Device and method for measuring depth of corrosion pit on surface of pipeline and evaluation method

Abstract

According to the pipeline surface corrosion pit depth measuring device and method and the evaluating method, the measuring device and method can accurately and efficiently measure the depth of a large-area corrosion pit, the depth serves as an input condition, finally, the residual life of the pipeline is evaluated based on the residual wall thickness, safe and stable operation of the pipeline can be guaranteed, and the working efficiency of the pipeline is improved. Pipeline leakage or explosion accidents and the like caused by wall thickness loss and running time exceeding the residual life are avoided, property loss or casualties are avoided, and great practical significance is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel pipe inspection, and particularly relates to a device, a method and an evaluation method for measuring the depth of corrosion pits on the surface of a pipeline. Background Art

[0002] During the long-term service of oil and gas pipelines, various corrosion pit defects are likely to occur due to various corrosion media and soil and other factors. These defects will reduce the remaining wall thickness of the pipeline and have a serious impact on the safe operation of the pipeline. By accurately measuring the depth of the corrosion pit, the remaining wall thickness of the pipeline can be accurately calculated. When evaluating the remaining life of the pipeline, the remaining wall thickness is an important input data for evaluating the remaining life of the pipeline. Using the pipeline remaining life evaluation method, the remaining life of the pipeline can be calculated. If the remaining wall thickness of the pipeline is seriously insufficient and does not meet the requirements for the safe operation of the in-service pipeline, then it may be necessary to replace the new pipeline. At present, the minimum wall thickness of oilfield gathering pipelines is about 4 mm. If the depth of the corrosion pits on the pipeline is not accurately measured, even if the error is about 0.5 mm, it will have a great impact on the calculation of the remaining life of the pipeline, thus affecting the safe operation of the entire pipeline. Therefore, accurately measuring the depth of the corrosion pit and evaluating the safety performance of the pipeline have great practical significance for the safe operation of the pipeline and the evaluation of the remaining life.

[0003] At present, pipeline corrosion pits can be divided into two types. One type is individual, local, small-area punctiform corrosion pits (see Figure 1 ), and the other type is large-area corrosion pits with different corrosion depths (see Figure 2 ). For the Figure 1 shown corrosion pit, its concave pit area is not large, and there is a relatively close reference plane on both sides of the corrosion pit. The conventional corrosion pit measuring instrument can be placed on both sides of the corrosion pit, and thus the depth of the corrosion pit can be measured relatively accurately ( Figure 3 ).

[0004] However, for the Figure 2 shown large-area corrosion pit, there is currently no good measurement method. Because the area of the part with a lower position of this kind of corrosion pit is large, and the position to be measured is far from the non-corroded part of the steel pipe, the conventional corrosion pit measuring instrument cannot be placed normally, making the two sides of the measuring instrument in a horizontal position. Therefore, the depth of this kind of corrosion pit cannot be accurately measured ( Figure 4 ), which has a serious impact on the evaluation of the remaining life of the pipeline in the later stage. As Figure 4As shown, the depth data of the corrosion pit measured by the conventional corrosion pit measuring instrument is a, while the actual depth of the corrosion pit is b, with a relatively large difference. It can be said that the data a is an incorrect corrosion pit depth data. Currently, for large-area corrosion pits, there is no effective measurement method that can make the measurement result be the corrosion pit with the maximum depth and the measurement data be accurate, nor is there a method to evaluate the remaining life of the pipeline using the remaining wall thickness of the pipeline.

[0005] Chinese patent document CN206378093U discloses a corrosion pit depth measuring instrument. It consists of a balance weight and a digital display meter, and can complete the measurement of the depths of various corrosion pits on metal and non-metal oil pipes, pipelines, storage tanks, etc. However, it must be placed on both sides of the corrosion pit and can only measure corrosion pits with a small area. For the depth of large-area corrosion pits at a lower position, it cannot accurately measure, and there is no effective measurement and inspection method to determine whether the measurement data is for the deepest corrosion pit, and it does not evaluate the safety performance of the pipeline.

