Flexible composite pipe operation state monitoring system and operation method

Abstract

The invention discloses a flexible composite pipe operation state monitoring system and an operation method, and the system comprises a terminal device which is used for carrying out human-computer interaction and displaying monitoring data, and a signal line is connected with the terminal device and a demodulator; one end of the temperature optical fiber and one end of the strain optical fiber are connected in the optical fiber welding joint; the other end of the temperature optical fiber and the other end of the strain optical fiber are respectively connected with corresponding fiber cores in the transmission optical cable in an optical fiber leading-out joint; the optical fiber interfaces of the demodulator are respectively and externally connected with corresponding fiber cores of the transmission optical cable; the BOTDA monitoring technology and the DVS monitoring technology are fused, the defects that the optical fiber breakpoint cannot be positioned through the single BOTDA technology and the false alarm rate of the single DVS technology is high are overcome, and the operation state of the flexible composite pipe can be comprehensively monitored according to the two technologies. The monitoring optical fiber is implanted in the optical fiber composite pipeline, the optical fiber is located in the pipe wall, in-situ detection can be achieved, meanwhile, the pipe wall can protect the optical fiber, and in addition, construction is greatly simplified without laying the monitoring optical fiber on site.

Description

Technical Field

[0001] The invention belongs to the technical field of pipeline monitoring, and relates to a flexible composite pipe operation status monitoring system and an operation method. Background Art

[0002] Flexible composite pipes have strict requirements on operating pressure and temperature. Overpressure, pressure fluctuations, and overtemperature may accelerate pipeline aging and even cause pipeline failure. Flexible composite pipes have the advantages of flexible pipe body, large single continuous length, and few pipe joints, which simplifies construction and reduces the risk of failure; however, this also limits the locations on the pipeline where monitoring sensors can be installed; moreover, the use of single-point sensors requires the selection of a sensor for each parameter. The use of multiple sensors is not only inconvenient for integration, but also increases investment costs and installation workload. There are also problems such as data transmission, component power supply, and subsequent maintenance difficulties. In comparison, distributed fiber optic sensing technology has the advantages of long monitoring distance, the fiber itself is both a sensor and a transmission medium, continuous monitoring within the fiber length range, and no power supply required. It has been applied to oil and gas pipeline monitoring. However, in the field of oil and gas pipelines, the purpose of monitoring distributed fiber optic sensing technology is limited to leakage and external intrusion of metal pipelines, and only a single distributed fiber optic sensing technology (such as Rayleigh scattering to measure vibration, Raman scattering to measure temperature, Brillouin scattering to measure temperature / strain, etc.) is used; therefore, the existing technology has the disadvantages of high false alarm or missed alarm rate on the one hand, and on the other hand, it is still unable to monitor the service behavior characteristics of flexible composite pipes. Therefore, after the flexible composite pipe is put into service, its operating parameters only rely on the collection of operating temperature and pressure at the starting end, the end and a few limited points along the pipeline, and most of the pipe body positions are in the "monitoring blind area". Summary of the invention

[0003] The purpose of the present invention is to solve the problem in the prior art that the operating parameters of flexible composite pipes only rely on the collection of operating temperature and pressure at the starting end, the end end and a limited number of points along the pipeline, and most of the pipe body positions are in a "monitoring blind spot", and to provide a flexible composite pipe operating status monitoring system and operating method.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A flexible composite pipe operation status monitoring system includes: terminal equipment, signal lines, demodulators, transmission optical cables and optical fiber composite pipes;

[0006] The terminal equipment is used for human-computer interaction and displaying monitoring data, and the signal lines are respectively connected to the terminal equipment and the demodulator; the optical fiber composite pipeline includes an optical fiber fusion joint, an optical fiber composite tube and an optical fiber lead-out joint; the transmission optical cable includes a plurality of optical fiber cores; a temperature optical fiber and a strain optical fiber are arranged inside the optical fiber composite tube; one end of the temperature optical fiber and one end of the strain optical fiber are connected in the optical fiber fusion joint; the other end of the temperature optical fiber and the other end of the strain optical fiber are respectively connected to the corresponding optical cores in the transmission optical cable in the optical fiber lead-out joint;

[0007] The demodulator comprises a first optical circulator, a polarization scrambler and a second optical circulator; the demodulator has two optical fiber interfaces, which are respectively connected to corresponding optical cores of transmission optical cables; the demodulator respectively operates the BOTDA function and the DVS function; when the BOTDA function is operated, the interior of one optical fiber interface is connected to the polarization scrambler to output frequency-modulated continuous laser, and the interior of the other optical fiber interface is connected to the second optical circulator to output pulse laser and receive returned Brillouin optical signal for temperature and strain signal demodulation; when the DVS function is operated, the internal optical path of any one of the optical fiber interfaces is in a disconnected state, and the interior of the remaining optical fiber interface is connected to the first optical circulator to output pulse laser and receive returned Rayleigh optical signal for vibration signal demodulation; the connection and disconnection of the interior of the optical fiber interface are automatically controlled by the demodulator software according to a pre-set method.

[0008] A further improvement of the present invention is:

[0009] Furthermore, the optical fiber composite tube includes an inner lining layer, a reinforcement layer and an outer protective layer; the reinforcement layer is arranged on the outside of the inner lining layer to wrap the inner lining layer; the outer protective layer is arranged on the outside of the reinforcement layer to wrap the reinforcement layer; the temperature optical fiber and the strain optical fiber are spirally wound in the reinforcement layer according to the winding angle α; the temperature optical fiber and the strain optical fiber both use single-mode optical fiber.

