US3511406A

US3511406A - Floating roof

Info

Publication number: US3511406A
Application number: US786856A
Authority: US
Inventors: Lou C Creith; Frank J Daniels
Original assignee: Olin Corp
Current assignee: Olin Corp
Priority date: 1968-12-23
Filing date: 1968-12-23
Publication date: 1970-05-12
Anticipated expiration: 1987-05-12

Description

y 70 L. c. CREITH ETAL 3,511,406

' FLOATING ROOF Original Filed March 28, 1966 INVENTORS.

LOU C. CHE/TH FRANKJ. DANIELS AT TORNEV United States Patent 3,511,406 FLOATING ROOF Lou C. Creith, Allentown, Pa., and Frank J. Daniels, Baldwin, N.J., assignors to Olin Mathieson Chemical Corporation, a corporation of Virginia Continuation of application Ser. No. 538,077, Mar. 28, 1966. This application Dec. 23, 1968, Ser. No. 786,856

Int. Cl. 365d 87/18 U.S. Cl. 22026 4 Claims ABSTRACT OF THE DISCLOSURE This application is a continuation of application Ser. No. 538,077 filed Mar. 28, 1966, now abandoned.

This invention relates in general to an improvement in floating decks for use within a liquid storage tank, and more particularly to an improved floating deck having provision for reducing the vapor'pressure around the periphery thereof.

Floating decks of many types and forms have been proposed and used in tanks designed for the storage of various liquids. Such a deck may form the roof for the storage tank, or may be an additional member within a tank having a fixed root. In either case, the deck floats substantially horizontally on the surface of the liquid in the tank and moves upwardly and downwardly with the surface as the volume of liquid in the tank changes. Thus, protection is afforded from the elements, and evaporation of the liquid stored in the tank is prevented.

The conventional floating deck is of a smaller radial dimension than the tank in which it is installed, in order to provide a clearance space between the periphery of the floating deck and the shell of the tank for accommodating local dimensional variations in the tank shell, known as out-of-roundness in the case of cylindrical tanks, which results from irregularities in the interior surface of the tank shell. To prevent evaporation of the liquid from this clearance space, it is conventional to employ a flexible peripheral sealing ring, thus sealing off this clearance space without impeding the motion of the floating deck as it changes position.

However, the various seals proposed do not impede evaporation as effectively as does the floating deck itself. Accordingly, it has been proposed to include about the peripheral edge of the floating deck a vertical web which extends downwardly into the surface of the liquid stored, as shown, for example, in U.S. Pat. 3,104,775, issued Sept. 24, 1963, to Champagnat. Employing such an expedient, vapor formed directly beneath the deck is retained in the area between the under surface of the deck and the surface of the liquid, thus preventing such vapor from moving into the clearance space below the peripheral seal. Necessarily, such an expedient also prevents vapor which is formed in the clearance space from entering the space directly beneath the deck.

Thus, there is formed about the periphery of the tank a clearance spacedefined by the vertical web, the tank shell, the peripheral sealing ring, and the surface of the liquid storedin which space the generated vapor is trapped. As this space is directly adjacent the tank shell, and since such storage tanks are relatively large in size and are conventionally situated outdoors, it has been 3,5Il,406 Patented May 12, 1970 found that the action of the suns rays on the exterior of the tank shell causes undesirable effects upon the performance ofthe floating deck. Specifically, as the sun follows is ecliptic path, various ortions of the tank shell are heated and then cooled; in the morning the east wall is heated and in the afternoon the west Wall is heated. As a portion of the tank Wall is heated, the vapor trapped in the clearance space is inherently also heated and expanded. As the vapors expand, they exert pressure on the sealing ring and pass through the outer edge of the ring to the space above the deck, thus at least in part defeating the purpose of the deck. Additionally, the vapor which does not escape through the peripheral seal convects in the clearance space, thus warming other portions of the clearance space not directly heated by the suns rays. Similarly, the heated vapor in the clearance space in turn heats the liquid immediately below, which is also heated directly by the sun on the hot side of the tank, thus further increasing the evaporation therefrom.

It has been found that the disadvantages noted above may be minimized by allowing the heated vapors in the clearance space to travel to areas directly beneath the deck, where they are reduced in temperature by the relatively cool liquid below the deck. This expedient reduces the volume of vapor that will escape the flexible seal and avoids warming other areas of the clearance space. Additionally, the liquid in the clearance space, heated by the vapor above it, is also allowed to flow into the area directly beneath the deck and be cooled by mixing with the cooler liquid in the area below the deck. It has been found that such controlled flow of the vapor and liquid in the clearance space may be obtained by providing in the vertical web about the periphery of the deck a number of slots allowing for'passage of the heated vapor. While such slots reduce in part the effectiveness of the vertical web, the reduction of the disadvantages noted above has been found to completely outweigh any such reduction in the effectiveness of the vertical Web.

Accordingly, it is a principal object of the instant invention to provide a new and improved floating deck for use within a liquid storage tank.

Another object of this invention is to provide such a deck which is simple in construction and easy to install.

A still further object of this invention is to provide such a deck which will allow for the passage of vapors and liquids trapped below the peripheral seal thereof to areas below the deck itself.

A still further object of this invention is to provide such a seal comprising a peripheral edge spaced inwardly from the tank shell and including a vertical web extending downwardly into the liquid stored, a flexible sealing ring secured to said peripheral edge and extending outwardly toward the tank shell, and at least one slot in said vertical web extending upwardly above the surface of the liquid stored.

