WO2006046873A1

WO2006046873A1 - Tank for storage of lng or other fluids

Info

Publication number: WO2006046873A1
Application number: PCT/NO2005/000403
Authority: WO
Inventors: Otto Skovholt; Bjørn SJETNAN; Trond Johansen; Terje Myrhaug; Steinar Johansen
Original assignee: CONCRYO AS; NCC CONSTRUCTION AS
Current assignee: CONCRYO AS; NCC CONSTRUCTION AS
Priority date: 2004-10-25
Filing date: 2005-10-25
Publication date: 2006-05-04
Anticipated expiration: 2007-04-25
Also published as: WO2006046874A1; NO328739B1; WO2006062411A1; NO20044586D0; NO20044586L; WO2006046872A1

Abstract

Tank (1) for storage or treatment of fluids, comprising a bottom, a wall, and a gas tight lining arranged on the wall, distinguished in that the gas tight lining is made from bands of thin sheets arranged side-by-side such that the wall is covered, adjacent bands being held together with a against the underlayer tightly fastened clamping moulding, and the bands being sealingly joined by seam welds to the clamping moulding. Method for arrangement of the gas tight lining.

Description

TANKFORSTORAGEOFLNGOROTHERFLUIDS

Field of invention

The present invention relates to storage of LNG, i.e. liquefied natural gas, and other cryogenic liquids. More particularly, the invention relates to large tanks for storage of LNG or other cryogenic fluids, and gas tight barriers in such tanks.

Prior art and background of the invention

Storage of LNG requires tanks withstanding operating temperatures lower than -161 ⁰C, which is the boiling point at atmospheric pressure of methane, the main component of LNG. A normal operating temperature of an LNG tank is -163 ⁰C.

Today, LNG is usually stored in double-walled tanks at atmospheric pressure. The inner tank serves to keep the LNG content enclosed, whereas the outer tank keeps the insulating material in position, protects the inner tank and the insulation against external influence, and provides increased security in case of leakage in the inner tank. For small to medium size tanks it is not unusual to use pressure tanks or isolation provided by arranging a vacuum between the tank walls. Such arrangements are inadequate for large tanks because the walls must be made unduly solid. In order to limit the wall thickness a circular cross section of the tank is the most usual. The outer tank is usually constructed to keep LNG or gas enclosed if a leakage should occur in the inner tank. The tanks of LNG import and export terminals may have sizes of up to about 160,000 m³, or even 200,000 m³, which may necessitate a tank diameter of about 70 m and a tank height of about 60 m. Large tanks are usually built from concrete, but concrete is not accepted to be sufficiently gas tight, hence, it is required with one or more barriers or linings that are tight with respect to the media to which the tank wall is exposed. In the outer tank a gas tight lining is usually built on the inside of the wall. The lower part of the gas tight lining, typically the lower 5 m, must be tight with respect to LNG that can leak out from the inner tank by earth quake or other extreme situations.

In patent publication NO 314814 a tank for storage of cryogenic fluids is described. The tank according to NO 314814 is provided with a separate outer tank (16) that can take up leakages. The time and working effort for construction are significant, such that the costs are high. Preparing the fluid tight barriers is very laborious, and represents a problem there is a demand to reduce. The construction period for a tank according to NO 314814, with a volume of 160 000 m³, typically exceeds 36 months.

On Melkeøya outside Hammerfest, Norway, a LNG-plant is under construction, comprising inter alia 2 LNG-tanks made of concrete and having a gas tight lining. A gas tight lining is arranged on the inside of an outer tank, for each of said tanks. In the outer concrete wall, towards the inside, steel ribs have been imbedded, so called strips, to which the gas tight lining shall be welded sealingly. The tank walls are slip formed, and it has proved that the steel ribs do not maintain their position in the surface of the walls, but are imbedded typically 5-15 mm inside the surface. The concrete surface must be furbished to expose the steel ribs, by surface grinding around each steel rib in a width of 200-300 mm. The result is nevertheless a quite uneven underlayer. On the inside of the outer concrete wall, towards the steel ribs, plates of typical 5 mm thickness, 1,5 m width and 6 m height are welded. The plates must be lifted and held in position during welding, which work has proved to be very comprehensive. Severe problems have been revealed with curving and twisting as a result of weld induced crimping, which problems increases both with the size of the plates because mal adjustments accumulate, and with decreasing thickness of the plates because of reduced stiffness. Therefore the thickness of the plates can hardly be reduced, and likewise the size of the plates can hardly be increased. The welding is undertaken by manual metal arc welding, with initial point welding and subsequent seam welding. Welding of the gas tight lining has been a significant part of the total welding work. To illustrate the scope of the work, it can be mentioned that about 150 welders have been in activity for about 24 months.

