CN119959120A - A pipeline corrosion monitoring method and system based on φ-OTDR - Google Patents
A pipeline corrosion monitoring method and system based on φ-OTDR Download PDFInfo
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Abstract
本发明公开了一种基于φ‑OTDR的管道腐蚀监测方法及系统，涉及工程监测技术领域，方法为：安装光纤；利用光纤接收发射的光信号，并将光信号产生的背向瑞利散射光传送至管道腐蚀监测系统进行分析；对接收到的背向瑞利散射光信号进行处理；根据处理结果，进行预警和实时监测。系统包括光纤、管道以及控制主机，控制主机通过绕设在管道上的光纤实现监测管道腐蚀的情况。本发明通过采用基于φ‑OTDR技术的管道腐蚀监测系统，能够实现对管道腐蚀的实时、连续、高精度监测，从而及时发现并预防潜在的管道泄漏和破裂风险，显著提高管道的安全性和可靠性，同时降低维护成本和提高监测效率。
The present invention discloses a pipeline corrosion monitoring method and system based on φ‑OTDR, which relates to the field of engineering monitoring technology. The method comprises: installing an optical fiber; using the optical fiber to receive the emitted optical signal, and transmitting the back-scattered Rayleigh light generated by the optical signal to the pipeline corrosion monitoring system for analysis; processing the received back-scattered Rayleigh light signal; and performing early warning and real-time monitoring according to the processing result. The system comprises an optical fiber, a pipeline and a control host, and the control host monitors the pipeline corrosion through the optical fiber wound around the pipeline. The present invention can realize real-time, continuous and high-precision monitoring of pipeline corrosion by adopting a pipeline corrosion monitoring system based on φ‑OTDR technology, thereby timely discovering and preventing potential pipeline leakage and rupture risks, significantly improving the safety and reliability of the pipeline, while reducing maintenance costs and improving monitoring efficiency.
Description
Technical Field
The invention relates to the technical field of engineering monitoring, in particular to a pipeline corrosion monitoring method and system based on phi-OTDR.
Background
Currently, pipe corrosion monitoring relies primarily on periodic physical inspection or the use of electrochemical sensors and the like. These methods suffer from the disadvantages of discontinuous monitoring, high cost, difficulty in real-time monitoring, etc., and are difficult to implement for long distance or difficult to reach pipelines, which have limitations in monitoring. In addition, the existing monitoring technology generally cannot provide high-precision corrosion data, and small corrosion changes are difficult to discover in time, so that the safety and reliability of the pipeline are affected.
Accordingly, there is a need for a system and method that can monitor corrosion of a pipe in real-time, continuously, and accurately to improve the safety and reliability of the pipe.
Disclosure of Invention
Aiming at the problems of discontinuous monitoring, high cost, difficult real-time monitoring and low monitoring precision existing in the pipeline corrosion monitoring method in the prior art, the invention provides a pipeline corrosion monitoring method and system based on phi-OTDR.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a pipeline corrosion monitoring method based on phi-OTDR comprises the following steps of S1, installing an optical fiber, S2, receiving an emitted optical signal by the optical fiber, transmitting back Rayleigh scattered light generated by the optical signal to a pipeline corrosion monitoring system for analysis, S3, processing the received back Rayleigh scattered light signal, S4, monitoring and comprehensively judging whether corrosion occurs according to the analysis result of the S2 and the processing result of the S3, and carrying out early warning.
Based on the above technical solution, in step S2, the back rayleigh scattered light is analyzed from the angles of phase change, intensity change, spectrum characteristics, real-time alarm and positioning.
Based on the technical scheme, the analysis process under the angle of the frequency spectrum characteristic comprises the steps of firstly emitting light pulses and then collecting back Rayleigh scattered light, wherein the analysis process comprises phase information extraction, data analysis and phase change analysis during collection, and the data analysis comprises phase difference measurement, phase transformation amplitude and phase change rate analysis.
Based on the above technical scheme, in step S3, the received dorsally rayleigh scattering optical signal is amplified, filtered and digitized, then the characteristic information in the signal is extracted, wherein when the characteristic information in the signal is extracted, the method of time domain analysis is firstly adopted to primarily screen out the potential abnormal region, then the method of frequency domain analysis is adopted to confirm whether the periodic vibration source exists, finally the wavelet transformation is adopted to accurately position and characterize the spatial distribution characteristics of the vibrations, wherein if the phase change of a certain region is gradually increased, the region is set as the potential abnormal region with corrosion.
