A long-distance buried double-wall pipe inner pipe leakage detection device and detection method

Abstract

The present invention belongs to the technical field of pipeline leakage detection and positioning, and specifically relates to a long-distance buried double-wall pipe inner pipe leakage detection device and a detection method thereof, comprising: a flow supply control device A, an interlayer pressure-charging and pressure-maintaining device B, a data acquisition and analysis device C, a pipeline to be inspected, a plurality of transmission cables and a plurality of pressure-bearing hoses; the flow supply control device A is connected to the data acquisition and analysis device C through the transmission cable; one end of the pipeline to be inspected is connected to the flow supply control device A, and the other end of the pipeline to be inspected is connected to the data acquisition and analysis device C; an interlayer pressure-charging and pressure-maintaining device B is provided at the interlayer of the pipeline to be inspected.

Description

Technical Field

[0001] The invention belongs to the technical field of pipeline leakage detection and positioning, and in particular relates to a long-distance buried double-wall pipe inner pipe leakage detection device and a detection method thereof. Background Art

[0002] The hydrogen transport pipeline of a nuclear power plant is a double-wall pipeline. The hydrogen concentration in the inner and outer pipes of the pipeline is found to be continuously increasing. Since hydrogen is a dangerous flammable gas with low ignition energy, wide explosion limit and fast burning rate, if hydrogen leaks from the inner pipe of the double-wall transport pipeline, it will accumulate in the inner and outer pipes, increasing the risk of fire. Therefore, it is particularly urgent to locate the leak point of the inner pipe of the double-wall pipeline for hydrogen transportation.

[0003] At present, there are few mature methods for locating leaks in double-walled pipelines for long-distance underground hydrogen transportation in the power industry. The oil and gas transportation industry mainly pre-installs leak detection devices during the pipeline installation phase and requires regular weak current to carry out leak detection. In addition, double-walled pipelines for hydrogen transportation are not pre-arranged with leak detection devices during the installation phase, and due to the flammable and explosive properties of hydrogen, the power-on detection method is not suitable for locating leaks in hydrogen pipelines. Therefore, it is necessary to study and design a safe and reliable leak locating device to locate the leak position of the inner pipe of a double-walled pipeline for long-distance underground hydrogen transportation to solve the above technical problems. Summary of the invention

[0004] The purpose of the present invention is to design a long-distance buried double-wall pipe inner pipe leakage detection device and detection method, which are used to solve the technical problems in the prior art that the hydrogen leakage point of the inner pipe of the double-wall pipeline for hydrogen transportation is difficult to locate and the leakage detection method has a high risk factor.

[0005] The technical solution of the present invention:

[0006] A long-distance buried double-wall pipe inner pipe leakage detection device, comprising: a flow supply control device A, an interlayer pressure-charging and pressure-maintaining device B, a data acquisition and analysis device C, a pipeline to be inspected, a plurality of transmission cables and a plurality of pressure-bearing hoses; the flow supply control device A is connected to the data acquisition and analysis device C through the transmission cable; one end of the pipeline to be inspected is connected to the flow supply control device A, and the other end of the pipeline to be inspected is connected to the data acquisition and analysis device C; an interlayer pressure-charging and pressure-maintaining device B is provided at the interlayer of the pipeline to be inspected.

[0007] The flow control device A comprises: a compressed air source A, a pressure regulating tank, a pressure gauge, a flow regulating valve, a switch valve A, a switch valve B, a flow sensor, a dew point thermometer, a temperature sensor, a standard leak hole and a connecting flange and a plurality of pressure-bearing hoses;

[0008] The compressed air source is connected to one end of the pressure-surge tank through a pressure hose, and the other end of the pressure-surge tank is connected in series with a pressure gauge, a flow regulating valve, a switch valve A, a flow sensor, a dew point thermometer, a temperature sensor and a connecting flange through a pressure hose;

[0009] One end of the switch valve B is arranged on the pressure hose between the flow regulating valve and the switch valve A, and the other end of the switch valve B is arranged on the pressure hose between the flow sensor and the dew point thermometer; a standard leak hole is also arranged on the pressure hose between the temperature sensor and the connecting flange;

[0010] The connecting flange is connected to one end of the inspected pipeline.

