GB2474096A

GB2474096A - Method and system for lining or jacketing storage tanks

Info

Publication number: GB2474096A
Application number: GB1013515A
Authority: GB
Inventors: Stephen Robinson
Original assignee: 1ST ADVANCE TANKS PIPEWORKS Ltd; JACQUELINE ROBINSON
Current assignee: JACQUELINE ROBINSON
Priority date: 2009-10-01
Filing date: 2010-08-11
Publication date: 2011-04-06
Anticipated expiration: 2030-08-11
Also published as: GB0917234D0; GB2474038A; GB201013515D0; GB2474038B; GB2474096B

Abstract

A method for lining the interior or exterior surface of a wall of a tank is described. A primary layer 12 of glass reinforced plastic (GRP) material is applied to the wall of a tank. The primary layer 12 has first and second opposed surfaces 14, 16 with a plurality of spaced, non-intersecting projections 18 extending from the first surface 14. The primary layer 12 is applied with the first surface 14 and the projections 18 facing the tank wall 20 to define a first interstitial gap 22 therebetween. The primary layer 12 is bonded to the tank wall 20 at a plurality of spaced locations 36. A secondary layer 112 of GRP material is applied against the primary layer 12. The secondary layer 112 also has first and opposed surfaces 114, 116 and a plurality of spaced, non-intersecting projections 118 extending from the first surface 114. The secondary layer 112 is applied with its first surface 114 facing the primary layer 12 and the projections 118 contacting the primary layer 12 to define a second interstitial gap 222 therebetween. The secondary layer 112 is bonded to the primary layer 12 at a plurality of spaced locations 38 none of which overlie the bonding locations 36 between the primary layer 12 and the tank wall 20. The arrangement is said to obviate the problem of leakage paths developing which pass through one of the spots of adhesive used to secure the lining layer to the wall of a tank in a single lining layer system.

Description

Method and System for Lining or Jacketing Storage Tanks The present invention relates to a method and system for lining or jacketing storage tanks to protect against leaks. The invention is described with particular reference to storage tanks for fuels such as petrol but is equally applicable to tanks for other purposes.

Leakages from tanks containing fuels or other chemicals may create safety hazards in terms of environmental pollution, fire or explosion risks, etc. Therefore, it is necessary to avoid leakages as far as possible and have early leak detection should a tank failure occur.

GB 2342430 discloses a petroleum product storage tank with a laminated interior liner formed of sheets of glass reinforced plastic material sandwiching a PVC plastic layer formed with castellations or corrugations in order to define a gap. In use, the gap may be evacuated.

Copending application GB 0917234.7 describes a method for lining the interior or exterior surface of a wall of a tank, comprising applying against the wall of the tank a first layer of glass reinforced plastic (GRP) material with first and second opposed surfaces, wherein a plurality of spaced, non-intersecting projections extend from the first surface, and wherein the layer is appied with the first surface facing the tank wall and the projections contacting the tank wall, and bonding the projections to the tank wall to define an interstitial gap between the tank wall and the first surface of the lining material, further comprising bonding at least one additional layer of GRP material against the second surface of the first layer of GRP material to form a lining with a laminated structure.

A potential problem with this arrangement is that it is theoretically possible for a leakage path to be established which passes through one of the spots of adhesive used to secure the lining layer to the wall of the tank. In this case, the leakage path would not intersect the interstitial gap between the tank wall and the lining material.

Therefore, any monitoring system checking the status of the interstitial gap in order to determine when a leak occurs would not be actuated. Current European and British standards (such as BS EN 13160-7:2003)regarding leakage detection systems for tanks such as fuel tanks require a lO0 rate of leak detection. The potential problem described above would mean that this requirement would not be fulfilled.

The present invention addresses these limitations of existing systems.

