US3915332A

US3915332A - Floating roof

Info

Publication number: US3915332A
Application number: US438650A
Authority: US
Inventors: Nestor Leon Pladys
Original assignee: BP PLC
Current assignee: BP PLC
Priority date: 1973-02-06
Filing date: 1974-02-01
Publication date: 1975-10-28
Anticipated expiration: 1992-10-28
Also published as: JPS49111422A; NL7401262A; FR2216815A5; GB1449962A; BE810678A; IT1008801B; DE2405410A1

Abstract

A floating roof suitable for use with petroleum product storage tanks having a light framework on which there is fixed a sealing screen. The framework is a double grid comprising a number of upper and lower horizontal tubes arranged one above the other which are integrated by a larger number of intermediate horizontal tubes at right angles to the upper and lower horizontal tubes. The tubes of the grid are fixed to a peripheral circular rim which is adapted to seal with the storage tank.

Description

United States Patent 11 1 Pladys [45] Oct. 28, 1975 FLOATING ROOF 2,586,856 2/1952 Orr 61 a1. 220/26 R 2,806,625 9/1957 Wiggins 220/26 D [75] Invent Nest" Pladys Rosendael, 3,362,562 1/1968 Marshall et al. 220 26 R France 3,374,918 3/1968 Creith 220/26 R [73] Assignee: The British Petroleum Company Limited, Londo E l d Primary ExaminerWilliam I. Price Assistant ExaminerStephen Marcus [22] Ffled' 1974 Attorney, Agent, or FirmMorgan, Finnegan, Pine, [21] Appl. No; 438,650 Foley & Lee

[30] Foreign Application Priority Data [57] ABSTRACT Feb. 6, 1973 France 73.04147 A floating roof Suitable for use with Petroleum Prod uct storage tanks having a light framework on which 52 US. Cl. 220/220; 220/224; 220/225 there is fixed Sealing screen- The framewmk is a 51 Int. cl. 865D 87/207; B651) 87/213 duble grid comprising a number Pl and 5 Field f Search 220/26 R 26 s, 26 SA horizontal tubes arranged one above the other which 220/26 D, 26 E 216427 are integrated by a larger number of intermediate horizontal tubes at right angles to the upper and lower [56] References Cited horizontal tubes. The tubes of the grid are fixed to a UNITED STATES PATENTS peripheral circular rim which is adapted to seal with the storage tank. 1,777,560 10/1930 Griffin 220/26 R 2,282,772 5/1942 Wiggins 220/26 R 0 l ims, 5 Drawing Figures US. Patent Oct.28, 1975 Sheet 1 of5 3,915,332

US. Patent Oct. 28, 1975 Sheet 3 of5 3,915,332

US. Patent Oct. 28, 1975 Sheet40f5 3,915,332

US. Patent' Oct. 28, 1975 Sheet 5 of5 3,915,332

FLOATING ROOF The present invention relates to a floating roof suitable for use with a liquid product storage tank.

British Patent Application No. 43283/72 and corresponding U.S. patent application Ser. No. 290,761,-

filed Sept. 20, 1972, U.S. Pat. No 3,885,699 describes a floating roof comprising a central framework with one or more substantially concentric floating rims, the rims being connected to said framework by means of tensioning cables adapted to give a stable structure and 'a covering sheet adapted to be supported by the framework and rims.

According to the present invention there is provided a floating roof having a framework supporting a sealing screen, said framework comprising a grid of upper and lower horizontal tubes integrated with one another by further horizontal tubes at an angle to the upper and lower tubes, the further tubes being also integrated with one another at a peripheral rim, which rim is adapted to make substantially sealing contact with the side of a liquid product storage tank.

The grid consists of a small number of tubes known as upper tubes and lower tubes, superimposed on one another and braced by a larger number of further horizontal tubes arranged preferably substantially perpendicularly to the said upper and lower tubes or forming a suitable angle in relation to these tubes.

The three horizontal beds of crossed and superimposed tubes have the purpose of imparting a considerable degree of inertia to the framework so that it will tolerate flexural stresses.

All the tubes terminate in the vicinity of the wall of the storage tank and are welded at their respective ends to the inner wall of the said peripheral rim, the crosssection of which is preferably rectangular. The framework includes props of the type described in the abovementioned application at the points of intersection between the said upper and lower tubes on the one hand and the said intermediate tubes on the other hand or at any other chosen point of the generatrix of the tubes of the intermediate row.

