RU2679042C2 - Method and device for defectic sciences of internal protective-insulating coatings of operating fishing pipelines - Google Patents

Abstract

FIELD: measurement technology.

SUBSTANCE: invention relates to the field of diagnostics of the state of existing field pipelines. Problem is solved by measuring the leakage of electric current resulting from the violation of the internal insulating coating of the steel pipe. Proposed method and device consist in radiation of the probing voltage pulses using a generator and measuring the parameters of the current pulse through the internal protective and insulating coating of the pipeline that occurs in the area bounded by two insulating cleaning discs sealed to the body of the in-tube device. To improve the quality of measurements, the parameters of the probe pulses are configured using a controller in the in-line device, which operates according to a specific algorithm, and the device is configured to calibrate at certain levels on models with damage.

EFFECT: invention can be used for the flaw detection of internal protective insulating coatings.

6 cl, 11 dwg

Description

The technical field to which the invention relates: diagnostics of the technical condition of existing field pipelines.

The proposed solution relates to the field of diagnostics of the technical condition of existing field pipelines, and can be used for flaw detection of internal protective and insulating coatings, in order to avoid uncontrolled opening of protective coatings and damage to the pipe wall.

State of the art

1. Known "In-tube ultrasonic inspection device" "UZVIP" from the company LLC "INTRON VTD" (http://intron-vtd.ru/3.html).

The device allows you to:

- Measure the wall thickness of the studied pipe;

- Measure the internal profile of the pipe;

- Detect delamination in the pipe wall;

- Identify pipe defects and anomalies, including unauthorized taps;

- Diagnose pipes from non-magnetic materials, including polyethylene and stainless steel.

Including the device has the ability to measure the thickness of the inner protective coating.

But the device is not intended to search for minor defects of the internal protective and insulating coating, which lead to leaks of the aggressive working medium of the pipeline to the metal wall and are the cause of its active destruction.

2. Known electrospark method for the diagnosis of insulation coatings.

One of the versions: “KORONA 1B (Digital) electrospark defectoscope” from the ANK company, Perm (http://ank-ndt.ru/produkcziya/kontrol-izolyaczii/elektroiskrovyie-defektoskopyi/korona-1v.html) .

“The device is designed to control cracks, porosity, unacceptable thinning and other violations of the integrity of the protective coatings inside the pipes.

Features:

- high safety due to the pulse mode of operation;

- a specialized disk electrode with support wheels, which allows you to control pipes of a given size with a large variation in bore diameter;

- a specialized prefabricated system for feeding and moving a disk electrode inside a pipe with support wheels;

- the ability to control the continuity of coatings of structures after assembly (welding) to a length of 14 m. "

The method is applicable only in a dry short pipe. If the pipeline is in operation and is filled with any kind of liquid, the method is not applicable in principle.

3. In the article "Method for the diagnosis of internal anti-corrosion coating of pipelines", A.A. Kundik (Gazpromneft-Orenburg LLC) PROneft Magazine (http://ntc.gazprom-neft.ru/research-and-development/proneft/1236/20535/) offers:

3.1. “The proposed method for determining the place of violation of the integrity of the pipe insulation is based on the ability of produced water to conduct electric current. An open circuit is created with a “plus” on a highly sensitive device, which is connected to the pipe metal in the zone of the most vulnerable place (weld), “minus” on the electrolyte - bottom water. After supplying current to the weld in the event of violation of the integrity of the insulation, the circuit will close and the device will indicate the presence of current. If the dielectric (insulating) layer is not broken, the circuit remains open, and the device indicates the absence of current. The main disadvantage of this method is the local nature of the control of the pipeline section. It is applicable only to detect defects in the installation of bushings that insulate the welded joints of the pipeline.