[0011] The interlayer pressure-charging and pressure-maintaining device B comprises: a helium gas source, a compressed air gas source B, a flow meter B, a flow meter C, a mixed pressure-stabilizing tank, a helium concentration measuring instrument, an absolute pressure gauge A, a pressure sensor, an absolute pressure gauge B, a switch valve C, a switch valve D, a vacuum pump and a plurality of pressure-bearing hoses; the mixed pressure-stabilizing tank is respectively connected to the helium gas source and the compressed air gas source B through the pressure-bearing hoses, the mixed pressure-stabilizing tank is also connected to the interlayer of the inspected pipeline through the pressure-bearing hoses, and the absolute pressure gauge A, the switch valve C, the pressure sensor, the switch valve D and the absolute pressure gauge B are sequentially arranged on the pressure-bearing hose between the mixed pressure-stabilizing tank and the interlayer of the inspected pipeline; the switch valve D is connected to the vacuum pump;

[0012] A flow meter B is also provided on the pressure hose between the helium gas source and the mixing pressure-stabilizing tank; a flow meter C is also provided on the pressure hose between the compressed air gas source B and the mixing pressure-stabilizing tank.

[0013] The data acquisition and analysis device C also includes: a data acquisition computer, a helium mass spectrometer leak detector, a mass spectrometer suction gun, a connecting flange and a current / digital converter; the current / digital converter is connected to the data acquisition computer and the helium mass spectrometer leak detector respectively through a transmission cable, and the helium mass spectrometer leak detector is also connected to the mass spectrometer suction gun through a transmission cable; the mass spectrometer suction gun is provided with a connecting flange; the connecting flange is connected to the other end of the pipeline to be inspected.

[0014] The current / digital converter is also connected to the flow sensor of the flow supply control device A through a transmission cable, and the current / digital converter is also connected to the temperature sensor of the flow supply control device A through a transmission cable.

[0015] The pressure hoses are all hard pressure hoses, and the pressure pipes are all equipped with instrument pressure pipe joints.

[0016] The pressure stabilizing tank and the mixed pressure stabilizing tank are both provided with pressure-bearing hose connectors.

[0017] A detection and positioning method for the long-distance buried double-wall pipe inner pipe leakage detection device as described above comprises the following steps:

[0018] Step 1: Connect the flow supply control device A and the data acquisition and analysis device C to the pipeline to be inspected through the connecting flange A and the connecting flange B; use the transmission cable to connect the current / digital converter, the data acquisition computer and the helium mass spectrometer leak detector and supply power to the current / digital converter, the data acquisition computer and the helium mass spectrometer leak detector respectively, and place the mass spectrometer suction gun at the outlet end of the inner pipe of the pipeline to be inspected;

[0019] Step 2: Initial inspection of the inner pipe: Open the compressed air source A, close the switch valve A and the connecting flange, open the switch valve B and the flow control valve, and fill the inner pipe of the inspected pipeline with compressed air. The compressed air pressure is greater than 0.1MPa. At this time, the interlayer of the inspected pipeline is kept at atmospheric pressure. After stabilization for four hours, measure the leakage rate of the inner pipe of the inspected pipeline; select a suitable reference leak hole and install it at the standard leak hole position;

[0020] Step 3: Fill the interlayer of the tested pipe with helium: close the switch valve, open the switch valve, start the vacuum pump to evacuate the interlayer of the tested pipe; stop the vacuum pump, open the switch valve, close the switch valve, open the helium cylinder and the compressed air cylinder, and fill the interlayer with a certain concentration of helium and air mixture; close the switch valve after filling to a certain pressure;

[0021] Step 4: Detection: Open the switch valve A and close the switch valve B, and adjust the air flow in the inner tube to V through the flow transmitter. 1 After the air flow rate is stable and the helium mass spectrometer leak detector signal is stable, adjust the flow control valve to adjust the air flow rate to V 2 If there is a leak, the helium concentration curve on the helium mass spectrometer leak detector and the data acquisition computer will show obvious mutations. The number of mutations represents the number of leaks. The data acquisition computer will calculate the time t between the concentration change moment of the helium mass spectrometer leak detector and the last concentration change moment, the air temperature T, the pipeline cross-sectional area S, and the pipeline flow rate V. 2 The distance between the leak point and the mass spectrometer leak detector is calculated by the following formula (1):

[0022]

[0023] Among them, 273 is a fixed parameter value, that is, the Kelvin temperature corresponding to 0°C.

