US2735573A - Floating roof seal - Google Patents

Description

Feb. 21, 1956 Filed May 22, 1955 FLOATING FlNO 2,735,573

ROOF SEAL 5 Sheets-Sheet 1 Fig.

INVENTQR Alexander I? Flno W m meld-M ATTORNEY Feb. 21, 1956 A. F. FINO 2,735,573

FLOATING ROOF SEAL Filed May 22, 1955 s Sheets-Sheet 2 INVENTOR Alexander F. Fino W1... MMQ L ATTORNEY Feb. 21, 1956 A. F. FINO FLOATING ROOF SEAL 3 Sheets-Sheet 3 Filed May 22, 1955 Fig.5

INVENTQR Alexander F F mo ATTORNEY United States Patent FLOATING ROOF SEAL Alexander F. Fino, Warren, Pa., assignor to Hammond Iron Works, Warren, Pa., a corporation or Pennsyivanra Application May 22, 1953, Serial No. 356,661

1 Claim. (Cl. 220-26) This invention relates to storage tanks for oil and oil products, and the like, that are of the type that has a roof or cover that floats on the liquid stored in the tank so that it rises and falls with the liquid-level of that liquid. In such tanks, there is the problem of sealing the annular space between the floating roof and the inner periphery of the shell or wall of the tank. 50 it is an object of this invention to devise a new seal for this space. Such seals are usually supported from the floating roof which in rising and falling causes the seal to slide vertically over the inner periphery of the shell of the tank. Since such tanks are relatively large, this inner periphery rarely has true circular form, and usually has many other and substantial irregularities. So it is another object of this invention to devise a deformable seal that is dependably tight in spite of such irregularities. Again, such seals sometimes have water-retaining pockets, the water of which freezes in winter. Therefore, it is a further object of this invention to devise a floating roof seal that eliminates this problem of freeze-ups. Due to the mechanics of construction, conventional seals contain an annular space that enables vapor to form therein. A still further object of this invention is to eliminate such vapor-collecting spaces and the need of gas-escape means therefrom. Conventional seals are made of metal that has an inherent tendency to abrade the tank shell, so it is another object of this invention to make the seal of non-metallic material and thus avoid all tendency to abrade the tank shell. Another object is to devise a non-metallic seal so constructed as to be substantially stiffer circumferentially than vertically. A still further object is to so arrange the seal and its environment that even when the floating roof is in its extreme lowered position, liquid can be fed into and withdrawn from the tank. In present floating roofs, they are not usually raised to the extreme top of the tank so the upper foot or two of the tank is lost in so far as r storage capacity is concerned. So it is a further object to devise a floating roof that can make use of all the tank storage space when the roof is in its extreme raised position. Yet another object is to devise a floating roof that avoids losses of the stored product due to capillary action between the tank shell and the floating roof with its usual shoes. Another object is to devise a non-metallic seal between the floating roof and the tank that provides a face contact with the tank shell rather than only a line contact. And a further object is to provide electrical connections between the floating roof and the tank shell to bridge electrically therebetween over the nonmetallic seal. 0ther objects will appear as this specification proceeds.

At least some of these objects can be realized by supporting from the floating roof that has a cylindrical periphery a more or less horizontally-extending deck, means for sealing the annular space between the tank shell and the periphery of the floating roof comprising a liquidcontaining flexible annular tube and a deformable band that while supported from the roof, extends between the tube and the shell meanwhile being pressed against the shell by the liquid-containing tube. Supplemental features of the invention for realizing some of its objects include horizontally-extending flexible ribs projecting toward the shell from the band; the band enclosing the tube within a fluid-resistant space; the supporting means therefor, a flexible weather-seal extending from the roof to the shell; the bottom of the tube aligned with the displacement flotation level of the roof; the bottom extension or skirt on the deck that is slotted or has liquid-flow passages therethrough; the rollers on the floating roof are for centering it as it rises and falls and for preventing deck rotation; the rollers are provided with electric conductors for ridding the floating roof of any static electricity by bridging across the non-metallic non-conducting seal; the upwardly-extending runways for the rollers for getting maximum storage capacity when the roof is in its extreme elevation; and still other features hereinafter described in detail.

The invention is illustrated in the accompanying drawings wherein one embodiment of the invention has been chosen for illustrative, but not for limiting, purposes. In the drawings, Figure 1 is an isometrical view of a tank having this invention incorporated therein, but with parts of the tank broken away. Fig. 2 is a plan view with parts broken away. Fig. 3 is a partial vertical sectional view through the lower-left-hand corner of the tank of Fig. 1, showing the floating seal of this invention in larger detail. Fig. 4 is a sectional view of a fragment of the sealing scuff band. Fig. 5 is a side elevational view of one static-conducting roller. Fig. 6 shows a top plan view as to the disposition of such rollers, and Fig. 7 is a partial side elevational view showing how the roof can raise to an elevation partly above the tank top.

