GB2407795A

GB2407795A - Electrofusion bonding

Info

Publication number: GB2407795A
Application number: GB0426600A
Authority: GB
Inventors: John Alexandre Boudry; Christopher Richard Wise
Original assignee: Petrotechnik Ltd
Current assignee: Petrotechnik Ltd
Priority date: 2003-12-05
Filing date: 2004-12-06
Publication date: 2005-05-11
Also published as: EP1691968A1; WO2005053936A1; GB0426600D0

Abstract

Disclosed are four separate inventions. The first being a bonding method comprising the use of an electrofusion tape. The second being a bonding method comprising the use of a sheathed electrofusion wire, broadly shown in fig 11. The third being a bonding method comprising the use of a electrofusion sleeve, such as capable of receiving components to be joined. The fourth being directed at the bonding of specific containment chamber arrangement for which the bonding is not specified, broadly shown in fig.4.

Description

SEALING ELEMENT AND METHOD

Field of the Invention

The present invention relates to a sealing element and to a sealing method for joining two components in a fluid-tight fashion. It is particularly applicable to the electrofusion of two components together. It is also applicable to a method and apparatus for constructing plastics articles such as containment chamber assemblies such as sumps.

Background to the Invention

Electrofusion finings and electrofusion couplings are widely used in a variety of applications. One such application involves the subterranean piping systems of the type that are typically installed at service stations to communicate fuel or chemicals between an underground storage tank and an above ground dispensing station. The underground storage tanks and associated piping pose serious potential environmental and fire hazards as the chemicals contained therein could and have in the past leaked into the earth.

Oil companies have been and remain under considerable pressure to ensure that environmental concerns are given priority in the planning and installation of petrol station infrastructures. This has not been without significant on-cost. One important advancement has been the use of pipeline systems constructed from plastics materials which have enabled the oil companies to install cost-effective environmentally acceptable alternatives to steel pipework systems which tend to corrode over time.

In recent years there has been an increasing awareness that 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.

Secondary containment involves containing each fuel supply pipeline in a respective secondary containment pipeline which is optionally sealed at its ends to the fuel supply pipeline. The secondary containment pipeline prevents leaks from the fuel supply pipeline from being discharged into the environment, and also can convey leaked petrol to a remote-sensing device. Typically, the pipes forming the secondary containment pipeline are initially separate from the fuel pipes and are sleeved over the latter as the fuel pipes are installed between the fuel storage tanks and dispensing pumps.

Whilst every effort is made to avoid having joints in underground pipelines, other than inside manhole chambers, these joints sometimes cannot be avoided. Such joints are conventionally made using special purpose built fittings and the connections are made by electrofusion welding. Electrofusion fittings used in this application are fairly typical of their class. The problems and shortcomings of this type of fitting are also common.

In conventional single containment plastic piping systems, successive lengths of plastic pipe are joined end to end using so called electrofusion couplings, sockets or welding muffs, which typically comprise short plastic sleeves providing sockets at either end having internal diameters of a size to receive the ends of the respective pipes as a close fit and incorporating electrical resistance heating windings. Thus, two adjoining pipe lengths can be connected end to end by inserting the adjoining pipe ends into such an electrofusion coupling from opposite ends thereafter passing electric current through the heating windings in order to fuse the internal surfaces of the electrofusion coupling and the adjacent external surfaces of the inserted pipe ends, thereby welding the pipe ends to the electrofusion coupling to form a fluid tight joint.

These electrofusion couplings, which are known per se, are specially manufactured fittings which are designed to mate with two components, for example two pipe ends, which are to be joined together. An electrical heating element or elements are set into the inner surface of the coupling and when current is passed through the heating element in the assembled coupling joint it melts the inner surface of the fitting itself and the outer surface of the component(s) placed inside it to fuse the components together.

Whilst this arrangement is tried and tested, and finds use in a wide range of applications, it has a number of disadvantages. Firstly, the heating element must be positioned in the inner surface of what is usually a complex shaped component. This may be done using patented technology, with the inevitable cost implication, or by a multi-stage construction process. In either case the result is that these fittings are relatively expensive to manufacture.

Secondly, a separate and individually designed fitting is required for each application. Thus different sizes of pipe require a suite of different fittings. In addition, a complete range of elbow joints, Tfittings and the like are needed for each pipe size.

These are expensive to manufacture and considerable stocks must be held to ensure prompt delivery of the right fitting(s). This in turn has a significant cost associated with it.

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

Typically, secondary containment systems have included access Bumps which are an offshoot from the so-called back fill retainer. There are a variety of Bumps now on the market usually comprising a base defining an enlarged chamber, a riser of smaller diameter connected to the base 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.

As explained above, 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 Bumps or chambers. Containment sumps are typically found at fuel service stations whereby they are installed below the surface to 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 Bumps which are similar in purpose but different in design. The first type is commonly referred to as a "tank sump" 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 Bumps 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 Bumps 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.

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 enclosures located at the tank and under the dispensing units provide a means of secondary containment for part of the entire system.

These access enclosures should be of such a design that they are liquid tight preventing ground and surface water from entering the enclosure, and preventing any leaking product escaping from the enclosure 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 sump and provide a means for forming liquid tight and secure connections to the tank and dispensing island.

