RU2671296C1 - Method of metal corrosion loss assessment in pipeline inaccessible area - Google Patents

Abstract

FIELD: fault detection.

SUBSTANCE: using to assess the corrosion losses of metal in the inaccessible pipeline section. Summary of the Invention is that they carry out an assessment of the defectiveness of the pipeline section to be monitored from the outside of a neighboring, accessible section of the same pipeline, the defect assessment is carried out by flowing electrical current directly through the controlled and adjacent sections of the pipeline, connecting a high-resistance electrical zero-indicator of high sensitivity with one end to the common interface between the two sections, and the other, forked by the end, to the other border of each of the sections – both controlled and neighboring, the contact at the connection point to the boundary of the adjacent section is moved until the zero position of the indicator is established, then the lengths of both sections are measured both by the ratio of these lengths and by the loss of metal in the neighboring section, the evaluation of which is performed by known methods, estimates the loss of metal in the inaccessible pipeline section.

EFFECT: ensuring the possibility of assessing metal losses with the smooth wear of this metal (for example, corrosive) that is outside that is inside the pipes or at the same time, both inside and outside.

1 cl, 1 dwg, 1 tbl

Description

The invention relates to non-destructive testing of pipelines, in particular, to assessing the total loss of metal in a controlled section of the pipeline.

It is a well-known method for assessing the total loss of metal by instrumental measurement (with a caliper, micrometer, etc.) of the outer diameter of the pipe in different sections of the controlled section, under the assumption that metal loss occurs only on the outside of the pipe. This method cannot be used if the outside of the pipe is not available.

It is a well-known method for evaluating the total metal loss in total from the outer and inner sides of the pipe by ultrasonic thickness measurement of the pipe walls, carried out from the outside of the pipe in different sections of the controlled section. This method cannot be used if the outside of the pipe is not available.

A known method for assessing the total loss of metal in the area inaccessible from the outside of the pipe using a crawler moving inside the pipe with a flowing liquid (for example, oil) [1, 2]. An ultrasonic thickness gauge is located in the crawler, which measures the thickness of the pipe wall in the immersion version. This method cannot be used if the inside of the pipe is not available. Even with accessibility to the inside of the pipe, it cannot be used if there is no fluid in the pipe. This method also does not apply to the control of small diameter pipes and small pipelines, due to economic inexpediency, even in the presence of liquid and internal access.

There is a method of estimating the total metal loss in a section of a pipe of small diameter inaccessible from the outside using the IRIS technology [3, 4], based on immersion ultrasonic thickness gauge. This method cannot be used if the inside of the pipe is not available. Ensuring accessibility to the inside of the pipe cannot be carried out without stopping the production process in which the pipeline is involved.

Closest to the claimed invention, under the terms of implementation, is a method for assessing metal defects in a controlled section of a pipeline that does not require access to either the outer or the inner side of the pipe wall and is carried out from the outer surface of an adjacent section of the pipeline. This method is based on an echo-pulsed ultrasonic remote control [5, 6]. For its implementation, the ultrasonic transducer located on the outer wall of the adjacent pipe section emits an ultrasonic pulse in the direction of the controlled section, filling the entire cross section of the pipe metal with ultrasound. The ultrasonic pulse reflected from the inhomogeneities of the cross section of the pipe section being monitored returns to the ultrasonic transducer and is estimated by its parameters related to the inhomogeneity of the cross section. But this method is not suitable for assessing metal losses with a smooth character of thinning of the pipe walls, because the ultrasonic pulse from the areas of smooth change in wall thickness is not reflected.

The technical result of the proposed solution is the ability to assess metal loss with a smooth nature of the wear of this metal (for example, corrosive), which is outside, inside the pipes or at the same time, inside and outside. The technical result is achieved by the fact that through a controlled (located in an inaccessible section of the pipeline) and adjacent (free from obstacles) sections of the pipeline simultaneously pass electric current; connect a high-resistance electric null indicator of high (for example, microvoltaic) sensitivity in such a way that one of its contacts is docked to the common boundary of the docking of both sections, and the other, made with a bifurcated end, to the other border of each of the sections: both monitored and neighboring . The contact at the point of connection to the border of the neighboring section (mobile contact) is moved until the indicator is in the zero position. Next, measure the lengths of both sections: both controlled and neighboring. The ratio of these lengths and the loss of metal in the neighboring section, which was estimated by known methods, assess the loss of metal in an inaccessible section of the pipeline.