[0010] Furthermore, the optical fiber fusion joint and the optical fiber lead-out joint are metal crimp joints; one end of the temperature optical fiber and one end of the strain optical fiber are connected in series through an optical fiber loss device; the other end of the temperature optical fiber and the other end of the strain optical fiber are connected to the corresponding optical core in the transmission optical cable through an optical fiber loss device respectively; the corresponding optical core of the transmission optical cable is externally connected to a demodulator to monitor the pipeline status.

[0011] Furthermore, the demodulator also includes a signal output unit, a microwave signal source, an electro-optic modulator, a variable optical attenuator, an avalanche photodetector and a signal acquisition unit;

[0012] When the demodulator runs the BOTDA function, the signal output unit outputs the first energy beam and the second energy beam; the first energy beam enters the electro-optical modulator to load the microwave signal generated by the microwave signal source for frequency modulation, then passes through the variable optical attenuator and the polarization scrambler in turn, and finally is output by the polarization scrambler and enters the temperature optical fiber and the strain optical fiber through the transmission optical cable; the second energy beam is split again to obtain the third energy beam and the fourth energy beam; the third energy beam enters the second optical circulator and is input into the temperature optical fiber and the strain optical fiber through the transmission optical cable; the continuous laser and the pulse laser inputted in opposite directions by the polarization scrambler and the second optical circulator meet in the temperature optical fiber and the strain optical fiber and generate a Brillouin optical signal, which contains the temperature and strain information of the temperature optical fiber and the strain optical fiber; the Brillouin optical signal is input into the avalanche photodetector through another port of the second optical circulator and converted into a first electrical signal; the first electrical signal enters the signal acquisition unit; the fourth energy beam is used by the DVS functional module.

[0013] Furthermore, the signal output unit includes a laser, a polarization beam splitter, an acousto-optic modulator, a pulsed erbium-doped fiber amplifier, and a non-polarization-maintaining beam splitter; the signal acquisition unit includes a data acquisition card and an industrial computer;

[0014] The laser outputs continuous laser light to the polarization beam splitter for energy splitting, which is divided into a first energy beam and a second energy beam; the second energy beam enters the acousto-optic modulator to form a nanosecond laser pulse, and then passes through a pulsed erbium-doped fiber amplifier and a non-polarization-maintaining beam splitter in sequence, and is again split at the non-polarization-maintaining beam splitter into a third energy beam and a fourth energy beam; the first electrical signal is transmitted to the industrial computer via the data acquisition card.

[0015] Furthermore, the demodulator includes a signal output unit, a pre-release erbium-doped fiber amplifier, a single-channel PIN photodetector and a signal acquisition unit; when the demodulator runs the DVS function, the fourth energy beam obtained based on the signal output unit is output through the first optical circulator and enters the temperature optical fiber and the strain optical fiber through the transmission optical cable to generate a Rayleigh optical signal, and the Rayleigh optical signal contains vibration information of the temperature optical fiber and the strain optical fiber; the Rayleigh optical signal passes through the first optical circulator, the pre-release erbium-doped fiber amplifier and the single-channel PIN photodetector in sequence; the single-channel PIN photodetector converts the Rayleigh optical signal into a second electrical signal, and the second electrical signal enters the signal acquisition unit, that is, the second electrical signal enters the industrial computer through the data acquisition card.

[0016] Furthermore, the strain optical fiber and the temperature optical fiber are laid together, and the signal of the temperature optical fiber corrects the strain optical fiber. Specifically, the temperature Brillouin frequency coefficient of the optical fiber is k1, and the strain Brillouin frequency coefficient of the optical fiber is k2; for a certain spatial position, the Brillouin frequency shift of the temperature optical fiber at that point is F1, and the temperature corresponding to the temperature optical fiber is k1*F1; the Brillouin frequency shift of the strain optical fiber at that point is F2, and the strain corresponding to the strain optical fiber is k2*(F2-F1); the temperature optical fiber is strain-desensitized by taking armor.

[0017] Furthermore, the energy of the first energy beam is 10% of the laser energy output by the laser; the energy of the second energy beam is 90% of the laser energy output by the laser; the energy of the third energy beam and the energy of the fourth energy beam are respectively 50% of the energy of the second energy beam.

[0018] A method for operating a flexible composite pipe operating status monitoring system, comprising:

[0019] Step 1: When the pipeline is laid and has not been backfilled, the temperature optical fiber or strain optical fiber is fused with the transmission optical cable, and then the corresponding fiber core of the transmission optical cable is connected to the optical time domain reflectometer. The characteristic attenuation signals generated by several optical fiber loss devices in the optical path are used to divide each section of the optical fiber, and the corresponding length value of the starting point of each section of the optical fiber is located; and then a digital mapping relationship of "optical fiber length-pipeline position" of the temperature optical fiber or strain optical fiber is established;

[0020] Step 2: Connect the fiber core corresponding to the transmission optical cable to the DVS fiber interface of the demodulator and run the DVS function; select a representative location along the optical fiber composite pipeline for tapping "stimulation", calibrate the digital mapping of this location based on the system's "response" signal, and mark the actual geographical routing information of this location;

[0021] Step 3, through calibration testing, converting the fiber temperature or fiber stress monitored at a certain position on the temperature fiber or strain fiber into the pipeline temperature and pipeline pressure generated by the transported fluid at the corresponding position of the pipeline, thereby realizing the monitoring of the temperature and pressure of the in-service pipeline;

[0022] Step 4: Determine whether there are breakpoints in the optical fiber, whether the pipeline is partially or completely overheated or overpressured, and whether there is abnormal vibration in the pipeline. If so, an alarm is issued.

