阅读说明：本技术 管道应变监测预警系统及方法 (Pipeline strain monitoring and early warning system and method ) 是由 赵毅 滕建强 叶帆 刘冀宁 赵德银 姚彬 邱海峰 钟荣强 李鹏 杨思远 常小虎 于 2020-04-21 设计创作，主要内容包括：本发明提供一种管道应变监测预警系统,其包含：弹性监测杆件,系统包含两条弹性监测杆件,对称设置在待监测管段的两侧,采用矩形中空截面设计,中空截面的两侧外壁设有矩形凹槽；传感光纤,包含两条传感光纤,分别设置在两条弹性监测杆件的矩形凹槽内；多通道切换模块,与传感光纤连接,用于在两条传感光纤之间进行通道切换；分布式光纤应变解调仪,与多通道切换模块连接,用于发出探测激光并接收反馈信号；连接光纤,其用于连接分布式光纤应变解调仪与多通道切换模块、多通道切换模块与传感光纤。本发明提出了监测预警系统的布设方案,对采集系统获取的数据进行分析,为管道到结构安全提供依据,实现准确、全面的管道结构健康监测和安全预警。(The invention provides a pipeline strain monitoring and early warning system, which comprises: the system comprises two elastic monitoring rod pieces which are symmetrically arranged on two sides of a pipe section to be monitored, the design of a rectangular hollow section is adopted, and rectangular grooves are formed in the outer walls of two sides of the hollow section; the sensing optical fibers comprise two sensing optical fibers which are respectively arranged in the rectangular grooves of the two elastic monitoring rod pieces; the multi-channel switching module is connected with the sensing optical fibers and used for switching channels between the two sensing optical fibers; the distributed optical fiber strain demodulator is connected with the multi-channel switching module and is used for sending detection laser and receiving feedback signals; and the connecting optical fiber is used for connecting the distributed optical fiber strain demodulator with the multi-channel switching module, the multi-channel switching module and the sensing optical fiber. The invention provides a layout scheme of a monitoring and early warning system, analyzes data acquired by an acquisition system, provides a basis for pipeline to structure safety, and realizes accurate and comprehensive pipeline structure health monitoring and safety early warning.)

1. A pipeline strain monitoring and early warning system, the system comprising:

the system comprises two elastic monitoring rod pieces which are symmetrically arranged on two sides of a pipe section to be monitored, the length of each elastic monitoring rod piece is the same as that of the pipe section to be monitored, the elastic monitoring rod pieces are designed to be rectangular hollow sections, and rectangular grooves are formed in the outer walls of two sides of each hollow section;

the system comprises two sensing optical fibers which are respectively arranged in rectangular grooves of the two elastic monitoring rod pieces, each sensing optical fiber is symmetrically folded back, and the length of each sensing optical fiber is twice of that of the pipe section to be monitored;

the multi-channel switching module is connected with the sensing optical fibers and used for switching channels between the two sensing optical fibers;

the distributed optical fiber strain demodulator is connected with the multi-channel switching module and is used for sending out detection laser and receiving feedback signals;

and the connecting optical fiber is used for connecting the distributed optical fiber strain demodulator with the multi-channel switching module, the multi-channel switching module and the sensing optical fiber.

2. The system of claim 1, further comprising an epoxy layer for routing the sensing fibers.

3. The system of claim 1, wherein each of the elasticity monitoring rods is disposed at a waist of the pipe section to be monitored, and is linearly spaced from an outer wall of the pipe section to be monitored by a first predetermined length.

4. The system of claim 1, wherein the connecting fiber and the sensing fiber are single mode fibers.

5. A pipeline strain monitoring and early warning method, which is characterized in that pipeline strain monitoring and early warning is carried out by the system as claimed in any one of claims 1 to 4, and comprises the following steps:

the method comprises the following steps: sending the detection laser to an incident section sensing optical fiber through the distributed optical fiber strain demodulator, and receiving the feedback signal fed back by a return section sensing optical fiber, wherein each sensing optical fiber is divided into the incident section sensing optical fiber and the return section sensing optical fiber;

step two: and carrying out strain analysis on the feedback signals to respectively obtain the axis distributed bending strains of the two elastic monitoring rod pieces so as to evaluate the safety condition of the pipe section to be monitored and send out early warning when risks exist.

6. The method of claim 5, wherein prior to step one, the method further comprises: and when the monitoring and early warning system is arranged, the feedback signal is inverted based on the length of the pipe section to be monitored, so that the incidence direction of the feedback signal is consistent with that of the detection laser.

