Method of searching for damages in underground pipe insulation

FIELD: physics.

SUBSTANCE: electrical currents are generated on two sides of the analysed section of a pipe. Movement is carried out on the pipeline route from a receiver with a magnetic field strength sensor. In the initial position, the magnetic axis of the sensor lies in the vertical plane passing through the axis of the pipe. Signals generated by components of magnetic field strength components in the given plane from both currents in the receiver are equal to zero. During movement, equality to zero of the signal from the current on one side of the pipe is constantly monitored through rotation about the vertical axis of the receiver. The point of damage to insulation is found from the signal in the receiver from the vector sum of magnetic field strength values generated by current on the other side of the pipe section and stray current from it.

EFFECT: efficient detection and accuracy of locating damages and reduced labour input.

2 dwg

 

The invention relates to a method of fault isolation of pipelines, cables and other underground utilities.

The known method for the contactless detection of insulation, in which the seeker insulation containing two transducer of the magnetic field into an electrical signal, is placed over interstate communication on vertical straight to the track so that the first placed under the second set alternately in places of control along the route communications. So produce a measurement of the output voltages from the sensors, which are proportional to the intensities azimuthally components of the magnetic field created by electric current flowing through communication, and using electronic Converter to calculate the depth of communication and the amount flowing through it current. The difference between the current measured in the areas of control, determines the amount of leakage current in the ground at the site of communication (USSR author's certificate N 1592810, G01R 31/08, 1987).

The main disadvantage of this method is the low performance.

Closest to the proposed method is a method for the contactless measurement of the leakage current at the site of underground conductors line, whereby when moving along the conductors on its phase is created with each of the two sides of the modulated electric current. At two points at the beginning and at two points at the end of the subject site, and the points at the beginning and at the end of the segment are the same distance from each other along straight, which is a continuation of the radii of communication, the receiver containing the magnetic field sensors to measure tension azimuthally components of the magnetic fields created by these currents. The detection of a leakage current from the modulated currents are, in defining the beginning and end of the segment against the tension azimuthally component of the magnetic field created one of the modulated currents to tension azimuthally component of the magnetic field created by another shock. The equality of these relationships means an absence of leakage currents (RF Patent N2150710, G01R 31/08, 31/02, 1999).

The main disadvantage of this method is the low performance because to determine where insulation is necessary to conduct several measurements, reducing the distance between the two measuring points on the pipeline route.

The proposed method aims at improving the efficiency of the detection and accurate localization of insulation while reducing complexity.

This goal is achieved by creating two sides of the pipeline electric currents moving along the pipeline route with primn the com, containing the sensor magnetic field strength, the magnetic axis is in the initial position lies in a vertical plane passing through the axis of the pipeline, and the signals generated by components of the magnetic field in the plane of both currents in the receiver is equal to zero. When driving along the pipeline to continually provide rotation about the vertical axis of the receiver is equal to zero signal current from one side of the pipeline. When passing over the defect receiver rotate around a vertical axis so as to obtain a zero signal from the vector sum of magnetic fields generated by current from one side of the pipe and the leakage current from it, and place the insulation to find the signal in the receiver from the vector sum of the magnetic fields created by another current, and leakage current from it. The electrical currents that are generated on both sides of the pipeline can have a different frequency.

Figure 1 shows an illustration of the proposed method, and figure 2 is a vector diagram of the magnetic fields generated by currents flowing in the pipeline, and leakage current.

The drawings indicated: insulated pipe 1; the receiver 2 with the magnetic field sensor 3; I1- electric current in the pipeline that is created on one side of the pipelines is a; I2- electric current in the pipeline, created on the other side of the pipeline; I1U- leakage current from the current I1; I2U- leakage current from the current I2; H1the magnetic field created by the current I1; N2the magnetic field created by the current I2; H1Uthe magnetic field created by the current I1U; H2Uthe magnetic field created by the current I2U; H1Sthe magnetic field is a vector sum of H1and H1U; H2Sthe magnetic field is a vector sum of H2and H2UMagnetic axis (AB) sensor in the initial position lies in a vertical plane passing through the axis of the pipe, and the sensor signals from both of the currents in the absence of defect zero. When driving along the pipeline to continually provide rotation about the vertical axis of the receiver is equal to zero signal current from one side of the pipeline. If there is a defect isolation current I1and the leakage current I1Ucreate a magnetic field intensity vector which are added, and the resultant magnetic field H1Slies in a plane angled to the pipeline. When this receiver is turned around a vertical axis so as to obtain a zero signal DOS is ikaetsya, when the direction of the magnetic axis of the sensor (AB1) perpendicular to the direction of the field H1S. The current flowing on the other side of the pipeline (I2) also has a leak in the defect isolation (I2U). Tensions they create magnetic fields H2and H2Uaccordingly, vector formed. Their vector sum of H2Slies in a plane angled to the pipeline and at an angle to the magnetic field H1S. In this regard, when the rotation sensor in the receiver receive the signal from the magnetic field strength H1S. On this signal to find the location of the defect.

As an example, the fault isolation of the pipeline with a diameter of 1420 mm, lying at a depth of 2 m On the section of the pipeline serves the currents on the one hand with a frequency of 10 Hz, and on the other hand - with a frequency of 6.25 Hz. The operator, having a receiver with a flux-gate magnetic field sensor, moves along the pipeline. In the initial position of the magnetic axis of the sensor lies in a vertical plane passing through the axis of the pipeline. When driving along the pipeline operator constantly provides rotation about the vertical axis of the receiver is equal to zero signal current with a frequency of 10 Hz. When passing over the defect isolation pipe he turns the receiver around the slight pressure from the beginning to the axis so that to obtain a zero signal with a frequency of 10 Hz. The fault isolation, the operator finds on the frequency of 6.25 Hz.

Thus, the present invention can solve the problem of increasing the efficiency of detection and accurate localization of insulation while reducing complexity.

The method of fault isolation of underground pipelines, which consists in creating two sides of the pipeline electric currents moving along the pipeline route with the receiver, containing the sensor magnetic field, characterized in that the magnetic axis of the sensor in the initial position lies in a vertical plane passing through the axis of the pipeline, and the signals generated by components of the magnetic field in the plane of both currents in the receiver is equal to zero, and in the process of moving constantly provide rotation about the vertical axis of the receiver is equal to zero signal current from one side of the pipe under the insulation to find the signal in the receiver from the vector sum of magnetic fields generated by the current on the other side of the pipeline, and the leakage current from it.



 

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