[0024] Beneficial effects of the present invention:

[0025] According to the industry's many years of helium leak detection experience and through multiple test bench simulation tests, the present invention has designed a long-distance double-wall pipe inner pipe leak point locating device based on the helium leak detection method. The flange positions at both ends of the pipeline inlet and outlet above the ground are used as the detection interface to implement the inner pipe leak point locating of the buried double-wall pipeline, and determine the number and positions of the inner pipe leak points of the buried double-wall pipeline.

[0026] (1) The device of the invention provides a long-distance double-walled pipe inner pipe leak detection function based on the principle of correlation between leak rate and velocity, which can detect and verify whether the pipeline has leaks and determine the number of leaks. Due to the use of helium leak detection method, it has a high leak point identification sensitivity;

[0027] (2) The invention provides a long-distance double-walled pipe inner pipe leak location function, which can accurately locate the position of the double-walled pipe inner pipe leak;

[0028] (3) The device of the invention sets a reference leak hole in a section of the pipeline, and effectively reduces the error caused by the reaction time of the leak detector and the reaction time of the sniffer gun through relative time recording;

[0029] (4) The device only needs to be installed at both ends of the double-walled pipeline to detect the number and precise location of leaks in the entire pipe section. No operation is required on the intermediate pipeline. It can detect and locate leaks in the inner pipe of long-distance double-walled pipes such as submarine tunnels, oil and gas pipelines, high-altitude pipelines, and underground pipelines.

[0030] (5) The leak point locating device uses helium and compressed air as the working medium. It is safe and reliable and can be used for leak detection in high-risk places such as flammable, explosive, and high-temperature places. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of the structure of a long-distance buried double-wall pipe inner pipe leakage detection device designed for the present invention;

[0032] Among them: 1. Compressed air source A, 2. Pressure regulating tank, 3. Pressure gauge, 4. Flow regulating valve, 5. Switch valve A, 6. Switch valve B, 7. Flow transmitter, 8. Leak point thermometer, 9. Temperature sensor, 10. Standard leak hole, 11. Connection flange A, 12. Helium source, 13. Compressed air source B, 14. Flow meter A, 15. Flow meter B, 16. Helium concentration meter, 17. Mixing pressure regulating tank, 18. Absolute pressure gauge A, 19. Pressure sensor 20. Absolute pressure gauge B, 21. Switch valve C, 22. Switch valve D, 23. Vacuum pump, 24. Connection flange, 25. Helium mass spectrometer leak detector, 26. Data acquisition computer, 27. Current / digital converter, 28. Inspected pipeline, 29-Mass spectrometer suction gun. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0034] The device of the present invention is composed of a flow supply control device A, an interlayer pressure charging / maintaining device B, and a data acquisition and analysis device C. When the interlayer environment of the inspected pipeline 28 remains unchanged, the change in the flow rate in the inspected pipeline 28 will cause a corresponding change in the indication of the helium mass spectrometer leak detector. The device of the present invention uses this principle to detect and calculate the leak point distance, the mass spectrometer suction gun position and the number of leak points. The specific structure of the device is as follows:

[0035] A long-distance buried double-wall pipe inner pipe leakage detection device, comprising: a flow supply control device A, an interlayer pressure-charging and pressure-maintaining device B, a data acquisition and analysis device C, a pipeline to be inspected 28, a plurality of transmission cables and a plurality of pressure-bearing hoses; the flow supply control device A is connected to the data acquisition and analysis device C through the transmission cable; one end of the pipeline to be inspected 28 is connected to the flow supply control device A, and the other end of the pipeline to be inspected 28 is connected to the data acquisition and analysis device C; an interlayer pressure-charging and pressure-maintaining device B is provided at the interlayer of the pipeline to be inspected 28.

