US1758225A - Floating-roof tank - Google Patents

Description

y 1930. s. P. JOHNSON 1,758,225

FLOAT ING ROOF TANK Filed Dec 8, 1926 2 Sheets-Sheet l 10 10 /1f & 11

J 41 J I 4 X 11 22 /5 1- Patented May 13, 1930 UNITED STATES PATENT OFFICE SIDNEY P. JOHNSON, OF SAN FRANCISCO,

COMPANY OF CALIFORNIA, OF SAN FR DELAWARE FLOATING-ROOF TANK Application filed December 8, 1926. Serial No. 153,302.

This invention relates to liquid storage tanks of the type which have a roof which floats upon the surface of the liquid in the tank; it is customary in such tanks to employ means for substantially preventing the evaporation of the liquidfrom the annular space between the tank wall and the floating roof. The advantages of floating roofs for such tanks are well known, and one of the principal problems in their construction is to provide an adequate seal for this annular space. It is impracticable, by ordinary construction methods, to produce a roof that will operate efl'ectlvely where there is a very small clearance between the floating roof and the tank, on account of irregularities which are incidental to the form of the tank wall. The evaporation loss from the annular space between such a floating roof and the tank wall Will be considerable unless some kind of expansible and contractible seal is used between the roof and the-tank. It is not necessary that this seal shall be absolutely gas-tight, however, as long as the liquid surface exposed is reduced to a small fraction of the whole area of the liquid.

The general object of this invention is to provide a seal for the annular space of such a tank which will operate without the formation of explosive gas and air pockets, at the same time providing means for substantially preventing, evaporation at this point, and providing for maintaining the roof centered in the tank, so that it is guided as the roof rises and falls with the liquid level.

Another object of the invention is to provide for sealing substantially all of the annular space Without necessitating the use of :1V flexible diaphragm or apron such as is sometimes used to seal this space. While such diaphragms or aprons have some advantages, they are likely to deteriorate or soak up oil through their capillarity.

Another object of the invention is to provide means for mounting the movable members in such a way that their connections are pivotal connections, thereby avoiding the excessive friction which would be developed if mere sliding connections were used.

Further objects of the invention will appear hereinafter.

The invention consists of the novel parts and combination of parts to be described hereinafter, all of which contribute to produce an eflicient floating roof tank.

A preferred embodiment of the invention is described in the following specification, 'while the broad scope of the invention is pointed out in the appended claims.

In the drawing:

Figure 1 is a plan of substantially onehalf of a floating roof tank embodying my invention.

Figure 2 is a vertical section through the tank, and particularly illustrating the construction of the roof which enables it to prevent the formation of gas pockets under it.

Figure 3 is a vertical section taken through the edge of the roof and the adjacent wall of the tank, upon an enlarged scale, certainparts being broken away. This particularly illustrates the means for centering the roof and for sealing the liquid in the annular space between the floating roof and the tank wall.

Figure 4 is a developed elevation, showin a short portion of the rim or edge of the roo and further illustrating details of the sealing means, certain parts being broken away.

In the drawing, 1 represents a tank of the usual cylindrical form, in which the liquid 2 is stored. On this liquid 11 floating roof 3 is supported, said roof consisting of a deck 4, which is substantially circular but preferably consists of a many sided polygon provided at its edge with an upwardly extending flange 5. The deck 4 is constructed in such a way that its central point 6 is slightly depressed, so that the deck inclines upwardly slightly toward its edge. With this construction, any gas forming in the liquid naturall moves toward the edge of the roof and will not accumulate in pockets under it. In order to give the deck this general form, I prefer to construct it of pyramidal form; that is to say, the deck is constructed in the form of an inverted pyramid, with a very large angle at the apex of the pyramid, which is disposed at the central point 6 of the roof. To this end, the deck 1s constructed of a plurality of substantially triangular sections or sectors 7. These sectors are constructed of flat form and are built up of plates riveted together and at their inclined-side edges, they are connected together by angle-iron stiffeners 8 which are riveted to the abutting edges of the sectors.

