Method for detection of disruptions of insulating cover of underground pipeline

FIELD: diagnosis and control.

SUBSTANCE: as source of electromagnetic field of cathode protection of pipeline is used. Depth of position of pipeline axis is determined on basis of magnetic transverse, longitudinal and vertical components of electromagnetic field of current of cathode protection of pipeline. longitudinal electric component of electromagnetic current field of cathode protection is measured and transverse component of electromagnetic field of current of cathode protection on the left and right from pipeline axes. Results of measurements are made normal for depth of pipeline, resistance of environment, surrounding pipeline, current force in pipeline, background components of electromagnetic fields. On basis of heightened values of normal electric components of electromagnetic field of cathode protection current position and size of disruptions of isolating cover of pipeline are detected.

EFFECT: higher efficiency.

2 dwg

 

The invention relates to the field of diagnostics and condition monitoring of pipelines, and in particular to methods for monitoring the integrity of the insulation of the pipelines under the ground.

There is a method of detecting violations of insulation coating, developed by D. Pearson in the 40-ies /1/.

According to method D. Pearson through the pipeline pass alternating current, the AC source (generator) connected to the test output of the cathodic protection system (measuring point) and a grounding electrode. In the case of defects of insulation coating at a controlled section between the pipe and the ground electrode, a voltage drop occurs, which is measured by a voltmeter. The described method is used in the measure of the damage isolation (FDI). As it approaches the defective area and accordingly increases the voltage drop in the headphones of the instrument occurs a sound, the maximum in the maximum voltage drop and approximately coincides with the projection of the defect on the earth's surface. After passing zones defective area signal gradually fades. The disadvantages of this method are:

- Difficulty in determining the location of the defective area and the size of the violation of isolation the th coverage due to the inability to accurately determine the depth of the pipeline.

- High complexity and significant financial costs due to the need of connecting the power generator to the pipeline and the availability of instrumentation points.

- When processing the results of observations does not provide a record of important parameters: the depth of the pipeline, the current in the pipeline, the background components of the electromagnetic field affecting the value measured by the method parameters.

The closest in technical essence and the achieved result is taken as a prototype relaxation method for detecting violations of the insulating coating of underground pipelines, based on the use of electromagnetic fields and is known as CIPS - Close Interval Pipe-to-Soil Potential /2/. According to the method CIPS is the analysis of changes in potential "pipe to ground when turned on, and the instantaneous current is switched off, running at intervals along the pipeline using a flexible wire connected to the measuring column (CIC) to provide electrical connections to the pipe. The physical basis of CIPS - registration of potential "pipe-to-ground using a copper sulfate electrode. The method is based on registration of potential on and off and the gradients of potential increments of 5 meters between the measuring points. The Commission is prohibited cyclic switching of the protective settings (modes: 12 - "Enable", 3 - "Off"). The axis of the pipeline is determined by the locator when connecting to the pipeline of the AC source. The fall of the stresses in the direction perpendicular to the pipeline determined relative to the external copper sulfate electrode which was placed 5 m away from the pipeline axis. As for measuring the capacity of the pipe-soil must be connected to the pipeline, then this connection is transferred from one control point to another using a cable reel. Measured potentials "pipe-to-ground and the voltage drop in the ground receive guidance on a lot of damage in the coating and an estimate of their value.

The disadvantages of this method are:

- Due to the inability to accurately determine the depth of the pipeline in this way reservation is the use of an additional device locator.

- There is no accounting for the resistance of rocks allotropes space. Not taken into account that soil, as a rule, a complex system of reservoirs and areas with different resistances.

- There is no record of important factors affecting the results of measurement of the depth of the pipeline, the current in the pipeline, the background components of the electromagnetic field that contributes significantly pogress the STI in the measurement results.

- High complexity and significant financial costs due to the need for clear cuttings cuttings width of several meters around the profile, the connection to the measuring points, the use of circuit breakers current (INTACTO) for short-term shutdown protection current with mandatory install them on all nearby cathodic protection station (RMS). Contacty must be installed on all queues of the pipeline (they need at least 12 units at chetyrekhetazhnoe pipeline system).

Significant measurement errors are also caused by the use of syntacto.

- You cannot change the spacings of the electrodes depending on the measurement conditions, which leads to skipping of violations of the insulating coating of the pipeline.

The inability of measurements in difficult ground conditions.

The technical result of the invention is increased in comparison with the prototype of the accuracy of determining the location and extent of the disruption insulation coating of underground pipelines, reducing the time of determination while reducing costs. The technical result in the known method of detection of violations of the insulating coating of underground pipelines, which consists in measuring the components of the electromagnetic field, is achieved by the fact that determined the t the depth of the pipeline axis in transverse magnetic, the longitudinal and vertical components of the electromagnetic field of the current cathodic protection of the pipeline, consistently measure the longitudinal electric component of the electromagnetic field of the current cathodic protection and the transverse component of the electromagnetic field of the current cathodic protection on the left and right of the pipe axis, normalized measurements on the depth of the pipeline, the resistance of the medium surrounding the pipeline, the current strength in the pipeline, the background components of the electromagnetic field and increased values of the normalized electric components of the electromagnetic field of the current cathodic protection determine the location and size of violations of the insulating coating of the pipeline.

