US2848799A - Method of erecting floating roofs - Google Patents

Description

6, 9 8 J. A. HANNA 2,848,799

METHOD OF ERECTING FLOATING ROOFS Filed Oct. 21, 1953 2 Sheets-Sheet 1 INVETO J Jamea QHarzzza,

s- 1958 J. A. HANNA 2,848,799

METHOD 01-" ERECTING FLOATING ROOFS Filed 001:. 21, 1953 v 2 Sheets-Sheet 2 INVENTOR. E5595 Zf/czmza,

BY I S. #M W United States Patent O METHOD OF ERECTING FLOATING RooFs James A. Hanna, Chicago, Ill., assignor to General American Transportation Corporation, Chicago, 111., a corporation of New York Application October 21, 1953, Serial No. 387,460

2 Claims. (Cl. 29-429) This invention relates to the erection of floating roofs in cylindrical storage tanks and has for its principal object the provision of a new and improved method of erecting such structures.

It is a main object of the invention to provide a method of erecting and installing a floating roof in a storage tank, which requires the use of a minimum of temporary structure.

Another object of the invention is to provide a method of erecting and installing a floating roof in a storage tank with a minimum expense.

Further objects of the invention not specifically mentioned here will be apparent from the detailed description and claims which follow, reference being had to the accompanying drawings in which the invention is diagrammatically illustrated in connection with one type of floating roof and in which:

Fig. 1 is a diagrammatic view showing the first step of the process;

Fig. 2 is a plan view showing the second step of the process;

Fig. 3 is an elevational view showing the next step of the process; I

Fig. 4 is a detailed view drawn to an enlarged scale and showing the arrangement employed in the step of the process illustrated in Fig. 3;

Fig. 5 is a detailed view drawn to an enlarged scale showing the arrangement of apparatus employed in the next step of the process; and

Fig. 6 is a diagrammatic view illustrating the structure at the completion of the process.

Storage tanks, such as are commonly used to store volatile liquids, frequently are in the form of a cylindrical tank, the axis of which is disposed vertically. Such tanks are oftentimes equipped with roofs which float upon the surface of the liquid stored in the tank, and rise and fall therein as the liquid level changes. Such roofs are provided in a number of forms including socalled high deck roofs in which the deck registers with the top of a continuous peripheral pontoon; low deck roofs in which the deck registers substantially with the bottom of a continuous peripheral pontoon; double deck roofs in which the decks register substantially with both the top and bottom of a continuous peripheral pontoon; and pan type roofs consisting of a deck and peripheral upwardly extending wall. Roofs for large diameter tanks are usually provided with a center pontoon in addition to the peripheral pontoon.

In the erection of such tanks it has heretofore been the procedure to lay the bottom of the tank complete and to erect the first layer of the side wall of the tank complete. Temporary structures are then placed upon the bottom comprising, in effect, a skeleton false bottom disposed above the bottom of the tank a distance corresponding to the normal minimum working height of the roof. The roof structure is then erected upon this false work. It will be understood that the deck and pontoons, if any, are both constructed of steel plates that are lapped and welded together. Construction of the roof elevated off of the bottom is necessary to permit installation of underdeck devices such as drains.

It is common practice in floating roofs of this type to provide as jntegral components of the roof, a plurality of sleeves through which are projected supporting pipes that engage the bottom of the tank and limit the downward movement of the roof at a point a few feet above the bottom. The supporting pipes ordinarily extend several feet above the roof, and when it is necessary to clean the tank or repair the same, these pipe supports are projected farther down while the roof is still floating upon the liquid, so that they will engage the bottom of the tank and support the roof thereabove a distance suflicient to permit the workmen to perform their duties in the space between the roof and the bottom of the tank after the tank has been drained.

Heretofore, as soon as the drains, sleeves, and supporting pipes have been inserted in the completed roof structure with the supports engaging the bottom of the tank, the false work has been removed. Since the roof structure must be complete or virtually complete before the false work can be removed, it is obvious that the task of removing this false work is hand work and therefore quite expensive, constituting a disproportionately large portion of the cost of installing the roof. Furthermore, since the entire roof, including the pontoons if any, must be supported in elevated position, a large quantity of false work material is required and the transportation of such material from job to job is therefore quite expensive.

