Multi-row type heat exchange tube eddy current detection device for laser calibration and use method of multi-row type heat exchange tube eddy current detection device

Abstract

The invention provides a multi-row heat exchange tube eddy current detection device for laser calibration and a use method, and aims to improve the detection efficiency and reduce the dependence on the experience of an operator. The device design has six degrees of freedom, the operability is enhanced, and a plurality of supports are installed on the inner frame sliding table, so that simultaneous work of a plurality of eddy current detection devices is realized. During detection, the wheel disc motor enables the wheel disc to rotate to drive the probe to advance, and the probe automatically enters the heat exchange tube for detection. According to the device, the lead screws on all the frames are moved, so that laser spots on the supports are accurately aligned with the heat exchange tubes, and complex manual adjustment is not needed. The distance between the supports is equal to the distance between the heat exchange tubes, and detection consistency is ensured. After one row of detection is completed, the position of the support is adjusted, the next row of heat exchange tubes are rapidly calibrated, and efficient detection of the whole heat exchanger is achieved. The device significantly improves the detection speed and accuracy, reduces the labor cost, and is especially suitable for the automatic detection task of a large-scale heat exchange tube.

Description

Technical Field

[0001] The present invention belongs to the technical field of detection devices, and more specifically, relates to a laser-calibrated multi-row heat exchange tube eddy current detection device and a method for using the same. Background Art

[0002] During the long-term operation of the heat exchanger, the heat exchange tubes are prone to corrosion, damage, and thinning of the heat exchange tube wall due to the influence of the gas or the alternation of hot and cold in the heat exchanger. If such problems are not discovered in time during long-term use, the efficiency of the heat exchanger will be reduced, or the gas in the tube will leak, causing great economic losses and safety hazards.

[0003] Due to the special structure of the heat exchange tube, the traditional method is to use the internal penetration eddy current detection method to detect the defects of the heat exchange tube. This requires manual insertion of the detection probe and the probe wire into the heat exchange tube. That is, after the probe is placed in the heat exchange tube, the probe is manually pushed to the other end of the heat exchange tube using the probe wire connected to the probe, and then the probe is pulled out using the probe wire. Manually passing the probe through the heat exchange tube is not only time-consuming and laborious, but the accuracy of the operation will also decrease with time or the fatigue of the worker, because the detection probe needs to maintain a certain speed during the insertion process, which cannot be too fast or too slow, and manual operation of these operations is unavoidable. In addition, a heat exchanger normally has hundreds of heat exchange tubes, which requires a large number of workers and equipment, and the efficiency of the entire detection is extremely low. Summary of the invention

[0004] The purpose of the present invention is to provide a laser-calibrated multi-row heat exchange tube eddy current detection device and a method of using the same, which has a reasonable structural design, is easy to operate, is independent of the operator's experience and skill level, can reduce manpower and effectively improve work efficiency.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: A laser-calibrated multi-row heat exchange tube eddy current detection device, characterized in that: it includes an inner frame slide, the inner frame slide is placed on a motion device with six degrees of freedom, two symmetrical fixed shafts are vertically installed in the inner frame slide, a plurality of brackets are installed on the fixed shafts, each bracket is installed with a tube and a laser transmitter, the bracket is used as a carrier and a bracket fixing device, a laser calibration device and a probe line pushing device are installed on it, and the probe line pushing device is located between the bracket fixing device and the laser calibration device; The bracket fixing device includes a pair of positioning bolts, a pair of bracket fixing fixtures, and a pair of fastening screws. The fastening screws are used to install the bracket fixing fixture so that the bracket can slide on the fixed shaft. The tube is placed on the bracket fixing fixture. Threaded holes are provided on both sides of the bracket to abut against the fixed shaft. The positioning bolts can be used to lock and position the bracket on the fixed shaft through the threaded holes. The tail of the bracket has a space for placing and fixing the laser emitter, and the laser calibration device includes a laser emitter and a pair of positioning pins, and the positioning pins are located above the tail of the bracket and clamped on both sides of the laser emitter for fixing; The probe line pushing device includes a pair of wheel motors, a pair of wheels and a pair of wire passing holes. The wheels are symmetrically arranged circular rotating wheels, and wheel motors are installed on the upper sides of the wheels. The wheel motors control the wheels to rotate towards or away from each other. Two vertical plates are installed in front and behind the wheels, and the wire passing holes are respectively located at the center of the two vertical plates. The probe line passes through the wire passing holes and is clamped by a pair of wheels, and the rotation of the wheels is controlled by the wheel motor to drive the extension and retraction of the probe line.

