A DC signal combination synchronous detection method for non-cathodic protection buried pipelines

Abstract

The present invention relates to the field of inspection and detection technology, and in particular to a method for synchronous detection of DC signal combination of corrosion of non-cathodic protected buried steel pipelines. The method comprises constructing a DC external detection path for non-cathodic protected buried pipelines, connecting the corresponding connection ends of a portable DC feeding device to an anode, a detection pipeline and a reference electrode, and setting the output DC voltage and current according to the length of the pipeline. Then, the current breaker is connected in series to the buried pipeline detection loop; the pipeline current mapping system (PCM+ / DM) is connected to detect the buried pipeline route, and then synchronous detection is performed by combining the application of close-interval potential measurement technology and DC potential gradient detection technology to achieve detection and evaluation of items such as the corrosion activity state of the pipe body of the cathodic protected buried pipeline and the severity of the damage point of the pipeline anti-corrosion layer. The method solves the major technical difficulties in corrosion detection of non-cathodic protected buried pipelines, realizes DC signal detection of the corrosion status of such pipelines, and improves the inspection and detection quality of such pipelines.

Description

Technical Field

[0001] The invention relates to the field of inspection and detection technology, and in particular to a DC signal combination synchronous detection method for corrosion of non-cathodic protection buried steel pipelines. Background Art

[0002] At present, the buried steel pipeline detection technology includes AC electromagnetic signal detection method and DC signal detection method. AC electromagnetic signal detection method is mainly used to detect and evaluate the quality of the anti-corrosion layer of buried pipelines, including detecting and locating the damaged points of the anti-corrosion layer of buried pipelines and the resistivity of the anti-corrosion layer, but it cannot detect and evaluate the corrosion activity of the pipe body and the severity of the damaged points of the anti-corrosion layer. DC signal detection technology is mainly suitable for the detection of buried pipelines with cathodic protection systems, detecting the damaged points of the anti-corrosion layer, cathodic protection potential, corrosion activity of the pipe body and evaluating the severity of the damage of the anti-corrosion layer.

[0003] As for the detection of non-cathodic protected buried pipelines, since there is no cathodic protection DC power supply system, there is no technical condition for DC signal detection, so the corrosion condition of such pipelines cannot be detected, which affects the quality of corrosion detection of such pipelines. In order to solve the major technical difficulties in the corrosion detection of non-cathodic protected buried pipelines, realize the DC signal detection of the corrosion condition of such pipelines, and improve the inspection and detection quality, a DC signal combination synchronous detection technology for the corrosion of non-cathodic protected buried pipelines has been developed through technical innovation. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] The present invention provides a DC signal combination synchronous detection method for non-cathodic protection buried steel pipeline corrosion, so as to overcome the problem that the non-cathodic protection buried pipeline detection cannot detect and evaluate the corrosion activity of the pipe body and the severity of the damage point of the pipeline anti-corrosion layer.

[0006] (II) Technical solution

[0007] To solve the above problems, the present invention provides a DC signal combination synchronous detection method for non-cathodic protection buried steel pipeline corrosion, comprising the following steps:

[0008] Step S1, prepare for the inspection according to the inspection items;

[0009] Step S2, constructing a DC external detection path for a non-cathodic protected buried pipeline, connecting the corresponding connection ends of the portable DC feeding device to the anode, the detection pipeline and the reference electrode, and setting the output DC voltage and current according to the pipeline length;

[0010] Step S3, setting up a pipeline current mapping system;

[0011] The detection path of the pipeline current mapping system is set up with double-sided multi-point grounding. Multiple grounding electrodes are evenly and symmetrically arranged on both sides of the target pipeline. The grounding electrodes of the same detection path are connected with wires; the equipment grounding wire is connected to the corresponding detection path grounding electrode, and the signal line of the transmitter is connected to the detection signal access point;

[0012] Step S4, detecting the buried pipeline route, comprising:

[0013] Set the signal transmitter of the pipeline current mapping system to a suitable detection signal frequency and output current; set the signal receiver of the pipeline current mapping system to the same detection frequency as the signal transmitter;

[0014] Use signal receivers to detect electromagnetic field signals in buried pipelines, and accurately detect and locate the routing position of buried pipelines based on signal strength;

[0015] Step S5, detecting the damaged points of the anti-corrosion layer of the buried pipeline;

[0016] Hold two probes and conduct inspection along the pipeline route. During the inspection, the two probes should be placed 1-2m apart above the pipeline route and fully contact the soil. Observe the pointer swing of the DCVG device and determine the damage point of the pipeline anti-corrosion layer based on the pointer swing.

