In this study mechanical strength of A53B carbon steel was analyzed using several types of test specimens directly machined from oil recycling pipe experienced a failure due to hydrogen attack in chemical plants. High temperature hydrogen attack (HTHA) is the damage process of grain boundary facets due to a chemical reaction of carbides with hydrogen, thus forming cavities with high pressure methane gas. Driven by the methane gas pressure, the cavities grow on grain boundaries forming intergranular micro cracks. Microscopic optical examination, tensile test, Charpy impact test, hardness measurement, and small punch (SP) test were performed. Carbon content of the hydrogen attacked specimens was dramatically reduced compared with that of standard specification of A53B. Traces of decarburization and micro-cracks were observed by optical and scanning electron microscopy. Charpy impact energy in hydrogen attacked part of the pipe exhibited very low values due to the decarburization and micro fissure formation by HTHA, on the other hand, data tested from the sound part of the pipe showed high and scattered impact energy. Maximum reaction forces and ductility in SP test were decreased at hydrogen attacked part of the pipe compared with sound part of the pipe. Finite element analyses for SP test were performed to estimate tensile properties for untested part of the pipe in tensile test. And fracture toughness was calculated using an equivalent strain concept with SP test and finite element analysis results.

This study includes a case study among plastic process manufacturing companies, based on which, the currently used 4M method is applied in terms of machine, media, man, and management, to conduct quantitative risk evaluation, and thus to contribute to reducing human and material loss as well as preventing accidents in industrial fields. The result of this study is analyzed based on the 4M-risk assessment to find out the hazardous risk elements, and the quantitative evaluation made it predictable the value of risk(frequency $\times$ intensity) in such classified levels as serious risk, critical risk, and intolerable risk. Further, Among the businesses with hazardous risk elements and high frequency of industrial disaster, risk analysis was conducted for each process, and as a result, 38 cases among 76, including those of serious risk, critical risk, and intolerable risk, were improved, and the risk was reduced. Besides, it is thought that with the engineering approach with 4M-Risk Assessment, the attempt to improve safety level contributes to prevention of accidents.

This study focuses on the trends and issues of improving safety management of elevators in Korea. Frequency and severity of accidents in relation to conditional pass in periodic inspection, maintenance, market surveillance are analyzed based on the statistical data and social cost due to a variety of related fields in managing elevator safety was estimated first. The results of statistical analysis performed in this study will provide logical basis and future direction for improving the safety management system. The role of certification and supervision is particularly addressed to reduce the related accidents and the social cost. The effectiveness of such procedures can be found from the results of simple statistical analysis.

This paper aims at the statistical analysis of electrical fire and classification of electrical fire causes to collect electrical fires data efficiently. Electrical fire statistics are produced to monitor the number and characteristics of fires attended by fire fighters, including the causes and effects of fire so that action can be taken to reduce the human and financial cost of fire. Electrical fires make up the majority of fires in Korea(including nearly 30% of total fires according to recent figures), The incorrect and biased knowledge for electrical fires changed the classification of certain types of fires, from non-electrical to electrical. It is convenient and required to develop the standardized form that makes, in the assessment of the cause of electrical fires, the fire fighters directly ticking the appropriate box on the fire report form or making an assessment of a text description. Therefore, it is highly recommended to develop electrical fire cause classification and electrical fire assessment on the fire statistics in order to categorize and assess electrical fires exactly. In this paper newly developed electrical fire cause classification structure, which is well-defined hierarchical structure so that there are not any relationship or overlap between cause categories, is suggested. Also fire statistics systems of foreign countries are introduced and compared.

An episode of corona is a heterogeneity-caused electric discharge that occurs when electric fields are formed layer on layer and concentrated on an electrode. Electric wires built at the tip of 154kV private facilities use dead end clamp spawns corona from homogeneity caused by field concentration. Corona induces power loss, noise, insulator failure and more. In this research, we've studied the characteristics of coronas that take place in porcelain insulators and terminal electric wires of supporting hard wares (dead end clamp) that are set up as spares in the 154kV private facilities use hydroelectricity installations to support electric wires. Corona, which cannot be identified by regular methods, was measured utilizing UV image camera. As the result of measuring corona via UV image camera, we've confirmed that the depletion of insulators was accelerated following the wire end treatment method and validated the stress intensity of insulators at various lengths of bare wires caused by electric fields via FEMLAB. We have also proposed a new model for relieving homogeneity-caused field concentration, and after analyzing the proposed model via FEMLAB, we've confirmed that the concentration of field distribution was indeed reduced. Such results are exploited in installation of private facilities use equipments, maintenance of insulators and hard wares as well as safety enhancement, and are anticipated to be effectively utilized in corona prevention measures.

For last several decades with the achievement of fast economic development, the electrical fires occupies over 30 percent of total fire incidents almost every year in Korea and not decreased in spite of much times and efforts. Electrical fire cause diagnostics are to confirm a cause for the fire by examination of fire scene. Cause diagnosis methods haven't been systematized yet, because of limits for available information, investigator's biased knowledge, etc. Therefore, in order to assist the investigators and to find out the exact causes of electrical fires, required is research for an electrical fire cause diagnosis system using DB, computer programming and some mathematical tools. The electrical fire cause diagnosis system has two functions of DB and electrical fire cause diagnosis. The cause diagnosis is conducted by a case-based reasoning on a case base and rule-based reasoning on a rule base. For the diagnosis with high reliability, a mixed reasoning approach of a case-based reasoning and fuzzy rule-based reasoning has been adopted. The electrical fire cause diagnosis system proposes the electrical fire causes inferred from the diagnosis processes, and possibility of the causes as well.

In recent days, the accidents have happened at experimental laboratories in universities or institutes. In order to improve safety assurance of workers in laboratories, it is required to carry out systematic study concerned with evaluation of safety and health level. The safety and health inspection checklists were developed and conducted the case study. The case study was carried out laboratory safety inspection with 5 inspectors by the checklists to become aware of safety and health level. From the evaluation results of the inspection, we could be made quantification of laboratory through evaluation of safety and health level in laboratory. It was found that was recognized present states of the laboratory and established a plan for improvements in laboratory safety facilities from the case study. The safety inspection checklists can be used as basic data to establish evaluation criteria of safety and health level.

As railway signaling system is computerized, the significance on safety demonstration and assessment has been increased. Therefore, railway signaling system should reflect the needs for safety assessment technique. Various studies on safety assessment technique for railway signaling have been made in Europe and standardization of the requirements for safety acceptance has been initiated by IEC. In order to develop and establish the safety assessment techniques for railway signaling in Korea, we try to review safety assessment activities for signaling system via reviewing relevant case studies and consulting with experts. And also we propose the safety assessment activity/methodology for Korean railway signaling system.

We introduced the Excavation One Call System (EOCS) as a pilot system, in Seoul, Korea. The system utilizes the phone and internet to transfer information about digging underground and buried gas pipelines, although currently written forms are used in accordance with the City Gas Business Law. After one year, we evaluated the business model by surveying the excavators and the operators of the gas companies. This paper shows that the EOCS was more effective in preventing the buried gas pipelines from being damaged than the existing method that has to use due form. It also shows that the EOCS was more convenient and cost efficient than the present policies in place. We come to the conclusion that the EOCS should be extended nationwide and gradually include other subsurface facilities.