WO2015177407A1

WO2015177407A1 - A fluid holding tank

Info

Publication number: WO2015177407A1
Application number: PCT/FI2015/050342
Authority: WO
Inventors: Jukka Lakanen; Pekka TÄHKIÖ
Original assignee: Outotec Finland Oy
Current assignee: Outotec Finland Oy
Priority date: 2014-05-20
Filing date: 2015-05-18
Publication date: 2015-11-26
Anticipated expiration: 2016-11-20
Also published as: FI20145453A7

Abstract

A fluid holding tank (1) for storage and/or handling of fluid, e.g. liquid or slurry, having a shape of a rectangular parallelepiped box and comprising a horizontal floor (2), two vertical side walls (3, 4), and two vertical end walls (5, 6) defining an inner space (7) to receive said fluid. The floor (2), the side walls (3, 4) and the end walls (5, 6) are formed of individually pre-fabricated rigid and flat floor element (2E), side wall elements (3E, 4E) and end wall elements (5E, 6E), respectively, which are fixedly connected to each other by welds to form said fluid holding tank (1), each of said floor, side wall and end wall elements comprising a rectangular frame (8, 9, 10) made of metal beams, said frame having a first side (11) and a second side (12), and a metal sandwich structure (13) comprising a first sheet metal plate (14) having a periphery which is laser welded to the first side (11) of the frame (8, 9, 10), a second sheet metal plate (15) having a periphery which is laser welded to the second side (12) of the frame, and a truss core (TC) sandwiched between the first and second sheet metal plates, said truss core comprising cross profiles (16) made of sheet metal and laser welded to the first and second sheet metal plates.

Description

A FLUID HOLDING TANK FIELD OF THE INVENTION

The present invention relates to a fluid holding tank for storage and/or handling of fluid, e.g. liquid or slurry, having a shape of a rectangular parallelepiped box and comprising a horizontal floor, two vertical side walls and two vertical end walls defining an in^¬ ner space to receive said fluid.

BACKGROUND OF THE INVENTION

In prior art the rectangular tanks made of metal and intended for holding fluids have typically had a structure wherein a space frame (i.e. a rigid three- dimensional framework made of metal beams) forms an outer frame inside which the floor, side walls and end walls made of metal plate are fixed by welding to form the tank. The outer framework is designed and dimensioned so that it bears most of the loads exerted by the hydrostatic pressure of the liquid filled in the tank. A problem is that with this kind of structure the tank is very heavy. The manufacturing of the tank is costly because of a large amount of manual welding required which cannot easily be automated. Manual welding is slow and the quality of the welds may vary a lot depending of the skills of the welder. Because the space frame is assembled from metal beams of many different lengths, this involves also a lot of cutting work .

OBJECTIVE OF THE INVENTION

The objective of the invention is to eliminate the disadvantages mentioned above. In particular, it is an objective of the present in^¬ vention to provide a fluid holding tank which has a structure the manufacturing of which can be simplified and easily automated.

It is also an objective of the present invention to provide a tank which has a light structure.

Further, it is an objective of the present invention to provide a tank which needs less metal beams than the traditional structure which means less cutting of metal beams to different lengths and less manual weld^¬ ing .

