A non-invasive measurement sensor, measurement method and installation method for pipeline pressure monitoring

Abstract

The present invention discloses a non-invasive measuring sensor, measuring method and installation method for pipeline pressure monitoring, wherein the non-invasive measuring sensor comprises a fixed caliper and an elastic element, wherein the fixed caliper comprises a first caliper and a second caliper, wherein the elastic element comprises an upper elastic member and a lower elastic member, wherein the upper and lower ends of the first caliper are connected to the upper and lower ends of the second caliper through the upper elastic member and the lower elastic member, wherein the first caliper and the second caliper are combined to form a through groove for clamping the pipeline, wherein the upper elastic member at the upper end of the first caliper and the second caliper is provided with a sensing unit, wherein the sensing unit comprises two substrates and a long gauge length double grating structure, wherein the long gauge length double grating structure is located between the two substrates and fixed on the two substrates. The installation and fixing of the non-invasive measuring sensor provided by the present invention to the pipeline does not need to destroy the integrity of the pipeline structure, and the non-invasive measuring sensor can adapt to harsh environments such as strong electromagnetic interference and strong chemical corrosion, and the wiring and installation of its internal structure are simple.

Description

Technical Field

[0001] The present invention relates to the technical field of pipeline monitoring, and in particular to a non-invasive measuring sensor, a measuring method and an installation method for pipeline pressure monitoring. Background Art

[0002] Pipelines are important tools for transporting fossil fuels such as oil and natural gas, and they play an important role in the development of the national economy. Therefore, pipeline leakage monitoring is an important topic in the field of pipeline operation status monitoring, which is of great significance to the safe and stable service of pipelines. The location and degree of pipeline leakage can be reflected from the pipeline pressure measurement data. Generally, the degree of pipeline leakage is measured by pressure sensors. At present, the pressure sensor structures for pipeline leakage monitoring mainly include resistive pressure sensors, capacitive pressure sensors, and fiber grating sensors. The existing pressure sensors have the following deficiencies in the process of measuring pipelines:

[0003] 1) Existing resistive or capacitive pressure sensors are usually invasive and require opening holes in the pipeline for installation, which damages the integrity and strength of the pipeline.

[0004] 2) Existing electrical pressure sensors usually have complex wiring, and their measurement errors in strong electromagnetic interference and strong corrosion environments make it difficult to ensure measurement accuracy;

[0005] 3) Existing fiber Bragg grating pressure sensors have problems of temperature coupling, low sensitivity and complex structure. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art. The present invention provides a non-invasive measurement sensor, measurement method and installation method that can adapt to harsh environments such as strong electromagnetic interference and strong chemical corrosion, and its installation does not damage the pipeline, the wiring method is simple, the measurement data is not affected by the ambient temperature, it is easy to install, and the sensitivity is higher than that of the existing fiber grating pressure sensor.

[0007] In order to solve the above technical problems, on the one hand, the present invention provides a non-invasive measurement sensor for pipeline pressure monitoring, the non-invasive measurement sensor comprising a fixed caliper and an elastic element, the fixed caliper comprising a first caliper and a second caliper, the first caliper and the second caliper are symmetrically spaced, the elastic element comprises an upper elastic member and a lower elastic member, the upper elastic member and the lower elastic member are symmetrically distributed in the upper and lower directions, the upper and lower ends of the first caliper are connected to the upper and lower ends of the second caliper through the upper elastic member and the lower elastic member, the first caliper and the second caliper are surrounded to form a through groove for clamping the pipeline, the upper elastic member at the upper ends of the first caliper and the second caliper is installed with a sensing unit, the first caliper and the second caliper are located at the left and right ends of the sensing unit, the sensing unit comprises two substrates and a long gauge double grating structure, the two substrates are symmetrically spaced at the two ends of the upper elastic member, the long gauge double grating structure is located between the two substrates and fixed on the two substrates.

[0008] Furthermore, the long gauge dual grating structure comprises a first long gauge fiber grating and a second long gauge fiber grating, and the first long gauge fiber grating and the second long gauge fiber grating are spaced apart and distributed in parallel between two substrates.

