaffected by, and

impermeable to, water, Water vapor, oxygen, car- Tov ample above given may be modified, it being desired, however, to retain the olefin polysulfde plastic as the predominant constituent thereof. Thus, if a black composition is not desired, the

carbon black may be omitted, and other fillers, 5

i are likely to be encountered, such as in the storage of carbon disulfide. The fabric or textile to which the compound is applied may be a cotton, linen or other textile fabric; but in circumstances under which re danger is likely to be encoun- 15 tered, I prefer to employ woven asbestos fabric, upon which the plastic compound is milled or sheeted as hereinbefore described, 4or a suitable flre-proofed textile. I may likewise use a composite protective rcoating or film; for example, a 20 fabric having the olen polysulfide plastic sheeted or frictioned upon one side thereof and a rubber compound applied to the opposite side, preferably to the side which is to be on the interior of the sealing member. Rubber is parg ticularly adaptable for such use when the interior of the sealing member is to be charged with carbon dioxide, nitrogen or other inert gases, by which the rubber is protected from oxidation.

The sealing member, formed as hereinbefore 30 described, is iniiated with an interior superatmospheric pressure of the selected gas sufficient to distend it to the desired extent, so that it will contact with the side walls of the tank ID, and in moving up and down in the tank in accordance with changes of level therein, or in accordance Cil -with expansion or contraction of the vapors on the surface of the liquid, will adjust itself automatically to irregularities in the side walls of the tank and maintain an adequate sealing contact 40 therewith. In case other means of inflation of the sealing member are not available, suiiicient quantities of a solution of a suitable carbonate, such as sodium or potassiumv carbonate or bicarbonate, and of a dilute acid such as dilute sul- 4,- furic or dilute hydrochloric acid may be charged into the interior of the sealing member I! through the conduit I2 to produce the necessary quantity of carbon dioxide gas for iniiation by their reaction within the sealing member. 50

Although the form of sealing member shown in Fig. l is satisfactory, particularly in smaller tanks, say up to 4 feet in diameter, for larger tanks, I prefer to modify the form of sealing member, preferably flattening it so that it assumes an approximately elliptical cross section. A simple form of construction of this type is illustrated in Fig. 2, in which the numeral I5 indicates the tank, and numeral I6 the sealing member, formed as an inflated bag or balloon of 60 approximately elliptical cross section, provided with a valved inflating tube I1. In order that the sealing member IB may be caused to maintain the desired shape and to follow changes in volume of the liquid and vapors in the tank I5, a metallic ring I8 is placed upon it, the outer diameter of the ring beingf somewhat less than the inner diameter of the tank. In addition, if desired, a metallic disk I9 is placed on the upper surface of the sealing member I6, approximately centrally thereof. The ring I8, and the disk I9, when the latter is employed, may be made of suitable Weight, depending upon the diameter of the tank, to insure the sealing and following action of the member I6. If desired, the ring I8 75 may be provided with spring-pressed pusher rods 20, contacting with the interior walls of the tank, by which undue lateral displacement of the ring is avoided.

In place of a completely flexible distended sealing member, I may, particularly in very large tanks such as those' used for storage of crude petroleum, gasoline and the like, employ a semirigid construction, in which the central or body portion of the sealing member is of rigid construction, provided marginally at its contacting surfaces with a laterally expansible, flexible sealing portion. Such a form of construction is shown in Figs. 3 and 4.l In this form of construction the numeral designates the side walls of the tank and the numeral 26 the sealing membustible liquids, the'material of the plates may be nre-proofed to a greater' or less extent by impregnation with suitable materials, such as alkali metal silicates, ammonium salts, such as ammonium phosphate, ammonium sulfate and vthc like, soluble tungstates, such as ammonium or sodium tungstate, bor'tes, or other nre-proofing agents. I may likewise employ porous asbestos boards for the construction of these plates. The plates are then impregnated, or preferably coated, with a continuous nlm of a suitable plastic material, preferably one such as the organic polysuliide material hereinbefore described lfor use in the treatment of the sealing member as shown in Figs. 1 and 2. A continuous coating of such material is applied as a sealing coating to the exterior surfaces of the plates 21 and 28, and.

as shown in enlarged sectional View in Fig. 4, in connection with the upperl sealing plate 21. The sheath or coating of the organic polysulde plastic material, designated by the numeral 30,is continued around the edges of the plates as at 3| and the inner side as at 32. l

Around the marginal edges of the plates,` the expansible sealing member 33 is secured thereto, forming with the plates 21 and 28 a completely enclosed chamber. The expansible sealing member 33 lis suitably formed of textile material impregnated or coated with olefinfpolysuliide plastic, of the same character as that hereinbefore described for use' in connection with the sealing ing on the outer surface of the' plate and on the surfaces of the fabric forming the sealing member 33 are completely united to form an impervious seal.