[0017] Step S6, marking the damaged points of the anti-corrosion layer of the buried pipeline;

[0018] After detecting the exact location of the damaged point of the outer anti-corrosion layer of the buried pipeline, record the signal value of the damaged point, and then use the real-time dynamic measurement RTK system to measure the position coordinates of the point, record the location coordinates of the damaged point and other information, and make a ground mark on the damaged point of the anti-corrosion layer;

[0019] Step S7, detecting and evaluating the severity of the damage points of the anti-corrosion layer;

[0020] After detecting and locating the damaged point of the anti-corrosion layer of the buried pipeline, the DCVG signal amplitude from the damaged center point to the remote point on the ground is measured by a DC potential gradient detector. The pipe-to-ground potential in the signal on and off state is measured by a close-interval potential detector. The DCVG signal amplitude from the damaged pipeline to the remote point is obtained by calculating the two potential differences. These data are substituted into formula (1) to calculate the severity %IR value of the anti-corrosion layer damage point:

[0021] (1);

[0022] Step S8, detecting and evaluating the corrosion activity state of the pipe body;

[0023] After detecting and locating the damaged point of the anti-corrosion layer of the buried pipeline, place the right-hand probe of the DC potential gradient detector at the center of the damaged point on the ground, and place the left-hand probe on the side 1-2m away from the pipeline. Observe the swing direction of the pointer of the equipment host, and determine the corrosion activity state of the pipe body at the damaged point of the anti-corrosion layer based on the pointer being located in the C / A area of ​​the dial at the moment of on and off: when the pointer is located in the C / C area of ​​the dial, the pipe body is not corroded; when the pointer is located in the A / A area of ​​the dial, the pipe body is corroded; when the pointer is located in the C / A area of ​​the dial, the pipe body is not corroded under effective cathodic protection conditions, and is corroded under conditions of no cathodic protection or ineffective cathodic protection.

[0024] Preferably, step S2 specifically includes: connecting corresponding connection ends of the portable DC feeding device to the anode, the detection pipeline and the reference electrode, and setting the output DC voltage and current according to the pipeline length;

[0025] A GPS synchronous current breaker of a CIPS / DCVG instrument is connected in series in the DC external detection loop of the buried pipeline, the current breaker is connected to a GPS satellite antenna, and the GPS satellite antenna is placed in an open area;

[0026] Set the interruption position of the circuit breaker, open the circuit breaker and wait for the GPS signal. When the GPS signal indicator light changes from red to green, the circuit breaker has completed synchronization with the GPS satellite.

[0027] Preferably, determining the damage point of the pipeline anti-corrosion layer according to the pointer swing in step S5 specifically includes:

[0028] If during the detection process the two probes are placed stably in the soil, and the pointer of the equipment only deflects but does not swing regularly, it means that the anti-corrosion layer of the pipeline at that location is intact; if the pointer of the equipment swings regularly and the frequency of the swing is synchronized with the current breaker, it means that there is a damaged point of the anti-corrosion layer near that location. The closer the detection position is to the damaged point, the larger the swing amplitude of the pointer will be, and the farther away from the damaged point, the smaller the swing amplitude of the pointer will be. After passing the damaged point during the measurement process, the pointer will indicate in the opposite direction, and the damaged point of the anti-corrosion layer can be located by the change of the pointer.

[0029] Preferably, in step S5, during the process of locating the damaged point, when the two probes are on the same ground equipotential line formed by the damaged point, the pointer of the DCVG host will be centered and will not swing or deflect. The perpendicular midline of the line connecting the two probes on the ground passes through the damaged point of the anti-corrosion layer, and then a perpendicular midline is located in a direction perpendicular to the pipeline using the same method. The intersection of the two perpendicular midlines is the exact position of the damaged point of the anti-corrosion layer of the buried pipeline.

