GB2530240A - A device for underwater cutting or welding - Google Patents

Abstract

A device 100 for underwater cutting or welding comprising: a housing 110 for an oxidising material , at least one igniter 130 to initiate oxidising and at least one passageway 150A defined in the material so as to promote rapid and even oxidisation. The housing has at least one opening to expel oxidised products and a way is provided to attach the device to an item to be cut or welded. The oxidising material may be thermite and the housing 110 may have a seal to prevent water ingress which may be hingeably attached. The housing 110 may be arranged in an external casing 120 which may be pressurised by piped gas which may further pass through the passageway in the material. The opening in the housing may be elongate and may be tapered to aid directing expelled products.

Description

A DEVICE FOR UNDERWATER CUTTING OR WELDING

Field of the Invention

The present invention relates to a device for underwater cutting or welding.

Background

Many specialised structures, objects and equipment are designed for use underwater. As a result such items may require construction, maintenance, repair and decommissioning to be carried out underwater, as it may not be possible or practical to remove structures, objects and equipment from their location in order to carry out such tasks.

As it is often necessary to weld or cut underwater items in situ, for example pipes or frames, specialised cutting devices and techniques have been developed. Tools commonly used on land may not be suitable for underwater use as water may inhibit tool functionality.

Underwater welding is traditionally carried out by divers using arc welding which requires a power supply to create an electrical arc between an electrode and base material to melt the metals at a welding point. It is sometimes been difficult to provide a power supply, for example at extreme depths.

Both heat cutting and welding typically require very high temperatures and due to the nature of it can be difficult to achieve these temperatures underwater in a controlled manner.

It is dangerous for divers to cut and weld underwater with risks increasing as depth of water increases. Limitations of the human body restrict divers to around 600 metres depth. Remote operated vehicles (ROVs) are capable of accurately positioning tools or equipment as an alternative to divers therefore mitigating the risk to personnel and can operate in excess of 3500 metres.

However ROVs are not as dextrous as humans and are expensive, therefore their use can be limited in some situations.

PriorArt A number of systems have been developed in an attempt to improve the position. These are described in the following: International Patent Application W097/37806 (HAGEN) discloses a method and device to join the ends of two cylindrical objects by welding at deep water without the use of divers, where the ends of the two objects are connected with an inner casing inside an outer casing thereby creating a closed chamber around the joint between inner and outer casings. The chamber is evacuated and a therm ite welding process is initiated.

The closed chamber thereby is filled with metal and a mould is established sealingly connected with the outer surface of the two objects and abridging the distance between the two objects.

The Broco (RTM) underwater cutting system includes a torch, a regulator, a knife switch, and ultrathermic cutting rods. The cutting rods produce a temperature in excess of 10,000° F, which is hot enough to quickly cut or melt through almost structures. The system uses only oxygen and a maximum of 150 Amps and is ignited by a spark generated by a 12 or 24 volt auto or marine battery. More information is described at http:/Iwww.broco-rankin. comtunderwater/underwater-cutting/broco-underwater-cutting-system.

The present invention overcomes various problems associated with some prior art system and provides a device for fitting to an object which enables oxidised material to be expelled in a controlled direction corresponding to an area to be cut or welded.

Summary of the Invention

According to one aspect of the present invention there is provided a device for underwater cutting or welding comprising: a housing for an oxidising material, at least one igniter to initiate oxidising of the material, at least one passageway defined in the material so as to promote rapid and even oxidisation through the material, the housing having at least one opening to expel oxidised products and a means to attach the device to an item to be cut or welded.

Oxidisation of the oxidising material generates high temperatures that facilitate cutting and welding. In this way the device can be arranged on an item to be cut or welded such as a bar, chain, shackle, frame or pipe wherein the opening is directed towards the item at a predetermined location so that the expelled products of oxidisation interface the item to enable cutting or welding. For example heat expelled through the opening during oxidisation may serve to cut the item.

In some embodiments the heat generated during oxidisation may be used to heat an object, for example to heat a pipe blocked with a solidified substance that will break down or melt upon heating, therefore restoring flow through the pipe.

Preferably the housing encases the oxidising material so as to be watertight in order to prevent ingress of water. In this way the oxidising material is kept dry and therefore ignition is not inhibited.

The housing therefore serves to protect the material during storage, transportation and in particular during location to the point of use, for example on a sub-sea structure.

