CN114607944A - A kind of natural gas pipeline leakage monitoring device and method - Google Patents

Abstract

The invention belongs to the technical field of natural gas pipeline leakage detection, and discloses a natural gas pipeline leakage monitoring device and method, comprising a sensing pipeline, the sensing pipeline is laid parallel to the natural gas pipeline along the top of the underground natural gas pipeline, and the gas leaked in the natural gas pipeline can enter In the sensing pipe, there are multiple gas detection units in the sensing pipe. The end of the sensing pipe extends out of the ground and is connected to the air pump. The standard optical fiber extends from the ground into the soil to connect each gas detection unit and then extends from the ground to connect the signal. The analysis unit, the standard optical fiber transmits the laser beam to the gas detection unit, and the signal analysis unit analyzes the laser signal intensity of the gas detection unit to determine whether there is a methane leakage. The invention can provide higher detection accuracy and sensitivity for gas leakage with slight leakage, early warning maintenance, and reduce accident probability. It has the advantages of small size, low cost, low power consumption, high stability and reliability.

Description

A kind of natural gas pipeline leakage monitoring device and method

technical field

The invention belongs to the technical field of natural gas pipeline leakage detection, and in particular relates to a natural gas pipeline leakage monitoring device and method.

Background technique

Pipeline transportation is the most common way of natural gas transportation, which has the advantages of safety and reliability, low energy consumption, no pollution and basically not affected by climate. Long-distance natural gas pipelines often pass through areas with complex terrain such as rivers, mountains, and goafs. The pipelines are easily damaged by third parties and lead to pipeline leakage. If the exposed pipelines or leaks cannot be found in time and corresponding measures are taken, certain economic losses will be caused to the pipeline operators, and serious accidents such as casualties may be caused.

Pipe leakage usually causes changes in the characteristics of the internal pressure, flow, and sound waves of the pipeline. Thus, pipeline leaks can be detected by monitoring changes in the relevant quantities. In the past few decades, researchers have proposed a variety of technologies for detecting natural gas pipeline leakage, commonly used acoustic sensing technology, thermal imaging technology, distributed optical fiber sensing technology, etc. In addition, Chinese patent CN105299477A discloses an oil and gas pipeline leakage monitoring system, including a monitoring center, multiple monitoring sub-stations, optical fiber sensing analyzers, lasers, sensing optical cables and distributor gas sensing arrays, which can effectively monitor Oil and gas leakage phenomenon, timely location of leakage locations, reduce the trouble of manual inspection, reduce losses and hazards.

Acoustic sensing technology uses the acoustic characteristics of the leak source and the propagation law of sound waves in the pipeline to detect the pipeline, but a slight leak will generate a small sound signal, and the system cannot detect the background noise, resulting in many false alarms in the system . Pipeline leak detection based on infrared thermal imaging technology is difficult to distinguish between normal pressure waves and leaks. This method is only effective for large-scale instantaneous leaks, which easily lead to false alarms. There are still many problems in multi-point detection, anti-environmental interference, improved positioning accuracy and automatic identification of vibration source types using distributed optical fiber acoustic sensing technology.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a natural gas pipeline leakage monitoring device and method to solve the above technical problems.

In order to solve the above-mentioned technical problems, the specific technical scheme of a natural gas pipeline leakage monitoring device and method of the present invention is as follows:

A natural gas pipeline leakage monitoring device, comprising a sensing pipeline, the sensing pipeline is laid parallel to the natural gas pipeline along the top of the underground natural gas pipeline, the sensing pipeline is a gas permeable, but impermeable liquid material, and the natural gas pipeline leaks The gas can enter the sensing pipeline, and the sensing pipeline has a plurality of gas detection units. The gas detection units are nested and sealed with the sensing pipeline. The gas detection units are used to detect the collected gas in the sensing pipeline. To the signal of leaking gas, the end of the sensing pipe extends out of the ground and is connected to an air pump, the air pump is used to transport the gas in the sensing pipe to the gas detection unit, and the standard optical fiber extends from the ground into the soil to connect each After each gas detection unit is connected to the signal analysis unit, the standard optical fiber transmits the laser beam to the gas detection unit, and the signal analysis unit analyzes the laser signal intensity of the gas detection unit to determine whether there is a methane leak.