[0009] Furthermore, bonding parts are provided on the surfaces of the two substrates, and both ends of the first long gauge fiber Bragg grating and the second long gauge fiber Bragg grating are fixed at the bonding parts of the two substrates to form a sensing unit.

[0010] Furthermore, the first long gauge fiber Bragg grating and the second long gauge fiber Bragg grating are applied to the bonding parts of the two substrates with adhesive to fix the first long gauge fiber Bragg grating and the second long gauge fiber Bragg grating to the two substrates.

[0011] Furthermore, the non-invasive measurement sensor includes four screws, the upper and lower ends of the first caliper are provided with a first upper fixing hole and a first lower fixing hole matching with the screws, the upper and lower ends of the second caliper are provided with a second upper fixing hole and a second lower fixing hole matching with the screws, and the four screws are respectively located at the first upper fixing hole and the first lower fixing hole at the upper and lower ends of the first caliper, and the second upper fixing hole and the second lower fixing hole at the upper and lower ends of the second caliper.

[0012] Furthermore, the two ends of the upper elastic member are respectively provided with a first upper elastic fixing hole and a second upper elastic fixing hole that cooperate with the screws, the two ends of the lower elastic member are respectively provided with a first lower elastic fixing hole and a second lower elastic fixing hole that cooperate with the screws, and the two substrates are both provided with a first substrate mounting hole and a second substrate mounting hole that cooperate with the screws. The two screws pass through the first substrate mounting holes, the second substrate mounting holes, the first upper elastic fixing holes, the second upper elastic fixing holes at both ends of the upper elastic member, the first upper fixing hole at the upper end of the first caliper, and the second upper fixing hole at the upper end of the second caliper from top to bottom to fix the two substrates and the upper elastic member to the upper ends of the first caliper and the second caliper; the other two screws pass through the first lower elastic fixing holes, the second lower elastic fixing holes, the first lower fixing holes at the lower end of the first caliper, and the second lower fixing holes at the lower end of the second caliper from bottom to top to fix the lower elastic member to the lower ends of the first caliper and the second caliper.

[0013] Furthermore, the upper elastic member and the lower elastic member are in a serpentine elastic structure.

[0014] On the other hand, the present invention provides a measurement method of a non-invasive measurement sensor for pipeline pressure monitoring, the measurement method comprising the following process:

[0015] Step S1) Pipeline pressure measurement: First, measure the inner diameter pressure change of the pipeline, apply pressure p to the pipeline through the pressure chamber to make the pipeline expand evenly under the internal pressure p, and calculate the change in the inner diameter of the pipeline. The inner diameter change is:

[0016] Where d is the inner diameter of the pipe; υ and E are the Poisson's ratio and elastic modulus of the pipe material, respectively; δ is the wall thickness of the pipe;

[0017] Step S2) Measurement of the long gauge length double grating structure: An equation relationship is established by the change in the internal diameter of the pipeline and the central wavelength offset measured by stretching the long gauge length double grating structure. When the inner diameter of the pipeline changes, the sensing unit, under the action of the elastic element, the left and right first calipers and the second caliper of the sensing unit can move with the deformation of the pipeline. According to the displacement coordination relationship, the relative displacement ΔL of the first caliper and the second caliper and the change in the inner diameter of the pipeline Δd have the following equation relationship: Δd=ΔL;

[0018] Under the relative movement of the first caliper and the second caliper, the first long-gauge fiber Bragg grating and the second long-gauge fiber Bragg grating of the long-gauge dual-gauge structure will be stretched, and the central wavelength offsets Δλ1 and Δλ2 of the first long-gauge fiber Bragg grating and the second long-gauge fiber Bragg grating can be expressed as:

[0019]

[0020] In the expression, λ1 and λ2 are the initial center wavelengths of the first long gauge fiber Bragg grating and the second long gauge fiber Bragg grating, respectively, and |K|≠0, L1 and L2 are the initial lengths of the first long gauge fiber Bragg grating and the second long gauge fiber Bragg grating, respectively, and p e is the elastic-optic coefficient of the fiber Bragg grating, α is the thermal expansion coefficient of the fiber Bragg grating, ξ is the thermo-optic coefficient of the fiber Bragg grating, and ΔT is the change in ambient temperature;

