Method and apparatus for repairing defects

Abstract

A method and apparatus are provided for repairing a surface defect, the method including the steps of: a) providing a bolus of an at least partially liquid alloy in a fill chamber, the fill chamber having a closable outlet and a closable pressure inlet, b) introducing a pressurized fluid into the fill chamber via the pressure inlet and accelerating the bolus such that the bolus is ejected from the fill chamber via the outlet, c) directing the bolus along a path between the fill chamber and the defect such that the bolus contacts the defect, and d) solidifying the at least partially liquid alloy while in contact with the defect.

Description

[Technical field]

[0001] The present invention relates to the repair of defects in surfaces, in particular to a method for repairing surfaces using a bolus of an at least partially liquid alloy composition, as well as a suitable apparatus therefor and the use of said apparatus. [Background technology]

[0002] It is common for surfaces of objects to develop defects, such as holes, cracks, fissures, fractures, dents, tears, holes, and punctures, that prevent or limit the ability of the object to perform its function. For example, pipes or containers may develop cracks or holes that may allow their contents to leak. Such situations would ideally require repair in situ, which may be difficult if the defect is hard to reach or in a dangerous location.

[0003] A common method of repairing surface defects is to apply a patch of material to the affected area, such as attaching a metal plate to the barrel (e.g., by welding) or applying a hardening polymer resin, however these methods often require relocation of the affected object and / or manual application of a more suitable environmental coating.

[0004] Cold spraying involves accelerating heated solid particles towards a surface at very high velocities with a carrier gas. The heated particles are accelerated at such a velocity that they undergo plastic deformation on impact with the surface. The deformed metal particles mechanically bond with the surface and with other metal particles, forming a layer on the surface. Cold spraying has been used to deposit metal layers. However, cold spraying has poor deposition efficiency, especially for alloy powders. Furthermore, the size of particles suitable for cold spraying (typically 1 to 50 μm) is limited to a narrow range, and for some types of particles used, supersonic velocities (typically 500 to 1000 m / s) are required to cause the necessary deformation on impact with the surface. Such high velocities are often achieved by heating the carrier gas to temperatures above 800 °C. Thus, the extreme temperatures and velocities used in cold spraying often cause damage to the surfaces to be sealed, and are certainly not suitable for fragile surfaces. Also, cold spraying is only suitable for sealing surfaces under atmospheric conditions, but cannot be used under submerged conditions. This is because the velocity of the metal particles is reduced as a result of friction with the surrounding water, and because the thermal energy of the particles is dissipated into the surrounding water before hitting the surface, the particles cool in the water, lose their elasticity (ability to deform on impact), and therefore simply bounce off the surface being coated.

[0005] WO2020 / 002886A1 describes a method for sealing a surface, comprising the steps of providing a metal composition, providing a propellant, heating the metal composition above the melting point of the metal composition to provide an at least partially liquid metal composition, accelerating the at least partially liquid metal composition towards the surface by the propellant, and applying the at least partially liquid metal composition to the surface. The method allows a spray of at least partially liquid metal to be directed towards the surface. Upon contact with the surface, the liquid metal droplets deform and cool. As the droplets cool, they solidify on the surface to form a coating. The coating reinforces and / or seals the surface towards which the stream of metal droplets is directed. The method can be used to seal leaks, particularly ongoing leaks. However, in certain circumstances, the liquid metal droplets forming the spray are prone to being deflected by leaking high-velocity material before contacting the surface, or the seal may fail, especially if the leak is in a container under high pressure.

[0006] Thus, there remains a need for a method and suitable apparatus for repairing surface defects that addresses one or more of the aforementioned problems. Summary of the Invention

[0007] According to a first aspect of the present invention, there is provided a method of repairing a surface defect, the method comprising the steps of: a) providing a bolus of an at least partially liquid alloy in a fill chamber, the fill chamber having a closable outlet and a closable pressure inlet, b) introducing a pressurized fluid into the fill chamber via the pressure inlet and accelerating the bolus such that the bolus is ejected from the fill chamber via the outlet, c) directing the bolus along a path between the fill chamber and the defect such that the bolus contacts the defect, and d) solidifying the at least partially liquid alloy while in contact with the defect.

[0008] A bolus of at least partially liquid alloy is a discrete, contiguous amount of at least partially liquid alloy that is distinct from a spray of at least partially liquid alloy (i.e., multiple discrete, discontinuous droplets of at least partially liquid alloy). The nature of the bolus allows the liquid alloy to be provided at a higher velocity and have a greater momentum without depositing an excessive amount of material. As a result, the bolus is more resistant to deflection by material leaking from the defect and is more capable of at least partially penetrating the defect, providing a more robust repair. The at least partially liquid alloy is preferably completely liquid. A bolus may also be referred to as a "slug."

[0009] Solidification of the at least partially liquid alloy is accomplished by cooling the at least partially liquid alloy while in contact with the defect. The at least partially liquid alloy loses heat to the surrounding environment. In some embodiments, this rate of heat loss (and therefore the solidification rate) may be increased by application of a coolant (e.g., a cryogenic fluid).

[0010] If the defect is relatively large compared to the volume of the bolus, it may be necessary to repeat steps a)-c) until enough material has been provided to completely repair the defect.

[0011] Step (c) of directing the bolus to the defect may include providing a delivery line that defines at least a portion of the path. The delivery line protects the bolus from external forces and ensures that it travels correctly along the path. Additionally, the delivery line allows the path to be non-linear, thereby extending the maximum possible length of the path by preventing dissipation of pressurized fluid.

[0012] The delivery line may be positioned by a robot or remote placement arm, optionally a snake-arm robot. Robotic positioning of the delivery line allows the placement of the delivery line to be performed remotely. This allows repair of defects in environments that are harmful to human operators (e.g., suffocating or toxic atmospheres, high temperatures or radiation). Snake-arm robots and similar robots with their high degrees of freedom are particularly suitable, as they also allow the delivery line to be directed to defects that are otherwise inaccessible.

