US2788913A - Centering device for floating roof - Google Patents

Description

April 16, 1957 J. w. ALLEN CENTERING DEVICE} FOR FLOATING ROOF Filed Oct. 5, 1955 INVENTOR. 0km WKZZZeZZ,

United States Patent 2,7ss;91s Dizvicii roe FLOATiisIG noon ronayv. sires, teenage,- 111:, ass n t Gni-al American Trah's'portafion Corporation, Chicago, 11]., a corporation of New York 7 'A ifiietibn October 5, 1955, Serial No. 334329 4 Claims. (Cl. 220 26) .Thisinyentionrelates to storage tanks andhas for its principal object the provision of a new and improved device ofthis kind. V t I,

.1: is am n b t f the inventidn t v de a improved meghani'sm for maintaining a floating roof centank-mw Another object of the invention is to provide a floating roof centering device which can be manufactured, installed and maintained in proper working condition at n -4 H. u A

.ns l a ethet, ie.pit e nv t n is 16 P ov de a centering device for afloating roof located solely between t eTedse 9 the r e san e nk W la d h t f epr tected from the weather by the vapor seal forming devices t e s. r, Still,anotherobject ofthe inventionis to provide a device for centering a floating roof in a tank which is of rugged construction and is not deteriorated by corrosion dvt i i e.

Further objects of the invention hot specifically mentionedhere will be apparent from the detailed description andiclaims which follow, reit'ere'nce being had to the acmitpan in w nss n i h a P e r embodiment ofthe invention is shown by wayof example and in which: Fig. l, is a fragmentary plan view of a tank and roof showing the pusher device installed therebetween; Fig. 2 is an elevationalview, partly. in section, along theline 2-2 of Fig. 1, looking in the direction of the arrows; J Fig, 3 is'a cross sectional view taken substantially along the line 3;3 of Fig. 1, looking in the direction of the IQW ;.3 d..

Fig. 4 is a view similar to Fig. l, showing a modified qrm o t s uc r.

C -ylindrica l tanks disposed with their axes vertical and equipped yyith roofs which float; upon the surface of liquid stored in the tank are commonly used'for the storage of petroleum products and the like. Such roof "structures are equipped with shoes supported onthe roof and disposed on the inside surface of shell to form a seal therebetween. Vaporproof membranes are connectto the uppe'r'e'nds'ofthe seal and to the roof'adja'cent 'it's periplieryto'forhi "a vapem'gntsal between the roof and the ea so that 'evehi'fth'e l qu d stored in'the tank is highly tenths, losses "due to evaporatioh will be minimized.

In such structures the roof is supported upon the surface of the liquid by pontoons, including an outer pontoon extending around the periphery of the roof. Obviously, for the proper functioning of a device of this kind, the roof must be maintained centered, or very nearly centered, on the axis of the tank. Numerous devices have been provided heretofore to maintain such centering of the roof and the present invention relates specifically to such centering devices and provides a new and improved device which is inexpensive to install and maintain and is of such simple construction as to remain in proper opera- 2,788,913 m fiatent ed Apr; '16, 1957 tiye condition over a long period of time with a minimum of maintenance. e

In its preferred form, the centering device of the present invention consists of arcuate brackets pivotally mounted ,upon the roof in pairs and tensioned to be drawn together, thereby to exert forcesextending radially outwardly from the roof and against the shoeto maintain that shoe tightly engaging the inner surface of the tank wall. In theevent that forces such as prolonged winds in a given direction tend. to move, the roof towards oneside of the tank, the bracketswill be spread apart against the tension tending to pull them together, and the force exerted bythe brackets on the shoe and through it on the wallof the tank will be increased on the side of the roof towards which it has a tendency to. move. On the side of. the tank away from which the roof moves, the brackets will move towards each other and the force exerted thereby on the shoe and tank will be decreased to facilitate maintaining the roof centered.

The centering device of the present invention is located solely between the outer periphery of the roof and the tank wall engaging shoe and beneath the vapor tight seal therebetween in which position it is completely shielded from the weather and not adversely affected by the elemerits. The centering device is located completely between the roof and the shoe and does not extend below the roof or the shoe, and therefore does not in any way interfere with the travel of the roof up and down in the tank throughout the entire range of movement that the roof is designed to make.

The invention will be best understood by reference to the drawings wherein the outer wall or shell of the tank is shown at 1, the deck of the roof at 2, and the outer periphery or rim ofthe roof at 3. As will be understood by those skilled in the art, floating roofs of this type are equipped with a boxlike pontoon that extends completely around the periphery of the roof and provides the necessary buoyancy to the roof. Fitted against the inside surface of the shell 1 is a shoe 4 that likewise extends completelyaround the shell and forms a seal thereagainst. The shoes of this type are usually made in sections and equipped with vaportight seals between the sections, thereby enabling the shoe to maintain a tight contact with the tank ,even though the walls or shell thereof be slightly out of round. The shoe ,4 is supported .upon the roof of the tank by a plurality of hangers forming no part of the instant invention and therefore omitted from the drawing to avoid 'anunnecessary complication thereof.

Fixed to theupper apart of the shoe 4 and extending therefrom to the. outer periphery of the roof 2 is a flexible vaporproof membrane 5 which cooperates with the shoe to form a vaportight seal betweenthe roof and tank shell. The details of this seal likewise form no part of thepresent invention.

The centering device of the present invention consists of a pair of bracketsltl and 11 pivotally mounted upon ,the vertical outer wall 3 of the roof, as indicated at 12.

