RU2230978C1 - Method of detection of break in pipe line - Google Patents

Abstract

FIELD: transportation of liquids, gases and other products by means of pipe lines; detection of defects in pipe lines laid on ground.

SUBSTANCE: proposed method includes flight of helicopter provided with two receiving antennae on opposite tips of main rotor blades; electromagnetic waves generated by break of pipe line and received by antennae are multiplied and harmonic voltage at frequency of rotation of main rotor is separated and compared with reference voltage; then, azimuth of radiation source of electromagnetic waves is accurately measured at simultaneous auto-correlation treatment of electromagnetic waves received by one antenna; azimuth of source of electromagnetic waves is measured at reduction of phase modulation index with no change in relationship R/λ_cr by means of differential phase direction finder by results of measurement of time intervals connected with function of frequency modulation of received electromagnetic waves during rotation of receiving antenna located on tip of main rotor blade. According to results of measurement of azimuth range, position of break in pipe line is determined; where R is radius of circle on which receiving antennae are located and λ_cr is critical length of radiating wave.

EFFECT: enhanced efficiency of detection.

2 dwg

Description

The proposed method relates to the field of transportation of liquids, gases and other products using pipelines, and in particular to methods for monitoring the integrity of pipelines located on the earth's surface and identifying the places of their ruptures.

Known methods for detecting a rupture of a pipeline (ed. Certificate of the USSR No. 642575, 723291, 1812386; RF patent No. 2135887; French patent No. 2642818 and others).

Of the known methods, the closest to the proposed one is the “Method for detecting a rupture of a pipeline” (RF patent No. 2135887, F 17 D 5/06, 1997), which is selected as a prototype.

This method consists in receiving electromagnetic waves outside the pipeline and determining the place of rupture of the pipeline. At the same time, alternating voltage with a frequency corresponding to the generation of electromagnetic waves with a wavelength close to the size of the expected gap or the diameter of the pipeline is supplied to the ends of the pipeline.

However, the known method does not provide rapid detection and location of the gap of the main pipeline.

An object of the invention is to increase the efficiency of detection and determination of the location of the rupture of the main pipeline by flying it by helicopter.

The problem is solved in that according to the method for detecting a pipeline rupture, which consists in the generation of electromagnetic waves directly by the pipeline rupture, for which an alternating voltage is applied to the ends of the pipeline with a frequency corresponding to wavelengths within the diameter of the pipeline, and the source of the resulting radiation is connected with by the location of the pipeline rupture, they fly over the pipeline by helicopter, at the opposite ends of the rotor blades of which they place two receiving antennas, and the received electromagnetic waves generated by the pipeline rupture are multiplied among themselves, a harmonic voltage is extracted at the rotor rotational speed, they are compared with the reference voltage and the azimuth of the electromagnetic radiation source is accurately measured, while the autocorrelation processing of electromagnetic waves received by one antenna, and unambiguously measure the azimuth of the electromagnetic radiation source, decreasing the phase modulation index without decreasing the ratio Ia R / λ _cr via differential-phase direction finder, according to the results of measurement of time intervals related to the function of modulation frequency of the received electromagnetic waves while rotating the receiving antenna located at the end of the rotor blade determine the range to the source of emission of electromagnetic waves, the results of the azimuth measuring and ranges determine the location of the pipeline rupture, where R is the radius of the circle on which the receiving antennas are located, λ _cr - the critical radiation wavelength.

The location of the receiving antennas on the helicopter is shown in figure 1. The structural diagram of a device that implements the proposed method is presented in figure 2.

