JPH06249739A - Tube leakage detector - Google Patents

Abstract

PURPOSE:To provide a tube leakage detector having a simple structure and high sensitivity. CONSTITUTION:A holder 2 is formed at a part to become a node of a vibration of a rodlike ultrasonic resonator 1 made of metal or ceramics, and the resonator 1 is held on a wall of a pressure vessel of an atomic power plant or a thermal power plant by utilizing the holder 2. The resonator 1 is resonated with ultrasonic wave generated at the time of tube leakage, and a vibration sensor 4 mounted at its rear end outputs it as an electric signal. It is preferable to form a vibration plate 5 integrally with the end of the resonator 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tube leak detecting device for detecting a leak in a steam generating tube, a steam heating tube, a tube in a heat exchanger or the like of a nuclear power plant or a thermal power plant. It is a thing.

[0002]

2. Description of the Related Art A pressure vessel composed of a large number of tubes in a nuclear power plant or a thermal power plant, when used for many years, suffers from fatigue deterioration of metal materials due to thermal stress, reduced brittleness, weld defects, or scale adhesion in tubes. Leakage occurs in the tube due to local heating caused by the above, and if it is left as it is, it may lead to troubles such as damage induction to the adjacent tube or decrease in efficiency, and eventually to unit stop.

However, there is no definitive means for detecting a tube leak accident. White smoke from a chimney, steam or water droplets leaking from a flue, water droplets adhering to an inspection door, or steam from a skin casing. A primary discovery is first made due to leaks, abnormal sounds heard through the boiler casing, changes in boiler feed water / make-up water flow, etc., and then the boiler is stopped and the relevant location is found by the hydraulic method, gas charging method, internal visual check, etc. ing. Therefore, a considerable amount of time will elapse from the moment when the leak occurs.

Therefore, an attempt has been made to detect a tube leak more quickly by utilizing a sound wave. For example, Japanese Patent Application Laid-Open No. 2-40521 discloses a method in which a waveguide rod is welded to a boiler housing and a vibration sensor attached to its rear end detects acoustic vibration caused by tube leak. However, in this method, since the tip of the waveguide rod is welded to the boiler housing, indirect acoustic vibration occurs, the transmission efficiency of vibration is poor, and it is difficult to obtain high detection sensitivity. Further, the leak vibration in the superheater and reheater suspended in the boiler is less likely to be transmitted to the boiler housing, so that the detection sensitivity is further low and the detection area is considerably limited.

A method has also been proposed in which a microphone is attached to a boiler housing, a sound wave generated by a leak is detected and converted into an electric signal, and a background noise is removed by a bandpass filter to monitor an abnormality of the boiler. . However, this method of using a microphone requires a structure in which heat resistance, pressure resistance, and dust resistance are taken into consideration with respect to the microphone, and there is a drawback that ancillary equipment becomes large, a large space is required, and equipment cost increases.

Further, a method has also been proposed in which an appropriate number of acoustic emission sensors are installed in the pipe pulling portion of a boiler tube and a leak of the tube is detected from the abnormal signal value generated by the acoustic emission sensors. However, when the total extension distance of each tube is extremely long, such as in a boiler of a thermal power plant, vibration damping on the way from the leak point to the header part is large, so leaks in individual tubes can be detected with high sensitivity at the header part. It is impossible to do.

[0007]

The present invention has been completed to solve the above-mentioned conventional problems, and to provide a tube leak detection device capable of detecting a tube leak with high sensitivity while having a simple structure. It was done.

[0008]

DISCLOSURE OF THE INVENTION The present invention, which has been made to solve the above-mentioned problems, has been proposed in the case where a crack or a pinhole is generated in a pressurized pipe or a pressure vessel and a leak occurs, so that The liquid or gas in the column is ejected at high speed due to the pressure difference between the inside and the outside, and at the same time, it generates a sound wave having a wide frequency component. While forming a holding part in the part that becomes a node of vibration of the body,
It is characterized in that a vibration sensor is attached to the rear end thereof. If the vibration plate is integrally formed at the tip of the ultrasonic resonator, the detection sensitivity can be further improved.

[0009]

The tube leak detecting apparatus of the present invention can be installed on a wall surface of a boiler by using a holding portion formed at a vibration node of the ultrasonic resonator, so The ultrasonic resonator resonates. Therefore, the vibration can be taken out by a vibration sensor, and the presence or absence of leak can be detected by using one or more of the resonance frequencies. Since the resonance phenomenon is used, the transmission efficiency of vibration is high, and highly sensitive detection is possible. In addition, since the ultrasonic resonator is made of metal or ceramics with excellent heat resistance and pressure resistance, and its tip can be directly projected into the pressure vessel such as a boiler, the leak sound from a wide range can be efficiently generated. Since it can be detected and does not require a special protection device such as a microphone system, it has an advantage that the device is simple and the installation space is small.

