Composite detection optical fiber and valve leakage detection device using same

Abstract

The utility model relates to a composite detection optical fiber and a valve leakage detection device using the same, the composite detection optical fiber comprises an optical fiber unit and a grating unit, the optical fiber unit comprises a temperature sensing optical fiber and a vibration sensing optical fiber, and the grating unit comprises a pressure optical fiber grating and a sound wave optical fiber grating; the valve leakage detection device comprises a composite detection optical fiber, an optical fiber data acquisition module, a data processing module, a neural network processing module and an output display module. The one-cable multi-core composite detection optical fiber is simple to install and small in laying amount; four types of sensors are adopted to analyze data of different areas of the valve, so that the inner leakage of the valve can be detected, and the outer leakage of the valve can also be detected; the neural network processing module not only can accurately judge the leakage of the valve, but also can accurately position the leakage area of the valve, predict the leakage range of the valve, establish a multi-parameter monitoring model of the valve, and provide visual and accurate display for the safe operation of the valve.

Description

Technical Field

[0001] The utility model relates to the technical field of leakage monitoring, in particular to a composite detection optical fiber and a valve leakage detection device using the optical fiber. Background Art

[0002] In pipeline systems such as petrochemicals and natural gas, valves are an indispensable part of the device, and valves are also widely used in liquefied hydrocarbon pipelines and equipment. Valves on liquefied hydrocarbon pipelines and equipment often come into contact with liquefied hydrocarbon chemicals, and liquefied hydrocarbon chemicals often have high pressure and flow rate. After long-term use, these valves often have valve leakage accidents, which will cause the loss of transmission media and production failures; therefore, in the actual production process, timely and accurate detection of valve leakage can avoid major accidents and disasters and greater economic losses, which is of great significance.

[0003] Valve leakage can be classified into two types: external leakage and internal leakage, depending on the flow direction of the medium. External leakage of valves refers to the leakage of the transmission medium outside the valve body, mainly caused by failures in the sealing packing of the valve stem and the connection of the valve body. The main reasons for external leakage of valves are improper installation of flanges or packing, etc. The leaking medium is directly exposed to the on-site environment, which is very likely to cause fires when encountering high-energy equipment or high-temperature areas. Internal leakage of valves refers to the phenomenon that when the fluid passes through the valve, the fluid cannot be blocked by the valve plate, valve disc, etc. and continues to flow out of the outlet direction. Because internal leakage of valves occurs inside the valve cavity, it is not easy to be observed and is often easily ignored, but the internal leakage of valves has a significant impact on the safe operation of production.

[0004] There are two main conventional valve leakage detection methods: one is direct observation detection, that is, the technician observes with the naked eye and listens with the ears. However, when the leaking material is seen and the sound of steam leakage is heard, the leakage may be too large; the other is to use a handheld valve leakage device to detect whether the valve is leaking. The internal leakage of the valve is currently detected by means of sound sensors, ultrasonic detection, infrared thermal imaging detection, etc.

[0005] A Chinese invention patent with application number 201010590565.1 (publication number CN102095083A) discloses a detection system for gas valve leakage, which mainly uses temperature transmitters, ultrasonic detectors, and pressure detectors installed before and after the valve for leakage detection. The invention sets up a variety of independent detection instruments, and the equipment installation and configuration are complicated. It is an active detection device that is not intrinsically safe. The three sensors are set independently and cannot determine multiple parameters in the same area. Therefore, the leakage positioning accuracy is insufficient. At the same time, it does not analyze different working conditions. There are many working conditions in the operation of the valve, and there are different interferences, which will interfere with the detection of temperature, pressure, and ultrasonic waves. Secondly, it does not propose a design for the fusion judgment of several sensor data. It simply judges the leakage from the detection value of a certain sensor, which has limited accuracy and precision and a high false alarm rate.