[0030] Preferably, after obtaining the %IR value of the severity of the anti-corrosion layer damage point through step S7, it also includes grading the severity of the anti-corrosion layer damage point of the cathodic protected buried pipeline according to the calculation result: when %IR≤15%, the severity of the anti-corrosion layer damage is mild; when 15%<%IR≤60%, the severity of the anti-corrosion layer damage is moderate; when 60%<%IR≤100%, the severity of the anti-corrosion layer damage is severe.

[0031] Preferably, in step S3, the grounding electrode should be more than 20 meters vertically away from the buried pipeline, the depth of each grounding electrode embedded in the soil should be no less than 1 meter, the spacing between adjacent grounding electrodes should be more than 2 meters, and the vertical distance between the equipment signal transmitter and the target pipeline should reach more than 20 meters.

[0032] (III) Beneficial effects

[0033] The DC signal combination synchronous detection method for corrosion of non-cathodic protected buried steel pipelines provided by the present invention solves the major technical problem of corrosion detection of non-cathodic protected buried pipelines, realizes DC signal detection of the corrosion status of such pipelines, and improves the inspection and detection quality of such pipelines. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flow chart of a method for synchronous detection of corrosion of non-cathodic protected buried steel pipelines using combined DC signals according to an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0036] The present invention provides a DC signal combination synchronous detection method for corrosion of non-cathodic protected buried steel pipelines. The method comprises first constructing a DC external detection path for non-cathodic protected buried pipelines, connecting the corresponding connection ends of a portable DC feeding device to an anode, a detection pipeline and a reference electrode, and setting the output DC voltage and current according to the length of the pipeline. Then, the current breaker is connected in series to the buried pipeline detection loop. Then, the pipeline current mapping system (PCM+ / DM) is connected to detect the buried pipeline route, and then synchronous detection is performed by combining the application of close-interval potential measurement technology and DC potential gradient detection technology to achieve detection and evaluation of items such as the corrosion activity state of the cathodic protected buried pipeline and the severity of the damage point of the pipeline anti-corrosion layer.

[0037] like Figure 1 As shown, the method specifically includes:

[0038] 1. Preparation for inspection and construction

[0039] (1) Prepare the DC potential gradient detector and accessories, including: DCVG main unit, probe rod, probe rod handle and connection line, charger and extension line, current breaker, current breaker GPS antenna, wooden plug fixing, wooden plug, saturated copper sulfate solution, etc.

[0040] (2) Mechanically zero the pointer of the DCVG host. Without turning on the power, place the DCVG host flat. If the pointer is not in the middle of the dial, use a flat-blade screwdriver to adjust the zeroing screw to the middle of the dial. Charge the device before testing and add saturated copper sulfate liquid to the probe.

[0041] (3) Place the two wooden plugs at the bottom of the DCVG probes in contact with each other in the soil or close to each other in the water, turn on the DCVG switch to the On position, adjust the range to the minimum position, turn on the leveling switch on the handle of any one of the probes, and manually adjust the knob so that the pointer on the host indicates the middle position of the dial. After completing the leveling of the minimum range, the other ranges are also leveled.

[0042] (4) Prepare the close-interval potential detector and accessories, including: CIPS main unit, probe rod, probe rod handle and connection wire, current breaker, current breaker GPS antenna, wooden plug fixing, wooden plug, saturated copper sulfate solution, etc. Wind the enameled wire for testing onto the tail wire reel, and fix the tail wire reel onto the back frame of the detector. Fill the CIPS detector probe rod with saturated copper sulfate solution and install the probe rod head. The probe rod head needs to be soaked in pure water before use. Charge the device before testing.

[0043] (II) Constructing a DC external detection channel for buried pipelines

[0044] (1) Connect the corresponding connection ends of the portable DC feeding device to the anode, detection pipeline and reference electrode, and set the output DC voltage and current according to the pipeline length.

