Method for predicting service life of long-distance coal conveying pipeline

Abstract

The invention discloses a method for predicting the service life of a long-distance coal conveying pipeline. The method comprises the following specific steps: step 1, selecting an easily-corroded part in the long-distance coal conveying pipeline as a key detection position; step 2, performing contact type quantitative detection on the pipe body at the key detection position in the step 1, obtaining the maximum abrasion depth d of the pipeline at each key detection position, and calculating the maximum abrasion rate r of the pipeline according to the maximum abrasion depth d of the pipeline; 3, calculating the minimum allowable wall thickness t of the pipeline at each key detection position in the step 1; 4, calculating the service life of the pipeline at each key detection position according to the maximum abrasion rate r of the pipeline and the minimum allowable wall thickness t of the pipeline, and selecting the minimum service life as the service life N of the long-distance pipeline; the method does not need to excavate and backfill all pipelines, is low in detection cost, does not damage the pipelines, does not need to stop production, and does not affect normal production operation.

Description

Technical Field

[0001] The invention belongs to the technical field of pipeline life prediction and relates to a method for predicting the service life of a long-distance coal transportation pipeline. Background Art

[0002] Existing coal pipelines have been in service for a long time in a flowing water-coal slurry environment. Under the coupling effect of erosion and abrasion of flowing coal powder particles and electrochemical corrosion of the transport medium, it is very easy to cause corrosion damage to the inner wall of the pipeline. In order to ensure the long-term safe and stable operation of the pipeline, it is necessary to accurately predict the service life of the pipeline. The traditional method is to predict the service life of the pipeline by obtaining accurate and comprehensive corrosion detection data. However, the pipelines of long-distance coal pipelines are long and buried in trenches underground. If the traditional method is used, all pipelines need to be fully excavated to obtain accurate and comprehensive corrosion detection data. The excavation is difficult and the cost required is extremely high. In addition, the pipelines are easily damaged during the excavation and backfilling process, causing production suspension and affecting normal production operations. Therefore, for long-distance coal pipelines, their corrosion conditions and service life are difficult to detect and predict. Summary of the invention

[0003] The purpose of the present invention is to provide a method for predicting the service life of a long-distance coal transportation pipeline, which solves the problem in the prior art that the corrosion of the long-distance coal transportation pipeline and the service life are difficult to detect and predict.

[0004] The technical solution adopted by the present invention is a method for predicting the service life of a long-distance coal transportation pipeline, and the specific steps are as follows: Step 1: Select the easily corroded parts in the long-distance coal transportation pipeline as the key detection locations; Step 2, carry out contact quantitative detection on the pipe body at the key detection position in step 1, obtain the maximum abrasion depth d of the pipeline at each key detection position, and calculate the maximum abrasion rate r of the pipeline according to the maximum abrasion depth d of the pipeline; Step 3, calculating the minimum allowable wall thickness t of the pipeline at each key detection position in step 1; Step 4: Calculate the service life of the pipeline at each key inspection location based on the maximum pipeline abrasion rate r and the minimum allowable pipeline wall thickness t, and select the minimum service life as the long-distance pipeline service life N.

[0005] The present invention is also characterized in that: The specific operations of step 1 are as follows: Select any one or more locations among the entrances and exits of the booster pump stations distributed on the long-distance coal pipeline trunk lines and branch lines, pressure monitoring points, shut-off valve chambers, exhaust valve chambers, energy dissipation stations, and diameter change points as key inspection locations.

[0006] The specific steps of contact quantitative detection in step 2 are as follows: Step 2.1, remove the anti-corrosion layer of the pipeline at the key detection position in step 1, and then clean and remove rust from the pipe body after the anti-corrosion layer is removed; Step 2.2, using an ultrasonic scanning device to perform ultrasonic circumferential corrosion linear scanning on the pipe body cleaned in step 2.1; In step 2.2, the number of ultrasonic circumferential corrosion linear scans is no less than 3 circles, and the ultrasonic scanning device uses any one of an ultrasonic C scanner or an ultrasonic phased array combined wall thickness detector.

[0007] Step 2.3: After the scanning in step 2.2 is completed, the insulation layer is re-installed on the pipe body of the inspected pipeline.

