RU2523043C1 - Method of detecting emergency situation precursors on linear part of underground main product pipeline - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method includes exciting a periodic sequence of vibroacoustic pulses in a given pipe section, detecting said pulses in two sections of the product pipeline located roughly equidistant at both sides of the excitation section, accumulating the sum of readings of integrals of differences of detected signals. The number of accumulations in a cycle is determined by calculation based on a given spurious solution probability for each emergency situation precursor, an estimate of the level of the expected signal at detection points, mean-square deviation of the recorded readings of said integrals, and the decision on the emergence of an emergency situation precursor is made if the result accumulated in a cycle exceeds one of predetermined reference levels. The decision to prepare a cut-in pipe section is transformed into an alarm signal through a loudspeaker installed on the monitored area, and signals of all decisions made are transmitted to a mnemocircuit in a security service via telemechanic channels.

EFFECT: enabling early detection of an imminent emergency situation on a linear part of an underground main product pipeline.

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Description

The invention relates to the control of the safety of operating main product pipelines and can be used to prevent the installation of cut-ins in the pipe, ammunition for undermining it, simulators of leaks of the pumped product for misinformation of the security service, detection of product leaks.

A known method of detecting changes in the state of a section of a pipeline by the appearance of a vibro-acoustic signal in the pipe shell that forms when the insert is inserted into it [Protection of pipelines from unauthorized inserts / A.A. Cossacks // Security Systems. - 2008. - No. 5. - S.150-154]. The disadvantage of this method is the late appearance of a warning signal, eliminating the possibility of preventing a violation of the integrity of the pipe by intruders and the accompanying emergency.

A known method of detecting an "emergency" section of the pipeline, based on the excitation of shock vibroacoustic pulses in the shell of the pipe using welded to it sound conductive rods, followed by determining the ratio of the resonant frequency of the diagnosed pipeline to the reference [Pat. 2350833 RF, IPC F17D 5/00. The method of monitoring and diagnosing the state of the pipeline [Text] / Tolstunov S.A., Moser S.P., Tolstunov A.S.]. The method is based on the well-known ratio of the dependence of the resonant frequency of the plate ƒ ₀ on its thickness h: ƒ ₀ = c / 2h, c is the propagation velocity of longitudinal waves in the pipeline. Using this pattern to identify earthworks in a protected area is not possible.

Known application No. 2006137406/28 of 10.23.2006 (publication date 04/27/2008) for a method and device for early detection of leaks in a pipeline. According to the application, periodic pressure waves are generated in the pumped product, which are recorded at the other end of the controlled area. The distortion of the recorded wave judges the presence of leakage in this area. The method does not allow to record changes that occur outside the shell of the pipeline.

A known method for detecting leaks in the pipeline transport of hydrocarbons, based on the registration and analysis of infrasound signals in the pumped product [Pat. US 666861982. Pattern matching for real time leak detection and location in pipelines and in various embodiments described in http://acoustic-solution-intl.com/faq_index. htm; www.grouplb.com; http://torinsk.ru/publication/25-mpp2007.html and others. The disadvantage of this method is the fact of violation of the integrity of the pipeline, and not preparatory work on the installation of a tie-in or ammunition.

Of the known technical solutions, the closest in combination of essential features to the claimed is a method for detecting changes in environmental parameters in the environment of a buried main pipeline [Pat. 2463590 RF IPC G01N 29/04. A method for detecting changes in environmental parameters in the environment of a buried main pipeline / Epifantsev BN, Fedotov AA].

According to the method, ringing pulses of elastic vibrations are excited in a selected section of the pipe shell, registered at a distance from the excitation section, a certain number of recorded pulses are accumulated in the next cycle of sequentially taken decisions, standards of emergency precursors (ES) are formed, and a decision is made based on the results of comparing the accumulation result with the standard. The disadvantage of this method is the high complexity of creating situations for building standards for emergency precursors on an existing product pipeline. To simulate a leak, it is required to dig a pit, partially fill it with oil, fill the remaining space with soil, and compact the earth above the pit. To simulate the situation “preparation for the insert”, it is necessary not only to dig a pit, but also to remove the insulation from the pipe. The above operations are not provided for by the current technical conditions for the operation of product pipelines. In addition, the constructed standards do not reflect the actual state of the product pipeline under changing weather conditions, product pumping modes, and it is often necessary to correct them.

