Method and device for detecting corrosion in water pipeline

Abstract

The invention discloses a method and a device for detecting internal corrosion of a water pipeline. Pressure drop calculation is performed on the water pipeline, internal corrosion sensitive points of the water pipeline are obtained through prediction, and the internal corrosion condition of the whole pipeline is evaluated based on an excavation direct detection result of the internal corrosion sensitive points. The requirement limitation of intelligent internal detection on the pipe diameter of a water pipeline, the curvature radius of a bent pipe and the conditions of a pipe cleaning device is avoided; through a scientific prediction method, the pipe section most prone to internal corrosion is selected for excavation and direct detection, the excavation detection efficiency and the internal corrosion defect detection rate are improved, and high cost and low efficiency caused by adopting a random excavation or whole-line excavation detection method are avoided.

Description

Technical Field

[0001] The invention relates to the technical field of pipeline corrosion, and in particular to a method and device for detecting corrosion in a water pipeline. Background Art

[0002] Water pipelines are frequently started and stopped, and the flow rate changes dramatically. Due to changes in pumping and working conditions, gas is easily mixed in. When the flow is stopped, bubbles are easily formed at the top of the high pipeline, and the coexistence of gas and liquid provides conditions for internal corrosion.

[0003] If disinfectant is dissolved in the water supply pipe, ClO2 is produced, and ClO2 reacts with water as follows:

[0004] 8ClO2+H2O→2Cl2+7O2+4HClO

[0005] The generated oxygen and hypochlorous acid are both strong oxidants. Therefore, the following electrochemical reactions occur in the pipeline:

[0006] Anode: Fe→Fe 2+ +2e, Fe 2+ +OH - →FeOH+e

[0007] Cathode: HClO + 2e - +H2O→Cl - +OH - , O2+H2O+e - →OH -

[0008] At the same time, the scale attached to the pipeline and the corrosion products are mixed to form a hard shell accumulation, forming an under-scale corrosion environment. - Accelerates pitting.

[0009] Since corrosion inside water pipes can cause defects and failures, it is necessary to conduct inspection and evaluation of corrosion inside water pipes so as to take corresponding control measures.

[0010] At present, there are two methods for detecting internal corrosion of water pipes: one is to carry out intelligent internal detection. This method is expensive and has certain requirements on the pipe diameter, bend radius of curvature, pipe cleaning device conditions, etc. There are a large number of water pipes that cannot be inspected internally; the other is to excavate the pipeline for non-destructive testing. At the current technical level, this method can only be carried out by full-line excavation or random excavation. Full-line excavation has low efficiency, long construction period and high cost, while random excavation has a low probability of finding internal corrosion defects. Summary of the invention

[0011] The purpose of the present invention is to provide a method and device for detecting corrosion in a water pipe to solve the above-mentioned technical problems.

[0012] To achieve the above object, the present invention provides a method for detecting corrosion in a water pipeline, the method comprising:

[0013] Get multiple low-pressure points in the water pipeline;

[0014] Performing nondestructive testing on the multiple low-pressure points to obtain minimum wall thickness data at the target low-pressure points;

[0015] According to the minimum wall thickness data at the target low-pressure point, the corrosion parameters at the target low-pressure point are obtained, and the corrosion parameters at the target low-pressure point are used as the corrosion parameters of the corrosion in the water pipeline.

[0016] Technical effects and advantages of the present invention:

[0017] The present invention predicts the internal corrosion sensitive points of the water pipeline by calculating the pressure drop of the water pipeline, and evaluates the internal corrosion status of the entire pipeline based on the direct detection results of the excavation of the internal corrosion sensitive points. It avoids the restrictions on the pipe diameter, curvature radius of the bend, and the conditions of the cleaning device for intelligent internal detection; through scientific prediction methods, the pipe section most prone to internal corrosion is selected for direct excavation detection, which improves the excavation detection efficiency and the detection rate of internal corrosion defects, and avoids the high cost and low efficiency caused by the random excavation or full-line excavation detection method.

