US2939801A - Methods and means for renovating corrosion-deteriorated tanks - Google Patents

Description

June 7, 1960 J. J. McGlLLls ErAL 2,939,801

METHODS AND MEANS Foa RENOVATING coRRosIoN-DETERIORATED TANKS Filed sept. 11, 195e 2 Sheets-Sheet l gw/ l IN V EN TOR.

June 7, 1960 J. J. McG|LL|s ErAL 2,939,801

METHODS AND MEANS FOR RENOVATING coRRosIoN-DETERIORATBD TANKS Filed Sept. l1. 1956 2 Sheets-Sheet 2 zz jay-ll Patented June `7, 1.960

. videsl amethod'and'nteans whereby a leaky tank not only may be permanenti s'ealedat the leak or leaks butmay z 939 801 *be conditioned foifiirther long service' without danger y that new leaks willsiiyelop, it is of considerable im- METHODS AND MEANS FOR RENOVATING 5 pertence that the mentioned sealing and conditioning may CORROSION'DETERIORATED TNKS, V be accomplished while thetank continues filled or partial- John J. MoGinis, 1339 Ash si., and iingh n. Mooiiiis, lY flllelW-tll eil faidfiwitlleusbstantiel less .0f Oil 'duf- 270 Manomet St., both of Brockton,.Mass. l lngI-Itlleahng and-fentdltlglulgg ptfoless.

ence,"it is among" eo ts o t e invention opro- Flled SePt n 1956 ser' Nnnul l l0 vide amethod of permanently sealing leak-holes in bottom wall portions of lled or filled oil tanksandv the like, whilesimlilt'aneously"insring against annsubsequentfdevelopment-:of corrosion-induced leak-holeswithj Ei in a predeterminedband of bottom Wallextending from This invention relates to improvements in methods `1p end to Wend of anyp arcu1ar.-tank f n and means for sealing leaks in oil storagedanksnrthe. Ammer object-f the nvm -o is to provide 'imethod llkegand for Protecnng tank Walls agalnsndslanol'afwnfn of .permanently sealing leak-holes in oil storage tanks, service. More particularly, the invention. provides a and th'elke, wljlgimultaep'sly permamly Pfoten.

method and means for Permanently saallng anynnla'znn ing a predetermined "band-of bottom wall of the tank holes that may have developed in lower wall portions of V20 an oil storage tank, or the like, or for permanentlypro tecting said lower wall portions againstlicorrosiverde terioration, the said sealing and protecting being c ective ly accomplished without need for emptyingthe tank of s. oil, or other liquid. ,.-igf'j The present application is a continuationimpart otour applications Serial No. 348,211, lled April .13, 19 53, `a1id Serial No. 423,489, tiled April 15, 1954`. 'ent i.t1ed Method and Means for Renovating Corrosion-Deteriorated 1`ank`s; both now abandoned. ',j .1- Oil storage tanks of the conventi nal sheet metal varieties are subject to deterioration .-in service dueto corrosion resulting from moisture which` unavoidablyfge ts into the tanks in relatively small amounts .anderideses on lower wall portions thereof. Moisture "n Arelativi-.ly small amounts Ordinarily is Present in* nilflllllnlfenlintn vwall of the'tank permanently sealing said covered band the Storage tanks and tends t0 settle anflf'isnndenSe-ln ofwall against any deteriorating effects of moisture which teflefly 0f the tank WallS- Detel'lolfatlnn'f-'Qfjtlle"tank' maybe present within the tank, the cement in the said Walls, dne t0 OOI'I'OSiOn iS a l'elatlvelygslew PlneeS'S 'and K 4covering mixture-providing a permanently stable proteca tank may Serve its PnfPOSeS fOl' elglltf-'ten's twelve, '0l' y tive covering having the property of absorbing and harmmore years, before the ravages ef eerreswn ultimately tessiy. consuming moisture from the interior of the tank.