[0036] The inspected pipeline 28 is a double-walled hydrogen transport pipeline;

[0037] The flow control device A comprises: a compressed air source A1, a pressure regulating tank 2, a pressure gauge 3, a flow regulating valve 4, a switch valve A5, a switch valve B6, a flow sensor 7, a dew point thermometer 8, a temperature sensor 9, a standard leak hole 10 and a connecting flange 11 and a plurality of pressure-bearing hoses;

[0038] The compressed air source 1 is connected to one end of the pressure stabilizing tank 2 through a pressure hose, and the other end of the pressure stabilizing tank 2 is connected in series with a pressure gauge 3, a flow regulating valve 4, a switch valve A5, a flow sensor 7, a dew point thermometer 8, a temperature sensor 9 and a connecting flange 11 in sequence through a pressure hose;

[0039] One end of the switch valve B6 is arranged on the pressure hose between the flow regulating valve 4 and the switch valve A5, and the other end of the switch valve B6 is arranged on the pressure hose between the flow sensor 7 and the dew point thermometer 8; a standard leak hole 10 is also arranged on the pressure hose between the temperature sensor 9 and the connecting flange 11;

[0040] The connecting flange 11 is also connected to one end of the pipeline 28 to be inspected.

[0041] The flow control device A is used to provide air of various flow rates. The pressure regulating tank provides a gas source with a stable pressure source;

[0042] The switch valve A5 and flow sensor 7 are used to control the input flow into the inspected pipeline; the switch valve B6 is used to switch to the high flow mode to purge the inner pipe of the inspected pipeline 28; the pressure gauge 3, temperature sensor 9 and dew point thermometer 8 are used to collect data and correct the results.

[0043] The interlayer pressure-charging and pressure-maintaining device B comprises: a helium gas source 12, a compressed air gas source B13, a flowmeter B14, a flowmeter C15, a mixing pressure-stabilizing tank 17, a helium concentration measuring instrument 16, an absolute pressure gauge A18, a pressure sensor 19, an absolute pressure gauge B20, a switch valve C21, a switch valve D22, a vacuum pump 23 and a plurality of pressure-bearing hoses; the mixing pressure-stabilizing tank 17 is connected to the helium gas source 12 and the compressed air gas source B13 respectively through the pressure-bearing hose, and the mixing pressure-stabilizing tank 17 is also connected to the interlayer of the inspected pipeline 28 through the pressure-bearing hose, and the absolute pressure gauge A18, the switch valve C21, the pressure sensor 19, the switch valve D22 and the absolute pressure gauge B20 are sequentially arranged on the pressure-bearing hose between the mixing pressure-stabilizing tank 17 and the interlayer of the inspected pipeline 28; the switch valve D22 is also provided with a vacuum pump 23;

[0044] A flow meter B14 is also provided on the pressure hose between the helium gas source 12 and the mixing pressure-stabilizing tank 17 ; a flow meter C15 is also provided on the pressure hose between the compressed air gas source B13 and the mixing pressure-stabilizing tank 17 .

[0045] The interlayer pressure-maintaining / pressurizing device is used to provide and maintain an appropriate concentration of helium to the interlayer of the inspected pipeline 28. The mixing and stabilizing tank 17 provides a space for the introduced gas source to be fully mixed; the flow meter B14 and the flow meter C15 adjust the concentration of helium by controlling the flow rate. The vacuum pump 23 is used to evacuate the space in the inspected pipeline 28. It is ensured that the helium concentration in the space reaches the required value after filling.

[0046] The data acquisition and analysis device C also includes: a data acquisition computer 26, a helium mass spectrometer leak detector 25, a mass spectrometer suction gun 29, a connecting flange 24 and a current / digital converter 27; the current / digital converter 27 is connected to the data acquisition computer 26 and the helium mass spectrometer leak detector 25 respectively through a transmission cable, and the helium mass spectrometer leak detector 25 is also connected to the mass spectrometer suction gun 29 through a transmission cable; the mass spectrometer suction gun 29 is provided with a connecting flange 24; the connecting flange 24 is connected to the other end of the inspected pipeline 28.

[0047] The current / digital converter 27 is also connected to the flow sensor 7 of the flow supply control device A via a transmission cable, and the current / digital converter 27 is also connected to the temperature sensor 9 of the flow supply control device A via a transmission cable.

[0048] The data acquisition computer 26 is used to count and display flow rate, temperature, helium concentration, time and other data information.

[0049] The data acquisition and processing device C is used to detect the concentration of helium, and obtains the precise location of the leakage point by analyzing the data collected from the flow control device A and the interlayer pressure-maintaining and charging device B.

[0050] Among them, the helium mass spectrometer leak detector 25 and the mass spectrometer suction gun 29 are used to detect the concentration change of helium in the inner tube of the inspected pipeline 28, the transmission cable is used to summarize the sensor data of the flow control device A and the interlayer pressure maintaining and charging device B, and the data acquisition computer 26 is used to analyze all the data and finally obtain the precise location of the leakage point.

