Method for Establishing Inspection Frequency of Corroded Pipelines

Abstract

The present invention discloses a method for formulating the detection frequency of a corroded pipeline, comprising the following steps: (1) selecting a pipe section to be measured, (2) performing surface treatment on the pipe section to be measured, (3) selecting a portion at one end of the pipe section to be measured, taking the portion as a starting point to measure the thickness along the axial direction and finding the thinnest point, marking it as point 1, (4) taking point 1 as a center point and measuring the thickness along the circumferential direction to both sides, finding the thinnest point, marking it as point 2, (5) taking point 2 as a center point and measuring along the axial direction to both sides, finding the thinnest point, marking it as point 3, (6) repeating the above operations and finding the thinnest point of the pipeline, and (7) calculating the corrosion rate of the pipeline and determining the detection frequency of the pipeline.

Description

Technical Field

[0001] The invention relates to the technical field of pipeline detection, and in particular to a method for formulating detection frequency of corroded pipelines. Background Art

[0002] Pipeline corrosion is one of the most common problems in the production process of high-risk industries such as oil and gas extraction, petroleum refining, and chemical synthesis. At present, the existing regular inspection of corroded pipelines is mostly annual shutdown maintenance inspection, but for the parts of the pipeline that are more severely corroded, the inspection time needs to be shortened to prevent pipeline damage and oil and gas leakage. Since the degree of corrosion of the pipeline is difficult to determine from the outside, the staff is required to regularly measure the pipeline to determine the degree of corrosion of the pipeline and repair and maintain the pipeline that has reached a certain degree of corrosion. However, the traditional regular inspection method of corroded pipelines requires the staff to inspect the entire section of the pipeline, which leads to a large workload and low work efficiency for the staff. The staff cannot quickly measure the thinnest point of the corroded pipeline, which seriously affects the inspection efficiency of the pipeline. Summary of the invention

[0003] In view of this, the present invention provides a method for formulating the detection frequency of corroded pipelines to solve the above-mentioned problems.

[0004] The technical solution adopted by the present invention to solve its technical problem is:

[0005] A method for determining the frequency of inspection of a corroded pipeline comprises the following steps:

[0006] (1) Select the pipe section that is susceptible to corrosion in the pipeline, which is the pipe section to be measured;

[0007] (2) Surface treatment of the pipe section to be measured;

[0008] (3) Select four locations at one end of the pipe section to be measured, and measure the thickness at the same interval X along the axial direction of the pipe section to be measured, starting from one end of each location. When two data points rise continuously, stop measuring the thickness, find the thinnest point on the axial direction and mark it as point 1;

[0009] (4) With point 1 as the center point, measure the thickness on both sides of the pipe section to be measured at the same interval X along the circumference. When two data points rise continuously, stop measuring the thickness, find the thinnest point on the circumference and mark it as point 2;

[0010] (5) With point 2 as the center point, measure the thickness on both sides of the pipe section to be measured at the same interval X along the axial direction. When two data points rise continuously, stop measuring the thickness, find the thinnest point on the axial direction and mark it as point 3;

[0011] (6) Measure the distance between point 2 and point 3. When the distance between point 2 and point 3 is equal to the length of interval X, point 3 is the thinnest point of the pipe to be measured, and the operation is stopped;

[0012] (7) When the distance between point 2 and point 3 is greater than the length of the interval X, continue to use point 3 as the center point and repeat at least one step from step (4) to step (6) until the interval between two consecutive thinnest points is X, thereby finding the thinnest point of the pipe section to be measured;

[0013] (8) Take the thinnest point data of the pipe section to be measured twice with a certain time interval, and calculate the corrosion rate of the pipeline based on the thickness difference obtained from the two measurements and the time interval between the two measurements. According to the corrosion rate of the pipeline, the inspection frequency of the pipeline is determined.

[0014] Furthermore, the pipe sections susceptible to corrosion in step (1) include: high-temperature pipeline equipment, parts susceptible to hydrochloric acid corrosion, parts susceptible to wet hydrogen sulfide corrosion, parts susceptible to alkali corrosion, parts with cavitation, parts susceptible to liquid water formation in low-temperature condensation areas, parts with high temperatures and organic acids, parts with high pipeline flow rates and severe corrosion and erosion, and dead corners.

