GB2418952A

GB2418952A - A containment chamber

Info

Publication number: GB2418952A
Application number: GB0520231A
Authority: GB
Inventors: John Alexandre Boudry; Paul Ridge
Original assignee: Petrotechnik Ltd
Current assignee: Petrotechnik Ltd
Priority date: 2004-10-05
Filing date: 2005-10-05
Publication date: 2006-04-12
Also published as: WO2006038015A1; GB0520231D0

Abstract

A chamber comprises a base section adapted to engage with the collar 121 of a tank 120, and a riser section 126 attached to the top of the base section 125. An endless channel 133 is provided at the interface of the riser and base, it is adapted to contain a sealing agent to forma fluid tight seal between the two sections. The channel may be integral to either the riser or the base, engagement means such as barbs or a snap-fit arrangement may be provided inside the channel. The chamber may be double-walled, having inner and outer skins bonded together. The engagement means preferably prevents the skins separating. The endless channel is preferably sufficiently broad to allow the tapering riser to be shortened. The base section may be polygonal or circular in section. The inner and outer base skins preferably both have endless channels such that they can be used either alone or in combination. A resin suitable for bonding GRP is preferably used for sealing.

Description

24 1 8952

IMPROVED CHAMBER

Field of the Invention

This invention relates to chambers and to methods of constructing chambers. It is particularly applicable, but in no way limited, to fluidtight underground containment chambers, including modular chambers, as found associated with subterranean fuel tanks or sumps, for example in petroleum forecourt installation.

Background of the Invention

In typical underground storage and distribution systems for hazardous fluids such as hydrocarbon fuels, the fuels are usually stored in a large storage tank or tanks buried in the ground and delivered through underground piping to delivery pumps or the like.

In recent years there has been an increasing awareness that these primary storage and distribution systems of hazardous fluids need to be contained to prevent product from leaking into the environment to prevent environmental problems such as contamination of public drinking water and making some of the food supply unusable as well as other serious environmental consequences. New laws have focused on this problem requiring improved means of storage, distribution and leak detection for all stored fluids which are characterized as hazardous. These systems can present a hazard to the environment because of poor installation practices, corrosion and structural failures producing leaks contaminating the environment.

These laws and regulations have given rise to so-called secondary containment systems which essentially provide a second barrier of protection around the primary fluid supply storage and delivery systems.

Typically, secondary containment systems have included access chambers which are an offshoot from the so-called back fill retainer. There are a variety of chambers now on the market usually comprising a base defining an enlarged chamber, a riser (or corbel) connected to the base of smaller diameter and a cover fitting over the top end of the riser which, in some instances, has access openings enclosed by an access lid which provide a means for inspecting the interior of the sump chambers.

Oil companies have been under considerable pressure to ensure that environmental concerns are given priority in the planning and installation of petrol station infrastructures. Regulations contain specific requirements that underground pumps and piping connections be provided with a means of secondary containment whereby any leaks in these plumbing connections will be contained and detected by means of a leak sensing device.

As a result of these new regulations, large containment containers have been introduced on to the market called containment chambers or Bumps.

Containment chambers are typically found at fuel service stations whereby they are installed below the ground level provide a means of access to the underground piping connections, submersible pumps, leak detection sensors, fire extinguisher and other plumbing components usually found connected to the top of underground storage tanks or under fuel dispensing units. There are generally two types of containment chambers which are similar in purpose but different in design. The first type is commonly referred to as a "tank chamber" which is installed and connected to the top of an underground storage tank. The second type is commonly referred to as a "dispenser sump", which is installed under a fuel- dispensing unit.

Containment chambers are multi-purpose in function: 1. They provide a means of surface access to equipment, plumbing and miscellaneous devices, installed underground.

2. They provide a means of ground isolation for contained components to prevent corrosion and decay.

3. They provide a means of secondary containment for those contained components which handle hazardous liquids.

4. They perform as a collection sump for double wall piping entering the sump.

Dispenser sumps are installed under the fuel dispenser to provide a means of secondary containment for the dispenser plumbing and the underground piping connections located directly below the dispenser. These dispenser sumps are available in both shallow and deep versions.

Tank chambers are installed above the underground storage tank and provide a means of secondary containment from the plumbing and piping connections located above the tank. They provide access to the manway, which in turn provides access to the interior of the tank. The tank chambers are of variable length, to allow for different depths of tanks, as they need to have a height sufficient to travel from ground level down to the top of the tank.

Subterranean piping systems, which are typically found at service stations, connect the remote underground storage tank to one or more above ground fuel dispensing units. At each of these connection locations are found access enclosures which provides surface access to these piping connections and other equipment such as a tanks' pump, valves and other plumbing devices.

As explained above, the underground storage and fuel dispensing system has been determined to be a source of environmental pollution, as well as a safety hazard because of product leakage into the surrounding earth. All components of that storage and dispensing system should be designed in such a manner that they prevent any leakage into the environment. Access chambers located at the tank and under the dispensing units provide a means of secondary containment for part of the entire system.

These access chambers should be of such a design that they are liquid tight preventing ground and surface water from entering the chamber, and preventing any leaking product escaping from the chamber into the surrounding environment. They should also be made of a material which is resistant to corrosion and deterioration and of sufficient strength to withstand external pressure from surface loads, backfill pressure, and high ground water pressures. They should also be designed and installed so that they flex or shift in such a manner that they do not damage the top of the tank as a result of tank, ground or surface movement. They should provide a means of effectively sealing all conduit and pipe penetrations into the chamber and provide a means for forming liquid tight and secure connections to the tank and dispensing island.