[0018] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a flow chart of the method for detecting corrosion in water pipes;

[0020] Figure 2 It is an elevation data map;

[0021] Figure 3 This is the pressure distribution diagram of the entire line;

[0022] Figure 4A This is the result of X-ray detection No. 6;

[0023] Figure 4B This is the result of X-ray detection No. 7;

[0024] Figure 4C This is the result of X-ray detection No. 8. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings provided by the present invention, and the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0027] In the detection and evaluation of internal corrosion in oil and gas pipelines, there is a direct evaluation method for internal corrosion, which can solve the above problems. Its technical route is: through multiphase flow analysis, select the low-lying points of the pipeline, that is, the points most prone to water accumulation and internal corrosion, for excavation, and select one or more methods such as X-ray, ultrasonic testing, ultrasonic C-scan, etc. for non-destructive testing; based on the internal corrosion conditions of the pipe sections most prone to corrosion, infer and evaluate the internal corrosion conditions of the entire oil and gas pipeline. Its logical basis is the bucket effect.

[0028] Water pipelines can be tested for internal corrosion in a similar way to oil and gas pipelines using direct internal corrosion evaluation methods. However, the internal corrosion law of water pipelines is different from that of oil and gas pipelines. Management practice has found that the most vulnerable locations for internal corrosion in water pipelines are at high places such as pipeline crossing points. Through research on the internal corrosion mechanism of water pipelines, it was found that the most vulnerable sections for internal corrosion are sections with low pressure, and thus the present invention was proposed. The principle on which this method is based is that water pipelines are prone to forming a gas-liquid coexistence space at low pressure, which is calculated by multiphase flow calculation and corrosion rate calculation.

[0029] In order to better explain the present invention, the following Figure 1 A method for detecting corrosion in a water pipeline is explained in detail, the method comprising:

[0030] 1. Obtain multiple low-pressure points in the water pipeline.

[0031] Specifically, obtaining a plurality of low-pressure points of a water pipeline includes: obtaining basic data of the water pipeline; obtaining a plurality of low-pressure points of the water pipeline according to the basic data;

[0032] The basic data include: elevation data, starting point pressure, flow rate, temperature, pipe wall roughness and stop time.

[0033] 2. Perform nondestructive testing on the multiple low-pressure points to obtain minimum wall thickness data at the target low-pressure points.

[0034] The pressure is calculated as follows: the pressure along the pipeline is calculated using the Bernoulli equation and the pressure drop equation, and the low-pressure point is selected as the internal corrosion sensitive point of the water pipeline, and the density is selected as 1-3 / 1km. If it is less than 1km, it is calculated as 1km. If the selected internal corrosion sensitive point is located in a river, cement road, etc., and does not have the conditions for excavation and cannot be excavated directly for testing, then determine whether the point is the lowest pressure point of the entire line. If so, select a point with a similar pressure value next to it for excavation testing; if not, the 1km pipe section can be directly tested without excavation.

[0035] In addition, the pressure calculation along the pipeline is common in this field, and currently there are various types of simulation software for the implementation of the pressure distribution, such as OLGA software (the software can be purchased from Schlumberger, USA), Pipephase software (the software can be purchased from SimSci, USA), etc. By inputting the parameters such as the flow rate, diameter, elevation data of the target pipeline into the above software, the movement of multiphase fluid in the pipeline can be simulated, thereby obtaining the relevant parameters (such as temperature, pressure, etc.) of a certain position in the pipeline.

