Leak detection system for hoses and use of such a system for detecting leaks in hoses

Abstract

A leak detection system for a hose(s) through which gas and powder are conveyed, the system comprising: a transport hose (11) which can be connected between a powder feed (40) and a laser metal deposition system (50) and through which a powder with a carrier gas is transported from the powder feed (40) to the laser metal deposition system (50), a protective tube (12) covering the transport tube (11) and defining an annular space (12') between the transport tube (11) and the protective tube (12), a first sealed connection (13) at a first end of the protective hose (12) connecting the protective hose (12) and the transport hose (11) and sealing the annular space (12') at the first end a second sealed connection (13') at a second end of the protective hose (12), which connects the protective hose (12) and the transport hose (11) to each other and seals the annular space (12') at the second end, and at least one pressure change measuring device (14) which is arranged to measure a pressure change in the annular space (12').

Description

This application claims priority to European Patent Application EP25382322.3 filed April 1, 2025. The entire disclosure of European patent application EP25382322.3 is hereby incorporated by reference.TECHNICAL FIELDThe invention relates generally to additive manufacturing in which metal or ceramic powders are used to build up parts, repair or coat surfaces.More particularly, the present invention relates to a leak detection system and the use of such a system for detecting leaks in hoses used for transporting coating powder from a powder supply system to the powder inlets of a laser head nozzle.The object of the invention is to provide a leak detection system which can detect any leak in the hose so that the powder supply system can be stopped and the leak can be repaired, thereby preventing emergency situations such as explosion.PRIOR ARTIn laser beam build-up welding, a laser beam is focused on the surface of a substrate or workpiece while a filler material in the form of wire or powder is supplied through a nozzle to be melted by the laser beam, so that a melt pool is formed on the substrate in which the laser beam impinges on the filler material.In the case of a powder as a filler, the powder is supplied from a powder feeder having a powder container in which the powder is stored and into which a gas is injected to generate pressure in the container. Nitrogen or argon is generally used, and helium is sometimes used. After the powder conveyor is switched on, the gas and powder are conveyed from the powder conveyor through a hose to a laser head, from where it is distributed and injected through a plurality of inlets to a nozzle of the laser head. The powder conveyor must maintain a constant pressure in its hoppers to avoid fluctuations in powder flow which could lead to uneven conveying of the powder.U.S. Pat. Nos. 2006 / 0266740 A1 and 2011 / 0089151 A1 describe laser beam build-up welding systems of this type.In order to ensure a high quality of the laser beam build-up welding process, it is of decisive importance that all powder inlets of the nozzle, which can be a coaxial nozzle or a multi-jet nozzle, are supplied with a uniform and consistent powder flow with respect to the flow rate and speed of the powder particles.However, since the powder must travel a relatively long distance from the powder conveyor to the nozzle, it is important to detect whether there is a leak in the hose. This is especially important because powders with small particle sizes as used in the coating may be explosive due to their large surface area to volume ratio which increases their reactivity. When these fine powder particles float in the air and rub against each other, they can generate static electricity and sparks. In the event of a leak, these sparks, in conjunction with the surface of the particles exposed to the atmospheric oxygen, may lead to rapid oxidation and ignition, which may cause an explosion. Moreover, some powders are made of materials that are inherently reactive with atmospheric oxygen. These materials, such as certain metals or organic compounds, can undergo rapid exothermic reactions upon contact with oxygen, resulting in combustion or explosion. The smaller the particle size, the more reactive the powder is due to the greater surface area available for the reaction.Leaks in hoses transporting these powders may be particularly hazardous because they can generate powder clouds in the ambient air. These clouds contain a high concentration of fine particles suspended in oxygen rich air and provide an ideal environment for rapid combustion or explosion. The risk is particularly high when the leak occurs near an ignition source or when the particles generate static electricity when they escape through the leak.Detection of leaks in powder delivery systems is critical to preventing potentially catastrophic explosions. Early detection can help maintain safe operating conditions, prevent the formation of explosive powder clouds, and minimize the risk of inflammation.Therefore, there is still much room in this field of technology for improvement to ensure leak detection in the tubes that transport the powder and carrier gas from the powder conveyor to the nozzle to ensure safe handling and transport of this type of powder.DESCRIPTION OF THE INVENTIONThe present invention describes systems for detecting leaks in a hose / hoses, used for transporting powders with carrier gases, and thus addresses a critical safety problem in the prior art. The invention also describes the use of such systems. The hose / hoses / hoses represent / represent a considerable risk of explosion if impaired by leaks, since flammable powders and carrier gases can escape into the environment. The present invention ensures early detection of leaks and thus increases operational reliability and prevents failures. The invention overcomes the limitations of existing technologies by offering a reliable and accurate approach to securing industrial processes involving the transport of powders.A first aspect of the invention is a leak detection system for a hose / hoses through which gas and powder is / are transported, the system comprising:a transport hose that can be connected between a powder supply and a laser metal deposition system and through which a powder is transported with a carrier gas from the powder supply to the laser metal deposition system,a protective tube covering the transport tube and defining an annular space between