The present invention provides a simple and inexpensive method for assessing metal losses in an inaccessible section of the pipeline with access to the outer surface of an adjacent section of the same pipeline. In the process of implementing the method, the integrity of the pipeline is not violated and its intended purpose does not stop.

Examples of possible practical application of the method include:

- control of a section of the pipeline passing under the highway or railway embankment, or when crossing a small river;

- control of the gas distribution pipe section passing through the concrete (or other material) wall of the apartment building.

An example of practical application. To verify the effectiveness of the proposed method, the following steps were taken.

The measurements were carried out on a pipe with an outer diameter of 27.1 mm, with an inner diameter of 21.4 mm (wall thickness - 2.85 mm), made of steel 3. The length of the pipe was 2 m. Corrosion wear was simulated in the pipe section 423 mm long the outer side, by removing part of the metal mechanically. The removal of metal was uniform along the cylindrical surface relative to the axis of the pipe and gradual thinning from the ends of the section with a length of 423 mm to its middle to an outer diameter of 23.3 mm. Changes in the outer diameter, measured with a caliper, are shown in figure 1, and the measurement data are shown in the table.

The volume of the pipe section without thinning with a length of 423 mm is equal to:

Vex = π * 423 * [(27.1 / 2) ² - (21.4 / 2) ² ] = 91780 mm ³ = 91.78 cm ³ .

The volume of the defective (thinned) pipe section with a length of 423 mm is calculated by the formula:

The ratio of the volumes of the defective and the initial sections of equal length determines the relative residual volume of the metal of the defective section:

To assess the residual metal volume of the defective area, the method proposed by the applicants connected to the pipe ends a current source made in the form of a 12V battery with a resistance of 10 Ohm connected in series. An F195 nanoammeter was used as a zero indicator. Any other null indicator with high sensitivity can be used, calibrated in amperes, volts, ohms (or in other electrical units or not calibrated at all). A high-resistance electric null indicator of microvoltaic sensitivity was connected at one end (contact) to the common interface of the docking of both sections, and the other, made with a bifurcated end, to the other border of each of the sections (both controlled and neighboring).

The contact at the point of connection to the border of the neighboring section (mobile contact) moved until the indicator was zero. Then measured the lengths of both sections - controlled and neighboring. The lengths of the sections were measured with a tape measure with an error of less than 2 mm.

The zero indication of the null indicator was recorded with the length of the adjacent section (with the initial external and internal diameters) equal to 660 mm. The relative integral estimate of the residual metal in the defective area obtained using the method proposed by the applicants is equal to:

Thus, the estimate of the residual metal in the defective section obtained using the method proposed by the applicants actually coincides (with a slight error) with the result of measuring the relative residual metal volume in the same section in a known manner. The obtained result indicates the effectiveness of the method proposed by the applicants for evaluating the residual metal in an inaccessible section of the controlled pipeline.

Between the values of OM and OOM there is a relationship: OOM≥OM. OOM is the relative residual volume of the metal; OM - a relative estimate of the residual metal (according to the claims). The approximate equality of the values of OOM and OM occurs with uniform corrosion wear.

Information sources

1. Shell - Ultrascan WM Flaw Detector [Internet, Oil-Gas Library: text with the term Flaw Detector].

2. Ultrascan M [Internet, Big Encyclopedia of Gas Oil, Flaw detector, Ultrascan M].

3. [Internet. IRIS - ultrasonic immersion echo - method with a rotating mirror], the firm "Testex".

4. [Internet. Ultrasonic flaw detectors, thickness gauges, Multiscan MS5800 Pipe Inspection Tool].

5. “Focus Teletest” - an ultrasonic system for bringing non-destructive testing of pipes to normal waves. [The Internet. Focus Teletest Pipe Monitoring System].

6. [Internet. Ultrasonic waveguide inspection of pipelines (Wavemaker 63)].

Claims (1)

A method for evaluating the corrosion loss of a metal in an inaccessible section of a pipeline, including assessing the defectiveness of a controlled section of a pipeline from the outside of an adjacent, accessible section of the same pipeline, characterized in that the assessment of defectiveness is carried out by passing an electric current directly through the controlled and neighboring sections of the pipeline, and connecting a high-resistance electric zero - an indicator of high sensitivity at one end to the common border of the docking of both sections, and at the other, forked end, to the other face each of the sections — both controlled and neighboring, and the contact at the point of connection to the border of the neighboring section is moved until the indicator is at the zero position, after which the lengths of both sections are measured both by the ratio of these lengths and by the metal loss in the neighboring section, which was estimated by known methods, assess the loss of metal in an inaccessible section of the pipeline.

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