DE202021003961U1 - Device for detecting a leak in a fluid-carrying element of a heat exchange device - Google Patents

Abstract

Leak detection system with a gas leak detector (24), a sniffer probe (22) and a 3D sensor (34), for detecting a leak in a fluid-carrying element (16, 18) of a heat exchange device (12), the leak detection system being designed to do the following Steps to perform:
a) generating a point cloud (44) of the heat exchange device (12) in a three-dimensional virtual space (48) using a 3D sensor (34), each of the points representing a surface point (46a) on the outer surface of the heat exchange device (12),
b) searching within the point cloud (44) for structures (50) that correspond to tubes with a predefined outside diameter,
c) searching the obtained structures (50) for a region of interest (52) in which the diameter or the direction of the tube changes,
d) once an area of interest (52) is found, determining an approach path (58) for approaching a sniffer probe (22) of a gas leak detector (24) to the area of interest (52) within the point cloud (44), and
e) automatically physically approaching the sniffer probe (22) to a test area (20) of the heat exchange device (12) along the approach path (58), the test area (20) corresponding to the area of interest (52) within the point cloud (44).

Description

The invention relates to a leak detector for detecting leaks in a test object.

A leak detector is eg in DE 10 2005 022 156 A1 (Inficon) described. This leak detector includes a probe whose probe tip is placed at predetermined inspection regions of an inspection object. The test object is filled with a test gas, eg helium. Escaping test gas is sucked in by a base unit via the probe tip and fed to a test gas detector, which can be designed as a mass spectrometer, for example.

When using leak detectors, the test object, e.g. an air conditioning system or the cooling unit of a refrigerator, is filled with a test gas and a sniffer probe can be used to detect whether test gas is escaping from the test object. In an industrial quality inspection of products, the probe tip is applied to specific inspection areas of the inspection object where there is a possibility of a leak. The probe is moved manually to the test areas. With this process, it is difficult to check whether the probe tip has been moved to all relevant inspection areas of the inspection objects. An operator may inadvertently skip certain test areas or skip other test areas that he/she subjectively judges to be uncritical.

US patent no. 4,945,305 (Ascension) describes a positioning system that includes a transmitter for generating a pulsed DC magnetic field and a receiver that is placed on the object. This method is particularly useful for determining a current position, comparing it to a desired position, and providing feedback. No interference is caused by non-magnetic objects in the line of sight between the transmitter and receiver. Residual interference from large masses of magnetizable material, such as an airend and chiller, can be eliminated by calibration since the assembly under test is static. This method has proven to be particularly useful for realizing the disclosure.

WO 2009/016160 A1 describes a leak detector having a base unit connected to a probe by a tube. The probe tip is placed on test zones or test areas of the test object. If tracer gas escapes from the test object, this is detected by a tracer gas detector in the base unit. A position determination system is provided, which has a transmitter, a receiver, which is arranged in the probe, and a feed and evaluation unit. This monitors and confirms the presence of the probe tip in each test area.

It is known in the field of automation to acquire digital data from physical objects using a 3D sensor, thereby obtaining a cloud of points in a 3-dimensional virtual space, each point representing a surface point on the outer surface of the physical object . Robots used in the automation industry, such as in the automated manufacture of products, such as cars, are controlled by software algorithms using the digital data collected. This is commonly done to sense the perimeter or areas of the entire physical object to locate, grasp, move or relocate the object, or to paint the outer surface of the object using a paint spray robotic arm, for example in the vehicle manufacturing industry.

Sniffing leak detection on heat exchange devices such as refrigerators, air conditioners, heat pumps, etc. is part of the quality inspection of heat exchange devices. A human operator must visually identify the relevant test areas on the heat exchanger, such as liquid-carrying pipes, and manually move the probe to the test areas one at a time. This type of sniffer leak detection on heat exchange devices is time consuming and prone to human factor errors such as missing test areas or not sufficiently approaching a test area with the sniffer probe.

The object of the invention is to create a more reliable and faster detection of a leak in a fluid-carrying element of a heat exchange device.

The device according to the invention is defined by the features of independent claim 1 .