Based on the technical scheme, in step S3, phi-OTDR is adopted to monitor the change condition of amplitude parameters, and then whether corrosion occurs is judged, wherein the judging process is that the amplitude is the signal intensity of the back Rayleigh scattered light, the reference interval is the initial measured value of a newly built or well maintained pipeline section as a benchmark, the normal fluctuation range is within +/-3 dB, and corrosion is considered to occur when the continuous change exceeding +/-3 dB.
Based on the above technical scheme, in step S3, phi-OTDR is adopted to monitor the change condition of frequency parameters, and then whether corrosion occurs is judged, wherein the judging process is that the frequency is the repetition rate of vibration or stress wave, the reference interval is the natural vibration frequency of an undamaged pipeline, the specific numerical value depends on the pipeline design and the environmental condition, and when deviation of more than +/-5% relative to the reference value occurs, the abnormal sign is considered.
Based on the above technical scheme, in step S3, phi-OTDR is adopted to monitor the change condition of the phase parameter, and then whether corrosion occurs is judged, wherein the judging process is that the phase is the relative time difference between two waveforms with the same frequency, the initial phase reading of the optical fiber installation is used as a standard, the optical fiber installation is smooth and stable, and early warning occurs when the phase difference of a certain section of pipeline suddenly increases by more than 0.1 radian or periodic fluctuation occurs.
Based on the above technical solution, in step S4, it is further required to determine whether the signal features are similar and further determine whether to issue an alarm, where the similarity determination process determines from amplitude fluctuation, frequency distribution and phase stability.
A pipeline corrosion monitoring system based on phi-OTDR comprises an optical fiber, a pipeline and a control host, wherein the control host monitors the pipeline corrosion through the optical fiber wound on the pipeline.
Based on the technical scheme, the control host comprises a receiver, a transmitter, a signal characteristic library, a data acquisition and processing unit and an early warning and monitoring unit, wherein the transmitter is used for transmitting a light source, the receiver is used for receiving backward Rayleigh scattered light generated by an optical fiber, the signal characteristic library is used for storing signal characteristic data as a reference basis for signal judgment, the data acquisition and processing unit is used for amplifying, filtering and digitally processing signals, and the early warning and monitoring unit is used for monitoring pipeline corrosion conditions in real time and carrying out early warning and reminding.
Compared with the prior art, the invention has the following beneficial effects:
The pipeline corrosion monitoring system based on the phi-OTDR technology can realize real-time, continuous and high-precision monitoring of pipeline corrosion, so that potential pipeline leakage and cracking risks can be found and prevented in time, the safety and reliability of the pipeline are obviously improved, and meanwhile, the maintenance cost and the monitoring efficiency are reduced.
Drawings
FIG. 1 is a flow chart of a monitoring method of the present invention;
FIG. 2 is a simplified diagram of a monitoring system of the present invention;
reference numeral 1, optical fiber, 2, pipeline, 3, control host.
Detailed Description
The invention is further illustrated and described below with reference to the drawings and detailed description. The technical features of the embodiments of the invention can be combined correspondingly on the premise of no mutual conflict.
In order that the above objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the invention, whereby the invention is not limited to the specific embodiments disclosed below. The technical features of the embodiments of the invention can be combined correspondingly on the premise of no mutual conflict.
In the description of the present invention, it will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or be indirectly connected with intervening elements present. In contrast, when an element is referred to as being "directly connected" to another element, there are no intervening elements present.
Example 1
The phase sensitive optical time domain reflectometer (phi-OTDR) adopts a distributed optical fiber sensing technology based on Rayleigh scattering, when light propagates in the optical fiber 1, rayleigh scattering can be generated due to uneven refractive index in the optical fiber 1 and other reasons, and the phi-OTDR can sense the change of the external environment by detecting the phase change of the back Rayleigh scattering light.
