JP2012052836A - Leakage detection device of liquid transport pipeline and method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a leakage detection device capable of reducing processing time.SOLUTION: A leakage detection device of the present invention comprises: a leakage detection cable 11 which is laid down along a pipeline and changes characteristic impedance thereof when liquid leaking from the pipeline infiltrates the same; a leakage detection pulse signal generation section 33 to generate a leakage detection pulse signal incident on the leakage detection cable; a storage section 23 to store data indicating a correlation between a propagation distance of reflection wave and attenuation of the reflection wave; an amplification factor variable gain amplifier 53 which is a gain amplifier to amplify the reflection wave with respect to the leakage detection pulse signal in synchronism with a sampling signal repeated with a predetermined sampling cycle and changes an amplification factor of the reflection wave based on the data; and an A/D conversion section 61 to convert the sampled reflection wave into a digital pulse signal by sampling the amplified reflection wave with respect to one leakage detection pulse signal a plurality of times in synchronism with a sampling signal.

Description

  The present invention relates to a leak detection apparatus for a liquid transportation pipeline such as an oil pipeline. Specifically, a change in characteristic impedance of a detection cable line such as a coaxial cable is detected by detecting a reflected wave of a pulse signal incident on the detection cable, and a defective portion of the detection cable and a liquid transport pipeline are detected. The present invention relates to a leak detection apparatus that identifies a leak location or the like in a short time.

  As one method for measuring the characteristic impedance of a coaxial cable, a TDR method (Time Domain Reflectometry) is known. As detectors to which the TDR method is applied, there are a detector that detects an abnormal portion of a coaxial cable, a leak detector that uses the coaxial cable as a detection cable, and the like. For example, in order to detect the leakage of liquid from a liquid transport pipeline having a length of 10 m or more, especially about 100 m to 5000 m, and a storage tank, and their associated equipment (hereinafter referred to as a liquid transport pipeline, etc.) There is known a leak detection apparatus applying the method (see Patent Documents 1 to 3). This leakage detection device includes a detection cable configured by a coaxial cable, a pulse signal generator that generates a pulse signal incident from one end of the detection cable, and a detector that detects a reflected wave of the pulse signal from the detection cable And have. The detection cable is arranged below the liquid transport pipeline, etc., and the insulator that is arranged between the conductors in the detection cable is made of a material whose characteristic impedance changes when the liquid to be detected infiltrates or penetrates. The Further, a terminator having an impedance equivalent to the characteristic impedance of the detection cable is connected to the other end of the detection cable so as to be matched with the characteristic impedance. For this reason, when there is no leakage, the pulse signal incident on the detection cable does not generate a reflected wave. However, when the liquid leaks from the liquid transport pipeline or the like, the liquid leaking from the pipeline penetrates the detection cable, and the characteristic impedance of the penetrated portion changes. As a result, when a pulse signal is incident on the detection cable, a reflected wave is generated before and after the portion where the characteristic impedance has changed due to liquid infiltration. The detector detects leakage by detecting this reflected wave.

  In addition, using such a leak detection device, it is possible to detect a leak and identify a leak location. For example, as disclosed in Patent Document 4, the leak location is calculated from the measured value of the time from when the pulse signal is incident on the detection cable until the reflected wave is detected and the pulse signal propagation time of the detection cable. be able to.

  In a conventional leak detection apparatus using the TDR method, a method is adopted in which the characteristic impedance at each measurement point is grasped by measuring the reflected wave at one point each time a pulse signal is incident. This is because the attenuation of the reflected wave depends on the propagation distance between the measurement point and the detection point, and the amplification factor of the reflected wave is different for each measurement point.

JP 54-68690 A JP 56-22923 A Japanese Patent Application Laid-Open No. 57-114832 JP 58-33145 A

  However, in the conventional leak detection device, the number of measurements increases as the length of the pipeline to be measured increases, and as the interval between the measurement points is narrowed to increase the resolution of the measurement value. There was a problem that the processing time was increased in proportion to the number of times.

  Accordingly, an object of the present invention is to provide a leak detection apparatus that can solve the above-described problems.

  Further, the present invention shortens the processing time by employing an amplification unit that amplifies the reflected wave at a specific sampling period based on data representing the correlation between the propagation distance of the reflected wave and the attenuation of the reflected wave. An object is to provide a leak detection device.