There are a variety of sumps now on the market usually comprising a base defining an enlarged chamber, a riser connected to the base having a smaller diameter than the base at the top of the riser 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.

These sumps have been made from a variety of materials including metal containers made of coated steel or non-corrodible fibreglass material. The Bumps 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 sump 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 hermetic sump 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 sumps 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 the materials used and 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. Sumps made of coated steel were unpopular because of their potential to fail due to corrosion over time.

The sumps made of rigid fibreglass and steel achieved limited success in providing a liquid tight access cover by means of bolt fasteners and gaskets.

In an effort to provide a containment sump which was easier to install and fabricate, polyethylene containment sumps were introduced in the late 1 980's.

These sumps were of a two-piece 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 riser 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 base/riser design was that it introduced a new, additional sump connection joint which also had to be liquid tight.

The first polyethylene containment sumps on the market did not have an effective means of sealing the base/riser joint. One such type of twopiece sump required that the joint where the riser section made contact with the base section 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 to solve the riser/base sealing process. This new sump introduced a mechanical means of sealing the riser/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.

The means of sealing the riser 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. 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.

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.

Furthermore 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.

Accordingly, it is an object of the present invention to overcome or mitigate some or all of the problems outlined above.

Summary of the Invention

According to a first aspect of the present invention there is provided a method of forming an electrofusion seal between a first component and a second component comprising the steps of: (a) providing a first component incorporating a region formed from an electrofusible plastics material; (b) providing a second component incorporating a region formed from an electrofusible plastics material, the first and second components being adapted to mate together in a mating region; (c) providing a separate sealing element, said sealing element incorporating energy transfer means, said energy transfer means being adapted to cause, in use, the first component, the second component and the sealing element to fuse or bond together; (d) applying energy to the energy transfer means to fuse or bond the first component to the second component.

By providing a separate sealing element it is no longer necessary to go to the expense of embedding the energy transfer means into one or other of the components.

This represents a considerable cost saving as well as providing increased flexibility on what type of components can be electrofusion welded.

Preferably the sealing element comprises a flexible band or tape the body of which is formed from an electrofusible plastics material. By forming the sealing element as a flexible unit it can be used to bond a variety of shapes and configuration of components together and need not be purpose designed for each application.

Preferably the sealing element is in the form of a band or tape which may be cut to length to correspond with the size/length of the mating region between the first and second components. This further increases the flexibility of the application and the tape can be trimmed off around the heating elements in order to connect them to a current supply.

In an alternative embodiment the sealing element comprises a pre-formed unit adapted to conform to the shape and configuration of the mating region between the first and second components. This arrangement ensures that all three components are a good mating fit.

Preferably the sealing element further comprises electrical terminal means.

According to a second aspect of the present invention there is provided a sealing element adapted to form an electrofusion seal between a first component and a second component, said components being adapted to mate together in a mating region, said sealing element incorporating energy transfer means, the energy transfer means being adapted to cause in use the first component and the second component to fuse or bond together in order to form a substantially fluid-tight seal there between.

Preferably the sealing element comprises a fusible material which, when heated via the energy transfer means, at least partially melts, causing the first component and the second component to fuse or bond together. The two components and the sealing element effectively fuse together to become a single unit.

Preferably the body of the sealing element is formed from a plastics material compatible to bond or fuse to the mating regions of the first and second components.

In a particularly preferred embodiment the energy transfer means comprises an electrical heating wire that is embedded within the body of the sealing component.

Preferably the sealing element is in the form of a band or tape.

Alternatively the sealing element is in the form of an electrical heating wire coated with an electrofusible material. Thus, the element can be made very economically as a coated wire. This is easy to manufacture and allows the wire to be stripped accurately.

Especially, the sealing element is from a strand of electrical heating wire coated with an electrofusible material.

Preferably, when coated the wire sealing element has a rectangular cross section, when viewed in a plane perpendicular to the longitudinal axis of the wire. This has a number of advantages. The height and width of the coating can be controlled to ensure that the wire is a predetermined distance from the components and from adjacent wire(s). Furthermore, when wrapping the wire around a component, for example a pipe, the rectangular cross section allows the successive loops to be easily laid adjacent to the previous loop. This ensures that the wires are a predetermined distance from each other to prevent them from shorting whilst the element is fusing. In addition, the wires can easily be arranged, with a number of loops laid together effectively forming a band with a single wire running through it. By passing a heat source over the top of the wires, the successive loops can be fused together, forming what amounts to a single tape.

Other cross sections can be envisaged, and are encompassed by the present invention, including square, circular or any other shape. It is particularly preferred when the width of coating is greater than the diameter of the wire. In essence any cross section can be used.

With a rectangular cross section, the longer edge can lay flat against the component, with the shorter edges of success loops of wire, abutting each other.

Preferably the band or tape is adapted to be cut to length to correspond with the size/length of the mating region between the first and second components. This is particularly advantageous because the sealing element can be manufactured and sold in a roll, from which pieces are cut to the required length. This represents a considerable cost saving as well as being more convenient.

Preferably the heating element comprises an electrical heating wire, the end of the tape being trimmable to expose the ends of the heating wire such that the heating wire can be connected to a current supply in use.

In an alternative embodiment the sealing element comprises a pre-formed unit adapted to conform to the shape and configuration of the mating region between the first and second components.

