US3055533A - Primary seal for floating roofs - Google Patents

Description

Sept. 5, 1962 E. EEEEE EEAL 3,055,533

PRIMARY SEAL FOR FLOATING ROOFS Filed Jan. 23, 1961 I 2 Sheets-Sheet 1 Z0 go 2.

P 25, 1962 R. REEsE ETAL 3,055,533

PRIMARY SEAL FOR momma ROOFS Filed Jan. 25, 1.961 2 Sheets-Sheet 2 v fir/awnifiat/7Q r0] fee 66, Ivan l lflz asmzj/eg' United States Patent 3,055,533 PRIMARY SEAL FOR FLOATING ROOFS Richard Reese, Park Forest, and Ivan L. Wissmiller, Chicago, Ill., assignors to Chicago Bridge & Iron Company, Chicago, Ill., a corporation of Illinois Filed Jan. 23, 1961, Ser. No. 84,288 11 Claims. (Cl. 220--26) This invention relates to an improvement in a floating roof tank, used for the storage of volatile liquids such as certain petroleum products, and more specifically, an improved method and means for effecting a seal between the floating roof and the outer shell of the tank.

The floating roof tank has been, and still is, the best means for storage of certain types of volatile liquids. The floating roof tank consists essentially of a bottom, a cylindi cal shell and a circular roof which rests on the surface of the liquid stored in the tank. The floating roof, because it is at all times in direct contact with the upper surface of the liquid, serves to reduce evaporation losses to a minimum, and to prevent the formation of an explosive combination of air and liquid vapor. 'Ilhe circular roof has a diameter that is less than the cylindrical shell in which it is contained because dimensional variations from welding shrinkage, temperature variations during use, and the probability of out-of-roundness in the cylindrical shell require clearance to be provided. Outof-roundness is local distortion of'the cylindrical shell caused by uneven foundation settlement, imprecise fabrication or erection, and unusual live loads such as high winds.

On account of the excessive evaporation loss that would otherwise occur, a suitable device for sealing the annular space between the circular roof and the cylindrical shell must be incorporated.

There are numerous types of floating roof seals in the literature. It is the purpose of this invention to provide a seal which does not require mechanically moving hangers. Tubular seals have also been employed in the past but they have been subject to puncturing. The present invention provides a self-supporting tubular seal which, if punctured, is still efiective.

The invention will be better understood from the following detailed description thereof, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a vertical broken section of a portion of the tank and roof and seal;

FIGURE 2 shows a modified version of the seal of FIGURE 1 using an apron to further limit leakage;

FIGURE 3 illustrates the position of the tubular seal when the roof is rising;

FIGURE 4 is a similar view illustrating the position of the seal when the roof is lowering; and

FIGURE 5 is a view of another version of the invention.

Referring to the accompanying drawings, the instant invention comprises a tubular seal formed in two sections 10a and 10b of a thin, flexible sheet material such as a rubberized fabric shaped by a number of relatively thin slabs 11 of a low density resilient material, such as polyurethane foam, sponge rubber, sponge cellulose or matted glass fibers coated and held together by a resilient binder. It is desirable to use a material for the impervious flexible sealing fabric that resists abrasion, atmospheric weathering and deterioration from contact with the stored product. The preferred material fabric consists of woven nylon fabric impregnated with a synthetic rubber such as buna-N, buna-vinyl, and polyurethane filled with nylon insert. The preferred embodiment has two outside layers of buna-N and an inner layer of the sandwich of woven nylon, having a total thickness of about 0.10".

3,055,533 Patented Sept. 25, 1962 For the resilient material within the seal, it is desirable to select a mass made of glass fibers having nominal diameters less than 0.00015". One type of fiberglass blanket which has been used is the type manufactured and marketed by the Johns-Manville Company under the name Microlite which has a phenolic binder and a density of about 1 pound per cubic foot. In the preferred embodiment the resilient slabs 11 are rectangular bats in sufficient number and size effectively to seal the annular space between the roof and the tank wall 20. Each of the rectangular bats is encased in polyethylene film 12 or any other suitable film material permitting easy slippage. -It is important that the resilient slabs 11 be installed in the seal with the smooth film 12 extending vertically between adjacent slabs to permit free relative sliding of adjacent slabs, and to prevent the resilient mass from being torn apart by the combined forces introduced in a tight rim space during raising and lowering movements. The film material 12 is connected at the top and bottom of the slabs to form an enclosure for each slab, thereby providing a limit for the sliding thereof. Attachment of the film 12 is made with tabs 13 and 14 so the slab adjacent the rim of the floating roof cannot slide relative thereto. The integral film enclosures limit the sliding of the remaining layers so that the outermost layer of resilient material will not slide vertically past the inner layer as the roof moves up and down as shown in FIGURES 3 and 4.