[0006] In general, the existing technical solutions still have the following problems: (1) When using multiple sensors for detection, it is often impossible to conduct centralized detection of multiple parameters in a certain area, it is impossible to centrally detect various leakage conditions in a certain area, and it is also impossible to conduct regional and category detection of valve characteristics and valve leakage-prone areas; (2) When setting up multiple detectors to detect leaks, there are many types of sensors, a large amount of sensor equipment to be installed, high installation requirements, and a large amount of optical fiber sensors to be laid, and it is also impossible to simultaneously detect internal and external leakage of the valve. Summary of the invention

[0007] The first technical problem to be solved by the utility model is to provide a composite detection optical fiber in view of the current status of the prior art.

[0008] The second technical problem to be solved by the utility model is to provide a valve leakage detection device using the above-mentioned composite detection optical fiber in view of the current status of the prior art.

[0009] The technical solution adopted by the utility model to solve the first technical problem mentioned above is: the composite detection optical fiber is characterized in that: the composite detection optical fiber includes an optical fiber unit and a grating unit, the optical fiber unit includes a temperature sensing optical fiber and a vibration sensing optical fiber, and the grating unit includes a pressure optical fiber grating and an acoustic optical fiber grating; an isolation layer is provided inside the composite detection optical fiber, and the isolation layer separates the optical fiber unit and the grating unit.

[0010] In order to prevent the detection lights of the optical fiber unit and the grating unit from interfering with each other, the temperature sensing optical fiber and the vibration sensing optical fiber are located on one side of the isolation layer, and the pressure fiber grating and the acoustic fiber grating are located on the other side of the isolation layer.

[0011] Furthermore, a grating unit is arranged at the same distance in the length direction of the composite detection optical fiber, and the pressure fiber grating and the acoustic fiber grating in each of the grating units are packaged at the same position.

[0012] Furthermore, the spacing distance between each of the grating units is within 1 meter, and the spacing distance is selected according to the positioning accuracy requirement.

[0013] In order to facilitate the fixing and installation of the composite detection optical fiber, welding points and / or magnetic points are set at the packaging of the pressure fiber grating and the acoustic fiber grating. The welding points and magnetic points enable the composite detection optical fiber to be fixed more accurately at a specific position of the valve and the vicinity of the valve, providing a basis for accurately detecting the leakage point.

[0014] Furthermore, an outer sheath is disposed outside the composite detection optical fiber, and the cross section of the outer sheath is flat. The flat outer sheath is convenient for attachment and fixation to the valve and a position near the valve.

[0015] The technical solution adopted by the utility model to solve the second technical problem is: the valve leakage detection device using the composite detection optical fiber is characterized in that the composite detection optical fiber is laid on the outer wall of the valve body, or the inlet flange of the valve, or the outlet flange of the valve, or the pipeline upstream and downstream of the valve. The composite detection optical fiber is laid at the above position to detect external leakage.

[0016] Furthermore, the valve stem and the valve body are connected via a connecting flange, and the composite detection optical fiber is laid in the connecting surface area of ​​the connecting flange upstream and downstream and the connecting flange, or the composite detection optical fiber is laid at the valve packing. The composite detection optical fiber is laid at the above position for detecting internal leakage.

[0017] In order to accurately locate the location of the internal leakage, the pressure fiber Bragg grating and the acoustic fiber Bragg grating are set in the connection surface area of ​​the connecting flange or the valve packing.

[0018] Furthermore, the valve leakage detection device also includes an optical fiber data acquisition module, a data processing module, a neural network processing module and an output display module; a laser is used as an incident light source, the incident light source enters the composite detection optical fiber, and reaches the temperature sensing optical fiber, the vibration sensing optical fiber, the pressure optical fiber grating and the acoustic fiber grating respectively, the composite detection optical fiber is connected to the optical fiber data acquisition module, and the optical fiber data acquisition module, the data processing module, the neural network processing module and the output display module are connected in sequence.

[0019] Furthermore, the data processing module also receives valve status, material flow rate and material pressure data sent by the DCS distributed control system.