At the same time, the problem of determining the breakdown of the internal insulation coating along the pipeline route remains unresolved. ”

In the same place (“Method for diagnosing the internal anti-corrosion coating of pipelines”, A.A. Kundik (Gazpromneft-Orenburg LLC) PROneft Magazine):

3.2. “However, it is possible to solve the problem, based on the nature of the electromagnetic field. An insulated section of the pipeline filled with electrolyte is a conductor of electric current, therefore, when a current is applied to the in-tube space around the electrolyte, a magnetic field will inevitably form. In a longitudinal section of the pipeline, the magnetic field propagates in the form of a sinusoid. In the place of violation of isolation of the sinusoid will go beyond the reference values. Thus, when fixing the value of the magnetic field with a special device, it becomes possible to determine the places of insulation damage along the entire length of the mounted pipeline. ”

The method also did not find wide application due to the ambiguity of the results, the complexity of measurements on rough terrain, in conditions of significant deepening of the studied pipeline, as well as the impact of environmental noise factors.

4. The closest in technical essence to the claimed invention is a method of measuring in lateral logging with a three-electrode probe (see, for example, SS Itenberg, TD Dakhkilgov. Geophysical studies in wells. M .: "Nedra", 1982. P. 108, 131, 132), in which the central (A0) and screen (A1-0, A1-1) probe electrodes connected to each other to equalize their potentials with an electric shunt of low resistance (Rш≈0.01 Ohm), supply alternating current, measure the current I _{0 of the} central electrode and the potential ΔU of the screen electrodes of the relative But the reference electrode also determines the apparent resistivity P _to rocks. (Fig. 1).

Physical basis of the method.

“Lateral logging refers to measurements of apparent resistance along a borehole with a three-electrode lateral logging probe with automatic focusing of current. The probe has a central electrode Ao (Fig. 2), symmetrically with respect to which elongated shield electrodes (A1 and Ae2) are interconnected.

When measuring the apparent resistance, the same potential of all electrodes is provided. Thus, the screen electrodes prevent the spreading of the current of the central electrode through the borehole and direct it directly into the studied formation (Fig. 3). "

This measurement method is designed to measure rock resistance in wells, and of course is not intended to diagnose the technical condition of pipes.

SUMMARY OF THE INVENTION

The objective of the invention is to identify small-sized damage to the protective insulating coating of the pipeline, causing leakage of pumped aggressive liquids to the steel wall of the pipe, causing its active corrosion failure.

The problem is solved by measuring the leakage of electric current arising from a violation of the internal insulation coating of the steel pipe.

In FIG. 4 shows an in-line device for flaw detection of internal protective-insulating coatings (hereinafter referred to as the "In-pipe device"), placed in the studied pipeline.

In FIG. 5 - The design of the probe in-tube device.

In FIG. 6. - Electrical diagram of the tube probe.

In FIG. 7. - Distribution of current lines of the in-tube device in the studied pipeline.

In FIG. 8 is an equivalent circuit diagram of an in-line instrument and a test pipeline.

From the diagrams in FIG. 6–8, you can understand that the main current loop is made up of elements: “Generator - Electrodes A0, Ae1, Ae2 with the same potential - electrodes B1, B2.”

The role of the conductors in this circuit is played by the fluid filling the internal space of the studied pipeline. The liquid, of course, is not perfect, not distilled water, and usually has very good conductivity, which is shown in the diagram by the resistors "R0", "Re1", "Re2", "Rb1", "Rb2".

The capacitors shown in the diagram, connected in series with each of the resistors, display the capacitive properties of the insulation coating in each of the sectors.

The conductivity of each of the sections will depend both on the properties of the filling fluid and on the geometric parameters of the sections corresponding to certain electrodes of the in-tube device.

The capacitive properties of each of the sites will depend on:

1) coating thickness

2) the length of the section corresponding to a specific electrode

3) the internal diameter of the studied pipeline.

In the General case, the capacity of each of the sites will be determined by the formula:

Where

ε ₀ = 8.854187817 × 10 ^-12 f / m is a constant value.