Advantageously the device provides an efficient means of cutting and welding underwater by reducing time required to cut or weld as the expelled oxidised material is directed to a specific part of a structure such as frame.

Furthermore the method of cutting and welding with this device reduces the amount of heat dissipated into the surrounding environment therefore reducing negative effects that may be caused by heating the surrounding water as well as accelerating cutting and welding as higher temperatures can be more easily maintained due to direct expulsion of the oxidising materials to the target area.

Other methods of cutting have limited uses that the present invention overcomes. For example water jet cutting tools are expensive, require large pumps and hoses, an operator must control the process and it can be difficult or impossible to use this method in deep water. The present invention can operate without pumps or tubes that are in communicate with the surface, the device can be operated remotely and only requires ignition to be commenced.

Diamond wire cutters can be used for underwater cutting; however they are, slow to cut and may be problematic when cutting load bearing vertical columns as the blade may become pinched by the column during cutting resulting in damage, whereas the present invention can be adapted to cut or weld any shaped structure by adjusting the housing and casing. Furthermore cutting or welding is quick due to the high temperatures obtained and directional expulsion of the oxidising material.

Oxy-fuel welding or cutting may also be used for underwater cutting or welding, however this is often required to be operated by divers and is therefore high risk, in particular in very deep water.

In some situations explosive may be used to cut a structure, however explosives are damaging to marine life, can be difficult and expensive to transport as well as being considered high risk. In particular sound and/or shock waves travel through the water as a result of detonation of the explosive causing harm or death to living organisms including marine life and persons within a certain radius due to effects of the shock and sound waves on the body(ies). The present invention does not cause these detrimental effects.

The present invention uses oxidising materials that can be readily transported and as oxidisation is confined to a define area risk to marine life is minimised.

The housing is typically formed from a strong durable rigid material such as metal or metal alloy so as to be able to withstand substantial pressures associated with being at depth underwater and so as to remain intact during and after the oxidisation process.

Preferably the housing may be formed from metals such as steel or tungsten.

Ideally the housing includes removable end caps so as to be able to add/remove the oxidising material from the housing.

Typically the end caps are dimensioned to be received by the housing.

Preferably the end caps are hexagonal so as to be similar to bolts.

Ideally the housing includes a flattened rim suitable for receiving the end cap.

Typically the rim and end cap include corresponding holes for receiving a bolt so as to allow the end cap to be connected to the housing.

The end caps may include a seal, such as an 0-ring so as to provide a watertight seal that ensures the oxidising material remains dry.

The housing may be formed from an extruded structural section and the end caps fabricated from profile cut plate.

In another preferred embodiment the housing includes an opening through which products of oxidisation are expelled. Preferably the opening is arranged to interface the item at the point at where cutting or welding is required.

Therefore the device may be attached to the item so as to direct the opening to the part to be cut or welded.

In some embodiments the opening may be dimensioned to the size of the area to be cut or welded. The length, width, and shape of the opening may correspond to the part item to be cut or welded. For example the opening may be an elongate slot of equal length to the item to be cut. Therefore the size of the housing may also correspond to size of the item to be cut or welded.

In some other embodiments a plurality of housings may be used wherein the housings are connected or arranged at particular positions to provide the desired cut or weld for example to provide a castellation on a pipe in order to prevent movement after cutting and instead allow the parts to be separated in a controlled manner.

Preferably the opening may be tapered in order narrow and force oxidised products through a narrowed opening. Advantageously this may aid in directing oxidised products including heat to the desired area. Additionally as the opening is narrowed it may increase the force at which products are expelled (Venturi effect) therefore improving efficiency and accuracy of cutting and welding.

In another embodiment the opening may be in the form of a nozzle that projects from the housing. In this way oxidised products are channelled through and forced from a defined opening.

In some preferred embodiments an outer face of the device may include a means of attachment for attaching the device to an item. The means of attachment may comprise a bracket, pins, hooks, clamps, magnets or plates.

The means of attachment may include at least one aperture for receiving a fitting such as a screw, pin or bolt to enable the device to be fixed to the item.

Advantageously the means of attachment enables the device to be held in place during use. Therefore the opening can be arranged at the desired position and oxidised products are expelled at a precise location.

In a preferred embodiment the housing is cylindrical or prismatic.

In preferred embodiments the housing is provided within an outer casing. The outer casing is adapted to receive the housing so that the housing is supported within the casing and is held in a fixed position.

