| The petroleum chemical industry occupies an important position in the national economy. However, the security problems of petrochemical industry is prominent, especially the equipment aging, improper management have become the major causes of safety accident. With the progress of science and technology,petrochemical equipments are becoming larger, automatable and intelligent and the changes of equipment status exhibit the characteristics such as time-varying, multi-dimensional, and coupling,which makes the equipment monitoring more difficult, and puts forward higher requirements to equipment’s managers.Therefore, it is necessary for petrochemical equipment to implement state monitoring and maintenance management.The fundation of equipment state maintenance is real-time, on-line dynamic monitoring. Conventional electro-magnetic sensing detection technology can meet certain requirement of application, but for inflammable and explosive, easily leakable and dangerous petrochemical occasion, its application is greatly limited. Fiber grating sensing technology has many advantages such as intrinsic safety, electromagnetic interference resistance, high temperature resistance, high pressure, easy multiplexing, remote distance signal transmission, therefore, it can provide a new method and idea for safety monitoring of petrochemical equipment. According to dynamic monitoring for mechanical equipment, although some relevant research has been carried out by some institutions or individuals, there are little available products, product performance is poor, and can not meet the demand for monitoring. Based on the above background, the research work of this paper will be innovative and has practical value that is to carry out the dynamic sensing and monitoring method for petrochemical equipment based on fiber Bragg grating(FBG),so it has important significance.The research on dynamic sensing and monitoring technology based on FBG for petrochemical equipment is an interdisciplinary and comprehensive research topic. Therefore, in this paper, with FBG dinamic technology as the object and dynamic monitoring system integration and application as the goal, from a multidisciplinary perspective, using the theory, experiment and field test means, the author has carried out a comprehensive, systematic, and in-depth studies on fiber Bragg grating fabrication and packaging, fiber grating sensor and signal detection, and integration and application of dynamic monitoring system. The main research contents and conclusions are as follows:(1) The methods on fabrication and packaging of fiber grating sensing material were studied. Mechanical properties of optical fiber and characteristic parameters of sensing gratings were analyzed. Preparation technology and package process for good-performance fiber grating were studied from the aspects of improving photosensitive and stability, controling main feature parameters. Two kinds of packaging technology for fiber grating were studied. Separately from the packaging material selection, sticky process, sensor package structure, theoretical and experimental research have been done on the adhesion type packaging process; Separately from the aspects of pretreatment, surface metallization, metal packaging,the metal encapsulation process is studied; The long-term reliability of FBG sensors encapsulated by two kinds of process has been tested through aging and fatigue resistance experiments and the results show that two kinds of sensors both have good stability, and meet the requirement for long-term reliability of engineering application.(2) Dynamic sensing and detection methods based on fiber grating were studied. In this thesis, the present status of fiber grating dynamic signal demodulation technology was analyzed and existing problems were studied. According to low accuracy of edge filter demodulation, the author has put forward respectively the differential detection method for FBG with intensity compensation and the one for CFBG based on ratio of light intensity, and the tests have verified the feasibilities of them. According to the shortage of the existing method for detecting ability, the author has put forward a new method of demodulation based on wavelength division multiplexing. After analysis of the design theory and principle of dynamic sensor, two kinds of fiber grating dynamic measurement sensor have been developed. First, according to the characteristics of large vibration amplitude and high-frequency response of high-speed rotating machinery, a type of chirped fiber Bgagg grating(CFBG) vibration sensor with push-pull structure is designed; using double chirped grating matching demodulation method, the influence of temperature was eliminated, and the measurement range was improved; These test results show that the natural frequency of the sensor is 3232 Hz, the working frequency is about 10-1000 Hz, the largest measuring acceleration is 4g, the sensitivity is about 66 mv/ ms-2, transverse interference coefficient is 6.6%, the repeatability error is less than 5%. Second, to meet the need for pump condition monitoring, an integrated sensor has been developed, which has the measurement functions of three-dimensional vibration and temperature. The experimentally measured 3D frequency range sensor are within 10-500 Hz, acceleration measurement range is in the 0.1- 1.0g, linear sensitivity is about 70mv/ ms-2, crosstalk coefficient is larger than 22 dB, The maximum error in the measurement of acceleration space is 4.8%, the temperature change does not affect the dynamic performance of the sensor, the sensitivity of the temperature sensor is 24pm/ deg. C.(3) The design and integration methods of dynamic sensing and monitoring system based on FBG for mechanical equipment was studied. Firstly, the work characteristics and monitoring requirements of mechanical(petrochemical) machines were analyzed, and the basic framework and function module of the system were designed. Secondly, these methods were studied,which were respectively state monitoring method based on fiber grating for mechanical equipment(with the bearing and the rotor as an example),dynamic signal analysis,fault diagnosis method and integration methods of dynamic monitoring system. At last, the anthor has been done some simulation experiments about the faults of mechanical equipment. The integrated system has been tested and the results show the system can better accomplish various testing tasks, the test results can be essentially in agreement with related theory analysis. Therefore, these experiments have verified the application feasibility of the integrated system.(4) Relying on the scientific research project, the fiber grating sensing technology is applied to state monitoring of petrochemical equipment, respectively, with pump, compressor unit and pump group as the object to the application test. First, the vibration situation of bearing seat, the impeller and the anchor bolt of water pump in a petrochemical factory were detected online, according to the collected data of before and after pump failed, an accurate diagnosis has been made about type and location of the fault; Second, a long-term and online monitoring is carried out for monitoring the temperature of the valve and vibration of the cylinder of reciprocating compressor in a petrochemical plant. Through the contrast test of various detecting methods, the feasibility of monitoring method based on optical fiber grating is vetified. Third, a long-term and online monitoring has been carried out for thermal radiation machine pump cluster of petrochemical plant. An on-line monitoring system for vibration and temperature of pump groups based on FBG has benn constructed and the data when a pump bearing goes wrong has been collected.The results from data analysis and diagnosis are in accord with the one from inspection after disassembly. These test results haved verified the feasibility and superiority of the application of the FBG dynamic monitoring system in petrochemical equipment. |
PDF Full Text Request