[0010]

The present invention will be described below in more detail with reference to the illustrated embodiments. FIG. 1 shows a first embodiment, 1 is a rod-shaped ultrasonic resonator made of alumina ceramics,
Reference numeral 2 is a double-ring-shaped holding portion formed in a portion serving as a node of the vibration. The ultrasonic resonator 1 is held by using this holding portion 2, but an auxiliary holding portion 3 is also formed in the rear portion. Reference numeral 4 denotes a vibration sensor adhered to the rear end portion of the ultrasonic resonator 1, and a piezoelectric ceramics sensor is used here, and mechanical vibration of the ultrasonic resonator 1 can be converted into an electric signal and taken out. There is.

FIG. 2 shows a second embodiment, in which a disc-shaped vibrating plate 5 is integrally formed at the tip of the ultrasonic resonator 1. Further, in this embodiment, in addition to the holding portion 2, two auxiliary holding portions 3 are formed. Although the ultrasonic resonator 1 made of solid alumina ceramics is used in each of the embodiments, it may be made of heat-resistant and pressure-resistant metal. It should be noted that since a hollow body complicates the vibration state, a solid body is used here, but it is not necessarily limited to this.

FIG. 3 shows a state in which the tube leak detecting device of the second embodiment is attached to the through hole 7 formed in the wall surface 6 of the boiler. 4 and 5 are views for explaining the mounting structure. As shown in these drawings, in the embodiment, the holding portion 2 provided at a portion serving as a node of vibration of the ultrasonic resonator 1 is provided with two holding plates 8 and 8 from above and below.
The ultrasonic resonator 1 is held only by the portion that serves as a vibration node by sandwiching it between the front end portions of the two and fixing the rear end portions of these two holding plates 8 to the bracket 9 of the wall surface 6 of the boiler. ing. However, since this alone may cause the ultrasonic resonator 1 to shake laterally, the bolts 10 are also provided on both sides of the auxiliary holding portion 3 on the way. As described above, the tube leak detection device of the present invention is directly inserted into the inner wall of the boiler without welding or the like, and the ultrasonic wave at the time of leak can be directly captured without the intermediate material.

FIG. 6 shows the resonance points of the ultrasonic resonator 1 of the second embodiment, which are about 10 kHz, 16 kHz, 29 kHz and 43 kHz.
Four resonance points at kHz are shown. Generally, when a leak occurs in the boiler tube, vibration in the ultrasonic region of 5000 to 50000 Hz occurs, so that the ultrasonic resonator 1 resonates largely due to the vibration that matches its resonance frequency, and this Sensitivity can be detected by converting the electric signal into an electric signal and extracting the electric signal by the vibration sensor 4 whose characteristics match the region.
Although one of the resonance frequencies may be used, the detection accuracy can be further improved by using two or more resonance frequencies to detect the leak.

[0014]

As described above, since the leak is detected by utilizing the resonance phenomenon of the ultrasonic resonator in the tube leak detecting apparatus of the present invention, it is possible to obtain an extremely high vibration transmission efficiency and reduce the sensitivity. Good detection is possible. Also, use metal or ceramics with excellent heat resistance and pressure resistance as the ultrasonic resonator, and project the tip directly into the pressure vessel such as a boiler without an intermediate material, as shown in FIG. Therefore, it is possible to efficiently detect the leak sound from a wide range, and to reliably detect the leak at any part. Further, since this ultrasonic resonator does not require a special protection device, the device is simple, the installation space is small, and the equipment cost is low. The tube leak detection device of the present invention can also be applied to the detection of tube leaks other than boilers.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment.

FIG. 2 is a perspective view showing a second embodiment.

FIG. 3 is a cross-sectional view showing a state in which the tube leak detection device of the second embodiment is attached to the wall surface of a boiler.

FIG. 4 is a perspective view illustrating a mounting structure of an ultrasonic resonator.

FIG. 5 is a side view illustrating a mounting structure of an ultrasonic resonator.

FIG. 6 is a graph showing resonance points of the ultrasonic resonator according to the second embodiment.

[Explanation of symbols]

 1 ultrasonic resonator 2 holding part 4 vibration sensor 5 diaphragm

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shigehiro Matsuda 11-1 Oguro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Tokyo Electric Power Co., Inc. Yokohama Power Plant (72) Koichi Takamura 11 Oguro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa No. 1 Toyo Electric Power Co., Inc. Yokohama Power Station (72) Inventor Shunichi Kiyosawa 2-14, Uchisaiwaicho, Chiyoda-ku, Tokyo Inside Toden Design Co., Ltd. (72) Toru Asami 2-chome, Uchisaiwaicho, Chiyoda-ku, Tokyo No. 4 Toden Design Co., Ltd. (72) Inventor Hiroshi Yamada 1-409, Tokushige, Midori-ku, Nagoya, Aichi Prefecture (72) Shinichi Naruse 3-61, Sounaka-cho, Kasugai-shi, Aichi Prefecture

Claims (3)

[Claims] 1. A holding portion is formed at a portion which becomes a node of vibration of a rod-shaped ultrasonic resonator capable of resonating with ultrasonic waves generated at the time of tube leak, and a vibration sensor is attached to a rear end portion thereof. Tube leak detector. 2. The tube leak detection device according to claim 1, wherein a vibration plate is integrally formed at the tip of the ultrasonic resonator. 3. The pressure vessel composed of a tube or a heat exchanger is directly inserted, and the ultrasonic wave generated when the tube leaks is directly captured without an intermediate material. Tube leak detector.