Preferably the sealing element further comprises electrical terminals for connecting the heating element to a current supply.

Preferably the sealing element comprises a tubular sleeve. A sleeve is particularly convenient for fusing together components where the mating region is cylindrical in shape, such as a pipe or a pipe fitting.

The present invention also extends to include components that have been fused together using the method or a sealing element according to the present invention. It therefore extends to include an apparatus comprising a first component and a second component, said first and second components being joined to each other in a substantially fluid- tight fashion by a sealing element or using a method as claimed herein.

The present invention is particularly applicable in subterranean pipework systems for fusing or welding together pipes, pipework fitting and Bumps/ chambers or combinations thereof.

One example of the sealing element and method is shown according to a second aspect of the invention there is provided a containment chamber assembly comprising: (i) a hollow base section having a bottom wall, an upstanding side wall and a first circumferentially extending base flange at the upper edge of the side wall; (ii) an elongated generally tubular riser section having a second circumferentially extending riser flange at its lower terminal edge adopted to confront and overlay the base flange; and (iii) optionally a cover mounted over the upper end of the riser; characterized in that the containment chamber assembly further comprises an energy transfer means, said energy transfer means being adapted to cause in use the base section and the riser section to fuse or bond together in order to form a substantially fluid-tight seal there between.

Preferably the energy transfer means is located in a sealing ring section adapted to fit between the two flanges.

Alternatively, the energy transfer means can be located in either the first base flange or the second riser flange or alternatively in both.

Preferably the section incorporating the energy transfer means comprises a fusible material which, when heated via the energy transfer means, at least partially melts, causing the base and the riser to be fused together.

More preferably the energy transfer means comprises conduction means for conducting an electric current, said conduction means in use, being heated by the current, to cause heating of the energy transfer means and the adjacent surfaces with which it is in contact.

Preferably the base section and the riser section are formed from the same electrofusible material.

In a particularly preferred embodiment the sealing ring section comprises a heating element, or a series of heating elements, set into a band of electrofusible material. Preferably the electrofusible material in the band is the same material from which the base and riser sections are made or alternatively is a material compatible to bond or fuse to the box and riser sections.

Preferably the adhesive is selected from a thermoplastic, thermoses, cross- linking or pressure sensitive adhesive.

Preferably the energy transfer means comprises a heating wire.

Preferably the section incorporating the energy transfer means also incorporates terminals for connecting the energy transfer means to a current supply.

Preferably there is a plurality of terminals and each set of terminals connects a separate section of the energy transfer means to a current supply. Although the terminals connect different regions the terminals can all be wired so that they all terminate in the same place and can optionally be colour coded to highlight which terminal corresponds to which region.

Preferably the sections of energy transfer means overlap with each other.

Preferably the energy transfer means allow substantially the whole of the circumference of the base section to be joined to the whole circumference of the riser section.

In an alternative embodiment the riser section comprises a flange at both the bottom end and the top end to provides means of bonding or fusing successive riser sections by using an energy transfer means.

In an alternative embodiment the energy transfer means could bond or fuse the base and rise sections in such a way as to maintain any interstitial gap formed from a secondarily contained chamber, the details of said chambers are known to those skilled in the art.

For example once the riser section has been mounted on to the base section the sealing section could be wound around the outside and/or inside of the join, like a bandage and fused or bonded into place.

It will be appreciated that this aspect of the present invention extends to a sealing ring section for bonding and fusing a chamber base section to a riser section, to a method for 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. In addition, the present invention relates to sealing a base section to a riser section, sealing a riser section to a riser section and sealing a riser section to a manhole cover or access hatch.

The invention will now be described in detail with reference to the drawings.

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 cutaway 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 one aspect of the present invention; Figure 2 illustrates a sealing element in the form of a tape according to one embodiment of the present invention; Figure 3 illustrates the sealing element of Figure 2 where the end of thetape has been trimmed to expose the ends of the heating wire; Figure 4 illustrates a containment chamber known in the prior art with a gasket and bolt arrangement; Figure 5 illustrates an elevational view of a containment chamber sealed with a sealing element according to one embodiment of the present invention; Figure 6 illustrates an elevational view with portions broken away of chamber shown in Figure 5; Figure 7 is an enlarged view of part of the joint between a chamber base and a riser section shown in Figure 6; Figure 8 illustrates a sealing element according to an alternative embodiment of the present invention; Figure 9 illustrates a sealing element with overlapping energy transfer means; Figure 10 illustrates an example of the sealing element of Figure 8 in use; Figure 11 illustrates an alternative sealing element in the form of a coated wire; Figure 12 illustrates several spirals of a coated wire as shown in figure 11 with the top surface fused together.

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: chamber or containment chamber - any receptacle designed to keep a fluid in or out.

This includes, but is not limited to, manhole and sump chambers as described herein. It also includes tanks in general.

flange - any collar suitable for attaching one component to another, such as a fitting to a chamber wall. In the examples given the surface of the flange which contacts the chamber wall is substantially planar. However, it will be understood that the flange must conform to the profile of the chamber wall around the pipe inlet opening. Thus the flange can adopt any suitable conformation to achieve the necessary contact with a flat or curved surface or even the corner of a container wall. It also includes 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. In summary, the term "flange" has a broad meaning.

