FLOATING ROOF OF SYNTHETIC MATERIAL FOR LIQUID STORAGE TANK

Abstract: The improvement relates to a method for the installation of a floating roof structure in a closed liquid storage tank and also it relates to the tank roof structure obtained thereby. It is the purpose of the invention to compose out of a great number of interconnectable synthetic modules or synthetic sandwich boards (3) backed up by a large number of prefabricated low frame profiles (4), an integral floating roof structure (1) of extremely lightweight construction. Furthermore it is particularly important as a feature that this floating roof structure (1), by its own rigidity and its overall strongness, can fully operate itself as a building site because of the fact that the traverse frame profiles (4) used for strenghtening the roof surface structure by interconnecting sandwich modules (3) have a height of e.g. no more than 2 times the single height of a module, i.e. no more than 15 cm. The level of liquid in the storage tank is now covered to a high degree, and apparently it is now possible to suppress even the recent tolerable rate of vaporization enormously, thereby contributing much to the desired degree of environmental purity.

Description: FLOATING ROOF OF SYNTHETIC MATERIAL FOR LIQUID STORAGE TANK The Invention relates io a method for the Installation of a floating roof struct a dosed liquid storage tank and further it relates to a floating roof obt thereby. In view to steadily increasing requirements In environmental legislation fo βtorage of volatile liquid products it becomes a tendency to avoid the creati a level of liquid underneath the floating roof as such creation could give ris substantionai environmental problems. Storage tanks for liquid products may have a diameter from e.g. 8 to nearl meters and In the latter case enormous volumes of liquid vapour mus discharged to the open air. This encounters extensive environmental prob because mostly such 1 stored volatile liquids dangerously affect the breathi human beings and animals. Metal floating roof structures are known which may sink down as a result of li movements and or leakage, resulting again In the creation of a level of liquid. there do exist floating roofs which are underneath covered with an aluminiu yet giving rise to . locally created levels of liquid, causing the aforementi disadvantages. Moreover a floating tank roof structure must be sufficiently st to be usable as a building site for carrying out repair activities. According to the invention a floating roof structure, also serving as a building may be Installed in a closed storage tank for liquid, which roof is composed number of interconnected synthetic modules thereby carrying out the follo steps: & a great number of fully enclosed sandwich module board elements reinforced synthetic rhaterial, provided with a core of hard foam and also b locally provided with taert pieces of screwable material, are lengthwise so positioned that they Constitute altogether an uninterrupted flat working floor surface, which by providing of corresponding roundings for the tank wall, w correspond in its shape and its size with the floating roof to be installed, whe this working floor is supported, at least for a substantial part, by a temporary premouπted fiat horizontally positioned roof support scaffolding structure whi located underneath and at a certain distance from the tank bottom; b. at the upper side of the working floor and In a direction which is perpendicular to the longitudinal axis of sandwich module boards there are positioned a number of oblong transverse frame profiles which are fixedly connected to the sandwich module boards by means of fasteners thereby providing for a stiff Integral roof structure; c. thereafter the roof structure is provided with operational means such i. a manhole in order to carry out activities underneath the roof structure; li. at choice a number of roof structure supporting legs, which may or may not be adjustable; Hi. a number of cable bushings for the use of anti-rotation cables to prevent an undesirable rotation of the roof structure; fv. at choice a number of drainages for condense liquid; v. at choice a number of air inlet and air discharge means; whereafter the horizontal roof support scaffolding structure Is dismounted an taken out of the tank allowing the floating roof structure to rest upon its own supporting legs or to rest upon a number of fixed supporting legs which we installed before on the bottom of the tank; d. the longitudinal and traverse seams between adjacent modules of the working floor for the roof structure are sealed off at the bottom side of the roof structure by means of self-adhesive tape thereby forming a totally flat surfϋoe, whereafter for the prevention of gas and air Inclusions, the seam slit is further fitted up with synthetic material of the skin material of the sandwich module, the self adhesive tape belog removed or not after hardening; e. the flexible tank wail seal Is thereafter mounted to the circumferential edge of the roof structure. In a preferred embodiment of the invention the floating roof structure Is buil of sandwich module boards and traverse frame profiles, characterized in th traverse frame profile has a polygonal vertical cross section and Is compose two preferably rectangular tubular profiles, one on top of the other, particular lower square tubular profile and on top of