Salient features of the claimed invention are the following:

- determine the depth of the pipe axis in the magnetic transverse, longitudinal and vertical components of the electromagnetic field of the current cathodic protection of the pipeline;

- along the pipeline consistently measure the longitudinal electric component of the electromagnetic field of the current cathodic protection and the transverse component of the electromagnetic field of the current cathodic protection on the left and right axis of the pipeline;

- normalized measurements on the depth of the pipeline, the resistance of the medium, the environment and the surrounding conduit, the current strength in the pipeline, the background components of the electromagnetic field;

- at higher values of the normalized electric components of the electromagnetic field of the current cathodic protection determine the location and size of violations of the insulating coating of the pipeline.

The above salient characteristics were unknown to us from the patent and scientific literature in this regard is "New".

At the same time essential characteristics are unknown to the average person skilled in the knowledge that meets the criterion of "Inventive step".

Due to the fact that the claimed method was trace test on the areas of gas "Ukhta-Torzhok" and "Gryazovets - St. Petersburg" we believe that the method meets the criterion of "Industrial applicability".

Figure 1. presents a scheme illustrating the proposed method of detection of violations of the insulating coating of underground pipelines, which shows the axis of the pipeline 1, laid in the ground 2, which are grounded reception electrodes M and N with a spacing of 5 meters.

The sensor 3 measures the electric components of the electromagnetic field of the current cathodic protection of the pipeline to determine violations of the insulation 4.

Figure 2 presents the results of measurements electricallyoperated X (Ex right and Ex left) and longitudinal (Y-EY) components of the electromagnetic field of the current cathodic protection of the pipeline.

The method is carried out in the following sequence. The sensor electromagnetic field 3 (with built-in filter 50 Hz to get rid of industrial noise) at a frequency of 100 Hz using a highly sensitive antenna system (not shown) measure the horizontal and vertical magnetic components of the electromagnetic field of the current cathodic protection.

According to the above mentioned characteristics determine the exact location and depth of the pipe axis.

Measurement of the depth of the pipe produced by the method described in [3] on str-129. The depth of the pipeline h0 is estimated by the formula:

where U1, U2 is the magnetic field strength at the measurement using 1-and 2 antennas, respectively, located to the difference of heights and, If the background field component, which is defined by the vertical antenna, r is the radius of the pipeline.

Two receiving electrodes M and N kasemset in the surface of the substrate 2 with a spacing of 5 meters, forming a line MN, which lie along the axis of the pipeline. The electrodes are connected to the sensor electromagnetic field 3 (with built-in filter 50 Hz to get rid of industrial noise). In this situation the receiving electrodes M and N sensor 3 to measure the longitudinal electric component EY of the electromagnetic field current is atomnoi protection of the pipeline. Electrode N leave a grounded above the axis of the pipeline 1, and the electrode M kasemset on the right side from the axis of the pipeline 1 (line NM1), perpendicular to its axis. In this position, sensor 3) register value of the transverse electric component Ex to the right of the electromagnetic field of the current cathodic protection of the pipeline. Electrode N leave a grounded above the axis of the pipeline 1, and the electrode M kasemset similarly on the left side of the axis of the pipeline 1 (line NM2), perpendicular to the axis. In this position, sensor 3) register value of the transverse electric component Ex to the left of the electromagnetic field of the current cathodic protection of the pipeline. Violations of the insulating coating 4 of the pipeline are indicated elevated values of the electric component of the electromagnetic field. Depending on the conditions and the detailed study of the violations of the insulating coating of the pipeline step of observations is reduced to 1 m to 1 m to reduce the spacing of the electrodes (the magnitude of the spacing of the electrodes is further taken into account when processing).

Clarification of the location of the insulation 4 is carried out by measurements of the electrical component at the location of the line MN at different angles to the axis of the pipeline 1. In fact, at least one of the electrodes kasemset in the area of the centerline of the pipeline 1.

To improve the roizvoditelnost measurements record the values of the electric component of the electromagnetic field in the memory meter is produced using the remote control button (not shown in figure 1). Measurement is carried out along the entire pipeline in increments of 5 meters. The measurement results are in the form of graphs electric components of the electromagnetic field of cathodic protection, contour maps of the electric component of the electromagnetic field and the list of intervals tracks with violations of the insulating coating 4. The measurement results normalized on the following factors: the depth of the pipeline, the resistance of the mountainous rocks ecolotree space, the current strength in the pipeline, the background components of the electromagnetic field adjacent pipes (lead to a resistivity of 20 Ohm·m, amperage 1 amp, depth 1.5 m).

At higher values of the normalized electric components of the electromagnetic field of the current cathodic protection determine the location and size of violations of the insulating coating of the pipeline.