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.

p He - the examples given herein are for a generally circular crosssectioned single wall pipe. However, the invention also covers other cross-sections such as box sections, corrugated and the like and secondarily contained pipes of the "pipe-within-a-pipe" type.

In this case the sealing member or boot for sealing the sleeve to the pipe will be rather more complex. However, such boots are well known in the art. The invention also encompasses pipes which are not circular in cross-section and multiple supply pipes housed within a single secondary pipe.

tubular sleeve - this term has a very broad meaning. It includes any tubular structure through which a pipe may pass. Although illustrated and described as substantially circular cylindrical in form, a sleeve according to this invention need not have a substantially circular crosssection and may confirm to the profile of the pipe to be accommodated in it. Nor need the cross-section of the sleeve be uniform along its whole length, is it need not be cylindrical.

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

enerov 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.

mating region: - this term relates to the region on a component which mates, or fits, together with a mating region of another component. It is intended to cover any region on a component which can fit against a mating region of another component and both said regions be fused together by a separate sealing element. Examples of mating regions include, but are not limited to, flanges, regions on fittings which form a tight sliding fit with a pipe or indeed separate regions within one fitting that can be electrofused together to form a new fitting.

sealing element: - the term sealing element has a very broad meaning in this context.

It is intended to encompass tapes, tubes, coils, filaments, coated wires or packaged elements.

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.

The present invention will now be described, by way of example only, in relation to joining components in underground pipework systems. However, as described below, the invention has general applicability to a wide variety of situations where two plastic components need to be joined together in a substantially fluid-tight fashion regardless of the application.

The sealing element in this invention is therefore intended to have a very broad application and is a truly versatile method of fusing or bonding together components of almost any shape or size by using a sacrificial sealing element wound around or encapsulated between a first component or a second component.

Previously, the only way to form a seal between components incorporating a region formed from an electrofusible plastics material has been to have an energy transfer means in the form of electrofusion element(s) built into the fitting. Surprisingly, it has been discovered that the energy transfer means can be in a separate sealing element. This obviously has a very broad application and for the first time provides a sealing element that can be used in a variety of different situations.

One example of such a sealing element is a tape or bandage, which can be measured from a reel, cut to length, terminated and then fitted in position and welded.

The tape or thin layer of plastics material, being the body of the sealing element, has a heating element or wire with a known resistance value per metre embedded within it.

The plastics material holds the coils or wire runs in a pre-determined format and prevents them from touching each other and shorting during the fusion process. The tape can be placed between or around the mating regions of the two components.

Alternatively, the sealing element could be in the form of a gasket or pre-shaped element, designed to be placed between the two components.

In essence, it will be seen that the present invention is applicable to any situation where two components, each comprising a mating region formed from an electrofusible plastics material, need to be fused or bonded together. Whilst it is particularly useful in the petroleum industry it is not limited to it. It is not limited to any particular application. For example it can be used as a method of providing a water tight seal or a mechanical joint in a wide variety of situations.

Previously, the need for one of the components to incorporate heating windings has always been accepted as the way to seal the components together. The present invention is a revolutionary method for forming an electrofusion seal between two components.

The invention provides a way to form a seal between a region of a first component formed from an electrofusible plastics material and a region of a second component formed from an electrofusible plastics material where the regions are adapted to mate together. This is achieved using a separate sealing element incorporating an energy transfer means. For the first time, a truly versatile sealing member has been devised which can be used across many different applications and components.

The invention is not intended to be limited to the examples given; they merely illustrate the broad application of the invention. In essence, the invention describes a new way of sealing two components using a separate element incorporating an energy transfer means. The element is placed between or wound around the region to fused and then fused in place.

The invention will now be described by way of some specific examples but it should be understood that the invention has very broad scope and application and these are merely some ways into which it can be put in practice. In addition to the tape and gasket that will be explained in greater detail below, the invention would also work for, among other things, a tube, coil, filament or packaged element or indeed any separate sealing element as herein described.

Consequently the invention is applicable to many different types of component, including pipes, chambers and fittings, such as elbows, tees and reducers. Indeed, it applies to many more components, the examples above and below being given for

example only.

Figure 2 shows an example of a tape or bandage according to one aspect of the present invention. It shows an energy transfer means 100, in the form of a wire, running through a tape 101 made of a plastics material. The wire is arranged within the tape so that when the energy transfer means is activated and the area around the wire becomes molten, the energy transfer means will not short circuit as a result of the wire coming into contact with itself. The tape can be measured from a reel and then wound around or between the components to be fused.

The tape is shown with an oscillating wire in the tape. It is possible to have the wire running longitudinally across the length of the tape, with multiple wires in parallel.

This requires multiple connections to each wire but it is possible to use a termination fitting that attaches to more than one wire at the same time.

The wire is made from a wire of known resistance per metre and therefore the technician knows how much current to apply to it and for how long to apply the current in order to ensure that a fluid tight seal is formed.

The modern electrofusion machines, which supply existing couplers with current, and which are used to carry out the electrofusion process on known electrofusion couplings incorporate features which provide a wide degree of versatility.

This means that they will operate a range of different couplings having a range of resistances. In one operational mode the electrofusion machine will run for a set period of time, generally one and a half minutes. The machine can automatically detect how much current to pass through the wires in order to form a satisfactory seal. This can be done by a variety of sensing means, including measuring the resistance of the wire or the current already passed.