[0008] The specific method for calculating the maximum abrasion rate r of the pipeline in step 2 is as follows:

[0009] Where: r is the maximum abrasion rate of the pipeline, unit: mm / a; T is the wall thickness of the pipe at the location of maximum abrasion, in mm; is the maximum corrosion depth of the pipeline, in mm; W represents the annual transportation volume of raw coal, in Wt; Q is the raw coal delivery volume, unit is Wt.

[0010] The calculation method of the minimum allowable pipe wall thickness t in step 3 is as follows: The minimum allowable wall thickness of the pipeline is calculated simultaneously using the abrasion allowance calculation method and the pipeline pressure calculation method. The two values ​​obtained are compared and the maximum value is selected as the minimum allowable wall thickness t of the pipeline at the key inspection position in step 1.

[0011] The specific calculation method of abrasion allowance is:

[0012] Where: t is the minimum allowable wall thickness of the steel pipe, in mm; is the designed wall thickness of the pipe, in mm; C is the 30-year abrasion allowance of the pipeline, in mm.

[0013] The specific method for calculating pipeline pressure is as follows:

[0014] Where: t is the minimum allowable wall thickness of the steel pipe, in mm; P is the maximum pressure of the pipeline, unit: MPa; D is the outer diameter of the pipe, in mm; K is the design coefficient, which is 0.72 in general areas and 0.6 in urban suburbs and station areas; It is the minimum yield strength of the pipe, in MPa. According to GB9711 standard, the value of L450 steel pipe is 450; It is the weld coefficient of the pipe and is 1 for steel pipes manufactured according to GB9711 standard.

[0015] The specific method for calculating the service life of pipelines at each key detection location in step 4 is as follows:

[0016] Where: N is the service life of the long-distance pipeline; T is the wall thickness of the pipe at the location of maximum abrasion; t is the minimum allowable wall thickness of the pipe; r is the maximum abrasion rate.

[0017] The beneficial effects of the present invention are: The present invention selects the easily corroded parts of the pipeline as the key detection positions of the long-distance coal transportation pipeline, does not need to excavate and backfill the entire pipeline, has low detection cost, does not damage the pipeline, does not need to stop production, and does not affect normal production operation; the present invention calculates the service life N of the long-distance pipeline according to the maximum abrasion rate r of the pipeline and the minimum allowable wall thickness t of the pipeline, has a wide range of applications, and can perform on-site prediction of the service life of any long-distance solid-liquid two-phase flow transmission pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flow chart of a method for predicting the service life of a long-distance coal transportation pipeline according to the present invention; Figure 2 This is a schematic diagram of key detection positions in the method for predicting the service life of a long-distance coal pipeline of the present invention; Figure 3 It is a schematic diagram of contact quantitative detection in the method for predicting the service life of a long-distance coal transportation pipeline of the present invention. DETAILED DESCRIPTION

[0019] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] The method for predicting the service life of a long-distance coal transportation pipeline of the present invention comprises the following specific steps: Step 1: Figure 1 As shown in the figure, the parts of the long-distance coal transportation pipeline that are prone to corrosion are selected as the key inspection locations of the long-distance coal transportation pipeline, for example: Figure 2 As shown in the figure, C1 and C2 are the key detection locations of long-distance coal pipelines.

[0021] Preferably, the key detection positions are selected from any one or more of the entrances and exits of the booster pump stations distributed on the long-distance coal pipeline trunk lines and branch lines, pressure monitoring points, shut-off valve chambers, exhaust valve chambers, energy dissipation stations, and diameter change points.

[0022] Among them, the pressure monitoring points are set at the highest and lowest points of the pipeline. After the long-distance coal pipeline has been running for a period of time, the convex end of the high-point bend will be more seriously corroded than the straight pipe, and the concave end of the low point will be more seriously corroded than the convex end of the high point. Therefore, this place can be selected as the key detection position.

[0023] The pipelines in the booster pump station are installed in an exposed manner. No excavation or backfilling is required during inspection. Therefore, this area can be selected as the key inspection location.

[0024] The shut-off valve chamber is generally open. In order to prevent coal slurry from polluting cities and rivers when accidents occur in long-distance pipelines, a shut-off valve chamber is usually installed where the pipeline passes through densely populated counties or upstream and downstream of rivers. This place is very likely to cause blockage accidents and cause pipeline corrosion. Therefore, this place can be selected as the key inspection location.