The present invention provides a method for lining the interior or exterior surface of a wall of a tank, comprising: applying to the wall of the tank a primary layer of glass reinforced plastic (GRP) material which has first and second opposed surfaces, wherein a plurality of spaced, non-intersecting projections extend from the first surface, and wherein the primary layer is applied with the first surface and the projections facing the tank wall to define a first interstitial gap between the tank wall and the first surface of the primary layer, and bonding the primary layer to the tank wall at a plurality of spaced locations; and applying against the primary layer a secondary layer of glass reinforced plastic (GRP) material which also has first and second opposed surfaces and a plurality of spaced, non-intersecting projections extending from the first surface, and wherein the secondary layer is applied with its first surface facing the primary layer and the projections contacting the primary layer to define a second interstitial gap between the primary layer and the secondary layer, and bonding the secondary layer to the primary layer at a plurality of spaced locations none of which overlie the bonding locations between the primary layer and the tank wall.

In this way, any leakage path between the interior and exterior of the tank must intersect one of the interstitial gaps and therefore will be detectable.

Preferably, the method further comprises bonding a base layer of GRP material to the tank wall before applying the primary layer, so that the primary layer is bonded to the base layer.

In addition, the method may further comprise bonding at least one finishing layer of GRP material against the second surface of the secondary layer.

Preferably, the method further comprises applying a sealing layer to the finishing layer of GRP material.

Conveniently, the method further comprises forming an opening in the tank wall or the lining layer and in communication with the interstitial gaps and securing a valve in the opening.

In particular this may involve forming the opening through the tank wall and cutting away the primary and secondary layers in the area of the opening to allow space to accommodate the valve, and further comprising forming a cap over the cut away area by applying a third layer of GRP material against at least a part of the secondary layer and extending over the cut away area.

The method preferably also involves either evacuating the interstitial gaps, filling the interstitial gaps with pressurised gas or filling the interstitial gaps with liquid, and installing status monitoring apparatus to detect a change in pressure or a change in liquid level in the interstitial gaps.

Any change in status detected by the monitoring apparatus will therefore indicate a leak in the tank wall and/or the lining layer.

In a second aspect, the present invention provides a tank having a wall with interior and exterior surfaces and a lining applied against at least one of the interior or exterior surfaces, the lining comprising at least two layers of GRP material bonded together to form a laminate, wherein a primary layer and a secondary layer of the lining each comprise first and second opposed surfaces and a plurality of spaced, non-intersecting projections extending from the first surface, wherein the first surface of the primary layer and its projections face the tank wall to define a first interstitial gap between the tank wall and the primary layer, and the primary layer is bonded to the tank wall at a plurality of spaced locations, wherein the first surface of the secondary layer faces the second surface of the primary layer and its projections contact the primary layer to define a second interstitial gap between the primary layer and the secondary layer, and the secondary layer is bonded to the primary layer at a plurality of spaced locations none of which overlie the bonding locations between the primary layer and the tank wall.

The tank may further comprise a base layer of GRP material bonded to the tank wall between the primary layer and the tank wall.

The tank may also comprise at least one finishing layer of GRP material bonded to the second surface of the secondary layer.

Preferably the interstitial gaps are either evacuated, filled with pressurised gas, or filled with liquid, and the tank further comprises status monitoring apparatus operable in use to detect a change in pressure or a change in liquid level in the interstitial gaps.

Preferably the status monitoring apparatus includes a visual and/or audible alarm actuable when changes in pressure or liquid level are detected.

The tank may further comprise a sealing layer applied to the finshing layer of GRP material.

In one example the projections comprise a plurality of ribs. Alternatively, the projections may comprise one or more of cones, cylinders, domes, cubes or pyramids.

Preferably the tank further comprises at least one valve in the tank wall and/or the lining layer allowing selective communication with the interstitial gap.

In one example, the valve is located in an opening in the tank wall and the primary and secondary layers are cut away in the area of the opening to allow space to accommodate the valve, and a cap is formed over the cut away area by a third layer of GRP material applied against at least a part of the secondary layer and extending over the cut away area.