  In order to achieve the above object, a leak detection device of the present invention is a device that detects a liquid leak from a liquid transport pipeline by detecting a reflected wave of a leak detection pulse signal incident on a leak detection cable. A leak detection cable that is laid along the pipeline and changes its characteristic impedance when liquid leaked from the pipeline permeates, and a leak detection pulse signal generator that generates a leak detection pulse signal incident on the leak detection cable And a storage unit for storing data representing the correlation between the propagation distance of the reflected wave and the attenuation of the reflected wave, and the reflected wave with respect to the leak detection pulse signal is amplified in synchronization with the sampling signal repeated at a predetermined sampling period. A gain amplifier that changes the gain of the reflected wave based on the data; In synchronism with the ring signal, a reflected wave is amplified for one leak detection pulse signal sampled a plurality of times, and having an A / D converter for converting the reflected wave sampled digital signal.

  According to the present invention, since it has the gain amplifier that amplifies the reflected wave based on the data representing the correlation between the propagation distance of the reflected wave and the attenuation of the reflected wave for each predetermined sampling period, the liquid transport pipeline A leak detection device that can detect the presence or absence of liquid leak in a short time can be realized.

It is a figure which shows an example of the leak detection apparatus which concerns on this invention. It is a figure which shows an example of the detection cable employ | adopted with the leak detection apparatus which concerns on this invention. It is a figure which shows an example of the circuit structure of the gain amplifier employ | adopted with the leak detection apparatus which concerns on this invention. It is a figure which shows an example of the timing chart which concerns on this invention. It is a figure which shows an example of the leak detection method which concerns on this invention. It is a figure which shows the other example of the leak detection apparatus which concerns on this invention. It is a figure which shows an example of the circuit structure of the delay amount selection part employ | adopted with the leak detection apparatus which concerns on this invention. It is a figure which shows the other example of the timing chart which concerns on this invention. It is a figure which shows the other example of the leak detection method which concerns on this invention.

  Hereinafter, a leak detection apparatus according to the present invention will be described in detail with reference to the accompanying drawings. In each drawing, components having the same or similar functions are denoted by the same or similar reference numerals. Therefore, a component having the same or similar function as the component described above may not be described again.

  FIG. 1 shows an example of a leak detection apparatus according to the present invention. As shown in FIG. 1, the leak detection device 1 includes a detection sensor 11 and a signal processing unit 2. The detection sensor 11 is disposed below the liquid transport pipeline 100 that transports a liquid such as petroleum. When the liquid leaks from the liquid transport pipeline 100, the leaked liquid penetrates the detection sensor 11. The signal processing unit 2 inputs a pulse signal to the detection sensor 11, processes a reflected wave generated when the leaked liquid penetrates the detection sensor 11, detects a leak in the liquid transport pipeline 100, and detects the leak location Identify.

  In FIG. 2, an example of the detection cable 11 employ | adopted with the leak detection apparatus 1 which concerns on this invention is shown. As shown in FIG. 2, the detection cable 11 includes an inner conductor 11a and an outer conductor 11b. The inner conductor 11a can be formed of bare annealed copper or the like, and the outer conductor 11b is braided with a tinned annealed copper wire, or a braid of a tinned annealed copper wire and a porous PTFE (polytetrafluoroethylene) tape. Can be formed. As shown in FIG. 1, one end of the internal conductor 11 a is connected to the signal processing unit 2, and the other end is preferably connected to the terminator 13. The impedance of the terminator 13 can be equivalent to the characteristic impedance of the detection cable 11. Accordingly, it is possible to prevent a reflected wave from being generated when a pulse signal is incident from one end of the detection cable. The outer conductor 11b is grounded to the ground.

  Referring to FIG. 2 again, an inner protective layer 11c and a detection layer 11d are disposed between the inner conductor 11a and the outer conductor 11b of the detection cable 11. An outer protective layer 11e and a protective braid 11f are disposed on the outer periphery of the outer conductor 11b. The outer protective layer 11e and the detection layer 11d disposed on the outer periphery of the outer conductor 11b are formed of porous PTFE tape. As known to those skilled in the art, porous PTFE has good water repellency, while having the property of easily penetrating oils. For this reason, the external protective layer 11e, the external conductor 11b, and the detection layer 11d including a porous PTFE tape as a material can transmit oil without allowing moisture such as rainwater to permeate. Furthermore, PTFE has the characteristic that the dielectric constant changes by containing oils. For this reason, the characteristic impedance of the detection cable 11 changes in the detection layer 11d formed between the inner conductor 11a and the outer conductor 11b when oil penetrates. The porous PTFE tape employed for the material such as the detection layer 11d can be various porous PTFE tapes having different air contents in the porous material. By changing the air content in the porous material, a porous PTFE tape having a desired dielectric constant can be formed. The inner protective layer 11c is formed of a resin such as PFA (perfluoroalkoxyalkane) and can prevent oils from penetrating into the inner conductor 11a.