SUMMARY OF THE INVENTION

According to an aspect, the present invention provides a fluid holding tank for storage and/or handling of fluid, e.g. liquid or slurry, having a shape of a rec^¬ tangular parallelepiped box and comprising a horizontal floor, two vertical side walls, and two vertical end walls defining an inner space to receive said flu- id. According to the invention, the floor, the side walls and the end walls are formed of individually pre-fabricated rigid and flat floor element, side wall elements and end wall elements, respectively, which are fixedly connected to each other by welds to form said fluid holding tank. Each of said floor, side wall and end wall elements comprise a rectangular frame made of metal beams. The frame has a first side and a second side, and a metal truss core sandwich structure comprising a first sheet metal plate having a periph- ery which is laser welded to the first side of the frame, a second sheet metal plate having a periphery which is laser welded to the second side of the frame, and a truss core sandwiched between the first and sec^¬ ond sheet metal plates. The truss core comprises cross profiles made of sheet metal, said cross profiles be^¬ ing laser welded to the first and second sheet metal plates . The advantage of the invention is that the tank can be constructed as a very light structure due to optimized material usage. The assembly of the sandwich struc- tures can be made by an automated laser welding pro^¬ cess which is very quick and provides better quality than manual welding. The welding speed of laser welding in sheet metal structures can be 5-10 m/min de^¬ pending on the thickness of the metal sheets. Laser welding is a particularly advantageous method of manu^¬ facturing sandwich structures because laser welding is very fast and hence efficient. Joining very thin metal sheets is possible without any through-burning. Weld^¬ ing can be done through a plate. Heat import is mini- mal and therefore also distortion is minimal. The neat weld seams ensure an attractive finish. Further, gen^¬ erally no additives are used. With the principles of the invention it is possible to obtain a tank having a total weight which is 40% less than the total weight of the conventional tank structure with the same vol^¬ ume. For example, 55% less beams are needed in rela^¬ tion to the conventional tank which means less cutting to length and less manual welding. A fluid holding tank can have only three different kinds of elements, a floor element, a sidewall element and an endwall el^¬ ement. The elements can be prefabricated as standard elements from standard profile beams and sheet metal in an engineering workshop by an automated welding laser process. Prefabricated flat elements are stackable for transfer to assembly location. The fluid holding tank assembled from the flat elements is light-weight. It can have a stiffness and strength which can hold e.g. a solid-liquid slurry with maximum specific weight of 1,85 kg/dm³. The fluid holding tank can be used as a tank of a froth flotation machine, as a tank of a mixing reactor, as a liquid-liquid solvent ex^¬ traction tank and/or as a fluid storage tank. In one embodiment of the fluid holding tank, the truss core comprises a plurality of V-shaped cross profiles, said V-shaped cross profiles being arranged in paral- lei and spaced apart relation to each other along the length of the frame and transversally in relation to a longitudinal direction of the frame.

In one embodiment of the fluid holding tank, each V- shaped cross profile has a general shape of a V in which free ends of V-legs have a continuous flat first flange portion laser welded with at least one continu^¬ ous welding seam to one of the sheet metal plates, and a continuous flat second flange portion at the meeting point of the V-legs of the V-shaped cross profile, said second flange portion being laser welded with at least one continuous welding seam to another of the sheet metal plates. In one embodiment of the fluid holding tank, the tank has exterior dimensions and comprises corner fittings and conforms to intermodal freight shipping container standards, said corner fittings being attached to each of the eight corners of the tank. Therefore, the tank provides cost-effective shipping container standard compatible transportability and stacking capability. At the site of use the tank can be placed on four pil^¬ lars having container lashing fittings which can be connected to the corner fittings of the tank, and thus it does not need to have a continuous foundation base.

In one embodiment of the fluid holding tank, the tank conforms to standard ISO 668 Series 1 "Freight con^¬ tainers - Classification, dimensions and ratings"; and that the corner fittings conform to standard ISO 1161 Series 1 "Freight containers - Corner fittings - spec^¬ ification" . In one embodiment of the fluid holding tank, the tank has dimensions of a 40 ft. high-cube intermodal ship^¬ ping container.

In one embodiment of the fluid holding tank, the floor element has a floor frame comprising two horizontal side beams and two horizontal end beams, which are fixedly connected to the ends of the side beams, to form said rectangular floor frame, each of the beams being a rectangular hollow section beam.

In one embodiment of the fluid holding tank, the floor frame further comprises a plurality of cross members extending transversally and spaced apart between the side beams along the length of the floor frame, the ends of the cross members being fixedly connected to said side beams for forming a ladder frame structure. In one embodiment of the fluid holding tank, the side wall element has a sidewall frame comprising a hori^¬ zontal lower sidewall beam, which is welded along its length on the horizontal side beam of the floor frame, a horizontal upper sidewall beam, and two vertical corner pillar beams which are fixedly connected to the ends of the lower sidewall beam and the upper sidewall beam to form said rectangular sidewall frame.