7. The method of claim 5, wherein the distributed strain of the incident segment sensing fiber is calculated by the following equation:

ε_f1(x)＝ε_M(x)+ε_N(x)+ε_OT(x)

wherein epsilon_f1(x) Representing the distributed strain, ε, of the sensing fiber at the incident section_M(x) Denotes the bending strain, ε, caused by lateral bending_N(x) Representing strain, ε, caused by axial force_OT(x) Indicating strain due to photothermal effects.

8. The method of claim 7, wherein the distributed strain of the return segment sensing fiber is calculated by the formula:

ε_f2(x)＝-ε_M(x)+ε_N(x)+ε_OT(x)

wherein epsilon_f2(x) The return segment senses the distributed strain of the optical fiber.

9. The method of claim 8, wherein the axial distributed bending strain of each of said elastic rod members is calculated by the following formula:

wherein epsilon_BM1(x) And the axial distributed bending strain of each elastic rod piece is represented.

10. The method of claim 5, wherein channel switching is performed by the multi-channel switching module to obtain axial distributed bending strains of the two elastic monitoring rods respectively.

Technical Field

The invention relates to the technical field of pipeline structure safety monitoring, in particular to a pipeline strain monitoring and early warning system and method.

Background

With the rapid development of modern construction, the energy demand is increasing day by day. The pipeline is used as a main mode of oil and gas transmission and is a 'life line engineering' system for oil and gas resource development. As national economy and social development have become increasingly dependent on oil and gas pipelines, the sensitivity of pipeline safety to economic, environmental and social stability has become increasingly important, and the service safety of oil and gas pipelines has become a focus of public, government and enterprise attention.

However, with the increase of pipelines and the increase of the age of the pipelines, the long-term action of various complex factors in the service process of the pipelines, the degradation phenomenon of the structural state of the pipelines commonly exists, and pipeline safety accidents happen sometimes, which causes great threats to the life, property safety, ecological environment and the like of people. Therefore, the advanced technical means of pipeline on-site monitoring and fine detection are urgently needed to be researched and developed, the structural state of the pipeline is evaluated in real time, the residual life of the pipeline is predicted quantitatively, decision support is provided for the safe operation of the whole life cycle of the pipeline, and scientific and technological support is provided for improving the benefit of an oil-gas pipe network and preventing public safety accidents.

Therefore, the invention provides a pipeline strain monitoring and early warning system and a pipeline strain monitoring and early warning method.

Disclosure of Invention

In order to solve the above problems, the present invention provides a pipeline strain monitoring and early warning system, which comprises:

the system comprises two elastic monitoring rod pieces which are symmetrically arranged on two sides of a pipe section to be monitored, the length of each elastic monitoring rod piece is the same as that of the pipe section to be monitored, the elastic monitoring rod pieces are designed to be rectangular hollow sections, and rectangular grooves are formed in the outer walls of two sides of each hollow section;

the system comprises two sensing optical fibers which are respectively arranged in rectangular grooves of the two elastic monitoring rod pieces, each sensing optical fiber is symmetrically folded back, and the length of each sensing optical fiber is twice of that of the pipe section to be monitored;

the multi-channel switching module is connected with the sensing optical fibers and used for switching channels between the two sensing optical fibers;

the distributed optical fiber strain demodulator is connected with the multi-channel switching module and is used for sending out detection laser and receiving feedback signals;

and the connecting optical fiber is used for connecting the distributed optical fiber strain demodulator with the multi-channel switching module, the multi-channel switching module and the sensing optical fiber.

According to one embodiment of the invention, the system further comprises an epoxy layer for routing the sensing fiber.

According to an embodiment of the present invention, each elasticity monitoring rod is disposed at a waist of the pipe section to be monitored, and a linear distance from an outer wall of the pipe section to be monitored is a first preset length.

According to one embodiment of the invention, the connecting fiber and the sensing fiber are single mode fibers.

According to another aspect of the present invention, there is provided a pipeline strain monitoring and early warning method, which performs pipeline strain monitoring and early warning through the system as described in any one of the above, including the following steps:

the method comprises the following steps: sending the detection laser to an incident section sensing optical fiber through the distributed optical fiber strain demodulator, and receiving the feedback signal fed back by a return section sensing optical fiber, wherein each sensing optical fiber is divided into the incident section sensing optical fiber and the return section sensing optical fiber;

step two: and carrying out strain analysis on the feedback signals to respectively obtain the axis distributed bending strains of the two elastic monitoring rod pieces so as to evaluate the safety condition of the pipe section to be monitored and send out early warning when risks exist.