The embodiment provides a pipeline corrosion monitoring method based on phi-OTDR, and the pipeline corrosion monitoring system based on phi-OTDR can detect the micro deformation of the pipeline with high sensitivity by utilizing the optical fiber sensing technology, so that the corrosion condition is deduced. The monitoring method not only can provide real-time data, but also has higher monitoring precision and lower maintenance cost, and is particularly suitable for monitoring pipelines which are long in distance or difficult to reach.
Referring to fig. 1, the monitoring method specifically includes the following steps:
Step S1, installing the optical fiber 1. Specifically, the optical fiber 1 may be laid along the pipe by directly adhering to the surface of the pipe 2, embedding in the pipe protective layer, or the like. When the environment around the pipe changes, the optical fiber 1 is also affected accordingly. Ensuring a firm installation of the optical fiber 1 and a good contact with the pipe 2 so that variations around the pipe can be accurately perceived.
And S2, receiving the transmitted optical signal by using the optical fiber 1, and transmitting the back Rayleigh scattered light generated by the optical signal to a pipeline corrosion monitoring system for analysis. Specifically, the light source in the pipe corrosion monitoring system in embodiment 2 emits a light pulse into the optical fiber 1, and the light pulse continuously generates back rayleigh scattered light when propagating in the optical fiber 1, and the receiver in the pipe corrosion monitoring system receives the back rayleigh scattered light and mainly analyzes the phase information carried by the back rayleigh scattering. Since phi-OTDR is very sensitive to the phase change of light, even a small phase change can be detected.
In this embodiment, the system for monitoring corrosion of a pipeline can analyze phase information carried in rayleigh scattering (RAYLEIGH SCATTERING), and when analyzing backscattered light, the system at least includes the following analysis angles:
Angle one, phase change, phi-OTDR, is the phase change that is produced by the interaction of an optical pulse with the surrounding environment as it propagates in the fiber 1. When corrosion of the pipe occurs, the material properties around the optical fiber 1 change, resulting in a change of the phase information.
The angle II and the intensity change phi-OTDR can be combined with the intensity change (such as the intensity of back scattered light) for comprehensive analysis besides the phase change, so as to improve the detection precision.
Angle three, spectral characteristics-in some cases, the pipe corrosion monitoring system also analyzes the spectral characteristics of the backscattered light, particularly Brillouin scattering (Brillouin Scattering) or Raman scattering (RAMAN SCATTERING), which can provide information about environmental parameters such as temperature, stress, etc., indirectly reflecting corrosion conditions.
In this embodiment, from angle one to angle three, the specific process of analyzing the backward Rayleigh scattered light by using the phi-OTDR monitoring value is as follows:
The method comprises the steps of firstly emitting light pulses, wherein a control host 3 is arranged in a pipeline corrosion monitoring system, a light source module is integrated in the control host 3, and the light source module emits laser pulses with narrow linewidth to enter a single-mode communication optical fiber 1.
And collecting the back Rayleigh scattered light, wherein during the collection, the analysis processes of phase information extraction, data analysis, phase change analysis and the like are involved, and the data analysis comprises the analysis processes of phase difference measurement, phase change amplitude and phase change rate. The method comprises the following steps:
(1) The phase change analysis is to analyze the amplitude and the rate of the phase change, and then calculate and obtain the corrosion rate. In particular, corrosion of the tube 2 occurs, resulting in a change in the refractive index of the optical signal passing through this region, or in a change in geometry around the optical fiber 1, which in turn affects the phase response.
Calculating the phase change: In the formula (I), in the formula (II), Indicating the phase difference between time t and the initial time; Is shown at the moment Is used for the phase value of (a),Representing the phase value at the initial time.
Determining a proportionality constant: wherein Δt represents a time difference between two times;
Calculating the corrosion rate: 。
(2) And phase difference measurement, namely extracting phase information by utilizing interference phenomenon by utilizing phi-OTDR to transmit optical pulses and receive returned back Rayleigh scattering optical signals. Assuming that the phase at a point in the fiber is Phase differenceCan be expressed as the phase difference between two adjacent points in time or space: In the formula, the compound of the formula, Is shown inPhase and time of dayA phase difference between phases at the time; Is shown at the moment Is used for the phase value of (a),Is shown at the momentIs a phase value of (a).