The aim of the invention is to eliminate the process of creating physical standards for emergency precursors in buried product pipelines while maintaining the reliability of detection at the required level at any time of the year.

This goal is achieved by the fact that the registration of ringing pulses of elastic vibrations is carried out in two sections of the shell of the product pipeline, approximately the same distance on both sides of the cross section of their excitation, the accumulation result is obtained in the form of samples of the integrals of the differences of these pulses, and the number of accumulations N _j in the cycle is determined as a result of solving the equation

$${\epsilon }_j\ge {\displaystyle \underset{\pm N_j\Delta C_j}{\overset{\pm \infty }{\int }}P\left(\sqrt{N_j{\sigma }_{\Delta E}}\right)d\Delta E}$$

according to the given probability of false decisions ε _j for the jth precursor of emergency situations, the estimated estimate of the expected signal ΔC _j at the registration points, the standard deviation of the recorded samples of these integrals ΔE, i.e. σ _ΔE , the levels ± N _j ΔC _j are used as standards, and the decision on the appearance of the j-th precursor of an emergency is made when the result of the reference levels set for it is exceeded for the cycle.

The invention is illustrated by the following description and the accompanying drawings. Figure 1 presents a variant of the structural diagram that implements the proposed method. Figure 2 explains the algorithm for determining the number of accumulations of the integrals of the differences of the recorded signals.

Designations in the figures: 1 - image of the product pipeline; 2 - soil surrounding the product pipeline; 3, 4 - sensors of vibroacoustic vibrations in the pipe shell; 5 - converter of electrical signals into elastic vibrations at a given point in the pipe; 6 - key, ensuring the transmission of the input signal to the output during the action of the control signal at another input; 7 - scheme of subtraction; 8 - delay line; 9 - generator "ringing"pulses; 10 - integrator of the input signal during the existence of the "ringing"pulse; 11 - calculator of the standard deviation of the integrated differences of the signals from the sensors 3, 4; 12 - microcontroller; 13, 14 - drives input signals; 15, 16, 17, 18 - decisive devices; 19, 20 - multipliers; 21 - loudspeaker; A, B - adjacent sections of the product pipeline, C - decision-making device; ΔC _y, ΔC _present - the increment of the recorded signal when a product pipeline at the site respectively leakage or changes related to the preparation of tapping; ε _y , ε _bp - set (acceptable) probabilities of false decisions provided by the device, N _j , - the required number of accumulations to ensure detection of the corresponding emergency precursor with the probability of false decisions ε _j , “Sin” - synchronization of operation (reset, start) of the adoption device solutions C, P (...) - probability density of the integrated differences of the signals from the sensors ΔE (t _i ) at the moments t _i .

It is known that the amplitude of the signal at the output of the sensors 3, 4 contains information about the parameters of the pumped product, the characteristics of the pipe and its environment [Budenkov S.A. et al. Evaluation of the possibilities of the acoustic emission method for monitoring pipelines // Defectoscopy, 2000, No. 2, S.29-36]. The reradiation of the elastic vibrations of the shell into the liquid is determined by its density, the turbulent medium, which is the pumped product, generates fluctuations in the amplitude of the recorded signals. The roots of trees in windy weather are sources of elastic vibrations in the soil, penetrating from the environment into the shell of the product pipeline. These and a number of other sources of non-informative signals (noise) determine the variance of the amplitudes of the recorded signals entering the subtraction circuit 7.

The pulses from the generator 9 are converted into elastic vibrations by element 5, recorded by sensors 3, 4, subtracted from one another by circuit 7, fed through key 6 to integrator 10, and the samples of the obtained integrals of the differences of the indicated pulses are sent to circuits 11, 13, 14. Since during propagation of elastic vibrations through the product pipeline, they are delayed relative to the excited pulses of the generator 9, a delay line 8 is introduced to control the key 6. Integration of the resulting differences increases the signal-to-noise ratio, they are suppressed high frequency components of noise.