According to an embodiment of the present invention, before the first step, the method further comprises: and when the monitoring and early warning system is arranged, the feedback signal is inverted based on the length of the pipe section to be monitored, so that the incidence direction of the feedback signal is consistent with that of the detection laser.

According to one embodiment of the present invention, the distributed strain of the sensing fiber at the incident section is calculated by the following formula:

ε_f1(x)＝ε_M(x)+ε_N(x)+ε_OT(x)

wherein epsilon_f1(x) Representing the distributed strain, ε, of the sensing fiber at the incident section_M(x) Denotes the bending strain, ε, caused by lateral bending_N(x) Representing strain, ε, caused by axial force_OT(x) Indicating strain due to photothermal effects.

According to one embodiment of the invention, the distributed strain of the return segment sensing fiber is calculated by the following formula:

ε_f2(x)＝-ε_M(x)+ε_N(x)+ε_OT(x)

wherein epsilon_f2(x) The return leg sensingDistributed strain of the optical fiber.

According to an embodiment of the present invention, the axial distributed bending strain of each elastic rod is calculated by the following formula:

wherein epsilon_BM1(x) And the axial distributed bending strain of each elastic rod piece is represented.

According to an embodiment of the invention, the multichannel switching module is used for switching channels to respectively obtain the axial distributed bending strains of the two elastic monitoring rod pieces.

The pipeline strain monitoring and early warning system and the pipeline strain monitoring and early warning method provided by the invention overcome the problems of insufficient precision, large environmental influence, incapability of accurately obtaining the real response of the pipeline structure of the pipeline under the action of quicksand and the like in the existing monitoring technology and means, adopt the distributed optical fiber strain sensor to monitor the quicksand change around the pipeline along the way, provide a layout scheme of the monitoring and early warning system, analyze the data obtained by the acquisition system, provide a basis for the pipeline to structure safety, and realize accurate and comprehensive pipeline structure health monitoring and safety early warning.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 shows a schematic structural diagram of a pipeline strain monitoring and early warning system according to an embodiment of the invention;

FIG. 2 is a schematic cross-sectional view of an elastic monitoring rod in a pipeline strain monitoring and early warning system according to an embodiment of the invention;

FIG. 3 is a schematic diagram illustrating the arrangement of sensing optical fibers in a pipeline strain monitoring and early warning system according to an embodiment of the present invention; and

fig. 4 shows a flowchart of a pipeline strain monitoring and early warning method according to an embodiment of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention are described in further detail below with reference to the accompanying drawings.

The invention aims at the field of pipeline safety monitoring and solves the problems of monitoring and early warning of pipeline bending stress under the action of a flowing dune. For example, in the north-cis oil and gas fields of China, the Tukrama dry sand desert is in the abdominal land, the sand storm frequently occurs in the desert, the annual average sand storm occurs for more than 30 days, and the annual moving distance of a moving sand dune is 20-30m in a moving sand dune area. The damage of the moving dune to the pipeline mainly comprises settlement and buckling deformation, and the pipeline can be broken by stress in serious conditions, so that serious accidents are caused. The pipeline strain monitoring is developed, the basis for mastering the pipeline strain real-time data is provided, reliable data support can be provided for pipeline design, construction and operation, the long-period safety of the pipeline is guaranteed, and casualties and economic losses caused by pipeline failure are reduced.

At present, response monitoring of pipeline structures at home and abroad mainly comprises deformation monitoring and structural bearing capacity monitoring, wherein a method for monitoring the deformation of a pipeline section mainly adopts a geometric leveling/total station measurement method, and the integral deformation condition of the pipeline is identified through the change of monitoring points on the pipeline. However, the pipeline monitoring technology including the application of the static level gauge and the GPS technology plays a certain role in the safe operation of the pipeline, but the defects of limited deformation monitoring points, small range, low precision, large environmental interference and the like limit the wide application of the pipeline monitoring technology.

In addition, two methods, namely a vibrating wire type strain gauge and a Fiber Bragg Grating (FBG) strain gauge, are mainly adopted for detecting the stress of the pipeline. The main challenge of this aspect is that the bending behavior of the pipeline caused by settlement and load has strong uncertainty, and the position where the maximum stress occurs and the evolution behavior are difficult to determine in advance, so that it is difficult to completely obtain the stress field change condition of the pipeline by only arranging stress sensors (vibrating wire type or fiber grating type) at limited positions, and the safety assessment made according to the change condition cannot reflect the real stress state of the pipeline.

Fig. 1 shows a schematic structural diagram of a pipeline strain monitoring and early warning system according to an embodiment of the invention.