ing thereon permanently sealing the said band of bottom from the tank and also sealrenovated. Aoil Ystorage. tank,

orf partially'lled tank is distributed as an adhered prond to end ofA adhered protective cover- I i .l titheY likefwhereinfa' rnix-".,v vtureof fibrous` material andcement deposited intoa-iilled .",tectivecovering. overal predetermined band ofbottom produce one er mere leak holes in the' tank walle-` stiu another object of the invention is to provide a HeretOfPl'e, an Oil tank Wh0Se Walls have detel'nfated tankrenovatng methodwhereby a corrosion-deteriorated t0 a eondltlOn 1n .Wlllch Oll leaks f1'0lnftl1e tank-tllfnngh oil storage tank, or the like, may be restored for a fura llle 91' holes eaten by 01T0Sl0n thlonghjtnn tank Walls 4 'ther -long life of service Without need for emptying the Oldlnalllv would be enndenlned aS nnt 4f0.1' fnl'tlhel eX- tank but with the contents of the tank serving to oat a tended Sel'vCe- SOlnetlnleS Snell a leak llaa been'tenlpo' deposited lmixture into covering relation to a predererily Sealed er patehed te step the leakage 'of eil; until terminen band of bottoni wall of the tank, and with the SnCh time aS the Oldl tank might be l'elllaged by' a-new materials of said mixture providing a stable adhered pro- Gne bnf, S0 far aS We'al'e aware n0 -Plflnlfseallnffof 5 tective covering over said-band of bottom wall permanent- Patelllng PI'OCedUl'e has cnntenllflatefl lestnl'atlnniqf a ly, sealing the,4 covered band' against any deteriorating leaky tank t0 a COlldltlOn k111 Wlllell lt Cnnldf'felldel'fexeffects of moisture which may be present within the tank, tended further Service WlthOnt danger 0f.?, 'ree nll.ene 0f the -said tank contents and said mixture coacting to eect the Old leak$ 0l` development 0f new leak-.Sq- 5 a .sealed plugging of any leak-hole or leak-holes that Leaks in oil storage tanks, due tocorro'sion, d'evelope-` may have been present in the said band of bottom wall of only at lower wall portions of the tanks because moisture the tank.- within the tank settles and condenses predominantly' on .The mentioned objects and results may be attained the lower or bottom portions of the tank :Iv'ltallS-v F0?I i by depositing suitable materials, including a relatively' example, corrosion-induced leaks in oil tanks fof the 'cross largeamount ofvPortland cement or the like, into the tank sectionally curved-bottom types develop onlylin'arelativewhich is to be renovated or protected against corrosive ly narrow band extending longitudinally along the bottom deterioration, the said materials being adapted to proof the tank.. Long experience indicatesthat substantialvide an adhered and stable protective covering over a ly all such leaks develop within a band' from four to predetermined band of the tank bottom wall, from end ve inches wide because such moisture as may be present 6 to end of the tank, thereby to permanently seal said band within any such tank tends to settle and condense within against the ravages of corrosion, and to expose abody this relatively narrow band of bottom wall. Hence, when of cementitiousmaterial to direct contact with the oil, corrosion causes such a tank to leak, it may be fairly or other liquid, for absorbing and consuming moisture assumed that the corrosive deterioration of the tank walls froml the oil.

will be substantially confined to the mentioned band along 70 In the .case of a tank having corrosion-developed leakt Athe tank bottom and that other portions of the tank walls holes, the leak-holes may, if desired, be enlarged and continue in serviceable condition. The invention proplugged from the exterior of the tank prior to deposition within the tank of the materials for sealed protective covering of the mentioned band of tank bottom wall. Preferably, however, any leak-holes in a tank bottom wall are plugged from within the tank by the material deposited in the tank, some of said material being carried into plugging relation to any leak-hole by the oil or other liquid initially escaping through the leak-hole. The subsequent build-up of the sealing protective covering over said band also permanently seals the plugged leak-hole which, if desired, may be subsequently plugged exteriorly of the tank to provide a finished exterior appearance.

In the accompanying drawings:

Fig. l is a vertical cross-sectional view through a conventional variety of home fuel oil storage tank having an adhered protective covering body of material covering and sealing a substantial width of the tank bottom wall against deteriorating effects of corrosion;

Fig. 2 is a cross-sectional view on line 2-2 of Fig. l;

Fig. 3 is -a fragmentary cross-sectional view of the lower wall portion of the tank of Figs. 1 and 2, on a larger scale, and prior to deposition in the tank of the sealing and covering material of Figs. l and 2;

Fig. 4 is a view generally similar to Fig. 3 but showing the deposited material settling through the oil, or other liquid, and being carried by the escaping liquid into plugging relation to a leak-hole in the bottom wall of the tank;

Fig. 5 is a Iview generally similar to Figs. 3 `and 4 but showing the deposited material covering a substantial width of the bottom wall of the tank and also covering the plugged leak-hole therein;

Fig. 6 is a view similar to Fig. 5 but showing the interiorly sealed leak-hole exteriorly plugged by a screw plug; and

Figs. 7-11 are views generally similar to Fig. 3 but showing successive steps in a modified form of the invention in which a leak-hole may be exteriorly plugged prior to deposition of the sealing and protective material within the tank.

