US2186185A - Method of tank construction - Google Patents

Description

Jan. 9, 1940 HM q WALKER' 2,186,185

ummm o@ camminano @riginal Filled Eem 24,.

F1 Gpl;

Suunto:

Patented -Jan., 9;, 1940 srarss escasas. c 'rnon or 'r coNs'raUc'rroN Henry G. Walker, Warren,

Pa., assigner to nemend lren Works, "Warren, Pa., a corporation ci 'Pennsylvania oai implication December 24, 1937, serial No.

Divided and this application July 14,

i938, Serial No. 219,109

5 Claims. v(Ui. .2S-1482) This vinvention relates to tanks or reservoirs for containing or storing materials such as liquids, and has particular reference to storage tanks of the type adapted to accommodate rel- .s atively large bodies of oil, petroleum or other viscous liquids, especially those liquids whose specic gravity is less than that of water.,

More speciiically the invention relates to the bottom construction of such tanks and to a manm ner of constructing and the arrangement of a bottom in the tanks to afford a strong, durable and substantially water-tight construction.

The prime object of the invention is to provide amethod of rendering nt for utilization again, liquid holding tanks the bottoms and/or lowermost wall vportions of which have become leaky and are no longer water-tight as a rult of rusting, erosion or corrosion.

Another object is to provide a method of inw stalling, in tanks Athat have become leaky at the bottom or adjacent thereto, a false or replacement bottom in a manner that will afford a substantially water-tight construction, and at the same time to determine that the structure is subw stantially water-tight.

Petroleum land. its products are usually stored in steel tanks above-ground. In most locations the steel tanks are set directly on the ground. These tanks are generally constructed of plates of structural steel, the plates running in thickness irom of an inch upwards. The plates forming the bottom are joined together in a water-tight manner by riveting, bolting or welding and the edges of adjoining plates are generas ally lapped. The walls of the tank are generally constructed of rings made up of a number of plate sections, the lowermost ring being joined to the bottom by means of an annular angle iron,

all joints being made Water-tight in any suitable l w manner.

In tanks of this sort corrosion dilculties are encountered most frequently at the bottom and at the joint between the bottom andthe walls of the tank` and cause considerable annoyance y necessitating expensive repairs and in many cases necessitating razing of the tank and erection of a' completely new one. The reasons for these `corrosion troubles being confined primarily to the bottom portion of t, First, there is the fact that any water in the tank or body of. oil contained therein will gravitate naturally to the bottom and will there attack the bottom plates and cause oxidation and rusting. Furthermore, the bottom is affected on its underside'by the humus acids inthe soil the tank are several.

upon which it rests. To the causes are added the contributing chemical eiectsof the various acids in the oil itself., y

Having in mind the above'enumerated corrosion 'difdcultiea it is a primary purpose of the E present invention to provide a method of enacting repair or replacement of a corroded tank bottom in an eminently satisfactory and economical manner and to obviate the necessity for completely rebuilding the bottom or replacing the entire tank structure. v

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the' following description. In the accompanying drawing, for the purmi; pose' of example there has been illustrated the best embodiment of the invention now known to me, but such embodiment is to be regarded as typical only of many possible embodiments-and the invention is not to be limited thereto. m

In the drawing:

Figure l is a top plan viewl of an oil'storage tank showing one manner of arranging the individual steel plates comprising the replacement bottom according to a form of the invention.

Figure 2 is a top plan view similar to Figure l but showing a storage tank rectangular in cross section.

Figure Sis an enlarged sectional perspective view through part of the bottom and side wall a@ of an oil storage tank showing the replacement bottom of the present invention ln position and illustrating the method o! constructing the same..

Figure 4 is a vertical sectional view similar to' 4Figure 3 and showing a modified detail of the 35 l construction.

Referring particularly to Fig. 3, the numeral 5 designates the upstanding side wall of an oil storage tank circular incross-section, the saidv wall being constructed of a number of -steel plates 40 joined together by riveting, welding or other appropriate means. The wall 5 adjacent its lower edge is secured to the upstanding flange of an annular angle iron 6 by'means of the rivets 1, and tothe horizontal flange of the angle iron 6 5 is attached the original tank bottom 8 by means of the rivets 9. `For convenience in illustration, the tank bottom 8 has been shown as a onepiece structure.- However, 'as mentioned above, the tank bottom is generally constructed of lap 50 or butt jointed plate sections. Furthermore," the wall 6 and bottom 8 have been shown as riveted to the angle iron 8 but it is understood that they may be secured to the angle iron in any other suitable manner such' as by bolting or welding. f ,5

The joints between the angle iron and the bottom and sides also are generally made water and oiltight by calking or otherwise, when a riveted or bolted construction is used.