1. a) eine Punktwolke in einem virtuellen 3-dimensionalen Raum aus der Wärmetauschvorrichtung unter Verwendung eines 3D-Sensors zu erhalten, wobei jeder der Punkte einen Oberflächenpunkt auf einer Außenfläche der Wärmetauschvorrichtung darstellt,
2. b) nach dem Erhalten der Punktwolke die Punktwolke hinsichtlich Strukturen zu durchsuchen, die Rohren mit einem vordefinierten Außendurchmesser entsprechen. Solche Rohre können fluidführenden Elementen der Wärmetauschvorrichtung entsprechen, in denen Lecks gesucht werden müssen,
3. c) in den gemäß b) erhaltenen Strukturen mindestens einen interessierenden Bereich zu durchsuchen, in dem sich der Durchmesser oder die Richtung des Rohrs ändert oder in dem ein Rohr endet, wie z.B. durch Vergrößerung des Durchmessers entsprechend einem Schweiß- oder Lötpunkt oder einer Schweiß- oder Lötstelle, einer Fügestelle oder einem Übergang zu einem weiteren Rohr, einem Verbindungsbereich, in dem das Rohr mit einem weiteren Rohr verbunden ist, wie z.B. durch Schweißen oder Löten, oder einem Ende eines Rohrs. Eine Richtungsänderung des Rohrs kann eine Biegung des Rohrs sein, an der sich die Richtung der Hauptlängsachse (Mittelachse) des Rohrs ändert. Eine Richtungsänderung des Rohrs kann auch eine Biegung in einer Außenwand des Rohrs sein. Diese interessierenden Bereiche stellen Schwachpunkte der durchsuchten fluidführenden Elemente dar und sind daher von besonderer Relevanz für die Schnüffel-Leckdetektion bei einer Qualitätsprüfung bei einem automatisierten Herstellungsprozesses einer Wärmetauschvorrichtung.
4. d) Sobald ein interessierender Bereich gefunden worden ist, wird mit der erfindungsgemäßen Vorrichtung ein Heranführweg zum Heranführen der Schnüffelsonde eines Gasleckdetektors eines Gasleckdetektionssystem an den interessierenden Bereich innerhalb der Punktwolke bestimmt. Dies kann typischerweise durch Berechnen von mehreren Heranführwegen innerhalb der Punktwolke im virtuellen Raum durchgeführt werden, bevor die physische Schnüffelsonde tatsächlich an die Wärmetauschvorrichtung herangeführt wird.
5. e) Sobald ein Heranführweg bestimmt worden ist, wird die Schnüffelsonde physisch manuell entlang des Heranführwegs an einen Prüfbereich der Wärmetauschvorrichtung herangeführt. Der Prüfbereich auf der physischen Wärmetauschvorrichtung entspricht dem zuvor ermittelten interessierenden Bereich innerhalb der Punktwolke.

Accordingly, the device is designed to

1. a) obtain a cloud of points in a virtual 3-dimensional space from the heat exchange device using a 3D sensor, each of the points representing a surface point on an outer surface of the heat exchange device,
2. b) after obtaining the point cloud, to search the point cloud for structures, correspond to tubes with a predefined outside diameter. Such tubes can correspond to fluid-carrying elements of the heat exchange device in which leaks must be searched,
3. c) to search in the structures obtained according to b) at least one region of interest where the diameter or the direction of the tube changes or where a tube ends, such as by increasing the diameter corresponding to a weld or braze point or a weld or a braze, a joint or transition to another pipe, a joint area where the pipe is joined to another pipe, such as by welding or brazing, or an end of a pipe. A change in direction of the pipe can be a bend in the pipe at which the direction of the main longitudinal axis (central axis) of the pipe changes. A change in direction of the tube can also be a bend in an outer wall of the tube. These areas of interest represent weak points of the fluid-carrying elements being searched and are therefore of particular relevance for sniffing leak detection during a quality check in an automated manufacturing process of a heat exchange device.
4. d) As soon as an area of interest has been found, a approach path for approaching the sniffer probe of a gas leak detector of a gas leak detection system to the area of interest within the point cloud is determined with the device according to the invention. This can typically be done by computing multiple approaches within the cloud of points in virtual space before actually approaching the physical sniffer probe to the heat exchange device.
5. e) Once an approach path has been determined, the sniffer probe is physically manually advanced along the approach path to a test area of the heat exchange device. The area of interest on the physical heat exchange device corresponds to the previously determined area of interest within the point cloud.