[0013] The delivery line may be operable to limit heat loss from the bolus and / or provide heat to the bolus. This allows the delivery line to be extended without risking premature solidification of the bolus. Limiting heat loss may be achieved by including insulation in or around the delivery line. Providing heat may be achieved by including a heating element in or around the delivery line.

[0014] Step (a) of providing the bolus to the filling chamber may comprise: i) at least partially melting a solid alloy and introducing the resulting at least partially liquid alloy into the filling chamber; or ii) introducing the solid alloy into the filling chamber and at least partially melting it in situ.

[0015] In other embodiments, the solid alloy may be partially melted prior to introduction into the fill chamber, and further melting may occur within the fill chamber.

[0016] The pressurized fluid may optionally be heated above the melting point of the alloy. Heating the pressurized fluid helps to maintain the alloy at least partially in a liquid state. The pressurized fluid may be compressed gas (e.g. compressed air) or steam. The compressed gas may be provided by a container of already compressed gas or may be provided as needed by a compressor. The pressurized fluid may have a pressure of up to about 30 bar, preferably in the range of about 1 bar to about 30 bar, more preferably in the range of about 5 bar to about 25 bar, and most preferably in the range of about 10 bar to about 20 bar. Alternatively, the pressurized fluid may have a pressure in the range of 1 bar to 15 bar, preferably in the range of 3 bar to 8 bar. When the device is used to repair a defect that is an ongoing leak, it is preferred that the pressure of the pressurized fluid (i.e. the pressure applied to the bolus) exceeds the pressure of the fluid leaking from the defect. It will be understood that the required pressure of the pressurized fluid is based on the length of the path between the outlet and the defect (e.g. the length of the delivery line), and the diameter of said delivery line, if any. Repairing an ongoing leak means that the rate of the leak is reduced or prevented entirely.

[0017] The alloy preferably has a melting point of less than about 300°C, more preferably less than 150°C, and most preferably less than 100°C. The alloy may be selected from the group consisting of bismuth alloys, indium alloys, antimony alloys, tin alloys, lead alloys, and gallium alloys. The alloy preferably expands upon solidification. The alloy preferably includes a bismuth alloy (i.e., an alloy based on bismuth) or an alloy containing bismuth. As used herein, the term alloy is understood to be an alloy containing one or more metals. For example, a bismuth alloy is understood to be a bismuth-containing alloy, but may contain other metals. One exemplary alloy is a field metal containing 32.5% Bi, 51% In, and 16.5% Sn by weight. The alloy may be one of the compositions described in US6474414B1, in particular the compositions described in column 3, line 8 to column 4, line 47. In one example, the alloy may include about 91 to 97% by weight bismuth and about 3 to 9% by weight silver. In another example, the alloy may include at least 50% by weight bismuth, 30 to 35% by weight tin, and 1.8 to 2.5% by weight antimony. In another example, the alloy may be as defined in EP3810816A1, and in particular as defined in the claims therein. The contents of US6474414 and EP3810816 are incorporated herein in their entirety.

[0018] In some embodiments, the alloy has minimal dimensional change upon solidification, e.g., shrinkage of less than 5%, preferably less than 3%, and most preferably less than 1%. It is preferable to use an alloy that does not expand or change in volume upon solidification, as this provides a stronger repair compared to materials that shrink upon solidification. Since the alloy is applied to the surface at least partially in liquid form, if it shrinks upon solidification, it will pull away from the edge of the defect and therefore the repair will be less effective. In contrast, having an alloy that expands or retains a constant volume upon cooling or solidification, according to the method of the present invention, will result in a repair that mechanically interlocks with the edge of the defect.

[0019] In this method, in step (b) of introducing pressurized fluid into the filling chamber via the inlet and accelerating the bolus so that the bolus is ejected from the filling chamber via the outlet, i) the outlet and pressure inlet are opened simultaneously so that the bolus is ejected when pressurized fluid is introduced, or ii) the outlet is opened first and the pressure inlet is opened second so that the bolus is ejected when the pressurized fluid is introduced, or iii) the pressure inlet is opened first and the pressurized fluid is introduced into the filling chamber and the outlet is opened second so that the bolus is ejected from the filling chamber when the outlet is opened.

[0020] These particular operating conditions allow the at least partially liquid alloy to be ejected as a bolus rather than as a spray, since discrete quantities of the alloy are accelerated as a single continuous mass. The mass of the bolus is selected relative to the size of the defect to be sufficient to repair the defect (e.g., replace material missing from the surface) without including excess material. Typically, the bolus may have a mass of up to 100 g, and multiple boluses may be used if the defect is large enough that this amount of alloy is insufficient to effect the repair. The speed at which the bolus is ejected varies depending on the pressure of the pressurized fluid, the mass of the bolus, the diameter of the fill chamber, and the diameter of the delivery line, if used.

[0021] In embodiments where a mold is introduced around the defect site to hold the alloy bolus around the defect, the mass of the alloy bolus is specific to the volume of the mold, and typically ranges from 300 g to 5 kg.

[0022] The defect may be an ongoing leak. In other words, the defect may provide a path through which the contents of the object to be repaired may escape. The method may further comprise the step of deflecting material ejected by said ongoing leak from said path. Such step occurs at least simultaneously with step c). The deflection may be achieved by providing a deflection fluid along a deflection line. Optionally, the deflection fluid may be a compressed gas or steam, or may be a pressurized fluid. If the defect is an ongoing leak, the bolus is preferably ejected with sufficient velocity to impart a greater momentum to the material ejected through the ongoing leak than the material ejected through the ongoing leak.