These props may slide inside sheaths provided at the said points of intersection and crossing the different tubes above-mentioned.

The sealing screen, is in the form of a roof, the ridge of which is located parallel to the upper and lower median tubes of the said double grid and between the tubes.

Preferably the peripheral sealing joint comprises an articulated collar pivotally attached to the rim, the collar being fitted with a first inflatable attachment and a second inflatable attachment that is nearer to the pivot than the first inflatable attachment the attachments being on opposite sides of said collar and being adapted, so that, upon inflation, the second inflatable attachment is pressed against the rim, and, by principle of levers, presses the first inflatable attachment against a surrounding wall of the tank.

However, other types of joint may also be used, pro-- vided that the fitting is capable of ensuring a seal as between the gaseous phase over the hydro=carbons and the ambient atmosphere, which may contain products harmful to the petroleum product being stored.

The peripheral rim consists of a circular tube of square cross-section with a vertical axis and of an external diameter which is slightly less than that of the storthat of the tank.

age tank so as to take into account the space necessary for the fitting of the said sealing joint.

The assembly, as between the lower and upper tubes on the one hand and the perpendicular intermediate tubes on the other, is usually achieved by welding and by insertion one into the other, but when the thickness of the roof is of little import, as is the case for tanks of large dimensions, the tubes may be assembled by welded intermediate parts.

The vertical sheaths provided atthe level of the assembly nodes serve, if necessary, as fixing points for cables or tie-rods which make it possible to place the framework under tension so as to make it capable of withstanding considerable mechanical stresses of compression, flexure and torsion which may be imparted to them accidentally by external agents, especially in the case of tanks of a large diameter.

The provision of horizontal floating tubes generates a large area of contact with the liquid, which creates a resistance to the movements of the framework. This may allow construction without the requirement of supplementary stabilizers.

It is always necessary to provide simple props in order to support the framework in a horizontal position when the tank is empty.

The sealing screen consists of elements of thin corrugated sheeting, preferably of galvanised steel, and having a good resistance to vertical loads, the elements being joined together along their respective edges parallel to the said corrugations.

This screen is housed below the upper floating tubes and is integrated with the said intermediate tubes. It preferably forms two symmetrical slopes of uniform gradient from its median crest as far as the said peripheral rim.

However, in the case of large tanks, the symmetrical slopes may be interrupted by slopes in the opposite direction and form alternating ridges and low points where the water can be collected.

This arrangement makes it possible to create more accentuated gradients and to avoid large volumes of gaseous material imprisoned under the roof.

The thin sheet metal may be formed, for example, of standardized elements of the great length having a width of the order of 1 meter The sheet metal is generally fixed on the said intermediate tubes and on the peripheral rim by means of welded flat irons and blind leakproof riveting or any other known process.

This sheet metal is also fixed on to intermediate stringers parallel to the different upper and lower tubes and located on either side of these tubes, this fixing being carried out by established processes.

In the case of an upwards thrust being exerted on the floating tubes, it is necessary to consider that the lower tubes are completely immersed while the upper tubes are at a higher level than that of the liquid stored.

There also persists between the sealing screen and the level of this liquid a gaseous atmosphere which is very rapidly saturated by hydrocarbon vapors. However, this gaseous phase is isolated from the ambient air and its gaseous composition does not alter. In contrast the emptying of a tank with a fixed roof may cause the re entry under is fixed roof of a volume of air equal to Such a framework may enable the floating roof to support over loads of for example, as much as 50 kgs. per sq. m.

It should be observed that the gaseous atmosphere which is located under the sealing screen isolates the stored liquid from the said screen, reduces the transmission to the framework of the action of the wind on this screen and prevents the possible creation in the stored liquid of the phenomenom of resonance which could cause damage to the framework.

In the event of a considerable accidental overload, the roof is forced in, the higher peripheral rim giving it the form of a plate which imparts to the said floating roof a very important increase in buoyancy which may reach as much as 150 kgs. per sq. m.