In one embodiment of the fluid holding tank, the lower sidewall beam is a U-profile beam and the upper side- wall beam and the corner pillar beams are rectangular hollow section beams.

In one embodiment of the fluid holding tank, the upper sidewall beams of the side wall elements are bound to^¬ gether by upper crosswise beams arranged in parallel and spaced apart with each other along the length of the upper sidewall beams and extending transversally in relation to the upper sidewall beams, the ends of said upper crosswise beams being fixedly connected to the upper sidewall beams.

In one embodiment of the fluid holding tank, the end wall element has an end wall frame comprising a hori^¬ zontal lower endwall beam assembly, which is welded along its length on the horizontal end beam of the floor frame, two vertical corner post beams which are fixedly connected to the ends of the lower endwall beam assembly and are welded along their length to the vertical corner pillar beams of the side wall frames, and a horizontal upper endwall beam extending between and being fixedly connected to the upper ends of the vertical corner post beams.

In one embodiment of the fluid holding tank, the lower endwall lower beam assembly comprises a first beam which is rectangular hollow section beam, having a lower wall and an upper wall, a second beam which is a U-profile beam welded along its length be^¬ low the first beam on the lower wall of the first beam, and a third beam which is a U-profile beam weld- ed along its length above the first beam on the upper wall of the first beam.

In one embodiment of the fluid holding tank, in the sandwich structures of the floor element, the side wall elements and the end wall elements, the first sheet metal plate is an outer plate facing outwards in relation to the inner space of the tank, said first sheet metal plate having a thickness which is 1,5 mm; the second first metal plate is an inner plate facing towards the inner space of the tank, said second sheet metal plate having a thickness which is 2,5 mm; and the sheet metal of the V-shaped cross profiles have a thickness 1,5 - 2,5 mm.

In one embodiment of the fluid holding tank, the sand- wich structure of the floor element has a total thick^¬ ness which is 154 mm.

In one embodiment of the fluid holding tank, the sand^¬ wich structure of the side wall elements has a total thickness which is 104 mm.

In one embodiment of the fluid holding tank, the sand^¬ wich structure of the end wall elements has a total thickness which is 104 mm.

In one embodiment of the fluid holding tank, the tank is a tank of a froth flotation machine, a tank of a mixing reactor, a liquid-liquid solvent extraction tank or a storage tank.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to pro^¬ vide a further understanding of the invention and con- stitute a part of this specification, illustrate em^¬ bodiments of the invention and together with the de^¬ scription help to explain the principles of the inven^¬ tion. In the drawings: Figure 1 is an axonometric view of the fluid holding tank according to one embodiment of the present inven^¬ tion, the tank being seen obliquely from above,

Figure 2 is an axonometric view of the fluid holding tank of Figure 1, the tank being seen obliquely from below, Figure 3 shows as axonometric an view the floor ele^¬ ment, two side wall elements, and two end wall ele^¬ ments of the embodiment of Figure 1, separately, Figure 4 shows a floor frame of the floor element of Figure 3,

Figure 5 shows a sidewall frame of the side wall ele^¬ ment of Figure 3,

Figure 6 shows an endwall frame of the end wall ele^¬ ment of Figure 3,

Figure 7 is a longitudinal cross-section VII-VII of the floor element of Figure 3,

Figure 8 is a longitudinal cross-section VIII-VIII of the side wall element of Figure 3, Figure 9 is a longitudinal cross-section IX-IX of the end wall element of Figure 3,

Figure 10 is a magnification of the detail A from Fig^¬ ure 7, 8 or 9.