[0006] Chinese patent document CN203132482U discloses a pitting corrosion pit depth measuring instrument. It mainly consists of a micrometer, and the probe of the micrometer has a test end that gradually tapers into a fine needle tip shape, etc. It is mainly used for on-site measurement of pitting corrosion pits with a small area. For the depth of large-area corrosion pits, it cannot accurately measure, and there is no effective measurement method to determine whether the measurement data is for the deepest corrosion pit, and it does not evaluate the safety performance of the pipeline.

[0007] Chinese patent document CN103175499A discloses a portable measuring instrument for the depth of local corrosion pits on pipes. It is used for on-site rapid measurement of the depth of corrosion pits after local corrosion occurs on metal pipes. The main instrument is a displacement sensor, and the pitting corrosion depth is directly read through the digital display meter connected to the sensor. However, it can only measure corrosion pits with a small area and close edges. The instrument can be placed horizontally on both sides of the pit. For the depth of large-area corrosion pits with a large area and a lower position on one side, it cannot accurately measure, and there is no effective measurement method to determine whether the measurement data is for the deepest corrosion pit, and it does not evaluate the safety performance of the pipeline.

[0008] Chinese patent document CN201382769 discloses a multi-purpose equipment corrosion pit depth measuring instrument and Chinese patent document CN201166541Y discloses a corrosion pit depth measuring instrument. Their disadvantages are similar to those of the above-mentioned documents. They can only measure pitting corrosion pits with a small area and cannot accurately measure large-area corrosion pits. There is no effective measurement method to determine whether the measurement data is for the deepest corrosion pit, and they do not evaluate the safety performance of the pipeline.

[0009] Chinese Patent Document CN111879211A discloses a device and method for unidirectional measurement of the depth of corrosion pits on the surface of steel pipes, which can be used to measure large-area corrosion pit defects. However, this device determines whether the horizontal scale is horizontal based on the position of the bubble. Since the position of the bubble is variable and its position is observed visually, it is not accurate enough and is likely to affect the accuracy of the final result. This method also does not provide a complete inspection method for the depth of corrosion pits on the surface of oil and gas pipelines, nor does it evaluate the remaining life of the pipeline. Summary of the Invention

[0010] To solve the problems of the above-mentioned prior art, the present invention provides a device, method and evaluation method for measuring the depth of corrosion pits on the surface of pipelines. This device and method can more accurately inspect the depth of large-area corrosion pits, have a higher detection efficiency, accurate and reliable detection results, and can evaluate the remaining life of the pipeline.

[0011] The present invention is achieved through the following technical solutions:

[0012] A device for measuring the depth of corrosion pits on the surface of a pipeline includes: a base, a vertical measuring scale, a fixing bolt, a knob, a laser rangefinder, a horizontal scale, a movable vertical rod and a probe; the vertical measuring scale is vertically arranged on the upper surface of the base, and the laser rangefinder is arranged on the vertical measuring scale; the horizontal scale is vertically arranged with the vertical measuring scale and both are provided with scale lines. The vertical measuring scale is provided with a first through groove along its length direction, and the horizontal scale is provided with a second through groove along its length direction. The fixing bolt slides through the first through groove and the second through groove, and the knob is sleeved on one end of the fixing bolt; the movable vertical rod is vertically fixedly connected to the horizontal scale, and the side surface of the movable vertical rod opposite to the vertical measuring scale is located at the zero position of the scale line on the horizontal scale; the probe is arranged at the bottom of the movable vertical rod; the fixing bolt corresponds to the laser rangefinder in the up and down position, and the laser beam emitted by the laser rangefinder is perpendicular to the vertical measuring scale and can irradiate on the side surface of the movable vertical rod opposite to the vertical measuring scale.

[0013] Preferably, the base is a ferromagnetic base.

[0014] A method for measuring the depth of corrosion pits on the surface of a pipeline, based on the above-mentioned measuring device, includes:

[0015] Fix the base at the non-corroded part of the pipeline, adjust the knob so that the horizontal scale can move up, down, left and right. Using the visual observation method, adjust the position of the horizontal scale so that the tip of the probe touches the bottom of the target corrosion pit. Turn on the laser rangefinder and measure the distance between the laser rangefinder and the moving vertical rod as a2; read the reading of the fixed bolt on the horizontal scale for the position as a1 through the scale line; when a1 = a2, it means that the horizontal scale is parallel to the pipeline axis; at this time, tighten the knob, and read the distance h1 between the base and the bottom surface of the horizontal scale according to the vertical measuring ruler. Calculate the depth h2 of the target corrosion pit based on h1 and h3, where h3 is the distance between the bottom of the probe tip and the bottom surface of the horizontal scale.