  The detection cable 11 and the signal processing unit 2 can be directly connected, but preferably, a dummy cable 15 can be inserted between the detection cable 11 and the signal processing unit 2. This is because when the dummy cable 15 is not inserted, there is a possibility that the incident pulse signal and the reflected wave are superimposed and the reflected wave cannot be detected. The length of the dummy cable is determined by the pulse width of the input leakage detection pulse. For example, the length of the dummy cable can be set to 100 [m]. In addition, a safety barrier 110 can be disposed between the liquid transport pipeline 100 and the detection cable 11. The safety barrier 110 has a function of preventing a combustible liquid such as petroleum leaking from the liquid transport pipeline 100 from igniting due to heat generated by the detection cable 11 or the like.

  With reference to FIG. 1 again, the signal processing unit 2 of the leak detection apparatus 1 will be described. The signal processing unit 2 includes a central processing unit (CPU) 21, a storage unit 23, a pulse generation unit 31, a pulse width control unit 33, an I / O unit 41, and a digital-analog conversion unit (DAC) 51. A gain amplifier 53, an analog-digital converter (ADC) 61, and a data I / O unit 71. The CPU 21 is connected to the storage unit 23, the pulse generation unit 31, the pulse width control unit 33, and the like, and controls each element. The pulse generation unit 31 generates a pulse signal based on the control of the CPU 21, provides the pulse signal to the pulse width control unit 33 that generates a signal incident on the detection cable 11, and controls the gain amplifier 53 that amplifies the reflected wave. This is provided as a sampling signal to the CPU 21 and the ADC 61 that converts the reflected wave into digital data. The pulse width control unit 33 changes the cycle of the pulse signal generated by the pulse generation unit 31 and the pulse width by a frequency divider circuit or the like, and generates a leak detection pulse signal suitable for input to the detection cable 11. . For example, when the detection cable has a length of about 1000 [m], the leakage detection pulse signal may have a pulse width of about 200 [ns] to 250 [ns]. The leak detection pulse signal generated by the pulse width control unit 33 is transmitted to the detection cable 11 via the I / O unit 41. The leakage detection pulse signal incident on the detection cable 11 is absorbed by the terminator 13 when there is no leakage in the liquid transport pipeline 100 and the characteristic impedance of the detection cable 11 does not match in the line direction. No reflected wave is generated.

  On the other hand, when liquid leakage occurs in the liquid transport pipeline 100 and the characteristic impedance of the detection cable 11 is mismatched in the line direction, a reflected wave is generated. The reflected wave generated in the detection cable 11 is transmitted to the gain amplifier 53 via the I / O unit 41 having a buffer and an attenuator. As will be described in detail later, the gain amplifier 53 detects the leakage point based on the gain table stored in the storage unit 23 that is read out via the DAC 51 for each sampling period of the sampling signal generated by the pulse generation unit 31. The reflected wave is amplified to an appropriate size according to the above. The reflected wave amplified by the gain amplifier 53 is sampled by the ADC 61 at the sampling period of the sampling signal generated by the pulse generator 31 and converted into a digital signal. The signal digitized by the ADC 61 is stored in the storage unit 23 and also provided to the display device 113 and the storage device arranged outside the data processing unit 2 via the data I / O unit 71.