The device comprises serially connected a first receiving antenna 5, a first high-frequency amplifier 7, a multiplier 9, the second input of which is connected to the output of the high-frequency amplifier 8, a narrow-band filter 13, a first phase meter 14, the second input of which is connected to the output of the reference generator 17, and block 18 registration, sequentially connected to the second receiving antenna 6, the second high-frequency amplifier 8, a delay line 10, a phase detector 11, the second input of which is connected to the output of the high-frequency amplifier 8, and the second phase meter 15, the second turn connected to the output of the reference oscillator 17, and an output connected to the second input register 18, whose third input unit 12 through the meter-range amplifier connected to the output 8 of high frequency. Receiving antennas 5 and 6 are located at opposite ends of the rotor blades of the helicopter. The engine 16 is kinematically connected with the rotor of the helicopter and the reference generator 17.

The proposed method for detecting a rupture of a pipeline is implemented as follows.

When installing an open pipeline next to it, lay an electric wire 3, which is connected to one of the ends of the pipeline 1. The other end is connected to the other wire of the AC voltage source 4. In the absence of a break, the emission of electromagnetic waves does not occur. In the event of a rupture 2 of pipeline 1, the rupture site serves as a kind of antenna and begins to emit electromagnetic waves with a wavelength characteristic of the size D of the rupture. To determine the characteristic size D of the gap, the following relation is used between the critical radiation wavelength λ _cr and D:

λ _cr = 1.25 D,

in which there is a transition from the exponential decay of radiation in the channel formed by the gap 2 in the wall of the pipe 1, to transmission, due to the possibility of propagation of the main wave in the waveguide channel of the gap 2.

If the pipeline is filled with a medium with a relative permittivity ε, then the radiation frequency f _cr corresponding to λ _cr is determined from the expression

where c is the speed of light in vacuum.

This radiation is received by antennas 5 and 6, located at opposite ends of the rotor blades of the helicopter

where U ₁ , U ₂ - the amplitude of the received electromagnetic waves;

f _cr - the critical frequency of the radiation;

R is the radius of the circle on which the receiving antennas 5 and 6 are located;

Ω = 2πF — rotational speed of receiving antennas 5 and 6 (rotational speed of the rotor of the helicopter);

β - bearing on the radiation source of electromagnetic waves (rupture 2 of the pipeline);

φ is the angle relative to the reference phase angle;

- фаза принимаемого сигнала.

- phase of the received signal.

The receiving antennas 5 and 6 move around the circle with a constant speed V = ΩR at a distance R _o from the radiation source 2. During the time of receiving electromagnetic oscillations from the radiation source, the antennas travel the path L = ΩtR.

The signs “+” and “-” before the phase ψ (t) correspond to diametrically opposite positions of the antennas 5 and 6 at the ends of two opposite rotor blades of the helicopter.

Direction finding of the radiation source (rupture of 2 pipelines) of electromagnetic oscillations in the horizontal (azimuthal) plane is carried out by the differential-phase method using the phase modulation caused by the Doppler effect that occurs when the receiving antennas 5 and 6 rotate in a circular fashion. The phase of the signal modulation envelope depends on the direction to the source radiation.

Since the receiving antennas 5 and 6 either approach the source, then move away from it, the Doppler effect arises, causing spatial-phase modulation of the received oscillations.

Moreover, the value

наступает неоднозначность отсчета угла β.which is part of the received oscillations and is called the phase modulation index, characterizes the maximum value of the phase deviation of the rotating receiving antennas. The direction finder is the more sensitive to the change in the angle β, the larger the relative size of the base R / λ _cr , however, with an increase in R / λ _cr , the value of the angular coordinate β decreases at which the phase difference exceeds 2π, i.e., the reading is ambiguous. Therefore, for

ambiguity of reading the angle β occurs.

The elimination of this ambiguity by reducing the R / λ _cr ratio usually does not justify itself, since the main advantage of the wide-base system is lost. In addition, in the range of meter and especially decimeter waves, it is often not possible to take small values of R / λ _cr due to design considerations.

It should be noted that existing helicopters, for example MI-6, MI-8, MI-24, MI-26, have blades 10 ... 20 m long, the rotor speed is 200 rpm and can fly around the pipeline at a safe height 50 ... 100 m.

