عنوان مقاله [English]
Today, gas industries mainly include extraction, processing, transmission and consumption. After extraction, natural gas is directed to the gas treatment unit by the collection network. Gas pressure drop is done in gas pressure reduction stations, so pressure reduction station, feeding network and gas distribution network play an important role as process units of gas supply companies. The use of risk assessment techniques in this area to identify high risk cases will allow optimal control of the system. The analysis of major accidents in these stations shows that a large part of the damage and damages of the accidents and the possibility of their occurrence are not only preventable but also predictable, of course, if measures such as identifying the root causes and final consequences and controlling them are carried out in time. Analysis and risk studies are one of the most necessary steps to increase the level of safety in these stations. The complexity and expansion of chemical and process industries lead to high safety risks and disasters in the world. Some of these tragic events are Fizin, Mexico City, Bhopal (India), Piper Alpha (UK), liquid fuel explosion (North Sea) or Chernobyl (Russia). Transportation of hazardous materials is a major source of hazards that threaten many industries as well as the public. These networks of hazardous material transmission lines are distributed among many industries and their customers, including the general population. Although the transportation of hazardous materials by pipelines seems safe, it still involves safety issues. Although the frequency of pipeline accidents is low, their high potential for consequences can affect the low frequency. Accident databases show that pipelines carrying hazardous materials are just as dangerous as refinery facilities. Pipeline industry It has experienced at least 8 major explosions and more than 55 deaths in 2014 alone. Pipelines are placed in areas that are not normally controlled. In addition, pipelines passing through high-risk areas such as congested areas make the situation even more dangerous. Therefore, high potential consequences, lack of control and passing through high-risk areas have made pipelines a serious source of destructive risks. Risk management should be measured according to the organization's policy and risk evaluation approved by the senior management and carried out through the method approved by the organization. According to the process safety management system, it is suggested to identify and evaluate process risks in the stages of installation, pre-commissioning, commissioning and operation, and in case of making any changes in the process, technology and equipment, document the changes in order to prevent the risks. Prepared from the changes. Some of the risks caused by changes are very small and have no harmful effects, so some others leave harmful effects and irreparable damages, for which it is necessary to take the necessary measures. By comparing the scenarios of accidents in different countries without considering their development status, it shows the existence of some common factors between the accidents that took place. The analysis of these incidents has factors such as human error, too much trust in equipment, design problems in operational units and lack of safety, health and environment units. The most important factor in system safety and risk management is the identification and reduction of risk potentials. In order to successfully control and control the risks, you must have a proper understanding of the risks and how to deal with them and how to identify them. In recent years, the lack of safety has become one of the most important issues and problems in the design and operation of operational units. First, due to the complexity of most processes in modern operating units, there are fundamental changes in control strategies and numerous improvements in process capabilities, all of which lead to an increase in operational problems, and second, due to the accidents that we witness every year around the world and cause loss of life, problems Environmental and loss are produced. It is possible to improve the safety of operational units in the stages of design and operation, if the necessary attention is paid to the analysis and identification of process risks. Risk of injury is the risk that occurs to specific individuals or groups exposed to it in any system or process. Accident analysis points to various factors, including human errors, over-reliance on machine safety, plant design problems, lack of preparation to face and deal with critical situations, and non-compliance with HSE rules.
The method used in this research is evaluation-analytical. In the current research, in order to compile the theoretical literature, the background of the research and to identify some research criteria, reliable books and researches conducted inside and outside the country, such as reliable domestic and foreign magazines and articles related to the research topic, were used. Some of the domestic publications used can be referred to as articles indexed in Elsevier scientific database, domestic research journals, and Sulica scientific database. By using the fuzzy-Delphi approach, by preparing a questionnaire and interviewing experts, these factors were screened and reduced to the main factors, and at the end, another questionnaire was prepared for pairwise comparisons of the identified factors, whose values were analyzed using the HAZOP method, and the influencing factors. and were identified as effective. HAZOP is a qualitative, systematic, creative and group method that is very easy to learn and is an effective way to identify hazards and system performance problems by determining their effects. The implementation of HAZOP is as follows:
1. Knowledge and general understanding of the system
2. Dividing the system into functional nodes
3. Identify deviations in each node using the keyword
4. Determine the main keywords: pressure, temperature, flow, etc
5. Use of secondary keywords: not, more than, less than, as well as etc
6. Estimating the probability and consequences of deviations
7. Determining the risk level of risks using the risk matrix
8. Define controls to reduce risks
To perform the HAZOP method, a team of specialists who have sufficient knowledge of the conditions and risks of the gas station must first be formed. The first step is to fully understand the system and process of the gas station, what equipment the station includes, with what features and functions. In the next step, this system is divided into nodes based on the function of each equipment. These nodes include scrubber filter, separator filter, dry filter, regulator and safety valve. After identifying the deviations in each of the nodes, the risks of each node are determined using the main keywords and secondary keywords. Using the severity of incidents in Table No. 1, the probability of incidents in Table No. 2 of the risk matrix is determined according to Table No. 3. Finally, based on the level of risk and risks of deviations in each of the nodes, controls have been recommended.
Out of 12 identified risks, 9 risks were in the acceptable risk group and 3 risks were in the undesirable risk group. This result indicates the favorable situation for the existing protections of Bampur gas station. The risk number of 8 for 2 deviations of separator filter and dry filter nodes is due to the structure of these two nodes, which has a filter valve in addition to the flange. Despite the favorable conditions of the station, due to the harmful consequences of deviations, all safety requirements must be met, therefore, safety recommendations including periodic inspection, personnel training, and timely replacement of gaskets and fasteners have been emphasized. From similar researches, we can refer to the research of Donjo and his colleagues in 2010. This article is entitled to collect the literature related to the HAZOP method. In this research, Donjo collected the literature related to the HAZOP method from books, guidelines, standards, large magazines and conferences with the purpose of classification and conducted research over the years to use this method. In the industries discussed, the method and results of the current research are somewhat in line with the reviewed article. In another research in the field, Alfredo improved the conventional HAZOP analysis through the fuzzy multi-attribute HAZOP technique. The results of the research indicate the identification of critical risks in the subsystem, which showed the sensitivity analysis of the reliability and strength of the final rating. The results of this analysis support preventive maintenance by identifying critical monitored points when scaling up biological biogas upgrading processes, which the results of Donjo's research partially overlap with the results obtained in the present study.