the transport tube and the protective tube,a first sealed joint at a first end of the protective tube, which connects the protective tube and the transport tube to each other and seals the annular space at the first end,a second sealed connection at a second end of the protective tube, which connects the protective tube and the transport tube to one another and seals the annular space at the second end, andat least one pressure change measuring device configured to detect a pressure change or pressure fluctuation in the annular space.The transport hose is a preferably flexible line which is intended for the transport of pulverulent materials. It is preferably made of an antistatic material to prevent the build-up of static electricity and to reduce the risk of ignition in flammable environments. A carrier gas, e.g., nitrogen, liquifies the powder for smooth transport through the tubing.Powder feeding, particularly for laser beam build-up welding, is a device for feeding powdered materials for laser beam build-up welding, although it does not form part of the present invention. It is based on the use of carrier gas to transport the powder to the point of injection into the laser beam. These feeders can process a wide range of particle sizes and powder morphologies.A laser metal deposition apparatus, particularly for laser beam build-up welding, although not part of the present invention, typically includes a high power laser source and a motion control system. The laser serves as a heat source for producing a melt bath on the substrate. Simultaneously, the metal powder is fed through nozzles into the melt bath where it fuses to the substrate surface.In laser beam build-up welding, the term powder refers to fine metal particles, which are usually made of materials such as iron, nickel, cobalt or ceramic-based alloys. These powders are selected according to the desired properties of the layer to be coated, e.g. wear resistance, corrosion resistance or heat resistance. The powder is applied to the workpiece surface with the aid of a carrier gas, which ensures precise metering and the transport of the powder into the melt bath produced by the laser. Common carrier gases are argon, helium and nitrogen, which are selected for their inertness and ability to prevent oxidation during the process.The protective tube surrounding the transport tube protects the inner transport tube from abrasion, high temperatures and other external factors that could impair its integrity or functionality. In addition, the protective tube forms an annular space between the transport tube and itself, in which the pressure remains constant as long as no leakage occurs in the transport tube. This serves to monitor the pressure in the annular space and thus to detect leaks which may occur in the transport hose. In one embodiment of the invention, the protective tube is also flexible. In one embodiment of the invention, the protective tube is also made of an antistatic material and may additionally have ATEX approval, thereby ensuring safety by preventing static electricity build-up and minimizing explosion risks in flammable environments.In view of the above, the annulus refers to the cavity or gap between the two concentric cylindrical objects, the two hoses in the present invention. The annulus may be uniformly shaped when the inner and outer tubes are perfectly aligned, but may also be irregular due to alignment errors, diameter variations or deformations of the objects. In any event, the function of the system is not impaired.The sealed connections between the two hoses are connection points that ensure a leak-free and secure interface between them. In one embodiment of the invention, the sealed connections include a sealing mechanism, such as O-rings, seals or special fittings, to provide a tight seal that prevents the escape of gas or powder. The sealed joints withstand pressure and maintain their integrity over time. In one embodiment of the invention, the sealed connections also include threaded or clamping fittings to provide additional stability and to reinforce the sealThe pressure change measuring device is configured to measure and monitor pressure changes in the limited area between the hoses, i.e. the annulus. In one embodiment of the invention, the pressure change measurement device uses a differential pressure measurement technique that compares the annulus pressure to a reference pressure and converts the physical pressure changes to electrical signals that can be processed and analyzed to detect anomalies or trends. In an embodiment of the invention, the pressure fluctuation measuring device measures the pressure over time, and a user determines whether a pressure fluctuation has occurred. In one embodiment of the invention, the pressure fluctuation measuring device compares the pressure at each point in time with a reference pressure and determines the pressure fluctuation. In this way, an external user can check whether the change is equal to zero or whether the pressure in the annulus has changed. In one embodiment, the pressure change measurement device may generate a signal when a pressure change above a predetermined threshold has occurred, thereby avoiding the need for monitoring by the user.The pressure in the annular space can increase or decrease in the event of a leak in the transport hose. The pressure in the annular space increases if there is a leak in the transport hose and air or inert gas accumulates from the transport hose in the annular space. The pressure in the annular space falls if a gas with a specific pressure is already present in the annular space and a leak occurs in the transport hose and the pressure in the transport hose is lower, the gas present in the annular space is introduced into the transport hose, as a result of which the pressure in the annular space falls. In both cases, the pressure change measuring device measures the pressure change or pressure fluctuation that would be detected in both cases.The pressure measurement in the annulus is performed at a certain frequency that is sufficiently high to determine that a leak has occurred within an appropriate time interval. This frequency may be, for example, every 5 seconds, every 2 seconds, every second, every 0.5 seconds, every 0.1 seconds or every 0.05 seconds, etc. In any case, the frequency of the pressure change or pressure fluctuation measurement can be adapted to the respective individual case, for example depending on the requirements of the system or the requirements required for compliance with the ATEX regulations. In addition, the pressure