で示される。ここで、ｃは、真空中の光速２．９９×１０⁸〔ｍ／ｓ〕であり、μは、比透磁率であり、εは、比誘電率である。また、検出ケーブル１１を漏洩検出パルス信号、及び反射波が１ｍ移動する時間ｔｃは、信号の伝搬速度Ｖｃの逆数で表すことができるので、ｔｃは、

で示される。ここで、比透磁率μを、１と仮定し、検出ケーブル１１の検出層に使用される多孔質ＰＴＦＥの比誘電率εを、１．５と仮定すると、検出ケーブル１１中を漏洩検出パルス信号、及び反射波が１ｍ移動する時間ｔｃは、

となる。さらに、検出ケーブル１１の入射端から漏洩検出パルス信号が入射し、Ｌ〔ｍ〕離れた地点で反射した反射波が戻ってくるまでの時間Δｔ〔ｎｓ〕は、
Δｔ ＝ ２×Ｌ×ｔｃ ≒ ８Ｌ〔ｎｓ〕
となる。一方、パルス生成部３１が生成するパルス信号の周波数が例えば、３１．２５〔ＭＨｚ〕であると仮定すると、パルス信号の周期Ｔは、
Ｔ ＝ １／３１．２５×１０⁶ ＝ ３２×１０^-9〔ｓ〕
＝ ３２〔ｎｓ〕
となる。これから、比誘電率εが１．５である多孔質ＰＴＦＥを有する検出ケーブルを使用した場合に、このパルス信号を使用して、３１．２５〔ＭＨｚ〕のサンプリング周波数で反射波をサンプリングすることは、
Ｌ ＝ ３２／８ ＝ ４〔ｍ〕
ごとの検出ケーブル１１の反射波を検出することに相当する。このように、パルス生成部３１が生成する特定のサンプリング周波数で反射波をサンプリングすることは、検出ケーブル１１を特定の距離間隔でサンプリングすることに相当する。 Here, the correlation between the frequency of the pulse signal generated by the pulse generator 31 and the distance between the incident end of the detection cable 11 and the measurement point will be described. First, the leakage detection pulse signal and the time tc [s / m] for which the reflected wave moves 1 m in the detection cable 11 are calculated. As derived from Maxwell's equations, the propagation speed Vc of the electromagnetic signal in the material is

Indicated by Here, c is the speed of light in vacuum of 2.99 × 10 ⁸ [m / s], μ is the relative permeability, and ε is the relative permittivity. Further, since the leak detection pulse signal and the time tc during which the reflected wave moves 1 m through the detection cable 11 can be expressed by the reciprocal of the signal propagation velocity Vc, tc is

Indicated by Here, assuming that the relative permeability μ is 1, and assuming that the relative permittivity ε of the porous PTFE used for the detection layer of the detection cable 11 is 1.5, the leakage detection pulse signal is passed through the detection cable 11. , And the time tc when the reflected wave moves 1 m is

It becomes. Furthermore, the time Δt [ns] from when the leakage detection pulse signal is incident from the incident end of the detection cable 11 until the reflected wave reflected at a point away from L [m] returns.
Δt = 2 × L × tc≈8L [ns]
It becomes. On the other hand, assuming that the frequency of the pulse signal generated by the pulse generator 31 is, for example, 31.25 [MHz], the period T of the pulse signal is
T = 1 / 31.25 × 10 ⁶ = 32 × 10 ⁻⁹ [s]
= 32 [ns]
It becomes. From this, when using a detection cable having porous PTFE having a relative dielectric constant ε of 1.5, it is possible to sample a reflected wave at a sampling frequency of 31.25 [MHz] using this pulse signal. ,
L = 32/8 = 4 [m]
This corresponds to detecting the reflected wave of each detection cable 11. As described above, sampling the reflected wave at the specific sampling frequency generated by the pulse generation unit 31 corresponds to sampling the detection cable 11 at a specific distance interval.

  In the following description, it is assumed that the pulse frequency generated by the pulse generator 31 is 31.25 [MHz], and the detection cable 11 has porous PTFE having a relative dielectric constant ε of 1.5. That is, it is assumed that the sampling frequency generated by the pulse generator 31 corresponds to sampling the detection cable 11 every 4 [m]. However, when using the leakage detection apparatus and method according to the present invention, it is included in the scope of the present invention even if the detection cable 11 having other pulse frequency and relative dielectric constant ε is used. Those skilled in the art will naturally understand.