In other words, the invention provides obtaining a virtual model or a simulation of at least part of the heat exchange device using a 3D sensor, the virtual model or the simulation in terms of possible leakage zones (test areas on the physical heat exchange device), the respective areas of interest of the virtual match the model is searched. Before the sniffer probe is actually physically approached to such a test area, the invention provides for determining a usable approach path using the virtual model instead of the physical heat exchange device to physically approach the sniffer probe to a test area only when a approach path to the respective area of interest of the virtual model has been found.

The invention thus provides more reliable, automated and faster sniffing leak detection on fluid-carrying elements of heat exchange devices. The fluid-carrying elements are often small and hidden within or below the outer peripheral surface of the heat exchange device. In particular, different types of heat exchange devices have different installation locations for their fluid-carrying structures to be tested. The invention therefore enables automatic searching of different types of heat exchange devices in a reliable and fast way.

The device is a leak detection system comprising the gas leak detector and preferably a robot.

The point cloud in the 3-dimensional virtual space is preferably generated from image data obtained from an optical camera, preferably at least two cameras of an imaging system. The 3D sensor can be an imaging system with at least one optical camera and at least one lighting device, such as an LED or a laser source.

Following step a), the point cloud can be compared with digital reference values of the structures of the heat exchange device to be searched for in the point cloud. This may be done to identify and/or locate structures such as a frame or other component of the heat exchange device such as a compressor. The digital reference data is preferably previously obtained CAD data of the heat exchange device. The digital reference data can be stored in a memory of the leak detection system according to the invention.

In one embodiment, at least one search region within the cloud of points may be selected or obtained based on comparing the cloud of points to the digital reference data. The search area can be determined using position data of the position of the heat exchange device within the point cloud, which position data can be obtained by step b). For example, once the Structures corresponding to a tube with a predefined outer diameter have been obtained by step b), the position of such structures are detected and stored. This positional data can be used to select the search area in which to search the identified structures or pipes for diameter changes, thereby obtaining the area of interest in which to perform leak detection.

The reference data can be generated by the 3D sensor of the leak detection system from the same heat exchange device or from a corresponding device of the same type.

Step c) can be performed by tracing and analyzing those points within the point cloud that correspond to the pipe found in step b).

In step d) an ideal position of the sniffer probe for gas leak detection on the pipe or an inspection area can be calculated.

Step d) may include determining whether a determined approach path will result in a collision of the sniffer probe with structures of the heat exchange device, and step d) includes determining a further approach path if a collision is expected at a previously determined approach path.

Step d) may be repeated until an approach path is determined in which no collision of the sniffer probe with structures of the heat exchange device is expected. Step d) can additionally or alternatively include the use of previously obtained and stored digital data, such as CAD data, of the sniffer probe and/or a robot performing step e). In particular, at least step e) can be carried out by a robot, which can be part of the leak detection system.

At least one of steps a) - d) can be performed by a software algorithm of a leak detection system comprising a leak detector and preferably the robot mentioned above.

Step d) can include generating a trajectory within or through the point cloud in the virtual space, wherein a robot carrying the sniffer probe is intended to follow the trajectory when performing the actual leak detection.

At least steps b) - d) can be repeated for a plurality of regions of interest, and step e) can then be performed a respective number of times in order to subsequently introduce the sniffer probe to respective test regions corresponding to the regions of interest.

Subsequent to step e), step f) can be carried out with the leak detection system according to the invention, in which the sniffer probe sniffs in the test region in order to carry out a leak detection within the test area on the pipe in order to identify a possible leak in the fluid-conducting structure.

The sniffer probe may have a generally U-shaped sniffer tip with two distally extending sniffer arms, at least one of the sniffer arms having an inlet port. Such a U-shaped sniffer tip is brought up to the inspection area such that the two sniffer tip arms are positioned on opposite sides of the pipe to be inspected.