To increase the accuracy of direction finding of the rupture of 2 pipelines in the horizontal (azimuthal) plane, receiving antennas are located at the ends of two opposite rotor blades of the helicopter. The bias of the signals from two diametrically opposite receiving antennas 5 and 6, located at the same distance R from the axis of rotation of the rotor, causes phase modulation, which is identical to the phase modulation obtained using one receiving antenna rotating in a circle, whose radius R ₁ is two times more (R ₁ = 2R).

Indeed, the output of the multiplier 9 produces a harmonic voltage

u ₃ (t) = U ₃ cos (2πFt-β),

Where

K ₁ - transfer coefficient of the multiplier,

with phase modulation index

which is allocated by a narrow-band filter 13 and fed to the first input of the phasemeter 14, the second input of which is supplied with the voltage of the reference oscillator 17

u _o (t) = U _o cos (2πFt + φ _o ).

The reference generator 17 is kinematically connected with the engine 16 of the helicopter. The phasometer 14 provides an accurate measurement of the angle β, which is recorded by the recording unit 18.

To eliminate the ambiguity of the azimuth reading β, it is necessary to reduce the phase modulation index without reducing the ratio R / λ _cr .

This problem can be solved by using a differential-phase direction finder, in which the phase difference between voltages is measured

removed from two synchronously rotating with an angular speed Ω = 2πF antennas 6 and 6 (5 and 5), shifted to each other by an angle μ (figure 1). The phase modulation index in this case is determined by the expression

- расстояние между антеннами 5 и 5 (6 и 6).Where

- the distance between the antennas 5 and 5 (6 and 6).

For d ₁ <R, the phase modulation index Δφ _m2 is smaller than that of the direction finder with one rotating antenna 5 (5) and the same measuring base

However, with this arrangement of the antennas, phase modulation is not eliminated due to the inconsistency of the phase of the received signal during the time interval τ ₃ .

A decrease in the phase modulation index can be achieved with one rotating antenna 6 (5). In this case, instead of the voltage u ₂ '(t), it is necessary to use the voltage u ₂ (t), delayed by the time τ ₃ , equivalent to the shift of the second antenna 6 (5) by the angle μ = Ωτ ₃ .

In the device that implements the proposed method, the voltage u ₂ (t) from the output of the high-frequency amplifier 8 is supplied to an autocorrelator consisting of a delay line 10 with a delay time τ ₃ and a phase detector 11. This is equivalent to a decrease in the phase modulation index to

A voltage is generated at the output of the autocorrelator

u ₄ (t) = U ₄ cos (2πFt-β)

Where

K ₂ - the transfer coefficient of the phase detector,

которое поступает на первый вход фазометра 15, на второй вход которого подается напряжение u_o(t) опорного генератора 17. Фазометр 15 обеспечивает однозначное измерение пеленга β на источник излучения. По существу фазометры 14 и 15 представляют собой две шкалы измерений угловой координаты β. Фазометр 14 представляет точную, но неоднозначную шкалу измерений, а фазометр 15 - грубую, но однозначную шкалу измерений.with phase modulation index

which is supplied to the first input of the phasemeter 15, the second input of which is supplied with the voltage u _o (t) of the reference generator 17. The phase meter 15 provides an unambiguous measurement of bearing β to the radiation source. In essence, the phaseometers 14 and 15 are two scales for measuring the angular coordinate β. The phasometer 14 represents an accurate but ambiguous measurement scale, and the phasometer 15 represents a rough but unambiguous measurement scale.

The frequency of the signal received by the moving antenna 5 (6) can be represented as follows:

where V = ΩR;

R _o is the distance from the radiation source to the screw.

When R _about >> R

The Doppler frequency shift in the sector of positions of the rotor blades 0 ... 40 ° is on average 0 ... 2000 Hz. Value (1) varies over time. We expand it in a row and are limited to the first two members

where Ωt = α _o .