In such an exceptional case, the sealing screen comes to rest partly or wholly on the surface of the liquid, but since this screen is in any case very light, it is supported uniformly by floating tubes and is subjected to an upwards thrust, so the mean plane of the said screen remains horizontal without being subjected to any excessive stress.

Finally, the flow of rainwater off-the roof is achieved by the 'water travelling along the two slopes of sufficient gradient as far as the periphery of the said screen or as far as the intermediate points where it is collected by an articulated tube of the established type. Moreover, in the event of an abnormal accumulation of rainwater, the tubes of the upper row which are located above this screen form separations which brake the flow of the said rainwater. The equilibrium of the roof is therefore ensured.

The mean weight per square meter of the new floating roof may in practice be two to four times less than that of the old forms of embodiment known as single or double decle.

The invention will now be described, by way of example only, with reference to FIGS. 1 to of the drawings accompanying the specification.

FIG. 1 is a plan view showing in particular the grid of the framework;

FIG. 2 is a vertical cross-section along the line lI-II of FIG. 1;

FIG. 3 is a vertical cross-section along the line IIIlII of FIG. 1;

FIG. 4 is a cross-section similar to FIG. 3, but showing the above-mentioned props in a position which permits of the supporting of the said floating roof when the tank is empty;

and FIG. 5 is a section along the line V-V of FIG. 1 showing the method of assembly as between the different elements of corrugated sheet metal, along their respective longitudinal edges.

It will be seen in FIG. 1 that the tank with a diameter of 20 m. includes a grid framework having three

upper tubes

1, 2 and 3, under which there are located three lower tubes la, 2a and 3a which are not visible in FIG.

The grid is supplemented by intermediate tubes which are visible respectively at 4, 5, 6, 7 and 8 in FIG. 1.

The lower part of the props provided at the level of the nodes of the said grid or at. any other point of the generatrix of the intermediate tubes is shown in broken lines at 9 or 9b.

A tear-away has been provided in the elements of corrugated sheet metal 10 which connect the intermediate tubes 4 to 8 and which also connect the outer intermediate tubes 4 and 8 to the peripheral rim 11. The inner wall of the rim, on which the ends of the different above-mentioned tubes 1 to 8 and 1 a and 3a are welded via flat irons lb to 8b, 10 to 30, can be seen at 11a in FIG. 1.

This rim of rectangular section consists of a circular bent tube and is visible in particular in FIGS. 2 to 4.

FIG. 1 shows a number of intermediate stringers 12 to 19 which are parallel to the said upper and lower tubes and located respectively between these different tubes and also between the outer tubes 1 and 3 and the peripheral rim 11.

These intermediate stringers are also welded at their respective ends to the peripheral rim 11.

FIG. 2 shows the intermediate tubes 6 to 8 as well as the peripheral rim 11 which is equipped with a joint holder collar 20 mounted so as to ensure the leakproofness of the periphery of the said tank 21 between the gaseous phase 22, which is located above the stored liquid, and the ambient atmosphere 23, which is above the joint proper 24.

The joint-holder collar 20 is equipped in its upper part with a second joint 25 which, in conjunction with the collar 20 and the joint 24, ensures the leakproofness between the peripheral rim 11 and the tank 21.

Provision has been made at each,of the assembly nodes of the above-mentioned double grid for sheaths 26 within which the rods 27 of the props 9 slide.

These horizontal props have been shown but clearly in the case of tanks with an inclined bottom the props are arranged parallel to this bottom so as to come into contact with the tank bottom in the lowest position of the floating roof as shown in FIG. 4.

The sealing screen can be seen at 28 and is welded to the peripheral rim and to the intermediate tubes 4 to 8. This sealing screen is at a higher level than that of the level 29 of the liquid stored.

FIG. 3 shows the

upper tubes

1 and 2 and the lower tubes 1a and 2a as well as the corresponding props 9 provided at the assembly nodes, the rods 27 of which slide inside the sheaths 26.

FIG. 3 shows intermediate stringers 12 to 15 on which there are fixed the elements of sheet metal 10 constituting the sealing screen 28.

FIGS. 3 and 4 show the rigid tie-

rods

30 and 31 intended to increase still further the rigidity of the gridtype framework.

It will be seen from these figures that these tie-

rods

30 and 31 do not pass through the sealing screen 28, thus facilitating assembly.