The outer casing serves to further protect the material during transportation and in particular during location to the point of use, for example on a sub-sea structure.

The outer casing provides additional integrity to the device providing additional strength and protection.

The outer casing may include a frame and/or supports for receiving the housing so that the housing is separated from the casing and so as to limit movement of the housing within the casing.

For example the outer casing may have ribs and/or fingers projecting inwards towards the housing so as to support the housing in a fixed position. In this way the housing may be separated from the outer casing by a void or cavity.

In other embodiments the housing may have ribs and/or fingers projecting towards the housing to position the housing within the casing so as to provide a cavity or void about the housing.

Advantageously the space between the housing and the casing may allow for expansion when the housing becomes super heated during oxidisation.

Furthermore in some embodiments the cavity may be filled with an insulating material so as to reduce heat loss during use. For example the cavity may be filled with vermiculite or ceramic based insulation.

In some embodiments the casing may be substantially the same shape as the casing. For example the cylindrical housing may be surrounded and encased by a cylindrical outer housing.

In other embodiments the outer casing may be a different shape to the housing. For example the housing may be cylindrical whereas the outer casing may be square.

In some embodiment the outer casing may not be watertight; therefore the outer casing may permit ingress of water whilst the housing prevents ingress of water to the oxidising material.

Preferably the outer casing is formed from marine grade steel, stainless steel or aluminium.

Typically the outer casing is at least 1mm thick and preferably at least 2mm thick.

Ideally the outer casing is formed from extruded structural section. In other embodiments the outer casing may be fabricated from a cast, moulded, or constructed from profile cut components.

Preferably the outer casing includes an aperture to correspond with the opening. The opening is ideally aligned with and/or projects through an aperture in the outer casing.

In preferred embodiments the opening to the oxidising material has a seal to close the opening so that the oxidising material is protected within the housing until oxidisation is initiated. Furthermore the seal prevents implosion due to high subsea pressure exerted on the device during deployment.

The seal may comprise at least one flap that is displaced during oxidisation.

For example the flap may be hingeably attached to the housing and forced open by burning as the oxidising product expands within the housing.

In other embodiments the seal may comprise a nail head arrangement that serves to seal the opening by having a body section that enters a mouth region of the opening and a head that is larger than the opening so as to cap off the opening. The seal is typically fitted by a resistance fitting so as to be pushed into place. The seal may be fitted by an adhesive in order to form a water tight seal and to prevent dislodgement of the seal during transportation.

In some other embodiments where implosion is not a risk the seal may comprise a layer of material that is destroyed as a result of burning in order to allow escape of oxidised products through the opening, for example a wax seal that melts when burning/oxidation commences.

Ideally the housing is filled with a solid oxidising material wherein the oxidising material has at least one passageway arranged to pass through the oxidising material. For example the oxidising material may be a solid cylindrical section having a channel passing through a central region. The passageway enables oxidation to occur more evenly and rapidly by allowing oxidisation to spread rapidly along the passageway. Additionally this may aid in accelerated oxidisation ensuring maximum temperatures are reached and that all oxidising material is oxidised.

In preferred embodiment the oxidising material includes at least one passageway that traverses across the length of the housing. Ideally a pipe is passed through the passageway.

Preferably the pipe passed through the housing wall and is connected to a piped gas supply. For example the pipe may be connected to a canister of compresses gas.

Typically the internal pipe arranged within the housing is sacrificial so as to be destroyed during oxidisation. Whereas the external pipe, arranged outside of the housing and connected to the canister is not sacrificial.

In this way as oxidisation commences the sacrificial internal pipe is destroyed therefore allowing release of the gas from the pipe. This allows gas to be forced into the housing from the canister which serves to accelerate oxidisation and increase the velocity at which the oxidised product through the opening.

Ideally the device housing and/or cavity defined by outer casing may be pressurised before entry to the water. In this way the device can be pressurised in order to withstand compression at depth.

In some embodiments at least one passageway may be linked to a compensator that allows gas to be released from a reservoir as the device is transported below sea in order to compensate for subsea pressure. It may be envisaged the reservoir may comprise the about mention canister, or may be a separate gas supply.

In some embodiments the solid oxidising material may have a network of passageways for example a grid of channels passing in different planes, such as horizontally and vertically, wherein the channels intersect.

Advantageously the passageways also allow for expansion of materials during oxidisation.