[0045] (2) Connect the GPS synchronization breaker of the CIPS / DCVG instrument in series in the DC external detection circuit of the buried pipeline. Connect the GPS satellite antenna to the breaker and place the GPS satellite antenna in an open area. Set the interruption position of the breaker. Turn on the breaker and wait for the GPS signal. When the GPS signal indicator light changes from red to green, the breaker has completed synchronization with the GPS satellite.

[0046] (III) Equipment pipeline current mapping system

[0047] The detection path of the pipeline current mapping system (PCM+ / DM) should be set up with double-sided multi-point grounding, and multiple grounding electrodes should be evenly and symmetrically arranged on both sides of the target pipeline. The grounding electrode should be more than 20 meters vertically away from the buried pipeline, and each grounding electrode should be embedded in the soil to a depth of not less than 1 meter. The spacing between adjacent grounding electrodes should be more than 2 meters, and the grounding electrodes in the same detection path should be connected with wires. The vertical distance between the equipment signal transmitter and the target pipeline should be more than 20 meters to prevent signal interference. Connect the power cord, signal line and grounding wire of the equipment signal transmitter. Connect the equipment grounding wire to the corresponding detection path grounding electrode, grind off the rust and paint at the detection signal source access point to ensure good conductivity, and then connect the transmitter's signal line to the detection signal access point. Perform safety protection work at the detection signal source location.

[0048] 4. Detection of buried pipeline routes

[0049] Turn on the signal transmitter of the pipeline current mapping system and set the appropriate detection signal frequency and output current. Turn on the signal receiver of the pipeline current mapping system and select the same detection frequency as the signal transmitter. The inspector uses the signal receiver to detect the electromagnetic field signal in the buried pipeline and accurately detect and locate the route position of the buried pipeline based on the signal strength. Use the RTK system to measure and record the starting and ending points, turning points, measurement sampling points, branch points, crossing points, and spanning points of the buried pipeline route.

[0050] (V) Detection of damaged points of anti-corrosion layer of buried pipelines

[0051] After the inspector connects and sets up the DCVG inspection equipment, he carries the equipment and holds two probes to inspect along the pipeline route. During the inspection, the two probes should be 1-2m apart above the pipeline route and fully in contact with the soil. The inspector needs to observe the swing of the pointer of the DCVG equipment and determine the damaged point of the pipeline anti-corrosion layer according to the swing of the pointer. If the two probes are placed stably in the soil during the inspection, and the pointer of the equipment only deflects but does not swing regularly, it means that the anti-corrosion layer of the pipeline at that location is intact; if the pointer of the equipment swings regularly and the frequency of the swing is synchronized with the current breaker, it means that there is a damaged point of the anti-corrosion layer near the location. When the inspection position is closer to the damaged point, the swing amplitude of the pointer will become larger and larger, and the swing amplitude of the pointer will become smaller and smaller when it is far away from the damaged point. After passing the damaged point during the measurement process, the pointer will indicate in the opposite direction, and the damaged point of the anti-corrosion layer can be roughly located by the change of the pointer.

[0052] During the process of locating the damaged point, when the two probes are on the same ground equipotential line formed by the damaged point, the pointer of the DCVG host will be centered and will not swing or deflect. The median perpendicular line connecting the two probes on the ground passes through the damaged point of the anti-corrosion layer. Then, the same method is used to locate a median perpendicular line in the direction perpendicular to the pipeline. The intersection of the two median perpendicular lines is the exact location of the damaged point of the anti-corrosion layer of the buried pipeline.

[0053] (VI) Marking the damaged points of the anti-corrosion layer of buried pipelines

[0054] After the inspectors detect the exact location of the damaged point of the anti-corrosion layer on the outside of the buried pipeline, they record the signal value of the damaged point, and then use the RTK system to measure the position coordinates of the point, record the position coordinates of the damaged point and other information, and make a ground mark on the damaged point of the anti-corrosion layer.