(3) Phase change amplitude the degree of phase change at a certain position is reflected by the phase change amplitude. Typically measured by calculating the maximum amount of phase change over a period of time or distance; In the formula (I), in the formula (II), Representing the amplitude of the phase change; Indicating the phase difference.
(4) Phase change Rate refers to the rate of change of phase per unit time that can be used to evaluate the rate of impact of corrosion or other environmental factors. Assuming that the phase varies with time t, the rate of phase variationIt can be obtained by taking the derivative:; representing the rate of phase change; representing the phase as a function of time t.
And alarming and positioning in real time, namely once the obvious phase change is detected, indicating that corrosion points possibly exist, immediately triggering an alarm by a pipeline corrosion monitoring system, accurately positioning the corrosion position through the phase change, and facilitating quick maintenance. In some embodiments, the significant phase change condition is defined as an amplitude change greater than + -3 db, a frequency change greater than + -5%, and a phase change greater than 0.1 radians.
And step S3, processing the received back Rayleigh scattered light signal. Specifically, the received back Rayleigh scattering optical signal is processed by a data acquisition and processing unit. The data acquisition and processing unit at least comprises an amplifier, a filter, an analog-to-digital converter and other devices and is used for amplifying, filtering and digitizing the back Rayleigh scattered light signals. Then, specific methods such as time domain analysis, frequency domain analysis, wavelet analysis and the like are adopted to extract characteristic information in the signals.
In the embodiment, the specific process of extracting the characteristic information in the signal by adopting the time domain analysis method is to perform denoising and smoothing processing on the original signal. Recalculating the mean μ and variance of the signalTo evaluate the overall level of the signal and its extent of fluctuation. The internal structure and periodicity of the signal are known by an autocorrelation function (ACF).
;
Wherein R (k) represents the autocorrelation coefficient of the lag k, x t represents the signal intensity at time t, μ represents the mean value of the signal, and finally the local maximum or minimum point in the signal is identified for peak detection, indicating the position where corrosion is likely to occur. For a one-dimensional signal x (t), x (t 0) is a peak point if x (t 0) > x (t 0- Δt) x (t 0) and x (t 0) > x (t0+Δt) x (t 0) are satisfied.
By performing time domain analysis on the time series data acquired by the phi-OTDR, the change mode of the phase along with time can be found, and potential corrosion activity can be deduced. For example, if the phase change of a certain area gradually increases, it may be that there is corrosion, that is, the area is considered as a potential abnormal area.
In the embodiment, the specific process of extracting the characteristic information in the signal by adopting the frequency domain analysis method comprises the following steps of converting a time domain signal into a frequency domain signal by using Fourier transform (FFT): Wherein X (f) represents the spectral density of the signal, X (t) represents the time domain signal, f represents the frequency variable, and j represents the imaginary unit. For discrete time signals, a Discrete Fourier Transform (DFT) is used to approximate a continuous fourier transform. The Power Spectral Density (PSD) estimate is used to calculate the energy distribution of each frequency component: Wherein Pxx (f) represents the power spectral density and |X (f) | represents the modulus of the frequency domain signal. When studying weak vibrations inside the pipe due to corrosion, frequency domain analysis can effectively separate these small but important frequency components, thereby assisting in judging the presence and severity of corrosion. In addition, frequency domain information may be used to perform fault diagnosis, such as distinguishing background noise under normal operating conditions from abnormal vibrations caused by corrosion, and thus to determine the vibration source.
In this embodiment, the specific process of extracting the characteristic information in the signal by using the wavelet analysis method is as follows:
In order to improve the accuracy, the monitoring system adopts wavelet analysis with higher flexibility than the traditional Fourier transform, has the advantage of multi-resolution decomposition, not only reserves the position information of a time domain, but also shows the characteristics of the frequency domain, and uses Discrete Wavelet Transform (DWT); Where c j [ k ] represents the wavelet coefficients at the j-th layer scale, x [ n ] represents the discrete time signal, and ψ j,k [ n ] represents the discrete wavelet basis functions.
Since DWT is able to resolve signals in both the time and frequency dimensions simultaneously, the precise location where vibration occurs can be effectively identified. In the pipe corrosion monitoring system, the reflected light signal is subjected to wavelet transformation, so that the position of the vibration occurrence point can be accurately positioned in the length direction of the optical fiber 1. In addition to spatial localization, wavelet analysis reveals the time-frequency characteristics of the vibrations. This is important to distinguish between different types of vibration sources, such as normal vibrations caused by natural environmental factors from abnormal vibrations caused by corrosion or other damage.
