JPH08304219A - Device and method for inspecting heat exchanger tube of heat exchanger - Google Patents

Abstract

PURPOSE: To detect very small through holes by acquiring ultrasonic waves generated by the differential pressure of a fluid caused by the leakage of outside air into a heat exchanger tube when the tube is evacuated with an acquisition sensor before the ultrasonic waves are absorbed into the tubesheet of the tube. CONSTITUTION: Since both ends of a heat exchanger tube 14 are plugged up with acquisition sensor-side closing plugs 17 and 18 and the inside of the tube 14 is maintained at a high vacuum by operating a vacuum pump 24, outside air blows in the tube 14 when a leaking section 40 exists. An acquisition sensor 16 provided in the tube 14 measures ultrasonic waves. Since leakage inspections are performed by acquiring the ultrasonic waves, the inspections are hardly affected by low-frequency ambient noise and the sensitivity of the inspections can be set at a high level. Then, the ultrasonic waves are acquired by means of a high-sensitivity ultrasonic-wave detector 28 which can selectively detect ultrasonic waves of a specific frequency and the position, size, etc., of a sound producing or leaking point are quantitatively measured and recorded with a receiver 30 or recorder 32 by converting the ultrasonic waves into an electric current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a heat transfer tube of a heat exchanger for inspecting whether or not a defective portion has occurred in a heat transfer tube used in a heat exchanger for power generation equipment installed in a power plant. In particular, the present invention relates to a heat transfer tube inspection apparatus and method for inspecting steam leakage from a defective portion generated in the heat transfer tube.

[0002]

2. Description of the Related Art Heat exchangers used in thermal power and nuclear power generation facilities are subjected to an eddy current flaw detection test instead of an air pressure or water pressure test as a test for confirming the reliability of a heat transfer tube after the start of operation. There is. Further, as described in JP-A-55-87933, there is a method of feeding gas into the outer pipe of the double pipe and detecting the leak sound of the inner pipe to detect the leak position of the pipe.

[0003]

Among the conventional techniques, the eddy current flaw detection method is sensitive to surface scratches on the heat transfer tube, deformation such as irregularities, inner surface erosion, and foreign matter adhering to the surface. However, it is insensitive to through holes,
Even if you inspect under the condition that detection sensitivity is raised and indication is likely to appear, whether the inspection result is due to deformation such as unevenness,
There is a problem that it is very difficult to determine whether it is due to a through leakage defect or a foreign substance is in contact with the outer surface of the heat transfer tube. Further, in the eddy current flaw inspection method, since the probes are inserted into the heat transfer tubes one by one and scanned, it takes a lot of time for inspection. It is not possible to scan the U-bend portion of the heat transfer tubes with the probes. There is a problem that it is not possible to specify the position such as leakage. Further, the method described in JP-A-55-87933 is a method of enclosing a gas in the outer tube of a double tube and inserting a probe into the inner tube for scanning to detect sound waves and detect leakage. However, the valve for holding the pressure is not installed in the system depending on the arrangement position and role of the heat exchanger, and enclosing gas from the outside is a problem in system operation. or,
When a sound wave is used for defect inspection of the heat transfer tube, there is a concern that the sound wave transmitted to the heat transfer tube is absorbed by the tube plate and attenuated, or ambient background noise is picked up.

As described above, as the defect detecting means after the operation of the heat transfer tube, the conventional eddy current flaw detection test has sufficiently evaluated the dents, surface scratches, corrosion, etc. due to the causes from the outside of the tube. However, it is insensitive to minute through holes, and if the sensitivity is set too high, there is a problem in that even defects not worthy of evaluation are detected as indications, making determination difficult. There is also a restriction on the arrangement position of the heat exchanger in the system and the system operation, and a method capable of detecting minute through holes without using gas or liquid is required.

An object of the present invention is to provide a method for inspecting a heat transfer tube of a heat exchanger which can detect minute through holes without using gas or liquid.

[0006]

In order to achieve the above object, a heat transfer tube inspection apparatus for a heat exchanger according to the present invention inspects a heat transfer tube used in a heat exchanger for the presence of a leak portion. In a heat exchanger heat transfer tube inspection device, a means for sucking air from the tube end of the heat transfer tube, an ultrasonic trapping sensor, and an air leak from a leaking portion detected by the trapping sensor are positioned and sized. It is characterized by having means for specifying.