Generally, the following disclosure contemplates applying to an area of the inner surface of a metallic, e.g. steel, oil-tank, without removing the oil therefrom, an aqueous cementitious material whose characteristic ingredient is selected, from the class consisting of inorganic silicon compdnd-iiorgamc calcium compounds. It has been foun a suc a materia w ic as greater density than the oil through which it is applied, is capable of adhering to and solidifying upon the inner surface of the tank, notwithstanding the presence of the oil, in order to provide a coating that seals leaks and prevents corrosion.

Referring to the drawings, a conventional variety of oil storage tank 10 is represented in Figs. 1 and 2 partially filled with oil 12. According to the invention a predetermined band or bottom wall, extending from end to end of the tank, is covered by a body of material indicated generally at 14, which is adhered to the bottom wall as a permanent covering which effectively seals the covered area of bottom wall against deteriorating eEects of corrosion.

The bottom wall of the tank 10 may have developed a leak-hole or a number of leak-holes as a result of corrosion, and Fig. 3 illustrates a small leak-hole 16 and shows also a region at 18 where the metal has been substantially reduced in thickness by corrosion.

Such a leaky tank, or a deteriorated tank which not yet has reached the leaky stage, or even a new tank, may,

'according to the invention, be renovated for further long water to provide a owable mixti which, when poured The siliceous cementitious material may be Portland cemgpt, or the like, and the manantial may be asbstos fibre, preferably, for the most part, relatively coarse and lo'n-g fibres. However, we have found that the fibres lodge in and plug leak-holes more rapidly and eectively if they are coated or partially coated with adhering cement which also has a grouping effect on the fibres. The cement adhering to the fibres aids and hastens settling of the fibres through oil in the tank, and the grouped fibres can more readily lodge in and plug relatively large leak-holes, as compared with fibres not coated with the cement.

In what we presently consider to be a preferred procedure, a lime-silica or lime-clay cement, in an extremely fine dry powder state, is thoroughly pre-mixed with the asbestos fibre to provide a preliminary dry mixture in which the cement powder constitutes from 40% to 60% of the mixture. This preliminary dry mixture next may be thoroughly mixed with siliceous material of the Portland cement variety, in approximately the proportions of four arts Portland cement to one part of the preliminary mixture, wil wam-dm a readilypurble wet mixture approximating the consistency of heavy cream.

The fine powdered cement in the preliminary dry mixture xbecomes intimately associated and intermingled with individual fibres and with matted or interltwined groups of the fibres. During the final mixing with Portland cement and water, considerable amounts of the water-activated lime-silica or lime-clay cement adheres to the fibres and groups of fibres. As the ultimate mixture is poured into an oil-containing tank 10, it readily settles through the oil 12. Pouring of the mixture is continued until an accumulation builds up on and spreads over the bottom wall sucient to completely cover the predetermined band of bottom wall which is to be sealed against corrosive deterioration. I'he mixture is of a nature to set to substantial hardness while immersed in oil, and the lime-silica or lime-clay cement and the Portland cement cooperate in effecting a relatively strong adhesive bond between the cementitious mass 14 and the tank walls, sealing out all moisture. The water coritent of the poured mixture becomes absorbed and consumed yby the Portland cement which subsequently absorbs such relatively small amounts of moisture as may get into the tank. The fibre in the set mass minimizes cracking or pulling away from the tank walls due to expansion and contraction of the mass and tank. This is especially true when oil 14 in the tank 10 constantly covers the cementitious mass 14, a condition which ordinarily prevails because the cementitious mass may be entirely below the outlet from the tank.

It is a characteristic of the cementitious mass 14 that, when it has set, its top surface which is exposed to the oil 12 is at and smooth, presumably due in some measure to the pressure of oil thereon during the setting process. The smoothness of this top surface, which is subiected to the eEects of any turbulence of the oil within the tank, minimizes the likelihood of fragments of the cementitious mass becoming detached arid floated away in the oil. However, it is recommended that a suitable filter -be provided in the flow passage between the tank and the oil burner -to ensure against the possibility of particles of the poured mix or of the ultimate protective mass being carried through the oil feed line to the burner,

,` tory & Insulation Corp., of

If there is a leak-hole in the bottom wall of a tank which is being renovated, such as the hole 16 shown in Fig. 3, oil will be escaping ltherethrough, and some of the poured mixture initially will be carried with the oil through the leak-hole until fibres, adhesively grouped or otherwise, lodge and accumulate in the hole and relatively quickly plug the hole against all but a mere seepage of oil. The subsequent accumulation of the poured mixture covers the plugged hole 16, preventing any further leakage or seepage of oil through hole 16 after the mass 14 has set in sealed attachment to the tank walls. Fig. 4 shows fibres of the poured mixture accumulated in leak-hole 16, and Fig. 5 shows the built up cementitious mass 14 covering bottom wall portions of the tank and covering the plugged leak-hole 16.

