Wall structure monitoring system

Abstract

A wall having a fluid impervious coating thereon and further having a monitoring arrangement which provides for monitoring the condition of the wall. The monitoring arrangement mounted on a surface of the wall.

Claims

1. A wall having a fluid impervious coating on an inner surface thereof and further comprising a monitoring arrangement which provides for monitoring the condition of the wall, the monitoring arrangement mounted on the inner surface of the wall, the inner surface of the wall and at least a part of the monitoring arrangement having the fluid impervious coating applied thereto, the monitoring arrangement including one of: a housing attached to and enclosing an enclosed region of the inner surface of the wall, the housing having an outer surface and extending to the same side thereof as the fluid impervious coating, the fluid impervious coating being applied to a part of the outer surface of the housing, the housing having a removable closure member that is fluid tight when closed, the housing providing access to the enclosed region of the inner surface of the wall that is not coated by the fluid impervious coating, wherein a space is formed between the inner surface of the wall in the enclosed region and an underside of the removable closure member; and a protective member attached to the inner surface of the wall, the protective member enclosing a region of the inner surface, wherein the protective member is situated between the inner surface of the wall and the fluid impervious coating and the enclosed region of the inner surface of the wall is not coated by the fluid impervious coating and wherein a space is formed between the inner surface in the enclosed region and an underside of the protective member.

2. A wall according to claim 1, wherein the coating has a nominal thickness of one of: at least 500 micron and at least 1270 micron.

3. A wall according to claim 1, wherein the coating is a resin coating.

4. A wall according to claim 3, wherein the resin is one of: solvent free and solvented.

5. A wall according to claim 3, wherein the resin is an epoxy resin.

6. A wall according to claim 1, wherein the housing includes a plate for attachment to the wall and the enclosed region is formed between the plate and the closure member.

7. A wall according to claim 6, wherein the plate has an opening therein through which access to the wall may be gained, the opening in the plate communicating into the enclosed region of the housing.

8. A wall according to claim 1, further comprising: monitoring means configured for monitoring the condition of the wall.

9. A wall according to claim 8, wherein the monitoring means comprises at least one sensor.

10. A wall according to claim 9, wherein the at least one sensor is connected to an external data receiving by one of a wired and wireless connection.

11. A wall according to claim 9, wherein the at least one sensor is mounted in one of: the housing and the protective member.

12. A structure comprising at least one wall, wherein the at least one wall of the structure is a wall having a fluid impervious coating thereon and further comprising a monitoring arrangement which provides for monitoring the condition of the wall, the monitoring arrangement mounted on a surface of the wall, the monitoring arrangement including one of: a housing, attached to and enclosing a region of the inner surface of the wall, the housing having an outer surface and extending to the same side thereof as the fluid impervious coating, the fluid impervious coating being applied to a part of the outer surface of the housing, the housing having a removable closure member that is fluid tight when closed, the housing providing access to the enclosed region of the inner surface of the wall that is not coated by the fluid impervious coating, wherein a space is formed between the inner surface of the wall in the enclosed region and an underside of the removable closure member; and a protective member attached to the inner surface of the wall, the protective member enclosing a region of the inner surface, wherein the protective member is situated between the inner surface of the wall and the fluid impervious coating and the enclosed region of the inner surface of the wall is not coated by the fluid impervious coating and wherein a space is formed between the inner surface in the enclosed region and an underside of the protective member.

13. A structure according to claim 12, wherein the structure is one of: a tank, a pipe, a turbine support structure, a water borne platform structure, a water bourne platform structure component part, a building support structure, and a bridge support structure.

14. A structure according to claim 12, wherein the at least one wall of the structure is provided with a plurality of monitoring arrangements.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings, which illustrate preferred embodiments of the invention, and which are by way of example:

(2) FIG. 1 is schematic representation of an above ground tank;

(3) FIG. 2a is a plan view of an inspection assembly comprising a plate for attachment to a tank wall and an inspection port box connected thereto;

(4) FIG. 2b is an exploded view of assembled components illustrated in FIG. 11a;

(5) FIG. 3 illustrates a tank bottom wall provided with a plurality of inspection assemblies of the type illustrated in FIGS. 11a and 11b with provision for remote mon toeing;

(6) FIG. 4 is a schematic representation of the inspection box illustrated in FIGS. 11a and 11b provided with instrumentation;

(7) FIG. 5 illustrates a tank bottom wall provided with an alternative type of monitoring arrangement; and