[0020] Furthermore, the training of the neural network model of the neural network processing module includes the following steps:

[0021] A1: Collect various parameter signals of pipelines and valves under multiple working conditions when they are leaking and various parameter signals of common non-leakage conditions;

[0022] A2: Extract sample data sets of temperature, pressure, vibration, and sound waves of each valve in leakage and non-leakage states; the leakage state includes parameter data of leakages of different regions, different working conditions, different valves, and different sizes; the non-leakage state includes parameter data of leakages of different regions, different working conditions, and different valves during normal operation;

[0023] A3: Divide the sample data set into training set, validation set and test set;

[0024] A4: Process the training set samples to optimize the training model;

[0025] A5: Optimize the neural network model parameters based on the validation set.

[0026] Furthermore, the neural network model input value includes at least one of the following: temperature sensing fiber optic detection value, vibration sensing fiber optic detection value, pressure fiber grating sensor detection value, acoustic fiber grating sensor detection value, valve type, valve state, valve size, material pressure, material flow rate, and detection area.

[0027] Furthermore, the output value of the neural network model includes at least one of the following: leakage type, leakage degree, and leakage area.

[0028] Compared with the prior art, the advantages of the utility model are:

[0029] (1) A composite detection optical fiber is proposed, which has multiple cores, including temperature sensing optical fiber, vibration sensing optical fiber, pressure optical fiber Bragg grating and acoustic wave optical fiber Bragg grating. The composite detection optical fiber is easy to install and requires a small amount of laying. In addition, four sensors are used to analyze data from different areas of the valve, which can detect not only internal leakage of the valve, but also external leakage of the valve, with a complete detection range.

[0030] (2) Under the premise that the positioning accuracy of the temperature sensing fiber and the vibration sensing fiber is 0.5 to 1 m, the packaging of the pressure fiber Bragg grating and the acoustic fiber Bragg grating is precisely laid in the area prone to leakage, so that the pressure fiber Bragg grating and the acoustic fiber Bragg grating can transmit the position signal to the data processing system, and the position signal of the optical fiber unit and the grating unit can be combined to more accurately locate the location of the leakage;

[0031] (3) It comprehensively considers the valve status, pipeline working status, pipeline pressure, pipeline flow, etc., and makes judgments through neural network learning, eliminating interference signals in the working process of pipeline valves, greatly improving the accuracy of judgment, and being targeted and applicable;

[0032] (4) The neural network processing module can not only accurately determine the leakage of the valve, but also accurately locate the area of ​​the valve leakage and predict the range of the valve leakage, and establish a multi-parameter monitoring model for the valve, providing an intuitive and accurate display for the safe operation of the valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the structure of the composite detection optical fiber in the embodiment of the utility model;

[0034] Figure 2 This is a schematic diagram of laying the composite detection optical fiber when detecting leakage in an embodiment of the utility model;

[0035] Figure 3 This is a schematic diagram of laying the composite detection optical fiber when detecting internal leakage in the embodiment of the utility model;

[0036] Figure 4 This is a schematic diagram of the composition of the valve leakage detection device in the embodiment of the utility model;

[0037] Figure 5 This is a flow chart of valve leakage detection in an embodiment of the utility model;

[0038] Figure 6 Schematic diagram of a neural network model of a neural network processing module in an embodiment of the present utility model. DETAILED DESCRIPTION

[0039] The present invention will be described in further detail below in conjunction with the accompanying drawings.

[0040] Example 1

[0041] like Figure 1 The figure shows a preferred embodiment of the composite detection optical fiber of the utility model. The composite detection optical fiber 1 is a multi-core cable, which includes an optical fiber unit, a grating unit and an isolation layer 15. An outer sheath 17 is arranged outside the composite detection optical fiber. The isolation layer 15 separates the optical fiber unit and the grating unit. The outer sheath 17 with a flat cross-section is sleeved outside the isolation layer 15, the optical fiber unit and the grating unit.