These chambers have been made from a variety of materials including metal containers made of coated steel, non-corrodible fibreglass or fusible thermoplastic materials. The chambers can house pumps and are often located at the lowest point of a sloped secondary piping system and thus are a focus of the collection of leaked fluids. They are viewed as multipurpose chambers.

Even though the secondary containment systems and detecting means have improved considerably over a relatively short period of time in response to continuously changing environmental and safety regulations and laws, there are still certain component parts and design concepts of these secondary containment systems discussed above which do not provide the optimum solution in developing more fail safe secondary containment systems. For example, even though seals have been utilized between the lip of the chamber cover and the top of the riser adjacent the open end, these seals have not proven adequate under extreme conditions to provide a truly water tight or hermetically sealed chamber. For example, in areas where the water table is high, the external pressure on the riser often results in a breakage of the seal and migration of fluids into or out of the sump chamber which, of course, is undesirable.

The first containment chambers introduced to the market in the middle 1980's were very limited in design and did not prove to be completely liquid tight.

These early models were usually made of fibreglass or corrosion protected steel.

Because of their design, they were not height adjustable, were difficult to field install and fabricate and provided restrictive pipe and conduit entry capabilities. The one- piece construction made the pump and piping installation difficult. Chambers made of coated steel were unpopular because of their potential to fail due to corrosion over time. The chambers made of rigid fibreglass and steel achieved limited success in providing a liquid tight access cover by means of bolt fasteners and gaskets.

In order to connect the chamber to the underground tank, a mechanical fixing of some form was necessary. This took the form of a combination of screws, bolts, nuts, washers, O-ring seals or gaskets. The chamber was moved into position and then bolted into place in a fluid-tight manner. The actual process of fastening the bolts into place is a difficult and time-consuming operation. in order to obtain a sufficient seal a large number of bolts needed to be used and each one must be fitted and tightened individually by two people who must work in difficult conditions in situ.

To ensure a fluid-tight seal, a rubber O-ring seal was often inserted between a flange on the tank and a flange on the base section of the chamber, and the two components were compressed together by tightening the metal fasteners.

The means of sealing the tank and the base by using metal fasteners and a rubber O-ring seal has a number of disadvantages. Because of the size of the chambers it is difficult to manipulate the O-ring seal into position and to line up the boltholes.

Furthermore, rubber O-ring seals degrade over time and eventually will not be able to maintain the fluid-tight seal that is required for modern containment chambers. This degradation is accelerated where the O-ring is in contact with fuel vapour from the inside of the containment chamber and also moisture from the ground outside the containment chamber. Once the seal has degraded sufficiently it will need to be replaced. This is a difficult and expensive procedure as the containment chambers are often cemented into the ground and maintenance of the chamber would result in severe disruption to the forecourt operation.

In addition, there is no monitoring of the O-ring seals so the oil companies or operators have no way of knowing if or when they need replacing.

In an effort to provide a containment chamber which was easier to install and fabricate, two-piece containment chambers were introduced in the late 1980's.

One type of chamber was a two-piece sump construction with a base section and a height adjustable riser section. This design allowed easy access into the accessible base section before the upper riser section was installed and was also cheaper to manufacture and easier to transport and handle.

The upper section was sized in diameter to be stored inside the base section before installation of the containment chamber. The upper riser section was also capable of being cut to the required installed height. This height adjustability feature allowed for both deep and shallow tank burial depths. The problem with this two-piece design was that it introduced a new, additional sump connection joint which also had to be liquid tight.

Another type of design had a base and riser (or corbel) section and a lid section. This provided unhindered access into the chamber and was also cheaper to manufacture and easier to transport and handle than a onepiece chamber.

However, it also introduced an additional joint that had to be fluidtight.

The first polyethylene containment Bumps on the market did not have an effective means of sealing this joint. One such type of two-piece chamber required that the joint be sealed by means of speed tip welding. This thermo-plastic welding process required the use of a hot air gun fitted with a special tip on its nozzle which allowed a plastic polyethylene rod to be inserted through an opening in the tip, heated and then melted over the joint area.

This welding process proved in the field to be ineffective for untrained personnel. The speed of welding, surface preparation, moisture, and other factors resulted in poor welding applications leading to numerous leaks.

In early 1990 a new sump was introduced to the market, which introduced a mechanical means of sealing the upper/base joint by using metal fasteners and a rubber O-ring seal. This required the base of the riser section and the top of the base section to have two flanges with a series of spaced boltholes in both flanges.

The rubber O-ring seal was inserted between the bottom portion of the riser flange and the top portion of the base flange on the outside of the fasteners, and the two components were compressed together by tightening the metal fasteners.

However, this had all the disadvantages of the original one-piece containment chamber, in that the same difficult installation process needed to be 1, used, not just for the tank/base section but also for the base/upper section.

Currently, not all countries or bodies which govern the regulations concerning petroleum installations stipulate that these chambers must be double walled or include secondary containment. Since there is a considerable cost premium to provide secondary containment, at the present time manufacturers have to provide two different designs of chamber. One design has a single wall and the other design has two walls with a sealed interstitial space between the walls. This involves two sets of tooling, two separate production runs and two separate stock lines being held and monitored. This all results in a significant on-cost to the 1 0 customer.

