Allocation of Individual Risk Criteria under LOPA Framework

The oil and gas industry in China has deployed risk management technologies for many years, including Layer Of Protection Analysis (LOPA), Alarm System Management (ASM) and Safety Instrumented System (SIS). These technologies, as well as their resulting risk treatments, consolidate the elements of the PSM system. However, to make the risk evaluation and following treatment possible, the determined scenario will be compared to some specified Risk Tolerable Criteria (RTC) in the risk management process of all of these technologies. By using the individual RTC mandated by Chinese Regulation Code No. 40 of the State Administration of Work Safety (SAWS) of China as a starting point, a new and structural procedure to develop Scenario oriented Individual RTC (SIRTC) is proposed. This procedure firstly decomposes the total RTC of a facility into specified process unit, and then continues onto a specified scenario level with the conception of residual risk under the LOPA framework. In this manner, it can avoid the common mismatch in risk comparison, as well as the inconsistency caused by empirical apportioning methods. The case study of a natural gas compression station is provided to illustrate the proposed approach and concerned numerical results are presented.