[0042] The optical fiber unit includes a temperature sensing optical fiber 11 and a vibration sensing optical fiber 12, and the grating unit includes a pressure optical fiber grating 13 and an acoustic fiber grating 14. The temperature sensing optical fiber 11 and the vibration sensing optical fiber 12 are located on one side of the isolation layer 15, and the pressure optical fiber grating 13 and the acoustic fiber grating 14 are located on the other side of the isolation layer 15.

[0043] A grating unit is arranged at a certain distance in the length direction of the composite detection optical fiber 1, and the pressure fiber grating 13 and the acoustic fiber grating 14 in each grating unit are packaged in the same position; the temperature sensing optical fiber 11 and the vibration sensing optical fiber 12 in the composite detection optical fiber can determine the location of the leak by using the optical fiber transmission characteristics, and the detection positioning accuracy is usually 0.5 to 1m. So how to improve the positioning accuracy within 1m? The utility model proposes to arrange a grating unit at a certain distance (selected within 1 meter according to the positioning accuracy requirement) in the composite detection optical fiber 1, and the change position within 1m can be accurately located through the alarm positioning of the above grating unit. In addition, welding points 161 and / or magnetic points 162 are arranged at the packaging of the pressure fiber grating 13 and the acoustic fiber grating 14, and the welding points 161 and the magnetic points 162 are fixed at the valve and the position near the valve where leakage is prone to occur, providing support for accurately detecting the leakage point.

[0044] A variety of fiber optic sensors are used to detect valve leakage status, and fiber optic filters of different wavelengths are connected. The fiber optic sensors do not interfere with each other, which improves the detection accuracy. Ordinary optical fiber is used as the detection fiber, and a temperature measurement fiber core and a vibration fiber core are set. Pressure fiber gratings and acoustic fiber gratings are arranged at equal intervals inside. Quasi-distributed fiber optic sensing technology can use the same optical fiber to multiplex multiple stress sensors, thereby achieving accurate measurement of fixed-point temperature, pressure, and sound waves at key parts of the pipeline to be tested, such as flanges, packings, and valve covers.

[0045] Example 2

[0046] like Figures 2 to 4 The figure shows a preferred embodiment of the valve leakage detection device of the utility model, which includes the above-mentioned composite detection optical fiber 1, and also includes an optical fiber data acquisition module, a data processing module, a neural network processing module and an output display module; a laser is used as an incident light source, and the incident light source enters the composite detection optical fiber 1, and reaches the temperature sensing optical fiber 11, the vibration sensing optical fiber 12, the pressure optical fiber grating 13 and the acoustic fiber grating 14 respectively, the composite detection optical fiber 1 is connected to the optical fiber data acquisition module, the optical fiber data acquisition module, the data processing module, the neural network processing module and the output display module are connected in sequence, and at the same time, the data processing module receives the data of the valve 2 state, material flow rate and material pressure sent by the DCS distributed control system, such as Figure 4 When the data processing module receives the data from the composite detection optical fiber 1 and the DCS distributed control system, the valve leakage detection device can judge and determine the area where the valve 2 leaks, issue a leakage alarm message, and also predict the scope of the leakage, wherein the data from the composite detection optical fiber 1 includes temperature changes, vibration signals, pressure changes, and sound wave signals generated by the leakage of the liquefied hydrocarbon medium, as well as the position data of the composite detection optical fiber 1 locating the leakage area.

[0047] The leakage caused by the valve 2 during installation and use includes internal leakage and external leakage. Therefore, in a specific embodiment, the composite detection optical fiber 1 of the valve leakage detection device is laid on the outer wall of the valve body of the valve 2, or the inlet flange 41 of the valve 2, or the outlet flange 42 of the valve 2, or the pipeline 3 upstream and downstream of the valve 2, for detecting the external leakage of the valve, such as Figure 2 As shown; the composite detection optical fiber 1 of the valve leakage detection device is also laid in the connection surface area of ​​the connecting flange 21 upstream and downstream of the valve stem and the valve body and the connecting flange 21, and the composite detection optical fiber 1 is also laid in the valve packing 22 for detecting the internal leakage of the valve, such as Figure 3 shown.

