EA036079B1 - Box tank and method for lining a box tank - Google Patents

Abstract

The invention relates to a method for lining an inner wall (2) of a box tank (1) comprising placing a clapboard layer (5) on the inner wall (2), the clapboard layer (5) being ventilated and electrically conductive in the direction parallel to the inner wall; coating the clapboard layer (5) with a reinforcing layer (9) made of liquid fiber reinforced synthetic resin with the first viscosity, and solidifying the reinforcing layer (9); and coating the solidified reinforcing layer (9) or a sealing layer (11) arranged thereon with a top layer (10) made of a liquid material with the second viscosity substantially lower than the first viscosity, and hardening the top layer (10). The invention also relates to the box tank (1) which is lined according to the method.

Description

The technical field to which the invention relates

The invention relates to a method for lining the inner wall of a tank, in particular an underground or surface tank for storing petroleum products, solvents, acids, bases, etc. The invention also relates to a lined tank.

State of the art

Applying a protective lining to the inner wall of a tank can be used for two purposes: either to repair a leaking tank or to upgrade a single wall tank with a double wall system. In a double-walled system, pressure changes can be monitored in the gap between the two walls, which reveal a leak in one of the walls. The lining includes a spacer to form the gap, and the original inner wall of the tank forms the outer wall of the double wall system.

US Re 33,421 describes several methods for lining tanks by applying a synthetic resin coating to overlapping foil spacers that is reinforced with glass fiber strips in the overlap areas. The application of the reinforcement strips is a time-consuming process and the overall design obtained is unsatisfactory in terms of tightness, durability and testability.

Disclosure of invention

It is an object of the present invention to provide an improved lining process as well as a lined tank that overcomes the disadvantages of the prior art.

To this end, a first aspect of the invention is a method for lining the inner wall of a tank, comprising applying to the inner wall a separating layer that is both air permeable and electrically conductive in a direction parallel to the inner wall;

applying to the separating layer a reinforcing layer consisting of a liquid fiber-reinforced synthetic resin having a first viscosity and curing the reinforcing layer and applying to the cured reinforcing layer or to a sealing layer applied thereto an upper layer consisting of a liquid material having a second viscosity, significantly lower than the specified first viscosity, and hardening of the upper layer.

By layering on the pre-formed separating layer superimposed layers of curable resin with different viscosities in their liquid form at the application stage, a double-walled structure can be easily formed for modernization and repair. The high resin viscosity of the reinforcing layer ensures sufficient thickness and thus impermeability and durability, as well as strong adhesion of the inner reinforcing fibers. This minimizes the risk of fibers falling out and circulating in the air, which could result in operator injury. Secondly, the low viscosity of the upper layer ensures its thin-layer application, saving materials and at the same time with easy penetration and closing of the pores of the underlying layer. Finally, the method combines fast and safe lining application with increased durability, impermeability and practicality of the lining.

Preferably, said first viscosity is greater than 3000 mPa-s at 25 ° C, and said second viscosity is less than 3000 mPa-s at 25 ° C.

In a preferred embodiment, the top layer is electrically conductive. The electrically conductive layer, when properly grounded, can discharge static electricity when the tank comes in contact with workers, eliminating the risk of fire.

Preferably, the reinforcing layer and the topsheet are roller or spray applied, which allows full utilization of the different viscosities of the layers to achieve these effects.

According to another preferred feature of the invention, the reinforcement layer is reinforced with microfibers. This provides a highly viscous, fiber-reinforced slurry that can be applied safely and in high build. In particular, the microfibers can be composed of glass staple fibers, preferably with a length in the range of 3-6 mm, which results in a high strength of the reinforcing layer.

As mentioned above, the lining can have either a three-layer structure (release layer, reinforcement layer, top layer) or a four-layer structure (release layer, reinforcement layer, seal layer, top layer). In the latter case, the sealant layer preferably consists of a liquid synthetic resin having a third viscosity that cures before being topcoated thereon, said third viscosity being significantly higher than said first viscosity, preferably above 8000 mPa-s at 25 ° C. Due to its high viscosity, the fiber-free seal layer will be applied with sufficient thickness to protect the reinforcement layer from any corrosive media in the tank. Preferably, the chemical resistance of the containment layer to hydrocarbons is also higher compared to the reinforcement layer.

In either case, the release layer can comprise corrugated or embossed aluminum foil or sheet, both of which can provide the necessary clearance for tightness control as well as electrical conductivity for spark brush leak testing, as will be explained below.

In another embodiment, the release layer is composed of a plurality of corrugated or embossed aluminum foil films or sheets, adjacent ones overlapping to improve structural strength and electrical conductivity. Structural strength can be further improved by optionally placing a fiber-reinforced tape or strip with overlap between adjacent foil films or sheets and embedded in the reinforcing layer when the reinforcing layer is applied to the separating layer.

A second aspect of the invention is a vessel lined according to the methods described above.

