US3116850A

US3116850A - Tube seal for floating roof storage tank

Info

Publication number: US3116850A
Application number: US186926A
Authority: US
Inventors: Sr Lloyd E Anderson; Buckwalter Milton Thomas
Original assignee: Pittsburgh Des Moines Steel Co
Current assignee: Pittsburgh Des Moines Steel Co
Priority date: 1962-04-12
Filing date: 1962-04-12
Publication date: 1964-01-07
Anticipated expiration: 1981-01-07

Description

Jan. 7, 1954 L. E. ANDERSON ETAL 3,116,850

TUBE SEAL FOR FLOATING ROOF STORAGE TANK Filed April 12, 1962 '2 Sheets-Sheet 1 l v I f 5 r42 4 f 4 f v) 7 3 4 1 4 f /0 /9 2/ E v f l 5 i 7 5 at? 22 h l j 26 27 2 y k 12g. 4 L my 5 mwa v g Y W i #04 7 'r/lams suck M275? BY I M, m%. l2: 5- 1 I Arron/vans.

7, 1964 L. E. ANDERSON ETAL 3,116,850

TUBE SEAL FOR FLOATING ROQF STORAGE TANK Filed April 12, 1962 2 Sheets-Sheet 2 INVENTORS 440m 5. AIVOERSfl/V, SR. g /L ra/v mums aw/mm r52 ATTORNEVS.

United States Patent 6,3 TUBE SEAL FOR FLGATlNG ROUF STORAGE TANK Lloyd E. Anderson, Sin, Pittsburgh, and Milton Thomas Buckwaiter, Allison Park, Pat, assignors to Pittsburgh- Des Moines Steel Company, a corporation of Pennsyl- Van a- 1 Filed Apr. 1-2, 1962, Ser. No. 186,926

7 Claims. (Cl. 22tl26) This invention relates to means for sealing the annular space between roof and tank shell in afloating roof storage tank of the type used, for example, to store volatile petroleum products, thereby to prevent the evaporation and escape of volatile constituents from the tank.

-It is among the objects of this invention to provide an improved seal, of the type referred to, that will accommodate large variations in tank diameter due to out-ofroundness of the tank shell; that will also accommodate maximum horizontal movement of the floating roof within the tank shell; and that can be installed, and removed for maintenance, from the upper deck of the floating roof.

The foregoing and other objects will be apparent from the following description of the invention, in connection with the attached drawings, in which:

FIG. 1 is afragmentary elevation, partly in section, of a portion of a fluid storage tank of the floating roof type, showing the tube seal of this invention for sealing the annular space between the tank shell and floating roof;

FIG. 2 showsthe cross section profile of the same tube seal when deformed by compression into a narrower an nular space;

FIG. 3 is a view of the underside of the seal of FIG. 1, showing the arrangement of hanger rods and ring bars; and

(FIG. 4 is a cross section profile of a'modified form of seal.

In aocordancewiththe present'invention, the seal is an annular flexible'ttubetfilled'with'liquid and adapted to rest on the surface "of the stored liquid in the tank, in the annular space betweenthe float-ing roof and tank shell. The tube seal 'issuppened "from the roof by a number of circumferentially spaced hanger rods, which are pivotally'connected at one end to the roof and which have their other end passing through the top and bottom of the tube and connected to horizontal ring bars. These bars underly and support the tube between hanger rods and normally divide the lower portion of the tube into two concentric lobes, depending on either side of the bars. By their ability to separate and draw together, these lobes give the tube seal added capacity to accommodate variations in the annular space about the floating roof.

Referring to FIGS. 1-3, a cylindrical tank shell 1 is partially filled with a liquid 2, such as gasolene, on which floats a conventional floating roof 3. Liquid displaced by the floating roof rises into the annular space 4 between the roof and tank shell. The sealing member is made of treated fabric, such as nylon reinforced Buna-N fabric, which is formed either into a continuous tube of generally toroidal shape that extend-s completely around the tank between roof and shell, or into a series of tubular segments that are joined together to make a continuous tube. The tube is supported from the tank roof by a plurality of hanger rods 11, which are preferably spaced 3.14 feet apart along the length of the tube. The upper end of each rod is provided with a laterally extending car 12, which passes through a vertical slot 13 on the upper rim 14 of the roof and is pivotally secured to a bracket 16 by a pin 17 and cotter pin 18. The lower end of each hanger bar passes through the top and bottom portions FIG, 3.

