JP2006084443A - Apparatus and method for detecting leakage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of exactly detecting the leakage of fluid in a valve. <P>SOLUTION: A temperature control section controls so as to equalize temperatures around a valve of an object to be detected (S10). An apparatus for detecting the leakage detects AE waves generated inside the valve, while maintaining the temperatures by the temperature control section (S12). The AE waves are inputted through a valve rod and a wave-guide rod to a converting means and thereby are converted into electrical signals. The converted AE signals are inputted to an analyzing device by a signal acquiring section, and the leakage of the fluid in the valve is detected, with analysis for AE signals by an analyzing section (S14). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for detecting fluid leakage in a valve provided in a pipe.

In general, a pipe that forms a fluid flow path is provided with a valve in order to control the flow rate of the fluid (see, for example, Patent Document 1). In the valve described in Patent Document 1, since the disc spring is integrally attached to the valve stem by the disc spring support member, these can be taken out integrally at the time of maintenance and inspected quickly. .
JP-A-8-233154

  However, even if maintenance inspection is easy, fluid may leak in the valve due to wear of the seat packing or the like. When even a small amount of leakage causes a problem, a technique for accurately detecting the leakage is required.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a technique for accurately detecting leakage of fluid in a valve.

  One embodiment of the present invention relates to a leak detection apparatus. The apparatus is a leak detection apparatus for detecting a fluid leak in a valve provided in a pipe, and acquires an acoustic emission generated inside the valve, and the acoustic emission acquired by the acquisition means Analysis means for detecting leakage of the fluid and temperature control means for controlling the temperature of the propagation path of the acoustic emission.

  The temperature control unit may control the temperature of the propagation path to be substantially uniform when the acoustic emission is acquired by the acquisition unit. The temperature control means may perform control so that the temperature of the propagation path does not substantially change when the acoustic emission is acquired by the acquisition means. The temperature control means may perform control so as to suppress a decrease in temperature of the propagation path. As a result, noise can be reduced and fluid leakage can be accurately detected. The temperature control means may be a device that can raise or lower the temperature of the propagation path in accordance with a change in ambient temperature in order to keep the temperature of the propagation path constant, or a control that controls such a device. It may be a program or the like, or may simply be a heat retaining agent for suppressing a temperature change in the propagation path.

  The analysis means may estimate the amount of leakage of the fluid based on the intensity of the acoustic emission at a specific frequency.

  Another aspect of the present invention relates to a leak detection method. This method is a method for detecting a fluid leak in a valve provided in a pipe, the step of acquiring acoustic emission generated inside the valve, and analyzing the acoustic emission to detect the fluid leak. A step of substantially uniforming a temperature of a propagation path of the acoustic emission prior to the obtaining step, wherein the detecting step is set in the step of making uniform. It is characterized by being executed while maintaining the temperature.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the technique which detects exactly the fluid leakage in the valve provided in piping can be provided.

  FIG. 1 shows a configuration example of a leak detection apparatus 20 according to an embodiment of the present invention. The leak detection device 20 is attached to a valve 10 provided in the pipe, and detects a fluid leak in the valve 10. The valve 10 includes a valve lid 13 attached to the valve box 12 and a valve rod 15 that presses a valve body 14 provided at a lower portion of the valve lid 13. The valve stem 15 is rotated by the handle 16 and is slid up and down by the rotation. Then, the valve seat is attached and detached by the vertical movement of the valve body 14, and the flow path is opened and closed.

  It has been found by experiments of the present inventor that when a fluid flows inside the valve 10, an acoustic emission (Acoustic Emission: hereinafter referred to as “AE”) wave having an intensity corresponding to the flow rate is generated. The AE wave is considered to be generated by, for example, friction with the fluid on the surface in contact with the fluid. By utilizing this phenomenon, fluid leakage in the valve 10 can be detected. For example, when the fluid leaks due to factors such as that the flow path is not completely sealed even when the valve 10 is fully closed, the leakage can be detected by detecting the AE wave generated by the flow. Since AE is an elastic wave and propagates through a continuous medium for several meters or more, the occurrence of leakage can be detected with high sensitivity.