[0016] A method for measuring the depth of a corrosion pit on the surface of a pipeline, comprising:

[0017] Step 1, determine the area where the target corrosion pit is located;

[0018] Step 2, measure the area S1 of the area where the target corrosion pit is located, and compare it with the set threshold S2 to judge the type of the target corrosion pit: if S1 < S2, determine that the type of the target corrosion pit is a pitting corrosion pit; if S1 ≥ S2, determine that the type of the target corrosion pit is a large-area corrosion pit;

[0019] Step 3, if the type of the target corrosion pit is a large-area corrosion pit, use the visual method to find the target corrosion pit in the area of the large-area corrosion pit. If the number of target corrosion pits is greater than 1, measure the depth of each target corrosion pit using the said measuring device respectively, compare the depths of each target corrosion pit, find the target corrosion pit with the maximum depth, and take the depth of this target corrosion pit as the depth of the large-area corrosion pit; if the number of target corrosion pits is 1, measure the depth of the target corrosion pit using the said measuring device as the depth of the large-area corrosion pit; if the type of the target corrosion pit is a pitting corrosion pit, measure the depth of the target corrosion pit as the depth of the pitting corrosion pit.

[0020] Preferably, in Step 1, to determine the area where the target corrosion pit is located, it includes: determining the position of the target corrosion pit on the pipeline surface and cleaning the impurities and rust on the surface of the target corrosion pit.

[0021] Preferably, in Step 2, to measure the area S1 of the area where the target corrosion pit is located, the method includes: determining the boundary lines of the area where the target corrosion pit is located in the axial direction and the cross-section of the pipeline. Each boundary line forms a rectangular area, and then use the product of the length and width of the rectangular area as the area S1.

[0022] Preferably, in Step 3, if the type of the target corrosion pit is a pitting corrosion pit, then measure the depth of the target corrosion pit using the said measuring device.

[0023] Preferably, in step 3, the depth of the target corrosion pit is measured by using the said measuring device, which specifically includes: fixing the base at the non-corroded part of the pipeline, adjusting the knob so that the horizontal scale can move up, down, left and right. By using the visual observation method, adjust the position of the horizontal scale so that the tip of the probe touches the bottom of the corrosion pit. Turn on the laser rangefinder and measure the distance between the laser rangefinder and the moving vertical rod as a2; read the reading of the fixed bolt on the horizontal scale for the position through the scale line as a1; when a1 = a2, it indicates that the horizontal scale is parallel to the pipeline axis; at this time, tighten the knob, and read the distance h1 between the base and the bottom surface of the horizontal scale according to the vertical measuring ruler. Calculate the depth h2 of the corrosion pit according to h1 and h3, where h3 is the distance between the bottom of the probe tip and the bottom surface of the horizontal scale.

[0024] A method for evaluating the remaining life of a pipeline, according to the depth of the large-area corrosion pit or the depth of the punctiform corrosion pit obtained by the said measuring method, calculates the remaining life of the pipeline according to the said depth, and obtains the remaining life value of the pipeline.

[0025] Preferably, the formula for calculating the remaining life of the pipeline is as follows:

[0026]

[0027] Wherein, P is the designed transportation pressure of the pipeline, D is the outer diameter of the pipeline, C is the corrosion rate of the pipeline, F is the designed stress of the pipeline, T is the pipeline wall thickness, and k1 is the correlation coefficient of the ratio between the remaining cross-sectional area of the pipeline body and the cross-sectional area of the pipeline body.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The method of the present invention has accurate measurement data and simple operation.

[0030] The device for measuring the depth of the corrosion pit on the surface of the pipeline of the present invention is placed on the pipeline through the base, so it can be fixed unilaterally and can accurately and efficiently measure the depth of the large-area corrosion pit. And a laser rangefinder is added to the device of the present invention. The distance between the moving vertical rod and the vertical measuring ruler is measured by the laser rangefinder. When this distance is consistent with the reading of the horizontal scale, it indicates that the horizontal scale is in a horizontal state. The present invention uses the laser rangefinder to check whether the horizontal scale is in a horizontal device, which is more accurate and efficient than the method of using a bubble. The detection efficiency of the measuring device of the present invention is relatively high, and the detection is accurate and reliable.