change measuring device has sufficient resolution, so that in the case of a leak, even a small one, this can be detected. In one embodiment of the invention, the pressure change measuring device has an accuracy of 0.1 bar, 0.01 bar, 0.001 bar or 0.0001 bar.In one embodiment of the invention, the system comprises a single pressure change measurement device. In one embodiment of the invention, the system comprises two or more pressure change gauges arranged along the protective tubeThis invention provides a simple and effective approach to detecting leaks in transport hoses. This is a sensor-based system that can detect pressure changes due to potential leaks, which allows early detection.In one embodiment of the invention, the system further comprises a control unit which is connected to the pressure change measuring device and is configured to trigger an alarm and / or to send a stop signal to the powder conveyor if a pressure fluctuation above a predefined threshold value is detected in the annular space.If a leak is detected in the transport hose, an alarm can be triggered, which can be carried out, for example, acoustically, illuminated or in the form of a message to a computer. Additionally or alternatively, a stop signal may be sent to the powder conveyor to stop production and thus prevent the leak from continuing and explosion occurring. This stop signal can generally be sent to any system that has control over the suspension of the coating process.In one embodiment of the invention, the pressure change measuring device and the control unit are connected via wired connections. In one embodiment of the invention, the pressure change measurement device and the controller are connected via wireless connections.The control device enables a stronger automation of the leak detection or leak search, since the user no longer has to monitor the pressure sensor values.In one embodiment of the invention, the system further comprises pressure relief means connected to the protective tube for relieving the pressure in the annulus when it exceeds a certain limit.Pressure relief devices are devices for relieving excess pressure in a system to prevent damage or failure. In one embodiment of the invention, the pressure relief means is a pressure relief valve. These devices are designed to open automatically when the pressure in a system exceeds a predetermined safe limit, so that excess liquid or gas can escape and the pressure is thereby reduced to a safe level. This ensures that the protective tube does not explode due to excessive pressure even if the powder feeder is not stopped fast enough or if the leak is large and the pressure in the annular space rises rapidly.In one embodiment of the invention, the protective tube is an antistatic tube, e.g. a polyurethane tube, a flexible metal tube or a corrugated tube.Which type of hose is used depends mainly on the type of powder being conveyed. An antistatic hose is, for example, a special flexible hose which reliably dissipates static electricity during material transport. It has been developed to prevent the build-up of electric charges which might cause sparks, fires or explosions in industrial environments. The flexible hose has the advantage that it is easier to handle and to wind around the transport hose.In one embodiment of the invention, the system further comprises a gas injector connected to the protective hose and configured to inject an inert gas into the annulus until a predetermined pressure is reached in the annulus.The gas injection device can be, for example, an injection valve which is connected to the protective hose and through which an inert gas, such as nitrogen, can be injected before the system is put into operation. In this manner, the initial annulus pressure is known and this initial pressure is used by the pressure change meter as a reference pressure to which the pressure measured at each time is compared to determine if a pressure change has occurred. Furthermore, introducing an inert gas into the annular space has the advantage that an inert atmosphere is created which prevents explosion even if the transported powder escapes into the annular space.A second aspect of the invention is a leak detection system for a hose / hoses through which gas and powder is / are transported, the system comprising:a transport hose that can be connected between a powder supply and a laser metal deposition system and through which a powder is transported with a carrier gas from the powder supply to the laser metal deposition system,a protective tube covering the transport tube and defining an annular space between the transport tube and the protective tube,a first sealed joint at a first end of the protective tube, which connects the protective tube and the transport tube to each other and seals the annular space at the first end,a second sealed connection at a second end of the protective tube, which connects the protective tube and the transport tube to one another and seals the annular space at the second end,gas injection means connected to the protective tube and configured to continuously blow air or an inert gas into the annular space, anda flow meter connected to the protective tube downstream of the gas injection means(s) and configured to receive the air or the inert gas injected into the annular space and to detect the presence of powder.The transport tube, powder conveyor, laser metal coating equipment, protective tube, sealed joints and gas injection means are the same as defined above.In this second aspect of the invention, the gas injection means continuously inject air or an inert gas into the annulus to create a flow which, when a leak occurs in the transport hose, draws the powder conveyed into the annulus to the flow meter.A flow meter for detecting powder in a gas serves to measure the flow rate or the amount of powder transported in a gas stream. It is usually used to monitor and control the real-time mass flow of powders in pipes or hoses. In one embodiment of the invention, the flow meter is based on electrostatic measurement, baffle plate detection or capacitive measurement in order to detect the interaction between the powder particles and the sensor. The acquired data is processed into output signals representing the flow rate or the total mass transported. These flow meters can be adapted to different particle sizes and flow ranges.In one embodiment of the invention, the flow meter measures the amount of powder in the air or inert gas stream passing through the flow meter. In this way, an external user can check whether the powder amount is zero or