Further, the sensing pipeline is laid parallel to the natural gas pipeline along 10-20 cm above the natural gas pipeline.

Further, the sensing pipeline includes a polyvinyl chloride pipe with a perforated array, and the polyvinyl chloride pipe is covered with a layer of ethylene-vinyl acetate film, and the ethylene-vinyl acetate film is permeable to gas, but impermeable. A liquid, ethylene-vinyl acetate film wrapped around a polyethylene braid.

Further, the interval between each of the gas detection units is 5-10m.

Further, it includes a current controller, a temperature controller, a distributed feedback laser and a bismuth-doped fiber power amplifier, the current controller and the temperature controller are connected to a distributed feedback laser, and the distributed feedback laser is connected to a bismuth-doped fiber power amplifier , the bismuth-doped fiber power amplifier is connected to a standard fiber; the current controller is used to control the output current of the distributed feedback laser; the temperature controller is used to control the operating temperature of the distributed feedback laser; the distributed feedback laser is used for A laser beam is emitted; the bismuth-doped fiber power amplifier is used to amplify the output power of the distributed feedback laser.

Further, the gas detection unit includes a first fiber coupler, a hollow-core photonic bandgap fiber, and a second fiber coupler; the standard fiber is connected to the first fiber coupler, and the first fiber coupler is connected to the hollow core A photonic bandgap fiber, the hollow-core photonic bandgap fiber is connected to a second fiber coupler, the second fiber coupler is connected to the next standard fiber, and the next standard fiber is connected to the next gas detection unit.

Further, the signal analysis unit includes a photodetector, a lock-in amplifier and a data processing center, the standard optical fiber is connected to the photodetector after extending out of the ground, the photodetector is connected to the lock-in amplifier, and the lock-in amplifier is connected to the a data processing center; the photodetector outputs a corresponding electrical signal according to the intensity of the detected laser signal, and the lock-in amplifier is used to detect the second harmonic signal in the electrical signal output by the photodetector; the data processing center It is used for data processing and display, including displaying whether there is methane leakage, the concentration of methane leakage, and calculating the leakage position according to the response time of the second harmonic signal.

Further, the hollow-core photonic bandgap optical fiber is 1 m long, and a plurality of air holes are opened on one side.

The invention also discloses a method for monitoring natural gas pipeline leakage, comprising the following steps:

Step 1: Connect the air pump to the sensing pipeline, turn on the air pump to transport the gas in the sensing pipeline from left to right;

Step 2: Load a combined modulation signal into the current controller, and then set the temperature controller to 27-30°C to control the distributed feedback laser to output the laser beam;

Step 3: connect the distributed feedback laser to the bismuth-doped fiber power amplifier, and amplify the output power of the distributed feedback laser to 160-200mW;

Step 4: then inject the laser light after passing through the bismuth-doped fiber power amplifier into the gas detection unit through the standard fiber, so that the laser beam of the distributed feedback laser enters the hollow-core photonic bandgap fiber 9;

Step 5: When the natural gas pipeline leaks, the sensing pipeline collects the leaked methane gas into the sensing pipeline and starts to transport it from left to right;

Step 6: When the leaked methane gas enters the hollow-core photonic bandgap fiber, according to the Lambert-Beer law, the laser beam of the standard fiber-delivered distributed feedback laser contacts the methane gas inside the hollow-core photonic bandgap fiber and is absorbed by the methane gas. Absorption, the laser intensity becomes weak, and the photodetector outputs a corresponding electrical signal according to the detected laser signal intensity. The second harmonic signal in the electrical signal output by the detector, and the concentration of the leaked gas is determined according to the strength of the second harmonic signal;

Step 7: Finally, the data processing center displays whether there is leakage according to the second harmonic signal detected by the lock-in amplifier, inverts the methane leakage concentration according to the amplitude of the second harmonic signal, and calculates the leakage according to the response time of the second harmonic signal. Location.