It is an object of the present invention to overcome or at least mitigate some or all of these problems.

Summarv of the Invention According to one aspect of the present invention there is provided a method of forming a substantially fluid-tight seal between sections of a containment chamber system comprising: i) providing a first section of the containment chamber system, said first section incorporating an endless channel; ii) adding a sealing agent to said channel formed in the first section; iii) providing a second section of the containment chamber system, wherein a portion of the second system is adapted to nest in the endless channel of the first section; iv) inserting said part of the second section into the endless channel; v) allowing the sealing agent to set to form a substantially fluid-tight seal between the first section and the second section.

For the first time there is provided a method of sealing a containment chamber system without the need for mechanical fixings. In particular there is provided a method for sealing a containment chamber to a metal tank without the need for mechanical fixings.

Preferably when the containment chamber is a double walled chamber, and wherein in use, the sealing agent seals the opening between the two walls, forming an interstitial space.

The sealant plugs the entrance to the gap between the two walls of the second section. It effectively plugs the gap and seals the interstitial space. By doing this to both ends of the chamber, an interstitial space is formed. The sealant wells up around the base of the second section within the channel. It effectively seals on the outside of the walls of the second section and also between the walls (i.e. plugging the interstitial space) when a double walled chamber is used.

Advantageously the channel comprises engaging means to prevent the second section disengaging from the first section before the sealing agent has set.

Preferably the resilient means also provides additional strength to the join once the sealing agent has set. Optionally the engagement means are internal barbs along part or all of the channel wall(s). Preferably, the second section is a snap-fit into the first section.

According to a particularly preferred embodiment the first section comprises a collar on an underground tank and the second section comprises the base section of a containment chamber.

Advantageously the engagement means comprises barbs on both sides of the channel. Preferably when the containment chamber is a double walled chamber, the channel comprises engagement means to hold both walls. In order for both walls of the chamber to engage with the channel, a plug could be inserted between the walls to ensure that they maintain a certain distance from each other.

That way, when the walls engage the barbs on the walls of the channel, they cannot move inwardly and they are therefore held in place.

Preferably the base section is a tight sliding fit with the channel.

Particularly preferably, the containment chamber system further comprising: i) providing a third section of the containment chamber system, said third section incorporating an endless channel; ii) adding a sealing agent to said channel formed in the third section; iii) wherein the second section of the containment chamber system further comprises a portion adapted to nest in the endless channel of the third section; iv) inserting said part of the second section into the endless channel of the third section; v) allowing the sealing agent to set to form a substantially fluid-tight seal between the second section and the third section.

According to a particularly preferred embodiment the third section comprises a riser section of a containment chamber and the second section comprises the base section of a containment chamber. Therefore, not only can the base of the chamber be sealed to the top of the tank, the riser section can also be sealed to the base by the same method.

Preferably the channel of the third section is wide enough to accommodate a varying diameter of base section.

Preferably the containment chamber is a glass reinforced plastic chamber.

Alternatively the containment chamber is made from a thermoplastics material.

Preferably the sealing agent is selected from a resin or adhesive or substance that will bond or seal the first and second sections in a substantially fluid tight manner.

It will be appreciated that the present invention extends to a containment chamber system incorporating the above sealing method, to a method for forming a fluid-tight seal between a tank collar and a chamber base section, together with a method of forming a fluid-tight seal between a chamber base section and a chamber riser section as described herein, and to installations, including petroleum forecourt systems incorporating chambers according to the present invention.

According to a second aspect of the present invention there is provided a containment chamber assembly said assembly comprising: (i) an inner base chamber portion; (ii) an inner corbel portion; and optionally (iii) an outer base chamber portion; and (iv) an outer corbel portion; wherein the inner base chamber portion comprises a lip extending around substantially the entire upper circumference of the outer base portion, said lip being adapted to sealingly engage with the underside of a corresponding lip on the inner base portion.

This arrangement provides the advantage that a selection from the same components can be used to construct a single walled chamber or a double walled chamber as required. Currently approximately 80% of chambers sold are single walled, and would require only the inner components.

Preferably the lip in the outer base portion incorporates an endless groove or channel adapted to accommodate the circumferential edge of the outer corbel portion and/or the circumferential edge of the inner corbel portion, or both. This provides for maximum flexibility and allows the outer base portion to be used to construct a single walled chamber.

Preferably the assembly further comprises a first sealing means adapted to seal the assembly to a tank upstand.

Preferably the assembly is adapted such that the tank upstand is located, in use, between the inner and outer base chamber portions. This arrangement simplifies construction and naturally creates a discrete interstitial space.

In an alternative preferred embodiment the inner and outer base chambers comprise a substantially fluid-tight base. This creates a chamber suitable for use as a sump.

In one version the assembly is supplied with only one base chamber portion and one corbel portion, when a single walled chamber is required.

It will be appreciated that these two aspects of the invention may be used together or independently in the construction and assembly of a containment chamber.

According to a further aspect of the present invention there is provided a containment chamber comprising: (i) a base section, the lowermost-in-use region of said base section being adapted to engage with, and form a substantially fluid-tight seal with, a collar section of a tank; (ii) a riser section adapted to engage with, and form a substantially fluid tight seal with, an uppermost-in-use region of said base portion; wherein an endless channel or groove is provided associated with the interface between the base section and the riser section, said endless channel being adapted to contain a sealing agent adapted in use to form a fluid-tight seal between the two sections.