[0023] The method may further comprise a cleaning step, whereby a cleaning liquid is delivered to the defect. The cleaning liquid may be a compressed gas or steam or may be a pressurized fluid. The application of the cleaning liquid before delivering the bolus makes it possible to remove any particles, dirt, dust, grime etc. from the surface and allows a better retention of the alloy due to improved contact with the defect. The cleaning liquid may be delivered through a delivery line or through a deflection line. Alternatively, the cleaning liquid may be delivered through a dedicated cleaning line.

[0024] The bolus may at least partially penetrate the defect. In such embodiments, the alloy is not only located above the defect, but within the defect, and optionally extends beyond the defect into the lumen of the object. Entering the defect increases the interaction between the defect and the alloy, increasing the strength of the repair. The alloy extending beyond the defect allows it to interact with the interior surface of the object, mechanically anchoring the repair such that outward removal (e.g., by pressure within the object) would require the alloy itself to fracture.

[0025] The defect may be at least partially immersed in an aqueous fluid. The aqueous fluid may include water, saline, seawater, a mixture of oil and water, etc. Alternatively, the defect may be at least partially immersed in a non-aqueous fluid, such as oil. In some embodiments of the present invention, the defect may be at least partially immersed in water. Advantageously, alloys with a melting point below 100° C. are preferred, meaning that the alloy has a melting point lower than the boiling point of water. Therefore, the bismuth alloy, when immersed in water, will remain in liquid form until it cools down to a solid, and furthermore, will not result in the generation of steam. Similarly, the bismuth alloy will not react with water, in contrast to, for example, liquid aluminum, which will react violently or explosively with water. Therefore, the alloy does not include compositions that will react violently with water when in the liquid state. This may be a chemical reaction, or may be due to the rapid generation of steam due to the high temperatures required to melt the alloy.

[0026] The method may further include disposing a mold around the defect prior to the step of directing the bolus along a path between the fill chamber and the defect such that the bolus contacts the defect, the mold operable to hold the alloy in contact with the defect. The use of a mold ensures that the alloy remains in contact with the defect as it cools and solidifies. The mold may also be shaped to produce a solidified alloy in an advantageous shape. For example, the mold may produce a cooled alloy that surrounds the object in which the defect is located, enhancing the repair to require fracture of the solidified alloy rather than merely separation from the defect and / or surface.

[0027] The method may further include removing debris from the delivery line and / or the filling chamber. Removing debris may include, for example, passing pressurized fluid through the delivery line and / or the filling chamber via a removal line and a removal valve.

[0028] A second aspect of the invention relates to an apparatus for repairing defects, the apparatus comprising a fill chamber for holding an at least partially liquid alloy, the fill chamber comprising a pressure inlet and an outlet, and a pressure line in fluid communication with the pressure inlet and connectable to a source of pressurized fluid. The apparatus can direct a bolus of the at least partially liquid alloy to the defect by propelling it with the pressurized fluid. The bolus deforms on impact with the defect and conforms to its shape before cooling and solidifying to effect repair of the defect. The apparatus can also direct the at least partially liquid alloy as a spray to the defect. The fill chamber is configured to be able to withstand the temperature of the at least partially liquid metal and the pressure of the pressurized fluid. In other words, any material capable of holding the molten alloy without being rapidly degraded by the alloy. For example, the fill chamber may be constructed of mild steel, stainless steel, or copper. These materials are solid in construction. The fill chamber may be in any suitable form, preferably the fill chamber is a section of a tube or pipe. The internal volume of the fill chamber limits the maximum volume of alloy that can be contained and therefore the maximum size of the bolus. The filling chamber may be essentially cylindrical and may have an internal diameter of up to 150 mm, preferably in the range of 5 mm to 25 mm, more preferably in the range of 10 mm to 20 mm, and most preferably about 15 mm. In embodiments in which the alloy is at least partially melted in the filling chamber, the preferred filling chamber diameter is in the range of 20 mm to 150 mm, more preferably in the range of 50 mm to 100 mm, and most preferably about 70 mm. In embodiments in which the alloy is at least partially melted in the filling chamber, the preferred filling chamber diameter is in the range of 2 mm to 20 mm, more preferably in the range of 4 mm to 15 mm, and most preferably in the range of 5 mm to 13 mm.

[0029] The pressure line is connectable to a source of pressurized fluid. In some embodiments, the source of pressurized fluid is part of the device and the pressure line is connected to the source of pressurized fluid. The source of pressurized fluid may be a container of compressed gas (e.g., a cylinder of compressed gas such as air or nitrogen). Alternatively, the source of pressurized fluid may be a compressor. Still alternatively, the source of pressurized fluid may be a boiler.

[0030] The apparatus may further comprise a delivery line in fluid communication with the outlet. The delivery line extends the maximum possible length of the path between the outlet and the defect by preventing dissipation of the pressurized fluid after ejection from the filling chamber and preventing external forces from interfering with the bolus. In some cases, the delivery line may be of any suitable length necessary to define a path between the outlet and the defect. The delivery line may be up to 50 m long, alternatively up to 25 m long, further alternatively up to 10 m long, and further alternatively up to 5 m long.

[0031] The delivery line may be flexible, allowing the path to be non-linear, allowing access to hard-to-reach defects. The delivery line may be made of any suitable material, such as braided metal (e.g., mild steel, stainless steel, aluminum, or copper), polymer tubing, or silicone tubing. In some embodiments, the delivery line is a polymeric tube or silicone tubing within a sheath of braided metal. The diameter of the tubing line ranges from 0.1 mm to 25 mm, preferably 1 mm to 15 mm, more preferably 2 mm to 15 mm, even more preferably 3 mm to 13 mm, and most preferably about 6 mm. In some embodiments, the diameter of the tube narrows toward the distal end (i.e., the end proximal to the defect).

[0032] This increases the velocity of the bolus.In other embodiments, the diameter of the tube is constant along its length.