Further, the modulation signal of the step includes an amplitude of 800mV, a high-frequency sinusoidal signal of 5kHz and a sawtooth wave scan signal of 10Hz, and the control distributed feedback laser outputs a laser beam with a center wavelength of 1650nm, and the power is 3-5mw. , the line width is less than 10MHz.

A natural gas pipeline leakage monitoring device and method of the present invention has the following advantages: the invention utilizes the advantages of hollow-core optical fiber gas sensing to provide a natural gas pipeline leakage monitoring method of hollow-core photonic bandgap optical fiber gas sensing, which utilizes the advantages of hollow-core optical fiber gas sensing. The hollow-core photonic bandgap optical fiber is a gas absorption cell to absorb the trace leakage gas collected in the sensing pipeline, and then detects the absorption signal of the methane gas leaked from the natural gas pipeline through the photoelectric detector, so as to determine the pipeline leakage position in time, which can simplify the operation and While reducing costs, it can provide higher detection accuracy and sensitivity for gas leaks with slight leaks, early warning maintenance, and reduce the probability of accidents. Compared with the traditional distributed optical fiber detection method, the natural gas pipeline leakage detection method proposed by the invention has smaller volume, lower cost and lower power consumption, improves the stability and reliability of the instrument, and also reduces the maintenance cost of the equipment.

Description of drawings

1 is a schematic structural diagram of a natural gas pipeline leakage monitoring device of the present invention;

Description of symbols in the figure: 1. Air pump; 2. Bi-doped fiber power amplifier; 3. Distributed feedback laser; 4. Current controller; 5. Temperature controller; 6. Gas detection unit; 7. Standard fiber; 8. 1st fiber coupler; 9. Hollow-core photonic bandgap fiber; 10. Second fiber coupler; 11. Photodetector; 12. Lock-in amplifier; 13. Data processing center; 14. Sensing pipeline; 15. Leak point; 16. Natural gas pipeline; 17. Underground soil.

Detailed ways

In order to better understand the purpose, structure and function of the present invention, a natural gas pipeline leakage monitoring device and method of the present invention will be described in further detail below with reference to the accompanying drawings.

As shown in FIG. 1 , the natural gas pipeline 16 is buried in the underground soil 17 . A natural gas pipeline leakage monitoring device of the present invention includes a sensing pipeline 14 , and the sensing pipeline 14 is parallel to the natural gas pipeline 10-20 cm above the natural gas pipeline 16 . 16 Lay, the sensing pipe 14 consists of three parts, including a polyvinyl chloride pipe with a perforated array covered with a thin ethylene-vinyl acetate membrane that is gas permeable but impermeable Liquid, finally externally protected with a polyethylene braid. The gas permeable structure of the sensing pipe 14 can allow the gas leaked from the natural gas pipe to easily enter the interior of the sensing pipe. The end of the sensing pipe 14 protrudes from the ground and is connected to an air pump 1, which is used to transport the gas in the sensing pipe from left to right. There are a plurality of gas detection units 6 in the sensing pipe 14. The gas detection units 6 are nested and sealed with the sensing pipe 14. The gas detection units 6 are used to detect the signal of the leaked gas collected in the sensing pipe 14. Each gas The interval between the detection units 6 is about 5-10m. The current controller 4 and the temperature controller 5 are connected to the distributed feedback laser 3, the distributed feedback laser 3 is connected to the bismuth-doped fiber power amplifier 2, the bismuth-doped fiber power amplifier 2 is connected to the standard optical fiber 7, and the standard optical fiber 7 extends from the ground into the soil to connect each After the gas detection unit 6 is extended from the ground, the signal analysis unit is connected. The signal analysis unit includes a photodetector 11 , a lock-in amplifier 12 and a data processing center 13 . The standard optical fiber 7 is connected to the photodetector 11 after extending out of the ground. The photodetector 11 is connected to the lock-in amplifier 12 , and the lock-in amplifier 12 is connected to the data processing center 13 . A standard optical fiber 7 is used to export the laser beam of the distributed feedback laser 3 . The current controller 4 is used to control the output current of the distributed feedback laser 3 . The temperature controller 5 is used to control the working temperature of the distributed feedback laser 3 . The distributed feedback laser 3 is used for emitting a laser beam. The bismuth-doped fiber power amplifier 2 is used to amplify the output power of the distributed feedback laser 3 . The photodetector 11 outputs a corresponding electrical signal according to the detected intensity of the laser signal, and the lock-in amplifier 12 is used to detect the second harmonic signal in the electrical signal output by the photodetector 11 . The data processing center 13 is a computer for data processing and display, including displaying whether there is a methane leakage, the concentration of methane leakage, and calculating the leakage position according to the response time.