Therefore, with a machine of this type, knowing the exact length of the sealing element is not crucial as the machine will automatically deliver the necessary current to form a satisfactory seal.

The path the wire takes within the tape can be chosen by the materials specialist to optimise the seal formed. For example it can be in the form of coils from side to side or wire runs up and down the tape. If the tape is thick enough, the wire may additionally be at or near the upper or lower surface or alternatively be arranged so that it runs near both surfaces. This would maximise the sealing properties of the tape.

In use, the ends of the tape would normally be stripped away to expose bare wire. This is shown in figure 3. The wires can then be connected to a current source as described above and the two fittings can be fused or sealed together.

The tape can be wound around the mating regions of the two components or alternatively placed between the mating regions of the two components. Its configuration and position will depend on the nature of the seal to be formed and the positions of the mating regions with respect to each other.

For example, if the mating regions are two complementary flanges, on two components, the tape can be applied between the flanges prior to the flanges being pressed together. The flanges could then be secured using moulded clips, adhesives or clamping means prior to welding.

Alternatively, in order to provide a seal between a pipe and a pipework fitting, tape could be applied between the mating regions of the pipe and the fitting. In this instance, a sealing element in the form of a tube or tubular sleeve, would be advantageous.

The tape can be wound into a reel or folded into a stack once it is formed in order to store it easily. This way the desired amount can be unwound when it is needed.

Alternatively the sealing member could be in the form of a coated wire. This is shown in figures 11 and 12. A heating wire 90 is coated by a coating 91 made from an electrofuseable material, for example polyethylene. The coating for the wire is shown in figure 11a as having a rectangular cross-section with the longer sides 92 and 93 resting against the surfaces to be fused. The actual cross-section can be varied and figure 11 b shows this as a square cross-section and figure 11c showing an elliptical cross-section.

Although the examples shown show a relatively large amount of coating compared with the thickness of the wire, a varying thickness of coating can be envisaged. The coating can be made from a variety of materials but will be a material compatible with the components to be fused.

When winding the wire around a surface, for example a pipe, having a rectangular coating allows the wire to be laid in a uniform pattern. This is shown in figure 12a, which shows a cut away version of three spirals of a single wire. It shows the sides 94 and 95 laid against each other. This allows the wires to be uniformly spaced from each other and ensures an even weld. It is possible to pass a heat gun or tack welder over the upper surface 93 of the wire once it is in position. This gives a continuous upper surface and joins the successive spirals together. This is shown in figure 12b. This wire is an effective and cheap way of forming an electrofusion weld. It is also very easy to install and use so methods using a wire of the type outlined above are particularly preferred.

in an alternative embodiment the sealing element or member could be a gasket of pre-formed shape. This is different to the tape in that the gasket would be pre formed to a particular size in order to fit specific components. This highlights the obvious advantage of the tape in that it is not specific to a particular type of fitting. The gasket is useful however, when it is to be used with particular components of known dimensions, for example a chamber of the type described above.

Further embodiments of the present invention will now be further exemplified in relation to subterranean fittings. 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 manhole 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.

By way of a specific example, Figure 4 illustrates a containment chamber assembly 20 known in the prior art. It comprises a lid or cover 29, a base section 21 and an upstanding riser section 22 detachably mounted at its lower end to the base 21.

In the present instance, the base and riser sections have complementary radially inwardly directed flanges 23 and 24, respectively, which are secured by a series of circumferentially spaced bolts 25 mounting a seal 26 between the confronting faces 23a, 24a of the respective flanges 23, 24. The riser section 22 has an accordion or corrugated shaped side wall 27 to facilitate trimming the riser as necessary to allow for shallow or deep burial of the containment chamber in the ground. The sump chamber 28 houses equipment, such as pumps and piping connecting the pumps through the base 21 to a supply tank or the like. The sump is usually mounted below ground and is usually surrounded by a manhole sleeve closely circumscribing the top of the riser section 22 and a conventional manhole cover for access to the sump and its contents.

As shown, the riser section 22 has a first flange 24 and the chamber base 21 has a second flange 23. An O-ring 26 is positioned between the two flanges 23 and 24.

A plurality of fasteners is required to make the seal fluid-tight. In this case a plurality of bolts 25 are placed through pre-drilled holes and nuts 25a are used to clamp the riser section to the base section.

The fasteners 25 which extend into the chamber base are relied upon to secure the flanges 23 and 24 and the O-ring 26 in a fluid-tight arrangement. Thus, the entire sealing assembly is located within the chamber base/riser section.

Figures 5, 6 and 7 illustrate a containment chamber 30 according to one embodiment of the present invention comprising a base section 31 and a riser section 32. The hollow base section 31 comprises a bottom 35 and a side wall 36. The base section can be formed from any geometric cross-section, for example circular, rectangular or square but an octagonal cross-section is often used in practice although this embodiment is in no way limited to containment chambers of any particular cross section. At the upper edge of the side wall 36 is a base flange 33 that extends circumferentially substantially perpendicular to the wall 36. It can extend either outwards from the wall 36 away from the body of the chamber or inwards into the chamber. In the example shown the flange 33 extends inwardly from the wall 36.