[0051] The pressure hoses are all hard pressure hoses, and the pressure pipes are all equipped with instrument pressure pipe joints.

[0052] The pressure stabilizing tank 2 and the mixing pressure stabilizing tank 17 are both provided with pressure-bearing hose connectors.

[0053] A detection and positioning method for the long-distance buried double-wall pipe inner pipe leakage detection device as described above comprises the following steps:

[0054] Step 1: Connect the flow supply control device A and the data acquisition and analysis device C to the inspected pipeline 28 through the connecting flange A11 and the connecting flange B24; use a transmission cable to connect the current / digital converter 27, the data acquisition computer 26 and the helium mass spectrometer leak detector 25 and connect the power to the current / digital converter 27, the data acquisition computer 26 and the helium mass spectrometer leak detector 25 respectively, and place the mass spectrometer suction gun 29 at the outlet end of the inner tube of the inspected pipeline 28;

[0055] Step 2, initial inspection of the inner pipe: open the compressed air source A1, close the switch valve A5 and the connecting flange 24, open the switch valve B6 and the flow regulating valve 4, and fill the inner pipe of the inspected pipeline 28 with compressed air, the compressed air pressure is greater than 0.1MPa; at this time, the interlayer of the inspected pipeline 28 maintains atmospheric pressure, and after stabilization for four hours, measure the leakage rate of the inner pipe of the inspected pipeline 28; select a suitable reference leak hole and install it at the position of the standard leak hole 10;

[0056] Step 3: Fill the interlayer of the tested pipe with helium: close the switch valve 21, open the switch valve 22, start the vacuum pump 23 to evacuate the interlayer of the tested pipe; stop the vacuum pump 23, open the switch valve 21, close the switch valve 22, open the helium cylinder 12 and the compressed air cylinder 13, and fill the interlayer with a certain concentration of helium and air; close the switch valve 21 after filling to a certain pressure;

[0057] Step 4: Detection: Open the switch valve A5 and close the switch valve B6, and adjust the air flow rate in the inner tube to V through the flow transmitter 7. 1 After the air flow rate is stable and the helium mass spectrometer leak detector signal is stable, adjust the flow control valve to adjust the air flow rate to V 2If there is a leak, the helium concentration curve on the helium mass spectrometer leak detector 25 and the data acquisition computer 26 shows obvious mutations, and the number of mutations represents the number of leaks. The data acquisition computer 26 calculates the time t between the concentration change moment of the helium mass spectrometer leak detector and the last concentration change moment, the air temperature T, the pipeline cross-sectional area S, and the pipeline flow rate V 2 The distance between the leak point and the mass spectrometer leak detector is calculated by the following formula (1):

[0058]

[0059] Among them, 273 is a fixed parameter value, that is, the Kelvin temperature corresponding to 0°C.

[0060] Test verification

[0061] The device of the present invention was used to carry out a "600m double-wall pipe simulated leak location test" nearly a thousand times in a laboratory for six months. The test results show that the leak location can be fully detected using the device, and the error can be controlled within 1%.

[0062] The device has been used for the first time in the inspection of inner tube leakage of hydrogen double-wall pipes in a nuclear power plant. Combined with the matching detection steps, the inner tube leakage of the 1050-meter-long double-wall pipeline from the hydrogen production station to the conventional island of Unit 4 was located and successfully located. After digging the ground for verification, it was found that the deviation between the located position and the actual leakage point was only 4cm, which greatly reduced the time for eliminating defects and the workload of replacing defective pipelines.

[0063] Effect evaluation

[0064] The present invention can safely, accurately and flexibly detect the location of the leakage point in the double-walled pipe. The device uses helium and air as the inspection medium and has a relatively simple structure. It has the characteristics of high safety, good accuracy and relatively simple implementation. When the device is used, the object to be inspected does not need to be heated or powered on, and can be used in flammable and explosive environments. In addition, the device only needs to be installed at both ends of the pipeline inlet and outlet. It can be used not only for underground pipeline leak detection, but also in long-distance double-walled pipe leak detection work in submarine tunnels, high-altitude pipelines, oil and gas transportation and other fields, and has great engineering application value in the future.

