This paper analyses the effect of parameters on the consequences of the unconfined vapor cloud explosion accident (UVCE) by the release of heavy gas (xylene vapor). Simulation results showed that the overpresure was increased with the increase of the release hole diameter and with the decrease of the interested distance and the wind speed. While, the overpresure was not nearly affected by the release height, weather and environmental conditions. From the results of the consequence analysis and analysis of affecting the consequences of UVCE, the emergency plan should be established taking into account these parameters.

현행 우리나라의 검사제도는 사업장의 자율관리 능력을 고려하지 않고, 설비의 노후화 및 위험도와 무관하게 획일화된 방식으로 적용하여 설비의 안전성을 확보하지 못할 뿐만 아니라 정기 및 자체 검사를 병행하여 많은 불편이 있다. 따라서 사업장의 불편을 해소하고, 설비의 안전성과 신뢰도를 높일 수 있는 위험기반검사(risk based inspection, RBI)를 국내 실정에 적합하게 도입하기 위하여 사업장, 정부 및 관련 기관에서 향후 추진해야할 방향에 대하여 분석하였다. 국내에서 위험기반검사 제도가 정착될 수 있기 위해서는 먼저 법적 근거가 마련되어야 하며, 법적 제도가 마련되면 사업장에서 RBI를 적용 시 이를 검증하고, 관리할 수 있는 인증기구의 설치가 필요하다. 또한 위험기반검사를 수행하는 사업장에 대해서는 공정안전이행수준과 같은 위험기반검사 이행수준평가를 도입하고, 차등 적용하여 사업장을 관리하는 것이 바람직하다.

The likelihood of failure for the stress corrosion cracking (SCC) of caustic cracking, which affect to a risk of facilities, was analyzed through the risk based-inspection using API-581 BRD. We found that SCC of the caustic cracking was occurred above 5 % NaOH concentration, and the technical module subfactor (TMSF) was maximized for above 50 % concentration. The heat traced and monitoring were not sensitive to the TMSF with NaOH concentration and temperature. But the steam out was more of less affect minimum value of the TMSF. Also, the inspection number, the inspection effectiveness, and the year since inspection were very sensitive to the TMSF with NaOH concentration and temperature. Therefore, the plan of next inspection will be established with compositively considering those at once.

The effect of parameters on the consequence of the flash fire accident by the release of heavy gas(in this study, xylene vapor) was analyzed. Simulation results showed that the distance with the lower flammable limit(XLFL) was increased with the increase of the release hole diameter. For the case of the elevated release, XLFL was increased with the increase of the wind speed and the release height, but XLFL was not affected by the wind speed for the release on the ground level. Therefore, the accident in the elevated release was more dangerous than the release on the ground level. In this condition, the release height had more effect on XLFL at the night time than the daytime and in the urban area than the rural area.

The quantitative evaluation method of the safety management cost was suggested to prevent a gas accident as a major industrial accident. In a gas governor station, process risk assessments such as the fault tree analysis(FTA) and the consequence analysis were performed. Based on process risk assessments, potential accident costs were estimated and the cost-benefit analysis(CBA) was performed. From the cost-benefit analysis for five classification items of safety management cost, the order of the cost/benefit ratio was estimated.

Cost-benefit analysis was investigated to propose the analysis method of the effect of investment and the optimum investment level of safety management cost for preventing gas accident in the B governor station. From five classifications of safety management costs consisting of cost items with similar characters and potential accident costs calculated by risk assessments(FMEA/HAZOP), we found that the order of the benefit(the reduction cost of the potential accident cost) was the instrument increase and repair cost > the safety checking and inspection cost > the labor and training cost > the safety equipment and corresponding cost > the research and development cost. As the benefit was increased with increasing the investment cost, the effect of investment was increased with decreasing the Investment cost. As a result, the optimum safety management cost was estimated and the investment level was analyzed by the model of optimum investment level.