The internal sacrificial pipe may be formed from metal or plastic. For example the sacrificial pipe may be formed from metals such as copper or steel, or synthetic plastics materials, such as polyvinyl chloride (PVC).

The external pipe may be also be formed from metal or plastic. For example the external pipe may be formed from stainless steel or PVC.

In preferred embodiments the gas piped to the housing may be one of, or a combination of the following gasses: oxygen, helium, acetylene, nitrogen, argon and carbon dioxide, Preferably the canister and/or reservoir may be attached to an outer face of the outer casing.

In other embodiments the canister or reservoir may be remote the device, for example being held on a remote operating vehicle (ROV).

In preferred embodiments the oxidising material is Thermite (RTM) or a Thermite variant such as Thermate (RTM). Thermite is a pyrotechnic composition of a fuel -metal powder, and metal oxide which when ignited burns rapidly at high temperatures typically in excess of 2000 °C and therefore capable of burning through most metals.

The Thermite (RTM) undergoes an exotherm ic-oxidation-reduction reaction.

The metal powder used may include but is not limited to: aluminium, magnesium, titanium, zinc, silicon and boron.

The metal oxide used may include but is not limited to boron (Ill) oxide, silicon (IV) oxide, chromium oxide, manganese oxide, iron oxide, copper oxide or lead oxide.

Advantageously Thermite (RIM) is capable of burning underwater and does not require an additional air supply.

In some embodiments the oxidising material may be provided as a powder or granules thereby having a plurality of natural passageways around each piece of/particle of oxidising material.

In preferred embodiments the igniter(s) is/are arranged in a passageway in order to correspond to location of ignition. Preferably more than one igniter is provided in each device. Therefore oxidisation may be initiated at a plurality of location within the oxidising material to ensure equal and rapid burning.

In some embodiments the ignitors may be triggered sequentially or in a predetermined order so as to initiate cutting or welding in a fixed manner.

Cutting may be activated in sections, for example at least one device may be positioned on each face of a square column wherein a device on a first face is ignited, followed by a second face, a third face and then a fourth face. It may be envisaged that activation of the ignitor on the final face or section of the structure to be cut may be delayed until the structure being cut is supported, for example by a crane, in order to prevent uncontrolled collapse, dismantling or fall of the structure. In this way a structure can be safely decommissioned.

Having more than one igniter also serves as a back-up should one igniter fail to ensure oxidisation can take place.

Typically the igniter comprises a wire coil coated in a flammable compound such as potassium chlorate, aluminium, charcoal, dextrin and magnesium.

Preferably the wire coil is formed from a resistance wire, typically a metal alloy that acts as a heating element when a current passes through. In this way as the coil heats the coating ignites and therefore commences oxidisation of the surrounding oxidising material.

In some embodiments the igniter may be set in the oxidising material or a substrate provided within a passageway in order to promote rapid oxidisation and reduce delays in commencement of oxidisation.

In some embodiments the igniters are wired to a remote controller. For example a wire may extend from the device to above water, or to an ROy. In this way a current can be passed along the wire to trigger the igniters and therefore commence oxidisation.

Typically a battery may be used to generate the charged passed along the wire to the igniters.

In some embodiments the device may include a built in battery and an onboard switch) to enable ROV and/or diver to trigger the igniters from the source. Preferably the onboard switch may include a time delay so as to allow a period of time between the device to be triggered and ignition so as to allow the diver/ROy to vacate the area to a safe distance.

In another embodiment a remote radiotacoustic signal may be used to initiate a current to activate the igniters.

In some embodiments the igniters may be linked to sensors to that a remote operator is informed as to whether the igniter has been activated. For example detection of a rise in voltage at the igniter indicates that it was triggered.

In some other embodiments the device may include a temperature sensor so as to monitor temperatures achieved during oxidisation. Therefore an operator is able to check if desired temperatures were reached to enable cutting or welding.

In some embodiments the device may include at least one handle arranged on an outer face to allow the device to be readily lifted and manoeuvred. For example the device may include a lifting eye or hook.

In some embodiments more than one device may be capable of connecting together in order to be fitted to a particular object. For example two semi-circular devices may be arranged around a pipe to be cut.

Ideally when one or more devices are designed to be used together they may be adapted so as to be connected. The devices may include interlocking means or may be dimensioned so that the devices can be positioned together in such as way that they cannot be dislodged, for example having corresponding castellated edging that slots together.