Other objects and advantages will become apparent to those skilled in the art as a detailed description of a particular embodiment proceeds with reference to the drawings which form a part hereof, and in which:

FIG. 1 is a perspective view of a storage tank employing a floating deck according to the instant invention, with a portion of the tank wall broken away to show the interior thereof; and

FIG. 2 is a fragmentary cross-sectional view of a portion of the periphery of the instant floating deck, showing its relationship with the tank shell.

Referring now to FIG. 1 of the drawings, there is illustrated a storage tank 10 containing a stored liquid 11. While the tank is shown as being cylindrical and of an open top construction, it is to be understood that the instant invention is equally applicable to a tank of any desired cross-sectional configuration, and that the deck may be used in either an open tank or a closed tank. Supported on the surface of the liquid 11 is a floating deck 12, for example of the construction shown in the aforementioned U.S. Pat. 3,104,775. The floating deck 12 includes floats A, which are attached to the underside of the deck, a peripheral sealing ring 13 in contact with the wall of tank 10, and a peripheral edge which includes at least one slot 14 in accordance with this invention. Sealing ring 13 may be of any desired construction, for example that shown at 41 in the aforementioned US. Pat. 3,104,775, oras illustrated in the drawings-of a two-piece annular ring construction appropriately connected to an outwardly directed flange 23 of the peripheral edge of deck 12.

As exemplary of the effects of the sun upon the stored liquid, discussed above, there is shown by the arrows 15 the direction of motion of the vapors formed by the solar heating of the stored liquid and of the heated liquid itself, due to convective effect. Assuming, for example, that the suns rays are directed at the side of the tank to the right in FIG. 1, the hot vapors formed in the stored liquid rise with the convectional currents in the direction of the arrows 15. For the reasons discussed in more detail below, the vapors first approach the area of the peripheral seal 13, then flow through slots 14 to the area directly beneath the deck 12, where they may be cooled.

This action may be seen with greater clarity from the detailed view of FIG. 2. As there shown, the peripheral edge of floating deck 12 includes a vertical web member which extends downwardly into the surface of the liquid stored, for the reasons indicated hereinbefore. A clearance space 21 is thus formed between the vertical web member 20, the shell 22 of tank 10, the sealing ring 13, and the surface S of the stored liquid 11. As an indication of the relative size of clearance space 21, an exemplary deck 12 would float with its surface about one inch above the surface of the liquid stored, the peripheral edge of the deck 12 would end about five to ten inches from the tank wall, depending upon the clearance needed. With the construction shown in FIG. 2, the peripheral sealing ring 13 would be spaced several inches above the deck 12. Thus, it can be seen that the annular area of clearance space 21 is substantial, and the action of the vapor in such a space has a material effect upon the performance of the deck 12.

As indicated herein'before, the effect of the suns rays is to heat the vapor formed in the space 21, causing it to escape through sealing ring 13 or to conduct about the clearance space 21. Instead, by the provision of the slots 14, the vapors formed in clearance space 21 are free to travel through the slots 14 into the area directly beneath the deck 12, where they may be cooled by contact with the cooler liquid in such areas. As illustrated, each of the slots 14 extends from the lower edge of vertical Web member 20-which extends downwardly into the liquid, for example, 1 to 1%, inches-vertically upwardly to a point just under the surface of the deck 12. As the surface of deck 12 is above the surface of the liquid stored, the slot 14 will leave a passage, for example 2 inches wide, above the surface of the liquid stored.

The number and location of the slots may readily be calculated for a given tank and its intended position with regard to the solar heating expected. For most installations, a first plurality of slots will be required at a first portion of the vertical webcorresponding to the morning sun rays-and a second plurality will be required at a second portion of the web spaced a substantial distance from the first portion and corresponding to the late afternoon sun rays. In this manner, the portions of the clearance space most heated may be relieved from the undesirable effects noted.

It is to be understood that the invention is not limited to the illustrations described and shown herein which are deemed to be merely illustrative of the best modes of carrying out the invention, and which are susceptible of modifications of form, size, arrangement of parts and detail of operation, but rather is intended to encompass all such modifications which are within the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. In combination;

(A) a liquid storage tank having a vertically extending tank shell,

(B) a liquid stored within said storage tank,

(C) a deck disposed within said storage tank and floating upon the surface of said liquid to form a first vapor space between said deck and said liquid, said deck comprising;

(1) a peripheral edge spaced inwardly from said tank shell and including a vertical web extending downwardly and into the liquid stored,

(2) a flexible sealing ring secured to said peripheral edge above said liquid and extending outwardly toward said tank shell,

(3) at least one slot in said vertical web immersed in said liquid with a portion thereof extending upwardly above the surface of the liquid stored,

(4) a second vapor space defined by said peripheral edge, said tank shell, said sealing ring, and the surface of said liquid,

(5) fioat means to cause said deck to float with said portion of said slot extending upwardly above said surface of said liquid stored,

whereby, in use, vapor in said second space is free to leave said second space through said slot into said first space.

2. A combination according to claim 1, wherein at least two of said slots are provided at circumferentially spaced portions of said vertical Web.

3. A combination according to claim 1, wherein a plurality of said slots are provided at circumferentially spaced portions of said vertical web.

4. A combination according to claim 1, wherein a first plurality of said slots is provided at a first portion of said vertical web, and a second plurality of said slots is provided at a second portion of said vertical web circumferentially spaced a substantial distance from said first portion.

References Cited UNITED STATES PATENTS 1,404,924 1/ 1922 Bloss. 1,628,246 5/ 1927 Iddings. 1,698,158 1/1929 Glass. 2,735,573 2/1956 Fino. 2,973,113 2/1961 Fino.

JOSEPH R. LECLAIR, Primary Examiner I. R. GARRETT, Assistant Examiner