The riser section 32 is mounted at its lower end to the base 31. It comprises a corrugated side wall 37 that allows the riser section to be trimmed as necessary. This allows the containment chambers to be buried at varying depths underground without the need for variously sized riser sections. The riser section 32 further comprises a riser flange 34 shaped so that it mates with the base flange 33 of the base section 31.

In this example the flanges 33 and 34 have a surface that is substantially flat to allow them to be placed against each other to form a close fit. However, any two shapes adapted to form a close fit between one another is sufficient.

This arrangement is shown in more detail in Figures 6 and 7, which show an elevated view of the containment chamber according to one embodiment of the present invention. Figure 6 shows the riser section 32 mounted onto the base section 31.

Flange 34 is mounted directly on top of flange 33. In a preferred embodiment a sealing element in the form of a sealing ring section, which initially is a separate component, is placed between the two flanges, much in the same way that the O-ring seal was located in the prior art chamber. However, the present sealing element or ring section incorporates or comprises energy transfer means in the form of electrical windings.

These are advantageous set in a thin body of the same plastics material as is used to construct the base and riser sections. The electrical windings may be one continuous heating wire or, preferably, a series of wires that overlap one with another to cover the entire circumference of the flange.

The sealing ring section may be adapted to nest in a pre-formed channel in the base flange for ease of assembly during construction. Alternatively the sealing ring section may be configured to fit over the flange and extend above or below one or both of the flanges where they meet.

In any event, during construction the sealing ring section is sandwiched between the two flanges. When electric current is applied to the winding or windings, either altogether or sequentially, an electrofusion weld is formed between the base section and the riser section.

Alternatively either flange 33 or flange 34 individually or alternatively both together may contain an energy transfer means 61 having the arrangement as shown in Figures 8 or 9.

In order to provide a liquid-tight seal the flange 34 of the riser section is mounted onto the upper surface of flange 33 of the base section. 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. Alternatively a number of bolts as shown in Figure 2 could be used to line up the flanges and provide additional compression before and/or after the flanges have been electrofused together.

Figure 8 shows diagrammatically a sealing ring section that contains an energy transfer means. In this instance a wire 61 is embedded in or near to the surface of the flange in a generally spiral shape and the ends of the wire are connected to electric terminals 61a and 61b.

Figure 9 shows an alternative arrangement in which there are a plurality of energy transfer means. For clarity, only a few of the energy transfer means are shown.

In practice the energy transfer means would cover the entire circumference of the gasket or flange to ensure that the entire circumference of the containment chamber is fused or bonded in a substantially fluid tight manner. In the example shown there are energy transfer means 71, 72 and 73 which overlap in the regions 74 and 75 and each have their own individual electric terminals, e.g. energy transfer means 71 has terminals 71a and 71b, energy transfer means 72 has terminals 72a and 72b and energy transfer means 73 has terminals 73a and 73b. Whilst the terminals are shown at either end of the energy transfer means in practice they could all be wired to one region on the circumference of the chamber or even into a single termination box where advantageously the terminals could be colour coded to show which terminals relate to which heating element. The overlapping regions ensure that the entire circumference of the flanges are sealed together to ensure a substantially fluid-tight seal.

It is also possible to use a single wire wound around the gasket in a spiral starting from on or near the inner circumference of the gasket moving through to the outer circumference of the gasket. If the wire is doubled up into a u shape with the u starting at or near the inner circumference then both terminals will protrude from the gasket in the same place allowing for easy connection. Thus in effect, there are two strands of the same wire running in parallel in an outward spiral.

When the riser section 32 is mounted onto the base section 31, the lower surface of flange 34is mounted onto the upper surface of flange 33 and the flanges are pressed together. The terminals 71a, 71b; 72a, 72b...etc, either together or sequentially in their pairs, are connected to a source of electric current. The current passes through the wire or wires causing the latter to heat the adjacent surfaces of the flanges 33 and 34 to cause the flange 33 and 34 to fuse together in a disc-shaped region which surrounds the opening in the base and riser sections forming a substantially fluid-tight seal.

If the containment chamber were to be made of glass reinforced plastic (GRP) or fibreglass, which is not suitable for electrofusion welding, a modified version of the present invention could be used. The modified version is identical to the version shown in Figures 5 to 9, apart from the inclusion of a layer of adhesive over the surface of the flange which would constitute the surfaces on the flanges 33 and 34 and which overlies the heating wire. The adhesive is a thermoplastic or cross-linking adhesive which, once heated, forms a bond between the flanges 33 and 34. Again, since the bond covers the entire circumference of the opening, it also acts as a liquid tight seal to prevent the ingress of water, or egress of liquids.

It will be appreciated that various modifications to the specific example are possible within the scope of the invention. Thus, for example, the wire 61 could be embedded in either flange 33, 34 or both, and either or both flanges could carry the adhesive coating.

Methods of laying a wire into a flat surface such as a gasket or a tape are known, and can be applied here without substantial modification.

In essence the present invention encompasses methods and apparatus for sealing a first component and second component by introducing an energy transfer means there between and the specific example encompasses methods and apparatus for sealing a chamber base section and chamber riser section by introducing an energy transfer means therebetween.