Brief Description of Figures

Figure 1 shows a plan view of the device; Figure 2 shows a cut through view of the device; Figure 3A shows an isometric view of the housing; Figure 33 shows a plan view of the housing; Figure 3C shows an alternative plan view of the housing; Figure 3D shows a cut through view of the housing; Figure 3E shows an end view of the housing; Figure 3F shows a plan view of an end cap; Figure 4A shows an isometric view of the outer casing; Figure 4B shows a plan view of the outer casing; Figure 4C shows an alternative plan view of the outer casing; Figure 4D shows an end view of the outer casing; Figure 5A shows an isometric view of an end plate; Figure 5B shows a side view of the end plate Figure SC shows a top view of the end plate; Figure 5D shows an under view of the end plate; Figure GA shows a plan view a seal; and Figure 6B shows a side view of the seal.

Detailed Description of Figures

Figures 1 to 6 show a preferred embodiment of the device. Figures 1 and 2 show overviews of the device 100 having a housing 110 arranged within the outer casing 120.

Figures 3A-3E show various views of the housing 110.

The housing 110 is cylindrical providing a tube into which oxidising material is placed. The housing 110 has an end cap 111 arranged on each end of the cylinder so as to close the housing 110 making it watertight. The housing therefore serves to prevent the oxidising material 115 from becoming wet whilst underwater.

The housing 110 is formed from metal, typically in the form of an extruded section.

The end cap 111 is hexagonal and corresponds to a planar hexagonal rim 116 (Figure 3A) provided on the housing 110. In this way the end cap 111 is fitted flush to the rim 116 as shown in Figure 3A.

In Figures 3D and 3E the rim 116 includes holes 117A for receiving bolts 114.

The end caps 111 include corresponding holes 117B for receiving bolts 114.

This enables the end caps 111 and the rims 116 to be bolted together in order to close the housing 110 making it watertight.

The end caps 111 are fixed in position on the housing 110 by four bolts 114 (Figures 3A, 3D and 3E).

In some embodiments only one end of the housing 110 may receive an end cap 111. The other end may be enclosed.

The housing 110 includes an opening 140 through which products of oxidation can escape. The opening 140 is a tapered nozzle having an elongate slot that serves to funnel products of oxidisation such as heat and molten metal out of the housing 110 towards the item being cut or welded.

The opening 140 projects from a side of the housing 110 thereby directing products away from the housing 140. The opening 140 is closed by a seal (Figure 6) so as to ensure the housing is watertight until oxidisation occurs.

The seal 145 also prevents escape of oxidising material 115, for example if the oxidising material 115 is a powder or granular form it may easily escape if the seal is not present.

The seal 145 is substantially T-shaped having a body 141 that is inserted into the opening 140 and a T-bar 142 that extends across the opening. The T-bar 143 is larger than the opening 140 so as to limit insertion of the seal 145 and to prevent implosion of the seal under pressure, for example at larger underwater depths.

The seal 145 is formed from metal and includes a gasket seal 144. In use the housing 110 is located within the outer casing 120.

Figures 4A to 4D show various views of the outer casing 120. The outer casing 120 is elongate and has a square cross section.

The outer casing 120 has an aperture 122 that corresponds to the opening of the housing 110. The aperture 122 is rectangular allowing the nozzle to poke through the aperture 122.

The outer casing 120 has displaceable end plates 121 at each end so as to allow access to, and closure of, the outer casing 120. In this way the housing can be inserted and removed from the outer casing 120. In some embodiments only one end of the outer casing 120 may have a displaceable end plate 121.

The end plate 121 is a square plate that serves to cover the open ends of the outer casing 120 so as to enclose the housing 110 within the outer casing 120.

The end plate 121 is fixed to the outer casing 120 by bolts four 114.

Figures 5A-5D show various views of the end plate 121. The end plate 121 includes a wing 123 having a hole 124 to aid in securement of the device 100 to an object. The end plate 121 is square having rounded corners.

The end plate 121 has four round holes 126 for receiving the bolts 114.

The device therefore comprises a housing 110 holding the oxidising material that is arranged in use within an outer casing 120.

The housing 110 is packed with a solid oxidising material, Thermite (RTM). A central channel is provided in the oxidising material 115 through which a sacrificial internal pipe 112 passes (shown in Figure 1).

The sacrificial internal pipe 112 passes through the end caps 111 where it joins the external pipe 113. Connection of the internal pipe 112 with the external pipe 113 permits a continuous flow of fluid from the internal pipe 112 to the external pipe 113 and vice versa.