In the drawings, 11 indicates the storage tank having a cylindrical vertical wall or shell 12, a bottom 13, and, if desired, a wind-girder 14 around the upper part of the tank. Within the tank is a floating roof or cover indicated generally by 253', having a peripheral wall 16, an upper deck 17 and a lower deck 18. The periphery 16 of the floating roof terminates in a skirt portion 19 having openended slots 23 or other liquid-flow passages. Between the roof 15 and the inner periphery of the tank shell is an annular space 21. From the periphery of the floating roof there extends outwardly a lower shelf or flange 22 made such as by an angle bar and an upper shelf, flange 23, from which is supported a band 24 (sometimes referred to as the scuff band) of flexible material such as reinforced synthetic rubber, having a stiffer backing sheet 25 of nylon or equivalent material, and 21 facing 26 of a wear-resistant resilient material such as reinforced synthetic rubber, from which protrudes horizontally-extending ribs 27. The scuff band 24 is fastened to the lower shelf 22 by bolts 28 passing through an annular bolting bar or ring 39 and to the upper shelf 23 by other bolts 25 passing througi an annular bolting bar or ring The lower shelf 22 at least should extend far enough toward the tank shell to keep the bottom of the tube 24 from sagging significantly therebelow. Thus the shelf should extend from the periphery 16 of the roof about half-way to the tank shell. The upper shelf 23 also has bolted to it an annular weather-shield strip 30 having bevelled outer portion, also made of some slightly resilient material such as neoprene, since it is designed to rub against the shell of the tank weather-proofly as the roof rises and falls, and to protect the scuff-band 24 from direct sunlight. This is sealingly held in place by the bolts 29. The scufl band 24 preferably is an endless band to eliminate field joints and vapor-escape channels.

Between the scuff band 2 and the periphery 16 of the floating roof 15, there is an enclosed liquid-resistant annular space 32, in the lower part of which there is an endless annular liquid-containing deformable tube 33, provided with any suitable filling connection 34. The liquid 35 with which the tube is filled is preferably (but not necessarily) heavier in specific gravity than the liquid stored in the tank, so it can be water, brine or oil, and therefore by gravity it exerts a uniform pressure against the scuff band whereby the scutf band always has facecontact with the tank shell (as opposed to line contact), regardless of tank irregularities. The tube is made of rubber or other substantially equally deformable material. The bottom of this tube is so located that it is substantially at the deck flotation displacement level, shown by dotted line 36. Liquid stored in the tank can be drawn off, or pumped in, through conventional shell nozzles 37, even when the floating roof is in its extreme lowered position as shown in Fig. 3, since the liquid stored in the tank can flow through the liquid-flow passages 29 in the skirt 19 depending from the floating roof, and thus have access to the inlet and outlet nozzles 37. Because the seal of this invention is located at the displacement level, the nozzles are below the seal even when the roof is in its lowermost position.

Figs. and 6 show the use of static electricity conducting spring-pressed rollers bridging around the non-metallic seal from the metallic roof to the metallic tank shell. Rising from the top deck 17 of the floating roof 15, there is a support 40 for a cylindrical casing 41 adapted to house a reciprocable stem 42 ending in a yoke 43 between the arms of which is journalled a roller 44 covered with an electricity-conductive rubber covering or tire 45 adapted to roll against the tank shell 12 as the roof rises and falls. The stem 42 carries inboard thereof a disc 46 with which is connected a spring 47 bearing against a plate 48 that is adjustable axially within the cylindrical casing 41 by means of adjusting screw 49, to increase or decrease the spring-pressure on the roller 44, and thus the degree of spring-load thereon. These rollers are normally disposed 90 apart on the floating roof, as shown in Fig. 6, although more or less can be used depending upon the size of the tank.

At the top of the tank, for each roller 44, there is provided one or more brackets 51,'shown in Fig. 7, having a bracing outer face 52, as shown, and an inner upright face 53 that is aligned with the inner periphery of the tank shell 12, to form a continuation thereof serving as a track on which the rollers roll. 54 represents a laterally extending flange at the top of the tank, that is straddled by the bracket 51. These brackets permit rollers 44 to ride upwardly thereon and thus the roof to rise partly above the top of the tank, to an elevation whereat the displacement level 36 is about even with the flange 54 at the top of the tank, thus letting the tank be filled completely with stored fluid.