A demand exists for a tank in concrete for storage of LNG or other fluids, with beneficial properties compared to what is mentioned above, and which allows a more preferable method for building a gas tight lining.

Summary of the invention

The above-mentioned demand is met by providing a tank for storage of LNG or other fluids, comprising an inner tank having a bottom, an inner side wall extending upwards to an optional insulating roof, an outer tank having a bottom, an outer side wall extending upwards around the inner tank to a level above said inner tank, a gas tight lining on the outer side wall, and an outer roof construction above said inner tank, insulating material between said inner tank and said outer tank, and at least one feedthrough for filling and emptying, distinguished in that the gas tight lining on the side wall of the outer tank is made from bands of thin sheets arranged from the upper end of the wall and down to the lower end of the wall, adjacent bands being held together with a against the underlayer tightly fastened clamping moulding, and the bands being sealingly joined by seam welds to the clamping moulding.

For a concrete tank for cryogenic fluids the gas tight lining is preferably arranged on the inner side wall of the outer tank. The clamping mouldings are preferably fastened by use of anchor bolts (threaded bolts) extending out from the outer side wall, overlapping over adjacent bands of thin sheets. The gas tight lining is preferably prepared from low temperature ductile steel thin sheet of thickness about 1 mm. Likewise, clamping mouldings and anchor bolts are preferably prepared from low temperature ductile steel. The anchor bolts are preferably fastened to a sleeve imbedded into the wall, are glued to the wall or are moulded to the wall by mortar.

With the present invention also a more general tank for storage or treatment of fluids is provided, comprising a bottom, a wall and a gas tight lining arranged on the wall, distinguished that the gas tight lining is made from bands of thin sheets arranged side-by- side such that the wall is covered, adjacent bands being held together with a against the underlayer tightly fastened clamping moulding, and the bands being sealingly joined by seam welds to the clamping moulding.

The invention also provides a method for arranging a gas tight lining onto or into a tank for storage or treatment of fluids, distinguished in that bands of thin sheets are arranged side-by-side on the surface where the lining shall be arranged; clamping mouldings are placed overlapping over adjacent bands; clamping mouldings and underlying bands are fastened tightly to the surface; and the edges of the clamping mouldings are sealingly seam welded to the underlying bands.

A preferable embodiment of the method comprises that: anchor bolts are arranged to extend out from the surface to be lined with the gas tight lining, bands of thin sheets are arranged side-by-side such that anchor bolts extend out between the bands, clamping moulds are placed overlapping over adjacent bands and with anchor bolts extending out through holes provided in the clamping mouldings, the clamping mouldings and underlying bands are fastened tightly to the surface by tightening nuts on the anchor bolts, optionally with a sealing washer placed under each nut, and the edges of clamping mouldings are seam welded sealingly to the underlying band with an automated welding tractor.

The anchor bolts are preferably fastened in advance into imbedded sleeves, are fixed by glue or fixed by moulding by mortar.

The welding tractor is preferably fastened two-sided with fastening means to the anchor bolts, the fastening means comprising rails that can be arranged to cover the length of the bands, along which rails the welding tractor can move. The welding tractor further preferably comprises at least one rolling drum or movable jig keeping the parts that are welded fixedly positioned until the weld has solidified, preferably until the weld has cooled down. The welding tractor is preferably designed for simultaneously welding of two welding seams, either along the longitudinal edges of one band or on each side of a clamping moulding.

With the tanks and the method according to the invention, the costs and working effort to build the gas tight lining can be significantly reduced. Drawings

The invention is illustrated by five drawings, of which: Figure 1 illustrates a tank according to the invention, in half section, Figure 2 illustrates the transition between inner tank, roof and outer tank, for the tank of Figure 1,

Figure 3 illustrates the transition between the side wall and bottom of the tank, for the tank of Figure 1,

Figure 4 is a further illustration of the gas tight lining arranged in a tank according to the invention, and Figure 5 is a further illustration of the gas tight lining arranged in a tank according to the invention.

Detailed description

Reference is made to Figure 1, illustrating a tank 1 according to the invention for storage of LNG or other cryogenic fluids. The tank 1 comprises an inner tank 2 having a bottom 2a, inner side walls 2b extending upwards and consisting of an inner concrete wall 2c, an intermediate low temperature ductile tight metal lining 2d, an outer wall 2e of prestressed concrete, and an insulating roof 2f.

The tank 1 further comprises an outer tank 3 having a bottom 3a, an outer side wall 3b extending upwards around the inner tank 2 to a level above said inner tank, an outer gas tight steel lining 3 c on the inner side of the outer wall, and an outer roof construction 3d above the inner tank. An insulating material 4 is arranged between the inner tank 2 and the outer tank 3. Also, at least one feedthrough 5 is arranged for filling and draining, which feedthrough is not shown in detail, but consists of inlet and outlet pipes, pumps and cables. Means for access of personnel are provided at the feedthrough locality.