In a third aspect, the present invention provides a system for lining the interior or exterior surface of a wall of a tank, comprising primary and secondary sheets formed of GRP material and each having first and second opposed surfaces, and a plurality of spaced, non-intersecting projections extending from the first surface; means to bond the primary sheet to a tank wall at a plurality of spaced locations, with the first surface and the projections facing the wall in order to define a first interstitial gap between the tank wall and the first surface of the primary sheet; and means to bond the secondary sheet to the primary sheet at a plurality of spaced locations none of which overlie the bonding locations between the primary sheet and the tank wall, with the projections of the secondary sheet contacting the primary sheet in order to define a second interstitial gap between the primary sheet and the secondary sheet.

The system may further comprise a base sheet formed of GRP material, and means to bond the base sheet to the tank wall between the primary sheet and the tank wall.

The system may also comprise a finishing sheet formed of GRP material, and means to bond the finishing sheet to the secondary sheet.

The system preferably further comprises means either to evacuate the interstitial gaps or to fill the interstitial gaps with pressurised gas or with liquid, and status monitoring apparatus operable to detect a change in the pressure or a change of the liquid level in the interstitial gaps.

The projections may comprise a plurality of ribs.

Alternatively, the projections may comprise one or more of cones, cylinders, domes, cubes or pyramids.

Thus, the present invention provides a method and system for lining the interior surface, or jacketing the exterior surface, of an existing tank with a GRP laminate to create a double skinned structure, and a tank with such a lining or jacketing. The GRP laminate forms a structural member. The interstitial gaps are either evacuated, pressurised or filled with liquid. The status of the interstitial gaps are monitored so that any change of status, such as loss of pressure or a drop in liquid level, indicating a tank failure, actuates a warning system.

The system can be applied to new tanks, or to existing tanks in situ. For in situ underground tanks, the interior surface will be lined to form the double skinned structure.

In situ or new above ground tanks may either be lined internally or jacketed externally to form the double skin structure. For existing tanks the system may be applied to upgrade to sound, or to repair and upgrade a tank which has already failed, to restore its structural integrity. The tanks themselves may be single skinned, or may already have a double skinned construction. In either case, in the following description reference to obtaining a doubled skinned structure with the present invention refers to combining whatever existing wall structure the tank may have, whether single, double or other configuration, with the lining/jacketing of the invention, which is itself a multi-layer construction. Also in the following description, reference to lining a tank is intended to cover both lining the interior surface of a tank and lining the exterior surface (i.e. jacketing) and reference to a lining material or lining layer may refer to the layer applied either internally or externally.

The present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a cross sectional view of part of a tank wall with a lining system in accordance with one embodiment of the present invention, shown schematically and not to scale.

Figure 2 is a plan view of a lining sheet for creating an interstitial gap.

The present invention provides a laminated tank lining layer 10 which is formed partially of primary and secondary flexible glass reinforced plastic (GRP) sheets 12 and 112, each with opposed first and second surfaces 14, 16 and 114, 116. A plurality of projections 18 and 118 are formed on the first surface of each sheet 12, 112. Preferably, these projections 18, 118 are in the form of a grid of ribs as shown in Figure 2. The ribs do not intersect each other so that the spaces between the ribs communicate with one another. The second, opposing surface 16, 116 of each sheet 12, 112 is substantially flat. It will be appreciated that ribs could be replaced by other configurations of projection such as cones, cylinders, domes, cubes or pyramids, or any other convenient form.

The primary and secondary sheets 12, 112 may be formed in any appropriate manner. Typically, this is by applying chopped strand glass fibre reinforced mat into a mould impregnated with a polyester resin and leaving the resulting sheet to cure. However, other GRP materials could be used, for example glass flake filled resin. The mould is generally flat but provided with grooves or recesses of the appropriate shape to form the projections 18, 118 on the sheet 12, 112.

After curing, the sheet 12, 112 is released from the mould and is slightly flexible to allow it to be fitted to the curved shape of a tank.