[0023] Furthermore, a digital mapping relationship of "fiber length-pipeline position" of the temperature fiber or strain fiber is established, specifically:

[0024] Based on the length of the temperature optical fiber or strain optical fiber and the optical fiber winding angle, a mathematical relationship between the monitored pipeline length and the optical fiber length is established, as shown in the formula:

[0025] L 管道 =L光纤 cosα

[0026] Where α is the fiber winding angle; L 光纤 is the length of the temperature fiber or strain fiber;

[0027] The method of temperature calibration test is: connect the monitoring system, run the BOTDA function, circulate test liquids of different temperatures inside the optical fiber composite pipe under normal pressure conditions, and the minimum and maximum temperatures of the test liquid should include the expected monitoring temperature range; record the corresponding test liquid temperature T 测试 and temperature fiber optic acquisition T 光纤 , and establish the mathematical relationship between the two 测试 =f(T 光纤 ); Due to T 测试 That is T 管道 , so "T 管道 =f(T 光纤 )”, input this relationship into the system to complete the temperature calibration;

[0028] The method of pressure calibration test is: connect the monitoring system, run the BOTDA function, apply different hydrostatic pressures inside the optical fiber composite pipe under constant temperature conditions, and the minimum and maximum pressures of the test should include the expected monitoring pressure range; record the corresponding test pressure P 测试 and ε collected by strain fiber 光纤 , and establish the mathematical relationship between the two "P 测试 =f(ε 光纤 )”; Due to P 测试 That is P 管道 , so "P 管道 =f(ε 光纤 )”, input this relationship into the system to complete the pressure calibration.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention integrates BOTDA and DVS monitoring technologies, overcomes the shortcomings of single BOTDA technology that cannot locate fiber breakpoints and single DVS technology with high false alarm rate, and can also perform comprehensive monitoring of the operating status of the flexible composite pipe based on the two technologies. In addition, the present invention integrates the BOTDA and DVS functions through a demodulator, simplifies the equipment structure and reduces the equipment cost by sharing some components; the present invention implants monitoring optical fibers inside the optical fiber composite pipe. On the one hand, the optical fibers are located inside the pipe wall to achieve in-situ detection, and on the other hand, the pipe wall can protect the optical fibers. In addition, there is no need to lay monitoring optical fibers on site, which greatly simplifies the construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 It is a structural schematic diagram of the flexible composite pipe operation status monitoring system of the present invention;

[0033] Figure 2 Schematic diagram of the structure of optical fiber composite tube; Figure 2 (a) is a schematic cross-sectional view of the optical fiber composite tube; Figure 2 (b) is a schematic diagram of the winding angle of the temperature optical fiber and the strain optical fiber;

[0034] Figure 3 This is a schematic diagram of the connection and lead-out method of the optical fiber at the connector;

[0035] Figure 4 It is a schematic diagram of the demodulator and its working principle;

[0036] Figure 5 To establish mapping relationships and geographic routing process diagrams;

[0037] Figure 6 The following is the working flow diagram of the monitoring system.

[0038] Among them, 1--terminal equipment; 2--signal line; 3--demodulator; 4--transmission optical cable; 5--optical fiber composite pipe; 6--optical fiber fusion joint; 7--optical fiber composite pipe; 8--optical fiber lead-out joint; 9--optical fiber loss device; 3-1--laser; 3-2--polarization beam splitter; 3-3--acoustic-optic modulator; 3-4--pulsed erbium-doped fiber amplifier; 3-5--non-polarization-maintaining beam splitter; 3-6--first optical circulator; 3-7--microwave signal source; 3-8--microwave signal source; 3-9--microwave signal source; 3-10--laser; 3-11--polarization beam splitter; 3-12--acoustic-optic modulator; 3-13--acoustic-optic modulator; 3-14--pulsed erbium-doped fiber amplifier; 3-15--non-polarization-maintaining beam splitter; 3-16--first optical circulator; 3-17--microwave signal source; 3-18--microwave signal source; 3-19--microwave signal source; 3-20--polarization beam splitter; 3-21--acoustic-optic modulator; 3-22--acoustic-optic modulator; 3-23--acoustic-optic modulator; 3-24--pulsed erbium-doped fiber amplifier; 3-25--non-polarization-maintaining beam splitter; 3-26--first optical circulator; 3-27--microwave signal source; 3-28--microwave signal source; 3-29--microwave signal source; 3-30--microwave signal source; 3-31- -8--Electro-optic modulator; 3-9--Variable optical attenuator; 3-10--Polarization scrambler; 3-11--Second optical circulator; 3-12--Pre-release erbium-doped fiber amplifier; 3-13--Industrial computer; 3-14--Data acquisition card; 3-15--Avalanche photodetector; 3-16--Single-channel PIN photodetector; 7-1--Inner lining layer; 7-2--Enhancement layer; 7-3--Outer protective layer; 7-4--Temperature optical fiber; 7-5--Strain optical fiber. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0040] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0042] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0043] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0044] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0046] See also Figure 1 , the present invention discloses a flexible composite pipe operation status monitoring system, comprising: a terminal device 1, a signal line 2, a demodulator 3, a transmission optical cable 4 and an optical fiber composite pipe 5;