[0048] Specifically, for internal leakage of the valve: the valve stem and the valve body of the valve 2 are connected by a connecting flange 21, the composite detection optical fiber 1 is wound around the upstream and downstream sides of the connecting flange 21 and the connecting surface area of ​​the connecting flange 21, and at least ensure that the pressure fiber grating 13 and the acoustic fiber grating 14 are arranged on the connecting surface of the connecting flange 21; the composite detection optical fiber 1 is wound around the valve packing 22, and the pressure fiber grating 13 and the acoustic fiber grating 14 are arranged in the valve packing 22.

[0049] When there is a leak in the valve, the transport medium in the valve will form a multiphase turbulent jet, which will impact the valve wall and radiate energy outward, generating a high-speed contraction noise. The stress wave of the generated noise signal will propagate along the valve body and other components, namely, acoustic emission signals such as jet noise, eddy noise and turbulent noise; when a leak appears on the valve sealing surface, the liquefied hydrocarbon medium will be sprayed through the valve damage point due to the pressure difference and collide with the inner wall of the valve and the pipe wall to form turbulence and generate transient acoustic wave signals. The acoustic fiber grating 14 of the composite detection optical fiber 1 can detect the acoustic wave signal when leaking. In addition, the internal leakage of the valve will cause a weak vibration of the pipeline. The vibration sensing optical fiber 12 attached to the valve and the outer wall of the pipeline near the valve can collect the vibration signal of the leakage, and the internal leakage of the valve can be detected by analyzing the vibration signal of the pipe wall when the valve leaks. In addition, internal leakage of the valve will cause a temperature difference between the upstream and downstream of the valve. By utilizing the difference between the temperature of the liquefied hydrocarbon transmitted by the valve and the ambient temperature, a temperature sensing optical fiber 11 is arranged near the valve body to measure the valve body temperature. The heat loss caused by valve leakage will cause a significant change in the temperature of the valve outside or the pipeline downstream of the valve. The temperature sensing optical fiber 11 arranged upstream and downstream of the valve can be used to detect temperature changes to detect valve leakage failures.

[0050] In actual operation, since the leakage medium of the valve will escape into the external environment, the harm caused by the leakage will be more serious than the internal leakage. Specifically, for the leakage of the valve: the leakage parts of the valve are mainly summarized as follows: (1) Valve body leakage, that is, the valve body has cracks and other conditions that cause leakage; (2) Valve packing leakage, including loose packing gland, loose sealing packing, packing aging or wear by the valve stem. The contact between the valve stem and the packing is the most prone to leakage; (3) Valve body connection leakage: The seal of the valve body connection refers to the seal between the valve body and the valve cover, which is usually a flange connection seal. Improper tightening of the connecting bolts and poor processing quality of the flange sealing surface can cause leakage at the valve body connection; (4) Valve pipeline leakage: It is usually also a flange seal, and external leakage may occur at the seal.

[0051] When the valve leaks out, the medium flowing out of the valve body will cause temperature changes. For example, the gasification of liquefied hydrocarbon medium will cause temperature changes. After leakage, it will cause local temperature mutations. The leakage of liquefied hydrocarbon absorbs heat and gasifies, causing the surrounding temperature to drop. For this reason, the temperature changes near the valve are monitored in real time by the temperature sensing optical fiber 11 wound on the valve; after the valve leaks out, pressurized gas and liquid phases will be released at the leakage point. The pressure value is monitored in real time by setting pressure fiber gratings at the flange sealing surface, packing sealing surface, packing gland, valve cover sealing surface, etc. that are prone to leakage. The leakage of pressurized liquefied hydrocarbon will impact the pressure fiber grating 13; when the valve leaks out, the gas and liquid will rub against the wall of the leakage hole. The fluid medium leaking from the valve will impact the sealing surface and excite elastic waves. The valve leakage information is obtained by detecting the high-frequency vibration signal generated when the valve leaks. The vibration signal is detected by the vibration sensing optical fiber 12 through the high-frequency vibration signal generated when the valve leaks, so as to achieve the purpose of determining the leakage.