Figure 11 is a cross section XI-XI of Figure 2 showing a joint between the floor element and the side wall element , Figure 12 is a cross section XII-XII of Figure 2 show^¬ ing a joint between the end wall element and the side wall element, and

Figure 13 is a cross section XIII-XIII of Figure 2 showing a joint between the end wall element and the floor element. DETAILED DESCRIPTION OF THE INVENTION

Figures 1 and 2 show a fluid holding tank 1 for storage and/or handling of fluid, e.g. liquid or slurry containing solids in liquid, having a shape of a rec- tangular parallelepiped box. The tank 1 has exterior dimensions and comprises corner fittings 19 that con^¬ form to intermodal freight shipping container stand^¬ ards. The corner fittings 19 are attached to each of the eight corners of the tank 1. The tank 1 conforms to standard ISO 668 Series 1 "Freight containers

Classification, dimensions and ratings". The corner fittings 19 conform to standard ISO 1161 Series 1 "Freight containers - Corner fittings - specifica^¬ tion". In the shown example the tank 1 has dimensions of a 40 ft. high-cube intermodal shipping container. The tank 1 can easily be stored, stacked, handled and transported as normal freight by normal transport equipment, such as trucks, trailers and container ships which are capable of handling and transporting shipping container standard compatible intermodal freight container units.

The tank 1 has many possible uses in the hydrometal- lurgical industry: the tank 1 may be a tank of a froth flotation machine, a tank of a mixing reactor, a liquid-liquid solvent extraction tank and/or a liquid storage tank.

The rectangular tank 1 comprises a horizontal floor 2, two vertical side walls 3, 4, and two vertical end walls 5, 6 which together define an inner space 7 to receive the fluid. In practice, the tank 1 can also have an inner lining (not shown) that provides for fluid tightness and protection from chemical and/or physical stresses caused by the fluid material. As shown in Figure 3, the floor 2, the side walls 3, 4 and the end walls 5, 6 are formed of individually pre^¬ fabricated rigid and flat floor element 2E, two side wall elements 3E, 4E and to end wall elements 5E, 6E, respectively, which are fixedly connected to each oth^¬ er by welds to form said fluid holding tank 1. Preferably, the two side wall elements 3E and 4E are identi^¬ cal and constructed from identical parts comprising standard metal profiles and plate parts. Also the end wall elements 5E and 6E are preferably identical and constructed from identical parts comprising standard metal profiles and plate parts.

With reference to Figures 3 to 10, the floor element 2E comprises a rectangular frame 8 (see Figure 4) made of metal beams, the side wall elements 3E and 4E com^¬ prise a rectangular sidewall frame 9 (see Figure 5) made of metal beams, and the end wall elements 5E and 6E comprise a rectangular endwall frame 10 (see Figure 6) made of metal beams. As shown in Figure 7, a metal sandwich structure 13 is attached inside the floor frame 8. As shown in Figure 8, a metal sandwich struc^¬ ture 13 is attached inside the sidewall frames 3E, 4E . As shown in Figure 8, a metal sandwich structure 13 is attached inside the endwall frames 5E, 6E.

With reference to Figures 7 to 10, the sandwich struc^¬ ture 13 comprises a first sheet metal plate 14 having a periphery which is laser welded to the first side 11 of the frame 8, 9, 10. Further, the sandwich structure 13 comprises a second sheet metal plate 15 having a periphery which is laser welded to the second side 12 of the frame 8, 9, 10. Further, the sandwich structure 13 comprises a truss core TC sandwiched between the first and second sheet metal plates 14 and 15. The truss core comprises cross profiles 16 made of sheet metal. The cross profiles 16 are laser welded to the first and second sheet metal plates 14 and 15.

As can be seen in Figures 7 to 9 and particularly in Figure 10, the truss core TC comprises a plurality of V-shaped cross profiles 16. The V-shaped cross pro^¬ files are arranged in parallel and spaced apart rela^¬ tion to each other along the length of each frame 8, 9, 10 and transversally in relation to a longitudinal direction of the frame 8, 9, 10. Each V-shaped cross profile 16 has a general shape of a V. In the shown embodiments, see Figure 10, the V-angle a is about 60°. As also can be seen in Figure 10, the free ends of V-legs have continuous flat first flange portions 17. The flat flange portions 17 are laser welded with a continuous welding seam to the sheet metal plate 14. At the meeting point of the V-legs of the V-shaped cross profile 16 there is a continuous flat second flange portion 18 which is laser welded with a contin- uous welding seam to the second sheet metal plate 15.