[0021] Combining the above expressions (1) and (2), the functional relationship between the internal pressure p of the pipeline and the central wavelength offset of the first long gauge fiber Bragg grating and the second long gauge fiber Bragg grating can be expressed as:

[0022]

[0023] In addition, the present invention also provides a method for installing a non-invasive measurement sensor for pipeline pressure monitoring, the installation method comprising the following steps:

[0024] Step 1) firstly fix the two ends of the first long gauge fiber Bragg grating and the second long gauge fiber Bragg grating to the bonding position of the two substrates by adhesive to form a sensing unit;

[0025] Step 2) installing the first caliper and the second caliper on both sides of the pipeline respectively;

[0026] Step 3) The sensing unit and the upper elastic member are mounted on the upper ends of the first caliper and the second caliper by screws. During the mounting, the first substrate mounting hole and the second substrate mounting hole of the two substrates of the sensing unit coincide with the axes of the first upper elastic fixing hole and the second upper elastic fixing hole of the upper elastic member and the first upper fixing hole at the upper end of the first caliper and the second upper fixing hole at the upper end of the second caliper;

[0027] Step 4) Install the lower elastic member on the lower ends of the first caliper and the second caliper by screws. The placement principle is that the center lines of the first lower elastic fixing hole and the second lower elastic fixing hole of the lower elastic member coincide with the center lines of the first lower fixing hole and the second lower fixing hole of the lower end of the first caliper and the second lower fixing hole of the lower end of the second caliper.

[0028] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0029] 1) The non-invasive measurement sensor provided by the present invention includes a fixed caliper and an elastic element. The fixed caliper includes a first caliper and a second caliper. The first caliper and the second caliper are symmetrically spaced. The elastic element includes an upper elastic member and a lower elastic member. The upper and lower ends of the first caliper are connected to the upper and lower ends of the second caliper through the upper elastic member and the lower elastic member. The first caliper and the second caliper are combined to form a through groove for clamping the pipeline. The upper elastic member at the upper end of the first caliper and the second caliper is installed with a sensing unit. The sensing unit includes two substrates and a long-gauge double grating structure. The long-gauge double grating structure is located between the two substrates and fixed on the two substrates. The installation and fixing method of the non-invasive measuring sensor and the pipeline provided by the present invention can realize the pressure measurement of the pipeline without destroying the integrity of the pipeline structure. The elastic elements at the upper and lower ends of the first caliper and the second caliper have stretching and contraction functions, and the structural dimensions of the non-invasive measuring sensor can be flexibly adjusted according to different pipeline sizes. The non-invasive measuring sensor can adapt to harsh environments such as strong electromagnetic interference and strong chemical corrosion, and the wiring and installation method of its internal structure is very simple, which can reduce the operating difficulty of the monitoring personnel.

[0030] 2) The long gauge length dual grating structure provided by the present invention includes a first long gauge length fiber grating and a second long gauge length fiber grating, and the first long gauge length fiber grating and the second long gauge length fiber grating are spaced apart and parallelly distributed between two substrates. The non-invasive measurement sensor of the present invention can flexibly adjust the sensitivity of the sensing unit by adjusting the effective length of the two long gauge length fiber gratings. Since the two long gauge length fiber gratings adopt a long gauge length structure, the radial strain of the pipeline can be significantly amplified. Compared with other types of fiber grating pipeline pressure sensors, it has a higher sensitivity. In addition, the long gauge length dual grating structure design can eliminate the influence of ambient temperature on the measurement results, so that the measurement data is not affected by the ambient temperature.

