CN203744938U - Fiber grating sensor for on-line strain monitoring on high temperature pressure pipeline outer wall - Google Patents

Abstract

The utility model belongs to the technical field of optical fiber grating sensing, in particular to an optical fiber grating sensor for on-line monitoring of strain on the outer wall of a high-temperature pressure pipeline. The fiber grating sensor includes a direct sensing arm, a rhombic base, an indirect sensing arm and a high temperature resistant fiber Bragg grating. The direct sensing arm, the diamond-shaped base and the indirect sensing arm are an integrated metal base structure, and the materials thereof are selected as consistent as possible with the high-temperature pressure pipeline; the high-temperature-resistant fiber Bragg grating is fixed on the indirect sensing arm by low-temperature glass solder. In the olive groove of the arm; the interior angle of the rhomboid base is 60° in the direction of the direct sensing arm. The fiber grating sensor for on-line monitoring of the strain on the outer wall of a high-temperature pressure pipeline described in the utility model can monitor the safety status of high-temperature components such as high-temperature pressure pipelines on-line at a high temperature of 300°C, detect strain abnormalities in advance, and remind enterprises in time Repair or replace related equipment to avoid pipe burst accidents.

Description

A Fiber Bragg Grating Sensor for On-line Monitoring of Outer Wall Strain of High Temperature Pressure Pipeline

technical field

The invention relates to the field of optical fiber grating sensing technology, in particular to an optical fiber grating sensor for on-line monitoring of strain on the outer wall of a high-temperature pressure pipeline, which is suitable for on-line monitoring of strain on the surfaces of various high-temperature components such as high-temperature pressure pipelines. the

Background technique

Since K.O.Hill et al. discovered the photosensitivity of optical fibers in 1978 and used the longitudinal standing wave writing method to make the world's first fiber Bragg grating, fiber Bragg gratings are inherently safe, light in weight, small in size, free from electromagnetic interference, and easy to use. Due to its unique advantages such as multiplexing and long-distance telemetry, it has been widely used in the field of sensing, and has become one of the mainstream directions in the development of sensing technology. the

At present, the safety monitoring technical means of high-temperature pressure pipelines mainly include: electrical sensor detection methods, ultrasonic detection methods and infrared thermal imaging detection methods. Since the inside of the high-temperature pressure pipeline is usually a flammable and explosive dangerous medium, any weak electric spark may cause the pipeline to explode, so the electric sensor is not suitable for safety monitoring of the high-temperature pressure pipeline; And infrared thermal imaging detection method, although it avoids the defects of electrical sensors, but the ultrasonic detection method is limited to its working principle and can only detect cracks on the inner wall of the pipeline and bubble defects in materials, etc., and cannot perform online strain monitoring on the surface of high-temperature pressure pipelines; while infrared The thermal imaging detection method has a low resolution and can only detect internal corrosion pits and wall thickness defects, and it is also unable to detect the strain change of the outer wall of the pipeline in real time. the

A large number of data results show that, on the premise of excluding the congenital defects of pipeline manufacturing and human error, the main causes of pipeline leakage and pipe burst accidents are high-temperature creep and pipe wall corrosion of pipeline materials, regardless of the high-temperature creep of pipeline materials Whether it is pipe wall corrosion, its external effects will cause obvious strain on the outer wall of the pipe, which will eventually lead to leakage or burst of the pipe. Based on the theoretical analysis of material mechanics, it can be concluded that the failure strain of the outer wall of the high-temperature pressure pipeline is a nonlinear process, that is, the closer the pipeline is to failure and bursting, the faster the strain rate of the outer wall is. Therefore, by monitoring the failure strain state of the outer wall of the high-temperature pressure pipeline , the safety status of the pipeline can be known, the abnormal strain point of the high-temperature pressure pipeline can be found in advance, and the enterprise can be reminded to repair or replace the high-temperature pressure pipeline in time to ensure the safe operation of the high-temperature pressure pipeline and avoid the occurrence of pipe burst accidents. the