[0031] The method for measuring the depth of corrosion pits on the surface of a pipeline according to the present invention classifies the target corrosion pits. For large-area corrosion pits, the measuring device of the present invention is used for measurement, which has high accuracy. By comparing the depths of different target corrosion pits, the target corrosion pit with the maximum depth is found, and the depth of this target corrosion pit is used as the depth of the large-area corrosion pit. This technology has high detection efficiency, is accurate and reliable in detection, and can be widely used in oilfield enterprises and pipeline companies.

[0032] The present invention takes the depth of the target corrosion pit with the maximum depth as the input condition, and finally evaluates the remaining life of the pipeline based on the remaining wall thickness, which can ensure the safe and stable operation of the pipeline, avoid pipeline leakage or explosion accidents caused by wall thickness loss and operation time exceeding the remaining life, and avoid property losses or casualties, which has great practical significance. Brief Description of the Drawings

[0033] Figure 1 It is a schematic diagram of a punctiform corrosion pit;

[0034] Figure 2 It is a schematic diagram of a large-area corrosion pit;

[0035] Figure 3 It is a schematic diagram of a punctiform corrosion pit measured by a conventional corrosion pit measuring instrument;

[0036] Figure 4 It is a schematic diagram of a large-area corrosion pit measured by a conventional corrosion pit measuring instrument;

[0037] Figure 5 It is a schematic diagram for calculating the area of the region where the target corrosion pit is located;

[0038] Figure 6 It is a schematic diagram of the structure of the measuring device of the present invention;

[0039] Figure 7 For Figure 6 Cross-sectional view A-A in

[0040] Figure 8 It is an implementation schematic diagram of the measuring device of the present invention for measuring a large-area corrosion pit;

[0041] Figure 9 It is a flowchart of the method for measuring the depth of corrosion pits on the surface of a pipeline according to the present invention.

[0042] In the figure: 1 - base, 2 - vertical measuring scale, 3 - fixing bolt, 4 - knob, 5 - laser rangefinder, 6 - scale line, 7 - horizontal scale, 8 - moving vertical rod, 9 - probe, 10 - laser emission beam, 11 - laser return beam. Detailed Embodiment

[0043] To further understand the present invention, the present invention will be described below in conjunction with embodiments. These descriptions are only for further explaining the features and advantages of the present invention and are not used to limit the claims of the present invention.

[0044] As Figure 6 shown, the pipeline surface corrosion pit depth measuring device of the present invention includes: a base 1, a vertical measuring ruler 2, a fixing bolt 3, a knob 4, a laser rangefinder 5, a horizontal scale 7, a movable vertical rod 8 and a probe 9. The base 1 has ferromagnetism, the vertical measuring ruler 2 is vertically fixed on the upper surface of the base 1, and the laser rangefinder 5 is fixedly arranged on the vertical measuring ruler 2. The horizontal scale 7 is vertically arranged with the vertical measuring ruler 2 and both are provided with scale lines 6. The vertical measuring ruler 2 is provided with a first through groove along the length direction, and the horizontal scale 7 is provided with a second through groove along the length direction. The fixing bolt 3 slidably passes through the first through groove and the second through groove. The fixing bolt 3 can freely move up and down in the first through groove of the vertical measuring ruler 2 and can also freely move in the second through groove of the horizontal scale 7. The knob 4 is sleeved on one end of the fixing bolt 3, and the knob 4 can freely rotate on the fixing bolt 3. The top end of the movable vertical rod 8 is vertically fixedly connected to one end of the horizontal scale 7, and the side surface of the movable vertical rod 8 opposite to the vertical measuring ruler 2 is located at the zero position of the scale line 6 on the horizontal scale 7. The probe 9 is arranged at the bottom of the movable vertical rod 8. The fixing bolt 3 corresponds to the laser rangefinder 5 in the up and down position, and the laser emission beam of the laser rangefinder 5 is perpendicular to the vertical measuring ruler 2 and can irradiate on the side surface of the movable vertical rod 8 opposite to the vertical measuring ruler 2.