Scheme 11 is entrusted with the function of calculating the standard deviation of the incoming samples σ _N :

$${\sigma }_N=\sqrt{\frac{\mathrm{one}}{N}{\displaystyle \sum _{t=\mathrm{one}}^N{({\displaystyle \underset{t_i}{\overset{t_i+\tau }{\int }}\Delta U(t)dt-m_N^{*}})}^2}},{\displaystyle \underset{t_i}{\overset{t_i+\tau }{\int }}\Delta U\left(t\right)dt=\Delta E\left(t_i\right)},$$

- оценка математического ожидания ΔE(t_i), которое при отсутствии предвестников ЧС устанавливается равным 0. Число N определяется по задаваемой точности определения σ_N схемой 11 с учетом количества импульсов, поступающих на ее вход со схемы 8.where N is the number of received samples in circuit 11, ΔU (t) is the signal at the output of circuit 7 at the moment of existence of the pulse at the output of circuit 8, τ is the pulse duration of the master oscillator 9, $$m_N^{*}$$

- an estimate of the mathematical expectation ΔE (t _i ), which in the absence of emergency precursors is set to 0. The number N is determined by the specified accuracy of determining σ _{N by} circuit 11, taking into account the number of pulses arriving at its input from circuit 8.

Upon completion of the formation of the value of σ _{N, the} microcontroller 12 is turned on. Its task is to determine the values of the numbers of accumulated signals ΔE (t _i ) for the given ε _y , ε _bp , ΔC _y , ΔC _bp and σ _N to detect the corresponding emergency precursors: "leakage" or "Preparation for setting the sidebar." In the general case, there may be more precursors, the device in Fig. 1 reflects the cases of detection of the indicated deviations from the norm in one of the controlled areas A, B.

, характеризуются на выходе схемы 11 только дисперсией $${\sigma }_N^2$$

. Накопление независимых отсчетов $${\displaystyle \sum _{i=1}^N\Delta E\left(t_i\right)}$$

увеличивает (согласно положениям теории вероятностей) среднеквадратическое отклонение обозначенной усредненной суммы в $$\sqrt{N}$$

раз (см. фиг.2). В то же время накопление сигнала ΔC_y·/(ΔC_вр) увеличивает итоговый сигнал в N раз. Поэтому увеличивая N, можно в принципе выявить сколь угодно малый полезный сигнал ΔC_j. Это известный вывод теории обнаружения сигналов. Применительно к рассматриваемой задаче не ясно, на каком количестве накоплений следует остановиться для ее решения.The operation algorithm of the microcontroller 12 can be explained using the signal density ΔE (t _i ) shown in Fig. 2. In the absence of accumulation (N = 1) has the form of probability density P (? E (t _i), N = 1). Noises generated by turbulent pressure pulsations in the pumped stream, by their nature, have a normal probability distribution law and for $$m_N^{*}\approx 0$$

are characterized at the output of circuit 11 only by dispersion $${\sigma }_N^2$$

. Accumulation of Independent Samples $${\displaystyle \sum _{i=\mathrm{one}}^N\Delta E\left(t_i\right)}$$

increases (according to the provisions of probability theory) the standard deviation of the indicated average sum in $$\sqrt{N}$$

times (see figure 2). At the same time, the accumulation of the signal ΔC _y · / (ΔC _bp ) increases the final signal by N times. Therefore, increasing N, it is possible in principle to reveal an arbitrarily small useful signal ΔC _j . This is a well-known theory of signal detection. In relation to the problem under consideration, it is not clear how many accumulations should be stopped to solve it.

From a physical point of view, the formation of a pit in an adjacent section (A or B) and the preparation of an exposed pipe to install a tool for creating an insert leads to a sharp reduction in the re-emission of propagating vibrations along the product pipeline in this zone and the appearance of a positive increment ΔC _bp in the registration cross section (formulas for calculating this increments are given in [Merkulov LG, Attenuation of normal waves in plates located in a liquid // Acoustic Journal, 1964, vol. X, issue 2, P.206-211; Budenkov GA, et al. Evaluation of the capabilities of the method akus nical emission at the control trunk pipelines // Flaw 2000, №2, S.29-36]). In case of a leak, the soil surrounding the product pipeline will be saturated with the resulting product. As a result, the re-emission of the propagating energy of elastic vibrations increases, the signal at the output of the registration system decreases (-ΔC _y ). Existing calculation methods allow us to estimate the values of ΔC _BP and ΔC _y . But there is a problem to detect these deviations in conditions when the signal-to-noise ratio at the input of the sensors is significantly less than unity. The only visible way to solve the indicated problem is to accumulate small deviations ΔC _bp , ΔC _y . According to the conditions of the task, several thousand accumulations are allowed and, therefore, it is possible to increase the initial signal-to-noise ratio up to 50-60 times. The opposite requirement: the more time will be spent on the implementation of the accumulation operation, the greater the volume of soil will be contaminated with the resulting product, i.e. the accumulation interval should be reduced.

