US2492963A - Sealing means for liquid storage tanks - Google Patents

Description

Patented Jan. 3, 1 950 UNITED S'l'A TE-S" PATENT OFFICE SEALING MEANS STORAGE Frederick Bernard Boos, Montreal, Quebec, Canada, assignor'to Chicago Bridge 8: Iron Company, a corporation of Illinois Application October 11, 1946, Serial No. 702,784

6 Claims.

1 This invention relates to sealing means and, more particularly, to a sealing means for use in conjunction with a liquid storage tank.

This application is a continuation-in-part of my copending application, fined November 26, 1945, as Serial No. 630,733, now abandoned.

In liquid storage tanks for the storage of volatile liquids, means must of necessity be provided for permitting expansion and contraction of volatilized gases within the tank. A common construction is a lifter roof tank in which the roof is adapted to rise and fall to provide a variable volumetric vapor capacity for the tank. In such installations it is necessary to provide a seal between the roof and the tank to prevent the escape of gases and the consequent loss of liquid. Two.types of seals have generally been employed, namely a liquid seal in which a depending skirt of the roof is immersed in an annular liquid trough about the tank, and a flexible fabric seal between the roof and the tank. It has been found that the fabric seal, while the most eflicient, is often the most ex pensive to install and maintain, mainly because of the initial cost of the. impregnated fabric and because of the need of replacement due to the corrosion of the seal by the gases.

I have found that a flexible seal composed of thin sheets of metal may be employed advantageously in place of the fabric seal, and pos- No. 630,733. The invention is illustrated in the accompanying drawings in which Fig. 1 is a side elevation partly broken away for clarity of illustration of a lifter roof tank. Fig. 2 is a top elevation partly broken away of the tank of Fig. 1. Fig. 3 is a vertical section along lines 3-3 of Fig. 1. Fig. 4 is a vertical section along lines 4-4 of Fig. 1. Fig. 5 is a detailed sectional view along lines 55 of Fig. 3. Fig. 6 is a detailed sectional view along lines 6-6 of Fig. 4, and Fig. '7 is a horizontal section along lines '|'l of Fig. 3.

The lifter roof tank shown in the accompanying drawings comprises a shell ill, a roof H, and 4 a novel, flexible, metallic sealing member |2 (which will hereinafter be more fully described) within the .tank is increased and decreased. In order to maintain the roof substantially level at all times, levelling means are provided. The levelling means comprises a plurality of spaced, sloped bar members It all sloped in the same direction at substantially to the horizontal. Around the outside of the tank and adjacent the bar members It there is located a ring i5. On the ring there are positioned rollers l6 held in brackets I! with each pair of rollers contacting the bar member it on opposite sides thereof. Around the edge of the roof and attached to the depending skirt l3 there are provided a plurality of spaced depending members it! located adjacent the ring I5. On each of these depending members there are provided a pair of rollers l9 mounted on brackets 20 with each pair of rollers contacting the bar I!) on opposite sides thereof. With this construction the rollers IS on the ring i5 ride up and down on the sloped bar members M as the roof rises and falls. This causes the ring I5 to turn, and because of the rollers IS on the depending members I8 the ring also turns relative to said depending members. The levelling means serves to maintain the roof level at all times.

In order that the roof itself will move vertically only, it is preferred that guide means be provided on the shell Ill and the roof Any suitable guide means may be provided. That shown includes a vertical guide bar 2| attached to the outside top edge of the shell and a pair of rollers 22 held in brackets 23 attached to the depending skirt I3. The rollers 22 contact the guide bar 2| on either side. As the roof moves the uide bar 2| and rollers 22 limit the move-. ment to vertical travel only.

In order that the top portion of the roof l2 will not rest on the top edge of the shell l0 when the roof is in its lowest position, there is provided an annular bracket 29 of angle iron or the like, attached to the inner surface of the shell In near the top thereof. There is also provided an annular depending member 30 attached to the under side of the roof l2 for resting on the bracket 29 when the roof is in its lowest position. The annular member 3|! serves not only to support the roof in its lowest position, but also reinforces the roof. If desired the depending member 30 may be located over the top edge of the shell Ill so as to eliminate the necessityv for the annular bracket 29.