The sniffer probe or a sniffer tip of the sniffer probe can be automatically reconfigured, transformed or exchanged for another sniffer probe or another sniffer tip once it is determined in step d) that an approach path leads to a collision of the sniffer probe with a structure of the heat exchange device.

The device according to the invention can be applied to a new type of heat exchange device in that information about the location of at least one region of interest and/about the location at which the diameter or the direction of at least one (further) tube changes, about the inside of a region of interest Area to be searched direction and / or to be searched for in step b) predefined outside diameter are provided.

• 1 eine schematische Darstellung eines Leckdetektionssystems und einer Wärmetauschvorrichtung,
• 2 eine schematische Darstellung der Punktwolke im virtuellen Raum, die aus der Wärmetauschvorrichtung von 1 erfasst wird,
• 3 eine schematische Darstellung eines Details einer weiteren Wärmetauschvorrichtung, und
• 4 eine schematische Darstellung der Punktwolke im virtuellen Raum, die aus der Wärmetauschvorrichtung von 3 erfasst wird.

In the following, embodiments of the invention are described in more detail with reference to the drawings. Show it:

• 1 a schematic representation of a leak detection system and a heat exchange device,
• 2 a schematic representation of the point cloud in virtual space resulting from the heat exchange device of 1 is recorded,
• 3 a schematic representation of a detail of another heat exchange device, and
• 4 a schematic representation of the point cloud in virtual space resulting from the heat exchange device of 3 is detected.

1 12 shows a heat exchange device 12 in the form of a refrigerator. The term “heat exchange device” as used in the present disclosure refers to systems or devices that include a heat exchanger, such as refrigerators, air conditioners, heat pumps, etc. On its lower rear side 14, the heat exchange device has a plurality of fluid-carrying elements 16, 18 in the form of tubes, which are welded onto the rear side of the refrigerator during the manufacturing process. As part of a fully automated quality control, particular inspection areas 20 for performing leak detection in the inspection areas 20 must be identified. A test area 20 is considered to be an area of the heat exchange device where tubes are assembled, welded or brazed together, where a tube terminates, where one tube is connected to another tube, or where tubes are joined or cross each other. At the in 1 In the embodiment shown, a first fluid-carrying element 16 is arranged vertically and a second fluid-carrying element 18 is connected to one of its ends with the first fluid-carrying element 16 . The area where the pipes 16, 18 are connected is considered the test area 20 and is in 1 shown as a dashed circle.

An even more typical example is in 3 and 4 shown, in which two tubes 16, 18 with different diameters are connected to each other along a common longitudinal axis 17.

The object of the invention is to automatically move a sniffer probe 22 of a sniffer leak detector 24 to the inspection area 20 so that the sniffer tip 25 of the sniffer probe 22 is positioned close enough to aspirate gas escaping from a possible leak in one of the pipes 16, 18 within the Test area 20 outlet. The sniffer probe 22 is connected to the gas leak detector 24 by a connecting tube 26 in a conventional manner.

The sniffer probe 22 is mounted on the distal end 28 of a robotic arm 30 of a robot 32 .

A 3D sensor 34 in the form of an imaging system 36 that includes two optical cameras 38, 40 and an illumination device 42 in the form of an LED light captures digital image data of the lower rear surface 14 of the heat exchange device 12. The illumination device 42 illuminates in a well-known manner the heat exchange device 12 and in particular the lower rear side 14 of the heat exchange device 12. The cameras 38, 40 capture the reflected light and the imaging system 36 generates digital image data from which a cloud of points 44 in a 3-dimensional virtual space 48 is captured.

2 and 4 12 show simplified reduced graphical representations of the acquired point cloud 44, shown reduced to a 2-dimensional matrix for illustrative purposes only. In fact, the point cloud 44 captured by the 3D sensor 34 is 3-dimensional, such as in the form of a 3-dimensional grid or network. In other words, each point 46 of the point cloud 44 has three coordinates x, y, z and an amplitude value that represents, for example, the intensity of the reflected illumination recorded by the cameras 38, 40.