In order to brace the roof and maintain it in its pyramidal form, I provide bracing on its upper side, said bracing comprising a center standard or short mast 9, from which di agonal tie-rods extend outwardly to the edges of the roof. These tie-rods 10 'may extend directly over the radial angle-irons 8 and they may he supported on intermediate standards or stanchions 11 (see Figure 2). Their outer ends attach to the parts 8.

The side edge or flange of the roof is disposed at sufficient distance from the wa l 12 of the tank to form an annular space 13. In order to seal this annular space; that is to say, to substantially cover the liquid. without the possibility of forming gas pockets at this point, I provide sealing means that extends under the edge of the roof and maintains contact with the tank wall. This sealing means is constructed so that it substantially cc vers all of the area of the annular space but permits escape of vapors, thereby preventing the formation of gas pockets under it. For this purpose I prefer to provide a plurality of shoes 14 corresponding to the sides of the polygon formed by the roof. These shoes have their side faces disposed slightly apart to permit independent and free movement of the shoes and they are constructed so that their inner edges 15 project under the edge of the roof (see Figure 3). Each shoe swings on its support in a radial plane with respect to the center of the tank. They maybe constructed of sheet metal and have substantially the form indicated; that is to say, they preferably have a round or curved outer face or nose 16 curved in a vertical plane (see Figure 3) which lies near or against the wall 12 of the tank.

Associated with the shoes 14, I prefer to provide means for maintaining the roof 4 centered in the tank, and this means includes yielding means for holding the shoes in an outwardlyextending relation. "In order to accomplish this, I mount the shoes so that they may rotate bodily in an are about a. substantially horizontal axis on the roof. In the pres-- ent instance, I provide each shoe with a pair of arms 17 which extend upwardly, and which are mounted to rock on a pivot bar 18 supported on stanchions 19 which extend up from the deck a short distance inside of the flange or rim 5. The upper portions of these arms 17 are substantially hOIlZOIItiIL'bUt their outer portions have downwardly disposed extensions '20 which are rigidly secured to the shoes. These shoes need not be buoyant and are preferably of sufficient weight to substantially overcome theirnatural buoyancy.

Associated with each pair of arms 17, I provide, means for yieldingly urging the arms in a direction to hold the shoes substantially against the tank wall. For this purpose, I may provide the arms 17 with inner extensions 21 which carry adjustable weights 22, and the arms may also be provided with coiled springs 23, respectively, which exert an upward thrust against the arms on the outer sides of the pivot rods 18, so as to assist the action of the weights 22. I prefer to construct the weight arms 21 in such a way that if the edge of the roof should approach unduly toward the tank wall at any particular point. then the lever arm of the weight will increase so as to give the weight an increased le"'erage in forcing the shoe out to its normal position. W'hile the use of weights, on account of this advantageous effect, is desirable, if desired. the weights can be omitted and the springs be used alone. The springs, however, cooperate with the weights when the weights are used. to make the arms more quickly responsive to changes in position of the roof, if it should get out of center.

The lower ends of the springs may be mounted in spring cups 24, respectively, which are supported on radial braces 25, in the form of angle-irons, which connect the upper edge of the flange 5 with the stanchions 19. In order to enable the springs 23-to be adjusted, the lower ends are supported on spring seats 26, which may be forced upwardly by an adjusting screw 27 which passes up through the horizontal flange of the angle brace 25.

If desired, the elevation of the pivot bar 18 may be made adjustable. In order to accomplish this, this pivot bar 18 may be supported on two angle brackets 28 secured by a bolt. 29 passing through an adjusting slot 30 in the brackets.

In order to provide a close fit between the inner portion of each shoe and the edge of the roof, I construct the roof at its edge with a curved face 31, the axis of curvature of which is at the axis of the bar 18. and the adjacent face 32 of the shoe 14 is similarly curved aboutthis axis. In this way, as the shoes move in or out, they still maintain their faces quite close to the edge of the roof.

.The ends of the shoes 14 lie quite close together, as illustrated in Figure 1, so that while. they substantially close or cover the annular space, they will permit an outward movement of any gas which forms under the roof and which moves outwardly on its under side.

The curved face or plate 31 and theshoes 14 are located substantially at the level of the liquid 2, which is indicated by the line 33. These faces need not actually touch each other and hence they offer no frictional resistance to the movement of the shoes. If desired, turn-buckles may be provided in the tie-rods 10.