Brief Description of Drawings

The invention will now be described in detail with reference to the accompanying drawings, in which: FIG. 1 is a fragmentary sectional view of a tank lined in accordance with the method of the invention;

in fig. 2 - fragment A of FIG. 1 on an enlarged scale;

in fig. 3 is an enlarged partial sectional view of another embodiment of the lining according to the invention;

in fig. 4 is an enlarged, fragmentary sectional view of another embodiment of the lining according to the invention.

FIG. 1 and 2 fragmentarily show a tank 1, for example, an underground or surface tank for storing petroleum products at a gas station or refinery. The tank 1 has an inner wall 2. The wall 2 can be made of concrete or metal and can be made in the form of a one-piece container or parts, which, for example, are welded together using seams 3.

The inner wall 2 of the tank 1 must be lined with a lining 4, which at the same time creates a double-walled system for the tank 1. For this purpose, the lining 4 contains a separating layer 5 opposite the inner wall 2. The separating layer 5 is permeable to air in a direction parallel to the inner wall 2, so that a gap 6 is formed between the separating layer 5 and the wall 2. The gap 6 can be evacuated and the pressure changes with time can be monitored in the vacuum inside it, which reveal the leakage of the liner 4 and / or wall 2, as is known in the art.

As shown in FIG. 2, the lining 4 is applied in situ to the tank 1 as follows.

First, a separating layer 5 is applied to the inner wall 2. The separating layer 5 can be composed of any material that allows air to penetrate in a direction parallel to the inner wall 2, so that the gap 6 can be evacuated from only one or more specific points on In addition, for spark control, as will be explained below, the separation layer 5 is electrically conductive in a direction parallel to the inner wall 2, so that it can only be electrically grounded at one or more specific points along the wall 2.

The separating layer 5 can, for example, be made of corrugated, corrugated or embossed polymer films or sheets, either made entirely of electrically conductive plastic or covered with an electrically conductive metal layer. Alternatively, and preferably, the release layer 5 is a corrugated or embossed aluminum foil or sheet having a plurality of ribs, protrusions or protuberances 7 opposite the wall 2 and located regularly throughout the release layer 5. The release layer 5 can be composed of a plurality of foil films or sheets that are mutually overlapping in the overlapping regions 8 (FIG. 4), as will be described below.

Secondly, a reinforcement layer 9 is applied to the release layer 5. The reinforcement layer 9 consists of a fiber-reinforced synthetic resin which is applied in liquid form to the release layer 5, preferably by roller or squeegee spreading or spraying. The reinforcement with synthetic resin fibers of the reinforcing layer 9 is achieved by embedding fibrous mats, woven or non-woven, in a liquid resin, or by impregnating the mats with such a liquid resin, or preferably by using a liquid resin suspension with microfibers such as glass or carbon staple fibers ... Glass staple fibers with a length in the range of 3-6 mm, for example 4.5 mm, are preferably used. The liquid suspension of synthetic resin and staple fibers is then rolled or sprayed onto the release layer 5, which also fills the bumps 7, as shown in FIG. 2.

The fiber-reinforced synthetic resin of the reinforcing layer 9 has a high viscosity in liquid form, for example in the range 2000-10000 mPa-s at 25 ° C, preferably 3000-8000 mPa-s at 25 ° C, particularly preferably about 5000 mPa-s at 25 ° C. This allows the reinforcement layer 9 to be applied in high build to the release layer 5 by roller or spray application. Besides

- 2 036079 In addition, the high viscosity of the synthetic resin of the reinforcement layer 9 also adheres strongly to the microfibers, so that the risk of individual fibers falling out of the layer during distribution or spraying is minimized.

After application of the reinforcing layer 9 in liquid form, it is hardened (hardened), for example, by self-curing in the case of a two-component synthetic resin, or by the action of light or heat in the case of a photocurable or thermosetting resin.

After the reinforcement layer 9 has been hardened, the impermeability of the (not yet formed) lining 4 can be tested by sparking. In a test of this kind, a high voltage brush (not shown) is moved or rolled over the formed reinforcement layer 9 while the spacer layer 5 is electrically grounded. In the case of the presence of pores or thinning of the hardened layer 9, spark discharges can be observed when moving the brush with high voltage, which reveals a leak or a malfunction.

Finally, a top layer 10 is applied to the cured reinforcement layer 9. The top layer 10 is applied as a liquid, preferably an electrically conductive material, such as a synthetic paint containing graphite, carbon, mica or particulate metal and having a viscosity much lower than the viscosity liquid resin of the reinforcing layer 9. The viscosity of the upper layer 10 is, for example, less than 3000 mPa-s at 25 ° C, preferably less than 2000 mPa-s at 25 ° C, particularly preferably less than 1000 mPa-s at 25 ° C, for example 500- 1000 mPa-s at 25 ° C. By using a low viscosity liquid for the topsheet 10, the thickness of the topsheet 10 can be minimized, while the pores of the reinforcement layer 9 are easily filled, closed and sealed when the topsheet 10 is roller or squeegee spread or sprayed. The top layer 10 is further hardened, for example by drying, and then electrically grounded.