A compromise solution to the problem is seen in the analysis of figure 2.

. Вероятность ложной тревогиIn solving the problem of detection (recognition) are set acceptable to the consumer the possibility of false solutions e _sp (ε _y) and passes the goal. With the accumulation of the signal increases in accordance NΔC _Bp (NΔC _y), the standard deviation of the noise - the law $$\sqrt{N}{\sigma }_N$$

. Probability of false alarm

$${\epsilon }_j\ge {\displaystyle \underset{\pm N_j\Delta C_j}{\overset{\pm \infty }{\int }}P\left(\sqrt{N_j{\sigma }_N}\right)d\Delta E}$$

. $$$$

$${\epsilon }_j\ge {\displaystyle \underset{\pm N_j\Delta C_j}{\overset{\pm \infty }{\int }}P\left(\sqrt{N_j{\sigma }_N}\right)d\Delta E}$$

.

(определяется экспериментально при каждом цикле принятия решений схемы 11), заданной вероятности ложных решений ε_j (например, 0,01) и расчетной оценке сигнала ΔC_j, от предвестника ЧС при нормальном распределении $$P\left(\sqrt{N\cdot {\sigma }_N}\right)$$

последовательное задание числа N_j позволяет определить его величину при решении приведенного уравнения. Эта функция возложена на микроконтроллер 12.With knowledge of noise energy estimates $${\sigma }_N^2$$

(determined experimentally for each decision-making cycle of scheme 11), the given probability of false decisions ε _j (for example, 0.01) and the estimated signal ΔC _j from the emergency precursor with a normal distribution $$P\left(\sqrt{N\cdot {\sigma }_N}\right)$$

sequential task of the number N _j allows you to determine its value when solving the above equation. This function is assigned to the microcontroller 12.

The found values of N ₁ and N ₂ are supplied to the decision-making device with its simultaneous start-up (signal “Sin”). The corresponding drives 13 and 14 summarize the N ₁ and N ₂ input samples; when these sums exceed the thresholds N ₁ ΔC _y and N ₂ ΔC _{bp, the} resolving devices 15, 16, 17, 18 generate “Decision” signals.

. Изменения режима перекачки, усиление ветра меняют показатель σ_N, а через него N_1, N₂. В результате поддерживается заданная вероятность ложных решений при обнаружении исходных изменений на продуктопроводе не ниже заданных при любых отклонениях параметров системы перекачки продуктов и погодных условий.Decision thresholds are determined by the numbers N ₁ and N ₂ , which are calculated by the current variance $${\sigma }_N^2$$

. Changes in the pumping mode, wind amplification change the σ _N index, and through it N _1, N ₂ . As a result, the specified probability of false decisions is maintained when the initial changes in the product pipeline are detected not lower than those set for any deviations in the parameters of the product transfer system and weather conditions.

Claims (1)

A method for detecting emergency precursors on the linear part of underground trunk pipelines, based on the excitation of ringing pulses of elastic vibrations in a selected section of the pipe shell, registering them at a distance from the excitation cross section, accumulating a certain number of recorded pulses in the next cycle of sequentially taken decisions, forming standards for emergency precursors and making decisions on the results of comparing the results of accumulation with standards, excellent schiysya that pulses registration is performed in two sections of the shell product pipeline removed at the same distance on both sides of the cross section of the excitation, the result of accumulation is obtained as the sum of the integrals of counts on the differences of these pulses, the number of accumulations N _j in the cycle is determined by solving the equation

,
where ε _j is the probability of false decisions for the j-th harbinger of an emergency, N _j is the number of accumulations for the j-th harbinger of an emergency; ΔC _j - estimated estimate of the level of the expected signal at the registration points,

is the normal probability density with zero mathematical expectation, σ _ΔE is the standard deviation of the recorded samples of these integrals ΔE, the levels ± N _j ΔC _j are used as standards, and the decision on the occurrence of the j-th harbinger of an emergency is made when the result set for the cycle is exceeded reference levels, and the “Insert" solution is transformed into an alarm signal through a loudspeaker installed in each section, and the signals of all decisions made are transmitted to the mnemonic circuit in security service via telemechanics channels.

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