US2766707A - Roofs for storage tanks or similar structures - Google Patents

Description

Oct. 16. 1956 R. H. FOSTER ET AL ROOFS FOR STORAGE TANKS OR SIMILAR STRUCTURES 3 Sheets-Sheet 1 Filed Feb. 19, 1953 m N 6 a w m N Q Oh mm Oh 9N R r. wN +0 \M N m w\ g m m m n A.. 0. o. J a Q .ofu v m m mkQ N\ EL FQ 5 3 m P HM Z a Ow NM bM 5mg QM m 0 a 1 v Oct. 16, 1956 R. H. FOSTER ET AL 2,766,707

ROOFS FOR STORAGE TANKS OR SIMILAR STRUCTURES Filed Feb. 19, 1953 3 Sheets-Sheet 2 l I ww ww \& om r vm/ \m hwl/ Q 1 all. 1; |||l Oct. 16, 1956 R. H. FOSTER ET AL 2,766,707

ROOFS FOR STORAGE TANKS OR SIMILAR STRUCTURES Filed Feb. 19, 1953 a Sheets-Sheet 3 lnvemor; Ro er-Z -/7 Fost 172277768 McLean United States Patent ROOFS FOR STORAGE TANKS 0R SIMILAR STRUCTURES Robert H. Foster, London, England, and James McLean, Mother-well, Scotland Application February 19, 1953, Serial No. 337,845!

1 Claim. (Cl. 108-32) This invention relates to the roofs of tanks for the storage of liquids, or of other similar structures. The invention provides a form of roof construction particularly suitable for application to structures having a diameter of about 50 feet or less, which permits considerable economies in the amount of steel and workmanship employed, as compared with previously known forms of roof.

The invention includes broadly a conical roof for a circular structure such as a liquid storage tank, which comprises a peripheral curb, a plurality of radially disposed sheet metal panels, together constituting the conical roof surface, which abut at their outer ends against the curb, and a centrally disposed crown member to which all the panels are secured at their inner ends, the panels, some at least of which are provided with stiffening flanges, being otherwise unsupported so that they act as half arches with continuity through the crown member.

Other features of the invention will sufliciently appear from the appended claims, when read in the light of the following description of the particular form of roof constructed in accordance with the invention, and of some of the many possible modifications of this construction, which are illustrated in the accompanying drawings. In these drawings:

Figure 1 is a plan view of part of the completed structure;

Figures 2 and 3 are fragmentary plan views showing parts of the structure on a larger scale;

Figures 4 and 5 are fragmentary vertical radial sections through the structure, taken respectively on the lines IV-IV and V-V of Figures 1, 2 and 3;

Figure 6 is a circumferential section taken on the line VI-VI of Figure 1, and

Figures 7, 8 and 9 are views, corresponding to 6, of modified constructions.

The roof illustrated in Figures 1 to 6 is intended for use upon an oil storage tank having a vertical cylindrical side wall, 35 feet in diameter. The roof is of conical shape, having a slope of 1 unit vertically in 6 units horizontally. It comprises 30 radially disposed panels formed from A thick plate, which extend from the top of the side wall 10 of the tank to a central crown member 11. One of these panels 12, which is the first to be placed in position, is flanged along both of its radial edges; the 28 similar panels 13, which are positioned next, are flanged along one radial edge only and the final closing panel 14 is unflanged. In each case, the flange comprises a downwardly projecting portion 15, which is 3 inches deep, and a horizontal inturned portion or return flange 16 which is 2 inches wide. At the junction between each pair of adjacent panels, an unflanged edge of one panel overlaps a flanged edge on the other panel by 1 /2 inches, the unflanged edge being secured by a continuous weld to the upper surface of the adjacent underlying panel. Each panel acts as a half arch, sup- Figure "ice ported at its outer end and continuous through the centre ring with the diametrically opposite half arch.

