1 Significance of urban buried steel gas pipeline early warning system The urban buried steel gas pipeline early warning system has great practical significance, mainly in three aspects. (1) Provide timely and accurate information for decision-making. The safety of buried urban steel gas pipelines is a matter of great concern to both the public and enterprises. This is determined by the economic, environmental and social attributes of urban gas pipelines. Early warning of urban buried steel gas pipelines can help pipeline management enterprises to keep abreast of changes in the safety situation of buried pipelines, find out the existing problems and improve the direction, and prevent them from happening beforehand, and provide basic information for enterprises and government safety management decisions. , Has important significance. (2) Raise public awareness of participation. The announcement of the buried gas pipeline safety warning can let the public know the real situation of the buried gas pipeline and is another way to educate the public on pipeline safety. Third, it is conducive to strengthening the management of the pipeline system. Early warning of urban buried steel gas pipelines is helpful for pipeline management enterprises to prioritize the situation, and timely control and repair of severely damaged pipelines to reduce the occurrence of accidents; at the same time, it can allocate funds and human resources to ensure pipelines Safe operation of the system and reduce maintenance costs during the overall operation of the pipeline system. Therefore, the development of an early warning system for urban buried steel gas pipelines is of great significance for the safe operation of pipelines and regional safety.
2 The objective of the urban buried steel gas pipeline warning system in order to fundamentally reduce the occurrence of pipeline accidents and reduce the losses caused by accidents, it is necessary to change the defects of the current safety management itself. From the perspective of comprehensive management of the entire system, a set of Methods for monitoring, diagnosing and pre-controlling the causes of pipeline accidents.
The overall goal of the urban buried steel gas pipeline early warning system is to use GIS technology as the core and use visualization technology to build a city buried steel gas pipeline safety information database based on data analysis, calculation, prediction, and evaluation. Establish an early warning model of urban buried steel gas pipelines, realize the pre-control of the space of buried steel gas pipelines, improve the ability of the pipeline system to prevent and avoid dangers, ensure that the pipeline system is in a reliable and controllable state, and manage the pipeline Enterprises provide auxiliary decision support.
3 Urban buried steel gas pipeline early warning system The main purpose of the urban buried steel gas pipeline early warning system is to reveal the early signs of the development of the accident, identify the safe state of the pipeline, and use this to make judgments and issue warnings in advance. Control strategies provide a basis for decision-making. The system includes four stages: detection, identification, diagnosis and processing.
3.1 Inspection Inspection is the premise of safety early warning, and the object of monitoring is the factor that directly affects the safety of the pipeline. There are two tasks for monitoring: one is organization testing, that is, testing related parameters of pipeline early warning (data of pipeline corrosion damage) to obtain real values; second, processing monitoring information. That is, by sorting, analyzing, and storing historical data of pipeline corrosion and real-time detection data, a gas pipeline early warning management information file is established, and the detection information is promptly and accurately input to the next early warning link.
3.2 Identification Through analysis of the monitoring information, the current safe state of the buried steel gas pipeline can be determined. That is, identify which stage is in a safe state, a quasi-safe state, a near-accident state (low-crisis state) or an accident state (crisis state). Identifying the development stage of an accident is a key link in the safety early warning system of buried steel gas pipelines. It provides a detailed and reliable quantitative basis for accident diagnosis.
3.3 Diagnosis Analyze the cause process and predict the development trend of the unsafe state (including near accident state and accident state) of the identified pipeline to clarify which accidents are the main ones and which are subordinate and incidental. The main task of accident diagnosis is to distinguish the major and minor accidents, and to accurately and quantitatively describe the background, development process and possible development trends of the major accidents.