Preferably the endless channel forms an integral part of the riser portion.

In an alternative preferred arrangement the endless channel forms an integral part of the base portion.

Preferably said endless groove incorporates engagement means, said engagement means being adapted to prevent the base section and the riser section separating.

Preferably said engagement means comprises internal barbs along part or all of the walls of the channel.

Preferably the engagement means comprises a snap fit arrangement wherein the snap fit arrangement comprises one or more protrusions within the endless channel and one or more corresponding recesses on the base section/riser section, or vice versa.

Preferably the base section engages with a second substantially endless channel associated with the collar section of a tank, said second endless channel being adapted to contain a sealing agent.

Preferably the sealing agent comprises an adhesive.

Alternatively said sealing agent comprises a resin suitable for bonding GRP.

Preferably the base section and/or the riser section and/or both sections are of double skinned construction.

Preferably the base section comprises an inner base chamber and an outer base chamber, the inner base chamber being adapted to nest within the outer base chamber and to be bonded together in use using a sealing agent.

Preferably the riser section comprises an inner riser section and an outer riser section, the inner section being adapted to nest within the outer section and the two sections being bonded together using a sealing agent.

Preferably the engagement means is adapted to prevent both inner and outer skins from separating.

Preferably said endless channel is sufficiently broad to allow the riser section to be trimmed in height yet still fit within the channel.

Preferably both the inner base chamber and the outer base chamber incorporate endless channels such that the inner base chamber or the outer base chamber can be used either alone or in combination in the construction of a containment chamber.

Preferably the base section is substantially cylindrical in cross-section.

Preferably the base section is polygonal in cross-section.

Alternatively the base section is substantially circular cylindrical in cross section.

According to a further embodiment there is provided a method of forming a substantially fluid-tight containment chamber system, said method comprising the steps of: (i) providing a base section, the lowermost-in-use region of said base section being adapted to engage with, and form a substantially fluid tight seal with, a collar section of a tank; (ii) providing a riser section adapted to engage with, and form a substantially fluid-tight seal with, an uppermost-in-use region of said base portion, wherein an endless channel or groove is provided associated with the interface between the base section and the riser section, said endless channel being adapted to contain a sealing agent adapted in use to form a fluid-tight seal between the two sections; (iii) adding a sealing agent to said endless channel; (iv) engaging the base section with the riser section such that they nest together in the endless channel; (v) allowing the sealing agent to set to form a substantially fluid-tight seal between the base section and the riser section.

Preferably the endless channel forms an integral part of the riser portion.

Alternatively the endless channel forms an integral part of the base portion.

Preferably said endless groove incorporates engagement means, said engagement means being adapted to prevent the base section and the riser section 1 5 separating.

In an alternative preferred arrangement the engagement means comprises a snap fit arrangement, wherein the snap fit arrangement comprises one or more protrusions within the endless channel and one or more corresponding recesses on the base section/riser section, or vice versa.

Preferably the base section engages with a second substantially endless channel associated with the collar section of a tank, said second endless channel being adapted to contain a sealing agent, said method incorporating the steps of adding a sealing agent to the second channel, inserting the base section into the channel, and allowing the sealing agent to set.

Preferably the sealing agent comprises an adhesive.

Alternatively said sealing agent comprises a resin suitable for bonding GRP.

Preferably the base section is substantially cylindrical in cross-section.

Preferably the base section is polygonal in cross-section.

Alternatively the base section is substantially circular cylindrical in cross- section.

Brief Description of the Drawings

The present invention will now be described, by way of examples only, with reference to the accompany drawings wherein: Figure 1 is a partially cut-away side view of part of a petroleum forecourt installation, which includes a tank having a manhole chamber, and a pair of dispensing pumps having containment chambers, the chambers in accordance with the invention; Figure 2 illustrates a cut-away side view of a containment chamber according to one embodiment of the present invention; Figure 3 illustrates a cut-away side view of a channel according to one embodiment of the present invention; Figure 4 illustrates a cut-away side view of a channel with a double walled chamber according to one embodiment of the present invention; Figure 5 illustrates a cut-away view of a containment chamber according to a further embodiment of the invention; Figure 6 illustrates an expanded view of a containment chamber assembly according to a second aspect of the present invention showing inner and outer base chamber portions and inner and outer corbel portions; Figure 7 shows in diagrammatic format and not to scale a cross-section of the base portionof Figure 7 once assembled; Figure 8 illustrated and alternative lip arrangement for the outer base chamber portion.

Description of the Preferred Embodiments

The present embodiments represent currently the best ways known to the applicant of putting the invention into practice. But they are not the only ways in which this can be achieved. They are illustrated, and they will now be described, by way of example only. By way of terminology used in this document the following definitions apply: Containment chamber any receptacle designed to keep a fluid in or out. This includes, but is not limited to, access manhole and sump chambers as described herein. It also includes tanks in general.

Containment chamber system - any part of the underground system, including the containment chamber, that is contained by, or attached to the containment chamber.

This includes the access chamber itself, corbel, frame neck or lid together with the underground tank, collar, manway and associated pipework.