[0033] The delivery line may comprise a handle adjacent the outlet, optionally comprising means for ejecting the at least partially liquid alloy. The handle facilitates positioning of the delivery line for an operator and enhances safety by increasing the distance between the operator and the bolus. Advantageously, the handle may incorporate means for actuating the pressure inlet and outlet to eject the bolus.

[0034] The delivery line may be compatible with or include a robot (e.g., a snake-arm robot) operable to position the delivery line. The use of a robot allows the delivery line to be positioned without the need for a human operator to be present, thereby allowing the device to be used in hazardous environments. Snake-arm robots and similarly flexible robots are particularly useful as they allow access to defects in otherwise inaccessible locations.

[0035] The delivery line may include insulation and / or a heating device. The inclusion of insulation and / or a heating device in or around the delivery line prevents the at least partially liquid bolus of alloy from prematurely cooling (and potentially solidifying). The delivery line may be at least partially covered with heating tape.

[0036] The delivery line may be provided with a nozzle at its end. The nozzle may be conical, cylindrical, cubic, or arcuate. The nozzle opening may be circular, diamond, or arcuate. In fact, any suitable nozzle shape or nozzle opening shape may be used. The shape of the nozzle or nozzle opening may be selected to provide a particular shape for the bolus.

[0037] The filling chamber may further comprise an alloy inlet, which allows the introduction of the alloy forming the bolus into the filling chamber, either in a solid state or in an at least partially liquid state. Providing a specific inlet for this purpose allows the filling chamber to be rapidly reset, thereby allowing the device to rapidly provide multiple boluses.

[0038] The apparatus may further comprise an alloy chamber in fluid communication with the alloy inlet, optionally comprising a heater operable to at least partially melt a portion of the solid alloy. The alloy chamber allows for storage of the alloy ready for use. The alloy chamber may store the alloy as a solid that is introduced into the filling chamber and melted in situ, preferably the alloy is a granular solid that can be easily split when introduced into the filling chamber. The optional heater allows for the alloy to be at least partially converted to a liquid state before being introduced into the filling chamber, thereby reducing the time required between bolus delivery. The alloy chamber has a volume suitable for the delivery of at least one appropriately sized bolus, preferably up to 1 liter. The appropriate size of the bolus may be determined based on the size of the repair to be performed and the size of the mold to be fixed around the defect, if used.

[0039] The alloy chamber further comprises a balance inlet, and the apparatus may further comprise a balance line in fluid communication with the balance inlet, and optionally also in fluid communication with the pressure line. The balance inlet and balance line allow for the introduction of a balance fluid into the alloy chamber, the balance fluid operable to push the alloy from the alloy chamber to the fill chamber. When the balance line is in fluid communication with the pressure line, the balance fluid is the same as the pressurized fluid. Alternatively, the balance line may be in fluid communication with a dedicated balance fluid source.

[0040] The fill chamber may include insulation and / or a heater, these features allowing the at least partially liquid alloy to be maintained in an at least partially liquid state and / or a solid alloy to be converted to an at least partially liquid alloy within the fill chamber.

[0041] The device may further comprise one or more sensors (e.g., temperature / pressure sensors) and / or a control system. The inclusion of sensors allows an operator to monitor the device and determine when a bolus is ready to be delivered, for example, by monitoring the temperature of the alloy in the fill chamber and the pressure in the pressure lines. The control system optionally allows for easy control of temperature and / or pressure in response to measurements from the one or more sensors.

[0042] The apparatus may further comprise a deflection line operable to deliver a deflection fluid to deflect material that may be leaking from a defect from the path traveled by the bolus. The deflection line may be fluidly connected to the pressure line. Alternatively, the deflection line may be fluidly connected to a dedicated deflection fluid source.

[0043] The apparatus may further comprise a housing enclosing one or more of the charge chamber, at least a portion of the pressure line, at least a portion of the delivery line if present, the alloy chamber if present, and at least a portion of the balance line if present, optionally the housing comprising insulation and / or a heater. The housing ensures that the apparatus is protected and allows for easier transport. When the housing comprises insulation and / or a heater, the ease with which an at least partially liquid alloy can be maintained in a liquid state and / or a solid alloy can be converted to an at least partially liquid alloy is increased.

[0044] The apparatus may further comprise a removal line. The removal line is operable to remove the system to ensure the delivery line is free of debris and / or to clean the surface containing the defect using pressurized fluid. The removal line allows for a fluid connection between the pressure line and the fill chamber, which bypasses the alloy chamber (if present) and at least a portion of the fill chamber. In some embodiments, the removal line completely bypasses the fill chamber and provides fluid communication between the pressure line and the delivery line. This allows for removal of the delivery line and / or cleaning of the surface containing the defect while retaining at least a portion of the liquid alloy in the fill chamber.

[0045] A third aspect of the invention relates to applying a bolus of at least partially liquid alloy to a defect of a target using the apparatus of the second aspect of the invention, which may be achieved once the fill chamber holds a bolus of at least partially liquid alloy by operating the outlet and pressure inlet as follows: i) opening the outlet and pressure inlet simultaneously, or ii) opening the outlet before opening the pressure inlet, or iii) opening the pressure inlet before opening the outlet, such that the bolus is ejected from the fill chamber when the outlet is opened.

[0046] Alternatively, this may be accomplished in the absence of an at least partially liquid alloy bolus from the fill chamber by operating the pressure inlet, alloy inlet, and outlet as follows: i) opening the pressure inlet before the alloy inlet and outlet are opened simultaneously, or ii) opening the values ​​in the following order: a. pressure inlet, b. alloy inlet, c. outlet.