[0015] Furthermore, the selection of the pipe section to be measured in the step (1) includes, according to the pipeline structure: selecting the reducer position for the reducer, selecting the elbow and the range of the rear connecting pipe portion for the elbow, selecting the range of the rear connecting pipe portion for the valve, selecting the branch pipe section where the main pipeline is located and the range of the two branch pipe joints for the tee, selecting the manifold section where the pipeline is located, selecting the branch pipe section where the branch pipe is located, and selecting the section centered on the branch pipe for the pipeline with an instrument branch pipe.

[0016] Furthermore, the length of the pipe section to be measured in step (1) is 10-30 cm.

[0017] Furthermore, the surface treatment of the pipe section to be measured in step (2) comprises the following steps:

[0018] Use a brush or file to remove loose scale, rust, dirt, and coating on the surface of the pipe section to make the measuring point smooth.

[0019] Furthermore, the interval X distance in step (3) is 1-3 cm.

[0020] Furthermore, the selected parts of the pipe section to be measured in the step (3) include, according to the type of the pipe section to be measured: for curved pipes, the outer bend, inner bend, right side, and left side are selected; for straight pipe sections and reducers, the upper surface, lower surface, left surface, and right surface are selected; for tee pipes, the opposite side and two side surfaces of the branch pipe are selected; and for branch pipes, two side surfaces are selected.

[0021] Furthermore, the corrosion rate calculation formula in step (8) is:

[0022]

[0023] Furthermore, the standard for establishing the pipeline inspection frequency in step (8) is as follows: strength check and maintenance are performed on pipe sections with a thinning rate greater than or equal to 40%, monthly measurement is performed on pipe sections with a corrosion rate greater than 0.5 mm / a or a thinning rate greater than or equal to 30% and less than 40%, and measurement is performed once every three months on pipe sections with a corrosion rate between 0.254 and 0.5 mm / a or a thinning rate greater than or equal to 20% and less than 30%; measurement is performed once every six months on pipe sections with a corrosion rate between 0.125 and 0.254 mm / a or a thinning rate greater than or equal to 10% and less than 20%, and measurement is performed once a year on pipe sections with a corrosion rate less than 0.125 mm / a or a thinning rate less than 10%.

[0024] The beneficial effects of the present invention are:

[0025] The method for formulating the detection frequency of a corroded pipeline provided by the present invention selects a corrosion-prone pipe section of the pipeline, selects four positions at one end of the pipe section to be measured, takes one end of each position as a starting point, performs detection at a certain interval along the axial direction of the pipe section to be measured, finds the thinnest point in the axial direction, and then takes the point as the center and performs thickness measurement at a certain interval along the circumferential direction to both sides, thereby quickly determining the thinnest point of the corrosion-prone pipe section in the pipeline, reducing the number of single measurement points of the pipeline, and reducing the workload of pipeline thickness measurement. At the same time, the staff can calculate the corrosion rate of the pipe section according to the thickness difference obtained by two measurements and the interval time between the two measurements, thereby determining the detection frequency of the pipeline, ensuring timely maintenance of the pipeline, reducing the risk of pipeline use, and extending the service life of the pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of a measuring method of a pipe section to be measured according to the present invention;

[0027] Figure 2 for Figure 1 A schematic diagram of a measuring method of a pipe section to be measured according to the present invention is shown;

[0028] Figure 3 for Figure 2 A schematic diagram of a measuring method of a pipe section to be measured according to the present invention is shown;

[0029] Figure 4 for Figure 1 A schematic diagram of four locations of a pipe section to be measured according to the present invention is shown. DETAILED DESCRIPTION

[0030] The present invention will now be described in detail with reference to the accompanying drawings. This figure is a simplified schematic diagram, which only illustrates the basic structure of the present invention in a schematic manner, and therefore only shows the components related to the present invention.