Energy transfer means - a generic term describing any form of energy source.

Typically it takes the form of a resistance winding which heats up when an electrical current is passed through it. The term also encompasses other welding techniques including ultrasonic welding and induction welding.

Flange - any collar suitable for attaching the various sections of the containment chamber. In the examples given the surface of the flanges are substantially planar.

However, it will be understood that the flange must conform to the profile of the section to which it is to be joined. Thus the flange can adopt any suitable conformation to achieve the necessary contact with a flat or curved surface.

Fluid - whilst the examples provided relate mainly to liquids, the term fluid refers to liquids, vapours and gases. For example, should a leak occur in a secondarily contained pipe in a garage forecourt installation then petrol or petrol vapour will collect in the manhole chamber. It is essential that this petrol vapour cannot escape through the wall of the chamber and into the surrounding ground.

Pipe - where pipes are referred to herein they are generally of circular cross- section. However, the term also covers other cross-sections such as box sections, corrugated and the like and secondarily contained pipes of the "pipe-within-a-pipe" type.

Glass reinforced plastic (GRP) - The term GRP has a very broad meaning in this context. It is intended to encompass any fibre-reinforced plastic wherein a fibre of any type is used to strengthen a thermosetting resin or other plastics material.

Fusible material - The term fusible material has a very broad meaning in this context. It is intended to encompass any polymeric material which when energy is applied to it can melt and fuse together with an adjacent material and is intended to cover thermoplastics, thermosets, elastomers and adhesives.

Plastics Material - The term has a very broad meaning in this context and is intended to encompass any polymeric material including thermoplastics, thermosets, elastomeric or any other polymeric material.

The petroleum forecourt installation shown in Figure 1 comprises a pair of dispensing pumps 10 and 11 connected to a subterranean tank 12 through a pipeline 13. The pipeline 13 is formed from contiguously arranged sections of polyethylene pipe. The pipeline 13 extends from the pumps 10 and 11 through the containment chambers 14 and 15 having side walls 16 and bases 17 into a containment chamber 18 having a side wall 19 and a base 1 immediately above the tank 12.

Figure 1 shows two lines extending from the pipeline 13 into the tank 12.

These lines relate to two alternative forms of fuel supply system and are both shown for the sake of completeness. In practice, only one of the lines would extend from the pipeline 13 into the manhole chamber 18. One of those lines is a suction line 2 which is used where the dispensing pumps 10 and 11 are fitted with suction pumps.

The alternative line, reference 3, is a pressure line connected to the pipeline 13 via a pump 4 which is operable to propel fuel from the tank 12 to the pumps 10 and 11.

It can be seen from Figure 1 that the walls 16 and 19 have to be apertured in order to allow the pipeline 13 to pass into the chambers. In order to prevent water leaking from the surrounding ground (here denoted by reference numeral 5) into the chambers 14, 15 and 18 through the aperture, the pipe is sealed to the walls 16 and 19 by means of a fitting. In the event of a spillage or a leak in a supply pipe the seal also prevents fuel from escaping into the environment.

Figure 2 shows a containment chamber system according to one embodiment of the present invention. It shows an underground tank 20, which is typically made of steel or glass reinforced plastic (GRP) having a collar section 21 fixed to the top of it. Within the collar section 21, is a manway 22, which permits access to the interior of the tank. The collar 21 has a channel 23 running around its perimeter. The collar 21 is typically cylindrical and the channel 23 extends radially outwards and upwards from the collar. The collar need not be strictly cylindrical, in that the cross-section need not be uniform along its length. The important feature is the endless channel or groove, which extends around the upper perimeter of the channel. The channel 23 can be seen more clearly in figure 3, which shows a cut away portion of the collar 21 and the channel 23. The channel can either be an integral part of the collar or alternatively be fixed to the collar.

The containment chamber 24 comprises a base section 25 and a riser/corbel section 26. The base section 25 is formed with a downwardly extending region 27, which is shaped in a complementary manner such that it can be inserted, or pushed, into the channel 23. The shape of the downwardly extending region will depend on the shape of the collar and/or channel. The downwardly extending region 27 and the channel 23 are shaped such that a portion of the region 27 can fit inside it.

The channel further comprises engagement means to hold the downwardly extending region in position 28. This can be either barbs or some form of snap lock arrangement, for example protrusions on the channel and corresponding recesses on the downwardly extending region whereby the protrusions are resiliently formed such that once the downwardly extending region is in position it cannot easily be removed again.

In order to form the seal, a sealing material 29, for example a resin or adhesive is poured into the channel. The downwardly extending region 27 is then pushed into position in the channel. Gravity puts downward pressure on the base and the sealing material 28 sets to form a fluid- tight seal. The sealing material 29 will also push up around the channel to form a fluid-tight region, which prevents fluids from entering or leaving the channel.

The sealing material 29 will also hold the base in position. This can be assisted by the barbs or snap lock arrangement 28. The combination of both features provides a strong bond, which cannot easily be broken. It may be possible to form a strong enough bond from the barbs alone but it is the sealing material 29 that forms the fluid-tight seal between the sections.

Figure 4 shows an arrangement with a double walled chamber. Generally, this type of chamber is formed from two separate chambers (see below), one inside the other and not connected together. The downwardly extending regions of the inner and outer chambers can be seen as inner wall 30 and outer wall 31 in figure 4.