[0052] Example 3

[0053] like Figure 6 As shown, the utility model also introduces a neural network processing module to improve the accuracy of detection and judgment. By collecting and simulating the valve in normal state, internal leakage state, external leakage state, and combining different parameter values ​​of valve type, valve size, valve opening, closing and opening state, the architecture and hierarchy of the neural network are established. The neural network of the utility model is a deep neural network, which is an algorithm for modeling high-complexity data through multi-layer nonlinear transformation. The deep neural network is divided into three layers, namely the input layer, hidden layer and output layer. The input value of the input layer of the neural network model: the parameters of each sensor are classified and graded, and each value is normalized. The input variables include:

[0054] Temperature sensing optical fiber detection value T;

[0055] Vibration sensing optical fiber detection value Z;

[0056] Pressure fiber Bragg grating sensor detection value P1;

[0057] Acoustic fiber Bragg grating sensor detection value V;

[0058] Valve type: butterfly valve, gate valve, ball valve, etc.;

[0059] Valve status: open, closed, opening degree;

[0060] Valve size: S;

[0061] Medium pressure: P2, output by DCS to the data processing module;

[0062] Medium flow rate: V, output by DCS to the data processing module;

[0063] Valve inspection areas: inlet flange, outlet flange, valve stem, packing, valve cover, valve body.

[0064] Output value of the output layer of the neural network model: Valve leakage judgment output of the utility model:

[0065] Leakage type (non-leakage, internal leakage, external leakage);

[0066] Leakage degree (micro leak, medium leak, severe leak);

[0067] Leakage areas (valve body, bonnet, packing, interface flanges, etc.).

[0068] The neural network uses the detection value of the temperature sensing fiber 11, the detection value of the vibration sensing fiber 12, the detection value of the pressure fiber Bragg grating 13, the detection value of the acoustic fiber Bragg grating 14, the sensor detection area, the valve type, the valve size, the valve state, the material pressure, etc. as monitoring parameters to construct a neural network leakage judgment model, normalize the sensor parameter values ​​as N variables of the neural network input, and select the output values ​​as leakage judgment, leakage degree and leakage area. The most important thing in the design of the neural network is to determine the optimal number of hidden layer neurons. The correct selection of the number of hidden layer nodes is very important, and it is necessary to comprehensively consider multiple conditions (comprehensive consideration of learning and training time and error, etc.) to determine the number of hidden layer nodes. Through learning samples, the learning and training of the network is realized, and the selected neural network algorithm can better describe the correlation between the parameters by selecting a suitable transfer function.

[0069] The training of the neural network model of the neural network processing module includes the following steps:

[0070] A1: Collect various parameter signals of pipeline 3 and valve 2 under multiple working conditions when they are leaking and various parameter signals of common non-leakage;

[0071] A2: Extract sample data sets of temperature, pressure, vibration, and sound waves of each valve in leakage and non-leakage states; the leakage state includes parameter data of leakages of different regions, different working conditions, different valves, and different sizes; the non-leakage state includes parameter data of leakages of different regions, different working conditions, and different valves during normal operation;

[0072] A3: Divide the sample data set into training set, validation set and test set;

[0073] A4: Process the training set samples to optimize the training model;

[0074] A5: Optimize the neural network model parameters based on the validation set.

[0075] During the sensor detection period, there will be different working conditions such as valves and pipelines, and different interferences will be generated under various working conditions, such as environmental background noise, interference from valve switching, working conditions of different pipelines, and interference from pump start and stop. Neural networks have strong environmental adaptability, learning ability, fault tolerance and parallel processing capabilities. When the input-output relationship cannot be described by a specific function expression, the neural network intelligent algorithm can simulate the internal connection between input and output through learning and training to achieve the effect of artificial intelligence judgment.