The fibre-plugged leak-hole 16, when desired, may be suitably enlarged exteriorly of the tank for reception of a screw plug, or the like, to provide a finished exterior appearance. 'Fig 6 shows such an exteriorly applied screw plug at 20. Plug 20 ordinarily will be put in place while the poured interior mixture continues in a relatively fluid or plastic condition and the plug becomes locked and sealed by the interior mixture when the latter sets. Or, the plug 20 may be screwed into place after the interior mixture has set, the fibre re-inforced interior mass, following complete setting thereof, being of a nature to receive the screw plug 20 without cracking.

herein. A- dry preparation available under "thiiame 11E-@taking puwutblguialo., Ine.. of 527 Fifth venue, able under the name New York, N.Y., and a dry preparation avail- Stic-tite and put out by Refrac- 120 Wall Street, New York,

l N.Y., may be employed to provide our preliminary mixnalysis indicates that Insulag .Ny hier ure of asbestos fibre and lime-silica or lime-clay cement.

consists of approxifour arts4 lime-silica Stic-tite consists of p- I ately one part asbestos fibre to lime-clay cement, and that H roximatel one art lime-silica or l1 e-cla cement to UL P Y P Milam-Mm..

four arts as'sfbm cement in each prepahratron consists of approximately one part lime to four parts silica or clay. These available dry preparations may be mixed together in approximately the proportions of one part Stic-tite to three parts Insulag to provide a preliminary dry mixture contanin alittle less than two parts cement to one part asbestos Ebre. In the nsu ag prepzation, thefbres, to a considerable extent, tend to be matted or intertwined, or otherwise joined, into relatively small groups of fibres with a relatively large amount of finely powdered cement intimately associated therewith, which makes this preparation generally coarser than the Stic-tite preparation wherein the fibres do not become grouped to any notable extent, and wherein there is a relatively smaller amount of the cement powder. These differences in the ltwo preparations areA advantageous in the ultimate pourable mixture in that the grouped fibres more readily become lodged in fairly large leak-holes and the relatively individually free fibres more effectively can enter and lodge with others to plug smaller leak-holes and cracks.

Figs. 7-11 illustrate a modified tank-renovating procedure wherein any leak-hole in the bottom of a tank may be initially plugged from the exterior of the tank prior to deposition in the tank of the materials for protectively covering the predetermined band of tank bottom wall. Assuming that a tank has a small leak-hole as indicated at 16 in Fig. 3, the hole may be drilled to a larger size, as at 30 in Fig. 7, for reception of a relatively soft rubber plug 32 which is shown in Fig. 7 ready to be thrust into the enlarged hole 30. Oil gushes out through the enlarged hole until plug 32 is in place, as in Fig. 8, stopping all but a slight seepage past the plug. But the oil quickly acts on the soft rubber plug with deteriorating effect and causes substantial swelling of the plug which relatively quickly takes the general form as represented in Fig. 9. It is essential that deterioration of the rubber plug be arrested before the plug becomes decomposed to a degree which would destroy its effectiveness as a plug, and this may be accomplished by deposition in the tank of material which spreads over the bottom of the tank, as described in connection with Figs. 1-6, and over the rubber plug as in Fig. 10. The deposited material may be the same mix which forms the protective body 14 in the Figs. 1-6 embodiment, in which case the body 14 effectively seals the plugged hole against entrance of any additional oil to the rubber, as well as sealing the covered band of tank bottom wall against corrosive deterioration, as described in connection with Figs. 1-6. Or water glass 34 may be first deposited in the tank to provide a sealing coating over the plug and over the tank bottom area which is to be protected, followed by deposition of Portland cement to provide a stabilizing protective body 14' over the water glass 34, in Fig. 11.