In this arrangement, only the inner wall 30 is caught by the barbs 28. As can be seen, the outer wall 31 is prevented from being removed from the channel by the inner wall 30. The flat portions of the base on the inner wall 30 will prevent upward movement. Thus, by holding the inner wall in position by the barbs 28, both the inner and outer chambers are prevented from moving.

When both chambers are pushed into the channel containing sealing material, part of the material is forced between the two walls. This effectively seals the gap between the two chambers and forms an interstitial space (provided that the l upper sections of the two chambers are also sealed. The interstitial space can then be monitored via standard monitoring techniques.

The channel can be designed such that it is a sliding fit with either a double walled chamber or alternatively, a single walled chamber. This way, a better seal will be formed between the collar and the base.

It is of course possible to have the channel attached to any part of the tank to form an effective fluid-tight region in the containment chamber.

The walls of the channel and/or downwardly extending region can contain protrusions or recesses that the sealing material can flow into whilst it is substantially in a liquid phase. Once it is set however, it will prevent movement of the base section out of the channel.

This type of sealing method is also applicable between the base section 25 and the riser section 26. In order to manufacture the base section, the walls 32 taper outwards. This allows the base section to be formed in a mould and then subsequently removed. When the base section is installed in situ, it generally has to be cut to the required height. This will depend on the distance from ground level to the top of the tank. Therefore, because the walls 32 taper outwards the diameter of the base section will vary depending on its height.

This means that the channel 33 in the riser section 26 needs to be wide enough to accommodate either a very tall base section where the diameter will be wide, or a small base section, where the diameter will be narrower. Thus, the tight fit of the collar/base channel will not always be applicable for the base/riser joint.

Additionally, the barbs used in the channel 23 may not be applicable, as the position of the wall 32 in the channel 33 will depend on the height of the wall 32.

In order to fix the riser 26 onto the base 25, the riser 26 is first turned upside down and sealing material is poured into the channel 33. The sealing material is designed to be thick or viscous enough so that when the riser 26 is turned the right way up, the sealing material does not pour out. The riser section is then pushed onto the upstanding walls of the base section and held in position until a fluid-tight seal is formed. Again, engagement means such as barbs, protrusions or recesses can be provided to enhance the strength of the bond.

By sealing both the top and the bottom of the base section of a double walled chamber, an interstitial space is formed that can be monitored.

The base section can be formed from any geometric cross-section, for example circular, rectangular or square but a polygonal shape such as an octagonal cross-section is often used in practice although this invention is in no way limited to containment chambers of any particular crosssection. The channel will correspond to the shape of the base section.

As explained above, gravity will assist in holding the sections in place but it is also envisaged that temporary or permanent clamps will be used to hold the base and the riser section in place.

The choice of sealing material will depend on the material chosen for the containment chamber and will be determined by the materials specialist. New adhesives are continually being developed and this invention is intended to encompass both known and yet to be developed adhesives and sealing materials.

For example a resin suitable for bonding GRP may be chosen in a GRP chamber arrangement but an adhesive suitable for bonding a plastics material may be necessary in a thermoplastic chamber arrangement.

A further embodiment is illustrated in Figure 5. This illustrates an embodiment in which the sealing groove or channel 123 on the tank collar is now internal to, rather than external of, the tank collar itself. This arrangement means that the majority of the sealant and the sealing region is internal to the chamber, and thus protected from the inhospitable external environment.

A further difference relates to the shape, configuration and location of the channel 133 into which the riser section 126 now nests. In this embodiment that channel is located around the perimeter of the upper edge of the base section 125.

This arrangement means that it is easier to fill this channel with sealant or bonding agent during assembly. As described above the channel is wide enough to allow the riser section 126 to be trimmed in height as necessary.

Figure 6 shows a schematic exploded view of a containment chamber assembly 30 according to a second aspect of the invention. The assembly comprises an outer chamber base portion 231, an inner chamber base portion 232, an outer corbel portion 233 and an inner corbel portion 234. Thus far the arrangement is similar to known double skinned or secondary contained chambers.

However, in this invention the same components can be used to create either a single skinned or double skinned chamber. Thus, referring to Figures 7 and 8, it will be seen that, during construction, and usually on site, a sealing means 240 is applied and sealed to the tank upstand 243. In this example the sealing means comprises an inner 241 and an outer 242 tank seal, applied to the inner and outer face of the tank upstand 243 to create an endless channel around the top of the tank upstand. However, a channel arrangement around the top of the tank upstand, as shown in Figures 2 to 5 and as described above, could equally well be provided.

The end result is that an endless groove or channel is provided around the top of the tank upstand, which is adapted to accommodate the bottom of the chamber base, be it of primary or secondary construction.

If a single walled chamber is required an inner base chamber portion 245 is inserted into the tank sealing means and embedded in sealant or resin to form a fluid-tight seal. The uppermost-in-use edge of the inner base chamber portion incorporates a lip or flange 248 which extends substantially around the entire upper, outer circumference of the base chamber portion. This lip/flange in turn incorporates an endless groove 249 designed to accommodate, and form a substantially fluid-tight seal with, a corbel portion. So to complete this form of construction, the endless groove 249 is filled with sealanVresin and a corbel portion inserted until a substantially fluid-tight seal has formed between the two components. In this regard, channel/groove 249 may be similar in its form and function to channel 133 described above.