The background value is determined by measuring the electric components of the electromagnetic field of cathodic protection on the pipeline sections where there is no insulation.

Normal value anomalies taken into account in absolute units more than 10 mV/m·And (for the current 1 And, for the depth of the pipeline 1.5 m, to resist the environment 20 Ohm·m).

The magnitude of the disturbance is estimated while the motor DF (%) damage the protective coating, calculated for individual intervals of the track according to the formula:

where ndfthe number of observations with values of the electric component of the electromagnetic field above the graph of the "normal line" in a specified number of times;

N is the total number of observations in the interval.

In addition to the graphs of the electrical component of the electromagnetic field the results are presented in tables and graphs DF, and the list of sections of pipeline that are recommended for visual inspection in the pits.

Example

Part of the track gas "Ukhta-Torzhok" (1020 mm diameter) are laid in the swampland. It is necessary to determine the condition of the insulation coating of the pipeline.

The depth of the axis of the pipe 1, as defined in the joint measurement of the horizontal X and vertical Z magnetic components of the electromagnetic field of the current cathodic protection for the entire site investigations have not changed and amounted to 0.8 m current in the pipeline 10 A. the resistance of the wetland environment allotropes space is 50 Ohms·m is presented in figure 1 scheme consistently measured transverse electric Ex right and Ex left and longitudinal EY components of the electromagnetic field of the current cathodic protection of drobopro is Yes. The results of the measurements at each point is normalized (divided) by the current strength in the pipeline 10 And the depth of the pipeline 0.8 meters, the resistance of the medium allotropes space 50 Ohm·m, the spacing of the electrodes 5 meters, which increases the accuracy of determining violations of the insulating coating 4 and ensures the comparability of the measurement results of the electric components of the electromagnetic field of the current cathodic protection of the pipeline on different sites.

As a result, the investigated section of the gas pipeline route for increased values of the electric components of the electromagnetic field of the current cathodic protection of the pipeline selected anomalous interval 110 metres wide (figure 2 shown in gray). The excess of the normal field (the field value in the absence of insulation 4) in terms of the Mu 180 UNED (relative units), Ex right - 75 ated, Ex left - 6.1 ated In the absence of violations values Ex right now match the Ex left and do not exceed level 5 oted

The conclusion: in the survey of the pipeline found a complete lack of insulation coating on the top surface and damage to the insulation coating on the right side of the pipeline. Insulation fault has a length of 110 meters.

A positive result due to the implementation of the decree the aqueous method:

- to determine violations of the pipeline isolation is the field current cathodic protection and do not require connection of the field generator to the pipeline;

- you can determine the exact location of the pipe axis, which increases the accuracy of determining the location of the violations of the insulation of the pipe;

the measurement results are normalized based on the following parameters: the depth of the pipeline, the resistance of the rocks composing ecolotree space current in the pipeline, the background components of the electromagnetic field adjacent pipelines and transmission lines, which significantly improves the accuracy of the research state of the insulation coating of the pipeline;

for measurements requires 2 operator (instead of 4). Does not require the establishment of INTACTO (short circuit current);

- allows you to change the spacing of the measuring electrodes depending on the conditions and the detailed study of the violations of the insulating coating of the pipeline. When processing the results of measurements normalized to the spacing of the electrodes;

- provides the possibility to determine violations of the insulating coating of the pipeline in difficult ground conditions (asphalt and concrete pavement, railroad crossings, crossings over water obstacles, debris, fragments of rocks, measures the ly soil, snow and ice cover, dry Sands) when used instead of voltage electrodes of the capacitive device.

The claimed method was trace tests for five years when diagnosing the technical condition of the four queues gas "Ukhta-Torzhok", and one line "Gryazovets - Saint-Petersburg ".

Sources of information

1. Glazkov VI electrical method for finding the end-to-end damage in the insulation coatings of existing pipelines // Protection of metals", 1965. No. 2. - P.21 (Similar).

2. Linz J.M. a New method of detecting corrosion of pipelines. part 1. // Oil, gas and petrochemical industries abroad. 1993. No. 7 - P.64-66. (Prototype).

3. Krapivsky H., Demchenko N "Geophysical methods of diagnostics of technical condition of underground pipelines s-129.

The method of detection of violations of the insulating coating of underground pipelines, which consists in the dimension along the pipeline components of the electromagnetic field, characterized in that determine the depth of the pipe axis in the magnetic transverse, longitudinal and vertical components of the electromagnetic field of the current cathodic protection of the pipeline, consistently measure the longitudinal electric component of the electromagnetic field of the current cathodic protection and the transverse component of the electromagnetic field is an eye cathodic protection left and right of the axis of the pipeline, normalized results of measurements on the depth of the pipeline, the resistance of the medium surrounding the pipeline, the current strength in the pipeline, the background components of the electromagnetic field and increased values of the normalized electric components of the electromagnetic field of the current cathodic protection determine the location and size of violations of the insulating coating of the pipeline.



 

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