When the natural gas pipeline 16 leaks, the sensing pipeline 14 absorbs methane gas, and under the action of the suction pump 1 , the gas starts to be transported from left to right in the sensing pipeline 14 . The leaked methane gas enters the gas detection unit 6, and the laser light transmitted from the standard optical fiber 7 is absorbed by the leaked gas and then weakens in intensity. The photodetector 11 outputs a corresponding electrical signal (including various noises and The lock-in amplifier 12 detects the second harmonic signal in the electrical signal output by the photodetector 11, and finally obtains the methane leakage concentration through the data processing center 13 and responds according to the second harmonic signal. Calculate the leak location.

Specifically, the gas detection unit 6 includes a first fiber coupler 8 , a hollow-core photonic bandgap fiber 9 and a second fiber coupler 10 . The standard fiber 7 is connected to the first fiber coupler 8, the first fiber coupler 8 is connected to the hollow-core photonic bandgap fiber 9, the hollow-core photonic bandgap fiber 9 is connected to the second fiber coupler 10, and the second fiber coupler 10 is connected The next segment of standard optical fiber 7 is connected to the next gas detection unit 6 . The hollow-core photonic bandgap fiber 9 is 1 m long, and has 10 air holes with tiny diameters on one side, so that the gas can enter the hollow-core photonic bandgap fiber 9 more fully.

The distributed feedback laser adopts NP-ICL-1650-T066 produced by Nanoplus Company, the central output wavelength is 1650nm, the power is 3-5mw, and the line width is less than 10MHz.

The photodetector adopts the MCT photodetector produced by VIGO system.

The lock-in amplifier adopts SR830 produced by STANFORD Company.

The steps of the detection method of this device are:

Step 1: Connect the air pump 1 to the sensing pipe 14, turn on the air pump 1 to transport the gas in the sensing pipe 14 from left to right.

Step 2: Load a combined modulation signal, including a high-frequency sine signal with an amplitude of 800mV, a 5kHz sine wave and a 10Hz sawtooth sweep signal, into the current controller 4, and then set the temperature controller 5 to 27-30°C, control The distributed feedback laser 3 outputs a laser beam with a center wavelength of 1650 nm, the power is greater than 3-5 mw, and the line width is less than 10 MHz.

Step 3: Connect the distributed feedback laser 3 to the bismuth-doped fiber power amplifier 2, and amplify the output power of the distributed feedback laser 3 to 160-200 mW.

Step 4: Then, the laser light passing through the bismuth-doped fiber power amplifier 2 is injected into the gas detection unit 6 through the standard fiber 7, so that the laser beam of the distributed feedback laser 3 enters the hollow-core photonic bandgap fiber 9.

Step 5: When the natural gas pipeline leakage point 15 leaks, the sensing pipeline 14 collects the leaked methane gas into the sensing pipeline 14 and starts to transport it from left to right.