It should be understood that the invention, in its broader aspects, provides a tank-renovating procedure and method wherein any of a variety of inorganic siliceous, cementitious materials, having specific gravity greater than that of an organic liquid stored in a metal tank, may be poured into the filled or partially filled tank to renovate the tank while it continues to be filled or partially filled with oil, or other liquid. The poured material preferably will be mineral aqueous cementitious material, suitable examples of which are Portland cement, Atlas cement and Keenes cement with water added suflicient to give the cement the consistency of relatively heavy cream.

The pourable material in some cases, such as when a tank has no relatively large leak-holes, may consist entirely of one of the mentioned mineral aqueous cementitious materials, rendered pourable and settable by addition of a suitable amount of water. When fibres are omitted from the pourable material, some cracking of the protective body may occur in the setting process, but minor cracks, apparently, do not effect the effectiveness of the protective mass, presumably because the cement tends to absorb and consume moisture which otherwise might condense on the tank walls. Neither do such minor cracks materially increase the likelihood of fragments becoming loosened or broken away from the mass as a result of turbulence of oil in the tank, especially when the oil inlet pipe is equipped with a spray nozzle as indicated at 1l in Figs. 1 and 2, such a nozzle 11 being recommended in all cases to avoid concentration of a stream of incoming oil at any one location. Nozzle 11 relatively gently sprays the incoming oil with no substantial created turbulence wthin the tank.

Addition of fibre to the cement usually will be found desirable, inasmuch as the fibres initially lodge in leakholes and cracks to effect plugging thereof before the poured material accumulates on the tank wall portions and ultimately sets in adhered covering relation to the mentioned predetermined band of bottom wall which becomes permanently sealed against corrosive deterioration. Also, the fibres strengthen the cementitious mass, minimizing any tendency of the material to crack or pull away from the tank walls. If the fibres are mixed directly with the sliceous cement and water when preparing the pourable mixture, the fibres preferably should be asbestos fibres, or comparable mineral fibres of a nature to settle through oil. On the other hand, if the fibres are pre-mixed with lime-silica or lime-clay cement to provide a preliminary dry mixture as earlier described herein, other varieties of fibres may be employed, such as vegetable fibres because the fibres of this preliminary mixture become coated or partially coated with the lime-silica or lime-clay cement when the latter is activated by the water in the ultimate mixture, and the adhering cement causes the fibres to settle through the oil and they can serve the unctions described in connection with asbestos fibres.

It is intended that the patent shall cover, by suitable expression in the appended claims, whatever features of patentable novelty exist in the invention disclosed.

We claim as our invention:

1. The method of coating an inner bottom surface area of the walls of a generally cylindrical horizontally disposed oil-containing tank, comprising the steps of predetermining a relatively narrow band of bottom wall of the tank within which band substantially all corrosive deterioration of the tank occurs, depositing through a top opening in the tank an aqueous cementitious material in quantity to cover said predetermined band by settling through the oil in the tank, said deposited material containing a mixture of lime-clay gguulnandag and to which has lle en added inaqueous vmixture a compound from the class consisting of compounds fpfsiliand calcium; the said deposited material being of a nature to smc through the oil in the tank into protective covering relation to said predetermined band of tank bottom wall, and letting all of the band-covering deposited material set to substantial rigidity while immersed in said oil.

2. The method of renovating an oil tank which has developed leak holes as a result of corrosive deterioration comprising predetermining a relatively narrow horizontally extending critical band of tank wall wherein substantially all said corrosive deterioration of the tank will occur, preparing an aqueous mixture of a fibrous material and a cementitious material having greater density than the oil in the tank, settling said mixture through the oil whereby said fibrous material oats to and lodges in and substantially to plug the leak-holes, continuing the settling of the material until a substantial accumulation thereof covers only slightly more than said predetermined critical band and said leak-holes, and letting all of the band covering accumulation set in the presence of said oil to provide a stable, substantially rigid covering over said critical band and said leak-holes.

3. The method of renovating a generally cylindrical horizontally disposed oil-containing storage tank susceptible of corrosive deterioration producing leak-holes in a lower wall portion thereof, comprising predetermining that relatively narrow longitudinally extending band of tank wall wherein substantially all said corrosive deterioration will occur, providing a pourable aqueous mixture of a mineral cement and a lime-silica compound interspersed with fibrous material and having specific gravity greater than that of the oil in the tank, pouring said mixture into the tank thereby causing the mixture to settle through the oil and accumulate on said lower wall portions of the tank, a relatively small amount of said poured mixture being initially carried through said leak-holes by escaping oil until fibres in the mixture lodge in and effectively plug the leak-holes, continuing the pouring until said accumulation builds up on and spreads over only slightly more than the total area of said predetermined band of tank wall including said fibreplugged leak-holes, said poured mixture being of a nature to relatively strongly adhere to the covered wall portions of the tank and to set into a relatively rigid brereinforced cementitious body protectively sealing said covered band of wall against corrosive deterioration.