Eachof the brackets 10 and 11' is generally J-shape'd having anarcuate end remote from the pivot 12 which engages the shoe 4 and exerts pressure therea gainst, as will presently appear. The brackets 10 and 11 are maintained in a horizontal position by suitable braces 13 fixed to the brackets and pivotally connected to the wall 3, as indicated at 14. To facilitate ease of installation, the assemblies thus formed are mounted upon bases 15 which can be readily attached to the wall 3 of the tank by welding, riveting or bolting. v

Extending between the brackets 10 and 11 is a flexible tension member 16, preferably a chain, at the center of which a weight 17 is hung. Gravity acting upon the weight tends to pull it downwardly, thereby exerting force the tension in the device that aids the movement.

transmitted by the chain 16 to the brackets 10 and 11 and tending to rotate them about their pivots toward each other. Thus the brackets 10 and 11 are made to exert outwardly extending force on the shoe 4 to maintain it tightly against the shell 1 and to maintain the roof centered in the tank. When the roof is centered, the brackets 10 and 11 are in a normal position, such as is shown in 'the drawing. It will be noted that as a result of the arcuate shape of the brackets 10 and 11, the distance between the pivots 12 and the pointof engagement of the bracket with the shoe 4 increases as the brackets move towards each other and decreases as they move apart.

Should forces such as wind acting upon the roof force it oif-center, thus decreasing the distance between the outer wall 3 of the roof and the tank wall 1, brackets 10 and 11 will thus be rotated away from each other, chain 16 will be moved upwardly so that the point of attachment of weight 17 thereto is more nearly in line with the ends of the chain, and as a consequence the force tending to rotate brackets 10 and 11 towards each other will thereby be increased, with the result that the pressure exerted on the tank wall by the brackets will be increased to oppose the forces tending to move the roof off-center.

On the side of the tank away from which the forces acting on the roof tend to move the roof, the distance between the outer wall 3 and the tank shell 1 will be increased. Weight 17 will draw the brackets 10 and 11 towards each other thereby increasing the angularity of the chain 16, with the result that the component of force placed on the chain by the weight 17 and acting in a horizontal direction will be lessened thereby making it easier for the diametrically opposed brackets to push the roof back into the center of the tank.

Thus it will be seen that with the centering device of the present invention installed on a floating roof, movement of the roof off-center will increase the tension in V the'device that opposes such movement and will decrease As a result, movements of the roof off-center are limited to small amounts and the roof is thereby maintained centered with sufficient accuracy to permit its proper functioning. V

As will be seen, particularly in Fig. 3, the centering device of the present invention is located entirely in the space between the outer wall 3 and the shell and beneath the vapor seal where it is protected from the weather and consequently is not deteriorated thereby. The centering device does not project below the roof and shoe, and consequently in no way interferes with travel of the roof up and down in the tank throughout the entire range of such travel that the roof is adapted to make.

The tensioning arrangement, consisting of the weight 17 and flexible member 16, is advantageous in that it is rugged and forces generated in it are dead weight forces which will exist with a minimum interference from corrosion and the like. In certain instances it may be advantageous to tension the brackets and 11 by means of a spring such as 20, Fig. 4. The spring is connected to the brackets by threaded rods 21 and 22 which provide for a certain amount of adjustment of the tension of the spring. Obviously, as the brackets are moved away from each other, the spring is elongated and the tension in it thereby increased. As the brackets move towards each other, the spring is shortened and its tension decreased.

Thus it will be seen that the principle of operation of the modification shown in Fig. 4 is identical with that hereinbefore described and ,need not be described in further detail.

The centering device of the present invention being composed of simple parts can be made rugged economically and when installed upon the tank roof will remain in proper operative condition upon the tank roof will remain in proper operative condition with a minimum of maintenance. Since the centering devices are located beneath the vapor seal, they are not aifected by weather and are subject only to the efiects of the vapor rising between the roof and shoe, which vapors ordinarily have little or no effect upon the brackets which preferably are composed of iron or steel. I

While 1 have chosen to show my invention by illustrating and describing a preferred embodiment of it, I have done so by way of example only, as there are many modifications and adaptations which can be made byone skilled in the art within the teachings of the invention.

Having thus complied with the statutes and shown and described a preferred embodiment of my invention, what I consider new and desire to have protected by Letters Patent is pointed out in the appended claims.

What is claimed is:

l. The combination with a vertically disposed cylindrical tank having a roof structure floating upon the surface of liquid therein and containing an outer vertically disposed cylindrical wall, and means including 'a shoe supported on and spaced from said roof and engaging the inner surface of the tank and a flexible membrane extending between the shoe and roof for forming a vaportight sealbetween the tank and roof in all positions of the roof; of means for maintaining the roof centered in the tank disposed entirely below the seal and between the roof and the shoe and comprising: a plurality of pairs of rigid lever arms slidably engaging the shoe and pivotally mounted upon the roof for rotation around vertical axes, the pivotal connections of each pair of arms being closer together than the points of contact of said arms with the shoe; and means extending between the arms of each pair tensioned to rotate the arms toward each other thereby to exert a force outwardly on the shoe tending to maintain the roof centered in the tank. 7 V

2. Centering means as claimed in claim 1, in which the lever arms are arcuate and are pivotally mounted upon the outer vertical wall of the roof.

3. Centering means as claimed in claim 1, in which the lever arms are connected together by a flexible member that is tensioned by a weight hung thereon at the middle thereof.

4. Centering means as claimed in claim 1, in which the tensioning means urging the lever arms together are springs adjustably connected to the lever arm's.

References Cited in the file of this patent UNITED STATES PATENTS Graham June. 10, 1952

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