[0055] (VII) Detection and evaluation of the severity of damage to the anti-corrosion layer

[0056] After detecting and locating the damaged point of the anti-corrosion layer of the buried pipeline, the DCVG signal amplitude value (IR) from the center point of the damaged point on the ground to the remote point is measured by a DC potential gradient detector. The pipe-to-ground potential (IR) in the signal on and off state is measured by a close-interval potential detector. The DCVG signal amplitude value (IR) from the pipeline at the damaged point to the remote point is obtained by calculating the two potential differences. Substitute these data into the formula:

[0057]

[0058] Calculate the %IR value of the severity of the anti-corrosion layer damage point, and classify the severity of the anti-corrosion layer damage point of the cathodic protected buried pipeline according to the calculation result: when %IR≤15%, the severity of the anti-corrosion layer damage is mild; when 15%<%IR≤60%, the severity of the anti-corrosion layer damage is moderate; when 60%<%IR≤100%, the severity of the anti-corrosion layer damage is severe.

[0059] (VIII) Detection and evaluation of the corrosion activity of the pipe body

[0060] After detecting and locating the damaged point of the anti-corrosion layer of the buried pipeline, place the right-hand probe of the DC potential gradient detector at the center of the damaged point on the ground, and place the left-hand probe on the side 1-2m away from the pipeline. Observe the swing direction of the pointer of the equipment host, and determine the corrosion activity state of the pipe body at the damaged point of the anti-corrosion layer based on the pointer being located in the C / A area of ​​the dial at the moment of on and off: when the pointer is located in the C / C area of ​​the dial, the pipe body is not corroded; when the pointer is located in the A / A area of ​​the dial, the pipe body is corroded; when the pointer is located in the C / A area of ​​the dial, the pipe body is not corroded under effective cathodic protection conditions, and is corroded under conditions of no cathodic protection or ineffective cathodic protection.

[0061] The DC signal combination synchronous detection technology for corrosion of non-cathodic protected buried pipelines provided by the present invention solves the major technical problem of corrosion detection of non-cathodic protected buried pipelines, realizes DC signal detection of the corrosion status of such pipelines, and improves the inspection and detection quality of such pipelines.