[0047] A fourth aspect of the invention relates to applying a spray of at least partially liquid alloy to a surface defect using the apparatus of the second aspect of the invention. This may be achieved by introducing the at least partially liquid alloy into the fill chamber while both the outlet and the pressure inlet are open. The at least partially liquid alloy is depleted as it is introduced and droplets separate to form a spray. Alternatively or additionally, this may be achieved by opening a removal valve to introduce further pressurized gas so as to break up the bolus to form a spray of discrete droplets.

[0048] A fifth aspect of the invention relates to applying a jet of at least partially liquid alloy to a surface defect using the apparatus of the second aspect of the invention. This may be achieved by pressurizing and ejecting a large amount of the at least partially liquid alloy from an outlet. The jet is a continuous flow of the at least partially liquid alloy as opposed to discrete amounts of the at least partially liquid alloy forming a bolus. For example, a leading edge of the jet of the at least partially liquid alloy may contact the defect while the jet is still being extruded from the outlet or delivery line, if used.

[0049] Any heater described herein may include one or more resistive heating elements (e.g., heating tape). Alternatively or additionally, the heater may be a tube through which a heated fluid, such as steam or water, passes. Alternatively or additionally, the heater may be a pyrotechnic means.

[0050] Any of the outlet, pressure inlet, balance inlet, or alloy inlet or removal valves may comprise a valve operable to be switched from an open position to a closed position and vice versa. The valve may be rapidly switched from an open position to a closed position, for example, in less than 1 second, less than 0.5 seconds, less than 0.2 seconds, or less than 0.1 seconds. Suitable valves include, but are not limited to, ball, butterfly, or needle, and may be mechanically actuated or electromechanically actuated (e.g., solenoid valves).

[0051] It will be understood that any feature described with respect to one embodiment of the invention may be combined with features described with respect to another embodiment of the invention. [Brief description of the drawings]

[0052] [Figure 1] FIG. 2 is a schematic diagram of one embodiment of the apparatus of the second aspect of the invention, the apparatus comprising a filling chamber (10) having a pressure inlet (20) and a pressure outlet (30), and a pressure line (40). [Diagram 2] FIG. 2 is a schematic diagram of one embodiment of the apparatus of the second aspect of the present invention, the apparatus comprising a filling chamber (10) having a pressure inlet (20) and a pressure outlet (30), a pressure line (40), and a delivery line (50). [Diagram 3] FIG. 2 is a schematic diagram of one embodiment of an apparatus of the second aspect of the present invention, the apparatus comprising a fill chamber (10) having a pressure inlet (20), a pressure outlet (30) and an alloy inlet (60), a pressure line (40), a delivery line (50), and an alloy chamber (70). [Figure 4] FIG. 2 is a schematic diagram of one embodiment of an apparatus of the second aspect of the present invention, the apparatus comprising a fill chamber (10) having a pressure inlet (20), a pressure outlet (30) and an alloy inlet (60), a pressure line (40), a delivery line (50), an alloy chamber (70) having a balance inlet (80), and a balance line (90). [Diagram 5] FIG. 2 is a schematic diagram of one embodiment of an apparatus of the second aspect of the present invention, the apparatus comprising a fill chamber (10) having a pressure inlet (20), a pressure outlet (30) and an alloy inlet (60), a pressure line (40), an alloy inlet (60), a pressure line (40), a delivery line (50), and an alloy chamber (70). [Figure 6] FIG. 1 is a schematic diagram of one embodiment of an apparatus of the second aspect of the present invention, comprising a loading chamber (10) having a pressure inlet (20), a pressure outlet (30), an alloy inlet (60), and a relief valve (100), a pressure line (40), a delivery line (50), an alloy chamber (70), and a relief line (110). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] The present invention provides a method and apparatus for repairing surface defects. Defects include holes, cracks, fissures, fractures, dents, crevices, holes, and punctures that prevent or limit the ability of an object to perform its function. For example, hollow objects such as containers or pipes can leak if the defect extends through the thickness of the surface.

[0054] Defects that can be repaired by the method and apparatus of the present invention can occur on a variety of surfaces, such as wooden surfaces, metal surfaces, geological surfaces (e.g., stone or rock), composite surfaces (e.g., cement), polymeric surfaces, and architectural surfaces. Defects can occur in hazardous locations, such as locations contaminated by radioactive, chemical, or biological waste, or locations exposed to excessive temperatures or harmful atmospheres. Repairable defects can occur in oil and gas wells and pipelines, chemical refinery equipment, aircraft parts such as aircraft fuselages and wings, military equipment, mining equipment, and marine vehicles such as submarines, ships, and boats.

[0055] As used herein, the term repair and similar terms are understood to mean restoring the object that constitutes the surface to be repaired to its original function. For example, a previously cracked and leaking tube can now withstand the pressures it was originally designed to handle. Repair is performed by filling areas where the surface material has been displaced (through chemical processes such as corrosion or physical processes such as impact) with an alloy composition. The alloy composition may also be in contact with the surface in other areas. In certain areas of the art, the terms "restoration" and "sealing" may be used interchangeably with the term "repair". For example, in the nuclear industry, the restoration of a surface would be called "recovery" rather than "repair".

[0056] Repairing a defect may include repairing a defect that is the source of a leak. The leak may be an ongoing leak where material is leaking during the repair process, meaning that the method of the present invention may be used to repair the defect without the need to stop the leak by isolating and / or evacuating the object being repaired.

[0057] With reference to FIG. 1, the present invention provides an apparatus for repairing defects in a surface. The apparatus comprises a fill chamber (10) including a pressure inlet (20) and an outlet (30), and a pressure line (40) connectable to a pressure source providing pressurized fluid. In operation, a bolus of at least partially liquid alloy is provided in the fill chamber (10), the apparatus is positioned such that the outlet (30) is directed toward the defect, and the bolus is ejected from the fill chamber (10) along a path between the outlet (30) and the defect. The bolus impacts the defect and deforms to conform to its contour while it is in an at least partially liquid state. While in contact with the defect, the bolus cools and solidifies, replacing the missing material and restoring functionality to the object including the surface where the defect was located.