[0047] The terminal device 1 is used for human-computer interaction and displaying monitoring data, such as a display, keyboard, mouse, etc. The signal line 2 connects the terminal device 1 and the demodulator 3 respectively; if wireless transmission technology is adopted, the signal line 2 can be omitted. The optical fiber composite pipe 5 includes an optical fiber fusion joint 6, an optical fiber composite tube 7 and an optical fiber lead-out joint 8; the transmission optical cable 4 includes a plurality of fiber cores; a temperature optical fiber 7-4 and a strain optical fiber 7-5 are arranged inside the optical fiber composite tube 7; one end of the temperature optical fiber 7-4 and one end of the strain optical fiber 7-5 are connected in the optical fiber fusion joint 6; the other end of the temperature optical fiber 7-4 and the other end of the strain optical fiber 7-5 are respectively connected to the corresponding fiber cores in the transmission optical cable 4 in the optical fiber lead-out joint 8; the transmission optical cable 4 is a single-mode optical fiber, and one multi-core optical cable can be used, or multiple single-core optical cables can be used.

[0048] The demodulator 3 includes a laser 3-1, a polarization beam splitter 3-2, an acousto-optic modulator 3-3, a pulsed erbium-doped fiber amplifier 3-4, a non-polarization-maintaining beam splitter 3-5, a first optical circulator 3-6, a microwave signal source 3-7, an electro-optic modulator 3-8, a variable optical attenuator 3-9, a polarization scrambler 3-10, a second optical circulator 3-11, a pre-release erbium-doped fiber amplifier 3-12, an industrial computer 3-13, a data acquisition card 3-14, an avalanche photodetector 3-15, and a single-channel PIN photodetector 3-16; the demodulator 3 has two optical fiber interfaces, which are respectively connected to the corresponding fiber cores of the transmission optical cable 4; the demodulator 3 can respectively run the BOTDA function and DVS functions; when the BOTDA function is running, the interior of one optical fiber interface is connected to the polarization scrambler 3-10 to output frequency-modulated continuous laser, and the interior of the other optical fiber interface is connected to the second optical circulator 3-11 to output pulsed laser and receive the returned Brillouin light signal for temperature and strain signal demodulation; when the DVS function is running, the internal optical path of any one of the optical fiber interfaces is in a disconnected state, and the interior of the remaining other optical fiber interface is connected to the first optical circulator 3-6 to output pulsed laser and receive the returned Rayleigh light signal for vibration signal demodulation; the connection and disconnection of the internal optical fiber interface are automatically controlled by the demodulator software in a pre-set manner.

[0049] See also Figure 2 (a) and Figure 2(b), the optical fiber composite tube 7 includes an inner lining layer 7-1, a reinforcement layer 7-2 and an outer protective layer 7-3; the tube structure of the optical fiber composite tube 7 is in accordance with the SY / T 6662.2 standard. The reinforcement layer 7-2 is arranged on the outer side of the inner lining layer 7-1 to wrap the inner lining layer 7-1; the outer protective layer 7-3 is arranged on the outer side of the reinforcement layer 7-2 to wrap the reinforcement layer 7-2; the temperature optical fiber 7-4 and the strain optical fiber 7-5 are spirally wound in the reinforcement layer 7-2 according to the winding angle α; the temperature optical fiber 7-4 and the strain optical fiber 7-5 are both single-mode optical fibers.

[0050] The optical fiber fusion joint 6 and the optical fiber lead-out joint 8 are metal crimp joints, which meet the basic requirements of SY / T 6662.2 on pipeline connection and sealing, and can further realize the lead-out, fusion and protection of the temperature optical fiber 7-4 and the strain optical fiber 7-5 in the optical fiber composite tube 7. Figure 3 , one end of the temperature optical fiber 7-4 and one end of the strain optical fiber 7-5 are connected in series through an optical fiber loss device 9; the other end of the temperature optical fiber 7-4 and the other end of the strain optical fiber 7-5 are connected to the corresponding fiber core in the transmission optical cable 4 through an optical fiber loss device 9 respectively; the function of the optical fiber loss device 9 is to generate a slight power loss that can be detected by the instrument in order to divide the starting point of each section of the optical fiber on the optical path. The corresponding fiber core of the transmission optical cable 4 is externally connected to the demodulator 3 to perform pipeline status monitoring. The transmission optical cable 4 also serves as a redundant optical fiber in the optical path to prevent the optical signal from being interfered by Fresnel reflection at the end of the temperature optical fiber 7-4 or the strain optical fiber 7-5.