In a further embodiment the riser section could contain flanges at both the lower and upper ends and fusible regions therein to allow riser sections to be bonded to each other. The present invention also encompasses a method of providing a substantially fluid-tight seal in a containment chamber as described above and the combination of apparatus that results from operating said method.

The regions formed from an electrofusible plastics material in the first and second components including the containment chamber assembly can be manufactured from a variety of materials as selected by the materials specialist.

Therefore the sealing element can also be manufactured from a variety of materials as selected by the materials specialist. Preferably the regions in the first and second components are formed from the same material, which is electrofusible. 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); tetrad uoroethylene-hexafl u roethylene copolymers (F E P) 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.

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

This selection is not intended to be limiting but rather demonstrates the flexibility and breadth of the invention. If using a separate sealing section as the energy transfer means the plastics material which is most compatible to the base and riser section to which it will be joined and with the lowest permeability to the fluid in question will usually be chosen by the materials specialist. 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.

The specific example described above relate principally to single wall chambers.

However, fittings according to the present invention can be used equally well with double-walled chambers where there is an interstitial space between the two chamber walls. In that case a seal is formed between the outer walls and between the inner walls. This can be done using two bandages, one outside and one inside the chamber, which are fused together to form a seal on either side of the interstitial space.

Alternatively, two flanges could be used one protruding outwards and one inward on each component, with a sealing element between each pair of flanges. This removes the need for a bandage. It is also possible to use a flange on one side, for example the inside of the chamber, and a bandage on the other side, for example the outside of the chamber. In either case the integrity of the interstitial space between the chamber walls is maintained and can be monitored.

The invention has been described in detail in relation to a seal being formed using a gasket between two components in a chamber. Many of the principles outlined are equally applicable to seals using different sealing members, e.g. a tape, and different components. The invention is in no way limited to the specific examples given, they are included to outline some specific examples of the broad, versatile application of the invention.

In summary, the invention provides a way to form a seal between a region of a first component formed from an electrofusible plastics material and a region of a second component formed from an electrofusible plastics material where the regions are adapted to mate together. This is achieved using a separate sealing element incorporating an energy transfer means. For the first time, a truly versatile sealing member has been devised which can be used across many different applications and components.

The invention is not intended to be limited to the examples given above; they merely illustrate the broad application of the invention. In essence, the invention describes a new way of sealing two components using a separate element incorporating an energy transfer means.