of tube 10, at or near the midline of those portions. In the embodiment shown in FIG. 1, the rod passes through rubber nozzles 19, which are vulcanized to the central top and bottom portions of tube 10 and secured therein ;by hose clamps 2-1. Tube 10 is held on the hanger rods by threaded nuts 22, which also supporthorizontally extending ring bars 23. The latter underlie and support the central bottom portion of tube 10 adjacent each pair of hanger bars, as shown in FIG. 3. The ends of adjacent bars are spacedapart sufficiently to allow for some radial movement of the ring bars. The bars are preferably curved (in plan view) to the approximate curvature of the midsection of the annular space 4, as shown in "It may also be desirable to curve the bars slightly in section and to round their upper edges, so as to fit the adjacent, arcuate bottom of the sealing tube.

By the arrangement described, tube 10 may be filled with a liquid 24, preferably a little heavier than the stored liquid 2, and be adequately supported from the roof of the tank. 7 7

Since the floating roof may occasionally be displaced to one side of the tank by external forces and since the diameter of the tank may vary due to out-of-roundness fabric will hang down in two lobes Zoand 27 on either side of ring bars 23. In other Words, the hanger rods and ring bars divide the lower portion of the tube into these two concentric lobes. When the annular space 4 varies in width, as when either the shell is out of round or the roof is displaced from its normally concentric position within the shell, then the lobes will become more pronounced and come together below the ends of the hanger rods 11 on that side of the tank where they are compressed as shown in MG. 2; and at the same time, due to hydrostatic pressure, the lobes will separate and flatten out into a more nearly circular (or rectangular) cross section profile onthe other side of the tank. 7 These changes in the tube profile will be accompanied by a transfer of fluid inside the tube, corresponding to changes in area of the tubes cross sections. It will be noted from FIG. 2 that the tube maybe compressed on one side to the width or" ring bar 23before any rigid structure limits the compression. Likewise, the tube may expand laterally to the extent permitted by its own size and shape without limitation from any rigid structure. The cross section profile of the tube at any spot will be determined by the relation between (I) the length of the perimeter of the cross section and the distance separating the top and bottom portions of the tube along the hanger rods 11 and (2) the width of the annular space 4 at that spot.

The sealing member shown in FIG. 4 is a tube 30 similar to that of FIG. 1, except that the central top and bottom portions of the tube in FIG. 4 are clamped tightly together at each hanger rod 31 (instead of being vertically spaced apart, as in FIG. 1) between ring bar 23 beneath the tube and clamping nuts 32 on a threaded portion of the hanger rod. This construction partitions the tube radially into two nearly separate concentric lobes 33 and 34. However, the two lobes are not sealed from each other between hanger rods, so that fluid may be transferred from one lobe to the other under various operating conditions. In the embodiment of 'FIG. 4, the hanger rods preferably project well below ring bars 23; and on the lower ends of those rods are mounted washers 36 and nuts 37 for clamping the lower edge of a continuous scuff band 38, provided with eyelets 39 through which the hanger rod passes. The scuff band extends around the outer lobe 33 of the sealing tube in contact with the tank shell and has its upper edge, also provided with eyelets, similarly clamped. The scuff band tends to limit the vertical displacement of the outer lobe 33, acting as a hold-down when the roof is moving downwards. in the absence of a scuff band, the same hold-down function can be obtained from a series of straps, attached to the hanger rods in the same way as the scuff band. Again, if the scuff band is made of a ribbed fabric with the ribbing 41 etxending horizontally, it will tend to reduce the capillary flow of stored liquid along the tank shell wall. The scuff band, being more resistant to wear than the fabric of the tube, may be used to advantage (with the seal of FIG. 1, as well as that of FIG. 4) in storage tanks having relatively rough inner tank shell surfaces, such as gunnited tanks, that are likely to abrade the more delicate fabric of the sealing tube itself. The scuff band is needed, if at all, only around the outer lobe of the tube, because that lobe alone slides relative to an adjacent surface (the tank shell). The seal moves with the roof, so that there is no relative sliding movement between the inner lobe and the roof wall.