Contents of the invention

In view of the urgency of monitoring the safety status of high-temperature pressure pipelines, the purpose of the present invention is to provide a fiber grating sensor for on-line monitoring of the outer wall strain of high-temperature pressure pipelines, which can monitor the safety of high-temperature pressure pipelines by performing real-time strain monitoring on the outer wall surface of high-temperature pressure pipelines situation. By selecting a suitable high temperature resistant fiber grating, matrix structure and material, the effect of sensitization and temperature compensation of the fiber grating sensor can be realized. the

The invention provides an optical fiber grating sensor for on-line monitoring of strain on the outer wall of a high-temperature pressure pipeline. The optical fiber grating sensor includes a direct sensing arm, a rhombus base, an indirect sensing arm and a high-temperature-resistant optical fiber Bragg grating. the

To achieve the above object, the present invention takes the following technical solutions:

The direct sensing arm, the rhombus base and the indirect sensing arm are integrally rigidly connected, and the direct sensing arm and the indirect sensing arm are located in two perpendicular directions of the rhombus base. the

The material of the direct sensing arm, rhombic base and indirect sensing arm is consistent with that of the high-temperature pressure pipeline. the

In the rhomboid base body, the inner rhombus angle in the direction of the direct sensing arm is less than 90°, so as to achieve the effect of strain sensitization. the

The part where the fiber grating is bonded in the indirect sensing arm is olive-shaped. the

The high temperature resistant fiber Bragg grating is a special fiber Bragg grating coated with polyimide. the

The high temperature resistant fiber Bragg grating is fixed in the olive groove of the indirect sensing arm by low temperature glass solder. the

The melting point of the low-temperature glass solder is 350°C-400°C. the

When the high temperature-resistant fiber Bragg grating is bonded to the indirect sensing arm, it needs to be properly pre-tensioned to ensure that the sensor has bidirectional strain sensing capability. the

The fiber grating sensor for on-line monitoring of strain on the outer wall of a high-temperature pressure pipeline described in the present invention can improve the strain sensitivity of the sensor while resisting a high temperature of 300°C through reasonable selection and design of materials and structures, and is suitable for high-temperature pressure pipelines. The safety status is monitored online, and by connecting multiple monitoring sensors to form a sensor network, while reducing the average cost of the system, it is possible to perform multi-point real-time telemetry on the entire high-temperature pressure pipeline system. the

Description of drawings

Figure 1 is a schematic diagram of a fiber grating sensor for on-line monitoring of the strain on the outer wall of a high-temperature pressure pipeline

Figure 2 is a schematic diagram of the fiber grating sensor processing platform

Figure 3 is a schematic diagram of the specific position of the installed fiber grating sensor relative to the high-temperature pressure pipeline

Detailed ways

An optical fiber grating sensor for on-line monitoring of strain on the outer wall of a high-temperature pressure pipeline according to the present invention comprises a direct sensing arm (11), a diamond-shaped substrate (12), an indirect sensing arm (13) and a high-temperature resistant fiber Bragg grating (14) , wherein the direct sensing arm (11), the diamond-shaped base (12) and the indirect sensing arm (13) are an integrated metal structure, and the direct sensing arm (11) and the indirect sensing arm (13) are located on the rhomboid base (12 ) in two vertical directions; the high temperature resistant fiber Bragg grating (14) is fixed on the indirect sensing arm (13) by low temperature glass solder. the

The material selection of the direct sensing arm (11), the diamond-shaped base (12) and the indirect sensing arm (13) is consistent with the high-temperature pressure pipeline, so as to avoid the thermal stress caused by the difference in thermal expansion coefficient of different materials when the temperature changes, so as to Ensure the monitoring accuracy of the sensor. the

The inner angle of the rhomboid base (12) in the direction of the direct sensing arm is less than 90°. According to relevant theories of structural mechanics, when the pipeline strain remains constant, the smaller the inner angle of the rhombus, the higher the strain amplification factor. In the present invention, the inner angle of the rhombus is 60°, which can be adjusted according to the specific size of the high-temperature pressure pipeline in practice to obtain the best effect. the

By using low-temperature glass solder to bond the high-temperature resistant fiber Bragg grating (14) and the indirect sensing arm (13), the purpose of monitoring component surface strain in a high-temperature environment of 300° C. can be achieved. the