[0045] As Figure 9 shown, the pipeline surface corrosion pit depth measuring method of the present invention includes:

[0046] B1. Determine the area where the target corrosion pit is located, including the position of the target corrosion pit on the pipeline surface, and clean the impurities, rust, etc. on the surface of the target corrosion pit.

[0047] If the pipeline is outdoors, remove magazines, rust, etc., and determine the most severely corroded area by visual inspection; if the pipeline is in a buried state, it is necessary to remove the external anti-corrosion layer, then remove the soil and other sundries on the pipeline surface, and visually check the most severely corroded area on the surface.

[0048] B2. Measure the area (S1) of the area where the target corrosion pit is located, and compare it with the set threshold (S2) to judge the type of the target corrosion pit.

[0049] Measure the area (S1) of the area where the target corrosion pit is located. The method includes: on the pipeline axis where the target corrosion pit is located, there are several corrosion pits, such as Figure 5As shown in the figure. On the pipeline axis where the target corrosion pit is located, there are several corrosion pits. Draw the four sides a, b, c, and d of a rectangle on the pipeline. Sides a and c are parallel to the pipeline axis, and a = c. Side a is the boundary line of the starting position of the first corrosion pit in the clockwise direction, and side c is the boundary line of the ending position of the last corrosion pit in the clockwise direction. Sides b and d are perpendicular to the pipeline axis, and b = d. Side b is the boundary line of the starting position of the first corrosion pit on the left side of the pipeline axis, and side d is the boundary line of the ending position of the last corrosion pit on the right side of the pipeline axis. The area S1 is equal to the product of a and b.

[0050] Select the base area of a conventional corrosion pit measuring instrument or a specific value based on the area of a certain corrosion pit, which can be set as the set threshold (S2).

[0051] If S1 < S2, it is determined that the type of the target corrosion pit is a pitting corrosion pit (the depth measurement method is shown in step 3). If S1 ≥ S2, it is determined that the type of the target corrosion pit is a large-area corrosion pit (the depth measurement method is shown in step 4).

[0052] B3. If it is determined that the type of the target corrosion pit is a pitting corrosion pit, a conventional corrosion pit measuring instrument (such as Figure 3 ) can be used to measure the depth of the corrosion pit. The method is as follows: Adjust the zero point of the conventional corrosion pit measuring instrument and perform zero calibration. Pull out the probe of the corrosion pit measuring instrument and place the corrosion pit measuring instrument stably on both sides of the corrosion pit. Check visually. When the probe touches the bottom of the corrosion pit, stop moving the probe and read the reading of the corrosion pit measuring instrument. At this time, the depth value of the corrosion pit is obtained. The depth measurement method in B4 can also be used.

[0053] B4. If it is determined that the type of the target corrosion pit is a large-area corrosion pit, the measuring device in the present invention can be used for measurement. The method is as follows:

[0054] B41. Determination of the number of target corrosion pits. Use the visual method to find the target corrosion pit in the area where the large-area corrosion pit is located. The target corrosion pit may be one or n places (n > 1. At this time, the naked eye cannot determine which one has the largest depth. Count the number of corrosion pits that may have the largest depth observed by the naked eye and record it as n places). If it is one place, there is only one depth measurement value. If it is n places, measure each of the n places separately. After obtaining the measurement values, find the one with the largest depth, which is called the first target corrosion pit.

[0055] B42. Depth measurement of the first target corrosion pit. Here, the depth measurement of the corrosion pit is taken as an example with the first target corrosion pit. The measurement methods for the remaining n - 1 places are the same as those for the first target corrosion pit. Such as Figure 7As shown in the figure, place the instrument at the non-corroded part of the steel pipe. Utilize the ferromagnetic property of the base 1 to make the bottom surface of the base 1 closely adhere to the non-corroded part of the steel pipe. Whether the target corrosion pit is on the top of the steel pipe or on the side of the steel pipe, the instrument can be well fixed. Adjust the knob 4 so that the horizontal scale 7 can move freely up and down in the chute of the vertical measuring ruler 2. Select the corrosion pit to be measured. Using the visual observation method, make the tip of the probe 9 contact the bottom of the corrosion pit, as Figure 8 shown. Turn on the laser rangefinder 5. Through the laser emission beam 10 and the laser return beam 11, calculate the distance between the laser rangefinder 5 and the movable vertical rod 8 as a2. At this time, read the reading of the horizontal scale 7 at this time through the engraved groove line 6 as a1. When a1 = a2, the horizontal scale 7 is parallel to the pipeline axis. At this time, tighten the knob 4, and the instrument is already adjusted. h1 is the distance between the base 1 and the bottom surface of the horizontal scale 7, h2 is the depth of the first target corrosion pit, and h3 is the distance (known) between the bottom of the tip of the probe 9 and the bottom of the horizontal scale 7. Then h2 = h3 - h1.