  Next, referring to FIG. 1 again, a method for amplifying the reflected wave in the gain amplifier 53 will be described. Based on the gain table stored in the storage unit 23, the gain amplifier 53 amplifies the reflected wave with an appropriate amplification factor according to the distance from the incident end. The gain table stored in the storage unit 23 stores data indicating the correlation between the distance between the end where the leak detection pulse signal is incident and the measurement point, that is, the propagation distance of the reflected wave and the attenuation of the reflected wave. Is done. The CPU 21 reads the data stored in the gain table at the cycle of the sampling signal generated by the pulse generator 31 and provides it to the DAC 51 as a control signal for the gain amplifier 53. This control signal corresponds to a control signal for controlling the gain of the gain amplifier 53. The gain amplifier 53 amplifies the reflected wave with an appropriate gain according to the propagation distance of the reflected wave. It is. In the gain table, data corresponding to a control signal for controlling the gain of the gain amplifier 53 can be stored, and an actual measurement value such as the attenuation rate of the reflected wave for each propagation distance of the reflected wave can also be stored. . In the latter case, the storage unit 23 stores data indicating the correlation between the stored actual measurement value and the gain of the gain amplifier 53, and the CPU 21 calculates an appropriate gain based on these data. . Preferably, the interval between the measurement points of the reflected wave attenuation rate stored in the gain table can be a distance interval synchronized with the sampling period. For example, when the sampling period of the pulse signal of the pulse generation unit 31 corresponds to every 4 [m], the gain table interval can be set every 4 [m]. Note that the correspondence between the propagation distance of the physical reflected wave and the distance corresponding to the amplification value stored in the gain table depends on the length of the dummy cable and the location of the leak detection device when installing the leak detection device. And the installation conditions such as the distance to the detection target pipeline.

  The gain amplifier 53 can have two modes: a disconnection of the detection cable 11 or a disconnection / short-circuit detection disconnection / short-circuit detection test mode for detecting a short circuit, and a leak detection mode for detecting a liquid leak in the liquid transport pipeline. . Since the reflected wave generated at the time of disconnection or short circuit has an amplitude several times larger than the reflected wave generated at the time of leakage, there is a possibility of damaging the amplification element inside the gain amplifier 53 and an electronic circuit element such as the ADC 61. It is. The disconnection / short circuit detection test mode can be executed before the leakage detection mode is executed. FIG. 3 shows an example of the gain amplifier 53 having two modes of a short circuit detection test mode and a leak detection mode. As shown in FIG. 3, the reflected wave input from the I / O unit includes a signal provided directly to the multiplexer 56 via the buffer 54, and a signal provided to the multiplexer 56 via the amplification element 55. Distributed to. The multiplexer 56 provides the former to the amplification element 57 in the disconnection / short-circuit detection test mode, and provides the latter to the amplification element 57 in the leakage detection mode. The amplifying element 57 amplifies the reflected wave based on a control signal generated from the gain table stored in the storage unit 23 via the DAC 51. The reflected wave amplified by the amplifying element 57 is provided to the ADC 61 via the buffer 58.

  Next, the reflected wave is sampled in the ADC 61 at the period of the sampling signal generated by the pulse generation unit 31 and digitally converted. Since both the digital conversion in the ADC 61 and the amplification in the gain amplifier 53 are executed in the sampling cycle of the sampling signal generated by the pulse generation unit 31, both processes are executed in synchronization. Further, the ADC 61 can have a function capable of preventing an input of an unnecessary signal to the ADC 61 such as a signal having a large amplitude when an ADC input cutoff signal is input. By having such a function, the ADC 61 can avoid a signal having a large amplitude such as a reflected wave generated at the time of disconnection or short circuit.

  With reference to FIG. 4, the timing of the sampling signal, the leak detection pulse signal, and the ADC input cutoff signal will be described. FIG. 4 is a diagram illustrating an example of a timing chart in the present embodiment. The sampling signal is a pulse signal generated by the pulse generator 31 shown in FIG. The period of the sampling signal depends on the dielectric constant ε of the detection layer of the detection cable 11 and the distance between measurement points. For example, when the relative dielectric constant ε of the detection layer of the detection cable 11 is 1.5 and the distance between measurement points is 4 [m], the period of the sampling signal can be 32 [ns]. The distance of 0 [m] to 32 [m] added to the sampling signal is the propagation distance of the reflected wave. The 0 [m] point is determined based on installation conditions such as the length of the dummy cable to be inserted, the installation location of the leak detection device, and the distance between the pipeline to be detected. The leakage detection pulse signal is formed by, for example, dividing the sampling signal generated by the pulse generator 31 by the pulse width controller 33 shown in FIG. In the example shown in FIG. 4, the pulse width of the leak detection pulse signal has a length corresponding to eight cycles of the sampling signal. The ADC input cut-off signal is a signal that cuts off the input of the ADC 61 so that an unexpected waveform such as a waveform having a large amplitude is not input to the ADC 61. Here, the leakage detection pulse signal is output from the pulse width control unit 33 and during an appropriate time after the leakage detection pulse signal is output so that the leakage detection pulse signal is not input to the ADC 61. The The reflected wave is a diagram schematically showing an analog signal observed at the input end of the ADC 61. A waveform indicated by an arrow A is a part of a leak detection pulse signal input via a protection diode, and an amplitude is about 0.5 [V]. The waveform indicated by arrow B is a reflected wave of the leak detection pulse signal. As described above, since the other end of the detection cable 11 is terminated by the terminator 13 having an impedance equivalent to the characteristic impedance of the detection cable 11, no reflected wave is normally generated. However, when the characteristic impedance of the detection cable 11 changes due to liquid leakage from a liquid transport pipeline or the like, a reflected wave is generated. Here, an example in which liquid leakage occurs between 16 [m] and 24 [m] is shown.