it an upper rectangular tubular pr resting upon its short jrectangular side. It is effective to bu up the tank roof structure according to βtill ano embodiment of the Indention with a number of cut-off profiles each time havin length of at least two times the width of a sandwich module is applied for, in s r a way that every time' the utmost ends of the lowermost square tubular pro and also the utmost jmds of the upper rightanglβd tubular profiles are alw located In the central portion of the sandwich module. It appears that for eas^ handling the length of a cut-off profile preferably amo 1,000 mm whereas tiie total integral cross section of the traverse frame pr amounts to 50 x 50 a d 50 x 30 square mm respectively. Thereby the stiffness of the built up tank roof structure may be efficiently obtai while using a standard sandwich module having a width of 500 mm, a lengt 6,000 mm and a thickness of 50 mm. In order that a sandwich module possesses sufficient rigidity It may be provid a direction perpendicular to Its longitudinal axis with Integral Insert pieces screwable material at regular distances preferably made of hard screw poiylamlnated wood (Multiplex), which pieces are Incorporated In the foamed c material for the f n of screws and suchlike fixing elements in and to I sandwich module, j According to the Invention at Its bottom side, the tank roof structure is enti flat except for the presence of a required manhole flange and various bushings (for cables, air inlets, air outlets, supporting legs) respectively so th is virtually Impossible jthat spaces are created having a level of liquid. At the hand the floating tanK roof structure is light enough to float upon the level of liq whereas at the othef hand It is pertinently unsinkable, this embodiment of structure constitutes such a rigidity that no Iquld volumes are collected upon tank roof and thus ni unallowable vaporization wBl occur. By using a great nunjber of adjustable support legs provided for underneath floating tank roof structure, the entire roof structure Is equally supported various locations wltrf respect to the bottom of the storage tank and all provisi are available to makfe the operational use of the tank roof structure profita thereby excluding ant disadvantages which Inherently affect existing floating t roof structures. \ According to another! embodiment of the Invention there are provided air Inlet air discharge means for a tank roof structure consisting of a potshaped hous having a number of parts, provided with at least one fixing flange for connec It with the opening in a sandwich module and a cup shaped cover of the hou being provided with * number of air inlet and discharge openings respecti which are covered by a flexible non-return valve, a vertically movable bar b centrally petitioned Iπ-the cover, which bar is provided at its upper end above cover with an eyelet f r connection to a cable and within the housing under cover and perpendicular thereto said bar Is provided with a number of clo discs, each having an Outer circumferential downwardly directed cupshaped e whereas the inner bide of said housing is provided with a number corresponding downwardly directed funnel-shaped concentric baffles, in su way that vapors passing through said means are forced to escape via labyrinth seal. I Also according to Vni invention there is provided for in a permanent fixatio means of a magnet k ping the floating roof structure In place by means of of the tank by mβans!of anti-rotation cables characterized In that a flat magn provided having horizontally and centrally respectively in at least two mut perpendicular directions a number of anti-tilting elements, one and the other a way that a possibψ tilting point or tilting Ine with respect to said fe loc substantially far awfiy and outwardly from the utmost borderline of circumferential edge if the permanent magnet which holds to the bottom o storage tank. j The Invention will now be further described with reference to the accompan drawing of an embodiment shown at different scale dimensions. Fig. 1 te a schematic pper view of a floating tank roof structure ao∞rdlng Invention; [ Fig. 2 shows schematically and in cross section the location of the tank structure which is supported upon the bottom of the tank by means of a number of support legs; Fig. 3 shows separately a synthetic module as part of the flat surface of the roof Fig. 4 te partially a cross section through a preferred embodiment of the tank structure taken at thi sealing off against the waX of the tank; Fig. 5 also shows a partial cross section of another preferred embodiment tank roof structure as 'Shown in Fig. 4; Fig. 6 is a cross sectjon of the traverse frame profiles which are applied render the required stiffness and strongness to the tank roof structure; Fig. 7 shows a special anchoring structure to fix the position of the floating t roof; I Fig. 8 is a cross sed ion of a bushing in the tank roof In use for a dip gauging tube and forlantl-rotation cables; Fig. θ is a cross sedtion of a sampling device provided for in the tank r provided with a star-shaped flexible non-return valve; Fig. 10 Is a liquid valour-overpressure drain valve provide with a labyrinth avoiding liquid to arrive upon the tank roof; Fig. 11 is a cross sedtion of the manhole structure for the tank roof. According to the invention the method basically consists in the composition o entire floating