At the upper edge of the side wall 10 of the tank is a curb 17 formed from curved angle sections, measuring 3 /2 inches by 2 /2 inches by inch, site welded into a continuous ring. As best seen from Figure 4, the curb angle is secured with its shorter limb against the outer surface of the side wall 10 and with its longer limb extending horizontally outwards from the upper edge of the wall, by continuous fillet welds at the top of the side sheeting and at the lower edge of the vertical limb of the curb. The outer end of each flange of the roof panels is cut away so that when the end surface of the flange is against the side Wall the top por-. tion of the panel overlaps the curb angle. The outer end of the return flange 16 rests on a bracket formed by a bent plate cleat 18, site welded to the vertical side Wall 10, which takes the vertical reaction from the flanged part and distributes it gradually down the shell plating. A bolt 19 passes through registering holes in the return flange 16 and cleat 18.

At the inner end of each flange of the roof panels (see particularly Figure 5) a 3 inch square by Mt inch thick pad plate 20 is welded on to the end surface of the flanged portion, the vertical flange 15 and return flange 16 being cut away so that the outer surface or" plate 20 is vertical and flush with the end of the top portion of the panel. The central crown member 11 is in the form of a ring fabricated from steel plates and has an outside diameter of 3 feet, an internal diameter of 1 foot 10 inches and a depth of 4 inches. It is composed of two annular plates 21, 22 connected together by two vertical cylindrical plates 23, 24, the connection between the plates being made by welding. The inner ends of the flanged panels abut against the outer face of the crown ring and, for temporary erection purposes, are attached to it by means of bolts 25, passing through appropriately positioned holes in the pad plates 20 and in the cylindrical plates 23, 24 of the crown ring. The permanent connection between the panels and the crown ring is obtained by welding the pad plates to the crown ring. A circular top closure plate 26 of about 3 feet 6 inches diameter overlies the crown ring. The marginal portion of this plate, which projects beyond the crown'ring, is flanged downwardly and attached to the roof panels by fillet welding along its periphery.

In assembling the roof structure, the curb angles 17 and cleats 18 are welded to the side sheeting and a temporary support is erected to carry the central crown ring. First, the double flanged panel 12 is lifted into position and held by the bolts 19 at its outer end and by the bolts 25 at its innerend. The 28 single flanged panels 13 are then lifted in turn, placed with the unflanged edge on top of the flanged part of the adjacent plate and held 7 in position by their bolts 19 and 25. After all the flanged panels are in position, their unflanged edges are continuous welded to the upper surface of the adjacent underlying panels and, for a distance of some six inches inwardly from the side wall, the flanged edges of the panels are Welded to the under surfaces of the adjacent overlying panels. The outer peripheral edges of the panels are continuous Welded to the curb angle 17 and the pad plates 20 are welded to the outer face of the crown ring.

The temporary centre support has been retained. during all of the preceding assembly and the load on it has been gradually increased. The panels have been acting as simply supported beams with vertical reactions at their outer ends to the cleats and vertical reactions at their inner ends to the central crown ring. When the aforementioned welding has been completed, the temporary support is removed through the still unclosed gap in the roof; Each panel then acts as a halt arch with continuity through the crown ring. The curb angle and adjacent portions of the roof sheets and side sheets supply the abutments of the arch and under the dead load of the roof are put into a state of bending and direct tension.

To complete the assembly of the roof, the unflanged closure plate 14 is placed in position and continuous fillet welded to the adjacent underlying flanged plates and 13. The circular top closure plate 26 is placed in position and continuous welded at its outer peripheral edge to the underlying panels, a packing plate 27 being inserted above the double flanged panel 12 to make up the difference in level between it and the adjacent panels. The outer peripheral edges of the panels are continuous welded to the curb angle 17.

In an alternative construction, which may be employed where additional strength is required, or Where corrosive liquids are to be stored, or where other conditions merit it, every second panel is constructed of thicker material and flanged along both radial edges while the intervening panels are left unflanged, all the panels being thus similar to the panels 12 and 14 of Figures 1 to 6. Figure 7 shows a section (corresponding to Figure 6) through a roof for a 35 foot diameter tank constructed in this alternative manner. The roof is composed of only 18 panels, thenine panels 28 being constructed from A inch plate and formed at both radial edges with downwardly extending flanges 29 and inwardly extending return flanges 30, precisely similar to the flanges 15, 16 already described, while the nine panels 31 are of 7 inch plate and are unflan'ged. A packing plate (similar to plate 27 of Figure 3) is in this case inserted between each of the panels 28 and the circular closure plate 26 applied over the crown ring. The construction and manner of erection of this roof is in other respects as already described with reference to Figures 1 to 6.