  Here, referring to FIG. 1 again, the reflected wave digitally converted by the ADC 61 is stored as processing data in the storage unit 23 or the like. Based on the processing data stored in the storage unit 23, the presence or absence of liquid leakage in the liquid transport pipeline can be determined. For example, the processing data can be displayed as a waveform graph or the like on the display device 113 such as an LCD display device connected to the leak detection device 1 via the data I / O unit 71. The inspector can determine the presence or absence of liquid leakage in the liquid transport pipeline by inspecting this display. Further, by comparing the reference data stored in the storage unit 23 or the storage device 115 with the processing data, it is possible to determine the presence or absence of liquid leakage in the liquid transport pipeline. The reference data may be created based on the measured value measured when the leak detection apparatus 1 is installed, or may be created based on the average value of the latest plurality of processing data. A predetermined threshold value may be further used when determining the presence or absence of liquid leakage. For example, the presence or absence of liquid leakage can be determined by comparing the maximum difference value between the processing data and the reference data with a predetermined threshold value. Furthermore, when determining the presence or absence of liquid leakage, an average value of a plurality of processing data may be used. This is to eliminate the influence of irregular noise such as thermal noise by using the average value of a plurality of processing data. Preferably, when determining the presence or absence of liquid leakage, it is desirable to use an average value of processing data of about 50 to 100. For example, an average value of 64 data can be used.

  As described above, the leak detection apparatus 1 reads the gain table stored in the storage unit 23 at a predetermined sampling period, and gives the reflected wave an appropriate amplification factor according to the propagation distance of the reflected wave. A plurality of reflected waves can be detected with respect to the leakage detection pulse signal. For example, when sampling reflected waves every 4 [m], it is possible to detect 250 reflected waves per 1000 [m] for one leak detection pulse signal. For this reason, in the leak detection apparatus 1 which concerns on this invention, compared with the conventional leak detection apparatus which detects one reflected wave with respect to one leak detection pulse signal, detection time can be shortened significantly. Further, in the leak detection apparatus 1 according to the present invention, a leak detection pulse signal incident on the detection cable 11 is generated using the signal generated by the single pulse generation unit 31, and the gain amplifier 53 and the ADC 61 are also generated. Therefore, it is easy to control the pulse signal and the reflected signal, and there is an advantage that the number of constituent elements can be reduced.

  Next, an example of a method for detecting liquid leakage from the liquid transport pipeline using the leakage detection apparatus 1 will be described with reference to FIG. As shown in FIG. 5, in step 101, the CPU 21 generates a pulse signal having a predetermined period. Based on this pulse signal, a leak detection pulse signal incident on the detection cable 11 is generated, and the reflected wave from the detection cable 11 is amplified and A / D converted. Next, at step 102, the CPU 21 causes the leakage detection pulse signal generated based on the pulse signal to enter the detection cable. After a suitable time has elapsed, in step 103, the CPU 21 amplifies the reflected wave at a predetermined sampling signal period, and in step 104, converts the amplified reflected wave from an analog signal to a digital signal. In step 105, the CPU 21 stores the data converted into the digital signal.

  In step 106, the CPU 21 determines whether steps 102 to 105 have been executed a predetermined number of times. If these steps have not been executed a predetermined number of times, the CPU 21 again enters the leak detection pulse signal into the detection cable in step 102. If these steps have been executed a predetermined number of times, in step 107, the CPU 21 compares the processing data that has undergone further processing such as averaging with the given reference data, and enters the liquid transport pipeline. It is determined whether or not liquid leakage has occurred.