-10 -In one example, the sheets 12, 112 measure approximately 2.44m by l.22m, with the projections 18 are approximately 3mm wide, 3mm deep and 50mm long. However, all these dimensions may be varied as required to suit the application.

In use, the wall 20 of a tank to be lined is prepared, e.g. cleaned, repaired if any leaks are present, etc. A base layer 11 of GRP material may be bonded to the tank wall 20 to provide a smooth base for application of subsequent layers. The primary sheet of GRP lining material 12 is applied either by hand or some mechanical means, with the first surface 14 facing the base layer 11 and the projections 18 contacting the base layer 11 (or the tank wall 20 if the base layer 11 is not used) . At the areas of contact the projections 18 may be chemically spot bonded to the base layer 11 e.g. with polyester bonding paste or a suitable grab adhesive. In addition a plurality of spots of adhesive 36 at various locations between the ribs 18 adhere the first surface 14 directly to the base layer 11, to ensure the primary sheet 12 is securely attached. The projections 18 ensure that a continuous interstitial space 22 is defined between the base layer 11 and the primary sheet 12.

Subsequently, a secondary GRP sheet 112 is applied by hand or mechanical means against the primary sheet 12. The first surface 114 of the secondary sheet 112 faces the flat surface 16 of the primary sheet 12 and the projections 118 contact the flat surface 16. As before, at the areas of contact the projections 118 may be chemically spot bonded to the surface 116. Further spots of adhesive 38 are -11 -provided between the ribs 118 to adhere the surface 114 directly to the surface 16 of the primary sheet 12. . In this way, a second interstitial gap 222 is provided between the primary sheet 12 and the secondary sheet 112.

However, crucially, the adhesive spots 38 are at different locations to the spots 36 so that none of the adhesive spots 38 lie directly over any of the adhesive spots 36 For applications in which it is intended to pressurise the interstitial gap 22, 222 or fill it with liquid, generally smaller lining sheets 12, 112 will be used than if it is intended to evacuate the interstitial gaps 22, 222.

The smaller primary sheets 12 for pressurised/liquid filled applications are preferably individually tied to the base layer 11 or tank wall 20 at their edges with further prices or GRP material. Adjoining lining sheets may be butted together or overlapped. Each joint is then covered with further strips of GRP material.

Subsequently, one or more openings communicating with the interstitial gaps 22, 222 may be formed through the lining layer 10 and/or through the existing tank wall 20 and a valve 30 such as a high pressure ball valve is secured in the opening. This allows the interstitial gaps 22, 222 to be either evacuated, pressurised with air or other gas, or filled with liquid.

In the example shown in Figure 1, the valve 30 is fitted to the exterior of the tank and passes through the tank wall 20 and into the lining layer 10. To allow -12 -sufficient space to accommodate the valve 30, the base layer 11, and the primary and secondary sheets 12, 112 are cut away. Therefore, a cap 212 is provided over the cut away area by a portion of a third GRP sheet.

A finishing layer 24 of GRP material is then applied over the entire surface of the secondary layer of lining material 112, and the cap 212 if present, and the layers are chemically bonded together to form a laminate. Further layers may be added if desired. This laminated structure formed of multiple layers of the same material provides a very strong lining layer of greater structural integrity than linings made of a combination of different materials.

Optionally, preformed rib sections of GRP material, e.g. flanged sections of approximately 50mm to 100mm in length and moulded into the same profile as the tank, may be bonded to the lining layer 10 for additional strength.

Additional coats of resin 26 may then be applied to the finishing layer 24. Finally, a sealing top coat 28 is applied. For tanks which are internally lined, this will be the layer in contact with the product stored in the tank and must therefore be impervious and resistant to it. For example, for applications in the petroleum industry ATLAC 590 vinyl ester resin is specified as it is resistant to 85% ether alcohol EA85. For externally lined (jacketed) tanks, a waterproofing final top coat may be required.