[0031] 3) The measurement method of the non-invasive measurement sensor provided by the present invention includes: measuring the change in the inner diameter pressure of the pipeline, applying pressure p to the pipeline through a pressure chamber so that the pipeline expands uniformly under the action of the internal pressure p, and calculating the change in the internal diameter of the pipeline, establishing an equation relationship between the change in the internal diameter of the pipeline and the center wavelength offset measured by the stretching of the long-gauge double grating structure, under the relative movement of the first caliper and the second caliper, the first long-gauge fiber grating and the second long-gauge fiber grating of the long-gauge double grating structure will be stretched, and the functional relationship between the internal pressure p of the pipeline and the center wavelength offset of the first long-gauge fiber grating and the second long-gauge fiber grating is obtained by stretching calculation, and the first caliper and the second caliper directly convert the diameter change of the pipeline into the axial displacement of the two long-gauge fiber gratings. The measurement method and measurement principle of the present invention are simple. By adopting the long-gauge double grating structure design, the influence of temperature changes can be eliminated, and the errors caused by structural asymmetry caused by factors such as processing can be further eliminated.

[0032] 4) The first long gauge fiber Bragg grating and the second long gauge fiber Bragg grating of the non-invasive measurement sensor provided by the present invention are connected and fixed to two substrates by adhesive. The first long gauge fiber Bragg grating and the second long gauge fiber Bragg grating are connected to the two substrates by two points, thereby avoiding the problems of fiber Bragg grating chirp, poor thermal stability and uneven stress caused by adhesive wetting.

[0033] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following is a detailed description in combination with the preferred embodiments and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 is a schematic diagram of the overall structure of the non-invasive measurement sensor in the first embodiment of the present invention;

[0036] Figure 2 Schematic diagram of the connection relationship between the fixed caliper, the elastic element and the pipeline in the first embodiment of the present invention Figure 1 ;

[0037] Figure 3 Schematic diagram of the connection relationship between the fixed caliper, the elastic element and the pipeline in the first embodiment of the present invention Figure 2 ;

[0038] Figure 4 is a schematic structural diagram of an upper elastic member in Embodiment 1 of the present invention;

[0039] Figure 5 is a schematic structural diagram of the lower elastic member in the first embodiment of the present invention;

[0040] Figure 6 It is a structural schematic diagram of the sensor unit in the first embodiment of the present invention.

[0041] In the figure, a fixed caliper 1, a first caliper 11, a second caliper 12, an elastic element 2, an upper elastic member 21, a lower elastic member 22, a sensing unit 3, a substrate 31, a long-gauge dual grating structure 32, a first long-gauge fiber grating 321, a second long-gauge fiber grating 322, a screw 4, and a pipe 5 are shown. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0043] Embodiment 1, as Figure 1-Figure 5As shown, the present invention provides a non-invasive measurement sensor for monitoring a pipeline 5, the non-invasive measurement sensor comprising a fixed caliper 1 and an elastic element 2, the fixed caliper 1 comprising a first caliper 11 and a second caliper 12, the first caliper 11 and the second caliper 12 are symmetrically spaced, the elastic element 2 comprises an upper elastic member 21 and a lower elastic member 22, the upper elastic member 21 and the lower elastic member 22 are symmetrically distributed in the upper and lower directions, the upper elastic member 21 and the lower elastic member 22 are in a serpentine elastic structure, the upper and lower ends of the first caliper 11 are connected to the upper and lower ends of the second caliper 12 through the upper elastic member 21 and the lower elastic member 22, the first caliper 11 and the second caliper 12 are surrounded to form a through groove for clamping the pipeline 5, the upper elastic member 21 at the upper ends of the first caliper 11 and the second caliper 12 is installed with a sensing unit 3, the first caliper 1 1 and the second caliper 12 are located at the left and right ends of the sensing unit 3. The sensing unit 3 includes two substrates 31 and a long-gauge double grating structure 32. The two substrates 31 are symmetrically installed at both ends of the upper elastic member 21. The long-gauge double grating structure 32 is located between the two substrates 31 and fixed on the two substrates 31. The non-invasive measurement sensor can be fixed to the pipeline 5 without destroying the internal structure of the pipeline 5, thereby avoiding the problem of damage to the pipeline 5. In addition, the non-invasive measurement sensor can adapt to harsh environments such as strong electromagnetic interference and strong chemical corrosion. The wiring installation method of its internal structure is very simple. The elastic elements 2 at the upper and lower ends of the first caliper 11 and the second caliper 12 have stretching and contraction effects, and the structural dimensions of the non-invasive measurement sensor can be flexibly adjusted according to the sizes of different pipelines 5.