[0006] As a further preferred solution, the rays emitted by the laser emitter pass through the wire hole and the tube.

[0007] As a further preferred solution, the motion device with six degrees of freedom includes a base, a pair of base screws, a pair of motors 1, an outer frame, a pair of outer frame screws, a pair of motors 2, an inner frame, a pair of inner frame screws, a motor 3, a rotating shaft, a pair of shaft gears, and a pair of screw gears; The top of the base is provided with a groove, and horizontal base screws are installed on both sides of the groove, and the base screws are controlled by corresponding motor 1. The two sides of the bottom end of the outer frame are rotatably connected with the base screws, and the outer frame is a vertical structure. The upper and lower parts of the outer frame are rotatably connected with horizontal outer frame screws, and the outer frame screws are controlled by corresponding motor 2. The upper and lower parts of the inner frame are rotatably connected with the outer frame screws, and the two sides of the bottom of the inner frame are rotatably connected with vertical inner frame screws, and a screw gear is installed on the top of the inner frame screw, and a rotating shaft is horizontally installed on the upper top of the inner frame, and the rotating shaft is controlled by motor 3 installed on the side of the inner frame, and gears on the shaft are fixedly connected to the gears on the shaft, and the gears on the shaft are meshed with the screw gear to drive the inner frame screw to rotate. The inner frame slide is a vertical structure, and the two sides of the inner frame slide frame are rotatably connected with the inner frame screw.

[0008] As a further preferred solution, the internal vertical length of the inner frame slide is 160 mm, which is suitable for testing heat exchangers with various heat exchange tube spacings.

[0009] As a further preferred solution, the outer diameter of the tube is 10 mm to facilitate the insertion and retraction of the probe wire and the probe.

[0010] As a further preferred solution, a method for using a laser-calibrated multi-row heat exchange tube eddy current detection device is characterized by comprising the following steps: S1, first start the motor to move the outer frame close to the heat exchange tube to be tested; S2, through the rays emitted by the laser transmitter, start the second motor to move the inner frame to achieve the preliminary alignment of the tube and the heat exchange tube to be inspected. When the rays pass through the wire hole and the tube and hit the tube plate of the heat exchanger to be inspected, start the second motor to move the inner frame to achieve vertical alignment of the tube and the heat exchange tube. Start the third motor to drive the rotating shaft. The gear on the rotating shaft drives the lead screw gear to rotate, and the inner frame lead screw also rotates accordingly, so that the inner frame slide slides to the appropriate position. Use the positioning bolts to adjust the position of the bracket so that the tube and the heat exchange tube are horizontally aligned. The rays are immersed in the first heat exchange tube to be inspected, and the positioning of the first tube and the first heat exchange tube is completed; S3. Adjust the positions of several subsequent brackets by means of positioning bolts so that each tube is calibrated and positioned with the heat exchange tubes in the same row; S4. After positioning is completed, put the eddy current probe into the tube, pass the probe wire through the wire hole at the rear of the wheel and put it between the two wheels, start the wheel motor, and the rotation of the wheel continuously squeezes the probe wire in the middle, so that the probe wire passes through the wire hole in front of the wheel and connects with the probe. Under the squeezing action of the wheel, the probe wire and the probe continuously extend into the heat exchange tube. When the probe protrudes from the other end of the heat exchange tube, stop the wheel motor to complete the detection; S5. After the detection is completed, the wheel motor is started again to pull back the probe and the probe wire, and the probe and the probe wire on the uppermost bracket of the inner frame slide are removed. Since the spacing between the heat exchange tubes on a normal heat exchanger is the same, after calibrating the positions of the corresponding heat exchange tubes, when the heat exchange tubes in the same column are detected again, step S2 is repeated to realize the positioning of the tube on the uppermost bracket and the uppermost heat exchange tube to be measured. The lower heat exchange tubes do not need to be calibrated again, and only step S4 needs to be repeated to detect the heat exchange tubes. Beneficial Effects