[0056] B5. Using the pipeline remaining life evaluation method, evaluate the remaining life of the pipeline. The remaining life of the pipeline is the length of time that the pipeline can operate safely.

[0057] In the pipeline remaining life evaluation calculation method, substitute parameters such as the remaining wall thickness t of the pipeline, the designed conveying pressure P of the pipeline, and the outer diameter D of the pipeline to obtain the stress value R of the pipeline. The calculation formula of R is:

[0058]

[0059] k1 is a coefficient related to the ratio of the remaining cross-sectional area of the pipeline body (excluding the cross-sectional area of the corrosion pit) to the nominal cross-sectional area of the pipeline body.

[0060] The designed stress of the pipeline is F, the corrosion rate of the pipeline is C (related to parameters such as the conveying medium, conveying pressure, and conveying temperature), and the remaining life of the pipeline is X. Then we can get:

[0061] R ≤ F (2)

[0062] Substitute Equation (1) into Equation (2), and we can get: Then:

[0063]

[0064] Substitute t = T - CX - h2 into Equation (3), where T is the pipeline wall thickness (known), and we can get:

[0065]

[0066] Therefore, the remaining life value of the pipeline is obtained from Equation (4).

Claims

1. A device for measuring the depth of corrosion pits on the surface of a pipeline, characterized in that, Comprising: a base (1), a vertical measuring scale (2), a fixing bolt (3), a knob (4), a laser rangefinder (5), a horizontal scale (7), a movable vertical rod (8) and a probe (9); the vertical measuring scale (2) is vertically arranged on the upper surface of the base (1), and the laser rangefinder (5) is arranged on the vertical measuring scale (2); the horizontal scale (7) is vertically arranged with the vertical measuring scale (2) and both are provided with scale lines (6), the vertical measuring scale (2) is provided with a first through groove along the length direction, the horizontal scale (7) is provided with a second through groove along the length direction, the fixing bolt (3) slides through the first through groove and the second through groove, and the knob (4) is sleeved on one end of the fixing bolt (3); the movable vertical rod (8) is perpendicularly and fixedly connected with the horizontal scale (7), and the side surface of the movable vertical rod (8) opposite to the vertical measuring scale (2) is located at the zero position of the scale line (6) on the horizontal scale (7); the probe (9) is arranged at the bottom of the movable vertical rod (8); the fixing bolt (3) corresponds to the laser rangefinder (5) in the up-and-down position, and the laser emission beam of the laser rangefinder (5) is perpendicular to the vertical measuring scale (2) and can irradiate on the side surface of the movable vertical rod (8) opposite to the vertical measuring scale (2).

2. The pipeline surface corrosion pit depth measuring device according to claim 1, wherein The base (1) is a ferromagnetic base.

3. A method for measuring the depth of corrosion pits on the surface of a pipeline, characterized in that, The measuring device according to any one of claims 1-2, comprising: Fix the base (1) at an uncorroded part of the pipeline, adjust the knob (4) so that the horizontal scale (7) can move up, down, left and right. By using the visual observation method, adjust the position of the horizontal scale (7) so that the tip of the probe (9) touches the bottom of the target corrosion pit. Turn on the laser rangefinder (5) and measure the distance between the laser rangefinder (5) and the movable vertical rod (8) as a2; read the reading of the position of the fixing bolt (3) on the horizontal scale (7) through the scale line (6) as a1; when a1 = a2, it indicates that the horizontal scale (7) is parallel to the pipeline axis; at this time, tighten the knob (4), read the distance h1 between the base (1) and the bottom surface of the horizontal scale (7) according to the vertical measuring scale (2), and calculate the depth h2 of the target corrosion pit according to h1 and h3, where h3 is the distance between the bottom of the tip of the probe (9) and the bottom surface of the horizontal scale (7).