The housing 110 includes five igniters 130 arranged within the oxidising material 115.

Each igniter 130 comprises of a resistive wire formed into 10 helical coils coated in a flammable compound. The flammable compound comprises: 300 parts potassium chlorate, 60 pads aluminium powder, two parts charcoal, 10% dextrin mixed with water to produce a slurry in which the coils are dipped. The flammable compound is allowed to dry and is dusted with magnesium prior to arrangement in the oxidising material 115.

The igniters 130 are evenly spaced along the length of the housing 110. In this way the oxidising material 115 can be ignited simultaneously at five different locations so as to permit rapid and even oxidisation.

The igniters 130 are arranged against the housing opposite the opening 140.

In this way all oxidising material 115 is oxidised from a back region first forcing waste material and heat out through the opening 140.

The igniters 130 are arranged in passageways 150 so as to allow oxidisation to spread rapidly. The passageway 150 is a hollow channel.

One central passageway 150A passes through the centre of the oxidising material 115. Each igniter 130 is arranged in a separate passageway 150B that links to passageway 1SOA. Passageway 150B traverses passageway 1 50A.

The passageways 150A and 150B form a network through which oxidisation spreads rapidly.

The sacrificial internal pipe 112 passes through the passageway 150A. The sacrificial internal pipe 112 passes through the end cap 111 and the end plate 121. As the internal sacrificial pipe 112 leaves the device through the end plate 121 the internal pipe 112 is connected to an external pipe 113.

The external pipe 113 connects to a pressurised gas source (not shown).

Therefore pressurised gas fills the external pipe 113 and internal pipe 112 enabling the housing to be pressurised. This enables the housing 110 to be equalised during transit to deeper waters, preventing implosion caused by water pressure.

Furthermore the housing 110 can remain pressurised during oxidisation so that as products are expelled pressure does not fall. This can ensure complete burning of the oxidising material 115 and aids in forcing oxidised products from the housing 110.

The pressurised gas source typically includes a valve arrangement so as to prevent back flow of gas into the pressurised air source thereby keeping gas expelled from the source within the housing. The device will now be described briefly in operation. The device 100 is first positioned and fixed on an object to be cut, welded or heated. In this way the device 100 is fixed in situ during oxidisation allowing a user to be clear of the area in which oxidisation occurs.

A change in current is caused in order to trigger the igniters. For example a charge may be passed from a battery. The resistance passing through the coil causes it to become heated, lighting the flammable compound around the coil and thereby initiating oxidisation of the oxidising material 115.

Oxidisation spreads along the passageways 150A, 150B igniting surrounding oxidising material 115.

As the oxidising material 115 is oxidised it is forced from the housing 110 through the opening 140. Waste products from oxidisation include heat and molten metal that are expelled through the opening 140.

The waste materials are directed to the object to be cut, welded or heated by theopening 140.

The invention has been described by way of examples only and it will be appreciated that variation may be made to the above-mentioned embodiments without departing from the scope of invention.

Claims (13)

1. Claims 1. A device for underwater cutting or welding comprising: a housing for an oxidising material, at least one igniter to initiate oxidising of the material, at least one passageway defined in the material so as to promote rapid and even oxidisation through the material, the housing having at least one opening to expel oxidised products and a means to attach the device to an item to be cut or welded.
2. 2. A device according to claim 1 having a seal for closing the opening to prevent water ingress.
3. 3. A device according to claim 2 wherein the seal is hingeably attached to the housing.
4. 4. A device according to any preceding claim wherein the housing is arranged within an external casing.
5. 5. A device according to claim 4 wherein the casing is capable of being pressurised.
6. 6. A device according to claim 5 wherein the casing is pressurised by means of a piped gas supply.
7. 7. A device according to claim 6 wherein the piped gas supply passes through the passageway in order to pressurise the housing.
8. 8. A device according to any preceding claim wherein the oxidising material is a solid.
9. 9. A device according to any preceding claim wherein the oxidising material is Thermite (RTM).
10. 1O.A device according to any preceding claim wherein the opening through which oxidised products are expelled is elongate.
11. 11.A device according to any preceding claim wherein the opening is tapered to aid in directing expelled oxidised products.

    S
12. 12.A device according to any preceding claim wherein the passageway comprises a channel.
13. 13.A device as substantially herein described with reference to the figures.