[0011] The present invention has the following beneficial effects: This device enables the eddy current detection device to have six degrees of freedom. Compared with the traditional detection device, it is more operable. Several brackets are installed on the slide, which can be used for multiple eddy current detection devices to work simultaneously. When working, you only need to open the two small motors behind the bracket. The motor drives the wheel to rotate to push the probe line forward continuously, so that the probe in the tube enters the heat exchange tube to be detected and continues to extend forward. There is also a laser calibration device behind the bracket. Before work, turn on the laser calibration device and move the screw on the base and the frame to make the light spot on the uppermost bracket sink into the first heat exchange tube to be detected. The other three brackets are fixed with bolts on both sides. The bracket can be moved up and down by rotating the screws. Only one worker is needed to operate it, and it no longer depends on the worker's operating experience and technical level.

[0012] Since the spacing between heat exchange tubes on a normal heat exchanger is the same, after calibrating the position of the corresponding heat exchange tube, there is no need to move the brackets of other heat exchange tubes on the heat exchanger. After the heat exchange tube to be tested is tested, it is only necessary to use the laser transmitter to calibrate the tube on the uppermost bracket with the uppermost heat exchange tube to be tested. This method can easily detect the entire device. It has a reasonable structural design and is easy to operate. It can reduce manpower and effectively improve work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a front view of the device of the present invention; Figure 2 It is the front view of the inner frame of the present invention; Figure 3 is an overall diagram of the stent of the present invention; Figure 4 is a front view of the bracket of the present invention; Figure 5 It is a schematic diagram of the position of the positioning bolts on the bracket of the present invention; Figure 6 It is a schematic diagram of the structure of the probe line pushing device and the laser calibration device of the present invention; Figure 7 It is a schematic diagram of the positioning of the laser transmitter and the positioning pin of the present invention.

[0014] The components include: 1. Base; 2. Base screw; 3. Motor 1; 4. Outer frame; 5. Outer frame screw; 6. Motor 2; 7. Inner frame; 8. Inner frame screw; 9. Motor 3; 10. Rotating shaft; 11. Gear on shaft; 12. Screw gear; 13. Inner frame slide; 14. Bracket; 141. Positioning bolt; 142. Bracket fixing fixture; 143. Fastening screw; 144. Positioning pin; 145. Wheel motor; 146. Wheel; 147. Wire hole; 15. Tube; 16. Laser transmitter. DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] In the description of the present invention, it should be understood that the terms "left side", "right side", "upper part", "lower part" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. "First", "second" and the like do not indicate the importance of the components, and therefore cannot be understood as limiting the present invention. The specific dimensions used in this embodiment are only for illustrating the technical solution, and do not limit the scope of protection of the present invention.

[0017] like Figure 1 and 2 As shown, the inner frame slide 13 is placed on a motion device with six degrees of freedom, which includes a base 1, a pair of base screws 2, a pair of motors 1 3, an outer frame 4, a pair of outer frame screws 5, a pair of motors 2 6, an inner frame 7, a pair of inner frame screws 8, a motor 3 9, a rotating shaft 10, a pair of shaft gears 11, and a pair of screw gears 12. A groove is provided on the top of the base 1, and horizontal base screws 2 are installed on both sides of the groove. The base screw 2 is controlled by the corresponding motor 1 3. The two sides of the bottom end of the outer frame 4 are rotatably connected with the base screw 2. The outer frame 4 is a vertical structure, and the upper and lower parts of the outer frame 4 are rotatably connected with the horizontal outer The frame lead screw 5 and the outer frame lead screw 5 are controlled by the corresponding motor 2 6. The upper and lower parts of the inner frame 7 are rotatably connected with the outer frame lead screw 5. The inner frame 7 is rotatably connected with vertical inner frame lead screws 8 on both sides of the bottom of the frame. A lead screw gear 12 is installed on the top of the inner frame lead screw 8. A rotating shaft 10 is horizontally installed on the top of the inner frame 7. The rotating shaft 10 is controlled by a motor 3 9 installed on the side of the inner frame 7. The two ends of the rotating shaft 10 are fixedly connected with shaft gears 11. The shaft gears 11 are meshed with the lead screw gear 12 to drive the inner frame lead screw 8 to rotate. The inner frame slide 12 is a vertical structure, and the inner frame slide 12 is rotatably connected with the inner frame lead screw 8 on both sides of the frame. Among them, the two base screws 2 can be rotated by motor 1 3 so that the outer frame 4 can move horizontally, and the two outer frame screws 5 can be rotated by motor 2 6 to realize the vertical movement of the inner frame 7. The rotating shaft 10 on the inner frame 7 can be rotated by motor 3 9, and the shaft gear 11 on the rotating shaft 10 drives the screw gear 12 at the top of the inner frame screw 8, so that the inner frame slide 13 can realize vertical movement.