Thus a double skinned construction is now created with the first skin being the pre-existing tank wall 20 and the second skin being the lining layer 10, with interstitial -13 -gaps 22, 222 therebetween. As mentioned previously, the first skin may itself be a single walled, double walled or other construction. The second skin will be a laminate comprising at least primary and secondary layers of GRP lining material 12, 122 and various other layers, such as base layer 11, finishing layer 24 and resin and sealant layers 26, 28.

Monitoring equipment 32 may be installed to monitor the status of the interstitial gaps 22, 222, i.e. to determine whether the vacuum is maintained, the pressure is maintained or the liquid level is maintained as appropriate. The monitoring equipment 32 is connected to an appropriate alarm system 34, e.g. by a cable or a remote signal. In this way, any change in the status of either of the interstitial gaps space 22, 222 which would indicate a tank failure and possible leak, will actuate an alarm such as an audible and/or visual alarm.

If a leakage path represented by line P in Figure 1 happens to pass through an adhesive spot 36, it cannot penetrate fully through the entire tank wall 20 and lining layer 10, thus leading to leakage into and out of the tank, without also intersecting the second interstitial gap 222.

Similarly, if an alternative leakage path represented by line F' in Figure 1 passes through an adhesive spot 38 it cannot penetrate fully through the entire tank wall 20 and lining layer 10 without also intersecting the first interstitial gap 22. Therefore, in either case one of the interstitial gaps 22, 222 is compromised and the alarm system 34 will be operated. In this way, 100 leak detection ability is provided.

-14 -Therefore, an improved tank lining/jacketing method and system is provided which can be applied to new tanks or fitted in situ to existing tanks, whether above ground or underground. It will be appreciated that the precise details of the invention can be varied to suit the application without departing from the scope of the invention as set out in the claims.

Claims

-15 -CLAIMS1. A method for lining the interior or exterior surface of a wall of a tank, comprising: applying to the wall of the tank a primary layer of glass reinforced plastic (GRP) material which has first and second opposed surfaces, wherein a plurality of spaced, non-intersecting projections extend from the first surface, and wherein the primary layer is applied with the first surface and the projections facing the tank wall to define a first interstitial gap between the tank wall and the first surface of the primary layer, and bonding the primary layer to the tank wall at a plurality of spaced locations; and applying against the primary layer a secondary layer of glass reinforced plastic (GRP) material which also has first and second opposed surfaces and a plurality of spaced, non-intersecting projections extending from the first surface, and wherein the secondary layer is applied with its first surface facing the primary layer and the projections contacting the primary layer to define a second interstitial gap between the primary layer and the secondary layer, and bonding the secondary layer to the primary layer at a plurality of spaced locations none of which overlie the bonding locations between the primary layer and the tank wall.
2. A method as claimed in claim 1, further comprising bonding a base layer of GRP material to the tank wall before applying the primary layer, so that the primary layer is bonded to the base layer.