Figure 4 shows the floor frame 8 of the floor element 2E. The floor frame 8 comprises two horizontal side beams 20 and two horizontal end beams 21, which are manually welded to the ends of the side beams 20 to form the rectangular floor frame 8. The side beams 20 and the end beams 21 are preferably rectangular hollow section beams. The floor frame 8 further comprises a plurality of cross members 22 extending transversally and spaced apart between the side beams 20 along the length of the floor frame 8, the ends of the cross members 22 are manually welded the side beams 20 for forming a ladder frame structure. In the shown embodi^¬ ment, the tank 1 being flotation tank the floor frame 8 is equipped with four support platforms for stators. The support platforms are connected between pairs of cross members 22. Figure 5 shows the side wall frame 9 of the side wall element 3E (or 4E) . The sidewall frame 9 comprises a horizontal lower sidewall beam 23, a horizontal upper sidewall beam 24, and two vertical corner pillar beams 25 which are fixedly connected to the ends of the low^¬ er sidewall beam and the upper sidewall beam to form the rectangular sidewall frame 9. As shown in Figures 2 and 11, the lower sidewall beam 23 is welded along its length on the horizontal side beam 20 of the floor frame 8. The lower sidewall beam 23 is a U-profile beam and the upper sidewall beam 24 and the corner pillar beams 25 are rectangular hollow section beams. In the tank 1, as shown in Figure 1, the upper side- wall beams 23 of the side wall elements 3E, 4E are bound together by upper crosswise beams 26 arranged in parallel and spaced apart with each other along the length of the upper sidewall beams 23 and extending transversally in relation to the upper sidewall beams 23. The ends of the upper crosswise beams 26 are manu^¬ ally welded to the upper sidewall beams 23.

Figure 6 shows the end wall frame 10 of the end wall element 5E (or 6E) . As also shown in Figures 9 and 13 the end wall frame 10 comprises a horizontal lower endwall beam assembly 27, which is welded along its length on the horizontal end beam 21 of the floor frame 8. Two vertical corner post beams 28 are manual- ly to the ends of the lower endwall beam assembly 27. A horizontal upper endwall beam 29 extends between the upper ends of the vertical corner post beams 28 and is welded thereto. As shown in Figures 2 and 12, in the tank 1, the vertical corner post beams 28 are welded along their length to the vertical corner pillar beams 25 of the side wall elements 4E (and 3E, respective^¬ ly) . As shown in Figures 9 and 13, the lower endwall lower beam assembly 27 comprises a first beam 30 which is rectangular hollow section beam, having a lower wall 31 and an upper wall 32, a second beam 33 which is a U-profile beam welded along its length below the first beam 30 on the lower wall 31 of the first beam 30, and a third beam 34 which is a U-profile beam welded along its length above the first beam 30 on the upper wall 31 of the first beam 30. In the sandwich structures 13 of the floor element 2E, the side wall elements 3E, 4E and the end wall ele^¬ ments 5E, 6E, the first sheet metal plate 14 is an outer plate facing outwards in relation to the inner space 7 of the tank 1 whereby the first sheet metal plate has a thickness which is 1,5 mm. The second first metal plate 15 is an inner plate facing towards the inner space 7 of the tank 1 whereby the second sheet metal plate 15 has a thickness which is 2,5 mm. The sheet metal of the cross profiles 16 has a thick- ness 1,5 - 2,5 mm.

The sandwich structure 13 of the floor element 2E has a thickness S_F which is 154 mm. The sandwich structure 13 of the side wall elements 3E, 4E has a thickness S_Sw which is 104 mm. The sandwich structure 13 of the end wall elements 5E, 6E has a thickness S_EW which is 104 mm.

In a special embodiment, wherein the tank 1 has dimen- sions of a 40 ft. high-cube intermodal shipping con^¬ tainer :

- The length of the floor element 2E has a length 12.192 m, width 2.438 m and thickness 0,154 m. The side beams 21 have a length of 11836 mm and are rectangular hollow sections RHS 150x150x8. The end beams 21 have a length 2138 mm and are rectangular hollow sections RHS 300x150x6. The truss core TC of the floor element 2E consists of 27 pieces of V-shaped cross profiles 16 having a sheet metal thickness 2.0 mm.