whether a certain amount of powder is present. In one embodiment, the flowmeter may generate a signal when a particular amount of powder above a predetermined threshold has been detected, thereby avoiding the need for monitoring by a user.The flow measurement is performed at a certain frequency that is sufficiently high to determine that a leak has occurred within an appropriate time interval. This frequency can be, for example, every 5 seconds, every 2 seconds, every second, every 0.5 seconds, every 0.1 seconds or every 0.05 seconds. In any case, the frequency of the flow measurement can be adapted to the respective individual case, for example depending on the requirements of the system or the requirements required to comply with the ATEX regulations. In addition, the flow meter has sufficient resolution so that in the event of a leak, even a small one, this can be detected. In one embodiment of the invention, the flowmeter has an accuracy range of 0.1%-5%, or of 0.2-3%, or of 0.1%-0.5%.Air is a mixture of gases present in the atmosphere, such as nitrogen, oxygen, carbon dioxide, argon and others. Inert gas is a gas that does not readily undergo chemical reactions with other materials and prevents undesired reactions such as oxidation. Examples of inert gases are inert gases (helium, neon, argon, krypton, xenon and radon), nitrogen and carbon dioxideIn one embodiment of the invention, the system further comprises a control device, which is coupled to the flow meter and is configured to trigger an alarm and / or to send a stop signal to the powder conveyor when powder is detected.The same definitions and advantages explained with respect to the controller of the first aspect of the invention can also be applied to the controller of this second aspect of the invention.In one embodiment of the invention, the system further comprises a fluid separation device coupled to the flow meter for draining the air or the inert gas and for retaining the powder, and a powder depot coupled to the fluid separation device for storing the filtered powder.In one embodiment of the invention, the fluid separation means comprises a filtered aerator which receives the stream of air or inert gas, traps the powder contained therein and discharges the powder-free air or gas.In one embodiment of the invention, the fluid separation means comprise a cyclone separator which produces a vortex by utilizing the effects of rotation and gravity to separate the mixture of air or inert gas and powder. In one embodiment of the invention, the upper part of the cyclone separator, through which the powder-free air or the inert gas exits, is fed to a suction system.The powder depot is coupled to the aerator with filter or to the cyclone separator, so that the powder can be stored in the depot after filtering. The air velocity decreases in the interior of the depot or container, so that the powder particles can separate from the air stream due to the force of gravity or the centrifugal forces. The separated powder is collected at the bottom of the container or depot, while the purified air exits through the aeration filter in order to avoid impurities.In one embodiment of the invention, the system further comprises a second pressure relief means connected to the powder depot and arranged to relieve the pressure when it is above a certain threshold.As with the first pressure relief means, the second pressure relief means is a means for relieving excess pressure in a system to prevent damage or failure. In one embodiment of the invention, the second pressure relief means is a pressure relief valve which opens automatically when the pressure in the powder tray exceeds a predetermined safe limit value so that air or gas can escape and the pressure is thereby reduced to a safe level.The system described in the second aspect of the invention detects the presence of a leak by identifying the presence of the powder which, upon exiting the transport hose, is transported through the annulus carried by the injected air or inert gas and measured in the flow meter.In one embodiment of the invention, the system further comprises at least one pressure change measuring device, configured to detect a pressure change in the annular space.This embodiment of the invention provides the above advantages, but in addition the system is redundant in this case because it includes both the pressure change meter and the flowmeter, which enables higher accuracy in detecting leaks and redundancy in the system in the event that either of the devices fails.In one embodiment of the invention, the control device is furthermore connected to the pressure change measuring device and is configured to trigger an alarm and / or to send a stop signal to the powder conveyor if a pressure change in the annular space is detected.In one embodiment of the invention, the controllers defined above in the various aspects of the invention comprise at least one processor and a memory. In one embodiment of the invention, the controller is located in the vicinity of the system. In one embodiment of the invention, the computer system is located at a remote location.A third aspect of the invention is a use of a leak detection system according to the first aspect of the invention for detecting leaks in a hose / hoses through which gas and powder / s is / are transported, the use comprising:monitoring the pressure in the annular chamber with the at least one pressure change measuring device andtriggering an alarm and / or sending a stop signal to the powder conveyor if a pressure fluctuation above a specific threshold value is detected in the annular chamber.An embodiment of the invention relates to the use of a leak detection system according to the first aspect of the invention, in particular according to the embodiment in which the system comprises a gas injection device, and wherein the use further comprises, prior to monitoring the pressure in the annular space:injecting an inert gas into the annulus with the gas injector until a predetermined initial pressure is reached in the annulus, and closing the gas injector,measuring, wherein the pressure change measurement means the initial pressure in the annular space,and wherein the alarm is triggered and / or a stop signal is sent to the powder conveyor if a pressure change above a certain threshold value with respect to the output pressure is detected in the annular chamber.A fourth aspect of the invention is a use of a leak detection system according to the second aspect of the invention for monitoring a leak in a hose through which gas and powder is / are transported, the