Further, the suction means has a plurality of capture sensors and a switching header connected to these via a dedicated hose. Further, the trapping sensor is formed at one end of the suction means, and the trapping sensor has a taper-shaped closure plug that is in close contact with the wall of the heat transfer tube.

Further, the inspection method is a heat exchanger heat exchanger tube inspection method for inspecting the presence or absence of a leak portion of the heat exchanger tube used in the heat exchanger, in which air is sucked from the end of the heat exchanger tube, It is characterized in that air leakage from the leaking portion is detected by ultrasonic waves.

Further, in the inspection method of the heat exchanger heat transfer tube for inspecting the presence or absence of a leak portion generated in the heat transfer tube used in the heat exchanger, air is sucked from the tube end portion of the heat transfer tube to cause the leakage portion. It is characterized in that the position of the leaked portion is specified by detecting the air leakage from the at least two places by ultrasonic waves. Further, a plurality of the trapping sensors are arranged so as to be evenly located on the inner circumference of the heat transfer tube. Further, the specifying means is a sound sensor which can selectively detect a specific frequency.

[0010]

With the above-mentioned structure, the inside of the heat transfer tube is evacuated and the ultrasonic waves generated by the fluid pressure difference when the outside air leaks are captured and inspected by the capture sensor before being absorbed by the tube sheet. Therefore, the presence or absence of leakage at the leakage portion can be reliably grasped as compared with the method of utilizing the change in magnetic force due to the eddy current.

Further, since the jet pressure of air from the leaking portion is effectively used and the leak sound is captured by ultrasonic waves, the influence of ambient background noise can be avoided. Also, ultrasonic waves are measured at both ends of the heat transfer tube in the longitudinal direction and in the circumferential direction of the circumferential direction, and proportional difference can be calculated based on the difference between them. It is possible to specify the leak position because the sound pressure detector detects the distribution of the sound pressure, and in the circumferential direction, the sound sensor is scanned in the circumferential direction to find the point where the sound pressure is maximum.

That is, since a trapping sensor is installed in the heat transfer tube, the inside of the heat transfer tube is evacuated to increase the jet pressure of the leak portion to generate ultrasonic waves, and the ultrasonic wave is detected by a highly sensitive ultrasonic sensor. The position and size of holes can be measured quantitatively, and highly reliable measurement can be performed. The leakage position can be easily obtained by measuring the respective sensitivities from both ends of the pipe and measuring the difference in sensitivity. Since leakage inspection is performed by capturing ultrasonic waves, it is possible to perform inspection at a high sensitivity setting because it is not affected by low-frequency noise that is ambient noise.

Further, since the one-touch connector with the switching valve is provided with the easily attachable / detachable multi-axis header, it is not necessary to scan the capturing sensor in the heat transfer tube, and the one-touch connector with the switching valve and the multi-axis header are connected. Therefore, the attachment / detachment operation at the time of switching can be performed quickly, the inspection time can be shortened, and the inspection process can be shortened to 1/3 of the eddy current flaw detection method.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. FIG. 1 is a system diagram of a moisture separator with a heat exchanger, FIG. 2 is a configuration diagram illustrating a leak inspection method of a heat transfer tube, FIG. 3 is a vertical cross-sectional view showing a trap sensor structure, and FIG.
FIG. 10 is a cross-sectional view showing the structure of the capturing sensor, FIG. 10 is a perspective view showing a state in which the multi-axis header is attached, FIGS. 5 and 6 are explanatory views for obtaining the position of the leak portion in the pipe length direction, and FIG. 7 is a through hole. Fig. 8 shows changes in the detection level when the distance is 0 mm.
FIG. 9 is a diagram showing a change in detection level when the through hole is 0.1 mm, and FIG. 9 is a diagram showing a change in detection level when the through hole is 0.3 mm.

The moisture separator with a heater for a nuclear power plant of this embodiment is constructed as shown in FIG. The steam generated in the nuclear reactor 1 passes through the main stop valve 2 and is guided to the high pressure turbine 3. A part of this steam is extracted on the high-pressure side after driving the turbine by the high-pressure turbine 3, flows through the high-pressure extraction pipe 4, flows into the inside of the heat transfer pipe 6 of the heater 6 built in the moisture separator 5, and heats it. It is used as heating steam. After driving the turbine by the high-pressure turbine 3, the remaining steam is extracted on the low-pressure side and guided to the moisture separator 5 through the high-pressure steam exhaust pipe 7. The steam that has flowed into the moisture separator 5 is separated into drain and steam here, and then heat-exchanges with the heated steam in the heater 6, becomes high-energy superheated steam, and is low pressure through the crossaround pipe 8. Air is sent to the turbine 9. The drain separated in the moisture separator 5 passes through the moisture separator drain pipe 10 to the high-pressure feed water heater 11, while the heated steam heat-exchanged in the heater 6 passes through the heater drain pipe 12 and drains. It is guided to the tank 13 and heat is recovered.