Below in conjunction with accompanying drawing, the example of the present invention is further elaborated:

1. Fabrication of Fiber Bragg Grating Sensors

As shown in Figure 2, a pair of pulleys (21) and the lifting platform (23) are fixed on the operating platform (24), and the metal base structure is placed on the lifting platform (23) to ensure that the metal base structure is stable and placed horizontally;

Install the high temperature resistant fiber Bragg grating (22) between two fixed pulleys (21), and the grating area is just inside the diamond-shaped base (12), and one end of the grating is fixed on the operating platform (24) with a clamp (26). ) side, and a heavy object (25) of appropriate weight is hung on the other end to ensure that the high temperature resistant fiber Bragg grating (22) is in a horizontally tensioned state;

Use the lifting platform (23) to adjust the vertical position of the metal base structure to ensure that the two ends of the gate area are in the olive groove of the rhombus base (12);

Put in an appropriate amount of low-temperature glass solder, and then sinter;

Apply silica gel evenly at the joint between the high temperature resistant fiber Bragg grating and the diamond-shaped substrate to eliminate the stress concentration between the high temperature resistant fiber Bragg grating and the low temperature glass solder, and avoid the grating from breaking due to stress concentration, and then wait for the silica gel to completely cure;

During the whole production process, a spectrometer (27) must be used to monitor the central wavelength of the high-temperature-resistant fiber Bragg grating in real time, so that adjustments can be made in time when there is an abnormal phenomenon. the

2. Fixing of fiber grating sensor

Pre-treatment the pipeline before welding, remove the surface attachments of the high-temperature pressure pipeline, and expose the smooth surface of the pipeline;

The two ends of the direct sensing arm (11) of the fiber grating sensor are welded on the surface of the pipeline. During welding, for each measuring point, a sensor is welded in the axial direction and the circumferential direction respectively, so that the circumferential direction of the surface of the high-temperature pressure pipeline can be monitored at the same time. and axial strain changes to provide comprehensive and reliable strain information, as shown in Figure 3;

After welding, cover the sensor with high-temperature adhesive tape to avoid external physical damage. the

3. Online monitoring

The optical fiber grating sensor welded on the surface of the high-temperature pressure pipeline is connected with an optical cable, and the sensor multiplexing technology is used to form a sensor network to cover the high-temperature pressure pipeline to be monitored. Through the signal demodulation module to analyze the reflected wavelength signal of the sensor carrying the strain information of the high-temperature pressure pipeline, the abnormal strain point of the high-temperature pipeline can be found in advance, and the enterprise can be reminded to repair or replace the high-temperature pressure pipeline in time, so as to avoid leakage or explosion of the high-temperature pressure pipeline Accidents happen. the

Claims (4)

1. the fiber-optic grating sensor of a high temperature pressure pipeline outer wall strain on-line monitoring, it is characterized in that, described fiber-optic grating sensor comprises direct pick-up arm, rhombus matrix, indirect sensing arm and high-temperature resistant optical fiber Bragg grating, wherein direct pick-up arm, rhombus matrix and indirect sensing arm is integrated is rigidly connected, direct pick-up arm and indirect sensing arm are positioned in two vertical direction of rhombus matrix, and the high-temperature resistant optical fiber Bragg grating that coat is polyimide is fixed in the olive groove of indirect sensing arm by low temperature glass solder.

2. the fiber-optic grating sensor of a kind of high temperature pressure pipeline outer wall strain on-line monitoring according to claim 1, is characterized in that, described direct pick-up arm, rhombus matrix and indirect sensing arm, and its material is selected the material consistent with high temperature pressure pipeline.

3. the fiber-optic grating sensor of a kind of high temperature pressure pipeline outer wall strain on-line monitoring according to claim 1, is characterized in that, described rhombus matrix, and in the rhombus of its direct pick-up arm direction, angle is less than 90 °, to play the effect of strain sensitization.

4. the fiber-optic grating sensor of a kind of high temperature pressure pipeline outer wall strain on-line monitoring according to claim 1, is characterized in that, the fusing point of described low temperature glass solder is 350 DEG C～400 DEG C.