  FIG. 6 shows another example of the leak detection apparatus according to the present invention. As shown in FIG. 6, the leak detection device 3 includes a detection sensor 11 and a signal processing unit 4. The signal processing unit 4 included in the leakage detection device 3 is different from the signal processing unit 2 included in the leakage detection device 1 in that it includes a delay amount selection unit 81. Therefore, here, the matters relating to the delay amount selection unit 81 which is the difference will be mainly described, and the explanation relating to the matters overlapping with the matters described above will be omitted.

  As shown in FIG. 6, the delay amount selection unit 81 receives the pulse signal generated by the pulse generation unit 31 and also receives the selection signal from the CPU 21 and is delayed by the delay amount selected by the selection signal. Is provided to the CPU 21 and the ADC 61 as a sampling signal. That is, the delay amount selection unit 81 can execute processing in the gain amplifier 53 and the ADC 61 at a timing delayed by the selected delay amount with respect to the pulse signal generated by the pulse generation unit 31. is there. As a result, leak detection can be performed with higher resolution than the leak detection device 1 that does not include the delay amount selection unit 81. That is, it is possible to shorten the measurement distance interval of the detection cable 11 and improve the resolution by sampling the time between the periods of the leakage detection pulse signal with the sampling signal delayed by the delay amount selection unit 81. is there.

  The operation of the leakage detection device 3 having the delay amount selection unit 81 is performed by using the detection cable 11 having the porous PTFE having the relative dielectric constant ε of 1.5 described above and the pulse signal generated by the pulse signal generation unit 31. A case where the frequency is 31.25 [MHz] will be described as an example. In this example, the period of the pulse signal is 32 [ns], which corresponds to 4 [m] when converted to the sampling distance interval of the detection cable 11. Consider a case in which this pulse signal is applied to a delay amount selection unit 81 configured by a circuit as shown in FIG. As shown in FIG. 7, the delay amount selection unit 81 controls a pulse signal obtained by delaying the pulse signal generated by the pulse generation unit 31 through delay elements 83a, 83b, 83g, and the like by the selection signal. The data is selected by the selector 85 and provided to the ADC 61 and the CPU 21. First, as shown in the timing chart of FIG. 8, when the selector 85 shown in FIG. 7 outputs the pulse signal input to Din0 to Dout, the sampling points of the pulse signal are 0 [m], 4 [m] in order. ], 8 [m],. . . , 992 [m], 996 [m], 1000 [m],. . . Is assumed to correspond. Then, when the pulse signal input to Din1 delayed by 4 [ns] from the pulse signal input to Din0 is output to Dout, sampling points are 0.5 [m], 4.5 [m], 8.5 [m],. . . 992.5 [m], 996.5 [m], 1000.5 [m],. . . Corresponding to This is because 4 [ns], which is the delay difference between both pulse signals, corresponds to 0.5 [m] in the distance interval of the detection cable 11. Similarly, when the pulse signal input to Din2 delayed by 8 [ns] from the pulse signal input to Din0 is output to Dout, sampling points are 1 [m], 5 [m], and 9 [m]. ],. . . , 993 [m], 997 [m], 1001 [m],. . . Corresponding to Hereinafter, similarly, the reflection of the detection cable 11 with a resolution of 4 [ns], that is, 0.5 [m], until the pulse signal input to Din7 delayed by 28 [ns] from the pulse signal input to Din0. Waves can be detected.

  As described above, by delaying the pulse signal by an appropriate delay amount and sampling the reflected wave, the resolution of the detection cable 11 can be increased without increasing the frequency of the pulse signal generated by the pulse generator 31. it can. In general, it is possible to increase the sampling frequency as long as the operation speed of electronic devices such as a CPU, DAC, and ADC, and performance such as resolution allow. However, when the sampling frequency is increased, it is necessary to use a signal processing circuit and a CPU having a high data rate. In general, the price of electronic components such as the ADC 51 and the DAC 61 increases exponentially as the rated sampling frequency increases. In order to cope with high-frequency operation, the electronic circuit board must also use an expensive board with high noise resistance. For this reason, if the frequency of the pulse signal generated by the pulse generation unit 31 is increased, the price of each element constituting the signal processing unit 4 increases, which may increase the manufacturing cost. Furthermore, as the sampling frequency is increased, the possibility of jitter between signals increases, and the reliability may be reduced. In the leak detection device 3 having the delay amount selection unit 81, a plurality of signals obtained by delaying the pulse signal by different delay amounts are used as sampling signals without increasing the frequency of the pulse signal generated by the pulse generation unit 31. , Can increase the resolution. For example, even when a general-purpose pulse generator that generates a frequency such as 31.25 [MHz] is used, data with sufficiently high resolution and reliability can be acquired in a short time.