(8) FIG. 6 is a schematic cross-sectional view of the mounting arrangement illustrated in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(9) Referring now to FIG. 1, which illustrates an above ground tank 1 comprising a side wall 2 a bottom wall 3 and a top wall 4. The bottom wall 3 and the side wall 2 are provided with sensors 50 (which are described in greater detail with reference to FIGS. 5 and 6 below). The walls of the tank in the illustrated example are single skinned, that is there is one wall rather that two walls separated by an interstitial space. The walls may be formed of metal such as steel and may be coated with a corrosion resistant material. The thickness of corrosion resistant coating will depend on the condition of the walls prior to application of the corrosion resistant coating. For example, where the tank is new and the metal of the walls is substantially free of corrosion a coating that is relatively thin may be used, whereas where the tank is being refurbished following significant corrosion of the walls a comparatively thicker coating will be required as described in greater detail below. The bottom wall 3 of the tank 1 is provided with a sump 5 which provides for emptying of the tank 1.

(10) Prior to application of a corrosion resistant coating the surface of wall 1 is prepared by cleaning, typically by shot blasting and then a layer of solvent free (or solvented) resin is applied to a thickness of between 500 micron and 1500 micron. Where there has been significant surface corrosion the surface can be pitted post cleaning. Where such surface pitting exists the nominal thickness of the solvent free resin coating will typical be 1270 micron or greater and preferably in the range 1270-1500 micron. Where there is little or no pitting the solvent free resin coating is applied to a nominal thickness of 500 micron to 1000 micron. Nominal thickness means an average of the thicknesses of the coating measured at a number of, for example 100, points. The solvent free resin is usually applied by spraying using equipment that is widely available and known in the art. In the illustrated example, the solvent free resin is a two component polycyclamine epoxy and includes glass flake and fibre reinforcement. The polycyclamine epoxy is a novolac epoxy resin. One solvent free resin having these properties is Enviroline (registered trade mark) 376F-60 (SPL) available from Akzo Nobel.

(11) The solvent free resin coat is allowed to cure for 24 hours. The surface provided by the cured resin is in itself impervious to fluids such as water, fuel, oil etc. If the solvent free coating is applied to a sufficient thickness, that is greater than 1270 micron, the cured solvent free epoxy resin coating can bridge holes in the metal of wall 1 of up to 50 mm diameter.

(12) If after cleaning, pits in the wall are too deep to be covered adequately by the sprayed on solvent free epoxy resin, any such pits can be filled with a two part epoxy filler that is compatible with the solvent free epoxy resin. Once pits are filled the solvent free epoxy coating may be applied to the cleaned metal surface and any filler applied thereto. Suitable fillers include Hempel ProFiller 35370 from Hempel A/S and AWLFAIR LW D8200/D7200 from Akzo Nobel.

(13) Above-ground structures (tanks in particular) are susceptible to external corrosion, especially in the bottom wall thereof, which is often inaccessible. FIG. 2a illustrates an inspection assembly 30 comprising a plate 31 for attachment to a tank wall and an inspection port box 32. The plate 31 includes a hole 31a. The inspection port box 32 also includes a hole 32a which aligns with the hole 31a when the inspection port box 32 is mounted on the plate 31. The inspection port box 32 is welded to the plate 31. The inspection port box 32 is provided with a lid 33 that is removable from the box 32. A seal, not shown, is provided between the lid 33 and the box 32.

(14) The inspection assembly 30 illustrated in FIGS. 2a and 2b is relatively small, the port plate being approximately 115 mm115 mm, with the inspection port box 32 being approximately 76 mm76 mm. The holes 31a, 32a in the example are approximately 50 mm in diameter. The sizes of the components of the inspection assembly are given by way of example only.

(15) FIG. 3 illustrates the inside surface of the bottom wall 3 of an above-ground tank, the bottom wall 3. In the illustrated example, six inspection assemblies 30 are attached to the bottom wall 3 at spaced apart locations. The surfaces of the plate 31, the walls of the inspection box 32 and the lid 33 that face into the tank 1 are coated with the same or a similar coating to the inner surfaces of the walls 2-4 of the tank 1.