ε is the dielectric constant of the dielectric between the plates,

S is the area of the lining,

d is the gap between the plates (in our case, the thickness of the coating).

Area "S" is calculated by the formula "cylinder surface area":

S = π * D * L

Where

π = 3.14 - geometric constant;

D is the cylinder diameter (in our case, the inner diameter of the pipeline);

L is the length of the cylinder (we have the length of each of the sections).

In general, without going into details of the calculation algorithm, we can highlight the main points that characterize the measurement method:

1. Since there are reactive elements (capacitors) in the circuit, such a circuit cannot operate on direct current.

2. Since the electrical properties of the filling fluid will change, and the geometric parameters of the sections above the probe will depend on the diameter of the studied pipelines, the operating frequency must be adjusted in each case, for better measurements.

Of course, this does not mean regular manual reconfiguration of the device. With this function, the controller in the in-tube device, working according to a certain algorithm, can safely cope.

3. For such measurements it is more convenient to use a signal not of a sinusoidal shape, but of a pulsed one.

Firstly, the generator circuit is much simplified.

Secondly, it is possible to measure not only the average values of currents, but also the parameters of transients, which significantly expands the capabilities of the method.

4. Since the length of the sections of the pipeline corresponding to the electrodes “B1” and “B2” will be almost infinite, the corresponding capacities (capacitors “Sv1” and “Sv2”) will be at least an order of magnitude larger than the capacity in the main measuring circuit “ C0. "

This is the most important thing for us. This means that “C0” is our main sensitive element.

And it is worth leaking (defect of the insulation coating) in the sector of the measuring electrode "A0", the measuring circuit takes the form of FIG. 9.

This additional element, the resistor "Ru" (leakage resistance), will change the parameters of the measuring circuit, depending on the area of the defect of the insulation coating.

That is, our ultimate goal is the most accurate calculation of Ru, and then we will be able to judge with appropriate accuracy the nature of the violation of the insulation coating. Either this is a scratch with a minimum area of violation, or it is a “torn” flap with an area of tens or hundreds of square centimeters.

5. Since the internal environment of the studied pipeline is not ideal, it can cause greasing of the electrodes (oil film, but of course not fuel oil). Trying to keep the electrodes clean for reliable galvanic contact is an ungrateful task. This can be either troublesome (complicating the design, regular cleaning), or expensive (special coatings).

In fact, the possible thickness of such a film is hundredths of a millimeter. Therefore, with a significant area of the electrodes, and the meager thickness of the insulator of such a "capacitor", we obtain a sufficiently large capacitance, many times greater than the capacitance of "C0". This means that such a film will not introduce any significant errors in our measurements, and we can neglect this additional capacity in the measurement scheme.

6. When pushing the in-tube device inside the test pipe, fluid leakage will inevitably occur between the pipe and the pulling sleeve, as well as between the pipe and the cleaning discs.

But since we have “screen electrodes”, they will not allow liquid leaks to lead to current leaks from the measuring electrode directly to the “B1” and “B2” electrodes.

That is, it does not threaten us with significant errors.

Another significant point of measurement.

The pipeline always contains a certain set of fittings - tees, gate valves, taps, etc., which will not contain enough high-quality protective coatings, and accordingly will introduce additional errors in the measurements.

But the fact is that usually such elements are spaced far enough apart. Therefore, we can assume that with respect to the in-tube device, they will usually be located only on one side, either in the sector of electrode “B1” or in the sector of electrode “B2”.

And also, if the pipe is not previously cleaned, then it will be sediment in front of the in-tube device, and the passing in-pipe device with its cleaning discs and pulling cuff will at least somehow clean the pipe.

And it turns out that the measurements in the circuit "Measuring electrode - electrode B1" should always be different from the measurements in the circuit "Measuring electrode - electrode B2".

Let us turn this into a virtue by organizing separate measurements in these chains. The circuit of FIG. 10.