[0018] like Figure 3-7As shown, four brackets 14 are installed on the inner frame slide 13, and a tube 15 and a laser emitter 16 are fixed on the bracket 14. The laser emitter 16 is an infrared straight line emitter. The bracket 14 includes a bracket fixing device, a laser calibration device and a line detection push device. The bracket fixing device includes a positioning bolt 141, a bracket fixing fixture 142 and a fastening screw 143. The fastening screw 143 is used to install the bracket 14. The tube 15 is placed on the bracket fixing fixture 142. When the upper and lower positions of the tube 15 need to be adjusted, the bracket 14 can be moved up and down by loosening and tightening the positioning bolt 141 to position the tube 15. The laser calibration device includes a laser emitter 16 and a positioning pin 144. The positioning pin 144 is clamped on both sides of the laser emitter 16 from the upper end of the bracket 14 to complete the fixation. The line detection push device includes a wire hole 147, a wheel 146 and a wheel motor 145.

[0019] During use, first install the bracket 14, start the motor 13 to move the outer frame 4 close to the heat exchange tube to be inspected, when the rays emitted by the laser emitter 16 pass through the wire hole 147 and the tube 15 to the heat exchanger tube plate to be inspected, the outer frame lead screw 5 is rotated by the motor 26 to make the inner frame 7 move horizontally, so that the tube 15 is vertically aligned with the heat exchange tube to be inspected, and then start the motor 39 to rotate the rotating shaft 10 to drive the lead screw gear 12 meshing with the gear 11 on the shaft to rotate, so that the inner frame lead screw 8 rotates at the same time, and the inner frame slide 13 moves up and down to a suitable position, and adjust the positioning bolts 141 on both sides of the bracket 14 to immerse the red dot in the first heat exchange tube to be inspected, then the tube 15 on the first bracket 14 is positioned with the first heat exchange tube, and at this time, it is only necessary to adjust the positioning bolts 141 on both sides of the second, third, and fourth brackets 14 to calibrate and position the lower three tubes 15 with the second, third, and fourth heat exchange tubes in the same row respectively. After the four brackets 14 are positioned, the probe is inserted into the tube 15, the probe wire passes through the wire hole 147 at the rear end of the wheel 146 and is stuck in the middle of the wheel, the wheel motor 145 on the wheel 146 is started to squeeze the probe wire in the middle through the rotation of the wheel 146 so that the probe wire is sent forward through the wire hole 147 at the front end of the wheel 146. After the probe is connected with the probe wire, the wheel motor 145 is started again so that the probe wire and the probe continue to move forward into the interior of the heat exchange tube. When the probe protrudes from the other end of the heat exchange tube, the wheel motor 145 is stopped, and the detection is completed at this time. When it is necessary to measure other heat exchange tubes, the roulette motor 145 is reversed so that the device can pull back the probe wire, and the probe and probe wire on the first bracket 14 are removed, the laser emitter 16 behind it is turned on, and the motor three 9 is turned on to slowly move the inner frame slide 13 downward through the rotating shaft 10. When the laser red dot is immersed in the fifth heat exchange tube, the following three heat exchange tubes do not need to be positioned, and the calibration is also completed. Because the spacing between the heat exchange tubes is the same, it is only necessary to position the first heat exchange tube and the fifth heat exchange tube, and then install the probe and probe wire of the first bracket 14, and repeat the above operation.