[0025] The exhaust valve chamber is usually built after the coal transportation pipeline system is established. The pipelines along the line need to be filled with water for exhaust. It is usually an exposed installation. No excavation or backfilling is required during inspection. Therefore, this place can be selected as the key inspection location.

[0026] The energy dissipation station and the diameter change point are set to prevent the pipeline from being hollowed out or producing accelerated flow under high drop. They are prone to corrosion and therefore can be selected as key inspection locations.

[0027] The key inspection locations of the above-mentioned long-distance coal pipelines are pipelines that are prone to corrosion and are installed in an exposed manner. The corrosion data is convenient for inspection, and there is no need to excavate and backfill all pipelines. The inspection cost is low, and the pipelines will not be damaged. There is no need to stop production, and normal production operations will not be affected. This effectively solves the problem of the difficulty in detecting corrosion in long-distance coal pipelines. The service life of long-distance coal pipelines can be predicted based on the inspection data in the future, which effectively solves the problem of the difficulty in predicting the service life of long-distance coal pipelines.

[0028] Step 2, carry out contact quantitative detection on the pipe body at the key detection position in step 1, obtain the maximum abrasion depth d of the pipeline at each key detection position, and calculate the maximum abrasion rate r of the pipeline according to the maximum abrasion depth d of the pipeline; The specific steps of contact quantitative detection in step 2 are as follows: Step 2.1, remove the anti-corrosion layer of the pipeline at the key inspection position in step 1, and then clean and remove rust from the pipe body after the anti-corrosion layer is removed, for example: Figure 3 As shown, C1 and C2 in the figure are long-distance coal transportation pipelines where the anti-corrosion layer has been removed; Step 2.2, using an ultrasonic scanning device to perform ultrasonic circumferential corrosion linear scanning on the pipe body cleaned in step 2.1; In step 2.2, the number of ultrasonic circumferential corrosion linear scans is no less than 3 circles, and the ultrasonic scanning device uses any one of an ultrasonic C scanner or an ultrasonic phased array combined wall thickness detector.

[0029] The specific method for calculating the maximum abrasion rate r of the pipeline in step 2 is as follows: (1) Where: r is the maximum abrasive rate of the pipeline mm / a; T is the wall thickness of the pipe at the location of maximum abrasion, in mm; is the maximum corrosion depth of the pipeline, in mm; W represents the annual transportation volume of raw coal, in units of Wt; the designed annual transportation volume of long-distance coal pipelines is usually 10 million tons; Q is the raw coal delivery volume, unit is Wt.

[0030] Step 2.3: After the scanning in step 2.2 is completed, the insulation layer is re-installed on the pipe body of the inspected pipeline.

[0031] Step 3, calculating the minimum allowable wall thickness t of the pipeline at each key detection position in step 1; The calculation method of the minimum allowable pipe wall thickness t in step 3 is as follows: The minimum allowable wall thickness of the pipeline is calculated simultaneously using the abrasion allowance calculation method and the pipeline pressure calculation method. The two values ​​obtained are compared and the maximum value is selected as the minimum allowable wall thickness t of the pipeline at the corresponding key inspection position in step 1.

[0032] The specific calculation method of abrasion allowance is as follows: (2) Where t is the minimum allowable wall thickness of the steel pipe, in mm; is the designed wall thickness of the pipe, in mm; C is the 30-year abrasion allowance of the pipeline, in mm.

[0033] The specific method for calculating pipeline pressure is as follows: (3) Where: t is the minimum allowable wall thickness of the steel pipe, in mm; P is the maximum pressure of the pipeline, unit: MPa; D is the outer diameter of the pipe, in mm; K is the design coefficient, which is 0.72 in general areas and 0.6 in urban suburbs and station areas; The minimum allowable wall thickness of the pipeline is calculated simultaneously by the abrasion allowance calculation method and the pipeline pressure calculation method, and the two values ​​are compared. The maximum value is selected as the minimum allowable wall thickness t of the pipeline at the key detection position in step 1. By using two methods for calculating the minimum allowable wall thickness t of the pipeline at the same time, they are mutually verified, and the maximum value is selected to participate in the prediction of the service life N of the long-distance pipeline. The final service life of the pipeline is shorter, avoiding premature corrosion of the pipeline due to the predicted service life of the long-distance pipeline being too long.