[0051] See also Figure 4When the demodulator 3 runs the BOTDA function, the laser 3-1 outputs a continuous laser to the polarization beam splitter 3-2 for energy splitting, and is divided into a first energy beam and a second energy beam; the first energy beam enters the electro-optic modulator 3-8 to load the microwave signal generated by the microwave signal source 3-7 for frequency modulation, and then passes through the variable optical attenuator 3-9 and the polarization scrambler 3-10 in turn, and is finally output by the polarization scrambler 3-10 through the transmission cable 4 to enter the temperature optical fiber 7-4 and the strain optical fiber 7-5; the second energy beam enters the acousto-optic modulator 3-3 to form a nanosecond laser pulse, and then passes through the pulse erbium-doped fiber amplifier 3-4 and the non-polarization-maintaining beam splitter 3-5 in turn, and is again split at the non-polarization-maintaining beam splitter 3-5 into the first energy beam and the second energy beam. Three energy beams and a fourth energy beam; the third energy beam enters the second optical circulator 3-11 and is input into the temperature optical fiber 7-4 and the strain optical fiber 7-5 via the transmission optical cable 4; the continuous laser and the pulse laser input in opposite directions by the polarization scrambler 3-10 and the second optical circulator 3-11 meet in the temperature optical fiber 7-4 and the strain optical fiber 7-5 and generate a Brillouin optical signal, which contains the temperature and strain information of the temperature optical fiber 7-4 and the strain optical fiber 7-5; the Brillouin optical signal is input into the avalanche photodetector 7-15 via another port of the second optical circulator 7-11 and converted into a first electrical signal; the first electrical signal is transmitted to the industrial computer 7-13 via the data acquisition card 7-14; the fourth energy beam is used by the DVS function.

[0052] When the demodulator 3 runs the DVS function, the operation mode of the laser 3-1, the polarization beam splitter 3-2, the acousto-optic modulator 3-3, the pulsed erbium-doped fiber amplifier 3-4, and the non-polarization-maintaining beam splitter 3-5 is the same as when the BOTDA function is run. The fourth energy beam formed is output from the first optical circulator 3-6 and enters the temperature optical fiber 7-4 and the strain optical fiber 7-5 through the transmission optical cable 4 and generates a Rayleigh optical signal. The Rayleigh optical signal contains the vibration information of the temperature optical fiber 7-4 and the strain optical fiber 7-5; the Rayleigh optical signal passes through the first optical circulator 3-6, the pre-release erbium-doped fiber amplifier 3-12 and the single-channel PIN photodetector 3-16 in sequence; the single-channel PIN photodetector 3-16 converts the Rayleigh optical signal into a second electrical signal, and the second electrical signal is transmitted to the industrial computer 3-13 through the data acquisition card 3-14.

[0053] The laser 3-1 is a 1550nm narrow linewidth laser; the polarization beam splitter 3-2 is a 90 / 10 polarization beam splitter; the non-polarization maintaining beam splitter 3-5 is a 50 / 50 non-polarization maintaining beam splitter; and the microwave signal source 3-7 is an 8GHz to 12GHz microwave signal source.

[0054] The temperature and strain signal sensing principle of this system is based on the Brillouin time domain analysis (BOTDA) technology of the Brillouin scattering effect of laser. Since both temperature and strain will cause the Brillouin optical signal frequency shift, it is necessary to separate the temperature and strain signals: the temperature optical fiber 7-4 is desensitized to strain by taking armor; the strain optical fiber 7-5 is sensitive to both strain and temperature; the strain optical fiber 7-5 is arranged along with the temperature optical fiber 7-4, and the signal of the accompanying temperature optical fiber 7-4 is used to correct the strain optical fiber 7-5. Specifically: the temperature Brillouin frequency coefficient of the optical fiber is k1, and the strain Brillouin frequency coefficient of the optical fiber is k2; for a certain spatial position, the Brillouin frequency shift of the temperature optical fiber 7-4 at this point is F1, and the temperature corresponding to the temperature optical fiber 7-4 is k1*F1; the Brillouin frequency shift of the strain optical fiber 7-5 at this point is F2, and the strain corresponding to the strain optical fiber 7-5 is k2*(F2-F1).

[0055] The vibration signal sensing principle in this system is the phase-sensitive optical time domain reflectometry (Φ-OTDR) technology based on the Rayleigh scattering effect of laser. When a certain point on the temperature optical fiber 7-4 or the strain optical fiber 7-5 is disturbed by external vibration, the system will detect the signal change at the disturbed position.

[0056] The energy of the first energy beam is 10% of the laser energy output by laser 3-1; the energy of the second energy beam is 90% of the laser energy output by laser 3-1; the energy of the third energy beam and the energy of the fourth energy beam are respectively 50% of the energy of the second energy beam.

[0057] The present invention discloses an operation method of a flexible composite pipe operation status monitoring system, comprising:

[0058] See also Figure 5 , Step 1: When the pipeline is laid and has not been backfilled, the temperature optical fiber 7-4 or the strain optical fiber 7-5 is fused with the transmission optical cable 4, and then the corresponding core of the transmission optical cable 4 is connected to the optical time domain reflectometer, and the characteristic attenuation signal generated by the optical fiber loss device 9 in the optical path is used to divide each section of the optical fiber, and the corresponding length value of the starting point of each section of the optical fiber is located; and then a digital mapping relationship of "optical fiber length-pipeline position" of the temperature optical fiber 7-4 or the strain optical fiber 7-5 is established;

[0059] Step 2: Connect the fiber core corresponding to the transmission optical cable 4 to the DVS fiber interface of the demodulator 3 and run the DVS function; select a representative position along the optical fiber composite pipeline 5 for tapping "stimulation", calibrate the digital mapping of this position according to the "response" signal of the system, and mark the actual geographical routing information of this position;

[0060] Step 3, run the BOTDA function, and convert the fiber temperature or fiber stress monitored at a certain position on the temperature fiber 7-4 or the strain fiber 7-5 into the pipeline temperature and pipeline pressure caused by the transported fluid at the corresponding position of the pipeline through calibration test, so as to realize the monitoring of the temperature and pressure of the in-service pipeline;

[0061] Step 4: Determine whether there are breakpoints in the optical fiber, whether the pipeline is partially or completely overheated or overpressured, and whether there is abnormal vibration in the pipeline. If so, an alarm is issued.