  The leak detection device 20 includes a waveguide rod 21 that guides the AE wave generated in the valve 10 to the outside of the valve 10, a jig 22 for fixing the waveguide rod 21 so as to contact the valve rod 15, A conversion unit 23 that converts an AE wave guided by the waveguide rod 25 into an electrical signal, and a cable 24 that transmits the converted electrical signal to the analysis device 30 are provided. The AE wave generated in the vicinity of the valve body 14 propagates through the valve rod 15 and is input to the conversion means 23 via the waveguide rod 21. The conversion means 23 converts the AE wave into an electric signal using a piezoelectric element or the like. The converted electrical signal is input to the analysis device 30 via the cable 24. The analysis device 30 analyzes the input electrical signal and detects fluid leakage in the valve 10.

  According to such a configuration, the AE wave can be efficiently acquired with high sensitivity via the valve rod 15 and the waveguide rod 21. Further, compared with the case where a sensor for detecting the AE wave is attached to the pipe, the detection sensitivity is high and the attachment is easy, and even if the valve 10 is covered with a heat insulating material or the like, the handle It can be attached from the 16th side. Therefore, it is easy to attach and detach, and it is possible to detect leakage even during operation or during stoppage. Furthermore, it is possible to attach even after the piping and the valve 10 are constructed.

  The jig 22 may include an elastic body for pressing the waveguide rod 21 against the outer end of the valve rod 15. According to such a configuration, scattering and attenuation of AE waves at the contact portion between the waveguide rod 21 and the valve rod 15 can be reduced. Further, the waveguide rod 21 and the valve rod 15 may be made of the same material, for example, stainless steel. According to such a configuration, it is possible to reduce reflection and scattering of AE waves at the contact portion between the waveguide rod 21 and the valve rod 15.

  FIG. 2 shows the frequency dependence of the signal level of the AE wave detected by the leak detection device 20. For example, at the frequency in the region indicated by the rectangle 40, the correlation between the flow rate and the AE signal level is high. By monitoring the AE signal level at such a specific frequency, leakage can be detected with high accuracy. As shown in FIG. 2, since the AE wave is generated even when the fluid is not flowing, the leak detection device 20 measures the background noise, and the background noise is detected from the detected AE signal. Remove and analyze.

  FIG. 3 shows the relationship between the flow rate of the fluid and the signal level of the AE wave in the specific frequency region 40 shown in FIG. The signal level obtained by removing background noise from the detected AE signal increases as the amount of leak increases. Therefore, it is possible to quantitatively grasp the amount of leakage based on the intensity of the detected AE signal.

  FIG. 4 shows an example of the internal configuration of the analysis apparatus 30. The analysis device 30 includes a signal acquisition unit 32, an analysis unit 34, and a temperature control unit 36. The signal acquisition unit 32 acquires the electrical signal converted by the conversion unit 23 via the cable 24. The analysis unit 34 analyzes the AE signal acquired by the signal acquisition unit 32. The analysis unit 34 holds the background noise measured when there is no fluid leakage, and removes the background noise from the acquired AE signal. Furthermore, the analysis unit 34 estimates the presence / absence of leakage and the amount of leakage based on the intensity of the AE signal from which background noise has been removed at a predetermined frequency. The frequency used for the analysis may be determined in advance by experiments or the like and held in the analysis unit 34. The analysis unit 34 may hold a threshold for determining that there is a leak, and may determine that a leak has occurred when the AE signal level exceeds the threshold. This threshold value may be determined in consideration of the background noise width, the measurement error of the AE signal, and the like. Moreover, the analysis part 34 may hold | maintain the relationship between signal strength and leakage amount as shown in FIG. 3, and may estimate leakage amount based on signal strength. The relationship between the signal intensity and the leakage amount may be determined in advance by experiments or the like and held in the analysis unit 34.

  When acquiring the AE signal, the temperature control unit 36 controls in advance so that the temperature of the propagation path of the AE wave, such as the inside of the pipe or the valve 10, is uniform, and this temperature is measured during the measurement of the AE signal. Control to maintain. It has been found by experiments of the present inventor that AE is sensitive to temperature changes, and particularly changes significantly as the temperature decreases. It is considered that a certain kind of “stagnation” occurs in the members constituting the valve 10 and the piping due to the temperature change, and as a result, the AE wave is disturbed and noise is generated. Therefore, before the measurement of the AE wave, the temperature of the propagation path of the AE wave is made uniform, and the temperature is kept especially during the measurement so as not to cause a rapid temperature change so as to suppress a decrease in temperature.