The seal shown in FIG. 4 acts essentially in the same way, under similar conditions, as that of FIG. 1, already described. Each seal is characterized by its capacity to accommodate large variations in the width of the annular space between the roof and tank shell, produced either by lateral shifting of the roof or by out-of-roundness of the shell, without reducing the effectiveness of the seal. Further, the means for supporting the seal from the rim of the roof permits the seal to be installed, or removed for inspection or repair, from the roof deck 42. It will be understood, of course, that the hanger rods, which also act as holddowns for the tube seal, will have a length determined by the height of liquid 2 in the annular space 4, this height being a function of the displacement of the tank roof.

According to the provisions of the patent statutes, we have explained the principles of my invention and have illustrated and described what we now conisder to repre sent its best embodiment. However, we desire to have it understood that, Within thescope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

We claim:

1. In a floating roof storage tank, a seal for sealing the annular space between the roof and tank shell, comprising a flexible tube disposed in the annular space, tube suporting means that include circumferentially spaced hanger rods each having one end pivotally connected to the roof and having the other end passing through top and bottom portions of the tube and connected to a horizontal ring bar underlying and supporting the tube between adjacent hanger rods, the ring bar dividing the bottom portion of the tube into two normally depending lobes, said tube supporting means extending from the Wall of the roof into the annular space a radial distance less than the minimum lateral thickness of the tube when fully compressed laterally, thereby to permit maximum lateral displacement of the roof relative to the shell by limiting such displacement solely by compression of the tube, and liquid within the tube to maintain its sides in sealing contact with the roof and shell.

2. Apparatus in accordance with claim 1, in which the top and bottom portions of the tube are clamped together at each hanger rod.

3. Apparatus according to claim 1, in which the top and bottom portions of the tube are spaced apart vertically at each hanger rod.

4. Apparatus according to claim 1 that also includes means for vertically spacing the top portion of the tube from the bottom portion at each hanger rod and means for preventing intermixing of liquid stored in the tank and liquid contained in the tube.

5. Apparatus according to claim 1 in which the hanger rods act as a hold-down for the tube as a whole and in which additional hold-down means are provided for the outer lobe and adjacent outer portions of the tube.

6. Apparatus according to claim 5, in which the additional hold-down means comprise a scuff band having an edge secured to the hanger rods above the tubular seal and having the other edge secured below the horizontal ring bar, the scuff band overlying the radially outermost lobe and an adjacent upper part of the tubular seal.

7. Apparatus according to claim 1, in which each hanger rod is connected to the roof by a laterally extending ear connected to the upper end of the rod, the roof having an opening for receiving the free end of the ear, and pin means inside the roof pivotally connecting the free end of the ear to the roof.

References Cited in the file of this patent UNITED STATES PATENTS 2,066,292 Kuehn Dec. 29, 1936 2,072,798 Cranz Mar. 2, 1937 3,002,828 Fino et al. Oct. 3, 1961 3,059,806 Joor Oct. 23, 1962 3,075,668 Reese Jan. 29, 1963 FOREIGN PATENTS 226,959 Australia Apr. 17, 1958 95,382 Netherlands Sept. 15, 1960

Claims

1. IN A FLOATING ROOF STORAGE TANK, A SEAL FOR SEALING THE ANNULAR SPACE BETWEEN THE ROOF AND TANK SHELL, COMPRISING A FLEXIBLE TUBE DISPOSED IN THE ANNULAR SPACE, TUBE SUPORTING MEANS THAT INCLUDE CIRCUMFENTIALLY SPACED HANGER RODS EACH HAVING ONE END PIVOTALLY CONNECTED TO THE ROOF AND HAVING THE OTHER END PASSING THROUGH TOP AND BOTTOM PORTIONS OF THE TUBE AND CONNECTED TO A HORIZONTAL RING BAR UNDERLYING AND SUPPORTING THE TUBE BETWEEN ADJACENT HANGER RODS, THE RING BAR DIVIDING THE BOTTOM PORTION OF THE TUBE INTO TWO NORMALLY DEPENDING