[0062] The technical contents not mentioned in the above method can be realized by adopting or drawing on the existing technology, and will not be described in detail. The above-mentioned embodiments are only the embodiments of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present invention, several deformations, equivalent substitutions, improvements, etc. can be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A DC signal combination synchronous detection method for non-cathodic protection buried pipelines, characterized in that: The steps include: Step S1, prepare for the inspection according to the inspection items; Step S2: construct a DC external detection path for non-cathodic protected buried pipelines, connect the corresponding connection ends of the portable DC feeding device to the anode, the detection pipeline and the reference electrode, and set the output DC voltage and current according to the pipeline length. Specifically include: A GPS synchronous current breaker of a CIPS / DCVG instrument is connected in series in the DC external detection loop of the buried pipeline, the current breaker is connected to a GPS satellite antenna, and the GPS satellite antenna is placed in an open area; Set the interruption position of the breaker, open the breaker and wait for the GPS signal. When the GPS signal indicator light changes from red to green, the breaker has completed synchronization with the GPS satellite. Step S3, setting up a pipeline current mapping system; The detection path of the pipeline current mapping system is set up with double-sided multi-point grounding. Multiple grounding electrodes are evenly and symmetrically arranged on both sides of the target pipeline. The grounding electrodes of the same detection path are connected with wires; the equipment grounding wire is connected to the corresponding detection path grounding electrode, and the signal line of the transmitter is connected to the detection signal access point; Step S4, detecting the buried pipeline route, comprising: Set the signal transmitter of the pipeline current mapping system to a suitable detection signal frequency and output current; set the signal receiver of the pipeline current mapping system to the same detection frequency as the signal transmitter; Use signal receivers to detect electromagnetic field signals in buried pipelines, and accurately detect and locate the routing position of buried pipelines based on signal strength; Step S5, detecting the damaged points of the anti-corrosion layer of the buried pipeline; Hold two probes and conduct inspection along the pipeline route. During the inspection, the two probes should be placed 1-2m apart above the pipeline route and fully contact the soil. Observe the pointer swing of the DCVG device and determine the damage point of the pipeline anti-corrosion layer based on the pointer swing. Among them, the specific conditions for determining the damage point of the pipeline anti-corrosion layer according to the pointer swing include: If during the test, the two probes are placed steadily in the soil, and the pointer of the device only deflects but does not swing regularly, it means that the anti-corrosion layer of the pipeline at that location is intact; if the pointer of the device swings regularly and the frequency of the swing is synchronized with the breaker, it means that there is a damaged point of the anti-corrosion layer near that location. When the test location is closer to the damaged point, the swing amplitude of the pointer will become larger and larger, and when it is farther away from the damaged point, the swing amplitude of the pointer will become smaller and smaller. After passing the damaged point during the measurement process, the pointer will indicate in the opposite direction, and the damaged point of the anti-corrosion layer can be located by the change of the pointer. Step S6, marking the damaged points of the anti-corrosion layer of the buried pipeline; After detecting the exact location of the damaged point of the outer anti-corrosion layer of the buried pipeline, record the signal value of the damaged point, and then use the real-time dynamic measurement RTK system to measure the position coordinates of the point, record the position coordinate information of the damaged point, and make a ground mark on the damaged point of the anti-corrosion layer; Step S7, detecting and evaluating the severity of the damage points of the anti-corrosion layer; After detecting and locating the damaged point of the anti-corrosion layer of the buried pipeline, a DC potential gradient detector is used to measure the DCVG signal amplitude value from the damaged center point to the remote point on the ground. The close-interval potential detector is used to measure the pipe-to-ground potential in the signal on and off states. The DCVG signal amplitude value from the damaged pipeline to the remote point is obtained by calculating the two potential differences. The DCVG signal amplitude value from the damaged center point to the remote point and the DCVG signal amplitude value from the damaged pipeline to the remote point are substituted into formula (1) to calculate the severity %IR value of the anti-corrosion layer damage point: （1）； Step S8, detecting and evaluating the corrosion activity state of the pipe body; After detecting and locating the damaged point of the anti-corrosion layer of the buried pipeline, place the right-hand probe of the DC potential gradient detector at the center of the damaged point on the ground, and place the left-hand probe on the side 1-2m away from the pipeline. Observe the swing direction of the pointer of the equipment host, and determine the corrosion activity state of the pipe body at the damaged point of the anti-corrosion layer based on the pointer being located in the C / A area of ​​the dial at the moment of on and off: when the pointer is located in the C / C area of ​​the dial, the pipe body is not corroded; when the pointer is located in the A / A area of ​​the dial, the pipe body is corroded; when the pointer is located in the C / A area of ​​the dial, the pipe body is not corroded under effective cathodic protection conditions, and is corroded under conditions of no cathodic protection or ineffective cathodic protection.

2. The DC signal combination synchronous detection method for non-cathodic protection buried pipeline according to claim 1 is characterized in that: Step S5: During the process of locating the damaged point, when the two probes are on the same ground equipotential line formed by the damaged point, the pointer of the DCVG host will be centered and will not swing or deflect. The perpendicular midline of the line connecting the two probes on the ground passes through the damaged point of the anti-corrosion layer. Then, the same method is used to locate a perpendicular midline in the direction perpendicular to the pipeline. The intersection of the two perpendicular midlines is the exact position of the damaged point of the anti-corrosion layer of the buried pipeline.

3. The DC signal combination synchronous detection method for non-cathodic protection buried pipeline according to claim 1, characterized in that: After the severity %IR value of the anti-corrosion layer damage point is obtained through step S7, the method also includes grading the severity of the anti-corrosion layer damage point of the cathodic protected buried pipeline according to the calculation result: when %IR≤15%, the severity of the anti-corrosion layer damage is mild; when 15%<%IR≤60%, the severity of the anti-corrosion layer damage is moderate; when 60%<%IR≤100%, the severity of the anti-corrosion layer damage is severe.

4. The DC signal combination synchronous detection method for non-cathodic protection buried pipeline according to claim 1, characterized in that: In step S3, the grounding electrode should be more than 20 meters vertically away from the buried pipeline, each grounding electrode should be embedded in the soil to a depth of not less than 1 meter, the spacing between adjacent grounding electrodes should be more than 2 meters, and the vertical distance between the equipment signal transmitter and the target pipeline should reach more than 20 meters.

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