[0036] Excavate the selected internal corrosion sensitive points, and use X-ray + ultrasonic thickness measurement, or X-ray + ultrasonic C-scan, or X-ray + ultrasonic thickness measurement + ultrasonic C-scan and other methods for non-destructive testing to obtain the minimum wall thickness data of the excavation point (i.e., the target low-pressure point). Among them, X-ray is used for qualitative analysis, ultrasonic thickness measurement is used for quantitative analysis, ultrasonic C-scan can obtain continuous wall thickness changes, and its result is a cloud map; ultrasonic thickness measurement measures the wall thickness of a point, which is discontinuous. Therefore, after excavation, technicians can choose non-destructive testing methods based on detection needs and cost.

[0037] 3. According to the minimum wall thickness data at the target low-pressure point, the corrosion parameters at the target low-pressure point are obtained, and the corrosion parameters at the target low-pressure point are used as the corrosion parameters of the corrosion in the water pipeline.

[0038] The corrosion parameters at the target low-pressure point include: internal corrosion degree, remaining life, and maintenance and use recommendations.

[0039] Specifically, the minimum wall thickness data of the excavation detection point is obtained by non-destructive testing, and the maximum wall thickness reduction ratio of each excavation detection point is calculated. The calculation formula is:

[0040]

[0041] Where, η is the maximum wall thickness reduction ratio, δ is the original / design wall thickness of the pipe at the excavation inspection point, mm, and δ is s ——The minimum wall thickness detected at the excavation inspection point, mm.

[0042] According to the wall thickness corrosion thinning degree evaluation standard table in Table 1, the internal corrosion degree is obtained.

[0043] Table 1 Evaluation standard of wall thickness corrosion thinning degree

[0044] Evaluation level light middle Heavy serious Maximum wall thickness reduction ratio ≤20％ 20％＜～≤40％ 40＜～≤60 >60％

[0045] Specifically, the remaining life of the detection part is calculated.

[0046]

[0047] In the formula, S is the remaining life of the detection part, a; δ min ——Minimum required wall thickness, mm;

[0048] v corr ——Corrosion rate, mm / a;

[0049] The corrosion rate calculation method is as follows:

[0050]

[0051] Where, t is the number of years of operation of the pipeline, a.

[0052] The minimum required wall thickness is calculated as follows:

[0053]

[0054] Among them, δ min ——Minimum required wall thickness, mm; P s ——design pressure, MPa; D——pipeline outer diameter, mm; θ——strength design coefficient of steel pipe; σ s ——Yield strength, MPa.

[0055] Specific, pipeline maintenance and usage recommendations.

[0056] Based on the corrosion degree and remaining life of the excavation inspection point, suggestions are given for pipe replacement / continued use / next evaluation time, etc. Preferably, the next evaluation time is half of the calculated remaining life, but not more than 8 years.

[0057] In order to better explain the present invention, examples are also provided below.

[0058] Take a gas field water pipeline A as an example. The specification is Φ323.9mm×5.6mm, the material is L245N, the design pressure is 4.0MPa, the starting pressure during normal operation is 3.5MPa, and the daily water delivery is 900~2500m 3 / d, the water delivery time is 3 to 5 hours per day, and the rest of the time is stopped. The corrosion detection method for water pipes is as follows:

[0059] 1. Collection of basic data of water pipelines.

[0060] The collected data show that the diameter of steel water pipe A is 323.9mm, the wall thickness is 5.6mm, the design pressure is 4MPa, the material is L245N steel, so the minimum yield strength is 245MPa, the inner wall roughness of the steel pipe is 0.2mm, the conveying temperature is about 20℃, the strength design coefficient of the pipeline is 0.72, and the viscosity of water is 1.01×10^(-3)Pa·s. The normal operating starting pressure of pipeline A is 2950kPa, and the water delivery capacity is 900~2500m 3 / d, the water delivery time is 3 to 5 hours per day, and the rest of the time is stopped. The operation time of pipeline A is 5 years. The elevation-mileage data of pipeline A was collected, and the elevation map is shown in Figure 2 .

[0061] 2. Calculate the pressure distribution and analyze the internal corrosion sensitive points.