  Prior to the measurement of the AE signal, the temperature control unit 36 may control the fluid at a predetermined temperature to flow through the pipe for a predetermined time so as to equalize the temperature around the valve 10. For example, the temperature control unit 36 sends a control signal to an electromagnetic pump (not shown) provided in the pipe, drives the electromagnetic pump for 5 minutes, for example, to flow a fluid through the pipe and the valve 10, and equalizes the temperature of the valve 10 and the pipe. May be. Further, a heat retaining means (not shown) may be provided around the valve 10, and a control signal may be sent to the heat retaining means to keep the temperature at a predetermined temperature. For example, the piping and valve 10 may be kept at a certain temperature between 200 ° C. and 600 ° C. The temperature of the piping and the valve 10 is preferably controlled so as not to drop by 1 ° C. or more from a predetermined temperature. Further, it is preferably controlled so as not to rise from a predetermined temperature by 5 ° C., more preferably by 2 ° C. or more. Thereby, since generation | occurrence | production of noise can be suppressed and an AE signal can be analyzed with sufficient precision, the leak of the fluid in the valve 10 can be detected exactly.

  FIG. 5 is a flowchart showing the procedure of the leak detection method according to the embodiment of the present invention. First, the temperature control unit 36 controls the temperature around the valve 10 to be detected to be uniform (S10). Subsequently, the AE wave generated inside the valve 10 is detected by the leakage detection device 20 while maintaining the temperature by the temperature control unit 36 (S12). The detected AE signal is input to the analysis device 30 by the signal acquisition unit 32, and the analysis unit 34 analyzes the AE signal to detect fluid leakage in the valve 10 (S14).

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there.

It is a figure which shows the structural example of the leak detection apparatus which concerns on embodiment of this invention. It is a figure which shows the frequency dependence of the signal level of the AE wave detected by the leak detection apparatus. It is a figure which shows the relationship between the flow volume of a fluid, and the signal level of the AE wave in the specific frequency area | region shown in FIG. It is a figure which shows the example of an internal structure of an analyzer. It is a flowchart which shows the procedure of the leak detection method which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Valve, 12 ... Valve box, 13 ... Valve lid, 14 ... Valve body, 15 ... Valve rod, 16 ... Handle, 20 ... Leak detection device, 21 ..Waveguide rod, 22 ... Jig, 23 ... Conversion means, 24 ... Cable, 30 ... Analysis device, 32 ... Signal acquisition unit, 34 ... Analysis unit, 36 ..Temperature control unit

Claims (6)

A leak detection device for detecting a fluid leak in a valve provided in a pipe,
Obtaining means for obtaining acoustic emission generated inside the valve;
Analyzing means for analyzing the acoustic emission acquired by the acquiring means to detect leakage of the fluid;
Temperature control means for controlling the temperature of the propagation path of the acoustic emission;
A leak detection apparatus comprising:   The leak detection apparatus according to claim 1, wherein the temperature control unit controls the propagation path to be substantially uniform when the acoustic emission is acquired by the acquisition unit.   The leak detection apparatus according to claim 1, wherein the temperature control unit controls the temperature of the propagation path so as not to change substantially when the acoustic emission is acquired by the acquisition unit. .   The leakage detection apparatus according to claim 3, wherein the temperature control unit performs control so as to suppress a decrease in temperature of the propagation path.   5. The leak detection apparatus according to claim 1, wherein the analysis unit estimates an amount of leak of the fluid based on an intensity of the acoustic emission having a specific frequency. A method for detecting fluid leakage in a valve provided in a pipe,
Obtaining acoustic emissions generated within the valve;
Analyzing the acoustic emission to detect leakage of the fluid; and
Prior to the obtaining step, further comprising substantially uniforming a temperature of a propagation path of the acoustic emission,
The detecting step is performed while maintaining the temperature set in the uniforming step.