The present method modifies the procedure that has been followed heretofore, in such a manner as to eliminate or minimize the use of false or temporary work and, where temporary Work is employed in reduced amount, to employ it in such position as to enable it to be handled into and out of the tank more economically than has been possible heretofore.

To this end the procedure of laying the bottom of the tank is followed as before. The roof structure is then erected directly upon the bottom of the tank. In case the roof is of the type having pontoons and a deck, both the pontoons and the deck are erected directly upon the bottom of the tank and the sleeves are installed and secured in place as by welding. In roofs such as the pan type roof, the deck and peripheral wall are erected upon the bottom of the tank and the sleeves installed therein.

Supporting pipes are inserted in the sleeves and the thus completed roof then hoisted into working position by hoisting means secured to the supporting pipes and to the roof. With the roof thus elevated, underdeck devices, such as drains, are then installed to complete the structure.

In the case of a so-called high deck roof, either one of two procedures may be followed within the teachings of the invention. In either case, the outer pontoon that extends completely around the periphery of the roof is erected directly upon the bottom and equipped with sleeves. In the case of large diameter tanks the center pontoon is also erected directly upon the bottom at the center of the tank. Either one of two procedures may then be followed in erecting the deck. In the one instance, the deck plates are installed directly on the bottom subsequently to be hoisted into registration with the pontoons by hoisting means attached to the supporting pipes that are placed in the sleeves. In the other procedure, a small amount of false work is placed upon the bottom of the tank and the plates laid thereupon and secured together and to the pontoons, the false work being moved around the deck as the work proceeds. In either case, the deck and pontoons are raised off of the the position shownin Fig. 3.

bottom of the tank by hoisting means connected between the supporting pipes and the roof structure. When the roof is' thus elevated, it is secured to the supporting pipes andunderdeck devices, such as drains, are next invSt lled. After the roof is secured to the supporting p'ipe's, any false work that has been employed can be removed easily sincethe side walls of thetank have not yet been erected and the false work can be moved laterally off of the bottom.

In the case of a low deck roof, the pontoons are installed asbefore and the deck plates placed either upon the bottom or upon false work that raises the outer ends of the plate to provide pitch to the roof for drainage purposes. Sleeves are installed and the roof hoisted to working height'as before, after which underdeck devices, such as drains, may be installed.

As will be seen in Fig. 1, in the first step of my improved process, the bottom 1', outer pontoon 3, central pontoon 4, if the tank is of largediameter and the roof is to be equipped with a central pontoon, and the deck 5, are erected with the pontoons and deck disposed upon the bottom 1 of the tank. This step of the operation includes inserting in the pontoons sleeves 6 and 7 which are usually located at the inner edge of the outer pontoonand outer edge of the inner pontoon and are suflicient in number to permit proper control of 'the roof in operation.

In Fig, 1 and throughout the drawings, the outer wall 2 of the tank is shown merely to illustrate its position relative to the roof as, in accordance with the teachings of this invention, the outer Wall of the tank is not erected until after the roof is completed. 1

As will be seen in Fig. 4, a pipe support is pro jected through each of the sleeves 6 and 7 and a hoisting mechanism' 11, preferably consisting of a chain hoist, is

connectedbetween the top of the supports 10 and brackets 1 2.attached to the deck 5 adjacent the outer edge there- Operation of the hoist 11' raises the deck into the position in which it is shown in Fig. 3.

Since the deck at this stage is unsupported at its outer edge, no temporary supporting structure having been used, it may be badly distorted by being raised'to To guard'against such a contingency, temporary brace members 15, preferably composed of scafiolding timbers, may be laid over the upper surface of the deck in-such a pattern as will best prevent distortion of it, which pattern may be varied within the teachings of the invention and will depend upon such factors as the diameter of the deck and height to which the outer edge is to be raised. The timbers 15 are secured to the deck by suitable brackets 16 welded to the deck plates.