4. A method for measuring the depth of corrosion pits on the surface of a pipeline, characterized in that, Comprising: Step 1, determine the area where the target corrosion pit is located; Step 2, measure the area S1 of the area where the target corrosion pit is located and compare it with the set threshold S2 to judge the type of the target corrosion pit: if S1 < S2, determine that the type of the target corrosion pit is a pitting corrosion pit; if S1 ≥ S2, determine that the type of the target corrosion pit is a large-area corrosion pit. Step 3: If the target corrosion pit type is a large-area corrosion pit, use the visual method to search for the target corrosion pit in the area where the large-area corrosion pit is located. If the number of target corrosion pits is greater than 1, use the measuring device described in any one of claims 1-2 to measure the depths of each target corrosion pit, compare the depths of each target corrosion pit, find the target corrosion pit with the maximum depth, and use the depth of this target corrosion pit as the depth of the large-area corrosion pit; if the number of target corrosion pits is 1, use the measuring device described in any one of claims 1-2 to measure the depth of the target corrosion pit as the depth of the large-area corrosion pit; if the target corrosion pit type is a punctiform corrosion pit, measure the depth of the target corrosion pit as the depth of the punctiform corrosion pit.

5. The method for measuring the depth of the corrosion pit on the pipeline surface according to claim 4, characterized in that In step 1, determining the area where the target corrosion pit is located includes: determining the position of the target corrosion pit on the pipeline surface and cleaning the impurities and rust on the surface of the target corrosion pit.

6. The method for measuring the depth of corrosion pits on the surface of a pipeline according to claim 4, characterized in that, In step 2, measuring the area S1 of the area where the target corrosion pit is located, the method includes: determining the boundary lines of the area where the target corrosion pit is located in the axial direction and the cross-section of the pipeline, and each boundary line forms a rectangular area, and then using the product of the length and width of the rectangular area as the area S1.

7. The method for measuring the depth of corrosion pits on the surface of a pipeline according to claim 4, wherein In step 3, if the target corrosion pit type is a punctiform corrosion pit, use the measuring device described in any one of claims 1-2 to measure the depth of the target corrosion pit.

8. The method for measuring the depth of corrosion pits on the surface of a pipeline according to claim 4, wherein In step 3, using the measuring device described in any one of claims 1-2 to measure the depth of the target corrosion pit specifically includes: fixing the base (1) at the non-corroded part of the pipeline, adjusting the knob (4) so that the horizontal scale (7) can move up, down, left, and right. Using the visual observation method, adjust the position of the horizontal scale (7) so that the tip of the probe (9) touches the bottom of the corrosion pit. Turn on the laser rangefinder (5) and measure the distance between the laser rangefinder (5) and the moving vertical rod (8) as a2; read the reading of the fixed bolt (3) on the horizontal scale (7) for the position through the scale line (6) as a1; when a1 = a2, it means that the horizontal scale (7) is parallel to the pipeline axis; at this time, tighten the knob (4), and according to the vertical measuring ruler (2), read the distance h1 between the base (1) and the bottom surface of the horizontal scale (7), and calculate the depth h2 of the corrosion pit based on h1 and h3, where h3 is the distance between the bottom of the tip of the probe (9) and the bottom surface of the horizontal scale (7).

9. A method for evaluating the remaining life of a pipeline, characterized in that, Based on the depth of the large-area corrosion pit or the depth of the punctiform corrosion pit obtained by the measuring method described in any one of claims 4-8, calculate the remaining life of the pipeline according to the depth, and obtain the remaining life value of the pipeline.

10. The pipeline remaining life evaluation method according to claim 9, wherein The formula for calculating the remaining life of the pipeline is as follows: Wherein, P is the designed transportation pressure of the pipeline, D is the outer diameter of the pipeline, C is the corrosion rate of the pipeline, F is the designed stress of the pipeline, T is the pipeline wall thickness, and k1 is a coefficient related to the ratio of the remaining cross-sectional area of the pipeline body to the nominal cross-sectional area of the pipeline body.

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