According to the invention, the point cloud 44 is searched for structures that correspond to pipes with a predefined outside diameter. For example, the amplitude values of the points 46 can be searched for values within a specific range and within specific distances with respect to the geometric structure of a tube with a predefined outside diameter corresponding to the diameter of the tubes 16,18.

In 2 and 4 For example, the points of cloud 44 corresponding to tubes 16, 18 are indicated by reference numeral 46a and are represented by filled circles, while other points 46 are represented by open circles. Lines 50 connect the points 46a and thereby make the structures or representations 15, 19 of the tubes 16, 18 of the heat exchange device 12 in the virtual space 48 visible.

The term "virtual space" generally refers to a simulated environment of the heat exchange device 12, the robot 32, the robotic arm 30 and the sniffer probe 22 and the space between the probe 22 and the heat exchange device 12.

As a next step, the structure or points 46 obtained are searched for changes in diameter using the device according to the invention. For example, if the points 46a or the lines 50 corresponding to the left horizontal tube 18 change to 2 followed from left to right, is the diameter of texture representation 19 of tube 18 within virtual space 48 when texture representation 19 of tube 18 meets texture representation 15 of vertical tube 16 and connected to it. For example, this can be determined by analyzing the distances between pairs of points 46a and comparing the distances to the respective distances of other points 46a along line 50. The dots 46a of the texture map 15 of the vertical tube 16 appear to increase in diameter on the texture map 19 of the tube 18 when analyzed from left to right.

Likewise, when analyzing the structural representation 15 of the vertical tube 16 from top to bottom, distances between pairs of points 46a in that region where the structural representation 15 of the vertical tube 16 meets the structural representation 19 of the horizontal tube 18 increase, resulting in an increase of the diameter of the tube 16 appears to be.

The area where such an increase in diameter is noted is indicated by the dashed line in 2 and 4 marked as region of interest 52 . This region of interest 52 is stored in a leak detection system 56 memory residing within the robot 32 and/or within the 3D sensor 36, or alternatively within a separate computing device connected to the robot 32 and/or the 3D sensor 36. can be provided. The leak detection device 56 has the leak detector 24 , the robot 32 and the 3D sensor 34 .

The area of interest 52 in the virtual space 48 corresponds to the test area 20 of the heat exchange device 12, with the sniffer probe 22 having to be brought up to the test area 12 for leak detection.

As a next step, a delivery path 58 for delivering the sniffer probe to the inspection area 20 and delivering a graphical representation of the sniffer probe 22 in the point cloud 44 to the area of interest 52 must be determined. This is done by using CAD data of the sniffer probe 22 and its sniffer tip 25 and comparing a point cloud 44 to the CAD data. In this way, the points 46b within the point cloud 44 which correspond to the sniffer tip 25 or the sniffer probe 22 can be identified. Thereafter, an approach path 58 for approaching the sniffer tip 25 to the inspection area 20 or the area of interest 52 within the virtual space 48 is calculated. Therefore, an approach path 58 must be determined to avoid collision of the sniffer tip 25, the sniffer probe 22 and/or the robot arm 30 or the connecting tube 26 with the heat exchange device 12 or other structures or components thereof. This approach path 58 is indicated by the four arrows and by the points 46c in 2 displayed.

Only after determining an approach path 58 on which no collision occurs within the virtual space 48 or the simulated environment is the sniffer tip 25 actually introduced by the robot 32 and the robotic arm 30 to the real inspection area 20 in the real world.

As a result, leak detection in the manufacturing industry and in quality control can be performed fully automatically, much faster and much more reliably compared to the conventional sniffing leak detection performed by human operators on heat exchange devices.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102005022156 A1 [0002]
• US4945305 [0004]
• WO 2009/016160 A1 [0005]

Claims (21)

