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The frontiers of science and education
35 of 2008
Summary of leak detection and location technology of oil pipeline
Zhu Xi 'an University of Science and Technology West Road, Shaanxi 7 10054)
The leakage of oil pipeline will not only cause huge economic losses, but also bring great danger and cause serious pollution to the environment. In this regard, this paper systematically introduces the detection and positioning technologies of F and II oil pipelines in China in recent years, and compares the advantages and disadvantages of various methods. Oil pipeline; Wool; Leak; Detection; location
It is said that pipeline transportation has the characteristics of smooth and continuous, good safety, large transportation volume, easy quality assurance, small material loss, small floor space and low transportation quality, and has become the first choice for oil transportation. However, the aging of pipelines due to the increase of service time, or the corrosion and man-made destruction of various media will cause pipeline leakage, which will seriously threaten the safety of oil pipelines and surrounding natural environment and bring immeasurable economic losses. At present, there are many methods to detect and locate oil pipeline leakage at home and abroad, including hardware-based detection methods, such as manual pipeline detection, "pipeline pig" and acoustic emission technology. Detection methods based on soft parts, such as negative pressure wave method and pressure gradient method.
Strong timeliness and accurate location of leakage points. However, the propagation distance of acoustic emission signal in oil pipeline is extremely limited, which is not conducive to long-distance detection. There are many methods based on hardware detection. For example, in-pipe intelligent crawling system (namely "pipeline pig"), light detection, cable detection and GPS detection.
3. Software detection method
Software detection method refers to the real-time collection of pipeline flow, pressure, temperature and other data according to computer data acquisition system (such as SCADA system), and the detection and location of leakage through calculation by using the principles of flow or pressure change, material or momentum balance, system dynamic model, pressure gradient and so on. 3. 1 negative pressure wave detection method When a pipeline suddenly leaks, a decompression wave will be generated from the leakage position to the upstream or downstream of the pipeline, which is called negative pressure wave. Pressure sensors are arranged at both ends of the pipeline, and when the sensors detect negative pressure waves. The leakage can be cut off and located. The key problem of applying negative pressure transit detection method is how to distinguish negative pressure waves caused by normal operation and leakage. The negative pressure wave detection method is sensitive and accurate. Large leaks can be detected quickly, but for relatively small leaks or leaks that have already occurred, the impact of /fi is obvious. 3 13.2 pressure gradient method When crude oil flows smoothly in the oil pipeline, the pressure changes linearly along the pipeline, that is, the pressure is distributed in an oblique straight line. Two pressure sensors are arranged upstream and downstream of the pipeline respectively, and the pressure gradient of the pipeline can be calculated through the pressure signals of the upstream and downstream. When the pipeline leaks, the flow before the leakage point becomes larger and the pressure gradient becomes steeper; The flow after the leakage point becomes smaller, the pressure gradient becomes flat, and its inflection point is the leakage point. From this, the location of the leakage point can be calculated. In actual operation, because the pressure gradient along the pipeline is nonlinear, the positioning accuracy of the pressure gradient method is poor, and the measuring accuracy and installation position of the instrument have great influence on the positioning results. 3.3 wavelet analysis wavelet analysis is a new mathematical theory and method developed in the mid-1980 s and a good time-frequency analysis tool. Wavelet analysis can be used to detect signal mutation, remove speech, extract system waveform features, and extract fault features for fault classification and identification. Therefore, wavelet transform can be used to detect the pressure drop point caused by leakage and denoise it, so as to detect leakage and improve the detection accuracy. The advantage of wavelet transform method is that it does not need the mathematical model of pipeline. The requirement for input signal is low, and the calculation amount is not large, so it can be used for online real-time leak detection. The ability to overcome noise is strong, but this method is difficult to identify the sudden pressure drop caused by working condition change and leakage, and it is easy to produce false alarms. 3.4 transient model method transient model method is to establish a mathematical model of fluid flow in the pipeline and solve the flow field in the pipeline under certain boundary conditions. Then compare the calculated value with the measured value at the pipe end. When the deviation between the measured value and the calculated value is greater than a certain range, it is considered that leakage has occurred. Use a steady-state model at the leak location. According to the change of pressure gradient in the pipeline, the location of the leakage point can be determined. The alarm threshold of transient model method is closely related to measuring instrument error, flow model error, numerical method error and required alarm time. If a small threshold is used to detect a small leak. Then the uncertainty caused by the above reasons will produce more false positives; If a lower false alarm rate is required, the minimum leak that can be detected will inevitably become larger. High false positive rate is a big defect of transient model method in practical application. Software-based detection methods also include pressure point analysis, flow balance, statistical detection and so on.