4. The method of renovating an oil-containing storage tank as defined in claim 3 wherein the said fibres are pre-mixed with finely powdered lime-silica cement in a dry state to provide a dry preliminary mixture in which the powdered cement constitutes from 40% to 60% of the dry mixture, the said pourable aqueous mixture consisting of approximately one part of the said preliminary dry mixture and four parts of the said mineral cement.

5. The method of renovating a generally cylindrical horizontally disposed oil-containing storage tank having a leak-hole in a lower wall portion thereof, comprising predetermining a relatively narrow horizontally extending band of tank wall wherein substantially all corrosive deterioration of the tank will occur, pre-mixing finely powdered lime-clay cement in a dry state with fibres to provide a dry preliminary mixture in which the powdered cement constitutes from 40% to 60% of the dry mixture, whereby the cement powder becomes intimately associated and intermingled with the fibres, followed by thoroughly mixing approximately one part of the said preliminary mixture with approximately four parts of settable siliceous cement, and water suicient to provide a pourable mixture having substantially the consistency of heavy cream, and then pouring the latter said mixture into the tank through a top wall opening whereby the poured mixture settles through the oil and accumulates on lower wall portions of the tank, some of the settled mixture being carried by leaking oil into and through the said leak-hole until fibres in the mixture lodge in and substantially plug the leak-hole, the said intimacy of association of the cement and fibres in said preliminary mixture resulting in substantial amounts of the pre-mix cement becoming intimately adhered to the libres when the cement is activated by said water, whereby settling of the fibres s aided by the adhering cement which also tends to unite fibres in relatively small groups which facilitate the said lodging of libres in the leak-hole, the pouring of the mixture into the tank being continued until the accumulation thereof has built up on and spread over only slightly more than the total area of said predetermined band including the portion thereof in which said leak-hole is located, and all of the said accumulation being allowed to set within the oil to substantial rigidity in adhering sealed relation to the said band of tank wall bottom wall portions of the tank.

References Cited in the file of this patent UNITED STATES PATENTS 1,281,690 Stern Oct. 15, 1918 2,110,053 Phillips Mar. 1, 1938 2,235,937 Linberg Mar. 25, 1941 2,320,633 Mitchell et al June 1, 1943 2,328,292 Painter Aug. 31, 1943 2,502,409 Bour Apr. 4, 1950 2,526,674 Larsen Oct. 24, 1950 2,629,667 Kaveler Feb. 24, 1953 2,795,507 Kaveler June 11, 1957 2,874,778 Kaveler Feb. 24, 1959 OTHER REFERENCES Volclay Bentonite, Data #230-3; Data 231-D; page 2; Data #202, pages l and 2.

Claims (1)

1. THE METHOD OF COATING AN INNER BOTTOM SURFACE AREA OF THE WALLS OF A GENERALLY CYLINDRICAL HORIZONTALLY DISPOSED OIL-CONTAINING TANK, COMPRISING THE STEPS OF PREDETERMINING A RELATIVELY NARROW BAND OF BOTTOM WALL OF THE TANK WITHIN WHICH BAND SUBSTANTIALLY ALL CORROSIVE DETERIORATION OF THE TANK OCCURS, DEPOSITING THROUGH A TOP OPENING IN THE TANK AN AQUEOUS CEMENTITIOUS MATERIAL IN QUANTITY TO COVER SAID PREDETERMINED BAND BY SETTLING THROUGH THE OIL IN THE TANK, SAID DEPOSITED MATERIAL CONTAINING A MIXTURE OF LIME-CLAY CEMENT AND FIBRES AND TO WHICH HAS BEEN ADDED IN AQUEOUS MIXTURE A COMPOUND FROM THE CLASS CONSISTING OF COMPOUNDS OF SILICON AND CALCIUM, THE SAID DEPOSITED MATERIAL BEING OF A NATURE TO SETTLE THROUGH THE OIL IN THE TANK INTO PROTECTIVE COVERING RELATION TO SAID PREDETERMINED BAND OF TANK BOTTOM WALL, AND LETTING ALL OF THE BAND-COVERING DEPOSITED MATERIAL SET TO SUBSTANTIAL RIGIDITY WHILE IMMERSED IN SAID OIL.

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