The side wall 3b of the outer tank 3 is formed in concrete as a homogenous unit, preferably without joints, and with a sufficient ring strength at an upper end, so that the outer roof construction 3d can be arranged directly on the outer side wall. The side wall 3b of the outer tank 3 is preferably formed with an enlarged wall thickness at the upper end, and preferably even at a lower end, so as to achieve a sufficient ring rigidity to resist expected impact in case of an earth quake.

The enlarged wall thickness, with the resulting increased ring rigidity and ring strength at the upper end and the lower end of the side wall 3b of the outer tank 3, is clearly seen in Figure 1. Reference is made, however, to Figure 2, from which it appears more clearly how the upper end of the outer side wall 3d has been formed with an enlarged wall thickness, for the outer wall construction 3d to be arranged directly on the outer side wall. Similarly, enlarged wall thickness and increased ring rigidity is also found at the lower end of the side wall 3b. The side walls are extending upwards from the periphery of the bottom parts, typically vertically, but they may also be arranged inclined. The conception of arranging the outer wall construction directly on the outer side wall implies that additional construction arrangements are not required for building the outer roof directly on the outer side wall. In the tank of the present invention side walls of concrete 2c, 2e, 3b are preferably slip formed. Slip forming is advantageous because the casting time can be considerably reduced as compared to casting using climbing formwork.

The tank of the present invention preferably comprises at least one earthquake support 6 between the outer and the inner side wall. Earthquake supports are illustrated in Figures 1, 2, and 3.

Reference is made to Figure 3, wherein a section of the lower part of the tank is shown, at the transition between the bottom and the side walls. More precisely, the bottom 2a of the inner tank and the bottom 3 a of the outer tank are shown, which are both made of a low temperature ductile metal. It is also shown how the space between the bottom layers is stratified with two layers of isolating blocks 7a, 7b, with small blocks, preferably made of isolating concrete, arranged in an upper layer 7a, and larger blocks, preferably made of isolating concrete, being arranged in a lower layer 7b, with overlaying, intermediate and underlying slip layers 8, preferably slip layers of low friction plywood. The purpose of said advantageous construction is to allow temperature induced expansion and compression, without stress formation and cracking. Furthermore, a support ring 9 is shown, and also a bearing ring 10, said bearing ring 10 being arranged below the inner side wall and being made of a pressure resistant perlite concrete. At detail B, it is shown how the bottom of the outer tank and the gas tight lining in the form of a low temperature ductile metal lining on the inner side of the side wall of the outer tank is shaped with a rounded transition between said elements and a yielding material 3g, for instance mineral wool, is arranged at the inside of said transition, the fastening of the low temperature ductile metal against the support near said transition is slip able, and the transition is situated mainly on the outside of the isolation on the relatively hot side of the tank wall, so said transition can resist strain without cracking. In case of leakage of LNG to the outer tank, the transition will contract against the yielding material, whereby excessive stress build-up is avoided.

On the Figures 1-3 the gas tight lining is not illustrated in detail. Therefore, reference is made to the Figures 4 and 5 where the gas tight lining is illustrated further. The Figures 4 and 5 illustrate in section bands of thin sheets, clamping moulding, anchor bolts, fixing of anchor bolts and nuts or similar for fastening. The anchor bolts and means for fastening thereof are however sketched. The anchor bolts are typical in form of threaded bolts that are screwed into dedicated fixings in the wall.

On Figure 4 metal plates 3 c constituting the gas tight lining are illustrated. Further, an anchor bolt 3e is illustrated, a clamping moulding 3f, an imbedded sleeve 3g, a nut 3i for fastening of the clamping moulding on the anchor bolt, and a washer 3j for arranging between the nut and the clamping moulding. Seam welds 3k between the clamping moulding and bands of plates 3 c are also illustrated. The imbedded sleeve 3g illustrated on Figure 4 is moulded into the concrete wall 3b during forming thereof, either by slip forming or with a climbing formwork. The anchor bolt 3e is fastened into the imbedded sleeve. Bands of thin metal sheets, i.e. thin sheets preferably arriving as a reel covering the full height of the wall in one length, are arranged adjacent towards the anchor bolts, the anchor bolts arranged in line such that bands can be arranged on each side of the anchor bolts. The bands of thin sheet can preferably be fastened with a tape or glue, preferably double-sided tape, for example of type VHB 1.1 x 19 mm from 3M. Then the clamping mouldings are tread over anchor bolts and thin sheet bands. A nut is put on the anchor bolts and tightened such that the thin sheets and clamping mouldings be tightly fastened to the concrete wall. Preferably a washer 3j can be arranged to ensure tightness for gas, however, the seal can be provided directly between the nut and the clamping moulding.