In order to reduce the amount of shop workmanship required and to reduce the bulk of the roof for shipping purposes, the flanges and return flanges 15, 16 and 29, 30 may be replaced by plain flanges and Figures 8 and 9 show constructions embodying this modification. In Figure 8, as in Figures 1 to 6, one of the panels 32 is provided with flanges 33 at both radial edges and an adjacent panel 34 is without flanges, all the remaining panels 35 having a flange 33 at one radial edge only. In Figure 9, as in Figure 7, panels 36, provided with flanges 37 at both radial edges, alternate with panels 38 which are unflanged. The flanges 33 and 37 have a depth considerably greater than the depth of the flanges and 29.

For the smaller diameters of roof, such plain flanges alone afford sufficient stiffening'to thereof panels, but for larger diameters and pressures additional strength and stiffening may be required. In such cases, as an alternative to the use of return flanges (such as 16, stiffening plates extending transversely to the panels may be secured between the inner surface of the flanges and the undersurface ofthe top portions of the panels. Figure 8 shows a single substantially triangular stiffening plate 39 of this kind, continuous fillet welded on both sides to the flange 33 of one of the panels and to the top portion of that panel. In practice a number of such plates would be provided at suitable intervals along the length of all or some of the flanged panels. Figure 9 shows a single substantially rectangular stiffening plate 40 secured at its ends by continuous fillet welds on both sides to both flanges of one of the panels 36 and at its upper edge by intermittent fillet welds on both sides to the top part of that panel. Again a number of such plates would in practice be provided at intervals along the length of all or some of the flanged panels. In the construction of Figure 9, triangular stiffening plates, such as 39, could be used either in place of or in addition to the plates 40.

It will be understood that the constructions described are intended by way of example only and that the invention is not limited to the dimensions given nor to the details of construction described, many modifications besides those spccifically mentioned being possible within the scope of the appended claims. Thus, for example, the roof may be constructed wholly or partly of aluminium alloy, or other suitable metal, instead of steel.

We claim:

In a tank having a vertical cylindrical wall and a conical roof, a roof structure comprising a peripheral curb forming a continuous aiigle section ring having a vertical limb secured to the vertical wall and a horizontal limb projecting outwardly from the wall, a plurality of radially disposed sheet metal panels together constituting the conical roof surface, the outer ends of said panels extending outwardly over the upper edge of said wall and being secured to said curb, a downwardly extending stiflening flange formed integrally upon the radial edge of at least one of said panels at each of the junctions between pairs of adjacent panels to constitute said panel as a girder,- the edge of the second panel of said pair being unflanged and projecting over the flanged edge of said first panel, oneof said panels having integral stifiening flanges upon both radial edges while another of said panels is flat and without any flanges, said stiffening flange extending to the inner end of said panel but terminating inwardly of said tank wall, a bracket'proje'cting' inwardly from said wall and supporting each of said stiflening flanges, an annular crown member having a depth substantially equal to that of said stiffening flanges to which all the panels are secured at their inner ends with their surfaces substantially level with the upper surface of said crown member, said stittening flanges are being secured over their entire depth to the crown member and abutting over their whole depth against the wall of the tank so that said crown member is being supported solely by said flanged panels, said crown member comprising'two spaced-apart concentric cylindrical members and flat rings joining said concentric members .at their upper and lower edges respectively, and a circular closure plate covering said crown member and extending outwardly over and secured to each of said panels, the panels being unsupported otherwise than at their endsso that they act as half arches with continuity through said crown member; the junctions between the panels themselves and between the panels and the curb and the cen: tral closure plate are all made by continuous lines of welding which constitute a seal as well as a connection.

References Cited in the file of this patent UNITED STATES PATENTS 577,097 Abrahams Feb. 16, 1897 1,844,961 Kramer Feb. .16, 1932 1,852,659 Kramer Apr. 5, 1932 1,907,268 Schwemlein May 2, 1933 1,983,476 Lincoln Dec. 4, 1934 FOREIGN PATENTS 7

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