In certain instances with very large decks, it may be advantageous to clamp one of the radial seams-in the deck plates instead of welding it, until after the deck has been hoisted to final position relative to the pontoons to permit a sliding movement of the plates during hoisting; however, I have found that ordinarily such procedure is not required if proper arrangements forstifiening the deck structure are employed.

With the deck 5 elevated in the manner shown in Fig. 3, with its outer periphery in registration with the upper .edge of the pontoon, the deck is secured to the pontoon secured to'the pontoons while on the bottom of the'tank,

" equipped with a sheave 20, and brackets 21 and 22 are fixed to the groove adjacent the sleeve 6. Bracket 21 carries a pulley 23 and a cable" 24 is attached to the bracket 22, extended .over the sheave 20 down the other side of the pipe 10' to the pulley 23 and thence to a hoisting device'such as a chain hoist, of sufiicient capacity to enable the roof to be raised.

When each of the pipes 10 has been so equipped, the hoisting devices are operated to raise the roof to a desired heightotf of the-bottom, and the pipes '10 are secured to the sleeve 6 ina'ny' preferredmanner, sue-h as for example by bolts extending through perforations 25 in the sleeve and pipe thus brought into registration with each other. The roof is then supportedabove the bottom of the tank by the pipes'10and the hoisting devices can be removed and the roof completedby the addition of sealing devices, vents, underdeckdrain pipes, and the like. After these devices have been added, the tank may be completed by erecting-the walls in the usual manner.

Thus it will be seen that the process ofth'e'presen invention simplifies the installation and construction or; floating roof-in a storage tank by considerable reduction or eliminationof temporary structure used for supporting the roofin working position during such construction. A minimum of apparatusv is required, the overall cost and materials are less, and'part of the-perm'anen't r'oof structure is utilized to accomplish thesepiirpose'si While I' have chosen to illustrate myinvention by showing and describing a preferred embodiment of -it, I have" done so by' way' of exampleas there are many modifications and adaptations which can be niade by one skilled in' the art, to meet'varying conditions encountered, within the teachings of the-inveiition.

Having thus com-plied with'the'statutes and shown and described a preferred embodiment of my invention, what I consider new" and desire to have protected by Letters Patent is pointed out in the 'appendedclaiins;

'What' is claimed is: v

l. The method of erecting' a' pontoon-supported floating'roof for a cylindrical't'ank, whichmer has a'continuous= peripheral pontoon, a' center pontoon and a single deck extending between said pontoons, which coinprisesi constructing the b'ottomof the" tank; constructing the'pontoons' and'deck upon the bottom; installing vertical sleeves at spaced apart points through and near the'inner periphery of the peripheral pontoon and through and near the outer periphery of the center pontoon; projecting supporting pipes-ofgre'aterlength than the sleeves through-saidsleevesinto engagement with the bottom; attaching a hoistingdevicebetween each pipe and the deck; opera-ting said hoisting" devices to raise the-deck into desired registration withthe-pontoons;

welding thedeck'to the pontoo'nsj operating said hoisting devices to raise the roof onsaidpipe'sintd workingposition; fastenin'g'thesleeves to the pipesto secure the roof in working position; and completing the thus secured roof.

2; Themethod of erecting and' installing" a roof that floats upon the liqin'd in afcylindrical'storagetank; which comprises: constructingithe bottom of'th'e'tank; erecting -the' basie structure of the roof on's'aidbottom with a plurality. of vertical sleeves extendingythcrethi'ough at spacedapart points in-the roof; then projecting through each sleeve a pipe that engages .said bottom and extends abovethe sleeve and roofpthenattaching;a hoisting: de-

vice between the top of each pipe and the roof; operating said hoisting devices to raise the roof on the pipes into a working position above said bottom; securing said roof in said working position by attaching it to said pipes; removing said hoisting devices; and while the roof is thus secured in said working position, attaching to it the devices required beneath and on the underside of it, thereby to complete the erection and installation of the roof.

References Cited in the file of this patent UNITED STATES PATENTS Gladnille Nov. 12, Harvey Dec. 8, Laird July 9, Allen May 29, Orr et a1. Feb. 26, Wiggins May 22,

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