Wavelet analysis is well suited for analyzing signals containing complex dynamics, such as sudden stress changes, in a pipe corrosion monitoring scenario. The system can accurately locate the specific time and place of the events and provide guidance for subsequent maintenance work.
In order to obtain the most accurate result, the method combines the three modes to carry out comprehensive analysis, and the specific process comprises the steps of firstly using time domain analysis to preliminarily screen potential abnormal areas which can rapidly identify areas possibly with problems, then further confirming whether periodic vibration sources exist or not by means of frequency domain analysis, wherein the periodic vibration sources are used for deep research to confirm whether potential corrosion phenomena exist or not, and finally using wavelet transformation analysis to accurately position and characterize the spatial distribution characteristics of the vibration sources, wherein the spatial distribution characteristics are used for accurately positioning and provide detailed space-time distribution information. The method is further explained in that a time domain analysis is adopted to determine a potential abnormal region, a frequency domain analysis is utilized to analyze the potential abnormal region, if the frequency domain analysis is considered to be corrosion, subsequent operation is not carried out, if the frequency domain analysis is considered to be corrosion, a result and related information are transmitted downwards, wavelet transformation analysis is carried out, and finally the corrosion position is determined.
The method comprises the steps of winding a section of pipeline 2 which is ensured not to be corroded by using an optical fiber 1, testing relevant parameters, winding the optical fiber 1 onto the pipeline 2 to be tested, comparing parameters such as amplitude, phase and the like, analyzing the parameters by means of time domain, frequency domain, wavelet transformation and the like, and if the tested parameters are similar, not corroding, and if the tested parameters have larger phase difference, corroding. Further, particularly under the comparison conditions of newly built or undamaged pipeline sections with the same materials, environmental conditions and service lives, the signals at the moment are recorded and are compared with the signals of the test pipeline, and whether the pipeline is corroded or not and the corrosion degree can be judged. For example, phi-OTDR can be used to monitor the change of amplitude, frequency, phase and other parameters to determine whether corrosion occurs, and when the detected signal amplitude, frequency, phase and other parameters change greatly or change obviously in a short time, it can be deduced that the pipeline is likely to corrode.
In this embodiment, if one of the analysis results of the angles such as amplitude, frequency, and phase satisfies the condition, analysis of time domain, frequency domain, and wavelet transformation is performed, and if the final result is predicted to be corrosion, it is determined that corrosion is occurring. The process of analysis from three angles specifically is:
From an amplitude analysis perspective, in this embodiment, the amplitude is the signal intensity of the backward rayleigh scattered light, the reference interval is the initial measured value of the newly built or well maintained pipe section, the normal fluctuation range is within ±3dB, and the obvious change is a continuous change exceeding ±3dB, which may indicate corrosion or other damage.
From the perspective of frequency analysis, in this embodiment, the frequency is the repetition rate of the vibration or stress wave, the reference interval is the natural vibration frequency of the undamaged pipeline, and the specific value depends on the pipeline design and the environmental condition, and the obvious change is a sign that the deviation of more than +/-5% relative to the reference value is possibly abnormal.
From the phase analysis perspective, in this embodiment, the phase is the relative time difference between two waveforms with the same frequency, and the initial phase reading of the installation of the optical fiber 1 is used as a standard, so that the optical fiber is smooth and stable, and the obvious change is early warning when the phase difference of a certain section of pipeline suddenly increases by more than 0.1 radian or periodic fluctuation occurs. The optical fiber 1 surrounding the pipeline 2 can be used as a sensor, the optical fiber 1 surrounds the pipeline 2 for monitoring corrosion, a light source shines into the optical fiber 1, a returned optical signal carries relevant information, the optical signal is firstly analyzed by phi-OTDR, then the optical signal is further analyzed by algorithms such as wavelet analysis and the like, and finally a prediction result is output.