[0031] Please refer to Figure 1 The method for formulating the detection frequency of corroded pipelines of the present invention comprises the following steps:

[0032] (1) Select the pipe section that is susceptible to corrosion in the pipeline, that is, the pipe section to be measured; wherein the pipe section susceptible to corrosion includes: high-temperature pipeline equipment, parts susceptible to hydrochloric acid corrosion, parts susceptible to wet hydrogen sulfide corrosion, parts susceptible to alkali corrosion, parts with cavitation, parts susceptible to liquid water in low-temperature condensation areas, parts with organic acids and high temperatures, parts with high pipeline flow rates and severe corrosion and erosion, and dead corners; the selection of the pipe section to be measured includes: selecting the reducer position for the reducer, selecting the elbow and the range of the rear pipe section for the elbow, selecting the range of the rear pipe section for the valve, selecting the branch section where the main pipeline is located and the range of the two branch pipe joints for the tee, selecting the pipe section where the pipeline is located, selecting the pipe section where the branch pipe is located, and selecting the pipe section centered on the branch pipe for the pipeline with instrument branches; the length of the pipe section to be measured is 10-30 cm.

[0033] (2) Perform surface treatment on the pipe section to be measured. Use a brush or file to remove loose oxide scale, rust, dirt, and coating on the surface of the pipe section to make the measuring point smooth.

[0034] (3) Select four locations at one end of the pipe section to be measured, and take one end of each location as the starting point according to Figure 1 The thickness measurement method shown is to measure the thickness at the same interval X along the axial direction of the pipe section to be measured, wherein: Figure 1 The arrow in the figure indicates the measurement direction. Figure 1 The dots in the figure represent the measuring points. When two data points rise continuously, stop the thickness measurement, find the thinnest point in the axis direction and mark it as point 1. The selected parts of the pipe section to be measured include: outer bend, inner bend, right side and left side for curved pipes; upper surface, lower surface, left surface and right surface for straight pipe sections and reducers; opposite side and two side surfaces for tees; and two side surfaces for branch pipes.

[0035] (4) With point 1 as the center point, measure the thickness on both sides of the pipe section to be measured at the same interval X along the circumference. When two data points rise continuously, stop measuring the thickness, find the thinnest point on the circumference and mark it as point 2.

[0036] (5) With point 2 as the center point, measure the thickness on both sides of the pipe section to be measured at the same interval X along the axial direction. When two data points rise continuously, stop measuring the thickness, find the thinnest point on the axial direction and mark it as point 3.

[0037] (6) Measure the distance between point 2 and point 3. When the distance between point 2 and point 3 is equal to the length of interval X, point 3 is the thinnest point of the pipe section to be measured and the operation is stopped.

[0038] (7) Please refer to Figure 2 When the distance between point 2 and point 3 is greater than the length of interval X, continue to measure the thickness on both sides of the pipe section to be measured at the same interval X along the circumference of the pipe section to be measured with point 3 as the center point. When two data rise continuously, stop the thickness measurement, find the thinnest point on the circumference and mark it as point 4, measure the distance between point 3 and point 4, when the distance between point 3 and point 4 is equal to the length of interval X, point 4 is the thinnest point of the pipe section to be measured, and stop the operation.

[0039] (8) Please refer to Figure 3 When the distance between point 3 and point 4 is greater than the length of interval X, continue to measure the thickness of the pipe section to be measured at the same interval X along the axial direction of the pipe section to be measured with point 4 as the center point. When two data rise continuously, stop measuring the thickness, find the thinnest point on the axial direction and mark it as point 5, measure the distance between point 5 and point 4, when the distance between point 5 and point 4 is equal to the length of interval X, point 5 is the thinnest point of the pipe section to be measured, and stop the operation. When the distance between point 4 and point 5 is greater than the length of interval X, continue to repeat at least one step from step (4) to step (6) with point 5 as the center point until the distance between two consecutive thinnest points is X, and the thinnest point of the pipe section to be measured can be found.

[0040] (9) Record the measurement data, and calculate the corrosion rate of the pipeline based on the thickness difference obtained from the two measurements and the interval between the two measurements. According to the corrosion rate of the pipeline, determine the inspection frequency of the pipeline; the corrosion rate calculation formula is:

[0041]

[0042] The standard for pipeline inspection frequency is as follows: strength verification and maintenance shall be carried out on pipe sections with a thinning rate greater than or equal to 40%, monthly measurement shall be carried out on pipe sections with a corrosion rate greater than 0.5mm / a or a thinning rate greater than or equal to 30% and less than 40%, and measurement shall be carried out on pipe sections with a corrosion rate between 0.254-0.5mm / a or a thinning rate greater than or equal to 20% and less than 30% every three months; measurement shall be carried out on pipe sections with a corrosion rate between 0.125-0.254mm / a or a thinning rate greater than or equal to 10% and less than 20% every six months, and measurement shall be carried out on pipe sections with a corrosion rate less than 0.125mm / a or a thinning rate less than 10% every year.