The polygonal shape for the deck is preferable to a circular form because it is easier to fit the shoes 14 to a straight side. If the circular form were used the upper face 32 of each shoe would have to be curved in two directions instead of merely of cylindrical form.

It is understood that the embodiment of the invention described herein is only one of the many embodiments this invention may take, and I do not wish to be limited in the practice of the invention, nor in the claims, to the particular embodiment set forth.

The slightly pyramidal form of the roof gives it a certain amount of stiffness and eliminates the quality of limberness inherent in a perfectly flat roof floating on a liquid.

\Vhat I claim is:

1. In a sealing construction for liquids, the combination of a tank to contain the liquid. a floating roof supported on the liquid so that an annular space is formed between the edge of the roof and the tank wall, a plurality of shoes having a support with a single pivotal axis on the roof, so as to swing bodily in an are about the pivotal support, and means for yieldingly pressing the shoes outwardly to hold their outer faces adjacent the tank wall, said shoes being disposed with their ends spaced slightly apart so that they are independently movable and substantially seal the annular space between the roof and the tank wall.

2. In a sealing construction for liquids, the combination of a tank to contain the liquid, a floating roof supported on the liquid so that an annular space is formed between the edge of the roof and the tank wall, a plurality of shoes haviiig pivotal supports on the roof with their inner ends extending under the edge of the roof. the upper faces of said inner ends and the adjacent edge of the roof being curved about the said pivotal support as an axis, and means for yieldingly pressing the shoes outwardly to hold their outer faces adjacent the tank wall.

3. In a sealing construction for liquids, the combination of a tank to contain the liquid, a floating roof supported on the liquid so that an annular space is formed between the edge of the roof and the tank wall, a plurality of shoes substantially filling said annular space, arms corresponding tr each shoe and having a pivotal support on the roof, said shoes being disposed substantially at the liquid level with their inner ends projecting under the edge of the roof, and means for yieldingly pressing the shoes outwardly to hold their outer faces adjacent the wall of the tank.

4. In a sealing construction for volatile liquids, the combination of a tank to contain the liquid. a floating roof supported on the liquid so that anannular space is formed between the edge of the roof and the tank wall, said roof having a substantially circular deck slightly dished so that it is depressed at its middle point whereby gases forming under the deck will move progressively toward said annular space, a plurality of independently movable shoes supported on the roof with their end faces disposed slightly apart to permit their independent movement, lying on the surface of the liquid, said shoes projecting out radially from the edge of the roof and substantially filling the said annular space, and means for yieldingly pressing the shoes outwardly toward the wall of the tank.

5. In a sealing construction for volatile liquids, the combination of a tank to contain the liquid, a floating roof supported on the liquid so that an annular space is formed between the edge of the roof and the tank wall, a plurality of shoes substantially sealing the space between the roof and the tank wall and in contact with the liquid, a plurality of arms carrying said shoes. pivotally supported on the roof and operating to hold the inner ends of the shoes under the edge of the roof, and counterweights associated with the arms respectively, to force the shoes yieldingly toward the tank wall.

6. In a sealing construction for volatile liquids, the combination of a tank to contain the liquid, a floating roof supported on the liquid so that an annular space is formed between the edge of the roof and the tank wall, a plurality of shoes substantially sealing the space between the roof and the tank wall and in contact with the liquid, a plurality of arms carrying said shoes. pivotallv supported on the roof and operating to hold the inner ends of the shoes under the edge of the roof, and a spring associated with the arms respectively, to force the shoes yieldingly toward the tank wall.

7. In a sealing construction for liquid the combination of a tank to contain the liquid, a floating roof supported on the liquid so that a substantially annular space is formed between the edge of the roof and the tank wall. a plurality of shoes pivotally supported on the roof, and means for yieldingly pressing the shoes outwardly to hold their outer faces adjacent the tank wall, said shoes capable of swinging bodily in a radial plane on the pivotal support so as to extend beneath the outer edge of the roof and being disposed adjacent each other so that they substantially fill the annular space between the roof and the tank wall.