1. Performance evaluation of oil pipeline leakage detection and location
Pipeline leakage detection and location technology can timely and accurately report leakage accidents, and minimize economic losses, environmental pollution and greater dangers. The evaluation of a leak detection method should be based on the following criteria: (1) leak detection sensitivity: refers to the detection ability of the leak detection system for tiny leak signals. (2) Timely leak detection: It means that the detection system detects the slurry leakage force in the shortest time. (3) False alarm rate of leakage: False alarm rate refers to the probability that the system is misjudged as leaking without leakage. (4) Leak miss rate: The miss rate refers to the probability that the system leaks but is not detected. (5) Distinguishing ability between normal working conditions and emission intensity: it refers to the ability to distinguish normal start, pump stop, valve adjustment, tank dumping and pipeline leakage. The stronger the distinguishing ability, the lower the false alarm rate. (6) Leakage identification accuracy: refers to the estimation accuracy of leakage size and its time-varying characteristics by the leakage detection system. Accurate estimation of leakage time variability. Not only can the degree of leakage be determined. It can also predict the aging and corrosion of pipelines and give reasonable treatment methods. (7) Robustness: refers to the ability of the leak diagnosis system to correctly complete the leak diagnosis task in the presence of noise, interference and modeling errors. At the same time, ensure satisfactory false positive rate and false negative rate. The stronger the robustness of the diagnosis system, the higher the reliability. (8) Adaptability: It means that the diagnosis system has adaptability to the changing diagnosis object and can make full use of the new information generated by the change to improve itself.
2. Hardware detection method
Hardware-based methods refer to hardware devices designed by different physical principles, such as infrared temperature sensors based on vision, ultrasonic sensors based on hearing, carbon and oxygen detection devices based on smell, etc. , carried or laid on the pipeline, used to detect pipeline leakage and locate. FLJ 2. 1 Manual inspection refers to inspection along the oil pipeline by experienced pipeline workers, or by helicopter or other aircraft carrying high-precision inspection equipment, and judging whether the pipeline leaks by monitoring and analyzing the changing environment around the pipeline. Obviously, this method has poor continuity and real-time performance, and the cost is high. 2.2 Acoustic emission technology When a pipeline leaks, fluid is ejected through cracks or corrosion holes to form a sound source. Then through the interaction with the pipeline, the sound source radiates energy to form sound waves, which is the acoustic emission phenomenon of pipeline leakage. Leakage acoustic emission signal is generated by liquid leakage excitation. It is a continuous acoustic emission signal, which propagates in the pipeline and can reflect some characteristics of the structure. Such as the position and size of the hole, and it has great randomness and uncertainty at the same time, which belongs to non-stationary interlocking signal. profit
4. Conclusion
Through the above discussion and comparison. Combining the analysis of several main standards to measure the advantages and disadvantages of pipeline waterfall detection methods, many detection methods have problems to be solved, such as the same small slag dew detection and positioning problem. Detection and location of pipelines with multiple leakage points, etc. However, there is no F-down code that can simply use any technology to detect and locate the leakage of oil pipelines.
Acoustic emission signals are captured and analyzed by test instruments. You can know whether it happened in the pipeline or not.
Break it until it becomes clear. The advantages of acoustic emission technology are that it is dynamic and practical.
Wanfang Data
OIT technical forum o
Day 35, 2008
Research and Analysis of University Computer Room Management System Based on Task Sharing Mode
Yin Cheng Zhang Law (Jiujiang Vocational College, Jiujiang, Jiangxi 3320000J
The computer room of Yao Yao school should not only meet the needs of school teaching management, but also meet the needs of students searching information and other applications online in their spare time. The traditional computer room management system adopts C/S mode, which has many limitations in practical application. The improved computer room management system changes the S in the traditional CIS to S and S in structure, that is, the functions in the original model big S are allocated to the corresponding main server S and sub-server S, so as to realize task sharing, which not only solves the problem of server overload in the original C/S. It also solves the problems of the network with the increase of the number of terminals.