And S4, monitoring and comprehensively judging whether corrosion occurs according to the analysis result of the step S2 and the processing result of the step S3, and performing early warning. When the analysis result shows that the corrosion degree of the pipeline exceeds the set threshold value, the early warning system gives an alarm, and when the threshold value is set, the requirement is determined according to the design, the environmental condition, the service life and other parameters of the pipeline to be tested, in the embodiment, the amplitude fluctuation range is within +/-3 dB, the frequency deviation is less than +/-5%, the phase difference is less than 0.1 radian, and if one of the conditions meets the corresponding condition, the early warning system further analyzes, and judges whether the alarm is required to be given according to the analysis result. The alarm can inform related personnel by means of an audible and visual alarm, a short message, an email and the like. Meanwhile, the system can continuously monitor the pipeline, and update the evaluation result of the corrosion degree in real time, so that related personnel can take measures in time to repair or replace the pipeline.
In this embodiment, if corrosion of a section of pipeline 2 is monitored for a long time, the pipeline will generate an alarm signal due to non-corrosion, but the signal changes greatly in a short time, so that it is an interference signal, and it is necessary to record separately, if the signal is generated, the alarm is not performed, and if the signal is generated, it is necessary to establish a signal feature library in the monitoring system and perform calibration operation. Specifically, a signal feature library in a normal running state is established, and the signal feature library is used as a reference basis for judging whether false alarm is caused or not. The signal feature library includes, but is not limited to, signal amplitude, frequency, phase, etc., and may also be combined with data of pressure sensor, flow sensor, etc. as judgment basis to eliminate interference signal. For example, comparing the corrosion signal characteristics with the normal interference signal characteristics, if the change characteristics are similar to the signal characteristics caused by normal petroleum flow or external pressure, the preliminary judgment may be false alarm, specifically, whether corrosion occurs is mainly seen according to three signal characteristics of amplitude fluctuation, frequency distribution and phase stability, but corrosion alarm is sometimes seen by combining with other parameters, and sometimes, the three parameters are similar to the corrosion characteristics, history records need to be seen, whether corrosion occurs once is compared, and if corrosion does not occur, the corrosion may occur.
In this embodiment, the corrosion signal characteristics are understood to be localized material losses, gradual attenuation of reflected light signal amplitudes, changes in the pipe mechanical characteristics in the corrosion region, effects natural vibration frequencies or transfer functions, typically increases in low frequency content, and periodic or nonlinear changes in phase.
The normal disturbance signal characteristics are understood to be that the liquid flow type typically vibrates with a specific frequency range, and externally applied pressure waves cause transient stress relief or absorption, typically manifested as rapid and short amplitude fluctuations or frequency shifts at specific points in time.
In this embodiment, in determining that the signal characteristics are similar, the monitored signal may be considered similar to a signal caused by normal petroleum flow or external pressure when the monitored signal exhibits the following characteristics:
1) Amplitude fluctuations if a rapid, short-term, large amplitude change is observed, rather than a gradual decrease trend, which is more likely to be caused by oil flow or external pressure changes, rather than corrosion.
2) Frequency distribution-frequency changes due to corrosion tend to be slow and concentrated in lower frequency bands, whereas frequency changes caused by fluid flow or pressure fluctuations may involve a wider frequency band, especially in the high frequency part.
3) Phase stability-phase changes due to corrosion are typically irregular and persistent, whereas phase changes due to oil flow or external pressure changes tend to be temporary and can recover after a period of time.
In this embodiment, the process of determining the similarity method is that the current main approach is to combine multiple parameters and analyze the experience of the historical data summary. Relying solely on a parameter to make a decision may lead to erroneous conclusions. Therefore, information on multiple aspects of amplitude, frequency, phase and the like should be considered simultaneously, and correlation and consistency between the information should be found. In view of the environmental variables such as temperature, humidity, etc. which may also affect the signal, the influence of these sources of interference must be excluded during the analysis to ensure that the observed changes are indeed due to internal structural changes. Comparing the current signal with the data recorded under the same condition in the past to see if a similar mode exists. If the difference between the old and new data is not large, it is likely to be the result of normal operating conditions. At this time, although the signal characteristics are similar to those of the corrosion signal, no corrosion occurs. It is also necessary to compare the history of corrosion, if the history has signal characteristics in this mode and no corrosion has occurred, if new characteristics may have occurred.