The detailed construction of the moisture separator 5 and the heat transfer tube leakage test inspection method will be described with reference to FIG. In the heater 6 built in the moisture separator 5, the heating steam which is the extraction steam from the high-pressure turbine passes through the inside of the heat transfer tube 14, and the high-pressure exhaust steam separated by the moisture separator 5 passes through the outside thereof. Is configured. The heat transfer tube 14 is attached to the tube plate 15 by pipe expansion and welding, and tapered capture sensor side closing plugs 17 and 18 are attached to both ends of the heat transfer tube 14.

At the time of leakage inspection, an ultrasonic wave capturing sensor 16 (hereinafter simply referred to as capturing sensor 16) is inserted into the heat transfer tube 14. The capture sensor 16 is configured as shown in FIGS. That is, as shown in FIGS. 3 and 4, the capture sensor 16 is composed of a large number of sound sensing bars 33 arranged on the inner peripheral side of the heat transfer tube 14, an adjusting nut 34, and a capture sensor side closing plug 17. . The span and contact force between the sound-sensing bar 33 and the heat transfer tube 14 can be adjusted by the adjusting nut 34 so that ultrasonic waves are transmitted to the maximum. As shown in FIG. 2, the rear end side of the capture sensor 16 is connected to a vacuum tank 21 via a pipe 20 having a main valve 19 in the middle, and the lower portion of the vacuum tank 21 is externally connected via a drain valve 26 to the outside. Of the suction device (not shown). This vacuum tank 21 has a vacuum gauge 25 through a valve.
Is connected to the vacuum pump 24 through the main valve 22 and the dehumidifier 23. An ultrasonic sensor 28 is in contact with an intermediate portion of the capture sensor 16, and a receiver 30 is connected to the ultrasonic sensor 28 via a cable 29 and a recorder 32 is connected to the ultrasonic sensor 28 via a cable 31. .

After inserting the capturing sensor 16 into the heat transfer tube 14, the capturing sensor side closing plug 17 and the closing plug 18 are attached.
Installed inside, operate the vacuum pump 24 and heat transfer tube 14
And the inside of the capture sensor 16 is evacuated. Vacuum tank 21
Is a capacity required to maintain a sufficient vacuum degree for a leak inspection even when there is a work of replacing the capture sensor side stop plugs 17 and 18 and a penetration defect shown by 40. The vacuum degree is measured by a vacuum gauge 25. There is. In addition, it is desirable to control the humidity inside the heat transfer tube 14 to be low, and while the dehumidifier 23 is installed to dehumidify,
When the drain is accumulated in the vacuum tank 21, the main valves 19 and 22 are closed, the drain discharge valve 26 is opened, and the drain is discharged by the suction device.

In the inspection method thus constructed, the trapping sensor side closing plug 17 and the closing plug 18 are attached to the pipe end, and the vacuum pump 24 is operated to maintain a high vacuum, so that the leak portion 40 exists. For example, air blows into the heat transfer tube. Since the capture sensor 16 is attached in the heat transfer tube 14, the capture sensor 16 measures ultrasonic waves. The reason for using ultrasonic waves is to capture the leakage sound with ultrasonic waves in order to avoid the influence of ambient background noise.Since ultrasonic waves are used for leak inspection, the influence of low-frequency noise, which is ambient noise, is used. Since it is hard to receive, inspection with high sensitivity setting is possible.