[0034] Step 4: Calculate the service life N of the long-distance pipeline based on the maximum pipeline abrasion rate r and the minimum allowable pipeline wall thickness t.

[0035] The specific method for calculating the service life of pipelines at each key detection location in step 4 is as follows: (4) Where: N is the service life of the long-distance pipeline; T is the wall thickness of the pipe at the location of maximum abrasion; t is the minimum allowable wall thickness of the pipe; r is the maximum abrasion rate.

[0036] The invention calculates the service life N of a long-distance pipeline according to the maximum abrasion rate r of the pipeline and the minimum allowable wall thickness t of the pipeline, has a wide application range, and can perform on-site prediction of the service life of any long-distance solid-liquid two-phase flow transmission pipeline.

[0037] The method for predicting the service life of a long-distance coal transportation pipeline of the present invention is specifically implemented as follows: Example 1 In this embodiment, the shutoff valve chamber 1 is selected as the key detection position, and 8 measurement points are randomly selected at this position for measurement, as shown in Table 1 below: Table 1 Measurement point selection table for cut-off valve chamber 1

[0038] By measuring each point in Table 1 above, the maximum pipeline abrasion rate r and the minimum allowable pipeline wall thickness t are calculated according to the measurement results, and the service life N of the long-distance pipeline is predicted, as shown in Table 2 below: Table 2 Service life N of the long-distance pipeline where the cut-off valve chamber 1 is located

[0039] Example 2 In this embodiment, the shutoff valve chamber 2 is selected as the key detection position, and 8 measurement points are randomly selected at this position for measurement, as shown in Table 3 below: Table 3 Measurement point selection table for cut-off valve chamber 2

[0040] By measuring each point in Table 3 above, the maximum pipeline abrasion rate r and the minimum allowable pipeline wall thickness t are calculated according to the measurement results, and the service life N of the long-distance pipeline is predicted, as shown in Table 4 below: Table 4 Service life N of long-distance pipeline where cut-off valve chamber 2 is located

[0041] Example 3 In this embodiment, the shutoff valve chamber 1 and the pressure monitoring point are selected as key detection positions, and 8 measurement points are randomly selected at the locations of the shutoff valve chamber 1 and the pressure monitoring point for measurement, as shown in Table 5 and Table 6 below: Table 5 Measurement point selection table for cut-off valve chamber 1

[0042] Table 6 Measurement point selection table for pressure monitoring points

[0043] By measuring the various points in Tables 5 and 6 above, the maximum pipeline abrasion rate r and the minimum allowable pipeline wall thickness t are calculated based on the measurement results, and the service life N of the long-distance pipeline is predicted, as shown in Table 6 below: Table 7 Service life N of the long-distance pipeline where the cut-off valve chamber 1 and the pressure monitoring point are located

[0044] It can be seen from the above-mentioned Examples 1, 2 and 3 that by selecting the cut-off valve chamber 1, the cut-off valve chamber 2, and the pressure monitoring point as the key detection positions, it is not necessary to excavate and backfill all pipelines, the detection cost is low, and the pipeline is not damaged, there is no need to stop production, and the normal production operation is not affected. At the same time, it can be seen from the above-mentioned Examples 1 and 2 that the service life of the long-distance coal transportation pipeline can be clearly calculated for different key detection positions by the method for predicting the service life of the long-distance coal transportation pipeline of the present invention, which effectively solves the problem of the difficulty in predicting the service life of the long-distance coal transportation pipeline. At the same time, it can be seen from Examples 1 and 2, combined with Example 3, that by detecting the key detection positions, the estimated service life finally predicted is different. In order to avoid the predicted service life of the long-distance pipeline being too large, which leads to the phenomenon of premature corrosion of the pipeline, the minimum pipeline service life is usually selected as the final predicted service life of the long-distance pipeline.