The sloped bar members I and the vertical guide bar 2| are preferably in the form of rails.

as many maybe provided as desired. 7 p The sealing member, generally designated I2, comprises a plurality of rectangular sheets of metal Ila, preferably aluminum, attached at their upper edges along a straight line to brackets 3| secured about the periphery of the shell It. The lower portion of each sheet is attached to brackets 32 secured about the periphery of the depending skirt i3, and the attachment is also along a straight line. It is necessary that the metal sheets comprising the sealing member be attached in the manner indicated to prevent buckling oi the metal as the root rises and falls. The attachment in the manner shown to the brackets 3i and 32, which are in the shape of a polygon about the shell and roof, provides for the attachment oi the sheets along straight lines and permits vertical movement of the roof, while limiting the flexing of the sheets to a single curve. Each sheet is maintained in vapor-tight relationship to adjoining sheets by a flexible non-metallic seal 33, attached to the adjacent edges of adjoining sheets and to the brackets 3| and 32 in order that no vapor may escape therebetween. This non-metallic sealing member 33 may be of any familiar construction, although I prefer to use an impregnated fabric, such as neoprene.

Various thicknesses of the metallic seal may be employed, the thicknesses depending upon the radius of the curved portion 34 of the seal. For example, if aluminum sheets are used, I have found that No. 29 gauge, which is approximately .012 inch. thick, will flex to a radius of curvature of approximately 3 inches and work at that radius without any apparent distress of permanent deformation. This material has a minimum ultimate strength of 42,000 lbs. with a minimum yield strength of 35,000 lbs. Working on a 3 inch radius, the metal is being stressed in the neighborhood of 20,600 lbs. If the horizontal distance between the brackets 3i and 32 are inches or greater so that the radius of the curve 34 is correspondingly greater, thicker sheets of aluminum may be used. For example, I have found that a sheet having a thickness of approximately .022 inch will bend to a radius of approximately 5 inches without taking a permanent set.

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

I claim:

1. A liquid storage tank comprising a shell, a lifter roof over said shell adapted to rise and fall with increasing and decreasing gas pressure within the tank, sloped bar members attached to the shell near the top thereof and all having substantially the same slope with respect to the horizontal, a ring surrounding the shell, roller members attached to said ring and contacting said bar members on either side thereof, depending members extending down from said roof adjacent said ring, roller members attached to said depending members and contacting the ring on either side thereof, and a plurality of substantially rectangular thin metal sheets secured to the roof along one Although only one guide bar has been shown.

gether inrvapor-tight relationship by an impervious, flexible, non-metallic seal.

, 3. In a lifter roof tank having a shell and a litter roof thereover adapted to rise and tall with increasing and decreasing vapor pressure within 7 the tank, flexible sealing means between the roof and the shell adapted to flex with upward and downward movement of the roof comprising a plurality of thin metallic sheets attached to the roof and to the-shell along straight lines, said straight lines being in the form of substantially concentric parallel polygons about theperipheries of the roof and the shell.

1. The lifter roof tank of claim 3 in which said metallic sealing means comprises a plurality of thin metallic sheets attached to the roof and to the shell along straight lines about the peripheries thereof, said lines being in the form of concentric parallel polygonsand said sheets having their adjacent edges secured together in vaportight relationship by a flexible non-metallic seal.

5. In a lifter roof tank having a shell and a roof thereover adapted to rise and fall with increasing and decreasing vapor pressure within the tank, flexible sealing means comprising a plurality of flexible metallic sheets attached to the shell about the periphery thereof along substantially straight lines and attached to the roof about the periphery thereof along substantially straight lines, the vertical distance between the lines of attachment to said roof and said shell being suilicient to permit said sheets to flex with upward and downward movement of said roof, with said lines being in the form ,of concentric parallel polygons, and a flexible non-metallic seal attached to adjacent edges of said sheets.

6. In a liquid storage tank having relatively movable members adapted to move with respect to each other to provide a variable volumetric vapor capacity for the tank, a flexible metallic sealing means between said members comprising a plurality of thin metallic sheets, each sheet being generally rectangular in shape and secured at one edge to one of said members along a straight line and secured to another member on a straight line along the opposite edge, said lines of attachment defining generally parallel concentric poly. gons about the periphery of the tank, the adjacent edges of said sheets being secured together r in vapor-tight relationship by a flexible non-metallic seal.

- FREDERICK BERNARD BOOZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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