[0065] The present invention is described in detail above with reference to the accompanying drawings and embodiments, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of ordinary technicians in the field without departing from the purpose of the present invention. Any content not described in detail in the present invention can adopt the existing technology.

Claims

1. A long-distance buried double-wall pipe inner pipe leakage detection device, characterized in that: include: A flow supply control device A, an interlayer pressure charging and maintaining device B, a data acquisition and analysis device C, a pipeline to be inspected (28), a plurality of transmission cables and a plurality of pressure-bearing hoses; the flow supply control device A is connected to the data acquisition and analysis device C via the transmission cable; one end of the pipeline to be inspected (28) is connected to the flow supply control device A, and the other end of the pipeline to be inspected (28) is connected to the data acquisition and analysis device C; the interlayer of the pipeline to be inspected (28) is provided with an interlayer pressure charging and maintaining device B; and the pressure-bearing hose is provided with a standard leak hole (10); The flow control device A comprises: a flow transmitter (7) and a pressure-stabilizing tank (2); the pressure-stabilizing tank (2) is connected in series with the flow transmitter (7) via a pressure-bearing hose; Fill the interlayer of the inspected pipeline with helium; The air flow rate in the inner tube of the pressure hose is adjusted to V1 by using the flow transmitter (7); after the air flow rate is stable and the signal of the helium mass spectrometer leak detector is stable, the flow regulating valve is adjusted to adjust the air flow rate to V 2； The data acquisition and analysis device C comprises: a data acquisition computer (26) and a helium mass spectrometer leak detector (25). The data acquisition computer (26) calculates the distance between the leak point and the suction port of the mass spectrometer leak detector according to the time t between the concentration change moment and the last concentration change moment of the helium mass spectrometer leak detector, the air temperature T, the pipeline cross-sectional area S, and the pipeline flow rate V2 parameters. The formula for calculating the distance between the leak point and the suction port of the mass spectrometer leak detector is as follows (1): Among them, 273 is a fixed parameter value, that is, the Kelvin temperature corresponding to 0°C.

2. A long-distance buried double-wall pipe inner pipe leakage detection device as claimed in claim 1, characterized in that: The flow control device A also includes: a compressed air source A (1), a pressure gauge (3), a flow regulating valve (4), a switch valve A (5), a switch valve B (6), a dew point thermometer (8), a temperature sensor (9), a standard leak hole (10), a connecting flange (11) and a plurality of pressure-bearing hoses; The compressed air source (1) is connected to one end of the pressure-suppressing tank (2) via a pressure-bearing hose, and the other end of the pressure-suppressing tank (2) is connected in series with a pressure gauge (3), a flow regulating valve (4), a switch valve A (5), a flow transmitter (7), a dew point thermometer (8), a temperature sensor (9) and a connecting flange (11) in sequence via the pressure-bearing hose; One end of the switch valve B (6) is arranged on the pressure-bearing hose between the flow regulating valve (4) and the switch valve A (5), and the other end of the switch valve B (6) is arranged on the pressure-bearing hose between the flow transmitter (7) and the dew point thermometer (8); The connecting flange (11) is connected to one end of the pipeline (28) to be inspected.

3. A long-distance buried double-wall pipe inner pipe leakage detection device as claimed in claim 2, characterized in that: The interlayer pressure-filling and pressure-maintaining device B comprises: a helium gas source (12), a compressed air gas source B (13), a flow meter B (14), a flow meter C (15), a mixing pressure-stabilizing tank (17), a helium concentration measuring instrument (16), an absolute pressure gauge A (18), a pressure sensor (19), an absolute pressure gauge B (20), a switch valve C (21), a switch valve D (22), a vacuum pump (23) and a plurality of pressure-bearing hoses; the mixing pressure-stabilizing tank (17) is connected to the helium gas source (12) and the compressed air source (13) through the pressure-bearing hoses. The gas source (12) is connected to the compressed air source B (13); the mixing pressure stabilizing tank (17) is also connected to the interlayer of the inspected pipeline (28) through a pressure hose; an absolute pressure gauge A (18), a switch valve C (21), a pressure sensor (19), a switch valve D (22) and an absolute pressure gauge B (20) are sequentially arranged on the pressure hose between the mixing pressure stabilizing tank (17) and the interlayer of the inspected pipeline (28); the switch valve D (22) is connected to a vacuum pump (23); A flow meter B (14) is provided on the pressure hose between the helium gas source (12) and the mixing pressure stabilizing tank (17); a flow meter C (15) is also provided on the pressure hose between the compressed air gas source B (13) and the mixing pressure stabilizing tank (17).