use comprising:continuously blowing air or an inert gas into the annular space with the gas blowing agent,monitoring the injected inert gas in the flow meter and triggering an alarm and / or sending a stop signal to the powder conveyor when the flow meter detects powder in the inert gas.In one embodiment of the invention, the leak detection system according to the second aspect of the invention is a system comprising at least one pressure change measuring device. In this embodiment, the use thereof further comprises:monitoring the pressure in the annular chamber in the at least one pressure change measuring device andtriggering an alarm and / or sending a stop signal to the powder conveyor if a pressure change or pressure fluctuation is detected and / or if the flow meter detects powder.Other advantages and features of the invention will become apparent from the following detailed description and are set forth with particularity in the appended claims.BRIEF DESCRIPTION OF THE DRAWINGSTo complete the description and to facilitate understanding of the invention, a series of drawings are included. These drawings form part of the specification and illustrate an embodiment of the invention which is not to be taken as limiting the scope of the invention, but merely as an example of a possible embodiment of the invention. The drawings include the following figures: Fig. 1 shows a leak detection system for powder and gas hoses. Fig. 2 shows a second embodiment of the leak detection system for powder and gas hoses. FIG. 3 shows a leak detection system for hoses through which gas and powder are transported. FIG. 4 shows a second embodiment of the leak detection system. FIG. 5 is a sectional view showing an embodiment of the pressure change measuring device. FIG. 6 is a sectional view showing another embodiment of the pressure change measuring device. FIG. 7 shows a flow chart of a use of a system according to the invention for detecting leaks in powder and gas hoses according to a first embodiment of the invention. FIG. 8 shows a flow chart of a use of a system according to the invention for detecting leaks in powder and gas hoses according to a second embodiment of the invention. Figure 9 shows a flow chart of a use of a system according to the invention for monitoring a leak in a hose through which a gas and powder are transported. FIG. 10 shows a flow chart of a use of a system according to the invention for monitoring a leak in a hose through which a gas and powder are transported in a second embodiment of the invention.DESCRIPTION OF AN EMBODIMENT OF THE INVENTIONThe following description is not to be taken in a limiting sense, but is merely intended to describe the principles of the invention. The next embodiments of the invention will be described by way of example with reference to the above drawings which show apparatus and results according to the invention.FIG. 1 is a front perspective view of a leak detection system 10 according to a particular embodiment of the invention. It should be appreciated that the system 10 of FIG. 1 may include additional components and that some of the components described herein may be removed and / or modified without compromising the scope of the described system 10. In addition, the implementation of the system 10 is not limited to this embodiment.The leak detection system 10 consists of a transport hose 11 which can be connected between a powder feed 40 and a laser metal deposition system 50, also known as a laser build-up welding system. A powder suspended in a carrier gas (argon or nitrogen) is transported through the transport hose 40. The powder may be a metal powder (stainless steel, silver, copper, nickel, titanium, cobalt, metal oxides, etc.), ceramic powder (carbides, nitrides, oxide ceramics, etc.), or a combination of both. The metal powder may be composed of a single metal component, a combination of metal components, alloys, or any combination thereof. Ceramic powder may be made from a single ceramic component or a combination of ceramic components. In the drawings, it is not shown that the transport hose 11 is hollow for ease of understanding, but it is obvious that air or inert gas and powder circulate therein.The powder is stored in a feed hopper in powder feed 40, and a stream of powder and carrier gas is passed through transport tubing 11 which carries it to laser metal coating equipment 50. There, it is passed through a nozzle 51 to be applied to a workpiece. The transport tube 11 is made of an antistatic material to prevent the build-up of electric charges.A second hose, in particular a protective hose 12, covers the transport hose 11 over its entire length, i.e. from the powder feed 40 to the laser metal deposition system 50. In one embodiment of the invention, the thickness of the annular portion is 0.5-3 mm. As can be seen, this region defines an annular space 12' with a small cross section because in this way, in the event of a leak, the pressure in the annular space 12' rises rapidly and the pressure change or pressure fluctuation is detected almost immediately. In any event, the thickness of the annulus 12' also depends on the type of hoses 11, 12 usedThe transport hose 11 and the protective hose 12 are connected to sealed connections 13, 13', which seal the annular space 12'. A first sealed connection 13 is located at a first end of the hoses 11, 12 which seals the annulus 12' at the first end and a second sealed connection 13' is located at a second end of the hoses 11, 12 which seals the annulus 12' at the second end. The first end is connectable to the powder conveyor or powder feed 40 and the second end is connectable to the laser metal deposition apparatus 50. The manner in which the hoses 11, 12 are connected to said elements is not part of the invention, but also these connections are sealed. Thus, the sealing connections 13, 13' seal the first and second ends of the protective tube 12 with the first and second ends of the transport tube 11. In this way, the annular space 12' between the two hoses 11, 12 is completely sealed. If the transport hose 11 is not leaking, the pressure in the annular space 12' remains substantially constant.As shown in FIG. 1, the leak detection system 10 further comprises a pressure change measuring device configured to detect any pressure change or pressure fluctuation in the annular space 12'. That is, whether the pressure increases or decreases.FIGS. 5 and 6 show an embodiment of the pressure change measuring device. In this embodiment, the pressure change measuring device consists of a tube connection 22 made of metal, which