8. In a sealing construction for liquid the combination of a tank to contain the liquid,

a floating roof supported on the liquid so that an annular space is formed between the 7 edge of the roof and the tank wall, a plurality of independently movable shoes pivotally supported on the roof so as to swing in and out in a radial plane and substantially in contact with the edge of the roof, and means for yieldingly pressing the shoes outwardly to hold their outer faces adjacent the tank wall. said shoes being disposed adjacent to each other and in contact with the liquid from the roof to the tanks wall so that they substantially seal the annular space between the roof and the tank wall and operating to permit escape of vapors between them and thereby prevent formation of a gas pocket under the shoes.

9. In a sealing construction for volatile liquids the combination of a tank to contain the liquid, a floating roof supported on the liquid so that an annular space is formed between the edge of the roof and the tank wall, said roof having a substantially circular deck slightly dished so that it is depressed at its middle point whereby gases forming under the deck will move progressively toward said annular space, a plurality of shoes supported on pivotal axes on the roof and substantially filling the said annular space, and means yieldingly pressing the shoes outwardly toward the wall of the tank, the said shoes having their upper faces curved about the said pivotal axes and projecting under and substantially against the edge of the said roof.

10. In a sealing construction for liquids, the combination of a tank to contain the liquid, a floating roof supported on the liquid so that an annular space is formed between the edge of the roof and the tank wall. a plurality of shoes substantially filling said annular space and pivotally supported on the roof with their inner ends extending under the edge of the roof, the upper faces of said inner ends being curved about said pivotal support as an axis so as at all times to be in close juxtaposition to the roof, and means for yieldingly pressing the shoes outwardly to hold their outer faces adjacent the tank wall.

11. An oil tank having a floating roof of smaller diameter than the tank, sealing means interposed between the wall of the tank and the floating roof lying on the surface of the liquid in the tank so as to engage the wall of the tank substantially at the liquid level and operating to substantially cover the area of the liquid between the tank wall and the periphery of the floating roof, thereby preventing the formation of a space in which gas could accumulate, said means constructed so as to permit escape of gas and thereby prevent accumulation of gas pockets below the sealing means, and means for supporting said sealing means on the floating roof.

12. An oil tank having a floating roof of smaller diameter than the tank, a plurality of sealin members interposed between the wall of t e tank and the periphery of the floatin roof lying on the oil and substantially ing the annular space at the oil level between the tank wall and the periphery of the floating roof, said members constructed to permit escape of gas and thereby prevent accumulation of gas pockets below the same, and means for attaching said members on the roof to enable the same to swing in a substantially radial plane with their inner ends extending under the edge of the roof and substantially in contact therewith.

13. An oil tank having a floating roof of smaller diameter than the tank, a plurality of sealing members interposed between the wall of the tank and the periphery of the floating roof lying on the oil and substantially filling the annular space at the oil level between the tank wall and the periphery of the floating roof, said members constructed to permit escape of gas and thereby prevent accumulation of gas pockets below the same, and means for attaching said members on the roof to enable the same to swing in a substantially radial plane with their inner ends extending under the edge of the roof and substantially in contact therewith, said members having noses at their outer ends curved in a vertical plane for engagement with the side wall of the tank.

14. An oil tank having a floating roof of smaller diameter than the tank, a plurality of sealing members interposed between the wall of the tank and the periphery of the floating roof lying on the oil and substantially filling the annular space at the oil level between the tank wall and the periphery of the floating roof, said members constructed to permit escape of gas and thereby prevent accumulation of gas pockets below the same, and means for attaching said members on the roof to enable the same to swing in a substantially radial plane with their inner ends extending under the edge of the roof and substantially in contact therewith, said members having noses at their outer ends curved in a vertical plane for engagement with the side wall of the tank, and means for yieldingly holding the noses of the said sealing members against the tank wall.

15. In a sealing construction for volatile liquids, the combination of a tank containing the liquid. a floating roof supported on the liquid so that an annular space is formed between the edge of the roof and the tank wall, said roof comprising a substantially circular deck, a plurality of shoes lying at the surface of the liquid, means for pivotally supporting the shoes on the roof to swing under the roof at their inner ends, with the upper faces of their inner ends lying substantially parallel to the adjacent face of the roof.

Signed at San Francisco, California, this 19th day of November, 1926.

SIDNEY P. JOHNSON.

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