Step 6: When the leaked methane gas enters the hollow-core photonic bandgap fiber 9, according to the Lambert-Beer law, the standard fiber 7 transmits the laser beam of the distributed feedback laser 3 and the methane inside the hollow-core photonic bandgap fiber 9 The gas contacts and is absorbed, and the laser intensity becomes weak. At this time, the photodetector 11 outputs a corresponding electrical signal (including a mixture of various noises and various harmonic signals) according to the detected laser signal intensity. The second harmonic term is proportional to the concentration of the leaking gas. The lock-in amplifier 12 detects the second harmonic signal in the electrical signal, and determines the concentration of the leaking gas according to the strength of the second harmonic signal.

Step 7: Finally, the data processing center 13 can display whether there is leakage according to the second harmonic signal detected by the lock-in amplifier 12, and invert the methane leakage concentration according to the amplitude of the second harmonic signal and respond according to the second harmonic signal. Time to calculate leak location.

It can be understood that the present invention is described by some embodiments, and those skilled in the art know that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, in the teachings of this invention, these features and embodiments may be modified to adapt a particular situation and material without departing from the spirit and scope of the invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present application fall within the protection scope of the present invention.

Claims (10)

1. A natural gas pipeline leakage monitoring device, comprising a sensing pipeline (14), the sensing pipeline (14) being laid parallel to the natural gas pipeline (16) along the top of the underground natural gas pipeline (16), and the sensing pipeline (16). 14) is a gas permeable, but impermeable liquid material, the gas leaked in the natural gas pipeline (16) can enter the sensing pipeline (14), characterized in that the sensing pipeline (14) has a plurality of gas detectors A unit (6), the gas detection unit (6) is nested and sealed with the sensing pipe (14), and the gas detection unit (6) is used for detecting the signal of leaking gas collected in the sensing pipe (14) , the end of the sensing pipe (14) protrudes from the ground and is connected to an air pump (1), the air pump (1) is used to transport the gas in the sensing pipe (14) to the gas detection unit (6) , the standard optical fiber (7) extends from the ground into the soil to connect each gas detection unit (6) and then extends from the ground to connect the signal analysis unit, the standard optical fiber (7) transmits the laser beam to the gas detection unit (6), the signal The analysis unit analyzes the laser signal intensity of the gas detection unit (6) to determine whether there is a methane leak. 2 . The natural gas pipeline leakage monitoring device according to claim 1 , wherein the sensing pipeline ( 14 ) is laid parallel to the natural gas pipeline ( 16 ) 10-20 cm above the natural gas pipeline ( 16 ). 3 . 3. The natural gas pipeline leakage monitoring device according to claim 1, wherein the sensing pipeline (14) comprises a polyvinyl chloride pipe with an array of holes, and the polyvinyl chloride pipe is covered with a layer of ethylene-acetic acid Vinyl ester film, the ethylene-vinyl acetate film is gas permeable but liquid impermeable, the ethylene-vinyl acetate film is wrapped with polyethylene braid on the outside. 4 . The natural gas pipeline leakage monitoring device according to claim 1 , wherein the interval between each of the gas detection units ( 6 ) is 5-10 m. 5 . 5. The natural gas pipeline leakage monitoring device according to claim 1, characterized in that it comprises a current controller (4), a temperature controller (5), a distributed feedback laser (3) and a bismuth-doped fiber power amplifier (2) , the current controller (4) and the temperature controller (5) are connected to a distributed feedback laser (3), the distributed feedback laser (3) is connected to a bismuth-doped fiber power amplifier (2), and the bismuth-doped fiber power The amplifier (2) is connected to a standard optical fiber (7); the current controller (4) is used to control the output current of the distributed feedback laser (3); the temperature controller (5) is used to control the distributed feedback laser (3) ); the distributed feedback laser (3) is used for emitting a laser beam; the bismuth-doped fiber power amplifier (2) is used for amplifying the output power of the distributed feedback laser (3). 