[0062] A digital mapping relationship of "fiber length-pipeline position" of the temperature optical fiber 7-4 or the strain optical fiber 7-5 is established, specifically:

[0063] Based on the length of the temperature optical fiber 7-4 or the strain optical fiber 7-5 and the optical fiber winding angle, a mathematical relationship between the monitored pipeline length and the optical fiber length is established, as shown in formula (1):

[0064] L 管道 =L 光纤 cosα (1)

[0065] Where α is the fiber winding angle; L 光纤 is the length of the temperature optical fiber 7-4 or the strain optical fiber 7-5;

[0066] The method of temperature calibration test is: connect the monitoring system, run the BOTDA function, circulate test liquids of different temperatures inside the optical fiber composite pipe 5 under normal pressure conditions, and the minimum and maximum temperatures of the test liquids should include the expected monitoring temperature range; record the corresponding test liquid temperature T 测试 and temperature optical fiber 7-4 collects T 光纤 , and establish the mathematical relationship between the two 测试 =f(T 光纤 ); Due to T 测试 That is T 管道 , so "T 管道 =f(T 光纤 )”, input this relationship into the system to complete the temperature calibration;

[0067] The method of pressure calibration test is: connect the monitoring system, run the BOTDA function, apply different static pressures inside the optical fiber composite pipe 5 under constant temperature conditions, and the minimum and maximum pressures of the test should include the expected monitoring pressure range; record the corresponding test pressure P 测试 and ε collected by strain fiber 7-5 光纤 , and establish the mathematical relationship between the two "P 测试 =f(ε 光纤 )”; Due to P 测试 That is P 管道 , so "P 管道=f(ε 光纤 )”, input this relationship into the system to complete the pressure calibration.

[0068] Embodiment: This system uses the collaborative operation of BOTDA function and DVS function. The workflow is as follows: Figure 6 As shown: 1) The system runs the BOTDA function by default to monitor the T 管道 and P 管道 2) When the pipeline T is found 管道 and P 管道 When the preset threshold is exceeded, the failure and failure type are determined based on the specific situation and the vibration signal of the DVS function. If failure is determined, an alarm is activated. 3) When the BOTDA function cannot operate normally, the DVS function is switched to monitor whether the optical fiber is intact, and the fault location and type are determined based on the actual situation, and an alarm is activated.

[0069] The present invention will be further described below in conjunction with specific embodiments.

[0070] 1) Monitoring system composition

[0071] 1 300m long optical fiber composite pipe, inner diameter 50mm, nominal pressure 16MPa, maximum service temperature 65℃. The inner lining layer is heat-resistant polyethylene, the reinforcement layer is continuous polyester fiber, the outer protective layer is polyethylene, the temperature optical fiber is a single-core single-mode optical fiber with a stainless steel loose tube, and the strain optical fiber is a single-core single-mode optical fiber with a thermoplastic elastomer tight tube. The winding angle of the two types of optical fibers is the same α=60°. The optical fiber fusion joint and the optical fiber lead-out joint are made of 316 stainless steel. Three 0.5dB optical fiber attenuators are used. Using the demodulator described in the present invention, such as Figure 4 As shown. The transmission optical cable uses a 2km long stainless steel spiral armored 4-core single-mode outdoor optical cable, of which 2 fiber cores are used to connect the optical path and the other 2 fiber cores are spare. The optical fiber interface of the demodulator and the transmission optical cable are connected through FC / APC connectors. The terminal device is a combination of a monitor, keyboard and mouse.

[0072] 2) Establish the mapping relationship between “fiber length and pipeline routing”

[0073] Use L 管道 =L 光纤 ·cos60°=0.5L 光纤 Establish digital mapping. From one end of the pipeline, every 50m is used as a tapping test point, a total of 7 points, calibrate the digital mapping, and average the distance between every two test points.

[0074] 3) Calibration test

[0075] A 5m long optical fiber composite pipe was used for calibration in a constant temperature water tank and a hydrostatic pressure tester in the laboratory. Calibration was performed based on the intended service conditions of 50℃ and 5MPa. When calibrating the temperature, the calibration points were 30℃, 50℃, and 70℃; when calibrating the pressure, the calibration points were 1MPa, 5MPa, and 10MPa; for any two adjacent calibration points, a linear equation was established based on the two sets of data corresponding to the two calibration points. This equation is the calibration equation for the temperature or pressure range (including these two points) during actual monitoring.

[0076] 4) Alarm point setting

[0077] The over-temperature alarm threshold is 55°C; the over-pressure alarm threshold is 6MPa; the leakage judgment vibration signal is within the range of ±5m of the local over-temperature (or over-pressure) point.