As shown in fig. 1, the monitoring and early warning system includes: the device comprises a distributed optical fiber strain demodulator 1, a multi-channel switching module 2, a connecting optical fiber 3, a sensing optical fiber 4 and an elastic monitoring rod piece 5.

The distributed optical fiber strain demodulator (BOTDA/ROTDA)1 is connected with the multi-channel switching module 2, and is used for emitting detection laser and receiving feedback signals.

As shown in fig. 1, the multi-channel switching module 2 is connected to the sensing fibers 4 for switching channels between two sensing fibers 4. Specifically, the multi-channel switching module 2 switches the distributed optical fiber strain regulators 1 and the different sensing optical fibers 4.

As shown in fig. 1, the connection optical fiber 3 is used to connect the distributed optical fiber strain demodulator 1 with the multi-channel switching module 2, the multi-channel switching module 2 with the sensing optical fiber 4.

As shown in fig. 1, the sensing optical fibers 4, the monitoring and early warning system, comprise two sensing optical fibers 4, which are respectively arranged in the rectangular grooves of the two elastic monitoring rod members 1, each sensing optical fiber 4 is symmetrically folded back and arranged, and the length of each sensing optical fiber 4 is twice of that of the pipe section 7 to be monitored.

As shown in fig. 3, the sensing fibers 4 are symmetrically folded back, the connecting segments are respectively connected with the connecting fibers 3 and arranged in the elastic monitoring rod 5, the length of each sensing fiber 4 is twice of that of the segment 7 to be monitored, and each sensing fiber can be divided into an incident segment sensing fiber and a return segment sensing fiber.

In one embodiment, the connecting fiber 3 and the sensing fiber 4 are single mode fibers.

As shown in fig. 1, the elastic monitoring rod 5 comprises two elastic monitoring rods 5 in the monitoring and early warning system, the two elastic monitoring rods 5 are symmetrically arranged on two sides of the pipe section 7 to be monitored, the length of each elastic monitoring rod 5 is the same as that of the pipe section 7 to be monitored, as shown in fig. 2, the elastic monitoring rods 5 are designed to be rectangular hollow sections, and the outer walls of two sides of each hollow section are provided with rectangular grooves.

In one embodiment, each elastic monitoring rod 5 is arranged at the waist of the pipe section 7 to be monitored, and is at a first preset length from the outer wall of the pipe section 7 to be monitored. Specifically, the first preset length may be 2m, and in application, a value of the first preset length may be adjusted according to an actual situation, which is not limited in the present invention.

Specifically, the elasticity monitoring rod 5 is a rectangular hollow high-elasticity rod, the length of the elasticity monitoring rod is consistent with that of the pipe section 7 to be monitored, as shown in fig. 2, a sensing optical fiber 4 is embedded in two sides of the elasticity monitoring rod 5 through an epoxy resin layer 6, and the elasticity monitoring rod is symmetrically arranged at the pipe waist of the pipe section 7 to be monitored and is located at the position 2m of the outer wall.

In one embodiment, the monitoring and pre-warning system further comprises an epoxy layer 6 for laying the sensing fiber 4.

To summarize, the present invention uses two distributed optical fiber strain sensors (i.e. sensing fibers 4), each having twice the length of the pipe section 7 to be monitored, attached to the elastic monitoring rod 5 through the epoxy layer 6. The length of the elastic monitoring rod 5 is consistent with that of the pipe section 7 to be monitored, and the sensing optical fibers 4 are symmetrically folded and distributed. The elastic monitoring rod piece 5 is designed to be a rectangular hollow section, rectangular grooves are formed in the outer walls of the two sides of the elastic monitoring rod piece and used for arranging the sensing optical fibers 4, and the sensing optical fibers are packaged through the epoxy resin layer 6.

Fig. 4 shows a flow chart of a pipeline strain monitoring and early warning method according to an embodiment of the invention.

As shown in fig. 4, in step S401, a detection laser is emitted to an incident segment sensing fiber through a distributed fiber strain demodulator, and the feedback signal fed back by a return segment sensing fiber is received, where each sensing fiber is divided into an incident segment sensing fiber and a return segment sensing fiber.

Specifically, detection laser is emitted through a distributed optical fiber strain demodulator (BOTDA/ROTDA)1, enters a multichannel switching module 2 through a connecting optical fiber 3, enters sensing optical fibers 4 on two sides of a pipeline 7 to be monitored through the connecting optical fiber 3 according to the setting of the multichannel switching module 2, and collects backscattered light in the sensing optical fibers 4, wherein the backscattered light is a feedback signal in one embodiment.

Specifically, as shown in fig. 3, each sensing fiber 4 can be divided into an incident sensing fiber and a return sensing fiber due to the symmetrical folding arrangement, the incident sensing fiber receives incident detection laser, and the return sensing fiber returns back scattered light.