is located between two parts of the protective tube 12. The protective hose 12 is connected to the hose connection 22 by two threaded connections 23 or fittings, one on each side. As can be seen in the two figures, the transport hose 11 continues to run unimpeded, just like the annular space 12' which is retained in the interior of the hose connection 22. The screw connections 23 ensure that no leaks are produced. In FIG. 5, a pressure sensor 14 is attached to the hose connector 22. No air or gas can escape from the annular space 12', but the pressure sensor 14 can monitor all pressure changes or pressure fluctuations that can occur in the annular space 12'. In the embodiment shown in FIG. 5, a pressure relief valve 15 is integrated into the pressure sensor 14, so that when a pressure above a specific threshold value is reached in the annular chamber 12', the latter can be reduced. In FIG. 6, the pressure relief valve 15 is attached to the hose connection 22 independently thereof.In the embodiment shown in FIGS. 1 and 2, the pressure change measuring device comprises a pressure sensor 14 which is arranged in the interior of the annular space 12' and comprises a pressure indicator element which is located outside the protective tube 12 so that a user can read the measured pressure in the annular space 12'. Therefore, the pressure sensor 14 is inserted through the protective tube 12 and is completely sealed so that air does not leak to the outside from the annular space 12'.If a leak occurs in the transport hose 11, the carrier gas circulating through the transport hose 11 and perhaps even some powder particles, depending on the size of the leak, emerge from the transport hose 11 and begin to fill the protective hose 12. In this case, the pressure in the annulus 12' begins to increase and the pressure sensor 14 provides a measurement which is higher than the pressure measurement without leakage. The pressure sensor 14 has sufficient resolution to detect a pressure change in the annulus 12' regardless of the size of the leak. When a user detects a change in pressure in reading the measurements of the pressure sensor 14, he may stop the powder supply 40 and stop production to attach the transport hose 11.However, as shown in FIG. 1, for improved monitoring of the pressure in annulus 12', system 10 also includes a controller 30 connected to pressure sensor 14 and receiving the pressure measurements of pressure sensor 14. If the controller 30 detects a deviation upon receipt of the pressure measurements, it generates an alarm. Alternatively or additionally, it can send a stop signal to the powder feed 40, so that the leak can be corrected and a risk of explosion can be prevented. The deviation detected by the control device 30 can consist in the pressure being above a specific value or below a specific value. The alarm may be, for example, a light and sound alarm.In the event that the pressure in the annular chamber 12' rises very rapidly, the system 10 also comprises pressure relief devices, in particular a relief valve 15, which is connected to the protective hose 12 and connects the annular chamber 12' to the outside world. If the pressure in the annular chamber 12' reaches a certain limit value, the pressure relief valve 15 opens and discharges air to the outside, so that the pressure in the annular chamber 12' drops and an explosion of the protective hose 12 is prevented. In this case, the pressure relief valve 15 can take up its work when the pressure in the annular chamber 12' reaches 3 bar, for example.Use of the above-described system 10 for detecting leaks in powder and gas hoses is illustrated in FIG. 7. As shown at reference numeral 100, a leak detection system 10 is provided as previously described. Then, 101 a powder is transported with a carrier gas through the transport hose 11 from the powder supply 40 to the laser metal deposition apparatus 50. In this case, the transport 101 refers to initiating the circulation of powder and gas through the transport hose 11.Next, a monitoring 102 of the pressure in the annular space 12' takes place with the pressure sensor 14. As already mentioned, the annular space 12' is completely sealed off, and if the transport hose 11 does not have any leakage, the pressure measured by the pressure sensor 14 is constant. The pressure sensor 14 sends the pressure measurements to the control device 30, and if a leak occurs in the transport hose 11, the pressure in the annular chamber 12' changes. It may rise or fall. In either case, pressure sensor 14 continues to send the pressure measurements to controller 30, and when the controller detects a pressure change, it triggers alarm 104 to stop the system and remedy the leak. The deviation must exceed a certain threshold value in order for the control device 30 to recognize that it is a leak. If, for example, the pressure in the interior of the transport hose 11 is 0.5 bar, the control device 30 detects a leak if the pressure change or pressure fluctuation in the annular chamber 12' is more than 0.01 bar if the pressure sensor 14 has an accuracy of 0.01 bar.Figure 2 shows a second embodiment of the leak detection system 10, except for the elements described above, the system 10 also comprises means for gas injection, e.g. a gas injection valve 16 connected to the protective hose 12 and having access to the annular space 12'. The interface between the protective hose 12 and the gas injection valve 16 is completely sealed, and no air can enter or leave the annular space 12'.FIG. 8 shows a flow diagram of a use of the system of FIG. 2 for detecting leaks in a hose / hoses. In this case, the annular space 12' is filled with an inert gas through the gas injection valve 16 before the powder supply 40 starts charging the laser metal deposition apparatus 50 through the transport hose 11. Thus, the annulus 12' is at a known pressure controlled by the introduction of a certain amount of inert gas. While the inert gas is introduced into the annular space 12' through the gas injection valve 16, the pressure sensor 14 measures the pressure in the annular space 12', and as soon as a desired pressure is reached, the gas injection is ended and the gas injection valve 16 is closed. In this way, the annular space 12' is filled with an inert gas at a known pressure. The controller 30, which is connected to the pressure sensor 14, regards this pressure as the output pressure. Then, the powder feeder 40 is activated, and the powder is conveyed through the conveying hose 11. If a leak occurs in the transport hose 11 or even in the protective hose 12, the pressure