tank roof 1, shown in Fig. 1 and 2, which has a flat synthetic b covering 2 having floating properties. The strongness and the stiffness of synthetic covering 2 ά obtained by interconnecting a great number of sand modules 3 to form a; flat surface while using traverse frame profiles 4, eac which is constituted by a number of tubular, preferably rectangular profile which are traversaliy coup-led to the sandwich modules 3 In a special manne Prior to building up st floating tank roof 1 at the Inside of a storage tank β t Is erected upon the bottom 7 of the tank, at a workable level of e.g. 80 c scaffolding having a flat upper surface (not shown here) upon which the sand modules 3 are positioned. After completion of the tank roof structure scaffolding must be dismounted and finally be carried away through the man 8. Upon this flat supporting surface ad sandwich modules 3 are now horizon positioned according! to Fig. 1 and nearby the wal 9 of the tank the sand modules 3 are adapted to the rounded shape. Internally these sandwich mod 3, see Fig. 3, are provided with a foamed core material 10 which Is compo from e.g. a flat core o hard foam sandwiched between two glass fiber reinfor outer skins 11. It is obvious that the sandwich module 3 Is entirety unsuscep for affection by the liquid stored in the tank β; this being important in the e of mechanical damage to the tank roof structure. The thickness of the sand module 3 is e.g. 50 Jm whereas the outside dimension of a single, prefer rightangled, in the drawing shown square profile 5, embodiment amounts to x δO mm. Figs. 4 arιd_5 βhow the arrangβmert of tto iwβreβ frame r a direction perpendicular to the longitudinal axis of the oblong sandwich mo 3. One tubular profile 5 which has a rectangular cross section, having an ov length of e.g. 100 cm, Is bondwtse placed upon a first lower row of tub profiles 5, see Fig. β, ! and it Is effective to let the longitudinal seam 12 betw adjacent sandwich modules 3 coincide with an abutting seam 12* between square profiles 5. It fe advantageous for obtaining a greater resistance aga bending to compose traverse frame profile 4 from a lower square tubular pr on top of which in aii upright position, a narrower rightangled tubular profil positioned. The traverse frame profile is a reversed T-profile compositi dimensions 50 x 50 m and 50 x 30 mm respectively. At the one hand Installa takes place with short standard lengths, at the other hand It simplifies a q mounting and disassembly respectively- in the hard foam core material sandwich module 3 a d upon regular distances there Is integrally Incorporated insert piece 13 of har<J screwable material sufch as polylamlnatβd wood (Multipl which will stand the fixation of fixing elements, Oke screws 14. After all preparations 1 have been made and the tank roof structure has b completed, all longitudinal and traverse seams 12 between adjacent sand modules 3 must be sealed off against liquid. To that purpose the seams 12 now at the bottom ώde of the tank roof structure entirety sealed off with adhesive tape and than these seams are fined up from the top side with same material of whibh the skin covering 11 Is made. After hardening out t is created an Integral roof which fulfills all required properties with respect t own floating power, the self-adhesive tape may be removed after hardening of the filled out seam, however this Is not afways necessary. After the tank roof structure has been completed, the seaftng 15 must be Inst its construction being here described in a global way only. In F . 4 an end sealing tip 16 is liquid tight connected by means of a colar 17 to the edge of tank roof 1 and the position of the tank roof 1 1s defined also by a spring ele 18 the one end 19 of which is connected to a seal Up 16 whereas the otiier 20 is fixed, through a spring loop 21, to the tank roof 1. Fig. 5 shows another seal in cross sectional view, consisting of a flexible bumper 16' which Is fixe the tank roof 1 by means of a distance holding device 18'. Fig. 7 sho bushing 22 in the saiidwtch module 3 for an anchoring cable 23. The upper of this anchoring cable 23 is fixed to the fixed roof of the storage tank 6 an lower end 24 is connected to the upper sde of a permanent magnet 26 means of a spring 25. It Is the purpose to anchor the magnet 26 to the bot 7 of the tank, the presence of a number of anti-rotation cables 23 thereby hol the position of the jfioating tank roof 1. The magnet 26 is provided protrusions 27 e.g. from strip material which Is fixed to the body of the ma 26 by means of damping or the like thus bringing the tilting point far away f the permanent magnetic surface, thereby guaranteeing the permanent locatio the magnet 26 with rispect to the bottom 7 of the tank. The extra advantag this faculty, which is uhbreakably connected to the tank roof structure, Is the avoidance of sooalte hot spotweldlng to the bottom 7 of the tank. In Fig. 8 another bustflng 28 Is shown for a fixed gauging tube (not shown he A flexible collar or cup 29 is clamped between a fixed flange 30 which b bol by means of bolts 14* around an opening in the tank roof 1 and a remov flange 31 so that the tank roof 1 can move in an upward and downward direc with respect to the tbted gauging tube. If necessary, the whole tank roof 1 be sunk for half of Its thickness Into the liquid without affecting Its effectivene For taking liquid samples from the storage