[0058] In this embodiment, the fill chamber (10) includes a heater configured to heat the alloy to at least its melting point. The pressure inlet (20) and outlet (30) each include a valve operable to be rapidly switched between an open position and a closed position (e.g., each may be a ball, butterfly, needle, or solenoid valve). In some embodiments, the outlet (30) may further include a nozzle to ensure that the bolus travels along an intended path.

[0059] The ejection of the bolus from the fill chamber (10) is accomplished by exposing it to pressurized fluid from a pressurized fluid source while the outlet (30) is open, and the entire amount of the at least partially liquid alloy held within the fill chamber (10) is ejected as a single continuous mass, or bolus.

[0060] This is in contrast to forming a spray, in which discrete portions of the at least partially liquid alloy are separated and accelerated as individual droplets (e.g., by simultaneously introducing pressurized fluid and the at least partially liquid alloy into the fill chamber (10) when the outlet (30) is open).

[0061] Due to its deformable nature, gradually exposing the bolus to pressure may cause it to break down and form a spray. If pressure is introduced gradually while the bolus is still mobile, there is an increased risk of "breakthrough" (the pressurized fluid will form a channel through the bolus, reducing the rate of acceleration and increasing the likelihood that the bolus will break down and form a spray). Thus, ejection of the bolus requires acceleration by rapid exposure to pressurized fluid. This may be achieved in one of two ways:

[0062] In the first mode, the outlet 30 and the pressure inlet 20 are opened simultaneously. This mode traps the bolus in the filling chamber 10 until acceleration occurs, preventing it from starting to flow prematurely (e.g., under gravity). However, it requires a high degree of coordination between the outlet 30 and the pressure inlet 20.

[0063] In the second mode, the outlet (30) is opened before the pressure inlet (20) is opened, which means that only the pressure inlet (20) needs to be opened quickly, at the risk of the bolus starting to flow prematurely from the outlet (30).

[0064] In the third mode, the pressure inlet (20) is opened before the outlet (30). This means that only the outlet (30) needs to open quickly, at the risk of the bolus starting to flow from the pressure inlet (20) along the pressure line (40).

[0065] In either case, the pressure differential between the pressurized fluid in pressure line (40) and the atmospheric pressure beyond outlet (30) will accelerate the bolus in the direction of outlet (30) and, if properly positioned, towards the defect.

[0066] In some embodiments, the device further includes one or more sensors. For example, the device may include a pressure sensor in the pressure line (40) to ensure that the pressurized fluid has sufficient pressure to accelerate the bolus, and / or a temperature sensor in the fill chamber (10) to ensure that the alloy is at least partially liquid. Information collected by these sensors may be communicated to an operator and / or a control system (e.g., to inform the operator that the device is "ready" or "not ready").

[0067] The embodiment of Fig. 2 corresponds to the embodiment of Fig. 1 with the addition of a delivery line (50) in fluid connection with the outlet (30). If a nozzle is used, the delivery line (50) is located between the outlet (30) and the nozzle. In use, the delivery line (50) defines a path between the outlet (30) and the defect, ensuring that the bolus is delivered accurately even over longer distances. Since the bolus is at least partially liquid, it can be thought of as flowing down the delivery line (50) as a stream, following any curves in the path defined by the delivery line (50).

[0068] In this embodiment, the delivery line (50) is flexible, allowing the path to be non-linear. This simplifies positioning of the device relative to the defect, as only the ends of the delivery line (50) require precise positioning. Additionally, it allows for repair of defects in locations that would otherwise be inaccessible (e.g., enclosed spaces).

[0069] In other embodiments, the flexible delivery line (50) may further include a robotic positioning system (e.g., a snake-arm robot) that can autonomously position the delivery line, thereby allowing the device to be used in hazardous environments without endangering the safety of a human operator.

[0070] The embodiment of Figure 3 corresponds to that of Figure 2 with the addition of an alloy chamber (70) in fluid communication with the filling chamber (10) via an alloy inlet (60). This arrangement allows for easy loading of the alloy into the filling chamber (10), making the device quicker to use.

[0071] The alloy inlet (60) includes a valve that mediates the transfer of the alloy between the alloy chamber (70) and the filling chamber (10). It is noted that this valve should be closed during the advancement of the bolus. The filling chamber (10) may include a heating element as described above. Alternatively or additionally, the alloy chamber (70) may include a heating element configured to heat the alloy to at least its melting point.

[0072] The embodiment of FIG. 4 corresponds to that of FIG. 3 with the addition of a balance line (90) that is fluidly connected to the pressure line (40) and the alloy chamber (70), the latter being connected via a balance inlet (80).

[0073] The balance line (90) provides the motive force necessary to transfer the alloy from the alloy chamber (70) to the fill chamber (10). The balance line (90) also allows the device to operate in a "spray mode" by simultaneously introducing the alloy and pressurized fluid while the outlet (30) is open. The balance line (90) also allows the device to operate in a "jet mode" by pressurizing the entire contents of the alloy chamber (e.g., by opening the outlet (30) and balance inlet (80) while the pressure inlet (20) is closed). Alternatively, the device can be operated in a "jet mode" by providing an excess amount of at least partially liquid alloy into the fill chamber, which allows the alloy to be ejected as a continuous stream rather than as a discrete bolus.

[0074] The embodiment of Figure 5 has a pressurized fluid path through the alloy chamber (70) and the fill chamber (10) such that the alloy inlet (60) also acts as the pressure inlet (10) and the alloy chamber (70) acts as a continuation of the pressure line (40). In this embodiment, providing the motive force to transfer the alloy from the alloy chamber (70) to the fill chamber (10) also provides the motive force to expel the bolus from the fill chamber when the pressure outlet (30) is opened.