As stated above, the rainwater collects in the lower part of the two symmetrical inclined planes constituting the said sealing screen 28, and an orifice located at one of the two low points of the flow of this rainwater through an articulated tube 32 to afixed discharge pipe 33.

FIG. 4 shows the position of the prop 9 which corresponds to the low position of the floating roof.

As stated previously, if the bottom of the tank were inclined, the props 9 would also remain located parallel to this bottom. The rods 27 of these props are, in this position, withdrawn to the maximum extent inside the sheaths 26.

FIG. 5 shows panels of section sheet metal 10 which extend between the parallel lines 10a and which are assembled in the vicinity of their respective ends 10b.

These panels also include ribs of a height which is more or less the same as that of the ends 10b, and intermediate ribs 10d which are less accentuated.

I claim: y

l. A floating roof for a liquid product storage tank having a framework supporting a sealing screen, said framework comprising a grid of parallel upper and lower horizontal tubes extending across the width of said floating roof, and a peripheral rim, said parallel upper and lower horizontal tubes being integrated withone another by further horizontal tubes at an angle to said parallel upper and lower horizontal tubes, said upper, lower and further horizontal tubes being integrated with one another at said peripheral rim, said rim including means for making substantially sealing contact with the wall of said liquid product storage tank.

2. A floating roof according to claim 1 in which the further horizontal tubes are arranged substantially perpendicularly to the upper and lower tubes.

3. A floating roof according to claim 1 in which the peripheral rim makes sealing contact with the liquid product storage tank by means of a peripheral sealing joint comprising an articulated collar pivotally attached to the rim, the collar being fitted with a first inflatable attachment and a second inflatable attachment that is nearer to the pivot than the first inflatable attachment,

the attachments being on opposite sides of said collar and being adapted, so that, on inflation, the second inflatable attachment is pressed against the rim and by principle of levers presses the first inflatable attachment against a surrounding wall of the tank.

4. A-floating roof according to claim 1 in which the peripheral rim comprises a circular tube of square cross-section.

5. A floating roof according to any of claim 1 in which the sealing screen is integrated with the horizontal tubes and has at least two slopes of opposite gradients.

6. A floating roof according to claim 5 in which the ridge of the sealing screen is located parallel to the upper and lower horizontal tubes of the grid and between said tubes.

7. A floating roof according to claim 1 in which the sealing screen comprises elements of thin corrugated sheeting, said elements being joined together along their respective edges and parallel to the corrugations.

8. A floating roof according to claim 7 in which the elements of sheeting are made from galvanised steel.

9. A floating roof according to claim 1 in which the framework is provided with props adapted to support the framework in a substantially horizontal position on the base of the substantially empty liquid product storage tank.

10. A floating roof according to claim 9 in which the props are adapted to be slidably adjustable in a substantially vertical plane.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION- PATENT NO. 3,915,332 DATED I October 28, 1975 INVENTOR( I Nestor Leon Pladys H. is certified that error appears in the above-identified patent and that said Letters Patent aye hereby corrected as shown beiow:

In Claim 5, line 1, delete "any of".

Signed and Scaled this ninth Day Of March 1976 [SEAL] I A ttest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner oflarents and Trademarks

Claims

1. A floating roof for a liquid product storage tank having a framework supporting a sealing screen, said framework comprising a grid of parallel upper and lower horizontal tubes extending across the width of said floating roof, and a peripheral rim, said parallel upper and lower horizontal tubes being integrated with one another by further horizontal tubes at an angle to said parallel upper and lower horizontal tubes, said upper, lower and further horizontal tubes being integrated with one another at said peripheral rim, said rim including means for making substantially sealing contact with the wall of said liquid product storage tank.

3. A floating roof according to claim 1 in which the peripheral rim makes sealing contact with the liquid product storage tank by means of a peripheral sealing joint comprising an articulated collar pivotally attached to the rim, the collar being fitted with a first inflatable attachment and a second inflatable attachment that is nearer to the pivot than the first inflatable attachment, the attachments being on opposite sides of said collar and being adapted, so that, on inflation, the second inflatable attachment is pressed against the rim and by principle of levers presses the first inflatable attachment against a surrounding wall of the tank.

4. A floating roof according To claim 1 in which the peripheral rim comprises a circular tube of square cross-section.