- The side wall element 3E, 4E has a length 12.192 m, height 2.709 m and thickness 0.104 m. The lower sidewall beam 23 is a U-profile beam U 100x50x5 with a length 11592 mm. The upper sidewall beam 24 is a rectangular hollow section beam RHS 150x100x6 with a length 11836 mm. The corner pillar beams 25 are rec- tangular hollow section beams RHS 300x100x6 with a length 2559 mm. The truss core TC of the side wall el^¬ ements consists of 33 pieces of V-shaped cross pro^¬ files 16 with a sheet metal thickness 2.0 mm.

- The end wall element 5E, 6E has a width 2.214 m, height 2.709 mm and thickness 0.104 m. The upper endwall beam 29 is a U-profile beam U100x50x5 having a length 2114 mm. The corner post beams 28 are U-profile beams 100x50x5 having a length 2159 mm. In the lower endwall assembly 27, the first beam 30 is a rectangular hollow section beam RHS 300x100x6 having a length 2214 mm. The second beam 33 and the third beam 34 are U-profile beams 100x50x5 having lengths of 2214 mm and 2114 mm, respectively. The truss core TC of the end all elements consists of 7 pieces of V-shaped cross profiles 16 with a sheet metal thickness 2.0 mm.

It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The in- vention and its embodiments are thus not limited to the examples described above, instead they may vary within the scope of the claims.

Claims

1. A fluid holding tank (1) for storage and/or handling of fluid, e.g. liquid or slurry, having a shape of a rectangular parallelepiped box and comprising a horizontal floor (2), two vertical side walls (3, 4), and two vertical end walls (5, 6) defining an inner space (7) to receive said fluid, characteri z ed in that the floor (2), the side walls (3, 4) and the end walls (5, 6) are formed of individually pre- fabricated rigid and flat floor element (2E), side wall elements (3E, 4E) and end wall elements (5E, 6E) , respectively, which are fixedly connected to each oth^¬ er by welds to form said fluid holding tank (1), each of said floor, side wall and end wall elements comprising

- a rectangular frame (8, 9, 10) made of met^¬ al beams, said frame having a first side (11) and a second side (12); and

- a metal truss core sandwich structure (13) comprising

-- a first sheet metal plate (14) having a periphery which is laser welded to the first side (11) of the frame (8, 9, 10) ,

-- a second sheet metal plate (15) having a periphery which is laser welded to the second side (12) of the frame, and

-- a truss core (TC) sandwiched between the first and second sheet metal plates, said truss core comprising cross profiles (16) made of sheet metal, said cross profiles being laser welded to the first and second sheet metal plates.

2. The tank according to claim 1, character i zed in that the truss core (TC) comprises a plurality of V-shaped cross profiles (16), said V-shaped cross pro^¬ files being arranged in parallel and spaced apart re^¬ lation to each other along the length of the frame (8, 9, 10) and transversally in relation to a longitudinal direction of the frame.

3. The tank according to claim 2, character i zed in that each V-shaped cross profile (16) has a general shape of a V in which free ends of V-legs have a con^¬ tinuous flat first flange portion (17) laser welded with at least one continuous welding seam to one of the sheet metal plates (14 or 15), and a continuous flat second flange portion (18) at the meeting point of the V-legs of the V-shaped cross profile, said sec^¬ ond flange portion (18) being laser welded with at least one continuous welding seam to another of the sheet metal plates (15 or 14) .

4. The tank according to any one of the claims 1 to 3, character i zed in that the tank (1) has exterior dimensions and comprises corner fittings (19) and con^¬ forms to intermodal freight shipping container stand- ards, said corner fittings (19) being attached to each of the eight corners of the tank (1) .

5. The tank according to claim 4, character i zed in that the tank (1) conforms to standard ISO 668 Se- ries 1 "Freight containers - Classification, dimen^¬ sions and ratings"; and that the corner fittings (19) conform to standard ISO 1161 Series 1 "Freight con^¬ tainers - Corner fittings - specification".