Leak detection system with a gas leak detector (24), a sniffer probe (22) and a 3D sensor (34), for detecting a leak in a fluid-carrying element (16, 18) of a heat exchange device (12), the leak detection system being designed to do the following Steps to perform: a) generating a point cloud (44) of the heat exchange device (12) in a three-dimensional virtual space (48) using a 3D sensor (34), each of the points representing a surface point (46a) on the outer surface of the heat exchange device (12), b) searching within the point cloud (44) for structures (50) that correspond to tubes with a predefined outside diameter, c) searching the obtained structures (50) for a region of interest (52) in which the diameter or the direction of the tube changes, d) once an area of interest (52) is found, determining an approach path (58) for approaching a sniffer probe (22) of a gas leak detector (24) to the area of interest (52) within the point cloud (44), and e) automatically physically approaching the sniffer probe (22) to a test area (20) of the heat exchange device (12) along the approach path (58), the test area (20) corresponding to the area of interest (52) within the point cloud (44). leak detection system claim 1 , wherein the leak detection system is designed to perform steps a) - e) automatically. leak detection system claim 1 or 2 , with an imaging system (36) having at least two optical cameras (38, 40), wherein the point cloud (44) is generated in the three-dimensional virtual space (48) from image data obtained from the at least two optical cameras (38, 40) of the Imaging system (36) are obtained. Leak detection system according to one of the preceding claims, in which the 3D sensor (34) is an imaging system (36) with at least one optical camera and at least one lighting device (42). Leak detection system according to one of the preceding claims, in which, following step a), the point cloud (44) is compared with digital reference data of the structures of the heat exchange device (12) to be searched for within the point cloud (44). leak detection system claim 5 , wherein the digital reference data are previously obtained CAD data of the heat exchange device (12). leak detection system claim 5 or 6 , in which at least one search area within the point cloud (44) is selected on the basis of the comparison with the reference data. A leak detection system according to any one of the preceding claims, wherein selecting the search area is performed using position data of the position of the heat exchange device (12) within the point cloud (44) obtained by step b). Leak detection system according to one of Claims 5 - 8th , in which the reference data from the 3D sensor (34) are generated from the same heat exchange device (12) or from a corresponding heat exchange device (12) of the same type. A leak detection system as claimed in any preceding claim, wherein step c) is performed by tracing and analyzing those points (46a) within the point cloud (44) which correspond to the pipe found in step b). A leak detection system according to any one of the preceding claims, wherein in step d) an ideal position of the sniffer probe (22) for gas leak detection at the pipe or test area (20) is calculated. A leak detection system according to any one of the preceding claims, wherein step d) includes determining whether a given approach path (58) will result in collision of the sniffer probe (22) with structures of the heat exchange device (12), and determining a further approach path (58) when a collision is expected at a predetermined approach path (58). A leak detection system according to any one of the preceding claims, wherein step d) is repeated until an approach path (58) is determined at which collision of the sniffer probe (22) with structures of the heat exchange device (12) is not expected. A leak detection system according to any one of the preceding claims, wherein step d) comprises using previously obtained and stored digital data, such as CAD data, of the sniffer probe (22) and/or a robot (32) performing step e). Leak detection system according to one of the preceding claims, in which at least step e) is carried out by a robot. A leak detection system as claimed in any preceding claim, wherein at least one of steps a) - d) is performed by a software algorithm of the leak detection system (56) comprising the leak detector and a robot (32). A leak detection system as claimed in any preceding claim, wherein step d) comprises generating a trajectory (46c) followed by a robot (32) carrying the sniffer probe (22). A leak detection system as claimed in any one of the preceding claims, wherein at least steps b) - d) are repeated for a plurality of regions of interest and step e) is then performed a respective number of times to subsequently place the sniffer probe (22) on respective test areas corresponding to the regions of interest correspond to bring. Leak detection system according to one of the preceding claims, wherein the leak detection system is adapted to carry out the following step after step e): f) sniffing the test region with the sniffer probe (22) to perform leak detection on the pipe within the test area (20) to identify a possible leak in the fluid-carrying structure (16, 18). A leak detection system as claimed in any preceding claim, wherein the sniffer probe (22) has a generally U-shaped sniffer tip with two distally extending sniffer arms. Leak detection system according to any of the preceding claims, wherein the sniffer probe (22) or a sniffer tip (25) of the sniffer probe (22) is automatically reconfigured, transformed or exchanged for another sniffer probe (22) or another sniffer tip (25) as soon as in step d) it is determined that a feed path (58) leads to a collision of the sniffer probe (22) with structures of the heat exchange device (12).

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