[0044] In specific implementation, the long-gauge dual-grating structure 32 of the present invention includes a first long-gauge fiber grating 321 and a second long-gauge fiber grating 322. The first long-gauge fiber grating 321 and the second long-gauge fiber grating 322 are distributed in parallel between two substrates 31 with a spacing therebetween. The sensitivity of the sensing unit 3 can be flexibly adjusted by adjusting the effective length of the two long-gauge fiber gratings. Since the two long-gauge fiber gratings adopt a long-gauge structure, the radial strain of the pipeline 5 can be significantly amplified, and the sensitivity is higher than other types of fiber grating pipeline pressure sensors.

[0045] When the embodiment of the present invention is implemented, the surfaces of the two substrates 31 are provided with bonding parts, and both ends of the first long gauge fiber grating 321 and the second long gauge fiber grating 322 are fixed at the bonding parts of the two substrates 31 to form the sensing unit 3. A hollow area is formed between the two substrates 31. The two substrates 31 can be made of stainless steel sheets. The thickness of the substrate 31 can be set to 0.15-2.00 mm. It is only necessary to drill holes at the positions of the two substrates 31 with an electric drill, and use adhesive to stick the first long-gauge fiber grating 321 and the second long-gauge fiber grating 322 to form a sensing unit 3. Then, screws 4 are driven into the two substrates 31 to install the sensing unit 3 on the upper ends of the first clamp 11 and the second clamp 12, so that the double fixation of the long-gauge double grating structure 32 can be achieved. The structure of the sensing unit 3 is simple, and a naked packaging design is adopted between the long-gauge double grating structure 32 and the two substrates 31, so that the sensing unit 3 can be more closely fitted to the monitoring part, and the strain can be transmitted to the maximum extent, thereby improving the monitoring accuracy and installation efficiency, and facilitating the first long-gauge fiber grating 321 and the second long-gauge fiber grating 322 to be pasted and fixed to the substrate 31, and generally, adhesive is used to fix them.

[0046] In specific implementation, after the first long gauge fiber Bragg grating 321 and the second long gauge fiber Bragg grating 322 of the present invention are pasted and fixed, optical cable protection and layout are required, and the ends of the first long gauge fiber Bragg grating 321 and the second long gauge fiber Bragg grating 322 are sealed to prevent liquid from invading the first long gauge fiber Bragg grating 321 and the second long gauge fiber Bragg grating 322.

[0047] In other embodiments, the present invention can make double-ended leads at both ends of the first long gauge fiber Bragg grating 321 and the second long gauge fiber Bragg grating 322, and form a quasi-distributed sensing network by connecting them in series, thereby realizing multi-point single-line measurement or simultaneous temperature measurement.

[0048] The non-invasive measurement sensor of the present invention includes four screws 4, the upper and lower ends of the first caliper 11 are provided with a first upper fixing hole and a first lower fixing hole matched with the screw 4, the upper and lower ends of the second caliper 12 are provided with a second upper fixing hole and a second lower fixing hole matched with the screw 4, the four screws 4 are respectively located at the first upper fixing hole and the first lower fixing hole at the upper and lower ends of the first caliper 11, the second upper fixing hole and the second lower fixing hole at the upper and lower ends of the second caliper 12, the two ends of the upper elastic member 21 are respectively provided with a first upper elastic fixing hole and a second upper elastic fixing hole matched with the screw 4, the two ends of the lower elastic member 22 are respectively provided with a first lower elastic fixing hole and a second lower elastic fixing hole matched with the screw 4, and the two substrates 31 are both provided with a first The substrate mounting hole and the second substrate mounting hole, two screws 4 respectively pass through the first substrate mounting hole, the second substrate mounting hole, the first upper elastic fixing hole at both ends of the upper elastic member 21, the second upper elastic fixing hole, the first upper fixing hole at the upper end of the first caliper 11, and the second upper fixing hole at the upper end of the second caliper 12 of the two substrates 31 from top to bottom in sequence to fix the upper elastic member 21 and the two substrates 31 to the upper ends of the first caliper 11 and the second caliper 12; the other two screws 4 respectively pass through the first lower elastic fixing hole, the second lower elastic fixing hole at both ends of the lower elastic member 22, the first lower fixing hole at the lower end of the first caliper 11, and the second lower fixing hole at the lower end of the second caliper 12 from bottom to top in sequence to fix the lower elastic member 22 to the lower ends of the first caliper 11 and the second caliper 12.