measured by the pressure sensor 14 deviates from the initial pressure. The controller 30 registers this deviation and triggers an alarm 104 to stop and repair the system.FIG. 3 shows a leak detection system 10 for a hose / hoses through which gas and powder / s is / are transported. Like the foregoing system, the present system 10 also includes a transport hose 11 connectable between a powder supply 40 and a laser metal deposition apparatus 50, and a protective hose 12 covering the transport hose 11 in its entirety and defining an annular space 12'. Both hoses 11, 12 are also sealed with a first and a second sealing connection 13, 13'. As shown in FIG. 3, the system 10 further includes gas injection means, which in this case includes a gas injection valve 16 coupled to the protective hose 12 for introducing air or an inert gas into the annulus 12', and a gas injector 17 in fluid communication with the gas injection valve 16.As seen in FIG. 3, the gas injector 16 is located closer to the first sealed connection 13 and thus upstream of the protective hose 12. In this manner, the flow meter 18 receives the inert gas introduced into the annular space 12'. The flow meter 18 is configured to detect the presence of powder in the inert gas or the air flow that occurs when a leak occurs in the transport hose 11.In order to avoid that air or inert gas possibly containing powder is released in the case of a leak in the transport hose 11, the system 10 also comprises a powder depot 19 which is connected to the flow meter 18 in order to store the powder possibly present in the gas. As shown in FIG. 3, the powder depot 19 comprises fluid separation means which in the present case comprise an aerator with filter 20 in order that the inert gas can be discharged but any powder present is retained. In case a greater leak occurs in the transport hose 11 and the pressure in the powder depot 19 rises rapidly, it also comprises a second pressure relief means, such as a pressure relief valve 21, connected to the powder depot 19 and relieving the pressure in the powder depot 19 once it has reached a certain limit, in order to avoid explosion or malfunction. If the pressure in the powder depot 19 reaches 3 bar, for example, the second pressure relief valve 21 opens.In addition, the system 10 may comprise a recirculation device (not shown in the figures) for recirculating the air or, in particular, the inert gas present by the aerator with filter 20 and reinjection into the annular space 12' through the injection valve 16.In the system 10 shown in FIG. 3, the flow meter 18 is connected to a controller 30, and when the presence of powder in the gas is detected, an alarm is triggered. Additionally or alternatively, a stop signal is sent to the powder supply 40 so that production is stopped and the leak can be repaired.FIG. 9 shows a flow chart of use of the system 10 of FIG. 3 for monitoring a leak in a hose. In this case, while the powder feeder 40 supplies 101 to the laser metal deposition apparatus 50 through the transport hose 11, an inert gas is continuously injected into the annular space 12' by the gas injector 105'. This internal gas is collected in the flow meter 18. If a leak occurs in the transport hose 11, a part of the powder that is supplied or conveyed leaves the transport hose 11 and enters the annular space 12'. It is then conveyed downstream to the flow meter 18 which is configured to monitor 102' the presence of the powder in the inert gas or in the air. If the presence of powder is detected, the controller receives a signal 103 from the flow meter 18 and triggers an alarm 104 to stop production. Additionally or alternatively, the controller 30 sends a stop signal to the powder supply to allow the leak to be repaired.FIG. 4 shows a further embodiment of the system from FIG. 3, which, in addition to the elements described above, also comprises a pressure sensor 14 for monitoring the pressure in the annular space 12'.FIG. 10 is a flow diagram of a use for monitoring a leak in a hose / hoses in which a system as shown in FIG. 4 is provided 100. In this case, as soon as the powder feeder 40 is activated and thus begins to feed powder with a carrier gas through the transport hose 11 to the laser metal deposition system 50, the gas injector 17 begins to continuously blow in 105' an inert gas or air through the gas injection valve 16 into the annular space 12'. The inert gas or air circulates through annulus 12' until it reaches flowmeter 18 and exits system 10 through the aerator with filter 20.If a leak occurs in the transport hose 11, the system 10 offers two possibilities for detecting it. On the one hand, the pressure sensor 14 constantly monitors the pressure in the annular chamber 12'. When a leak occurs, the pressure changes. At this time, the controller 30 detects the pressure change supplied from the pressure sensor 14 and triggers an alarm 104. Second, the flow meter 18 continuously monitors the flow of inert gas or air 102'. If a leak occurs, it is possible that some powder escapes from the transport hose 11. In this case, the flow meter 18 detects the presence of powder in the inert gas, and the controller 30 also triggers the alarm 104. In this case, the powder accumulates in the powder depot 19 while the inert gas or air stream is filtered and exits the system through the aerator with filter 20.If a large leak occurs, as a result of which the pressure in the annular space 12' rises rapidly, the system 10 comprises the two pressure relief valves 15, 21, which are illustrated in FIG. 4 and are connected to the protective tube 12 and the powder depot or bearing 19. In this way, the pressure in the system 10 is relieved and an explosion of the protective tube 12 is prevented.The numerical signs shown in FIGS. 1 to 10 and the corresponding constituent elements are listed below:10 Leak detection system 11 Transport hose 12 Protective hose 12' Annular space 13, 13' Sealed joints 14 Pressure sensor 15 Pressure relief device 16 Means for gas injection 17 Gas injection valve 18 Flow meter 19 Powder depot 20 Means for liquid separation 21 Second pressure relief device 22 Hose connection 23 Threaded connection 30 External computer 40 Powder supply 50 Laser metal separation systems 51 Nozzle 100 Provision of 101 Transport 102 Monitoring 103 Receiving 104 Triggering of an alarm 105, 105' Injection 106 Termination 107 MeasurementReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedEP 25382322.3

[0001] US 2006 / 0266740 A1

[0007] US 2011 / 0089151 A1

[0007]

Claims