Busy phenomenon. Keywords client/server mode; Task sharing; C/s/S/s mode; wol,wake on lan
First, improve the necessity of computer room management system in colleges and universities
The computer room of the school should not only meet the needs of the school's teaching management, but also meet the needs of students surfing the Internet for information and other applications in their spare time. As a set of computer room management software, it must have the following functions: before class, teachers can make an appointment for class, and during normal class hours, teachers can use management software to check the status of equipment and the attendance of students, and students can't charge for using computers; After class, the school can charge students a certain service fee. However, in the practical application process, at present, many schools use credit card. In this way, students need personnel supervision when they get on the computer, but they still need personnel supervision when they get off the computer. If the hardware solution is adopted, it will increase the equipment cost and maintenance cost. At the same time, with the expansion of the school scale and the increase of the number of students in the school, the number of computers in the computer room is also increasing, and the number of computer users is also increasing. Moreover, many schools have multi-campus phenomenon, which leads to the scattered distribution of equipment. If you swipe your card in this way. It will inevitably increase the workload of workers. In order to ensure the efficiency of equipment management, the unity of centralized management, the flexibility of using computers in spare time, and reduce the workload of staff, from the application point of view, an effective software is needed for management control. Technically speaking, many computer room management softwares now adopt the mode of C and S, that is, client and server. In this mode, when there are too many clients and a large amount of data increases, the server will be overloaded and the server will crash seriously. At the same time, the network data traffic will increase obviously, which will increase the network burden. In order to avoid this situation, it needs to be improved technically, which provides technical requirements for the task sharing model. diligent
(2) Main Server S Function The main server S mainly realizes data distribution, data reception of various services, management of various servers, and teacher's class appointment. Its basic function is shown on the right. (3) Functions of the secondary server The secondary server mainly realizes the data sending and receiving of the primary server, the control and management of the client, and the realization of charging. The main functions are shown on the right: The functions of the computer room management system in colleges and universities under the task sharing mode are as follows:
The functions of university computer room management system based on task sharing mode are as follows: (1) It can realize data transmission and control across networks, and realize the unity of computer room management. (2) Teachers can use this software to make an appointment to get on the computer, check the status of equipment in the computer room and take exams for students. (3) Automatic billing management to realize unattended billing. (4) Use the server wake-up technology, and do not start the server program. The client program interface does not appear, and the computer charging in the open computer room does not affect the normal teaching and work use. . One machine has multiple functions, which meets the needs of the school to open the computer room to the outside world. (5) The server program is separated from the charging and recharging program, which is convenient for control and management. There is no cash transaction on the computer, which increases the transparency of charging and expense management. (6) The client automatically displays the computer time, which is convenient for users to understand and master the computer time. (7) Automatically check the account balance. Prevent overdraft and insufficient balance, remind in advance and count down. (8) Support multiple administrators, with division of functions and mutual constraints.
Second, the realization of task sharing mode
The traditional C/S mode has many limitations in practical application. The improved computer room management system changes the structure of S in traditional C and S to S and S, that is, the functions in the original model S are allocated to the corresponding main server S and sub-server S, which realizes task sharing, solves the problem of server overload in the original C and S, and also solves the phenomenon that the network is too busy with the increase of the number of terminals. Its structure and function are divided as follows. (1) Topological structure design: The topological structure is shown in the right figure. This structure changes the C/S mode, and turns S into a server 8 and a main server S, that is, C S, S. Most data of each client can be processed in the local server S, thus sharing tasks with the main server S. At the same time, the data traffic in the network will be greatly reduced, reducing the burden on the network and realizing task sharing. Where the primary server is S and the secondary server is S.
Improving the management efficiency of computer room is very positive for school management.
Meaning of. bang
refer to
[1 Wang Jingbin. Development of computer room charge management system software. Computer development and application. 2002, (3).
The realization of university computer room management system based on task sharing mode will certainly benefit universities.
(2 Sui Dan. Design Agent implementation of agent-based distributed computer room management system D 1. East China Normal University ... 2007,
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[3] Yin Cheng: Jiujiang Vocational University.
I. Lei Jian Wu Liang
Oral customer support
Responsibility condensed edition: Tian Rui stack
J method has achieved satisfactory results. Only by using a variety of technologies comprehensively. Only when
[3J Kang Xiaoqin et al. Clarification, detection and positioning system of sugar casing pipeline based on negative pressure coating method. Computational hunger engineering and design.
20 Xin, 0.5: 2199-2202.
It can successfully detect and locate the leakage of oil pipeline. ● Three