6. The tank according to any one of the claims 1 to 5, character i zed in that the tank (1) has dimen^¬ sions of a 40 ft. high-cube intermodal shipping con^¬ tainer .

7. The tank according to any one of the claims 1 to 6, character i zed in that the floor element (2E) has a floor frame (8) comprising two horizontal side beams (20) and two horizontal end beams (21), which are fixedly connected to the ends of the side beams, to form said rectangular floor frame, and/or that each of the beams is a rectangular hollow section beam.

8. The tank according to claim 7, character i zed in that the floor frame (8) further comprises a plu^¬ rality of cross members (22) extending transversally and spaced apart between the side beams (20) along the length of the floor frame, the ends of the cross mem^¬ bers (22) being fixedly connected to said side beams (20) for forming a ladder frame structure.

9. The tank according to claim 7 or 8, character- i z e d in that the side wall element (3E, 4E) has a sidewall frame (9) comprising a horizontal lower side- wall beam (23), which is welded along its length on the horizontal side beam (20) of the floor frame (8), a horizontal upper sidewall beam (24), and two verti- cal corner pillar beams (25) which are fixedly con^¬ nected to the ends of the lower sidewall beam and the upper sidewall beam to form said rectangular sidewall frame .

10. The tank according to claim 9, characteri z ed in that the lower sidewall beam (23) is a U- profile beam and the upper sidewall beam (24) and the corner pillar beams (25) are rectangular hollow section beams.

11. The tank according to claim 9 or 10, characteri z ed in that the upper sidewall beams (23) of the side wall elements (3E, 4E) are bound together by upper crosswise beams (26) arranged in parallel and spaced apart with each other along the length of the upper sidewall beams and extending transversally in relation to the upper sidewall beams, the ends of said upper crosswise beams being fixedly connected to the upper sidewall beams.

12. The tank according to any one of the claims 7 to 11, characteri zed in that the end wall element

(5E, 6E) has an end wall frame (10) comprising a horizontal lower endwall beam assembly (27), which is welded along its length on the horizontal end beam (21) of the floor frame (8), two vertical corner post beams (28) which are fixedly connected to the ends of the lower endwall beam assembly (27) and are welded along their length to the vertical corner pillar beams (25) of the side wall frames (9), and a horizontal up^¬ per endwall beam (29) extending between and being fix- edly connected to the upper ends of the vertical cor^¬ ner post beams (28) .

13. The tank according to claim 12, characteri z ed in that the lower endwall lower beam assembly (27) comprises a first beam (30) which is rectangular hollow section beam, having a lower wall (31) and an upper wall (32), a second beam (33) which is a U- profile beam welded along its length below the first beam on the lower wall (31) of the first beam (30), and a third beam (34) which is a U-profile beam welded along its length above the first beam (30) on the up^¬ per wall (31) of the first beam (30) .

14. The tank according to any one of the claims 1 to 13, character i z ed in that in the sandwich structures (13) of the floor element (2E), the side wall elements (3E, 4E) and the end wall elements (5E, 6E) , the first sheet metal plate (14) is an outer plate facing outwards in relation to the inner space (7) of the tank (1), said first sheet metal plate hav^¬ ing a thickness which is 1,5 mm; that the second first metal plate (15) is an inner plate facing towards the inner space of the tank, said second sheet metal plate (15) having a thickness which is 2,5 mm; and that the sheet metal of the cross profiles (16) have a thick^¬ ness 1,5 - 2,5 mm.

15. The tank according to claim 14, characteri z ed in that the sandwich structure (13) of the floor element (2E) has a thickness (S_F) which is 154 mm.

16. The tank according to claim 14, characteri z ed in that the sandwich structure (13) of the side wall elements (3E, 4E) has a thickness (S_Sw) which is 104 mm .

17. The tank according to claim 14, characteri z ed in that the sandwich structure (13) of the end wall elements (5E, 6E) has a thickness (S_EW) which is 104 mm.

18. The tank according to any one of the claims 1 to 17, characteri zed in that the tank (1) is a tank of a froth flotation machine, a tank of a mixing reactor, a liquid-liquid solvent extraction tank or a liquid storage tank.