A leak detection system for a hose / smoke through which gas and powder is / are transported, the system comprising: a transport hose (11) connectable between a powder supply (40) and a laser metal deposition plant (50) and through which powder is transported with a carrier gas from the powder supply (40) to the laser metal deposition plant (50), a protective hose (12) covering the transport hose (11) and defining an annular space (12') between the transport hose (11) and the protective hose (12), a first sealed connection (13) at a first end of the protective hose (12), connecting the protective tube (12) and the transport tube (11) and sealing the annular space (12') at the first end, a second sealed connection (13') at a second end of the protective tube (12), connecting the protective tube (12) and the transport tube (11) to each other and sealing the annular space (12') at the second end, and at least one pressure change measuring device (14) configured to measure a pressure change in the annular space (12').The system according to claim 1, further comprising a control unit (30) connected to the at least one pressure change measuring device (14) and configured to trigger an alarm and / or to send a stop signal to the powder supply (40) if a pressure change above a predefined threshold is detected in the annulus (12').The system according to any one of the preceding claims, wherein it further comprises pressure relief means (15) connected to the protective tube (12) for relieving the pressure in the annulus (12') when it is above a predefined threshold.The system of any preceding claim, wherein the protective tube (12) is selected from among an antistatic tube, a flexible metal tube, and a corrugated tube.The system according to any of the preceding claims, wherein it further comprises a gas injection means (16) connected to the protective hose (12) and configured to inject an inert gas into the annulus (12') until a predetermined pressure is reached in the annulus (12').A leak detection system for a hose / hoses through which gas and powder is / are transported, the system comprising: a transport hose (11) connectable between a powder supply (40) and a laser metal deposition plant (50) and through which powder is transported with a carrier gas from the powder supply (40) to the laser metal deposition plant (50), a protective hose (12) covering the transport hose (11) and defining an annular space (12') therebetween, a first sealed connection (13) at a first end of the protective hose (12) connecting the protective hose (12) and the transport hose (11) and sealing the annular space (12') at the first end, a second sealed connection (13') at a second end of the protective hose (12), connecting the protective tube (12) and the transport tube (11) to each other and sealing the annular space (12') at the second end, gas injection means (16) coupled to the protective tube (12) and configured to continuously inject air or an inert gas into the annular space (12'), and a flow meter (18) coupled to the protective tube (12) downstream of the gas injection means(s) (16) and configured to receive the air or the inert gas injected into the annular space (12') and detect the presence of powder.The system of claim 6, further comprising a controller (30) coupled to the flow meter (18) and configured to trigger an alarm and / or send a stop signal to the powder supply (40) when powder is detected in the air or inert gas entering the flow meter (18).The system of claim 6 or 7, further comprising a fluid separation device (20) coupled to the flow meter (18) for venting the air or inert gas and retaining the powder, and a powder depot (19) coupled to the fluid separation device (20) for storing the filtered powder.The system according to claim 8, further comprising a second pressure relief device (21) connected to the powder depot (19) and configured to relieve the pressure in the powder depot (19) when it is above a certain threshold.The system according to any of claims 6 to 9, wherein it further comprises at least one pressure change measurement device (14) configured to detect a pressure change in the annular space (12').The system according to claim 10, wherein the controller (30) is further connected to the at least one pressure change measuring device (14), and wherein the system is further configured to trigger an alarm and / or to send a stop signal to the powder supply (40) if a pressure change or pressure fluctuation above a certain threshold value is detected in the annulus (12').Use of a leak detection system according to one of claims 1 to 5 for detecting leaks in a hose / hoses through which gas and powder is / are transported, comprising: monitoring (102) the pressure in the annular space (12') with the at least one pressure change measuring device (14), and triggering an alarm (104) and / or sending a stop signal to the powder feed (40) if a pressure change or pressure fluctuation above a specific threshold value is detected in the annular space (12').Use according to claim 12, using a leak detection system according to claim 5, prior to monitoring (102), comprising: injecting (105) an inert gas into the annular space (12') with the gas injection means (16) until a predetermined initial pressure is reached in the annular space (12'), and closing (106) the gas injection means (16), measuring (107) the initial pressure in the annular space (12') with the at least one pressure change measuring device (14), and wherein the alarm (104) is triggered and / or a stop signal is sent to the powder feed (40) if a pressure change or pressure fluctuation above a specific threshold value with respect to the initial pressure is detected in the annular space (12').Use of a leak detection system according to any one of claims 6 to 11 for monitoring a leak in a hose / hoses through which gas and powder is / are transported, comprising: continuously blowing (105') air or inert gas with the gas blowing means (16) into the annular space (12'), monitoring (102) the injected air or inert gas in the flow meter (18), and triggering an alarm (104) and / or sending a stop signal to the powder feed (40) when the flow meter (18) detects powder.Use according to claim 14, using a leak detection system according to claim 10 or 11, further comprising: monitoring (102) the pressure in the annular space (12') in / with the at least one pressure change measuring device (14), and triggering an alarm (104) and / or sending a stop signal to the powder conveyor (40) if a pressure change or pressure fluctuation above a certain threshold value is detected in the annular space (12') and / or if the flow meter (18) detects powder.

Images