Timing diagram of signals in the circuits “Measuring electrode - electrode B1” (Generator G1) and “Measuring electrode - electrode B2” (Generator G2) - in FIG. eleven.

That is, these circuits operate in a pulsed mode, alternately.

Both screen electrodes “A1” and “A2” always work.

The technical result of the invention is a high-quality flaw detection of internal protective and insulating coatings of existing field pipelines.

Brief Description of the Drawings

FIG. 1. Scheme of the side logging probe.

This, which has already become classic, the scheme of the side logging probe clearly demonstrates that the current of the measuring electrode is directed perpendicular to the vertical axis of the probe, due to the presence of screen electrodes. Since the potentials of the electrodes “A0”, “A1-0” and “A1-1” are equal, this does not allow the current of the measuring electrode to follow the shortest path through the drilling fluid, but directs it to the rock opposite the measuring electrode.

FIG. 2. The electrical circuit of the three-electrode lateral logging probe (BK-3).

"Ae1" - screen electrode 1;

"A0" - measuring electrode;

"Ae2" - screen electrode 2;

Rш - a shunt with low resistance (Rш≈0.01 Ohm) between the screen and measuring electrodes.

The designation of the screen electrodes hereinafter: “Ae1”, “Ae2”.

FIG. 3. The distribution pattern of the current lines of the lateral logging probes in a homogeneous medium for a three-electrode probe.

This circuit is very similar in essence to that shown in FIG. 1, but more clearly displays the studied interval.

FIG. 4. In-tube device located in the studied pipeline.

1 - Device for starting the device into the pipe.

2 - The studied pipe.

3 - In-tube device.

4 - Camera receiving device.

FIG. 5 Design of the in-line device.

5 - electrode "B1"

6 - screen electrode "AE1"

7 - measuring electrode "A0"

8 - screen electrode "AE2"

9 - electrode "B2"

10 - pulling cuff

11 - cleaning discs

12 - insulators

FIG. 6. The electric circuit of the in-tube device.

Generator generates a pulse signal to the screen and measuring electrodes. Moreover, the signal is fed to the measuring electrode through a low-resistance resistor "Run" to measure the current flowing in the circuit.

All electrodes are separated by insulators, above each of which is installed either a pulling cuff or a cleaning disc.

Moreover, these elements are installed on the insulators in such a way as to ensure tightness between the sections corresponding to each of the electrodes.

FIG. 7. Distribution of current lines of the in-tube device in the studied pipeline.

Here, the direction of the currents in each of the sections is visually displayed, and the approximate ratio of the geometric dimensions of each section of the pipe.

FIG. 8. Equivalent electrical circuit of the in-tube device and the studied pipeline.

Each of the electrodes of the in-tube device corresponds to a certain volume of liquid.

The filling fluid has a certain electrical conductivity, depending on the chemical composition.

The geometric dimensions of each volume of liquid above the corresponding electrode of the in-tube device will also affect the electrical parameters.

Therefore, each of the sections above the corresponding electrode is displayed by an equivalent electrical circuit consisting of a series-connected resistor (liquid conductivity) and a capacitor (protective and insulating coating of the studied pipeline).

FIG. 9. Equivalent electrical circuit of the in-tube device and the studied pipeline, with a defect in the insulation coating on the measuring electrode.

The same as in FIG. 8, but in the test area (opposite the measuring electrode), a defect in the insulation coating appears - an electric current conductor "Ry" (Leakage Resistance).

FIG. 10. The electric circuit of the in-tube device for separate measurements with electrodes "B1" and "B2".

In contrast to the circuit of FIG. 6, here we have 2 generators generating alternating pulse signals.

FIG. 11. Timing diagram of signals during separate measurements with electrodes “B1” and “B2”, corresponding to the circuit in FIG. 10.

The implementation of the invention

Like all in-line diagnostic shells operating over long distances (kilometers, tens of kilometers, and even hundreds of kilometers), this in-line device is pushed by the working medium of the pipeline under study. No pulling on the cables is applicable here, so we do not consider them.