6. The natural gas pipeline leakage monitoring device according to claim 1, wherein the gas detection unit (6) comprises a first fiber coupler (8), a hollow-core photonic bandgap fiber (9) and a second fiber An optical fiber coupler (10); the standard optical fiber (7) is connected to a first optical fiber coupler (8), and the first optical fiber coupler (8) is connected to a hollow-core photonic bandgap optical fiber (9), the hollow-core optical fiber (9) The photonic bandgap optical fiber (9) is connected to a second optical fiber coupler (10), the second optical fiber coupler (10) is connected to the next standard optical fiber (7), and the next standard optical fiber (7) is connected to the next gas detection unit (6). 7. The natural gas pipeline leakage monitoring device according to claim 1, wherein the signal analysis unit comprises a photodetector (11), a lock-in amplifier (12) and a data processing center (13), the standard optical fiber (7) Connect the photodetector (11) after sticking out of the ground, the photodetector (11) is connected to the lock-in amplifier (12), and the lock-in amplifier (12) is connected to the data processing center (13); the photoelectric The detector (11) outputs a corresponding electrical signal according to the detected intensity of the laser signal, and the lock-in amplifier (12) is used to detect the second harmonic signal in the electrical signal output by the photodetector (11); the data The processing center (13) is used for data processing and display, including displaying whether there is methane leakage, the concentration of methane leakage, and calculating the leakage position according to the response time of the second harmonic signal. 8 . The natural gas pipeline leakage monitoring device according to claim 6 , wherein the hollow-core photonic bandgap optical fiber ( 9 ) is 1 m long and has a plurality of air holes on one side. 9 . 9. A method for monitoring natural gas pipeline leakage by utilizing the natural gas pipeline leakage monitoring device according to any one of claims 1-8, characterized in that, comprising the steps of: Step 1: Connect the air pump (1) to the sensing pipe (14), turn on the air pump (1) to transport the gas in the sensing pipe (14) from left to right; Step 2: Load a combined modulation signal into the current controller 4, then set the temperature controller (5) to 27-30°C, and control the distributed feedback laser (3) to output the laser beam; Step 3: connect the distributed feedback laser (3) to the bismuth-doped fiber power amplifier (2), and amplify the output power of the distributed feedback laser (3) to 160-200mW; Step 4: Then, the laser light passing through the bismuth-doped fiber power amplifier (2) is injected into the gas detection unit (6) through the standard fiber (7), so that the laser beam of the distributed feedback laser (3) enters the hollow-core photonic band. Inside the gap fiber (9); Step 5: When the natural gas pipeline leaks, the sensing pipeline (14) collects the leaked methane gas into the sensing pipeline (14) and starts to transport it from left to right; Step 6: When the leaked methane gas enters the hollow-core photonic bandgap fiber (9), according to the Lambert-Beer law, the standard fiber (7) transmits the laser beam of the distributed feedback laser 3 and the hollow-core photonic bandgap fiber (9) The internal methane gas contacts and is absorbed, and the laser intensity becomes weak. At this time, the photodetector (11) outputs a corresponding electrical signal according to the detected laser signal intensity, wherein the second harmonic term in the electrical signal is related to the leakage. The concentration of the gas is proportional, the lock-in amplifier (12) detects the second harmonic signal in the electrical signal output by the photodetector (11), and determines the concentration of the leaked gas according to the strength of the second harmonic signal; Step 7: Finally, the data processing center (13) displays whether there is leakage according to the second harmonic signal detected by the lock-in amplifier (12), inverts the methane leakage concentration according to the amplitude of the second harmonic signal, and according to the second harmonic signal The wave signal response time calculates the leak location. 10. The method for monitoring natural gas pipeline leakage according to claim 9, wherein the modulated signal in step 2 comprises an amplitude of 800mV, a high-frequency sinusoidal signal of 5kHz and a sawtooth sweep signal of 10Hz, and the control The distributed feedback laser (3) outputs a laser beam with a center wavelength of 1650nm, a power of 3-5mw, and a line width of less than 10MHz.

Images