[0076] Example 4

[0077] like Figure 5 The figure shows a flow chart of the valve leakage detection method of the utility model. The method comprises the following steps:

[0078] S1: Lay a composite detection optical fiber 1 near a valve 2 to be detected;

[0079] S2: The laser enters the composite detection optical fiber 1 as an incident light source, and the composite detection optical fiber 1 detects the temperature, vibration, stress, and acoustic wave parameters of the detected area, and transmits the parameters to the optical fiber data acquisition module;

[0080] S3: The data processing module receives the temperature, vibration, stress, acoustic wave parameter data and DCS distributed control system data collected by the optical fiber data collection module, and performs data processing;

[0081] S4: The neural network processing module performs leakage model determination on the data processing results;

[0082] S5: The output display module outputs the determination result.

[0083] The method utilizes temperature sensing optical fiber 11, vibration sensing optical fiber 12, pressure optical fiber grating 13, and acoustic wave optical fiber grating 14 to collect valve leakage signals. When the valve leaks, the valve leakage position can be located by analyzing the changes in parameters in different detection areas on the composite detection optical fiber 1, and the leakage size and trend can be predicted. Since temperature, vibration, stress, and acoustic wave parameters are related, a detection and judgment model is established through a neural network algorithm to perform real-time online intelligent detection, identification, and classification of valve leakage events, thereby solving the problem of online precise leakage detection and positioning of valves in complex environments.

Claims

1. A composite detection optical fiber, characterized in that: The composite detection optical fiber (1) comprises an optical fiber unit and a grating unit, wherein the optical fiber unit comprises a temperature sensing optical fiber (11) and a vibration sensing optical fiber (12), and the grating unit comprises a pressure optical fiber grating (13) and an acoustic optical fiber grating (14); an isolation layer (15) is provided inside the composite detection optical fiber (1), and the isolation layer (15) separates the optical fiber unit and the grating unit.

2. The composite detection optical fiber according to claim 1, characterized in that: The temperature sensing optical fiber (11) and the vibration sensing optical fiber (12) are located on one side of the isolation layer (15), and the pressure optical fiber grating (13) and the acoustic optical fiber grating (14) are located on the other side of the isolation layer (15).

3. The composite detection optical fiber according to claim 2, characterized in that: A grating unit is arranged at equal intervals in the length direction of the composite detection optical fiber, and the pressure fiber grating (13) and the acoustic fiber grating (14) in each grating unit are packaged at the same position.

4. The composite detection optical fiber according to claim 3, characterized in that: The spacing distance between each of the grating units is within 1 meter.

5. The composite detection optical fiber according to claim 4, characterized in that: A welding point (161) and / or a magnetic attraction point (162) are arranged at the packaging of the pressure fiber grating (13) and the acoustic fiber grating (14).

6. The composite detection optical fiber according to claim 5, characterized in that: The composite detection optical fiber (1) is provided with an outer sheath (17) outside, and the cross section of the outer sheath (17) is flat.

7. A valve leakage detection device using the composite detection optical fiber according to any one of claims 1 to 6, characterized in that: The composite detection optical fiber (1) is laid on the outer wall of the valve body of the valve (2), or the inlet flange (41) of the valve (2), or the outlet flange (42) of the valve (2), or the pipeline (3) upstream and downstream of the valve (2).

8. The valve leakage detection device according to claim 7, characterized in that: The valve stem and the valve body are connected via a connecting flange (21), and the composite detection optical fiber (1) is laid in the upstream and downstream areas of the connecting flange (21) and in the connecting surface area of ​​the connecting flange (21), or the composite detection optical fiber (1) is laid at the valve packing (22).

9. The valve leakage detection device according to claim 8, characterized in that: The pressure fiber grating (13) and the acoustic fiber grating (14) are arranged at the connection surface area of ​​the connection flange (21) or at the valve packing (22).

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