[0062] In this evaluation, the pressure calculation formula is used to calculate the pressure along the line:

[0063]

[0064] In the formula, z1 is the starting point elevation, m; p1 is the starting point pressure, kpa; ρ is the density of the delivered water, kg / m3; g is the acceleration due to gravity, 9.8 m / s 2 ; v1——flow velocity at the starting point, m / s; z2——elevation of the point, m; p2——pressure at the point, kpa; v2——flow velocity at the point, m / s; ——flow velocity along the way, m / s; λ——friction coefficient along the way, which can be found in the hydraulic manual; d——inner diameter of the pipe, mm; L——distance from the point to the starting point, m.

[0065] 3. Calculate the pressure distribution diagram of the entire line, see Figure 3 .

[0066] According to the calculation results, 8 internal corrosion sensitive points were selected for pipeline A by selecting 1-3 lowest pressure points per kilometer, see Table 2.

[0067] Table 2 Results of selection of internal corrosion sensitive points

[0068]

[0069]

[0070] Among the 8 internal corrosion sensitive points, 1, 2, 3, 4, and 5 do not meet the conditions for excavation, and are not the lowest pressure points on the entire line, so there is no need to select nearby points for excavation. Therefore, the points that should be excavated and directly tested are 6, 7, and 8, a total of 3 points.

[0071] 4. Use X-ray and ultrasonic thickness measurement non-destructive testing methods to directly detect corrosion-sensitive points in selected water pipelines.

[0072] ①X-ray test results, such as Figure 4A , Figure 4B , Figure 4C shown.

[0073] according to Figure 4A , Figure 4B , Figure 4C It can be seen that there is corrosion wall thinning near the 12 o'clock position of the three excavated inspection pipe sections.

[0074] ②Ultrasonic thickness measurement results.

[0075] At each excavation point, an ultrasonic thickness gauge was used to measure six times at 12 clock positions along the circumference of the pipeline. A total of 72 wall thickness values ​​were measured at each excavation point. The wall thickness measurement results of excavation detection position No. 6 are shown in Table 3.

[0076] Table 3 Wall thickness measurement results of No. 6 excavation detection position

[0077]

[0078]

[0079] Finally, the minimum wall thickness and maximum wall thickness reduction of each excavated pipe section were obtained, see Table 4.

[0080] Table 4 Minimum wall thickness results measured at excavation test points

[0081]

[0082] 5. Post-evaluation.

[0083] ① Determine the degree of internal corrosion based on the maximum wall thickness reduction ratio, see Table 5.

[0084] Table 5 Judgment results of corrosion degree inside excavation detection points

[0085]

[0086] It can be seen that the maximum wall thickness thinning ratio at excavation locations 6, 7, and 8 is in the range of 21%≤~≤40%, so the degree of internal corrosion is moderate.

[0087] ② Based on the data obtained from the test, calculate the corrosion life of the test part.

[0088]

[0089] Where, S is the remaining life of the detection part, a; δ min ——Minimum required wall thickness, mm; v corr ——Corrosion rate, mm / a.

[0090] The minimum required wall thickness of pipeline A is calculated according to the formula calculate:

[0091]

[0092] Calculate the remaining life at point 6 based on the test results:

[0093] Calculate the remaining life at point 7 based on the test results:

[0094] Calculate the remaining life at point 8 based on the test results:

[0095] ③The maintenance and use recommendations for the pipeline are as follows: When pipeline A was tested, the section with the most serious internal corrosion had a moderate degree of internal corrosion; according to the current development of internal corrosion, the minimum remaining life is 1.43 years; the next evaluation time is 8 months (0.715 years) later.

[0096] The present invention also provides a device for detecting corrosion in a water pipe, the device comprising: a low-pressure point acquisition unit, used to obtain multiple low-pressure points in the water pipe; a data acquisition unit, used to perform non-destructive testing on the multiple low-pressure points to obtain minimum wall thickness data at the target low-pressure point; a parameter acquisition unit, used to obtain corrosion parameters at the target low-pressure point based on the minimum wall thickness data at the target low-pressure point, and use the corrosion parameters at the target low-pressure point as corrosion parameters for corrosion in the water pipe.