[0075] The embodiment of Figure 6 corresponds to that of Figure 5 with the addition of a removal line (110) and removal valve (100) for the operational advantage of being able to remove the line of any debris without disturbing the alloy in the alloy chamber (70). When operating in bolus mode to eject the alloy from the system, the removal valve (100) remains closed throughout operation.

[0076] The removal line (110) also allows the device to operate in a "spray mode" by simultaneously introducing alloy and pressurized fluid into the fill chamber (10) while the outlet (30) is open, and the removal line (110) also allows the device to operate in a "jet mode" by pressurizing the entire contents of the alloy chamber.

[0077] It will be appreciated that the removal line (110) and removal valve (100) may be incorporated into any of the embodiments described herein to provide the functionality of removing the line of debris. In some embodiments, the removal valve (100) and outlet (30) are combined, for example in the form of a three-way valve, to pass pressurized fluid, at least partially liquid metal, or a combination thereof, through the delivery line as desired.

[0078] When operating in any of the aforementioned modes, it may be advantageous to match the location of the defect to a collar or mold to ensure that the alloy (whether in the form of a bolus, spray or jet) is precisely directed to the location of the defect. In certain embodiments, the collar is used to define a volume around the defect into which the alloy is injected. Advantageously, the collar or mold defines a volume that surrounds the object in which the defect is located, such that removal of the solidified alloy requires not only displacement but also destruction of the solidified alloy.

[0079] (Example) The invention will now be described with reference to the following non-limiting examples.

[0080] Example 1 The apparatus described in Figure 4 was used to repair active leaks in a 1 inch (2.54 cm) outside diameter steel pipe with a 1 mm diameter hole drilled in it. Water exited each leak at the rate indicated. In each example, the following process steps were followed:

[0081] 1. The heater was turned on and the required alloy chamber and delivery line temperatures were set.

[0082] 2. The pressurized fluid in the pressure line (nitrogen in this example) is brought to the required pressure.

[0083] 3. The alloy (in this example, field metal (32.5 wt% Bi, 51 wt% In, 16.5 wt% Sn) with a melting point of 62° C.) was added to the heated alloy chamber and allowed to melt.

[0084] 4. The valves with the balance inlet and alloy inlet were opened to transfer the molten alloy into the charging chamber.

[0085] 5. The valves containing the balance inlet and the alloy inlet were closed.

[0086] 6. The delivery line was positioned so that the nozzle at its end was aimed at the ongoing leak.

[0087] 7. The valves with the pressure inlet and outlet were opened simultaneously, and the molten alloy was injected in a single "charge".

[0088] 8. The molten alloy was allowed to cool while in contact with the defect.

[0089] As a test of the effectiveness of each repair, water within the tube was pressurized until the repair failed.

[0090] [Table 1]

[0091] Example 2 The stainless steel defects were repaired using the apparatus described in Figure 5. No water was flowing during the repair, but the leak rate was measured prior to sealing. For each example, the following steps were followed:

[0092] 1. The heaters were turned on and the required alloy chamber, fill chamber and delivery line temperatures were set.

[0093] 2. The alloy (in this example, a field metal (32.5 wt% Bi, 51 wt% In, 16.5 wt% Sn) with a melting point of 62°C) was added in solid form to a heated alloying chamber and allowed to melt.

[0094] 3. The pressurized fluid in the pressure line (nitrogen in this example) is brought to the required pressure.

[0095] 4. The delivery line was manually positioned but held by a stand at a known angle and distance incident on the defect.

[0096] 5. The valve with the pressure inlet was opened.

[0097] 6. The valve with the alloy inlet was opened and the molten alloy was transferred into the filling chamber.

[0098] 7. The valve with the pressure outlet was opened and the molten alloy was injected in a single "charge".

[0099] 8. The molten alloy was allowed to cool while in contact with the defect.

[0100] To test the effectiveness of each repair, the water in the pipes was pressurised up to 15barg and the leak rate was measured.

[0101] [Table 2]

[0102] Example 3 The apparatus shown in Figure 2 was used to repair a defect in a straight union stainless steel joint joining two 1 inch copper pipes. A nitrogen gas leak of 4.5 barg flow was allowed to flow at the time of sealing. A mould was used around the repair. The following process steps were followed:

[0103] 1. The heaters were turned on and the required alloy chamber, fill chamber and delivery line temperatures were set.

[0104] 2. The alloy (in this example, a field metal (32.5 wt% Bi, 51 wt% In, 16.5 wt% Sn) with a melting point of 62°C) was added in solid form to a heated alloying chamber and allowed to melt.

[0105] 3. A mold was placed around the restoration area.

[0106] 4. The delivery lines were connected to the mold.

[0107] 5. The pressurized fluid in the pressure line (nitrogen in this example) is now at the required pressure.

[0108] 6. The valve with the pressure inlet was opened.

[0109] 7. The valve with the pressure outlet was opened to inject the molten alloy in a single "charge".

[0110] 8. The molten alloy was cooled while in contact with the defect.

[0111] 9. The mold was removed.

[0112] [Table 3]

[0113] Example 4 The apparatus shown in Figure 2 was used to repair a defect in a 2 inch elbow connection between stainless steel piping. A 0.2 barg dripping mineral oil leak was flowing at the seal. A mold was used around the repair. The following process steps were followed:

[0114] 1. The heaters were turned on and the required alloy chamber, fill chamber and delivery line temperatures were set.

[0115] 2. The alloy (in this example, a bismuth alloy (57% Bi, 26% In, 17% Sn by weight) with a melting point of 78°C) was added in solid form to the heated alloy chamber and allowed to melt.

[0116] 3. A mold was placed around the restoration area.

[0117] 4. The delivery lines were connected to the mold.

[0118] 5. The pressurized fluid in the pressure line (nitrogen in this example) is now at the required pressure.

[0119] 6. The valve with the pressure inlet was opened.