However, a major advantage of this invention is that the same components may be used to construct a double walled chamber. In this case, having applied a sealing means 240 to the tank upstand as described above, an outer base chamber portion is first inserted into the tank sealing means. The uppermost-in-use edge of the outer base chamber also incorporates a lip or flange 258. The upper surface of the lip/flange 258 is adapted to be sealed to the underside surface of lip/flange 248 using a sealant or resin. Once a substantially fluid-tight seal has formed between the two, then this part of the construction is complete.

It will be seen from Figure 7 that the inner and outer base chamber portions sit either side of the tank upstand. The interstitial space between the inner and outer base chamber portions may be filed with brine or glycol antifreeze or may be placed under a vacuum. In any event, the status of this interstitial space may be monitored using conventional means.

Figure 8 illustrates an assembly in which the lip of the outer base chamber portion has a slightly different configuration. In this case the lip 458 also incorporates an endless groove 459 adapted to accommodate an inner corbel portion or an outer corbel portion or both. Other components in Figure 8 are numbered using a numbering system corresponding to that used in Figure 3.

It will be appreciated that a number of different types of sealing means can be used around the tank upstand. It could be supplied with an endless groove around its upper edge. Or a flange connector could be used, including a bolted flange-type connector. t

It will also be appreciated that different types of sealing and jointing arrangements can be used at the top edge of the base chamber portions. However, an essential part of the invention is that part of the inner base chamber portion is adapted to form a seal with the outer base chamber portion as well as forming a seal with a corbel portion.

The present invention, in both its aspects, is suitable for providing fluid-tight seals in chambers made of metal, GRP, a plastics material or any other material that can be bonded with some form of adhesive.

The containment chamber assembly can be manufactured from a variety of materials as selected by the materials specialist. Preferably the base section and the riser section are formed from the same material. By way of examples only suitable plastics materials may be selected from the group comprising: polyethylene; polypropylene; polyvinyl chloride; polybutylene polyurethanes; polyamides, including polyamides 6, 6.6, 6.10, 6.12, 11 and 12; polyethylene terphthalate; polybutylene terephthalate; polyphenylene sulphide; polyoxymethylene (acetal); ethylene/vinyl alcohol copolymers; polyvinylidene fluoride (PVDF) and copolymers; polyvinyl fluoride (PVF); tetrafluoroethylene-ethylene copolymer (ETFE); tetrafluoroethylene-hexafluroethylene copolymers (PEP) ethylene tetrafluoroethylene hexafluropropylene terpolymers (EFEP) terpolymers of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride (THV); polyhexafluoropropylene; polytetrafluoroethylene (PTFE); polychlorotrifluoroethylene; polychlorotrifluoroethylene (PCTFE); fluorinated polyethylene; fluorinated polypropylene; and blends and copolymers thereof. Furthermore, it is known to use blends of two or more polymers and this invention extends to cover known and yet to be developed blends of plastics material.

Alternatively the chamber components may be formed from glass reinforced plastic (GRP) or fibre reinforced plastic.

Alternatively the chamber components may be formed from metal, for example steel or a coated metal.

This selection is not intended to be limiting but rather demonstrates the flexibility and breadth of the invention.

The GRP resin component can be formed from any suitable thermosetting resin as selected by the materials specialist, including but not limited to polyester or epoxy resins. The present invention also extends to moulding methods yet to be discovered.

The examples described above relate principally to containment chambers.

However, the sealing or construction method is equally applicable to other forms of chambers or joins between two components where the components are to be held in place and a substantially fluid-tight seal is required.

The sealing material chosen will be one which provides the strongest joint and also with the lowest permeability to the fluid in question. The sealing material could be a compound, resin, adhesive, sealing agent or substance that will bond or seal the two parts together in a watertight way.

A major advantage of this invention is that it allows chambers of any material to be attached to steel tanks in a water tight fashion with no mechanical fixing in that there are no screws, bolts, nuts, washers or gaskets. t

Claims

1. A containment chamber comprising: (i) a base section, the lowermost-in-use region of said base section being adapted to engage with, and form a substantially fluid-tight seal with, a collar section of a tank; (ii) a riser section adapted to engage with, and form a substantially fluid tight seal with, an uppermost-in-use region of said base portion; wherein an endless channel or groove is provided associated with the interface between the base section and the riser section, said endless channel being adapted to contain a sealing agent adapted in use to form a fluid-tight seal between the two sections.

2. A containment chamber as claimed in Claim 1 wherein the endless channel forms an integral part of the riser portion.

3. A containment chamber as claimed in Claim 1 wherein the endless channel forms an integral part of the base portion.

4. A containment chamber as claimed in any preceding claim wherein said endless groove incorporates engagement means, said engagement means being adapted to prevent the base section and the riser section separating.

5. A containment chamber according to Claim 4 wherein said engagement means comprises internal barbs along part or all of the walls of the channel.

6. A containment chamber according to Claim 4 or Claim 5 wherein the engagement means comprises a snap fit arrangement.

7. A containment chamber according to Claim 6 wherein the snap fit arrangement comprises one or more protrusions within the endless channel and one or more corresponding recesses on the base section/riser section, or vice versa.

8. A containment chamber as claimed in any preceding claim wherein the base section engages with a second substantially endless channel associated with the collar section of a tank, said second endless channel being adapted to contain a sealing agent.