Claims

1. A method for predicting the service life of a long-distance coal pipeline, characterized in that: The specific steps are as follows: Step 1: Select the easily corroded parts in the long-distance coal transportation pipeline as the key detection locations; Step 2, carry out contact quantitative detection on the pipe body at the key detection position in step 1, obtain the maximum abrasion depth d of the pipeline at each key detection position, and calculate the maximum abrasion rate r of the pipeline according to the maximum abrasion depth d of the pipeline; Step 3, calculating the minimum allowable wall thickness t of the pipeline at each key detection position in step 1; Step 4: Calculate the service life of the pipeline at each key inspection location based on the maximum pipeline abrasion rate r and the minimum allowable pipeline wall thickness t, and select the minimum service life as the long-distance pipeline service life N.

2. The method for predicting the service life of a long-distance coal pipeline according to claim 1, characterized in that: Step 1 The specific process is as follows: Select any one or more locations among the entrances and exits of the booster pump stations distributed on the long-distance coal pipeline trunk lines and branch lines, pressure monitoring points, shut-off valve chambers, exhaust valve chambers, energy dissipation stations, and diameter change points as key inspection locations.

3. The method for predicting the service life of a long-distance coal pipeline according to claim 1, characterized in that: The specific steps of the contact quantitative detection described in step 2 are as follows: Step 2.1, remove the anti-corrosion layer of the pipeline at the key detection position in step 1, and then clean and remove rust from the pipe body after the anti-corrosion layer is removed; Step 2.2, using an ultrasonic scanning device to perform ultrasonic circumferential corrosion linear scanning on the pipe body cleaned in step 2.1; Step 2.3: After the scanning in step 2.2 is completed, the insulation layer is re-installed on the pipe body of the inspected pipeline.

4. The method for predicting the service life of a long-distance coal pipeline according to claim 3, characterized in that: The ultrasonic circumferential corrosion linear scanning in step 2.2 is performed for no less than 3 circles, and the ultrasonic scanning device is any one of an ultrasonic C scanner or an ultrasonic phased array combined wall thickness detector.

5. The method for predicting the service life of a long-distance coal pipeline according to claim 1, characterized in that: The specific method for calculating the maximum abrasion rate r of the pipeline described in step 2 is as follows: （1） Where: r is the maximum abrasion rate of the pipeline, unit: mm / a; T is the wall thickness of the pipe at the location of maximum abrasion, in mm; is the maximum corrosion depth of the pipeline, in mm; W represents the annual transportation volume of raw coal, in Wt; Q is the raw coal delivery volume, unit is Wt.

6. The method for predicting the service life of a long-distance coal pipeline according to claim 1, characterized in that: The calculation method of the minimum allowable wall thickness t of the pipeline described in step 3 is as follows: The minimum allowable wall thickness of the pipeline is calculated simultaneously using the abrasion allowance calculation method and the pipeline pressure calculation method. The two values ​​obtained are compared and the maximum value is selected as the minimum allowable wall thickness t of the pipeline at the key inspection position in step 1.

7. The method for predicting the service life of a long-distance coal pipeline according to claim 6, characterized in that: The abrasion allowance calculation method is specifically as follows: （2） Where: t is the minimum allowable wall thickness of the steel pipe, in mm; is the designed wall thickness of the pipe, in mm; C is the 30-year abrasion allowance of the pipeline, in mm.

8. The method for predicting the service life of a long-distance coal pipeline according to claim 6, characterized in that: The pipeline pressure calculation method is specifically as follows: （3） Where: t is the minimum allowable wall thickness of the steel pipe, in mm; P is the maximum pressure of the pipeline, unit: MPa; D is the outer diameter of the pipe, in mm; K is the design coefficient, which is 0.72 in general areas and 0.6 in urban suburbs and station areas; It is the minimum yield strength of the pipe, in MPa. According to GB9711 standard, the value of L450 steel pipe is 450; It is the weld coefficient of the pipe and is 1 for steel pipes manufactured according to GB9711 standard.

9. The method for predicting the service life of a long-distance coal pipeline according to claim 1, characterized in that: The specific method for calculating the service life of the pipeline at each key detection location described in step 4 is as follows: （4） Where: N is the service life of the long-distance pipeline; T is the wall thickness of the pipe at the location of maximum abrasion; t is the minimum allowable wall thickness of the pipe; r is the maximum abrasion rate.

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