The coefficient α is found from the geometric relationships (figure 1)

r=ΩtR;

r = ΩtR;

r is the distance between the radiation source and antenna 5 (6).

Determine the resolution of two sources (two gaps) in azimuth

Modulation period

Resolution is carried out at a distance when the modulating function changes by one period

where L = ΩtR.

Azimuth Resolution

- ширина диаграммы направленности бортовой антенны;Where

- the width of the radiation pattern of the onboard antenna;

d - the maximum size of the antenna located on the rotor blades.

To determine the distance to the radiation source, it is sufficient to measure the steepness of function (2) in the vicinity of the point x = 0.

Let be

Then

The maximum and minimum values of F are reached at the moment

and makes up

and the maximum value

and is achieved when

The difference of moments for adjacent maximum and minimum values is a function of range, and their half-sum is a function of the azimuth of the radiation source.

From (5), by differentiation, we can obtain a relationship between the errors in measuring the moments of the maximum and minimum Δt and the distance to the radiation source

For example, when r = 1000 m-1 = 1.3 · 10 ⁶ ; at r = 500 m -1 = 3.3 · 10 ⁵ ;

at r = 100 m -1 = 1.5 · 10 ⁴ ; at r = 50 m -1 = 4.5 · 10 ³ ;

at r = 20 m-1 = 1.1 · 10 ³ .

The measurement of the range r is carried out in the meter 12 according to the results of measuring time intervals associated with the function of modulating the frequency of the received electromagnetic waves during rotation of the receiving antenna 6 located on the rotor blade. The measured value of the range r is recorded by the block 18 registration.

The location of the gap 2 of the pipeline is determined using the measured values of the azimuth β and range r.

Thus, the proposed method in comparison with the prototype and other technical solutions for a similar purpose provides increased efficiency in detecting and determining the location of a rupture of the main pipeline. This is achieved by flying around the main pipeline in a helicopter, on two opposite main rotor blades of which are receiving antennas. A passive helicopter coordinate determination system with receiving antennas located on two opposite rotor blades allows accurate and unambiguous measurement of the azimuth β and the distance r to the ground source of radiation (pipeline rupture) from one position. At the same time, two scales are used to measure the azimuth of β: accurate, but ambiguous, and rough, but unambiguous. The azimuth resolution is determined by the implementation capabilities of the artificial aperture of the antenna and is limited by the length of the rotor blades of the helicopter. The measurement of the range r is carried out according to the results of measuring time intervals associated with the function of modulating the frequency of the received electromagnetic oscillations generated by a rupture of the pipeline during the rotation of the receiving antennas located on two opposite rotor blades.

Claims (1)

A method for detecting a place of a pipeline rupture, which consists in generating electromagnetic waves directly by the pipeline rupture, for which an alternating voltage is applied to the ends of the pipeline with a frequency corresponding to wavelengths within the diameter of the pipeline, and the source of the resulting radiation is associated with the location of the pipeline rupture, characterized in that they fly around the pipeline by helicopter, at the opposite ends of the rotor blades of which are placed two receiving antennas, and the received electromagnetic waves generated by the rupture of the pipeline are multiplied among themselves, emit a harmonic voltage at the rotational speed of the rotor, compare it with the reference voltage and accurately measure the azimuth of the electromagnetic radiation source, simultaneously carry out autocorrelation processing of electromagnetic waves received by one antenna, and unambiguously measure the azimuth of a source of electromagnetic waves, reducing the phase modulation index without reducing the R / λ ratio _cr via differential direction-finder, by measuring the time intervals associated with the frequency modulation function of the received electromagnetic waves during the rotation of the receiving antenna located at the end of the rotor blade, determine the distance to the electromagnetic wave radiation source, determine the location of the pipeline rupture by the azimuth and range measurements, where R is the radius of the circle on which the receiving antennas are located, λ _kr is the critical radiation wavelength.

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