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3. A method as claimed in claim 1 or claim 2, further comprising bonding at least one finishing layer of GRP material against the second surface of the secondary layer.
4. A method as claimed in claim 3, further comprising applying a sealing layer to the finishing layer of GRP material.
5. A method as claimed in any preceding claim, further comprising forming an opening in the tank wall or the lining and in communication with the interstitial gaps, and securing a valve in the opening.
6. A method as claimed in claim 5, further comprising forming the opening through the tank wall and cutting away the primary and secondary layers in the area of the opening to allow space to accommodate the valve, and further comprising forming a cap over the cut away area by applying a third layer of GRP material against at least a part of the secondary layer and extending over the cut away area.
7. A method as claimed in claim 5 or claim 6, further comprising either evacuating the interstitial gaps, filling the interstitial gaps with pressurised gap or filling the interstitial gaps with liquid, and installing status monitoring apparatus to detect a change in pressure or a change in liquid level in the interstitial gaps.
8. A tank having a wall with interior and exterior surfaces and a lining applied against at least one of the interior or exterior surfaces, the lining comprising at least two layers of GRP material bonded together to form a -17 -laminate, wherein a primary layer and a secondary layer of the lining each comprise first and second opposed surfaces and a plurality of spaced, non-intersecting projections extending from the first surface, wherein the first surface of the primary layer and its projections face the tank wall to define a first interstitial gap between the tank wall and the primary layer, and the primary layer is bonded to the tank wall at a plurality of spaced locations, wherein the first surface of the secondary layer faces the second surface of the primary layer and its projections contact the primary layer to define a second interstitial gap between the primary layer and the secondary layer, and the secondary layer is bonded to the primary layer at a plurality of spaced locations none of which overlie the bonding locations between the primary layer and the tank wall.
9. A tank as claimed in claim 8 further comprising a base layer of GRP material bonded to the tank wall between the primary layer and the tank wall.
10. A tank as claimed in claim 8 or claim 9, further comprising at least one finishing layer of GRP material bonded to the second surface of the secondary.
11. A tank as claimed in any of claims 8-10, wherein the interstitial gaps are either evacuated, filled with pressurised gas, or filled with liquid, and further comprising status monitoring apparatus operable in use to detect a change in pressure or a change in liquid level in the interstitial gaps.

-18 -
12. A tank as claimed in claim 11, wherein the status monitoring apparatus includes a visual and/or audible alarm actuable when changes in pressure or liquid level are detected.
13. A tank as claimed in any of claims 8-12, further comprising a sealing layer applied to the finishing layer.
14. A tank as claimed in any of claims 8-13, wherein the projections comprise a plurality of ribs.
15. A tank as claimed in any of claims 8-13, wherein the projections comprise one or more of cones, cylinders, domes, cubes or pyramids.
16. A tank as claimed in any one claims 8-15, further comprising of at least one valve in the tank wall and/or the lining layer allowing selective communication with the interstitial gaps.
17. A tank as claimed in claim 16, wherein the valve is located in an opening in the tank wall and the primary and secondary layers are cut away in the area of the opening to allow space to accommodate the valve, and a cap is formed over the cut away area by a third layer of GRP material applied against at least a part of the secondary layer and extending over the cut away area.
18. A system for lining the interior or exterior surface of a wall of a tank, comprising primary and secondary sheets formed of GRP material and each having first and second opposed surfaces, and a plurality of spaced, non- -19 -intersecting projections extending from the first surface; means to bond the primary sheet to a tank wall at a plurality of spaced locations, with the first surface and the projections facing the wall in order to define a first interstitial gap between the tank wall and the first surface of the primary sheet; and means to bond the secondary sheet to the primary sheet at a plurality of spaced locations none of which overlie the bonding locations between the primary sheet and the tank wall, with the projections of the secondary sheet contacting the primary sheet in order to define a second interstitial gap between the primary sheet and the secondary sheet.
19. A system as claimed in claim 18, further comprising a base sheet formed of GRP material and having first and second surfaces, and means to bond the base sheet to the tank wall between the primary sheet and the tank wall.
20. A system as claimed in claim 18 or claim 19, further comprising a finishing sheet formed of GRP material, and means to bond the finshing sheet to the secondary sheet.
21. A system as claimed in any of claims 18-20, further comprising means either to evacuate the interstitial gaps or to fill the interstitial gaps with pressurised gas or with liquid, and status monitoring apparatus operable to detect a change in the pressure or a change of the liquid level in the interstitial gaps.
22. A system as claimed in any of claims 18-21, wherein the projections comprise a plurality of ribs.

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23. A system as claimed in any of claims 18-21, wherein the projections comprise one or more of cones, cylinders, domes, cubes or pyramids.
24. A method for lining the interior or exterior surface of a wall of a tank substantially as hereinbefore described and with reference to the accompanying drawings.
25. A tank as substantially and hereinbefore described and with reference to the accompanying drawings.
26. A system for lining the interior or exterior surface of a wall of a tank substantially as hereinbefore described and with reference to the accompanying drawings.