  Next, an example of a method for detecting liquid leakage from the liquid transport pipeline using the leakage detection device 3 having the delay amount selection unit 81 will be described with reference to FIG. As shown in FIG. 9, in step 201, the CPU 21 provides a selection signal to the delay amount selection unit 81. Steps 202 to 207 are the same as steps 101 to 106 in FIG. In step 208, after the leakage detection pulse is incident on the detection cable 11 for a predetermined number of times and the reflected signal is stored, the CPU 21 determines whether or not there is a delay amount not selected by the delay amount selection unit 81. To do. If there is an unselected delay amount, the process returns to step 201. If all the delay amounts are selected, in step 209, the CPU 21 combines the processing data delayed by different delay amounts into one data. By combining the processing data, processing data with improved resolution can be obtained. In step 210, the processed data is compared with the reference data.

  As mentioned above, although embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that various modifications are possible.

  For example, the present invention can be used not only to identify a leak location in a transport pipeline, but also to identify a fault location in a leak detection cable. Further, in the present specification, a leakage detection apparatus that uses a coaxial cable having porous PTFE having a relative dielectric constant ε of 1.5 as a detection cable has been described. However, a detection cable having porous PTFE having a different dielectric constant or a detection cable using another resin as an insulating material can also be used as the detection cable. Furthermore, in this specification, the leak detection pulse signal is generated by the signal of the pulse generation unit 31 that generates the sampling signal, but can also be generated by another pulse generator.

DESCRIPTION OF SYMBOLS 1, 3 Leak detection apparatus 2, 4 Signal processing part 11 Detection sensor 13 Terminator 15 Dummy cable 21 CPU
31 Pulse Generation Unit 33 Pulse Width Control Unit 41 I / O Unit 51 DAC
53 gain amplifier 61 ADC
71 Data I / O
81 Delay amount selection unit 100 Liquid transport pipeline 111 Input device 113 Display device 115 Storage device

Claims (6)

An apparatus for detecting liquid leakage from a liquid transport pipeline by detecting a reflected wave of a leakage detection pulse signal incident on a leakage detection cable,
Leakage detection cable that is laid along the pipeline and has a characteristic impedance that changes due to penetration of liquid leaked from the pipeline;
A leak detection pulse signal generation unit for generating a leak detection pulse signal incident on the leak detection cable;
A storage unit for storing data representing a correlation between the propagation distance of the reflected wave and the attenuation of the reflected wave;
A gain amplifier that amplifies the reflected wave with respect to the leakage detection pulse signal in synchronization with a sampling signal repeated at a predetermined sampling period, and an amplification factor variable that changes an amplification factor of the reflected wave based on the data A gain amplifier,
An A / D converter that samples the amplified reflected wave for one leak detection pulse signal a plurality of times in synchronization with the sampling signal, and converts the sampled reflected wave into a digital signal;
A device characterized by comprising:   2. The delay amount selection unit capable of delaying the sampling signal by N delay amounts having different delay amounts by 1 / N of the sampling period, wherein the N is an integer. The device described in 1.   The apparatus according to claim 1, wherein the digital signal and a given reference value are compared to determine whether there is leakage from the pipeline or the like. A method for detecting liquid leakage from a liquid transport pipeline, etc.
Inputting a leak detection pulse signal to the leak detection cable;
Amplifying a reflected wave of the leakage detection pulse signal in synchronization with a sampling signal having a predetermined sampling period;
Sampling the amplified reflected wave in synchronization with the sampling signal and converting the sampled reflected wave into a digital signal;
A method characterized by comprising:   The sampling period of the step of amplifying a reflected wave and the step of converting the amplified reflected wave to a digital signal is shifted by N timings with different delay amounts by 1 / N of the sampling period, The method of claim 4, wherein each method is performed, wherein N is an integer.   The method according to claim 4, further comprising a step of comparing the digital signal with a given reference value to determine whether there is leakage from the pipeline or the like.

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