[0049] Embodiment 2, the present invention also provides a measurement method of a non-invasive measurement sensor for monitoring a pipeline 5, the measurement method comprising the following process:

[0050] Step S1) Pipeline 5 pressure measurement: First, measure the inner diameter pressure change of the pipeline 5, apply pressure p to the pipeline 5 through the pressure chamber to make the pipeline 5 expand evenly under the internal pressure p, and calculate the inner diameter change of the pipeline 5, the inner diameter change is:

[0051] Wherein, d is the inner diameter of the pipe 5; υ and E are the Poisson's ratio and elastic modulus of the pipe 5 material respectively; δ is the wall thickness of the pipe 5;

[0052] Step S2) Measurement of the long gauge length double grating structure 32: An equation relationship is established between the change in the internal diameter of the pipeline 5 and the central wavelength offset measured by stretching the long gauge length double grating structure 32. When the inner diameter of the pipeline 5 changes, the sensing unit 3, under the action of the elastic element 2, the left and right first calipers 11 and the second caliper 12 of the sensing unit 3 can move with the deformation of the pipeline 5. According to the displacement coordination relationship, the relative displacement ΔL of the first caliper 11 and the second caliper 12 and the change Δd of the inner diameter of the pipeline 5 have the following equation relationship: Δd=ΔL;

[0053] Under the relative movement of the first caliper 11 and the second caliper 12, the first long gauge fiber Bragg grating 321 and the second long gauge fiber Bragg grating 322 of the long gauge dual grating structure 32 will be stretched, and the central wavelength offsets Δλ1 and Δλ2 of the first long gauge fiber Bragg grating 321 and the second long gauge fiber Bragg grating 322 can be expressed as:

[0054]

[0055] In the expression, λ1 and λ2 are the initial center wavelengths of the first long gauge fiber Bragg grating 321 and the second long gauge fiber Bragg grating 322, respectively, and |K|≠0, L1 and L2 are the initial lengths of the first long gauge fiber Bragg grating 321 and the second long gauge fiber Bragg grating 322, respectively, and p e is the elastic-optic coefficient of the fiber Bragg grating, α is the thermal expansion coefficient of the fiber Bragg grating, ξ is the thermo-optic coefficient of the fiber Bragg grating, and ΔT is the change in ambient temperature;

[0056] Combining the above expressions (1) and (2), the functional relationship between the internal pressure p of the pipeline 5 and the central wavelength offset of the first long gauge fiber Bragg grating 321 and the second long gauge fiber Bragg grating 322 can be expressed as:

[0057]

[0058] The measurement method provided by the present invention can eliminate the influence of temperature change by adopting the long-gauge-length double-grating structure 32 design, and can further eliminate the error caused by structural asymmetry caused by factors such as processing.

[0059] Embodiment 3, the present invention also provides a method for installing a non-intrusive measurement sensor for monitoring a pipeline 5, the installation method comprising the following steps:

[0060] Step 1) First, two ends of the first long gauge fiber Bragg grating 321 and the second long gauge fiber Bragg grating 322 are bonded and fixed to the bonding position of the two substrates 31 by adhesive to form a sensing unit 3;

[0061] Step 2) Install the first caliper 11 and the second caliper 12 on both sides of the pipe 5 respectively;

[0062] Step 3) The sensor unit 3 and the upper elastic member 21 are mounted on the upper ends of the first caliper 11 and the second caliper 12 by means of screws 4. During the mounting, the first substrate mounting hole and the second substrate mounting hole of the two substrates 31 of the sensor unit 3 coincide with the axes of the first upper elastic fixing hole and the second upper elastic fixing hole of the upper elastic member 21 and the first upper fixing hole at the upper end of the first caliper 11 and the second upper fixing hole at the upper end of the second caliper 12;

[0063] Step 4) Install the lower elastic member 22 on the lower ends of the first caliper 11 and the second caliper 12 by means of screws 4. The placement principle is that the center lines of the first lower elastic fixing hole and the second lower elastic fixing hole of the lower elastic member 22 coincide with the center lines of the first lower fixing hole at the lower end of the first caliper 11 and the second lower fixing hole at the lower end of the second caliper 12.