Claims

Claims: 1. A method of forming an electrofusion seal between a first

component and a second component comprising the steps of: (a) providing a first component incorporating a region formed from an electrofusible plastics material; (b) providing a second component incorporating a region formed from an electrofusible plastics material, the first and second components being adapted to mate together on a mating region; (c) providing a separate sealing element adapted to fit between the first component and the second component in said mating region, said sealing element incorporating energy transfer means, said energy transfer means being adapted to cause, in use, the first component, the second component and the sealing element to fuse or bond together; (d) applying energy to the energy transfer means to fuse or bond the first component to the second component.
2. A method according to Claim 1 wherein the sealing element comprises a flexible band or tape formed from a wire in an electrofusible plastics material.
3. A method according to Claim 1 or Claim 2 wherein the sealing element is in the form of a band or tape which may be cut to length to correspond with the size/length of the mating region between the first and second components.
4. A method according to Claim 1 wherein the sealing element comprises a pre formed unit adapted to conform to the shape and configuration of the mating region between the first and second components.
5. A method according to Claim 1 or Claim 2 or Claim 4 when dependent on Claims 1 and 2, wherein the sealing element further comprises electrical terminal means.
6. A method substantially as hereinbefore described and with reference to and as illustrated in Figure 2, Figure 3 and Figures 5 to 12.
7. A sealing element adapted to form an electrofusion seal between a first component and a second component, said components being adapted to mate together in a mating region, said sealing element incorporating energy transfer means, the energy transfer means being adapted to cause in use the first component and the second component to fuse or bond together in order to form a substantially fluid-tight seal there between.
8. A sealing element as claimed in Claim 7 wherein the sealing element comprises a fusible material which, when heated via the energy transfer means, at least partially melts, causing the first component and the second component to fuse or bond together.
9. A sealing element as claimed in Claim 7 or Claim 8 wherein the body of the sealing element is formed from a plastics material compatible to bond or fuse to the mating regions of the first and second components.
10. A sealing element as claimed in any of Claims 7 to 9 inclusive wherein the energy transfer means comprises an electrical heating wire that is embedded within the body of the sealing element.
11. A sealing element as claimed in any of previous Claims 7 to 10 inclusive wherein the sealing element is in the form of a band or tape.
12. A sealing element as claimed in any of Claims 7 to 10, wherein the sealing element is in the form of a strand of electrical heating wire coated with an electrofusible material.
13. A sealing element as claimed in Claim 12, wherein the coating for the wire has a rectangular cross section, when viewed in a plane perpendicular to longitudinal axis of the wire.
14. A sealing element as claimed in any of Claims 11 to 13, wherein the band, tape or coated wire is adapted to be cut to length to correspond with the size/length of the mating region between the first and second components.
15. A sealing element as claimed in Claim 14 wherein the end of the end(s) of the sealing element are adapted to be trimmable to expose the ends of the heating wire such that the heating wire can be connected to a current supply in use.
16. A sealing element as claimed in any of Claims 7 to 10 inclusive wherein the sealing element comprises a pre-formed unit adapted to conform to the shape and configuration of the mating region between the first and second components.
17. A sealing element as claimed in any of Claims 7 to 13 inclusive or Claim 16 wherein the element further comprises electrical terminals for connecting the heating element to a current supply.
18. A sealing element as claimed in any of Claims 7 to 13 or any of Claims 16 or 17 inclusive wherein the sealing element comprises a tubular sleeve.
19. A sealing element substantially as hereinbefore described and with reference to and as illustrated in Figure 2, Figure 3 and Figures 5 to 12.
20. A sealing element as claimed in any of Claims 7 to 19, adapted to form an electrofusion seal between a first component and a second component, according to the method according to any of Claims 1 to 6.
21. An apparatus comprising a first component and a second component, said first and second components being joined to each other in a substantially fluid-tight fashion by a sealing element as claimed in any of Claims 7 to 20 inclusive.
22. An apparatus as claimed in Claim 21 wherein said apparatus comprises a pipe.
23. An apparatus as claimed in Claim 21 wherein said apparatus comprises a pipework fitting.
24. An apparatus as claimed in Claim 21 wherein said apparatus comprises a chamber or a sump.
25. A method according to any of Claims 1 to 6, wherein the first component comprises a hollow base section having a bottom wall, an upstanding side wall and a first circumferentially extending base flange at the upper edge of the side wall, and the second component comprises an elongated generally tubular riser section having a second circumferentially extending riser flange at its lower terminal edge adopted to confront and overlay the base flange.
26. A sealing element according to any of Claims 7 to 20, wherein the first component comprises a hollow base section having a bottom wall, an upstanding side wall and a first circumferentially extending base flange at the upper edge of the side wall; and the second component comprises an elongated generally tubular riser section having a second circumferentially extending riser flange at its lower terminal edge adopted to confront and overlay the base flange.
27. A containment chamber assembly comprising: (i) a hollow base section having a bottom wall, an upstanding side wall and a first circumferentially extending base flange at the upper edge of the side wall; (ii) an elongated generally tubular riser section having a second circumferentially extending riser flange at its lower terminal edge adopted to confront and overlay the base flange; and (iii) optionally a cover mounted over the upper end of the riser; characterized in that the containment chamber assembly further comprises an energy transfer means, said energy transfer means being adapted to cause in use the base section and the riser section to fuse or bond together in order to form a substantially fluid-tght seal there between.
28. A containment chamber assembly according to Claim 27, wherein the energy transfer means is located in a sealing ring section adapted to fit between the two flanges.
29. A containment chamber assembly according to Claim 27, wherein the energy transfer means can be located in either the first base flange or the second riser flange or alternatively in both.
30. A containment chamber assembly according to any of Claims 27 to 29, wherein the section incorporating the energy transfer means comprises a fusible material which, when heated via the energy transfer means, at least partially melts, causing the base and the riser to be fused together.
31. A containment chamber assembly according to any of Claims 27 to 30, wherein the energy transfer means comprises conduction means for conducting an electric current, said conduction means in use, being heated by the current, to cause heating of the energy transfer means and the adjacent surfaces with which it is in contact.
32. A containment chamber assembly according to any of Claims 27 to 31, wherein the base section and the riser section are formed from the same electrofusible material.
33. A containment chamber assembly according to Claim 28, wherein the sealing ring section comprises a heating element, or a series of heating elements, set into a band of electrofusible material.
34. A containment chamber assembly according to Claim 33, wherein the electrofusible material in the band is the same material from which the base and riser sections are made or alternatively is a material compatible to bond or fuse to the box and riser sections.
35. A containment chamber assembly according to Claim 34, wherein the adhesive is selected from a thermoplastic, thermoses, cross-linking or pressure sensitive adhesive.
36. A containment chamber assembly according to any of Claims 27 to 35, wherein the energy transfer means comprises a heating wire.
37. A containment chamber assembly according to any of Claims 27 to 35, wherein the section incorporating the energy transfer means also incorporates terminals for connecting the energy transfer means to a current supply.
38. A containment chamber assembly according to Claim 37, wherein there is a plurality of terminals and each set of terminals connects a separate section of the energy transfer means to a current supply.
39. A containment chamber assembly according to Claim 38, wherein the sections of energy transfer means overlap with each other.
40. A containment chamber assembly according to any of Claims 27 to 39, wherein the energy transfer means allow substantially the whole of the circumference of the base section to be joined to the whole circumference of the riser section.
41. A containment chamber assembly according to any of Claims 27 to 40, wherein the riser section comprises a flange at both the bottom end and the top end to provides means of bonding or fusing successive riser sections by using an energy transfer means.
42. A containment chamber assembly according to any of Claims 27 to 41, wherein the energy transfer means could bond or fuse the base and rise sections in such a way as to maintain any interstitial gap formed from a secondarily contained chamber.
43. A containment chamber assembly according to Claim 42, wherein the energy transfer means is wound around the outside and/or inside of the join, like a bandage and fused or bonded into place.
44. A method of forming an electrofusion seal in a containment chamber assembly according to any of Claims 27 to 43.
45. A containment chamber assembly substantially as hereinbefore described and with reference to and as illustrated in Figure 2, Figure 3 and Figures 5 to 12.