In summary, the similarity determination process is determined by excluding the interference of the time domain analysis, the frequency domain analysis, and the wavelet analysis, but the three analyses are determined based on the amplitude fluctuation, the frequency distribution, and the phase stability. In step S3, whether corrosion occurs is determined by time domain analysis, frequency domain analysis, and wavelet analysis. Step S4, eliminating the similar interference and determining whether to alarm.
Specifically, the time domain analysis eliminates interference, namely short-term fluctuation and periodical change, and observes whether the short-term temporary quick recovery or obvious periodicity exists or not, and judges whether the short-term temporary quick recovery or the obvious periodicity exists or not.
Frequency domain analysis eliminates interference by distinguishing wideband noise from fixed frequency pulses, eliminating interference caused by fluid flow or pumping.
The wavelet analysis eliminates interference, namely transient events and periodic fluctuation are identified, and whether corrosion occurs or not is distinguished through the characteristic of detail coefficients after wavelet transformation.
In some embodiments, the chemical may suddenly appear due to the corrosion of the pipe, which may affect the soil condition around the optical cable, and the signal parameter may change, so that corrosion alarm may occur, which is not false alarm, or the chemical may be generated due to the slight corrosion of the pipe 2, but the chemical may cause the system to give out corrosion alarm in advance, and perhaps the pipe does not have obvious corrosion, but may have corrosion alarm, which is a false alarm. Specifically, pipe corrosion is detected by detecting a change in soil composition, which, when corroded, causes a series of changes in the surrounding environment. For example, corrosion may cause thinning of the pipe walls, thereby affecting the structural strength of the pipe. In this case, the pipe 2 may generate minute vibrations, and these vibration sources may be transmitted into the surrounding soil, thereby affecting the optical fiber 1 laid nearby. Some chemicals may be generated during the etching process, which may change the refractive index around the fiber, thereby affecting the propagation of light in the fiber. These variations can cause the optical phase in the fiber to change. The phi-OTDR can detect this phase change and convert it into an electrical signal for processing.
Example 2
Referring to fig. 2, the embodiment further provides a pipeline corrosion monitoring system based on phi-OTDR, which comprises an optical fiber 1, a pipeline 2 and a control host 3, wherein the control host 3 monitors the corrosion condition of the pipeline 2 through the optical fiber 1 wound on the pipeline 2.
Specifically, the control host 3 includes a receiver, a transmitter, a signal feature library, a data acquisition and processing unit, and an early warning monitoring unit. Further, the receiver is used for receiving the backward Rayleigh scattered light generated by the optical fiber 1, the transmitter is used as a light source module for transmitting light sources, the signal characteristic library is used for storing signal characteristic data as a reference basis for signal judgment, the data acquisition and processing unit comprises, but not limited to, an amplifier, a filter, an analog-to-digital converter and other devices for amplifying, filtering and digitizing the signals, and the early warning and monitoring unit is used for monitoring corrosion conditions of the pipeline 2 in real time and can perform early warning and reminding.
In this embodiment, the control host information transfer flow is as follows:
The optical pulse enters the optical fiber 1, the optical fiber 1 is wound around the corrosion monitoring pipeline 2, an optical pulse signal propagates in the optical fiber 1, the optical fiber 1 serves as a sensor, all signal information is brought back to a receiver of the control host 3 by the optical pulse, the receiver receives the optical signal and then transmits the optical signal to the data acquisition and processing unit, the data acquisition and processing unit calculates parameters such as amplitude, phase and the like, analysis is carried out through modes such as time domain, frequency spectrum and wavelet transformation, after the result parameters are analyzed, the analyzed result is compared with reference parameters of a signal characteristic library, finally, a comprehensive predicted value of the corrosion occurrence probability is provided, the comprehensive predicted value is compared with a threshold value set by the early warning monitoring unit, and early warning is carried out when the comprehensive predicted value is larger than the threshold value.
Finally, it should be noted that the above description is only for illustrating the technical solution of the present invention, and not for limiting the scope of the present invention, and that the simple modification and equivalent substitution of the technical solution of the present invention can be made by those skilled in the art without departing from the spirit and scope of the technical solution of the present invention.