FIGURE 1 shows the tube 10 suspended from upper support rings 15 and 16, and similar lower rings 17 and 18. These rings, like tube 10, encircle the roof and are formed of curved bars which follow the periphery of the roof. Tabs 13 and 14 and the separate portions 10a and 1012 which form the tubular seal 10 are clamped between the support rings, e.g., 15 and 16, which are held together by means of bolts 19.

Hanger bars 21 spaced at approximately equal intervals around the periphery of the rim serve as tension members as the roof moves up and compression members as the roof moves down. The hanger bars are bolted 22 to the rim of the roof and support the rings 15, 16, 17. and 18 through bolts 19 as shown.

Installation of the seal assembly is made with the support rings, tabs and hanger bars in place. This assembly is performed above the rim of the pontoon. When the assembly is completed, the rings are dropped into place and the hanger bars are bolted to the rim of the roof.

To remove the seal assembly, the bolts 22 attaching the hanger bars to the roof are removed. The entire assembly is pulled out either by lifting the seal from above or by lowering the product level a few feet with the seal assembly tied to the shell of the tank.

Several variations of the embodiment shown in FIG- URE 1 can be made. Thus, other suitable structural members can be used in place of hanger bars 21 or support rings 15, 16, 17 and 18. The use of bars as described, however, makes fabrication of the ring components a simple operation. Lower support rings 17 and 18 can be eliminated, if the rolling movement of the seal with respect to the roof is not excessive as the roof changes direction. Only one tab on the seal would be required with this arrangement.

A variation of the invention is shown in FIGURE 2. The seal shown is essentially a duplicate of that of FIG- URE 1, with the addition of an apron 31 which extends from the rim of the roof to the top of the seal and which is held in position by means of bolts 19 and 22, as shown. This apron traps and prevents the escape of any vapors which may flow between the seal 10 and the roof along the hanger bars 21.

Still another embodiment of the invention is shown in FIGURE 5. In this arrangement the top support rings 3 and the hanger bars are eliminated and a flexible material such as the rubberized fabric 41 of the same constnlction as the seal 10 of FIGURE 1 is used. Fabric 41 extends completely around the resilient slabs 11 and the polyurethane slidable film 12. The lower support rings 17 and 18 are bolted to the tab 42 by the bolts 19, giving the weight necessary to hold the entire sealing mechanism in its proper position. The sealing fabric 41 extends to the rim of the roof where it is fastened by bolts 22. The sealing fabric is vulcanized or otherwise joined to itself at the inner top edge of the tube, i.e., 43.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art.

What is claimed is:

1. In a cylindrical tank for the storage of volatile liquids, a circular roof having a diameter smaller than the inner diameter of said tank and adapted to float on the stored liquid, and a seal comprising an annular tube of a thin flexible impervious material supported by said roof and disposed in the annular space between the wall of the tank and said floating roof, said tube enclosing a mass of low density resilient material of sufiicient volume to seal said annular space against the escape of vapors of said volatile liquid, said mass comprising a plurality of individual relatively thin annular slabs of said resilient material, said slabs being in vertical face-to-face arrangement, adjacent faces of said slabs being separated by a relatively slippery sheet material which facilitates vertical displacement of said slabs relative to each other.

2. The device of claim 1 in which said 'low density resilient material is selected from the class consisting of polyurethane foam, sponge rubber, sponge cellulose and matted glass fibers.

3. The device of claim 1 in which said low density material is polyurethane foam.

4. The device of claim 1 in which said low density material is sponge rubber.

5. The device of claim 1 in which said low density material is sponge cellulose.

6. The device of claim 1 in which said low density material is matted glass fibers.

7. The device of claim 1 in which said annular tube is supported by at least one annular ring to which said tube is attached, and said ring is supported by a plurality of hanger members attached to said roof.

8. The device of claim 1 in which said slippery material is a smooth synthetic plastic film.

9. The device of claim 1 in which said slippery material is a polyethylene filrn.

10. The device of claim 1 in which said impervious flexible sealing fabric consists of a. woven plastic fabric impregnated with a synthetic elastomer.

11. The device of claim 1 in which said impervious flexible sealing fabric consists of a woven nylon fabric impregnated with a synthetic elastomer selected from the class consisting of buna-N, buna-vinyl, and polyurethane.

References Cited in the file of this patent UNITED STATES PATENTS 1,722,863 Schurmann July 30, 1929 1,859,718 Santos May 24, 1932 2,523,292 Goldsby et a1. Sept. 26, 1950 2,914,212 Fino Nov. 24, 1959 FOREIGN PATENTS 584,280 Germany Sept. 16, 1933

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