4. A long-distance buried double-walled pipe inner pipe leakage detection device as claimed in claim 3, characterized in that: The data acquisition and analysis device C further comprises: a mass spectrometer suction gun (29), a connecting flange (24) and a current / digital converter (27); the current / digital converter (27) is respectively connected to a data acquisition computer (26) and a helium mass spectrometer leak detector (25) via transmission cables, and the helium mass spectrometer leak detector (25) is also connected to the mass spectrometer suction gun (29) via a transmission cable; the mass spectrometer suction gun (29) is provided with a connecting flange (24); the connecting flange (24) is connected to the other end of the pipeline (28) to be inspected.

5. A long-distance buried double-walled pipe inner pipe leakage detection device as claimed in claim 4, characterized in that: The current / digital converter (27) is also connected to the flow transmitter (7) of the flow supply control device A via a transmission cable, and the current / digital converter (27) is also connected to the temperature sensor (9) of the flow supply control device A via a transmission cable.

6. A long-distance buried double-walled pipe inner pipe leakage detection device as claimed in claim 5, characterized in that: The pressure hoses are all hard pressure hoses, and the pressure pipes are all equipped with instrument pressure pipe joints.

7. A long-distance buried double-walled pipe inner pipe leakage detection device as claimed in claim 6, characterized in that: The pressure stabilizing tank (2) and the mixed pressure stabilizing tank (17) are both provided with pressure-bearing hose connectors.

8. A method for detecting and locating inner tube leakage of a long-distance buried double-walled pipe, using the inner tube leakage detection device of a long-distance buried double-walled pipe as claimed in claim 7, characterized in that: The steps include: Step 1: Connect the flow supply control device A and the data acquisition and analysis device C to the pipeline to be inspected (28) through the connecting flange A (11) and the connecting flange B (24); use a transmission cable to connect the current / digital converter (27), the data acquisition computer (26) and the helium mass spectrometer leak detector (25) and connect the power to the current / digital converter (27), the data acquisition computer (26) and the helium mass spectrometer leak detector (25), respectively, and place the mass spectrometer suction gun (29) at the outlet end of the inner tube of the pipeline to be inspected (28); Step 2, initial inspection of the inner pipe: open the compressed air source A (1), close the switch valve A (5) and the connecting flange (24), open the switch valve B (6) and the flow control valve (4), and fill the inner pipe of the inspected pipeline (28) with compressed air, the compressed air pressure is greater than 0.1 MPa; at this time, the interlayer of the inspected pipeline (28) maintains atmospheric pressure, and after stabilization for four hours, measure the leakage rate of the inner pipe of the inspected pipeline (28); select a suitable reference leak hole and install it at the position of the standard leak hole (10); Step 3: Fill the interlayer of the pipeline to be tested with helium; close the switch valve (21), open the switch valve (22), start the vacuum pump (23) to evacuate the interlayer of the pipeline to be tested; stop the vacuum pump (23), open the switch valve (21), close the switch valve (22), open the helium bottle (12) and the compressed air bottle (13), and fill the interlayer with a mixture of helium and air of a certain concentration; close the switch valve (21) after filling to a certain pressure; Step 4, detection: open the switch valve A (5) and close the switch valve B (6), adjust the air flow rate in the inner tube to V1 through the flow transmitter (7); after the air flow rate is stable and the signal of the helium mass spectrometer leak detector is stable, adjust the flow control valve to adjust the air flow rate to V2; if there is a leak, the helium concentration curve on the helium mass spectrometer leak detector (25) and the data acquisition computer (26) shows obvious mutations, and the number of mutations represents the number of leaks. The data acquisition computer (26) calculates the distance between the leak and the mass spectrometer leak detector according to the time t between the concentration change moment of the helium mass spectrometer leak detector and the last concentration change moment, the air temperature T, the pipeline cross-sectional area S, and the pipeline flow rate V2 parameters. The formula for calculating the distance between the leak and the mass spectrometer leak detector is as follows (1): Among them, 273 is a fixed parameter value, that is, the Kelvin temperature corresponding to 0°C.

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