Claims (10)
1. The pipeline corrosion monitoring method based on phi-OTDR is characterized by comprising the following steps of:
s1, installing an optical fiber;
s2, receiving the transmitted optical signals by utilizing optical fibers, and transmitting the back Rayleigh scattered light generated by the optical signals to a pipeline corrosion monitoring system for analysis;
S3, processing the received back Rayleigh scattered light signal;
And S4, monitoring and comprehensively judging whether corrosion occurs according to the analysis result of the step S2 and the processing result of the step S3, and performing early warning.
2. The method for monitoring corrosion of a pipeline based on phi-OTDR according to claim 1, wherein in step S2, the backward rayleigh scattered light is analyzed from the angles of phase change, intensity change, spectral characteristics, real-time alarm and positioning.
3. The method for monitoring pipeline corrosion based on phi-OTDR according to claim 2, wherein the analysis process under the angle of spectrum characteristic is to emit light pulse first and then collect back Rayleigh scattered light, wherein the analysis process involves phase information extraction, data analysis and phase change analysis during collection, and the data analysis includes analysis of phase difference measurement, phase change amplitude and phase change rate.
4. The method for monitoring pipeline corrosion based on phi-OTDR according to claim 1 is characterized in that in step S3, the received back Rayleigh scattering optical signal is amplified, filtered and digitized, characteristic information in the signal is extracted, when the characteristic information in the signal is extracted, a time domain analysis method is adopted to primarily screen out a potential abnormal region, a frequency domain analysis method is adopted to confirm whether a periodic vibration source exists, and finally wavelet transformation is adopted to accurately position and characterize the spatial distribution characteristic of the vibration source, wherein if the phase change of a certain region is gradually increased, the region is set to be the potential abnormal region with corrosion.
5. The method for monitoring pipeline corrosion based on phi-OTDR according to claim 4, wherein in step S3, the variation of amplitude parameter is monitored by adopting phi-OTDR to further judge whether corrosion occurs, the judging process is that the amplitude is the signal intensity of the backward Rayleigh scattered light, the reference interval is the initial measured value of the newly built or maintained pipeline section as a reference, the normal fluctuation range is within + -3 dB, and corrosion is considered to occur when the persistence variation exceeding + -3 dB.
6. The method of monitoring corrosion of pipeline based on phi-OTDR according to claim 5, wherein in step S3, the variation of frequency parameter is monitored by adopting phi-OTDR to further judge whether corrosion occurs, the judging process is that the frequency is the repetition rate of vibration or stress wave, the reference interval is the natural vibration frequency of undamaged pipeline, the specific value depends on the pipeline design and environmental condition, and when deviation of + -5% or more relative to the reference value occurs, the abnormal sign is considered.
7. The method for monitoring corrosion of pipeline based on phi-OTDR according to claim 6, wherein in step S3, phi-OTDR is adopted to monitor the change condition of phase parameter, and further judge whether corrosion occurs, the judging process is that the phase is the relative time difference between two waveforms with the same frequency, the initial phase reading of the optical fiber is taken as a standard, and when the phase difference of a pipeline of a certain section suddenly increases by more than 0.1 radian or periodic fluctuation occurs, early warning occurs.
8. The method according to claim 1, wherein in step S4, it is determined whether the signal characteristics are similar and whether an alarm is issued, and wherein the similarity determination process determines from amplitude fluctuation, frequency distribution and phase stability.
9. A phi-OTDR-based pipe corrosion monitoring system, characterized in that a phi-OTDR-based pipe corrosion monitoring method according to any one of claims 1 to 8 is performed, wherein the pipe corrosion monitoring system comprises an optical fiber, a pipe and a control host, and the control host monitors the pipe corrosion through the optical fiber wound around the pipe.
10. The system for monitoring corrosion of a pipeline based on phi-OTDR according to claim 9, wherein the control host comprises a receiver, a transmitter, a signal feature library, a data acquisition and processing unit and an early warning monitoring unit;
the emitter is used for emitting the light source;
The receiver is used for receiving the back Rayleigh scattered light generated by the optical fiber;
the signal feature library is used for storing signal feature data and is used as a reference basis for signal judgment;
the data acquisition and processing unit is used for amplifying, filtering and digitizing the signals;
the early warning monitoring unit is used for monitoring the corrosion condition of the pipeline in real time and carrying out early warning reminding.
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