Next, the ultrasonic wave is captured by a high-sensitivity ultrasonic sensor 28 capable of selectively detecting a specific frequency, converted into an electric current, and quantitatively detected by the receiver 30 or the recorder 32 such as the sound or leakage position and size. Record measurement. The position, size, etc. of the leaked portion are measured as follows. As described above, a large number of ultrasonic wave capturing sensors 16 are evenly arranged on the inner circumference of the heat transfer tube, and the leak position is specified by ultrasonic waves at both ends of the heat transfer tube in the longitudinal direction and in the circumferential direction in the circumferential direction. Is measured and proportionally divided by the difference. That is, the leak position in the longitudinal direction of the heat transfer tube is detected by the distribution of the sound pressure from the sound source (sensitivity is measured from both ends of the tube, and the difference is obtained to obtain the sensitivity). Is scanned in the circumferential direction, and the point where the sound pressure is maximized is searched for and detected.

A method of obtaining the leak position in the longitudinal direction of the heat transfer tube will be described more specifically with reference to FIGS. 5 and 6
It is assumed that the leakage portion 40 is present at the position indicated by. At this time,
As shown in FIG. 5, when the capture sensor 16 is arranged at one end of the heat transfer tube and the measurement is performed, the sensing level at the ultrasonic transmission seat 27a is D1, as shown in FIG. 6, at the other end of the heat transfer tube. When the detection level at the ultrasonic wave transmission seat 27b when the capture sensor 16 is arranged and measured is D2, the distance from the leakage portion 40 to the end surface of the tube sheet of the ultrasonic wave transmission seat 27a is L1, the leakage portion. 40 to ultrasonic transmission seat 27b
Let L1 be the distance to the tube sheet end surface of L2 and L be the distance between the tube sheet end surfaces, and L1 and L2 are respectively calculated by L1 = {D1 / (D1 + D2)} L L2 = {D2 / (D1 + D2)} L be able to.

As for the size of the leakage portion 40, the level is measured as shown in FIGS. 7 to 9 showing the measurement results for the diameters of the through holes of 0 mm, 0.1 mm and 0.3 mm, for example. By doing, you can know from its size.

Further, as shown in Table 1, the number of sound-sensing bars 33, that is, the number of sensors, and the degree of vacuum have a relationship in detecting the leaked portion 40, and the number of sensors of 30 to 34 (Table 1) is related. Most suitable.

[0024]

[Table 1]

As described above, according to this embodiment,
A trapping sensor is installed in the heat transfer tube, and the pressure of the leak is increased to generate ultrasonic waves and ultrasonic waves are generated, and the ultrasonic sensor with high sensitivity measures the position and size of the leak holes. The measurement can be performed accurately, and highly reliable measurement can be performed.
Since the scanning of the capture sensor inside the heat transfer tube is not required and the one-touch connector with switching valve and the multi-axis header are connected, the attachment / detachment operation at the time of switching can be performed quickly, and the inspection process is also compared to the eddy current flaw detection test method. , 1/3 can be shortened. Since leakage inspection is performed by capturing ultrasonic waves, it is possible to perform inspection at a high sensitivity setting because it is not affected by low-frequency noise that is ambient noise.

Next, a leakage inspection method using the multi-axis header method will be described with reference to FIGS. As shown in FIG. 10, the multi-axis header system is configured to insert a large number of capture sensors 16 into the heat transfer tubes 14 attached to the tube sheet 15. A one-touch connector 35 with a switching valve and a hose 36 dedicated to a header are connected to each capture sensor 16, and the other end is connected to a multi-axis header 37. In the apparatus thus configured, the main valves 19 and 22 are opened and the vacuum pump 24 is operated. The measurement is performed in the same manner as described above, and if there is a penetration defect, ultrasonic waves are generated by the jet pressure of air, and the ultrasonic sensor 28 can quantitatively capture the position and size of the leaked portion. With this configuration, the one-touch connector with a switching valve allows measurement with a multi-axis header that can be easily attached and detached, and therefore the detector switching operation can be shortened. In addition, the scanning of the capture sensor is not required inside the heat transfer tube, and the one-touch connector with switching valve and the multi-axis header are connected. , 1/3 can be shortened.

[0027]

As described above, the method of inspecting the heat transfer tube of the heat exchanger of the present invention has the following effects.

First, a trapping sensor is installed in the heat transfer tube, and a vacuum is applied to increase the jet pressure at the leaking portion to generate an ultrasonic wave, which is measured by a highly sensitive ultrasonic sensor. Position, size, etc. can be measured quantitatively, and highly reliable measurement can be performed.

Secondly, the scanning of the trapping sensor in the heat transfer tube is not required, and the one-touch connector with a switching valve and the multi-axis header are connected, so that the detaching operation at the time of switching can be performed swiftly, and the inspection process can be swirled. Compared with the current flaw detection test method, it can be shortened to 1/3.