[0078] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A flexible composite pipe operation status monitoring system, characterized in that: include: Terminal equipment (1), signal line (2), demodulator (3), transmission optical cable (4) and optical fiber composite pipe (5); The terminal device (1) is used for human-computer interaction and displaying monitoring data, and the signal line (2) is respectively connected to the terminal device (1) and the demodulator (3); the optical fiber composite pipeline (5) comprises an optical fiber fusion joint (6), an optical fiber composite tube (7) and an optical fiber lead-out joint (8); the transmission optical cable (4) comprises a plurality of optical fiber cores; a temperature optical fiber (7-4) and a strain optical fiber (7-5) are arranged inside the optical fiber composite tube (7); one end of the temperature optical fiber (7-4) and one end of the strain optical fiber (7-5) are connected in the optical fiber fusion joint (6); the other end of the temperature optical fiber (7-4) and the other end of the strain optical fiber (7-5) are respectively connected to the corresponding optical fiber cores in the transmission optical cable (4) in the optical fiber lead-out joint (8); The demodulator (3) comprises a first optical circulator (3-6), a polarization scrambler (3-10) and a second optical circulator (3-11); the demodulator (3) has two optical fiber interfaces, the optical fiber interfaces are respectively connected to the corresponding optical cores of the transmission optical cable (4); the demodulator (3) respectively operates the BOTDA function and the DVS function; when the BOTDA function is operated, the interior of one optical fiber interface is connected to the polarization scrambler (3-10) to output frequency-modulated continuous laser light, and the interior of the other optical fiber interface is connected to the second optical circulator (3-11) to output pulse laser light and receive the returned Brillouin optical signal for temperature and strain signal demodulation; when the DVS function is operated, the internal optical path of any one of the optical fiber interfaces is in a disconnected state, and the interior of the remaining optical fiber interface is connected to the first optical circulator (3-6) to output pulse laser light and receive the returned Rayleigh optical signal for vibration signal demodulation; the connection and disconnection of the interior of the optical fiber interface are automatically controlled by the demodulator (1) software according to a pre-set method.

2. The flexible composite pipe operation status monitoring system according to claim 1 is characterized in that: The optical fiber composite tube (7) comprises an inner lining layer (7-1), a reinforcement layer (7-2) and an outer protective layer (7-3); the reinforcement layer (7-2) is arranged on the outer side of the inner lining layer (7-1) to wrap the inner lining layer (7-1); the outer protective layer (7-3) is arranged on the outer side of the reinforcement layer (7-2) to wrap the reinforcement layer (7-2); the temperature optical fiber (7-4) and the strain optical fiber (7-5) are spirally wound in the reinforcement layer (7-2) according to a winding angle α; the temperature optical fiber (7-4) and the strain optical fiber (7-5) are both single-mode optical fibers.

3. The flexible composite pipe operation status monitoring system according to claim 2 is characterized in that: The optical fiber fusion joint (6) and the optical fiber lead-out joint (8) are metal crimp joints; one end of the temperature optical fiber (7-4) and one end of the strain optical fiber (7-5) are connected in series via an optical fiber loss device (9); the other end of the temperature optical fiber (7-4) and the other end of the strain optical fiber (7-5) are connected to the corresponding fiber core in the transmission optical cable (4) via an optical fiber loss device (9) respectively; and the corresponding fiber core of the transmission optical cable (4) is externally connected to a demodulator (3) to monitor the pipeline status.

4. The flexible composite pipe operation status monitoring system according to claim 3 is characterized in that: The demodulator (3) also includes a signal output unit, a microwave signal source (3-7), an electro-optic modulator (3-8), a variable optical attenuator (3-9), an avalanche photodetector (3-15) and a signal acquisition unit; When the demodulator (3) operates the BOTDA function, the signal output unit outputs a first energy beam and a second energy beam; the first energy beam enters the electro-optical modulator (3-8) to load the microwave signal generated by the microwave signal source (3-7) for frequency modulation, and then passes through the variable optical attenuator (3-9) and the polarization scrambler (3-10) in sequence, and finally is output by the polarization scrambler (3-10) and enters the temperature optical fiber (7-4) and the strain optical fiber (7-5) via the transmission optical cable (4); the second energy beam is split again to obtain a third energy beam and a fourth energy beam; the third energy beam enters the second optical circulator (3-11) and then passes through the transmission optical cable (4 ) input the temperature optical fiber (7-4) and the strain optical fiber (7-5); the continuous laser and the pulse laser inputted in opposite directions by the polarization scrambler (3-10) and the second optical circulator (3-11) meet in the temperature optical fiber (7-4) and the strain optical fiber (7-5) and generate a Brillouin optical signal, wherein the Brillouin optical signal contains the temperature and strain information of the temperature optical fiber (7-4) and the strain optical fiber (7-5); the Brillouin optical signal is input into the avalanche photodetector (3-15) through another port of the second optical circulator (3-11) and converted into a first electrical signal; the first electrical signal enters the signal acquisition unit; the fourth energy beam is used by the DVS functional module.

5. The flexible composite pipe operation status monitoring system according to claim 4, characterized in that: The signal output unit comprises a laser (3-1), a polarization beam splitter (3-2), an acousto-optic modulator (3-3), a pulsed erbium-doped fiber amplifier (3-4), and a non-polarization-maintaining beam splitter (3-5); the signal acquisition unit comprises a data acquisition card (3-14) and an industrial computer (3-13); The laser (3-1) outputs continuous laser light to a polarization beam splitter (3-2) for energy splitting, and the energy beam is split into a first energy beam and a second energy beam; the second energy beam enters an acousto-optic modulator (3-3) to form a nanosecond laser pulse, and then passes through a pulsed erbium-doped fiber amplifier (3-4) and a non-polarization-maintaining beam splitter (3-5) in sequence, and is again split into a third energy beam and a fourth energy beam at the non-polarization-maintaining beam splitter (3-5); the first electrical signal is transmitted to an industrial computer (3-13) via a data acquisition card (3-14).