5 As explained above, the bottom 8 in most instances rests directly upon the ground as will clearly be seen in Fig. 4, and is subjected to various corrosive attacks both from the constituents-oi` the soil on the underside and from the 1g Water and possibly other contents of the tank or.

the upper side.

The useful spanof life of storage tanks constructed aS above is definitely limited and is gen? erally determined by the condition ofthe tank 15 bottom. This may sometimes be repaired but such repairs are diflicult and expensive and inA any event the bottom will eventually beeome'so corroded as to preclude effective repair and thus necessitate complete rebuilding of the tank 20 even though the upper Walls may be perfectly satisfactory lfor continued service. The present invention completely eliminates these diiculties by providing a method whereby a complete replacement or false bottom may be built into the gij'tank with a minimum of effort and expense and will provide in eil'ect a completely rebuilt bottom Y that is water-tight, durable and highly emcient. Referring again to Fig. 3, it is assumed that the bottom 3 of the tank has become so corroded 3@ as to render it no longer efcient. The tank is completely drained of its contents and upon the upper side of the bottom 5 is spread a uniform and homogeneous layer or foundation It of sand, fine gravel, cinders, or other loose aggregate. .35 The thickness of the layer IG may be any that is desirable, but in the present embodiment is generally built up so that its top surface is approximately level with the highest point on the upper heads II of the rivets d so that the heads 4o ii will serve as steps or foundations upon which the 'outer periphery of the false bottom may solidly rest.

The foundation I il having been laid firmly in place, there is now constructed upon upper 5 surface thereof, a replacement or false bottom i2 which is preferably composed of individual plate sections i3 joined to one another in a watertight manner by welds I These plate sections v are preferably lap-Welded to one another as 50 shown in Fig. 4, but may, of course, be buttwelded as seen'in Fig. 3. The false bottom I2 may, of course, consist of a single unitary steel member. However, a steel shape of that character would be extremely diicult and expensive 55 to obtain so that the bottom l2 is generally constructed, in situ, of the individual plate sections,

as just described. Fig. 1 shows the manner in which the plate sections adjacent the outer perlphery of the member l2 may be cut or sheared @a to conform to the contour of the inner wall o the tank. v

The thus fabricated false bottom l2 is substantially circular in shape and 'of a diameter just slightly less than the inside diameter of the tank 55 adjacent its bottom so that the outer peripheral edge of the member I2 lies closely. adjacent to and approximately parallels the inner wall of the tank, with the underside of the false bottom I2 adjacent its periphery resting firmly Aupon the 70 heads II of the rivets 9 as hereinbefore explained. The outer edge of the false bottom I2 at its upper side is now intermittently welded to the inside faceof the vertical ange of the annular a'ngle iron 6 or the inside of the wall 5 75 of the tank as the case may be by means of the -nection.

interrupted llets I5, leaving an unwelded area.

I 6 of substantial extent between each llet, fora the purpose presently to be described.

The false bottom I2 having been thus fabricated and resting upon its sand cushion I on the heads II of the rivets, there is now provided means for sealing the new bottom I2 to the inner side of the wall so as to provide a water-tight and substantially oil-tight construction and' provision is made, in connection with this sealing means. for testing the construction and ascertaining that it is water-tight, or of locating the nature and extent of anypoints of leakage. To

this end a sealing ring I'I, in the preferred construction taking the form of an inverted angle iron, is placed in position entirely around the inside of the tank adjacent the point of conjunction ofthe side wall'5 and the bottom I2,

placed at an angle with one edge resting against the side Wall and the other against the bottom.

,The sealing ring I'I is continuous, of course, and

extends completely aroun'd the inside of the tank. The horizontal leg I6 of the sealing ring I'I, which parallels the inner surface of the wall 5, is now welded to the inner surface of the wall by means of the continuous and uninterrupted fillet I9 which extends completely around the inside of the tank and forms an eiectively sealed joint between the leg I 8 and the inner surface of the wall 5. To seal the joint between the edge of the vertical leg and the bottom I2, the said leg is welded tothe bottom by means of the continuous and uninterruptedllet 2l which also extends completely around the joint between the bottom and the sealing ring and forms an edective water-tight and substantially oil-tight seal. It will 'now be apparent that, assuming all of the welds hereinbeiore described to have been executed in a satisfactory manner, the tank will now be provided with a new bottom which will be in all respects water-tight and substantially oil-tight. A visual inspection of the. various welded areas will generally sulce to assure that all joints are Water-tight, particularly if relatively large amounts of weld metal are used throughout the welded areas. However, in order to provide an accurate check on theforiglnal inspection, and, particularlyif a minimum amount of weld metal is used at the various joints, a method and means are provided for testing the newly fabricated structure in order to determine beyond doubt that it is actually watertight.