In summary, the distributed optical fiber strain sensor is adopted to monitor the drift sand change of the pipeline along the way, the arrangement scheme of the monitoring and early warning system and the special design of the elastic rod optical fiber sensor are adopted, the turn-back arrangement, the hollow rectangular section design, the sensing optical fiber arrangement scheme and the wiring design are adopted, the data acquired by the acquisition system are analyzed, the basis is provided for the structural safety of the pipeline, and the accurate and comprehensive pipeline structure health monitoring and safety early warning are realized.

As shown in fig. 4, in step S402, the feedback signal is subjected to strain analysis to obtain the axis distributed bending strains of the two elastic monitoring rods, so as to evaluate the safety condition of the pipe section to be monitored, and send out an early warning when there is a risk.

Specifically, when the sand dune flowing around the pipe 7 to be monitored changes, the elastic monitoring rod 5 is laterally bent and deformed therewith. Since the epoxy layer 6 enables the sensing fiber 4 to change along with the change, the response change condition of the elastic monitoring rod 5 under the action of the quicksand can be obtained by monitoring the back scattered light in the sensing fiber 4.

In general, the strain in the sensing fiber 4 is caused by three loads, respectively lateral bending induced bending strain ε_MStrain epsilon caused by axial force_NAnd strain epsilon due to photothermal effect_OT。

Specifically, the distributed strain of the sensing fiber at the incident section is calculated by the following formula:

ε_f1(x)＝ε_M(x)+ε_N(x)+ε_OT(x)

wherein epsilon_f1(x) Representing distributed strain, ε, of the sensing fiber at the incident section_M(x) Denotes the bending strain, ε, caused by lateral bending_N(x) Representing strain, ε, caused by axial force_OT(x) Indicating strain due to photothermal effects.

Specifically, from the cross-sectional form and the bending strain characteristic of the elastic monitoring rod 5, the distributed strain of the sensing fiber at the return section is calculated by the following formula:

ε_f2(x)＝-ε_M(x)+ε_N(x)+ε_OT(x)

wherein epsilon_f2(x) The return segment senses the distributed strain of the optical fiber.

Further, according to the sectional form of the elastic monitoring rod 5 and the strain composition analysis of the sensing optical fibers at the incident end and the return end, the axis distributed bending strain of each elastic rod is calculated by the following formula:

wherein epsilon_BM1(x) The axial distributed bending strain of each elastic rod piece is shown.

In summary, the above method can obtain the strain epsilon of the elastic monitoring rod 5 under the pure bending action_M(x) And the effect degree and the influence of the quicksand on the pipe section 7 to be monitored are monitored.

In one embodiment, the channel switching module 2 performs channel switching to obtain the axial distributed bending strains of the two elastic monitoring rods 5 respectively.

In one embodiment, before step S401, when the monitoring and early warning system is deployed, the feedback signal is inverted based on the length of the pipe segment to be monitored, so that the feedback signal is consistent with the incident direction of the detection laser.

Specifically, the purpose of the above steps is to ensure that: when a monitoring and early warning system is arranged, the incident section sensing optical fiber and the return section sensing optical fiber are kept in a parallel state, and the direction of incident detection laser is consistent with that of a return feedback signal.

In conclusion, the bending strain of the elastic monitoring rod 5 at a certain distance from the two sides of the pipeline 7 to be monitored can be monitored and analyzed, so that the quicksand action degree and the influence can be monitored, and the safety of the pipeline 7 to be monitored can be evaluated; meanwhile, the elastic monitoring rod piece 5 is still at a certain distance from the pipeline in the arrangement position, so that the function of early warning on the sand convection can be achieved, and the function of early warning on the pipeline risk is realized.

In conclusion, the pipeline strain monitoring and early warning system and the pipeline strain monitoring and early warning method provided by the invention overcome the problems of insufficient precision, large environmental influence, incapability of accurately obtaining real pipeline structure response of a pipeline under the action of quicksand and the like in the existing monitoring technology and means, adopt the distributed optical fiber strain sensor to monitor the quicksand change around the pipeline section to be detected along the way, and provide a layout scheme of the monitoring and early warning system.

It is to be understood that the disclosed embodiments of the invention are not limited to the particular structures, process steps, or materials disclosed herein but are extended to equivalents thereof as would be understood by those ordinarily skilled in the relevant arts. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

Reference in the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrase "one embodiment" or "an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment.

Although the embodiments of the present invention have been described above, the above description is only for the convenience of understanding the present invention, and is not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.