Figure 5 illustrates a similar embodiment, different by instead of the imbedded sleeve 3g the anchor bolts are either arranged in a glued fixing 3h or in a fixing of moulded mortar. The glue fixing of anchor bolts can because of vitrification of the glue be inappropriate in areas that can be exposed to low temperatures, such as the lower 5 meters of the wall of a LNG tank.

As illustrated on Figure 5 the anchor bolts preferably extend beyond the gas tight lining. This will also be the situation on Figure 4 after tightening. The advantage thereby is that the anchor bolts can be used for fastening of welding equipment, working platforms, lifting devices etc. Preferably a welding tractor is used that is fastened two- sided with fastening means to the anchor bolts, which fastening means comprise rails that can be arranged to cover the length of the bands, along which rails the welding tractor can move. The welding tractor preferably comprises at least one rolling drum or moveable jig keeping the parts that are welded fixedly in position until the weld has solidified. Appropriate welding equipment can be provided from the company ESAB. For parts of the gas tight lining that never can be exposed to cryogenic temperatures, or for tanks that are not to store cryogenic fluids, glue fixation of the anchor bolts can be used, and materials that are not low temperature resistant. Rolling out of bands, fastening with clamping moulding and seam welding, can either be undertaken simultaneously, for example with a lifting device with working platform and welding equipment that can be moved up or down, or the work operations can be undertaken in separated steps.

Claims

1. Tank (1) for storage of LNG or other fluids, comprising an inner tank (2) having a bottom (2a), an inner side wall (2b) extending upwards to an optional insulating roof (2f), an outer tank (3) having a bottom (3a), an outer side wall (3b) extending upwards around the inner tank to a level above said inner tank, a gas tight lining (3 c) on the outer side wall, and an outer roof construction (3d) above said inner tank, insulating material (4) between said inner tank and said outer tank, and at least one feedthrough (5) for filling and emptying, characterized in that the gas tight lining (3 c) on the side wall of the outer tank is made from bands of thin sheets arranged from the upper end of the wall and down to the lower end of the wall, adjacent bands being held together with a against the underlay er tightly fastened clamping moulding, and the bands being sealingly joined by seam welds to the clamping moulding.

2. Tank (1) for storage or treatment of fluids, comprising a bottom, a wall, and a gas tight lining arranged on the wall, characterized in that the gas tight lining is made from bands of thin sheet arranged side-by-side such that the wall is covered, adjacent bands being held together with a against the underlayer tightly fastened clamping moulding, and the bands being sealingly joined by seam welds to the clamping moulding.

3. The tank of claim 1 or 2, characterized in that the gas tight lining (3 c) is arranged on the inner side wall of the outer tank.

4. Tank according to claim 1 or 2, characterized in that the clamping mouldings by use of anchor bolts (threaded bolts) that extend out from the outer side wall, are fastened overlapping over adjacent bands of thin sheet.

5. Tank according to claim 1 or 2, characterized in that the gas tight lining is made from low temperature ductile thin sheet of steel of thickness of about 1 mm.

6. Tank according to claim 1 or 2, characterized in that clamping mouldings and anchor bolts are made of low temperature ductile steel.

7. Tank according to claim 1 or 2, characterized in that anchor bolts either are fastened to a sleeve imbedded into the wall, are fastened with glue to the wall or are fastened to the wall by mortar.

8. Method for arranging a gas tight lining onto or into a tank (1) for storage or treatment of fluids, characterized in that bands of thin sheet are arranged side-by-side on the surface where the lining shall be provided, clamping mouldings are placed overlapping over adjacent bands, clamping mouldings and underlying bands are fastened tightly to the surface, and the edges of the clamping mouldings are seam welded sealingly to the underlying bands.

9. Method according to claim 8, characterized in that anchor bolts are arranged to extend out from the surface to be lined with the gas tight lining, bands of thin sheets are arranged side-by-side such that anchor bolts extend out between the bands, clamping mouldings are placed overlapping over adjacent bands and with anchor bolts extending out through dedicated holes in the clamping mouldings, clamping mouldings and underlying bands are fastened tightly to the surface by tightening nuts on the anchor bolts, optionally with a sealing washer placed under each nut, and the edge of clamping mouldings are seam welded sealingly to the underlying band with an automated welding tractor.

10. Method according to claim 9, characterized in that anchor bolts are fastened into imbedded sleeves, or glued or fastened by mortar.

11. Method according to claim 9, characterized in that the welding tractor is fastened two-sided with fastening means to the anchor bolts, the fastening means comprising rails that can be arranged to cover the length of the bands, along which rails the welding tractor can move.

12. Method according to claim 9, characterized in that the welding tractor comprises at least one rolling drum or moveable jig that can hold the parts that are welded together in a fixed position until the weld has solidified.

13. Method according to claim 9, characterized in that the bands of thin sheets initially are fastened to the underlayer with double-sided tape.