[0064] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A non-invasive measurement sensor for pipeline pressure monitoring, characterized in that: The non-invasive measurement sensor includes a fixed caliper and an elastic element. The fixed caliper includes a first caliper and a second caliper. The first caliper and the second caliper are symmetrically spaced. The elastic element includes an upper elastic member and a lower elastic member. The upper elastic member and the lower elastic member are symmetrically spaced. The upper and lower ends of the first caliper are connected to the upper and lower ends of the second caliper through the upper elastic member and the lower elastic member. The first caliper and the second caliper are surrounded to form a through groove for clamping the pipeline. The upper elastic member at the upper end of the first caliper and the second caliper is installed with a sensing unit. The first caliper and the second caliper are located at the left and right ends of the sensing unit. The sensing unit includes two substrates and a long-gauge double grating structure. The two substrates are symmetrically spaced and installed at a distance. At both ends of the upper elastic member, the long gauge dual grating structure is located between the two substrates and fixed on the two substrates, the long gauge dual grating structure includes a first long gauge fiber grating and a second long gauge fiber grating, the first long gauge fiber grating and the second long gauge fiber grating are distributed in parallel between the two substrates at intervals, the first long gauge fiber grating and the second long gauge fiber grating are connected to the two substrates in a two-point manner, the two long gauge fiber gratings adopt a long gauge structure, which can significantly amplify the radial strain of the pipeline, the upper elastic member and the lower elastic member are serpentine elastic structures, and the functional relationship between the internal pressure p of the pipeline and the central wavelength offset of the first long gauge fiber grating and the second long gauge fiber grating can be expressed as: Wherein, d is the inner diameter of the pipeline, υ and E are the Poisson's ratio and elastic modulus of the pipeline material, respectively; δ is the wall thickness of the pipeline, the change in the inner diameter of the pipeline is Δd, λ1 and λ2 are the initial central wavelengths of the first long gauge fiber Bragg grating and the second long gauge fiber Bragg grating, respectively, Δλ1 and Δλ2 are the central wavelength offsets of the first long gauge fiber Bragg grating and the second long gauge fiber Bragg grating, respectively, L1 and L2 are the initial lengths of the first long gauge fiber Bragg grating and the second long gauge fiber Bragg grating, respectively, p e is the elastic-optical coefficient of the fiber Bragg grating.

2. The non-invasive measurement sensor for pipeline pressure monitoring according to claim 1, characterized in that: The surfaces of the two substrates are provided with bonding parts, and the two ends of the first long gauge fiber grating and the second long gauge fiber grating are fixed at the bonding parts of the two substrates to form a sensing unit.

3. The non-invasive measurement sensor for pipeline pressure monitoring according to claim 1, characterized in that: The first long gauge fiber Bragg grating and the second long gauge fiber Bragg grating are applied to the bonding parts of the two substrates with adhesive to achieve the fixation of the first long gauge fiber Bragg grating and the second long gauge fiber Bragg grating to the two substrates.

4. The non-invasive measurement sensor for pipeline pressure monitoring according to claim 1, characterized in that: The non-invasive measurement sensor includes four screws, and the upper and lower ends of the first caliper are provided with a first upper fixing hole and a first lower fixing hole that match the screws, and the upper and lower ends of the second caliper are provided with a second upper fixing hole and a second lower fixing hole that match the screws, and the four screws are respectively located at the first upper fixing hole and the first lower fixing hole at the upper and lower ends of the first caliper, and the second upper fixing hole and the second lower fixing hole at the upper and lower ends of the second caliper.