3.4 Disposal The pipeline that has been confirmed to be in a dangerous state shall be repaired and rectified accordingly, and it shall be clarified what kind of damage the pipeline will suffer in this dangerous state. For example, when the maximum corrosion pit depth of the pipeline corrosion damage exceeds 80% of the pipeline wall thickness, this section of pipeline will most likely have a leakage accident caused by corrosion perforation. Clarify the potential accidents that may occur in this section of the pipeline, so as to determine the repair work and further work arrangements of the pipeline, so that the pipeline risk is always in a controllable state to ensure the safe operation of the pipeline.
4. Urban early warning system for buried steel gas pipelines The construction of pipeline risk early warning system is mainly to conduct risk analysis and implement risk early warning for the factors that induce main pipeline accidents.
4.1 Urban buried steel gas pipeline early warning system The logical process of forming a complete urban buried steel gas pipeline early warning system should include the following five parts.
4.1.1 Collection of early warning information The collection of early warning information refers to collecting and obtaining relevant information from relevant channels and preprocessing the information. In this link, it is important to ensure the authenticity, accuracy, effectiveness, and timeliness of the warning information.
The collection of early warning information generally adopts on-site testing, consulting completion data, etc. Establish a fixed database for early warning information collection to accurately grasp possible dangers. Such as the maximum corrosion pit depth of the pipeline, the corrosion rate, the use time of the pipeline, and the risk value of the pipeline after the risk assessment. These indicators can objectively reflect the size of the pipeline's dangerous situation. Through the detection and monitoring of these indicators, early detection, early diagnosis and early treatment of the pipeline's dangerous situation can be achieved.
4.1.2 Early warning analysis Early warning analysis is to analyze the early warning information collected and judge the early warning level, and lay the foundation for the subsequent rapid response subsystem. After grasping the potential danger state and development trend, immediately analyze and comprehensively judge the early warning information to determine the danger (continued from page 363) National “Eleventh Five-Year†Technology Support Plan Project: Urban Municipal Pipeline Network Planning, Construction and Operation Research and demonstration of key management technologies (2006BA16B08) Yuan Jinbiao (1974-), male, Liaoning, Ph.D., mainly engaged in the management of urban gas pipeline network.
The structural formula of ofloxacin is in solution. -NH2 of the chitosan molecule reacts with -CHO of glutaraldehyde to form a Schiff base, which cross-links the chitosan to form a gel. Tests have shown that increasing the ratio of glutaraldehyde to chitosan can increase the strength of the gel. As can be seen from the figure, the entire release behavior can be divided into two stages of rapid release and slow release. At the beginning of 5h, the release rate of Ofloxacin reached about 70 °%, and during the release process after that, the release rate almost stabilized. Studies have shown that in the early stages of the interpretation of Offangxin, Ofloxacin's release was mainly molecular diffusion. The rapid release of Ofloxacin may be caused by the rapid release of Ofloxacin in the outer layer of the gel, or it may be caused by the larger pore size of the gel. Subsequently, the release of Ofloxacin entered the slow release phase, but a small amount of Ofloxacin molecules remained in the gel, which may be caused by the interaction of Ofloxacin and the remaining amino groups on chitosan. It can also be seen that different pH has an effect on the release of Ofloxacin, because the pH has a great influence on the swelling degree and swelling rate of the gel. In an acidic solution with pH = 5.0, the gel swells rapidly, and small drug molecules quickly diffuse out of the gel network. In the slow release stage, the amount of drug released in the solution with pH = 5.0 is larger than that with pH = 7.4.
3 Conclusion Using glutaraldehyde as the cross-linking agent, the model drug ofloxacin was selected to prepare the chitosan-loaded hydrogel, and the controlled release performance of the gel on the drug was investigated. The drug-loaded gel releases rapidly within 5 hours in the buffer solution, and the release gradually slows down over time, and the drug can be continuously released to more than 24 hours. pH has an effect on the release of Ofloxacin, because pH has a great influence on the swelling degree and swelling rate of the gel. In the slow release stage, the amount of drug released in the solution with pH = 5.0 is larger than that with pH = 7.4.
Time / h release curve of drug-loaded gel at different pH
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