In operation, the annular flexible tube 33 is put in place as shown in Fig. 3, and filled with its liquid after being emplaced. Then the scuff band 24 is fastened around it as shown in that figure, being fastened at its bottom to lower shelf 22 and at its top to upper shelf 23, for thus leaving a liquid-resistant space 32 above the tube 33 supported from the exterior of the floating roof, and with the bottom of the tube located just about at the deck flotation displacement level 36. As the floating roof rises and falls, the weight of the liquid in the tube 33 causes the scuff band 24 to be resiliently forcibly pressed against the shell 12 of the tank with uniform pressure. When the floating roof rises, the scuff band is pulled upwardly through its upper margin from the upper flange 23'by a line of pull spaced from the periphery of the roof and when the roof falls, the band is pulled downwardly through its lower margin from the lower flange 22 by a line of pull also spaced from the periphery 'of the roof meanwhile the liquid-containing tube 33 continues to maintain its position deformably pressed against the tank wall. The horizontal ribs 27 molded on the exterior surface of the scuff band 24, tend to flop and ride over the sharp edges, welds, rivets, and other protuberances and irregularities, and thus maintain a tight seal while reducing wear action on the band. Also, these ribs give circumferential stiflness and vertical flexibility without lagging or sagging, and they prevent capillary creep between the contact surfaces. The lower connection of the scuif band is located at the stored liquid displacement level 36. This eliminates any seal vapor space and this stops or precludes seal vapor losses. Such loss is precluded by two means, namely, displacement of the vapor-forming space, and the uniform tightness of the seal against the'shell of the tank, irrespective of irregularities therein. No seal vent is therefore necessary leading from the usual seal vapor space.

Should any ice tend to form, freeze-ups will be eliminated by the flexible tube 33 because during deck movement, the ice will be broken up similarly to the flexing action of de-icers on airplane wings. The new seal is easy to emplace, or to replace. The scuff band is preferably continuous and is th of an inch in thickness. The ribs are th of an inch in height. The weathershield 30 precludes obstructions or water from getting down between the scuff band and the tank shell, and keeps out sunlight from deteriorating the scuff band.

The spring-pressed rollers 44 tend to keep the floating roof centered in the tank and prevent any tendency otherwise to bind. By their frictional contact, they prevent rotation of the roof while it floats. Also, they play an important part in relieving the floating roof of any residual static electricity, since they form a bridging conducting connection between the metallic roof and the metallic tank, around or across the non-metallic seal. Further, by the construction shown in Figs. 6 and 7, they, with the upstanding brackets 51, permit the floating roof to rise to an elevation shown in Fig. 7, that permits the tank to be completely full of stored liquid, something very beneficial for a floating roof tank to do.

The non-metallic flexible seal of this invention has many advantages: 'it permits painting of the inside of the tank if required for certain types of storage; capillary losses of the stored product past the seal are avoided; windage losses are prevented; wetting losses are avoided; it affords face contact with the tank wall instead of the usual line contact; it affords a tight seal in spite of protuberances inwardly extending from the tank wall; it

causes no abrasion of the tank wall; there is no possibility of the roof becoming hung up and later to fall; the deck of the roof can be elevated above the tank top; the roof can be lowered to the tank bottom and still conventional shell outlets can be used since the flow will not be shut off as the seal is above the displacement level; and the seal can be' installed in existing floating roof tanks, of both the welded and riveted types.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claim rather than by the description preceding it, and all changes that fall within the metes and bounds of the claim or that form their functional as well as conjointly cooperative equivalents,

are therefore intended to be embraced by the claim.

I claim:

A liquid storage tank having a cylindrical wall, a bottom, and a floating roof for liquids within the tank adapted to rise and fall with the liquid level in the tank, said roof being of smaller diameter than the inside of said cylindrical wall to provide an annular space between its periphery and the tank, a horizontal annular flange secured to said roof and disposed slightly lower than the displacement level thereof and extending subband and the periphery of the floating roof, a liquid containing flexible hollow member of annular shape disposed in said liquid resistant space and supported partially from said flange and partially from said band, the portion of said band which supports the hollow member being substantially horizontal and the lowermost point of centact between the band and the cylindrical wall being disposed substantially at the displacement level of the roof to minimize gas collecting space between the band and the liquid level of the tank.

References Cited in the file of this patent UNITED STATES PATENTS Bown Mar 2, Stough Apr. 7, Keuhn Dec. 29, Horton et al. July 6, Haupt et a1. Feb. 13, Rivers Oct. 6, Oifenhauser Feb. 15, Boberg July 25,

FOREIGN PATENT Great Britain June 24,

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