[0020] This device can greatly reduce the use of manpower, is simple and convenient to operate, is not limited by the operator's operating experience and level, and greatly stabilizes the accuracy of the detection. The vertical length of the inner frame of the inner frame slide 13 is 160mm, and the outer diameter of the tube 15 is only 10mm, which is suitable for heat exchangers with various heat exchange tube spacings. Because when the heat exchange tube spacing is large, two or three devices can be used for measurement at the same time. Consider the number of installation brackets 14 based on the heat exchange tube spacing. The installation of the bracket 14 is very convenient and easy to disassemble and assemble. Moreover, after positioning a group of heat exchange tubes, there is no need to adjust the position of the bracket 14 on the inner frame slide 13. You only need to adjust the position of the inner frame slide 13 vertically to position the tube 15 on the first bracket 14 with the first heat exchange tube of each group. The process of extending and pulling out the probe line on the bracket 14 replaces the traditional manual operation, reduces the consumption of manpower and material resources, and is easy to operate and more accurate in detection. After the measurement of one row of heat exchange tubes is completed, start the motor 2 6 to rotate the outer frame screw 5 to move the inner frame 7 horizontally, so that the tube 15 on the first bracket 14 is positioned with the first heat exchange tube of another row, and then measure the other row of heat exchange tubes in the same way.

[0021] The preferred embodiments of the present invention are described in detail above; however, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all belong to the protection scope of the present invention.

Claims

1. A laser-calibrated eddy current detection device for multi-row heat exchange tubes, characterized in that: The invention comprises an inner frame slide (13), wherein the inner frame slide (13) is placed on a motion device having six degrees of freedom, wherein two symmetrical fixed shafts are vertically installed in the frame of the inner frame slide (13), wherein a plurality of brackets (14) are installed on the fixed shafts, wherein each bracket (14) is installed with a tube (15) and a laser transmitter (16), wherein the bracket (14) is used as a carrier and a bracket fixing device, a laser calibration device and a probe line pushing device are installed on the bracket (14), wherein the probe line pushing device is located between the bracket fixing device and the laser calibration device; The bracket fixing device comprises a pair of positioning bolts (141), a pair of bracket fixing fixtures (142), and a pair of fastening screws (143). The fastening screws (143) are used to install the bracket fixing fixture (142), so that the bracket (14) can slide on the fixed shaft. The tube (15) is placed on the bracket fixing fixture (142). The bracket (14) is provided with threaded holes on both sides to abut against the fixed shaft. The positioning bolts (141) can realize the locking and positioning of the bracket (14) on the fixed shaft through the threaded holes. The rear portion of the bracket (14) has a space for placing and fixing a laser emitter (16), and the laser calibration device comprises a laser emitter (16) and a pair of positioning pins (144), wherein the positioning pins (144) are located above the rear portion of the bracket (15) and are clamped on both sides of the laser emitter (16) for fixing; The detection line pushing device comprises a pair of wheel motors (145), a pair of wheels (146) and a pair of wire passing holes (147). The wheels (146) are circular rotating wheels arranged symmetrically. The wheel motors (145) are installed on the upper sides of the wheels (146). The wheel motors (145) control the wheels (146) to rotate towards or away from each other. Two vertical plates are installed at the front and rear of the wheel (146). The wire passing holes (147) are respectively located at the center positions of the two vertical plates. The detection line passes through the wire passing holes (147) and is clamped by the pair of wheels (146). The rotation of the wheel motor (145) controls the extension and retraction of the detection line.

2. The laser-calibrated eddy current detection device for multi-row heat exchange tubes according to claim 1, characterized in that: The radiation emitted by the laser emitter (16) passes through the wire hole (147) and the tube (15).