5. The non-invasive measurement sensor for pipeline pressure monitoring according to claim 1, characterized in that: The two ends of the upper elastic member are respectively provided with a first upper elastic fixing hole and a second upper elastic fixing hole that match the screws, the two ends of the lower elastic member are respectively provided with a first lower elastic fixing hole and a second lower elastic fixing hole that match the screws, and the two substrates are both provided with a first substrate mounting hole and a second substrate mounting hole that match the screws. The two screws pass through the first substrate mounting hole, the second substrate mounting hole, the first upper elastic fixing hole, the second upper elastic fixing hole at both ends of the upper elastic member, the first upper fixing hole at the upper end of the first caliper, and the second upper fixing hole at the upper end of the second caliper from top to bottom to fix the two substrates and the upper elastic member to the upper ends of the first caliper and the second caliper; the other two screws pass through the first lower elastic fixing hole, the second lower elastic fixing hole, the first lower fixing hole at the lower end of the first caliper, and the second lower fixing hole at the lower end of the second caliper from bottom to top to fix the lower elastic member to the lower ends of the first caliper and the second caliper.

6. A measurement method of a non-invasive measurement sensor for pipeline pressure monitoring according to claim 1, characterized in that: The measurement method includes the following procedures: Step S1) Pipeline pressure measurement: First, measure the inner diameter pressure change of the pipeline, apply pressure p to the pipeline through the pressure chamber to make the pipeline expand evenly under the internal pressure p, and calculate the change in the inner diameter of the pipeline. The inner diameter change is: Where d is the inner diameter of the pipe; υ and E are the Poisson's ratio and elastic modulus of the pipe material, respectively; δ is the wall thickness of the pipe; Step S2) Measurement of the long gauge length double grating structure: An equation relationship is established by the change in the internal diameter of the pipeline and the central wavelength offset measured by stretching the long gauge length double grating structure. When the inner diameter of the pipeline changes, the sensing unit, under the action of the elastic element, the left and right first calipers and the second caliper of the sensing unit can move with the deformation of the pipeline. According to the displacement coordination relationship, the relative displacement ΔL of the first caliper and the second caliper and the change in the inner diameter of the pipeline Δd have the following equation relationship: Δd=ΔL; Under the relative movement of the first caliper and the second caliper, the first long-gauge fiber Bragg grating and the second long-gauge fiber Bragg grating of the long-gauge dual-gauge structure will be stretched, and the central wavelength offsets Δλ1 and Δλ2 of the first long-gauge fiber Bragg grating and the second long-gauge fiber Bragg grating can be expressed as: In the expression, λ1 and λ2 are the initial center wavelengths of the first and second long gauge fiber Bragg gratings, respectively, and |K|≠0, L1 and L2 are the initial lengths of the first and second long gauge fiber Bragg gratings, respectively, and p e is the elastic-optic coefficient of the fiber Bragg grating, α is the thermal expansion coefficient of the fiber Bragg grating, ξ is the thermo-optic coefficient of the fiber Bragg grating, and ΔT is the change in ambient temperature; Combining the above expressions (1) and (2), the functional relationship between the internal pressure p of the pipeline and the central wavelength offset of the first long gauge fiber Bragg grating and the second long gauge fiber Bragg grating can be expressed as:

7. A method for installing a non-invasive measurement sensor for pipeline pressure monitoring according to claim 1, characterized in that: The installation method comprises the following steps: Step 1) firstly fix the two ends of the first long gauge fiber Bragg grating and the second long gauge fiber Bragg grating to the bonding position of the two substrates by adhesive to form a sensing unit; Step 2) installing the first caliper and the second caliper on both sides of the pipeline respectively; Step 3) The sensing unit and the upper elastic member are mounted on the upper ends of the first caliper and the second caliper by screws. During the mounting, the first substrate mounting hole and the second substrate mounting hole of the two substrates of the sensing unit coincide with the axes of the first upper elastic fixing hole and the second upper elastic fixing hole of the upper elastic member and the first upper fixing hole at the upper end of the first caliper and the second upper fixing hole at the upper end of the second caliper; Step 4) Install the lower elastic member on the lower ends of the first caliper and the second caliper by screws. The placement principle is that the center lines of the first lower elastic fixing hole and the second lower elastic fixing hole of the lower elastic member coincide with the center lines of the first lower fixing hole and the second lower fixing hole of the lower end of the first caliper and the second lower fixing hole of the lower end of the second caliper.

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