[0043] Wherein, the length of the interval X in steps (3) to (8) is 1-3 cm.

[0044] Example

[0045] This embodiment measures the pipe wall thickness of a certain company's atmospheric and vacuum distillation unit, and the specific operation process includes the following steps:

[0046] (1) Thirty-two high-risk points in the pipeline of the company's atmospheric and vacuum distillation unit were selected, and the thickness of the three most susceptible to corrosion among the 32 high-risk points was measured. The three sections were: the P-40 pump sweep elbow, the P-32 outlet sweep elbow, and the P-44 inlet elbow.

[0047] (3) Use a brush or file to remove loose scale, rust, dirt, and coating from the surface of these three pipe sections to ensure that the measuring points are flat.

[0048] (4) Select the test part of the P-40 pump sweep elbow, first measure the outer curved surface at intervals of 2 cm and record the readings. Figure 1 The steps shown in the figure are used to measure and record the maximum thinning point of the outer bend test thick point, and then the inner bend, left side and right side areas are measured continuously. The maximum thinning reading of 3.11mm (thinning percentage 22.3%) in the inner bend, outer bend, left side and right side is recorded, and the maximum thinning point is marked on the pipeline for the convenience of the next measurement. According to the same test steps, the maximum thinning reading of the P-32 outlet steam sweep line elbow is 2.54mm (thinning percentage 36.5%), and the maximum thinning reading of the P-44 inlet elbow is 6.6mm (thinning percentage 17.5%).

[0049] (5) Measurement data recording: The measured data shall be recorded in Table 1. According to the thinning ratio, the measurement frequency of the P-40 pump sweep elbow shall be determined to be 3 months / time, the measurement frequency of the P-32 outlet steam sweep elbow shall be determined to be 1 month / time, and the measurement frequency of the P-44 inlet elbow shall be determined to be 6 months / time. According to the specified measurement frequency, the removable insulation cover shall be removed. Three months after the last measurement, the maximum thinning part of the P-32 outlet steam sweep elbow shall be measured and the readings shall be recorded. One month later, the maximum thinning part of the P-32 outlet steam sweep elbow shall be measured and the readings shall be recorded. Six months later, the maximum thinning part of the P-44 inlet elbow shall be read, and the maximum thinning percentage and corrosion rate shall be calculated. The maximum thinning reading, maximum thinning percentage and corrosion rate shall be recorded in Table 1.

[0050] Table 1 Measurement and investigation of atmospheric and vacuum distillation unit

[0051]

[0052]

[0053] As can be seen from Table 1, the method for formulating the detection frequency of the corroded pipeline provided by the present invention is adopted in this embodiment. By selecting three easily corroded pipe sections, namely, the P-40 pump sweeping elbow, the P-32 outlet sweeping elbow and the P-44 inlet elbow in the atmospheric and vacuum distillation device, the inner bend, the outer bend, the left side and the right side on the three pipe sections are detected at a certain interval along the axial direction of the pipe section to be measured, and the thinnest point in the axial direction is found. Then, the thickness is measured at a certain interval along the circumferential direction to both sides with the thinnest point in the axial direction as the center, so that the thinnest point of the easily corroded pipe section in the pipeline can be quickly determined, the coverage range of a single measurement of the pipeline is reduced, and the workload of the pipeline thickness measurement is reduced. At the same time, the staff can determine the detection frequency of the pipeline according to the thinning ratio, and calculate the corrosion rate of the pipe section by the thickness difference obtained by the two measurements and the interval time between the two measurements, so as to ensure timely maintenance of the pipeline, reduce the risk of pipeline use, and extend the service life of the pipeline.