[0120] 7. The valve with the pressure outlet was opened to inject the molten alloy in a single "charge".

[0121] 8. The molten alloy was cooled while in contact with the defect.

[0122] 9. The mold was removed.

[0123] [Table 4]

[0124] These examples demonstrate that the methods and apparatus of the present invention can be used to effect repair of surface defects, and in particular, to repair defects that are leaking material. These examples further demonstrate that the repairs effected by the methods and apparatus of the present invention are robust and can withstand significant pressure differentials across the repaired surface.

Claims

1. 1. A method for repairing surface defects, comprising: a) providing a bolus of an at least partially liquid alloy in a fill chamber, said fill chamber having a closable outlet and a closable pressure inlet; b) introducing pressurized fluid into the filling chamber via the pressure inlet and accelerating the bolus such that the bolus is ejected from the filling chamber via the outlet; c) directing the bolus along a path between the filling chamber and the defect such that the bolus contacts the defect; d) solidifying the at least partially liquid alloy while in contact with the defect; A method comprising:

2. The method of claim 1 , wherein step (c) of directing the bolus to the defect comprises providing a delivery line that defines at least a portion of the path.

3. The method of claim 2 , wherein the delivery line is positioned by a robot.

4. The method described in claim 3, wherein the robot is a snake-arm robot.

5. A method according to any one of claims 2 to 4, wherein the delivery line is operable to limit heat loss from the bolus and / or to provide heat to the bolus.

6. The step (a) of providing the bolus to the filling chamber comprises: i) at least partially melting a solid alloy and introducing the resulting at least partially liquid alloy into said fill chamber; or ii) introducing said solid alloy into said filling chamber and at least partially melting it in situ; The method of claim 1 , comprising:

7. The pressurized fluid is i) heated, and / or ii) is a compressed gas; and / or iii) steam, and / or iv) a pressure of up to about 30 bar.

8. The method described in claim 7, wherein the compressed gas is compressed air.

9. 10. The method of claim 1, wherein the alloy is selected from the group consisting of bismuth alloys, indium alloys, antimony alloys, tin alloys, lead alloys, and gallium alloys.

10. The method of claim 9, wherein the alloy is a bismuth alloy.

11. In step (b), introducing pressurized fluid into the filling chamber via the pressure inlet and accelerating the bolus such that the bolus is ejected from the filling chamber via the outlet; i) the outlet and pressure inlet are simultaneously opened so that the bolus is ejected upon introduction of the pressurized fluid; or ii) the outlet is first opened and the pressure inlet is second opened so that the bolus is ejected upon introduction of the pressurized fluid; or iii) the pressure inlet is first opened and the pressurized fluid is introduced into the filling chamber, and the outlet is second opened such that the bolus is ejected from the filling chamber when the outlet is opened.

12. The method of claim 1 , wherein the defect is an ongoing leak.

13. The method of claim 12, further comprising a step of deflecting material ejected by the ongoing leak from the path.

14. The method of claim 1 further comprising a cleaning step, wherein a cleaning solution is delivered to the defect.

15. The method of claim 1 , wherein the bolus penetrates the defect.

16. 10. The method of claim 1, further comprising the step of positioning a mold around the defect prior to the step of directing the bolus along a path between the filling chamber and the defect such that the bolus contacts the defect, the mold operable to hold the alloy in contact with the defect.

17. 1. An apparatus for repairing defects, comprising: a fill chamber for holding an at least partially liquid alloy, the fill chamber having a pressure inlet and an outlet; a pressure line fluidly connected to the pressure inlet and connectable to a source of pressurized fluid; An apparatus comprising:

18. 20. The device of claim 17, further comprising a delivery line fluidly connected to the outlet.

19. The delivery line i) flexible, and / or ii) a handle adjacent to the outlet; and / or iii) comprising a robot operable to position the delivery line; and / or iv) equipped with insulation and / or heating devices; and / or 19. The device of claim 18, further comprising: v) a nozzle at the end.

20. The apparatus of claim 19, wherein the handle comprises means for ejecting the at least partially liquid alloy.

21. The apparatus of claim 19, wherein the robot is a snake-arm robot.

22. The apparatus of any one of claims 17 to 21, wherein the filling chamber further comprises an alloy inlet.

23. 23. The apparatus of claim 22, wherein the apparatus further comprises an alloy chamber in fluid communication with the alloy inlet.

24. The apparatus described in claim 23, wherein the alloy chamber includes a heater operable to at least partially melt a portion of the solid alloy.

25. 24. The apparatus of claim 23, wherein the alloy chamber further comprises a balance inlet, and the apparatus further comprises a balance line fluidly connected to the balance inlet.

26. The apparatus of claim 25, wherein the balance line is also fluidly connected to the pressure line.

27. 18. The apparatus of claim 17, wherein the filling chamber comprises insulation and / or a heater.

28. The apparatus of claim 17 , wherein the apparatus further comprises one or more sensors and / or a control system.

29. The device described in claim 28, wherein the one or more sensors include a temperature sensor and / or a pressure sensor.

30. The apparatus of claim 17 , wherein the apparatus further comprises a deflection line.

31. 20. The device of claim 17, wherein the device further comprises a removal line.

32. 20. The apparatus of claim 17, further comprising a housing that houses one or more of the filling chamber, at least a portion of the pressure line, if present, at least a portion of the delivery line, if present, the alloy chamber, if present, at least a portion of the balance line, if present, and the removal line, if present, the housing comprising insulation and / or a heater.

33. 20. Use of the apparatus of claim 17 for applying a bolus of at least partially liquid alloy to a surface defect.

34. 20. Use of the apparatus of claim 17 for applying a spray of at least partially liquid alloy to a surface defect.

35. 18. Use of the device according to claim 17 for applying a jet of at least partially liquid alloy to a surface defect.

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