3. The laser-calibrated eddy current detection device for multi-row heat exchange tubes according to claim 1, characterized in that: The motion device having six degrees of freedom comprises a base (1), a pair of base lead screws (2), a pair of motor one (3), an outer frame (4), a pair of outer frame lead screws (5), a pair of motor two (6), an inner frame (7), a pair of inner frame lead screws (8), a motor three (9), a rotating shaft (10), a pair of shaft gears (11), and a pair of lead screw gears (12); The top of the base (1) is provided with a groove, and horizontal base screws (2) are installed on both sides of the groove. The base screws (2) are controlled by a corresponding motor 1 (3). The bottom sides of the outer frame (4) are rotatably connected to the base screws (2). The outer frame (4) is a vertical structure. The upper and lower parts of the outer frame (4) are rotatably connected to the horizontal outer frame screws (5). The outer frame screws (5) are controlled by a corresponding motor 2 (6). The upper and lower parts of the inner frame (7) are rotatably connected to the outer frame screws (5). The inner frame (7) is rotatably connected to the bottom sides of the inner frame (7). A vertical inner frame lead screw (8) is connected, a lead screw gear (12) is installed on the top of the inner frame lead screw (8), a rotating shaft (10) is installed horizontally on the top of the inner frame (7), the rotating shaft (10) is controlled by a motor (9) installed on the side of the inner frame (7), and shaft gears (11) are fixedly connected at both ends of the rotating shaft (10), and the shaft gears (11) are meshed with the lead screw gear (12) to drive the inner frame lead screw (8) to rotate, and the inner frame slide (12) is a vertical structure, and the inner frame slide (12) is rotatably connected to the inner frame lead screw (8) on both sides of the frame.

4. The laser-calibrated multi-row heat exchange tube eddy current detection device according to claim 1, characterized in that: The inner vertical length of the inner frame slide (13) is 160 mm, which is suitable for testing heat exchangers with various heat exchange tube spacings.

5. The laser-calibrated eddy current testing device for multi-row heat exchange tubes according to claim 1, characterized in that: The outer diameter of the tube (13) is 10 mm, which is convenient for the insertion and contraction of the probe line and the probe.

6. The method for using the laser-calibrated multi-row heat exchange tube eddy current detection device according to claims 1-5, characterized in that: The following steps are involved: S1, after installing a plurality of brackets (14), start motor 1 (3) to move the outer frame (4) close to the heat exchange tube to be inspected; S2, using the radiation emitted by the laser emitter (16), the motor 2 (6) is started to move the inner frame (7) to achieve preliminary alignment between the tube (15) and the heat exchange tube to be inspected. When the radiation passes through the wire hole (147) and the tube (15) and is emitted onto the tube sheet of the heat exchanger to be inspected, the motor 2 (6) is started again to move the inner frame (7) to achieve vertical alignment between the tube (15) and the heat exchange tube. The motor 3 (9) is started to drive the rotating shaft (10). The gear (11) on the rotating shaft drives the lead screw gear (12) to rotate, and the inner frame lead screw (8) also rotates accordingly, so that the inner frame slide (13) slides to a suitable position. The position of the bracket (14) is adjusted using the positioning bolt (141) so that the tube (15) is horizontally aligned with the heat exchange tube. The radiation is immersed in the first heat exchange tube to be inspected, and the first tube (15) and the first heat exchange tube are positioned. S3, adjusting the positions of the subsequent plurality of brackets (14) by means of positioning bolts (141) so that each tube (15) is calibrated and positioned with respect to the heat exchange tubes in the same row; S4. After the positioning is completed, the eddy current probe is placed in the tube (15), the probe wire passes through the wire hole (147) at the rear of the wheel (146) and is placed between the two wheel discs (146), the wheel disc motor (145) is started, and the rotation of the wheel disc (146) continuously squeezes the probe wire in the middle, so that the probe wire passes through the wire hole (147) in front of the wheel disc (146) and is connected to the probe. Under the squeezing action of the wheel disc (146), the probe wire and the probe continuously extend into the interior of the heat exchange tube. When the probe protrudes from the other end of the heat exchange tube, the wheel disc motor (145) is stopped to complete the detection; S5. After the detection is completed, the wheel motor (145) is started again to pull back the probe and the detection wire, and the probe and the detection wire on the uppermost bracket (14) of the inner frame slide (13) are removed, and step S2 is repeated to achieve the positioning of the first tube (15) and the first heat exchange tube, and step S4 is repeated again to detect the heat exchange tube.

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