[0054] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the scope of the present invention through the above description. The technical scope of this invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for determining the frequency of detection of corroded pipelines, characterized in that: The following steps are involved: (1) Select the pipe section that is susceptible to corrosion in the pipeline, which is the pipe section to be measured; (2) Surface treatment of the pipe section to be measured; (3) Select four locations at one end of the pipe section to be measured, and measure the thickness at the same interval X along the axial direction of the pipe section to be measured, starting from one end of each location. When two data points rise continuously, stop measuring the thickness, find the thinnest point on the axial direction and mark it as point 1; (4) With point 1 as the center point, measure the thickness on both sides of the pipe section to be measured at the same interval X along the circumference. When two data points rise continuously, stop measuring the thickness, find the thinnest point on the circumference and mark it as point 2; (5) With point 2 as the center point, measure the thickness on both sides of the pipe section to be measured at the same interval X along the axial direction. When two data points rise continuously, stop measuring the thickness, find the thinnest point on the axial direction and mark it as point 3; (6) Measure the distance between point 2 and point 3. When the distance between point 2 and point 3 is equal to the length of interval X, point 3 is the thinnest point of the pipe to be measured, and the operation is stopped; (7) When the distance between point 2 and point 3 is greater than the length of the interval X, continue to use point 3 as the center point and repeat at least one step from step (4) to step (6) until the interval between two consecutive thinnest points is X, thereby finding the thinnest point of the pipe section to be measured; (8) Take the thinnest point data of the pipe section to be measured twice with a certain time interval, and calculate the corrosion rate of the pipeline based on the thickness difference obtained from the two measurements and the time interval between the two measurements. According to the corrosion rate of the pipeline, the inspection frequency of the pipeline is determined.

2. The method for determining the detection frequency of corroded pipelines according to claim 1, characterized in that: The pipe sections susceptible to corrosion in step (1) include: high-temperature pipeline equipment, parts susceptible to hydrochloric acid corrosion, parts susceptible to wet hydrogen sulfide corrosion, parts susceptible to alkali corrosion, parts with cavitation, parts susceptible to liquid water formation in low-temperature condensation areas, parts with high temperatures and organic acids, parts with high pipeline flow rates and severe corrosion and erosion, and dead corners.

3. The method for determining the detection frequency of corroded pipelines according to claim 1, characterized in that: The selection of the pipe section to be measured in the step (1) includes, according to the pipeline structure: selecting the reducer at the reducer position, selecting the elbow and the range of the rear pipe connection portion for the elbow, selecting the range of the rear pipe connection portion for the valve, selecting the branch pipe section where the main pipeline is located and the range of the two branch pipe joints for the tee, selecting the manifold section where the pipeline is located, selecting the branch pipe section where the branch pipe is located for the branch pipe, and selecting the section centered on the branch pipe for the pipeline with an instrument branch pipe.

4. The method for determining the detection frequency of corroded pipelines according to claim 1, characterized in that: The length of the pipe section to be measured in step (1) is 10-30 cm.

5. The method for determining the detection frequency of corroded pipelines according to claim 1, characterized in that: The surface treatment of the pipe section to be measured in step (2) comprises the following steps: Use a brush or file to remove loose scale, rust, dirt, and coating on the surface of the pipe section to make the measuring point smooth.

6. The method for determining the detection frequency of corroded pipelines according to claim 1, characterized in that: The interval X distance in step (3) is 1-3 cm.

7. The method for determining the detection frequency of corroded pipelines according to claim 1, characterized in that: The selected parts of the pipe section to be measured in the step (3) include, according to the type of the pipe section to be measured: for curved pipes, the outer bend, inner bend, right side, and left side are selected; for straight pipe sections and reducers, the upper surface, lower surface, left surface, and right surface are selected; for tees, the opposite side and two side surfaces of the branch pipe are selected; and for branch pipes, two side surfaces are selected.

8. The method for determining the detection frequency of corroded pipelines according to claim 1, characterized in that: The corrosion rate calculation formula in step (8) is:

9. The method for determining the detection frequency of corroded pipelines according to claim 1, characterized in that: The standard for the pipeline inspection frequency in step (8) is as follows: strength check and maintenance are performed on pipe sections with a thinning rate greater than or equal to 40%, monthly inspection is performed on pipe sections with a corrosion rate greater than 0.5 mm / a or a thinning rate greater than or equal to 30% and less than 40%, and once every three months is performed on pipe sections with a corrosion rate between 0.254 and 0.5 mm / a or a thinning rate greater than or equal to 20% and less than 30%; once every six months is performed on pipe sections with a corrosion rate between 0.125 and 0.254 mm / a or a thinning rate greater than or equal to 10% and less than 20%, and once a year is performed on pipe sections with a corrosion rate less than 0.125 mm / a or a thinning rate less than 10%.

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