It is apparent that the plates 21 and 2li, with the marginal sealing member 33 constitute an enclosed, laterally expansible chamber, anda suitable means, such as the valved pipe 35 is provided for filling this chamber and inating the sealing member 33, causing it to contact with the seal and the walls of the chamber, in the same manner as inthe forms of construction previously set forth. 5

Figs. 5 and 6 illustrate Ia further modied form of construction of cellular type, having a central rigid portion formed by the upper plate 40 and lower plate 4l, to which is marginally secured the expansible sealing member 42. In this form 10' of construction, the upper and lower sealing plates of the central rigid portion are similar` to the upper and lower sealing plates of the form of construction shownin Fig. 3, and in addition, partitions 42a of similar material are provided 1'5 between the plates 40 and .4l to divide the spa-ce into cells. As illustrated, these partitions are circular in section, although any suitable' arrangement to divide the space within the sealing member into cells may be employed. An 20 outer Wall or partition 43 may be provided between the outer edges of the plates 40 and 4|.

The partitions ft2 and the outer wall 43, as. well as the plates ll!) and 4l are coated with theolen polysulde plastic material hereinbe- 25 fore referred to, so that the cells within the sealing member are substantially impervious and may be individually filled with a suitable gas, prefer- With the cellular construction of the device, as

shown in Figs. 5 and 6, in the event of the rupture of one of lthe cells of either of the expansible marginal sealing member or of the rigid center portionthe remaining cells continueA to function-45 and the eiciency of the device as a whole can be substantially maintained.

In the operation of the laterally expansible, gas filled sealing members as hereinbefore described, the outer edges of the sealing member, by reason of their flexibility, and of the internal pressure of the gas withuwhich they are iniiated, tend to follow the irregularities in the 'wall of lthe tank both when stationary and in motion.

The sealing member is of high buoyancy, and consequently there is no diiilculty in floating itv on eventhe lightest liquids.

The seal of my invention is particularly advantageous in connection with the storage of highly volatile liquids under conditions in which a vapor tends to form and overlie the surface of the liquid, This vapor tends to expand and contract with increase or decrease in temperature, to a very substantial extent, producing the phenomenon known as breathing. When a sealing member constructed in accordance with the presy ent invention is used in such a case, on increase in temperature, the expansion of the gas within the seal tends to force itv more rmly against the side walls of the tank, thus providing a better seal and at the same time a greater resistance to upward movement of the sealing member. On the other hand, on reduction of general atmospheric temperature, the contraction of the gas Within the 'sealing member somewhat decreases the torce 75 with which it is held against the side walls of the tank and permits a greater facility of movement of the sealing member downwardly in accordance with the contraction of the yvapors within the tank itself.

I clam:

1. In storage means, a storage tank and a closure member therefor, said closure member being formed of a central portion comprising spaced upper and lower plates, a laterally expansible, flexible membrane secured marginally to said plates and closing the space therebetween, and means for forcing gas into the closure member to expand said membrane laterally and force it into contact with the' walls of the tank. n

2. In storage means, a tank and a closure member therefor, said closure member being formed with a central portion comprising spaced plates and a 4flexible diaphragm secured marginally to said plates and closing the space therebetween, a continuous sheathing of inert plastic material comprising olen-polysulflde plastic belng provided on said membrane and spaced plates, and means for forcing gas into the space between said plates to force said membrane outwardly into contact with the walls of the tank.

3. In storage means, a tank, a container formed of a flexible membrane comprising a continuous fllm of olefln-polysulflde plastic adapted to overlie the contents of the tank, and means for forcing gas into said flexible container to expand it laterally against the walls of the tank.

4. Instorage means, a tank, a flexible-walled container within said tank and adapted to overlie the contents thereof, the walls of said flexible container comprising a continuous sheathing of inert polysulflde plastic, means for inflating said flexible container to cause it to expand laterally and force it against the walls of the tank, and a Weight disposed on the upper surface of said lflexible resilient material that is unaffected by solvents and impermeable to gases closing the l5 space between said tank and said member, said flexible resilient material having its exposed portions composed mainly of a polymethylene-polysulfide reaction product of the general formula CnHznSx wherein a: is more than 2, and being pressed against the inner surfaces of the walls of said tank.

8. Storage means comprising a tank, a closure member for said tank, spaced therefrom, and flexible resilient material that is unaected by solvents and impermeableto gases attached to said closure member and closing the space be- A.tween said tank and said member, said flexible resilient material having its exposed portions composed mainly of a polymethylene-polysulflde reaction product of the general formula. CnHnnSx wherein a: is more than 2.

9. Storage means comprising a tank,`a closure for said tank having flexible resilient material on the surfaces thereof that contact with the inner walls of said tank and also on the surfaces thereof that are exposed to gases that may arise from the contents of said tank, said flexible resient material having its exposed portions composed mainly of a polymethylene-polysulde re- 40 action product of the general formua CnHznSr wherein :c is more than 2. l

10. Storage means comprising a tank, a, closure for said tank having flexible resilient material on the surfaces thereof that contact with the inner 4, walls of said tank, said flexible resilient material having its exposed portions composed mainly of a polymethylene-polysulflde reaction product of the general formula CnHznSx wherein a: is more than 2. JOSEPH C. PATRICK.

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