Thirdly, the leakage position can be easily obtained by measuring the respective sensitivities from both ends of the pipe and measuring the sensitivity difference.

Fourthly, since leakage inspection is performed by capturing ultrasonic waves, it is possible to perform inspection with a high sensitivity setting because it is not affected by low-frequency noise that is ambient noise.

[Brief description of drawings]

FIG. 1 is a system diagram of a moisture separator with a heat exchanger.

FIG. 2 is a configuration diagram illustrating a leakage inspection method for a heat transfer tube.

FIG. 3 is a vertical cross-sectional view showing a capture sensor structure.

FIG. 4 is a cross-sectional view showing the structure of the capture sensor viewed from the direction of arrow AA in FIG.

FIG. 5 is an explanatory diagram for obtaining the position of the leaked portion in the pipe length direction.

FIG. 6 is an explanatory diagram for obtaining the position of the leaked portion in the pipe length direction.

FIG. 7 is a diagram showing a change in detection level when a through hole is 0 mm.

FIG. 8 is a diagram showing a change in detection level when a through hole is 0.1 mm.

FIG. 9 is a diagram showing changes in the detection level when the through hole is 0.3 mm.

FIG. 10 is a perspective view showing a multi-axis header attached state.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor, 2 ... Main stop valve, 3 ... High pressure turbine, 4 ... High pressure extraction pipe, 5 ... Moisture separator, 6 ... Heater, 7 ... High pressure steam exhaust pipe, 8 ... Crossaround pipe, 9 ... Low pressure turbine,
10 ... Moisture separator drain pipe, 11 ... High-pressure feed water heater, 1
2 ... Heater drain pipe, 13 ... Drain tank, 14 ... Heat transfer pipe, 15 ... Tube plate, 16 ... Capture sensor, 17 ... Capture sensor side closing plug, 18 ... Closing plug, 19, 22 ... Main valve, 20 ... Hose , 21 ... Vacuum tank, 23 ... Dehumidifier, 24 ... Vacuum pump, 25 ... Vacuum gauge, 26 ... Drain removal valve, 27 ... Ultrasonic transmission seat, 28 ... Ultrasonic sensor, 29 ... Cable, 30 ...
Receiver, 31 ... Cable, 32 ... Recorder, 33
... Sound-sensing bar, 34 ... Adjustment nut, 35 ... One-touch connector, 36 ... Heose for header, 37 ... Multi-axis header, 40 ... Leakage part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuo Obara 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory

Claims (7)

[Claims] 1. A method of inspecting a heat transfer tube for a heat exchanger for inspecting a heat transfer tube used for a heat exchanger, wherein air is sucked from a tube end portion of the heat transfer tube, A method for inspecting a heat transfer tube of a heat exchanger, characterized by detecting air leakage by ultrasonic waves. 2. A heat exchanger heat exchanger tube inspection method for inspecting a heat exchanger tube used in a heat exchanger for the presence of a leak portion, wherein air is sucked from a tube end portion of the heat exchanger tube, and the leak portion is detected. A method for inspecting a heat transfer tube of a heat exchanger, characterized in that air leaks from the air are detected by ultrasonic waves at at least two places, and the position of the leaked portion is specified. 3. A heat exchanger heat exchanger tube inspection device for inspecting a heat exchanger tube used in a heat exchanger for the presence of a leak portion, and a means for sucking air from a tube end portion of the heat exchanger tube; An apparatus for inspecting a heat transfer tube of a heat exchanger, comprising: a sound wave capturing sensor; and means for specifying a position and a size of air leakage from a leak portion detected by the capturing sensor. 4. The heat transfer tube inspection device according to claim 3, wherein the suction means has a plurality of capture sensors and a switching header connected to the capture sensors via a dedicated hose. 5. The heat exchanger according to claim 3, wherein the trapping sensor is formed at one end of the suction means, and the trapping sensor has a taper-shaped closing plug that is in close contact with the wall of the heat transfer tube. Inspection device for heat transfer tubes. 6. The heat exchanger heat exchanger tube inspection device according to claim 3, wherein a plurality of the trap sensors are arranged so as to be evenly located on the inner circumference of the heat exchanger tube. 7. The heat exchanger heat transfer tube inspection device according to claim 3, wherein the specifying means is a sound sensor capable of selectively detecting a specific frequency.