FIG. 3 shows an alternative embodiment of applying a four-layer lining 4 'to the wall 2 of the tank 1. In this embodiment, after the application of the reinforcement layer 9 and before the application of the top layer 10, a sealing layer 11 is applied to the reinforcement layer 9. The sealing layer 11 is applied in the form of a liquid synthetic resin and is then strengthened by curing. The sealing layer 11 seals all possible irregularities on the surface of the reinforcing layers 9. The spark test of the tightness can, of course, preferably be carried out after the completion of the formation of the sealing layer 11 and before the application of the top layer 10.

The viscosity of the liquid synthetic resin of the sealing layer 11 is preferably selected to be higher than the viscosity of the synthetic resin of the reinforcement layer 6, for example, more than 8000 mPa-s at 25 ° C, preferably more than 10,000 mPa-s at 25 ° C, particularly preferably more than 14000 mPa-s at 25 ° C. This provides a sufficient thickness of the seal layer 10, although it is devoid of reinforcing fibers when spread with a roller or doctor blade or sprayed onto the reinforcement layer 9.

FIG. 4 shows an embodiment of the application of the release layer 5 in the form of a plurality of separate foils or sheets, which are mutually overlapping in the overlapping zones 8. Overlap formation between such overlap zones 8, i. E. the overlap from one foil or sheet of separation layer 5 to an adjacent foil or sheet is accomplished by fiber-reinforced ribbons or strips 12. The strips 12 are embedded in the fiber-reinforced synthetic resin reinforcement layer 9, for example by applying a first portion of the liquid synthetic resin reinforcement layer 9 to overlapping foil films or sheets of the release layer 5, followed by the application of tapes or strips 12 to the zones 8 and the application of the rest of the liquid synthetic resin on top of the reinforcing layer 9. The tapes or strips 12 can be, for example, woven or non-woven glass or carbon fiber mats, which can also be pre-impregnated with synthetic resin of the strengthening layer 9 in the form of prepregs.

The invention is not limited to the specific embodiments set forth herein, but includes all variations, modifications, and combinations thereof that fall within the scope of the appended claims.

Claims (17)

CLAIM 1. A method of lining the inner wall (2) of the tank (1), including the sequential application of a separating layer (5), which is permeable to air and electrically conductive in a direction parallel to the inner wall; applying a reinforcing layer (9) consisting of a liquid fiber-reinforced synthetic resin having a first viscosity and curing a reinforcing layer (9) and applying an upper layer (10) consisting of a liquid material having a second viscosity significantly lower than the first viscosity, and hardening of the upper layer (10). 2. A method according to claim 1, wherein said first viscosity is greater than 3000 mPa-s at 25 ° C, and said second viscosity is less than 3000 mPa-s at 25 ° C. - 3 036079 3. A method according to claim 1, wherein the top layer (10) is electrically conductive. 4. A method according to claim 1, wherein the reinforcement layer (9) and the top layer (10) are roller or spray applied. 5. A method according to claim 1, wherein the reinforcement layer (9) is reinforced with microfibers. 6. The method of claim 5, wherein the microfibers are glass staple fibers. 7. The method of claim 6, wherein the glass staple fibers have a length of 3 to 6 mm. 8. A method according to any one of claims 1 to 7, in which a sealant layer (11) is applied to the cured reinforcement layer (9) before the top layer (10) is applied. 9. A method according to claim 8, wherein the sealing layer (11) is composed of a liquid synthetic resin having a third viscosity and is cured before the top layer (10) is applied thereon, said third viscosity being significantly higher than said first viscosity. 10. The method according to claim 9, wherein said third viscosity is greater than 8000 mPa-s at 25 ° C. 11. A method according to claim 9, wherein the chemical resistance of the containment layer (11) to hydrocarbons is higher compared to the reinforcement layer (9). 12. A method according to any one of claims 1 to 7, wherein the separating layer (5) comprises corrugated or embossed aluminum foil or sheet. 13. A method according to any one of claims 1 to 7, wherein the separating layer (5) consists of a plurality of corrugated or embossed aluminum foil films or sheets, adjacent ones overlapping. 14. A method according to claim 13, wherein the fiber-reinforced tape or strip (12) is placed overlapping between adjacent foil films or sheets and embedded in the reinforcement layer (9) when the reinforcement layer (9) is applied to the separating layer (5). 15. A reservoir, the inner wall (2) of which is lined with a separating layer (5), a reinforcing layer (9) and a top layer (10), these layers being applied according to the method according to any one of claims 1-7. 16. A reservoir, the inner wall (2) of which is lined with a separating layer (5), a reinforcing layer (9), a sealing layer (11) and a top layer (10), these layers being applied according to the method according to claim 8 or 9. 17. A reservoir, the inner wall (2) of which is lined with a separating layer (5), a reinforcing layer (9), a sealing layer (11) and a top layer (10), these layers being applied according to the method according to claim 10.