tank there is provided a sampl device, Fig. 9, consisting of a funnel-shaped mouth 33 for receiving and center a bottle shaped container (not shown) which is lowered by means of a s shaped cut flexible valve 34 to sample liquid from the tank content. The ann protruding edge 35 at the lower side of the funnel-βhaped mouth 33 rests u and is guided respectively in u tubular passage 36, provided with a flange 37 a counter flange 38 for its attachment to the opening bi the tank roof 1. At level of the flange 37 there are provided In the tubutar widened portion a num of air openings. The alve 34 is attached to the throat of the funnel-shaped mo 33 by means of a hinge 39 and can be opened by means of a cable 40. other cable end is connected to a hook 41 whioh Is adjustably m its hei attached to the tank roof 1. The valve 34 is automatically opened In the event t the lower end of the hook 41 (not fully shown) Is running up against a stop, the bottom 1 of the tank. If as a result of weather conditions e.g. liquid vapour is collected under the t roof 1 which must be discharged, there are a number of dischargers 32 provi upon openings In the tank roof 1, see Fig. 10. A discharger 32 consists of a shaped housing 42 which is downwardly attached to a tubular passage provided with attachment flanges 43 and 44 respectively and connected to tank roof 1. The passage 45 has air openings 46 and It diverges downwardl a funnel 47. The housihg 42 is covered by a cup-shaped lid 48 which Is provi with passage ways 49* which are cioβabie by means of a flexible non-return v 50. A centra] rod 51 having an eyelet 53 can be operated by a cable 23' from upper side and so be lifted or closed. Attached to the rod 61 and to the hou 42 are cooperating labyrinth baffles and discs 64 and 66 respectively w obstruct the escape ς>f vapour. To enable a fast escape however the lid 4 operated by means of the cable 23'. Fig. 11 shows details ;of a manhole. The manhole cover 66 rests upon a tub collar flange 57 circumferential edge of the manhole 8. The flange is attache means of screws 14' screwed in the hard polyiaminated (Multiplex) material wi the sandwich module; 3. in the central portion upon the manhole cover 56 t is a passage opening 1 in which a discharger 32, see Fig. 2, can be installed further handgrips are provided at the upper and bottom side respectively of manhole cover 66. Fig. 2 schematically sjhows the adjustable support legs 60 which are guided and attached to the tank roof 1 by means of tubular guidlngs 61. At choice s support legs may have a fixed length and are attached to the tank roof 1 means of a tubular guiding 61 or the support tegs 60 and their guidlngs 61 provided of adjustable locking devices, known per se. The floating tank roqf 1 Is of very light construction and it has a high floa power and, by its enormous own rigidity resulting from the use of sand modules and low travferβe frame profiles, is also an Weal building floor for oaπ out maintenance activities. The smooth surface underneath It prevents all exis disadvantages with known tank roofs. Considering the very smal height of tank roof 1, e.g. 50 fnm of the sandwich module plus two times 50 mm for composing tubular profiles 5 of the traverse frame profile 4, Its total height I more than 15 cm (I); at the location of these traverse frame profiles 4. In Fig. 1 the simple and systematic building up of the tank roof structure by new method is made visible. The modular arrangement makes It possible to m tank roofs of different dimensions having the same favorable floating power. use of the sandwich structure having a hard outer skin make no longer a pro of possible damages and their quick repair. Since the construction is realized with simply operable sandwich modules a whereas the tubular profiles are easily handled during mounting and demounti because of the small length, this novel method offers great advantages end ex safety for the environment, now that even for very great tanks only a minim evaporation will occur and so It remains controllable. Apart therefrom this floati roof together with Its synthetic sandwich modules has a specific heat insulati function for the liquid which is stored in the tank. Potent dal

Claims: PATE T CLAIMS 1. Method for the Instillation of a floating roof structure in a closed storage tan for liquid, which roof is composed of a number of Interconnected syntheti modules thereby carrying out the following steps: a a great number of fully enclosed sandwich module board elements of reinforced synthetic material, provided with a core of hard foam and also bein locally provided with ihsert pieces of screwable material, are lengthwise so positioned that they c nstitute altogether an uninterrupted flat working floor surface, which by providing of corresponding roυndings for the tank wall, will correspond in Its sha^e and its size with the floating roof to be Installed, where this working floor is supported, at least for a substantial part, by a temporary a premounted flat horizontally positioned roof support scaffolding structure which i located underneath and at a certain distance from the tank bottom; b. at the upper side of the working floor and In a direction which is perpendicular to the Ibngltudlnal axis of sandwich module boards there are positioned a number of oblong transverse frame profiles which are fixedlya) Ro connected to the sandwich module boards by means of fasteners