(16) Referring now to FIGS. 3 and 4, the inspection boxes 32 are provided with sensor ports 34a each equipped with a sensor 34b for monitoring the condition of the bottom wall 3. The sensor ports 34a sit in the hole 32a in the inspection port box 32. The sensor ports 34a each comprise a block of metal such as mild steel in which the sensor 34b is mounted. The sensors 34b may be ultrasonic sensors. Signals from the sensors may be conveyed to an external data receiving system by wires 35 or by means of wireless communication. In the wired arrangement illustrated in FIGS. 3 and 4 the inspection boxes 32 are provided with ports 36 through which the wires 35 pass. The ports 36 are sealed against ingress of fluid when the wires have been passed through the ports. It is preferred that the wires 35 are encapsulated and therefore separated from the contents of the tank. In the illustrated example, trunking 42 is provided. This trunking may sit on top of the fluid impervious coating covering the bottom wall 3. The trunking may be attached to the fluid impervious coating of the bottom wall 3 by means of a suitable adhesive. The trunking may then be coated with the same or a similar fluid impervious coating to that applied to the liner surface of the wall 3. The wires 35 exit the tank via a pipe penetration apparatus which allows the wires 35 to be accessed whilst preventing egress of fluid from the tank.

(17) The inspection boxes 32 illustrated in FIGS. 2 to 4 provide for manual inspection of the bottom wall 3. Inspection is carried out by draining the content of a tank, for example via sump 5, entering the tank and removing the lid 33. The bottom wall 3 may be inspected visually through the holes 31a, 32a or by using non destructive testing equipment that is brought to the tank. There the inspection box is equipped with sensor ports 34a and sensor 34b, the wall 3 may be inspected manually by removing the sensors port 34a from the hole 32a of the inspection box 32.

(18) By providing for both manual and remote inspection it is possible that manual inspection cycles may be lengthened, whilst providing for corrosion to be detected earlier than high occur with manual inspection only.

(19) FIG. 5 illustrates a bottom wall 3 of the above-ground tank that is instrumented with sensors 50, typically ultrasound sensors, which are encapsulated within the fluid impervious coating described above. In this arrangement, manual inspection of the bottom wall 3 is not possible. The ultrasound sensors 50 are equipped are wireless enabled so that data can be transmitted to an external data receiver. Alternatively, the sensor 50 could be connected by wires to an external data receiver. Where wired connections are used, trunking similar to described with reference to FIG. 4 may be deployed. The ultrasound sensors 50 are shown distributed around the bottom wall 3. The sensors 50 may be distributed around the tank so that the condition of specific components of the tank. For example, the bottom wall may comprise a bottom plate and an annular ring. One or both of these components may be provided with a number of sensors. Advantageously, the sensors are identifiable by the external data receiving means. For example, if the sensors are wirelessly enabled each may have its now identification code. Where the sensors are wired, those wires may be connected such that the location of respective sensors may be identified.

(20) FIG. 6 illustrates one of the sensors 50 situated between the bottom wall 3 and a layer of fluid impervious coating 7 as described generally with reference to FIG. 1 for example. The sensor 50 is attached by means of a suitable adhesive to the surface of the structural wall 3 after its surface has been cleaned, typically by blasting thereof. A protective cap 51 is located over the sensor 50. The cap 51 is also attached to the surface of the structural wall 3 by adhesive. The function of the cap 51 is to protect the sensor 50 from inadvertent damage, for example if the sensor 50 were to be walked on. The cap may be formed from pressed steel or a plastic. Typically, it is only the area of the wall 3 immediately beneath the sensor 50 that is not coated with the fluid impervious coating. Where the fluid impervious coating is taken up to the edge of the sensor 50 the cap 51 is attached to that fluid impervious coating, typically by adhesive, and a further layer of fluid impervious coating is applied over the cap 51 and the area of the coated wall 3 immediately around the cap 51. Of course, the cap 51 may be attached to the surface of the wall 3 before the fluid impervious coating is applied thereto. In this case, the fluid impervious coating is applied over the surface of the wall 3 and the cap 51.

(21) The invention has been described in relation to a tank. However, other types of structure may benefit from the invention. For example, wind turbine towers, oil rig legs, large diameter pipes, etc. In relation to tanks, it is not only fuel tanks that may benefit from the monitoring arrangements described herein. Many liquids have corrosive properties and hence preventing contact between such liquids and the structural wall may be useful. Also, liquids may not be corrosive to a structure, but they may be harmful to the environment if they escape, and walls of a tank may be subject to external corrosion. Hence, providing a means by which the condition of the wall of a tank may be monitored is beneficial.