[0097] Since the content protected by this device is similar to that protected by the above method, no further introduction will be given here. Please refer to the discussion section of the above method for details.

[0098] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for detecting corrosion in a water pipeline, characterized in that: The method comprises: Get multiple low-pressure points in the water pipeline; Performing nondestructive testing on the multiple low-pressure points to obtain minimum wall thickness data at the target low-pressure points; According to the minimum wall thickness data at the target low-pressure point, the corrosion parameters at the target low-pressure point are obtained, and the corrosion parameters at the target low-pressure point are used as the corrosion parameters of the corrosion in the water pipeline.

2. The method according to claim 1, characterized in that Access multiple low-pressure points in the water pipeline, including: Obtaining basic data of the water pipeline; According to the basic data, a plurality of low-pressure points of the water pipeline are obtained; The basic data include: elevation data, starting point pressure, flow rate, temperature, pipe wall roughness and stop time.

3. The method according to claim 2, characterized in that According to the basic data, multiple low-pressure points of the water pipeline are obtained, including: The basic data is processed by using the Bernoulli equation and the pressure drop equation to obtain a plurality of low-pressure points of the water pipeline.

4. The method according to claim 1, characterized in that: The multiple low-pressure points are non-destructively tested by X-ray and ultrasonic thickness measurement.

5. The method according to claim 1, characterized in that The corrosion parameters at the target low-pressure point include: internal corrosion degree and remaining life.

6. The method according to claim 5, characterized in that According to the minimum wall thickness data at the target low pressure point, the internal corrosion degree at the target low pressure point is obtained, including: According to the minimum wall thickness data at the target low pressure point, the wall thickness reduction ratio at the target low pressure point is obtained by the following formula; According to the wall thickness reduction ratio at the target low-pressure point, the internal corrosion degree at the target low-pressure point is obtained; Where η is the maximum wall thickness reduction ratio; δ is the original / design wall thickness of the pipe at the target low pressure point; δ s It is the minimum wall thickness detected at the target low pressure point.

7. The method according to claim 5, characterized in that Obtaining the remaining life at the target low-pressure point according to the minimum wall thickness data at the target low-pressure point, including: obtaining the remaining life at the target low-pressure point by the following formula; Where S is the remaining life at the target low pressure point; δ s is the minimum wall thickness detected at the target low pressure point; δ min is the minimum required wall thickness; v corr is the corrosion rate.

8. The method according to claim 7, characterized in that The corrosion rate and minimum required wall thickness are obtained by the following formula; In the formula, v corr is the corrosion rate; δ is the original / designed wall thickness of the pipeline at the target low pressure point; δ s is the minimum wall thickness detected at the target low-pressure point; t is the service life of the pipeline; δ min is the minimum required wall thickness; P s is the design pressure; D is the outer diameter of the water pipe; θ is the strength design coefficient of the water pipe; σ s is the yield strength.

9. The method according to claim 5, characterized in that The method further includes: obtaining a maintenance and use suggestion for the target low-pressure point according to the internal corrosion degree at the target low-pressure point and the remaining life at the target low-pressure point; The maintenance and use suggestions include: replacing the tube, continuing to use, and the next evaluation time.

10. A water pipeline corrosion detection device, characterized in that: The device comprises: A low-pressure point obtaining unit, used for obtaining multiple low-pressure points of a water pipeline; A data acquisition unit, used for performing nondestructive testing on the plurality of low-pressure points to obtain minimum wall thickness data at the target low-pressure points; The parameter obtaining unit is used to obtain the corrosion parameters at the target low-pressure point according to the minimum wall thickness data at the target low-pressure point, and use the corrosion parameters at the target low-pressure point as the corrosion parameters of the corrosion in the water pipeline.

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