there providing for a stiff integral roof structure; c. thereafter the roof structure provided with operational means such as i. a manhole in order to carry out activities underneath the ro structure : 11. at choice a number of roof structure supporting legs, which may may not to adjustable; lit. a number of cable bushings for the use of anti-rotation cables prevent art undesirable rotation of the roof structure; Iv. at choice a number of drainages for condense flquld; v. at choloe a number of air Inlet and air discharge means; whereafter the horizontal roof support scaffolding structure Is dismounted a taken out of the tenk allowing the floating roof structure to rest upon supporting legs or to 'rest upon a number of flxed supporting legs whloh Install before on the bottom of the tank; d. the longitudinal and traverse seams between adjacent modules of t working floor for the roof structure are sealed off at the bottom side of t roof structure by means of setf-adheslve tape thereby forming a totally surface, whereafter for the prevention of gas and air inclusions, the βea is further filled up with synthetic material of the skin material of the sand module, the self adhesive tape being removed or not after hardening; e. the flexible tank wall seal is thereafter mounted to the circumferential e of the roof structure. 2. Floating roof structure which is composed, according to claim 1, of sandwi module boards and traverse frame profiles, characterized in that a traverse pr has a polygonal vertical cross section and is composed by two prefer rectangular tubular profiles, one on top of the other, particularly a lower tub profile and on top of it an upper rectangular tubular profile, resting its s rectangular side. 3. Roof structure according to claim 2, characterized In that a number of cu profiles each time having a length of at least two times the width of a sand module is applied for, in such a way that every time the utmost ends of lowermost square tubular profiles and also the utmost ends of the up rightangied tubular profiles are always located in the central portion of sandwich module. 4. Roof structure according to aim 3, characterized In that a cut-off profile a length of about 1,000 mm whereas the total Integral cross section of the trave frame profile amounts to 50 x 50 and 50 x 30 square mm. 5. Roof structure according to daim 4, characterized In th the βanΛvlch mo preferably has a width of 500 mm and a length of 6,000 mm at a thickness of mm. 6. Sandwich module to be used for a roof structure according to claim characterized in that locally, In a direction perpendicular to its longitudinal a integral insert pieces of screwable material are provided at regular distan preferably of hard screwable potylamiπated wood (Multiplex), which pieces Incorporated In the foamed core material for. the fixing of screws and such fixing elements In and to the sandwich module. 7. Roof structure according to claims 2-5, characterized in that its bottom side i entirely flat except for the presence of a required manhole flange and variou bushings (for cables, air Nets, air outlets, supporting legs) respectively. 8. Roof structure according to daim 7, characterized in that the floating ro structure Is provided with a great number of adjustable support legs which equall support the entire roof structure on various locations with respect to the botto of the tank. 9. Air inlet and air discharge means for a roof structure according to any one the foregoing daims- 2-5 and 7-8, characterized that a pot-shaped housin consisting of a number of parts, is provided with at least one fixing flange f connecting it with the opening in a sandwich module and a cup shaped cover the housing being provided with a number of air inlet and discharge openin respectively which are covered by a flexible non-return valve, a vertically movabl bar being centrally positioned in the cover, which bar is provided at its upper en above the cover with an eyelet for connection to a cable and within the housin under the cover and perpendicular thereto said bar Is provided with a number closed discs, each having an outer drcumferential downwardly directe cupshaped edge, whereas the inner side of said housing is provided with number of corresponding downwardly directed funnel-shaped concentric baffle in such a way that vapors passing through said means are forced to escape v this labyrinth seal. • 10. Permanent magnet fixing means for keeping the floating roof structu according to daims 2-5 and 7-8 respectively In place with respect to the botto of the tank by means of anti-rotation cables characterized In that a flat permane magnet is provided horizontally and centrally respectively in at least two mutua perpendicular directions of a number of aπti+tilting elements, one and the other such a way that a possible tilting point or tilting line with respect to said magn is located substantially far away and outwardly from the utmost borderline of t drcumferential edge of the permanent magnet which holds to the bottom of t storage tank.

Inventors: FABER ALEXANDER, KROESBEEK ROBERT, VAN DER KUIL PIET HUGO ALPHONS, FABER, ALEXANDER, KROESBEEK, ROBERT, VAN DER KUIL, PIET, HUGO, ALPHONSUS
Applicants: FABER ALEXANDER, KROESBEEK ROBERT, KUIL PIET HUGO ALPHONSUS V D, FABER, ALEXANDER, KROESBEEK, ROBERT, VAN DER KUIL, PIET, HUGO, ALPHONSUS
Application year: 1991
Main classification: B65G88
IPC codes: B65D88