6. The flexible composite pipe operation status monitoring system according to claim 5, characterized in that: The demodulator (3) comprises a signal output unit, a pre-release erbium-doped fiber amplifier (3-12), a single-channel PIN photodetector (3-16) and a signal acquisition unit; when the demodulator (3) runs a DVS function, a fourth energy beam obtained based on the signal output unit is output via a first optical circulator (3-6) and enters a temperature optical fiber (7-4) and a strain optical fiber (7-5) via a transmission optical cable (4) to generate a Rayleigh optical signal, wherein the Rayleigh optical signal contains vibration information of the temperature optical fiber (7-4) and the strain optical fiber (7-5); the Rayleigh optical signal passes through the first optical circulator (3-6), the pre-release erbium-doped fiber amplifier (3-12) and the single-channel PIN photodetector (3-16) in sequence; the single-channel PIN photodetector (3-16) converts the Rayleigh optical signal into a second electrical signal, and the second electrical signal enters the signal acquisition unit, that is, the second electrical signal enters the data acquisition card (3-14) and is transmitted to the industrial control computer (3-13).

7. The flexible composite pipe operation status monitoring system according to claim 6, characterized in that: The strain optical fiber (7-5) and the temperature optical fiber (7-4) are arranged in parallel, and the signal of the temperature optical fiber (7-4) corrects the strain optical fiber (7-5), specifically: the temperature Brillouin frequency coefficient of the optical fiber is k1, and the strain Brillouin frequency coefficient of the optical fiber is k2; for a certain spatial position, the Brillouin frequency shift of the temperature optical fiber (7-4) at this point is F1, and the temperature corresponding to the temperature optical fiber (7-4) is k1*F1; the Brillouin frequency shift of the strain optical fiber (7-5) at this point is F2, and the strain corresponding to the strain optical fiber (7-5) is k2*(F2-F1); the temperature optical fiber (7-4) is subjected to strain desensitization treatment by adopting armor.

8. The flexible composite pipe operation status monitoring system according to claim 7, characterized in that: The energy of the first energy beam is 10% of the laser energy output by the laser (3-1); the energy of the second energy beam is 90% of the laser energy output by the laser (3-1); the energy of the third energy beam and the energy of the fourth energy beam are respectively 50% of the energy of the second energy beam.

9. An operating method of the flexible composite pipe operating status monitoring system according to claim 8, characterized in that: include: Step 1: When the pipeline is laid and has not yet been backfilled, the temperature optical fiber (7-4) or the strain optical fiber (7-5) is fused with the transmission optical cable (4), and then the corresponding fiber core of the transmission optical cable (4) is connected to the optical time domain reflectometer, and the characteristic attenuation signals generated by a plurality of optical fiber loss devices (9) in the optical path are used to divide each section of the optical fiber, and the corresponding length value of the starting point of each section of the optical fiber is located; and then a digital mapping relationship of "optical fiber length-pipeline position" of the temperature optical fiber (7-4) or the strain optical fiber (7-5) is established; Step 2, connect the fiber core corresponding to the transmission optical cable (4) to the DVS fiber interface of the demodulator (3) and run the DVS function; select a representative position along the optical fiber composite pipeline (5) to perform knocking "stimulation", calibrate the digital mapping of this position according to the "response" signal of the system, and mark the actual geographical routing information of this position; Step 3, converting the optical fiber temperature or optical fiber stress monitored at a certain position on the temperature optical fiber (7-4) or the strain optical fiber (7-5) into the pipeline temperature and pipeline pressure generated by the transported fluid at the corresponding position of the pipeline through calibration testing, so as to realize the monitoring of the temperature and pressure of the in-service pipeline; Step 4: Determine whether there are breakpoints in the optical fiber, whether the pipeline is partially or completely overheated or overpressured, and whether there is abnormal vibration in the pipeline. If so, an alarm is issued.

10. The operating method of the flexible composite pipe operating status monitoring system according to claim 9, characterized in that: The digital mapping relationship of "fiber length-pipeline position" of the temperature optical fiber (7-4) or the strain optical fiber (7-5) is established as follows: Based on the length of the temperature optical fiber (7-4) or the strain optical fiber (7-5) and the optical fiber winding angle, a mathematical relationship between the monitored pipeline length and the optical fiber length is established, as shown in formula (1): L 管道 =L 光纤 cosα (1) Where α is the fiber winding angle; L 光纤 is the length of the temperature optical fiber (7-4) or the strain optical fiber (7-5); The temperature calibration test method is: connect the monitoring system, run the BOTDA function, circulate test liquids of different temperatures inside the optical fiber composite pipe (5) under normal pressure conditions, and the lowest and highest temperatures of the test liquids should include the expected monitoring temperature range; record the corresponding test liquid temperature T 测试 and temperature optical fiber (7-4) collected T 光纤 , and establish the mathematical relationship between the two 测试 =f(T 光纤 ); Due to T 测试 That is T 管道 , so "T 管道 =f(T 光纤 )”, input this relationship into the system to complete the temperature calibration; The method of pressure calibration test is: connect the monitoring system, run the BOTDA function, apply different static hydraulic pressures inside the optical fiber composite pipe (5) under constant temperature conditions, and the minimum and maximum pressures of the test should include the expected monitoring pressure range; record the corresponding test pressure P 测试 and ε collected by strain optical fiber (7-5) 光纤 , and establish the mathematical relationship between the two 测试 =f(ε 光纤 )”; Due to P 测试 That is P 管道 , so "P 管道 =f(ε 光纤 )”, input this relationship into the system to complete the pressure calibration.

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