When pushing the in-tube device with the working medium of the studied pipeline, certain reinforcement is required. We will not describe the whole complex; we will restrict ourselves to the main elements depicted in FIG. 4: Launcher and Reception Camera.

Initially, the in-tube device is placed in the Launcher, and is pushed by the working fluid into the test pipeline.

The speed of movement through the pipeline is determined by the performance of the pump, and is strictly specified in the statement of work for inspection of the pipeline.

The in-tube device that has passed the entire distance enters the receiving chamber, as evidenced by a special “flag”.

The device is removed from the reception chamber, laundered. Recorded data is extracted from it (on a memory card, or through an interface cable), and the device is preserved until the next cycle of work.

Requirements for the working environment of the studied pipeline, unambiguously arising from the measurement method:

1. The liquid must be well conductive and not contain viscous insulating fractions (fuel oil).

2. A minimum amount of gas is desirable. The air plug formed in the upper sector of the working area (Volume around the measuring electrode) excludes the corresponding sector from the examined area, since there is no electric current in this sector.

Linking the measured data to the distance along the studied pipeline can be made in various ways, for example:

- using odometric wheels, and recording their readings in the memory of the in-tube device;

- strict measurement of the volume of pumped liquid, with the recording of data in the memory of the measuring system at the pumping control point. After removing the in-tube device, its data is synchronized with the pumping data.

- Using a system of beacons and marker points;

- Etc.

Claims (11)

1. The method of flaw detection of internal protective and insulating coatings of existing field pipelines, consisting in the emission of probing voltage pulses using a generator, characterized in that in order to detect current leaks between the internal environment of the examined pipeline and the steel wall of the pipe, indicating the presence of a defect in the protective insulation coating, measure the parameters of the current pulse through the internal protective-insulating coating of the pipeline in a limited area. 2. The method of defectoscopy of internal protective-insulating coatings of existing field pipelines according to claim 1, characterized in that in order to improve the quality of measurements in areas containing deposits or valves such as valves, tees, etc., the measurements are made alternately relative to the electrode "B1 "In the rear of the in-tube device and the B2 electrode in the front. 3. The method of flaw detection of internal protective-insulating coatings of existing field pipelines according to claim 1, characterized in that the device is calibrated to compact defects, such as a scratch, with a minimum damage area, and to large ones, with an area of tens or hundreds of square centimeters at certain levels on special models with damage. 4. A device for defectoscopy of internal protective-insulating coatings of existing field pipelines, based on the generation of sounding voltage pulses and measuring the parameters of the current pulse through the internal protective-insulating coating of the pipeline arising in the area bounded by two insulating cleaning disks hermetically fixed to the body of the in-tube device, characterized in that in order to detect current leaks between the internal environment of the examined pipeline and the steel wall of the pipe, indicating the presence of a defect in the protective insulation coating, the measuring system contains a measuring electrode "A0", as well as an electrode "B1" in the rear of the in-tube device and an electrode "B2" in front of which alternate pulse measurements are made, and the measuring electrode is connected through a low-impedance shunt to measure the parameters of the pulses flowing through it current. 5. A device for defectoscopy of internal protective-insulating coatings of existing field pipelines according to claim 4, characterized in that in order to eliminate the influence of leakage of electric current in the gap between the cleaning discs and the inner wall of the pipeline under examination, the in-tube device contains screen electrodes "A1" and "Ae2 »On both sides of the measuring electrode, having equal electrical potential with it. 6. A device for defectoscopy of internal protective-insulating coatings of existing field pipelines according to claim 4, characterized in that in order to improve the quality of measurements when changing the electrical properties of the filling fluid, as well as when changing the diameter of the studied pipelines, the parameters of the probe pulses are adjusted using the controller in the in-pipe a device that works according to a certain algorithm.

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