For this purpose one or more relatively small holes or openings 22 are drilled through the horizontal leg I8 of the sealing ring il. The opening 22 is then screw-threaded' internally and 4into the same is then screwed the pipe or tube 23 having a corresponding externally screwthreaded end. It is understood, of course, that the opening 22 need not necessarily be screwthreaded and may receive theend of a pipe or any other type of tube without a screw-threaded connection, a Vscrew-threaded connection, however, providing a solid joint more satisfactory for the ensuing test than most other types of con- Having now placed the pipe 23 in position so that it communicates with. the space between l to 'lo rate the sand cushion I0 and completely fill the space 24. Thereafter continued pressure on this body oi liquid exerted through the pipe 23 will force the liquid through any part of the new construction that is not water-tight and will thus 1g appear on the inside of the tank and apprise the observer of any points or localities of leakage. lAny points where such leakage is observed may then be ef'lectivelyl sealed by welding and the` structure effectively made completely water- Upon completion of the foregoing test, and having observed that there are no leaks, or having remedied whatever leaks may have been observed, the pipe 23 is now withdrawn from the 25 opening 22. The opening or openings 22 are then tightly sealed preferably by means of. screwthreaded bolt 25 if the opening 22 is internally screw threaded. If not, other suitable plugs or sealing means may be used such as a metal plug which may be welded into the opening.

The new bottom construction and joint having been thus thoroughly tested and examined and the test openings 22 having been effectively plugged and sealed, there is now provided an oil storage tank having a completely new bottom that is water-tight and substantially oil-tight in every particular 'and that is satisfactory and eminently fit forcontinuation of its oil storage function.

The above described method of testing the new bottom construction with water is generally the most convenient where an adequate water supply is available. In addition, other testing methods may be mentioned briey and these will provide an even'more accurate check upon the oil-tight characteristics yof the welded seams. Where sufcient oil, petroleum or any of its products is available, a quantity of the same may be forced through thepipe 23 and into the sand bed IIJ and the space 24 and a static pressure built up against it sufficient to force the oil through anyopenings, even very minutel ones.

This method will, of course, provide a very accurate test since it will reveal any points through further advantage in that it provides the underside of the new or false bottom I2 with a protective coating -of oil or petroleum' which, of course, will hinder to some extent, the corrosive attacks vof water and moisture upon the underside of the false bottom.

Another useful test method, where neither oil nor water are readily available, is to smear or coat all seams or welded areas with a soap solution. Air is then forced or blown through the pipe 23 and beneath the bottom I2 and into the space 24. With 'a relatively small amount of pressure behind the air, the same will, of course,

be forced through any openings or poroiu points in the welds and 'will reveal itself in the form of bubbles caused by contact of the air with the coating of soap solution. Wherever the bubbles appear, additional ,welding can be effected and thus assure air-.tight seams which will, of course.

be watertight and substantially oil-tight.

which oil' couldleak. .This method also has theV While steel oil storage tanks are most generally constructed with a circular cross-sectional configuration, square or rectangular tanks are sometimes encountered and a plan view of. this type oftank is shown in Fig. 2. In that'construction it is a relatively simple matter to lay out and fabricate the false bottom I2 as shown since the plates I3 do not have to be sheared to conform with the inner contour of a curved wall. In the construction of Fig. 2, the plates are merely laid upon the sand cushion I0 as previously described and then intermittently welded toA the side walls of the tank. In this instance the sealing member I1 will preferably be constructed offour straight sections of 'angle iron, or other preferred metallic shape, one 'of which sections will, of course, be laid along each side wall oi'A the tank and continuously welded to the correspending side wall and to the false bottom I2. These strips will, of A one another at their joints 2B in each corner of the tank and -the construction may then be tested for leakage in any of the manners hereinbefore described in connection with the round tank:

It will be appreciated, of course, that, in either shape of tank, the false bottom I2 need not necessarily be welded or joined to the side wall 5 as at I5. In other words, if preferred, the false bottom may be fabricated upon the cushion II) and the sealing ring Il may be applied thereafter without any welding or otherwise joining of the peripheral edge of the false bottom to the slde wall, the intermittent weld flllets I5 serving mere-l ly to provide a more rigid and durablel structure. The cushion Ill of loose aggregate material might also in some instances be eliminated without decourse, also be welded toparting from the scope of the invention.- In that event it would probably be necessary to place blocks of wood or other material at scattered points over the original bottom 8 to serve as supporting elements for the false bottom I2 and to prevent any tendency of the same to buckle, the continuous cushion of loose filling material, however, being preferred as it supports the false bottom throughout its entire area and eliminates any stress caused by the weight of the contents of the tank.