9. A containment chamber as claimed in any preceding claim wherein the sealing agent comprises an adhesive.

10. A containment chamber as claimed in any preceding claim wherein said sealing agent comprises a resin suitable for bonding GRP.

11. A containment chamber as claimed in any preceding claim wherein the base section and/or the riser section and/or both sections are of double skinned construction.

12. A containment chamber as claimed in Claim 11 wherein the base section comprises an inner base chamber and an outer base chamber, the inner base chamber being adapted to nest within the outer base chamber and to be bonded together in use using a sealing agent.

13. A containment chamber as claimed in Claim 11 or Claim 12 wherein the riser section comprises an inner riser section and an outer riser section, the inner section being adapted to nest within the outer section and the two sections being bonded together using a sealing agent.

14. A containment chamber as claimed in any of Claims 11 to 13 inclusive when dependent on Claim 4 wherein the engagement means is adapted to prevent both inner and outer skins from separating.

15. A containment chamber as claimed in Claim 3 and any of Claims 4 to 14 when dependent on Claim 3, wherein said endless channel is sufficiently broad to allow the riser section to be trimmed in height yet still fit within the channel.

16. A containment chamber as claimed in Claim 12 wherein both the inner base chamber and the outer base chamber incorporate endless channels such that the inner base chamber or the outer base chamber can be used either alone or in combination in the construction of a containment chamber.

17. A containment chamber as claimed in any preceding claim wherein the base section is substantially cylindrical in cross-section.

18. A containment chamber as claimed in Claim 17 wherein the base section is polygonal in cross-section.

19. A containment chamber as claimed in Claim 17 wherein the base section is substantially circular cylindrical in cross-section.

20. A containment chamber substantially as herein described, with reference to and as illustrated in any combination of the accompanying drawings.

21. A method of forming a substantially fluid-tight containment chamber system, said method comprising the steps of: (i) providing a base section, the lowermost-in-use region of said base section being adapted to engage with, and form a substantially fluid tight seal with, a collar section of a tank; (ii) providing a riser section adapted to engage with, and form a substantially fluid-tight seal with, an uppermost-in-use region of said base portion, wherein an endless channel or groove is provided associated with the interface between the base section and the riser section, said endless channel being adapted to contain a sealing agent adapted in use to form a fluid-tight seal between the two sections; (iii) adding a sealing agent to said endless channel; (iv) engaging the base section with the riser section such that they nest together in the endless channel; (v) allowing the sealing agent to set to form a substantially fluid-tight seal between the base section and the riser section.

22. A method as claimed in Claim 21 wherein the endless channel forms an integral part of the riser portion.

23. A method as claimed in Claim 21 wherein the endless channel forms an integral part of the base portion.

24. A method as claimed in any of Claims 21 to 23 inclusive wherein said endless groove incorporates engagement means, said engagement means being adapted to prevent the base section and the riser section separating.

25. A method according to Claim 24 wherein said engagement means comprises internal barbs along part or all of the walls of the channel.

26. A method according to Claim 24 or Claim 25 wherein the engagement means comprises a snap fit arrangement.

27. A method according to Claim 26 wherein the snap fit arrangement comprises one or more protrusions within the endless channel and one or more corresponding recesses on the base section/riser section, or vice versa.

28. A method as claimed in any of Claims 21 to 27 inclusive wherein the base section engages with a second substantially endless channel associated with the collar section of a tank, said second endless channel being adapted to contain a sealing agent, said method incorporating the steps of adding a sealing agent to the second channel, inserting the base section into the channel, and allowing the sealing agent to set.

29. A method as claimed in any of Claims 21 to 28 inclusive wherein the sealing agent comprises an adhesive.

30. A method as claimed in any of Claims 21 to 29 inclusive wherein said sealing agent comprises a resin suitable for bonding GRP.

31. A method as claimed in any of Claims 21 to 30 inclusive wherein the base section and/or the riser section and/or both sections are of double skinned construction.

32. A method as claimed in Claim 31 wherein the base section comprises an inner base chamber and an outer base chamber, the inner base chamber being adapted to nest within the outer base chamber and to be bonded together in use using a sealing agent.

33. A method as claimed in Claim 31 or Claim 32 wherein the riser section comprises an inner riser section and an outer riser section, the inner section being adapted to nest within the outer section and the two sections being bonded together using a sealing agent.

34. A method as claimed in any of Claims 31 to 33 inclusive when dependent on Claim 24 wherein the engagement means is adapted to prevent both inner and outer skins from separating.

35. A containment chamber as claimed in Claim 23 and any of Claims 24 to 34 when dependent on Claim 23, wherein said endless channel is sufficiently broad to allow the riser section to be trimmed in height yet still fit within the channel.

36. A method as claimed in Claim 32 wherein both the inner base chamber and the outer base chamber incorporate endless channels such that the inner base chamber or the outer base chamber can be used either alone or in combination in the construction of a containment chamber.

37. A method as claimed in any of Claims 21 to 36 inclusive wherein the base section is substantially cylindrical in cross-section.

38. A method as claimed in Claim 37 wherein the base section is polygonal in cross-section.

39. A method as claimed in Claim 37 wherein the base section is substantially circular cylindrical in cross-section.

40. A method of forming a substantially fluid-tight containment chamber system substantially as herein described, with reference to and as illustrated in any combination of the accompanying drawings.