In either event the present invention provides a method of installing a completely new bottom in an oil tank, the original bottom of which has become so corroded as to be unfit for further service. All fabrication and construction of the false bottom may be effected in the field without resort to prefabricated special shapes or structures and a construction results which is strong, durable and highly efficient for continuation of the function for which the tankis adapted. Furthermore, it will be apparent that. in the event of the false bottom eventually becomlng so corroded as to render the tank inemcient, another of these false bottoms identical in practically every respect to the one herein shown and described may easily be built in place upon the corroded false bottom in the same manner as the corroded false bottom was installed over the original bottomof the tank, the additional false bottom merely being laid upon the upper face of the horizontal flange I8 of thesealing ring with a sand cushion between it and the false bottom I2 and4 an additional sealing ring placed upon the new or additional false bottom and sealed in place and tested ln any of the manners heretofore mentioned. This procedure may, of course, be continued indefinitely, depending upon the condition of the side walls 5 and the capacity of the tank desired.

The foregoing specification has been copied from my patent application ser. No. 181,549,

led December 24, 1937, in which division was required by the Patent Olhce between process and apparatus claims. Apparatus claims were .eft in that case While process claims are covered in this divisional case.

What is claimed is:

1.. 'I'he herein-described method oi repairing oil storage tanks whose bottoms have become corroded and of testing the water tightness of the repaired construction which comprises, spreading -a layer of .loose aggregate material upon the corroded bottom, placing a false bottom upon the surface of said material, intermittently welding the peripheral edge of said false bottom to the side wall of the tank, placing a sealing ring between the side wall and the false bottom adjacent to and overlying the peripheral edge of the latter, continuously welding the sealing ring'to the side wall and to the false bottom, providing an opening through the sealing ring, forcing a uid through said opening and ultimately into the aggregate illled space beneath the false bottom to reveal any points of leakage in the construction, and thereafter sealing up the opening in the sealing ring.

2. The herein described method of repairing in situ stationary metallic storage tanks of largecapacity, comprising introducing through the top of the tankI a supplemental bottom member having an approximate lit around its periphery with the upright side wall of the tank, supporting the supplemental bottom'member spaced above the main bottom of the tank, then introducing through the top of the tank a sealing ring and placing said ring in position with its bottom edge resting on the upper side of the supplemental bottom member inwardly from the periphery thereof and the top edge ofthe sealing ring resting against the inner face of the upstanding peripheral wall of the tank upwardly yfrom the supplemental bottom member, and then vwelding andthereby liquid sealing the bottom edge of the sealing ring to the supplemental bottom member throughout the length-of said bottom edge and also welding and thereby liquid sealing the top edge of the sealing ring to the upstanding peripheral side wall of the tank throughout the peripheral length of said top edge.

3. The herein described method of repairing in situ stationary metallic storage tanks of large capacity comprising spreading loose granular material on the upper side of the -bottom of the tank, introducing through the top of the .tank a supplemental bottom'member having an approximate ilt 'around its periphery with the upright side wall of the tank and placing the same upon said granular material, then introducing through the top of the tank a sealing ring and placing said ring in position with its bottom edge resting on the upper side of the supplemental bottom member inwardly from the periphery thereof and the top edge .of the sealing ring resting against the inner face of the upstanding peripheral wall .of the tank upwardly from the supplemental bottom member, and then welding and' thereby liquid sealing the bottom edge of the sealing ring' to the supplemental bottom member throughout the length of said bottom edge and also welding and thereby liquid sealing the top edge of the sealing'ring to the upstanding peripheral side wall of the tank throughout the peripheral length of said -top edge.

4. The herein described method of repairing tanks whose bottoms have become corroded and of testing the water tightness of the repaired construction which comprises, placing supporting means upon the corroded bottom, placing a false bottom upon said'supporting means, placing a sealing ring between the side wall and the false bottom adjacent to and overlying the peripheraledge of the latter, continuously welding the sealing ring to the side wall and to the false bottom, providing an opening through the sealing ring, forcing a fluid through said opening and ultimately beneath the false bottom to reveal any points of leakage in the construction,l and thereafter sealing up the opening in the'sealing ring.

5. The herein described method of repairing in situ stationary metallic storage tanks of large capacity, comprising introducing through the. top'of the tank a supplemental bottom member having an approximate lit around itsv periphery Withthe upright vside wall of the tank, supporting the supplemental bottom member Ispaced above the main bottom of the tank, intermittently welding the peripheral edge of the supplemental bottom member to the side wall of the tank, then introducing through the top of the tank a sealing ring and placing said ring in position with its bottom edge restingV on the upper side ofthe supplemental bottom member inwardly from the periphery thereof and the top edge of the sealing ring resting against the inner face of the upstanding peripheral wall of the tank upwardly from the supplemental bottom member, and then welding land thereby liquid sealing the bottom edge of the sealing ring to the supplemental bottom member throughout the length of said bottom edge and also welding and thereby liquid sealing the top edge of the sealing ring to the upstanding peripheral side wall of the tank throughout the peripheral length of said top edge.

HENRY O. WALKER. n

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