Improving PHA/LOPA by consistent consequence severity estimation

Safety assessment of petrochemical enterprise using the cloud model, PHA–LOPA and the bow-tie model

“…Motivated by the previous studies of the cloud model [ 15 – 17 ], PHA–LOPA [ 31 – 33 ] and the bow-tie model [ 35 – 38 ], these three methods were used for the safety assessment of petrochemical enterprises for the first time. Different from the frequently used quantitative safety assessment methods such as the fuzzy evaluation method [ 6 – 8 ], grey system theory [ 9 – 11 ], set pair analysis [ 12 – 14 ] and neural networks [ 18 – 20 ], the cloud model uses an uncertainty transformation that contains fuzziness and randomness, which is suitable for petrochemical enterprises.…”

“…By taking the effects of the uncertainty transformation of the cloud model into consideration, the evaluation result may be different and skip from one level to another level. We imitated previous studies of PHA–LOPA [ 31 – 33 ] and the bow-tie model [ 35 – 38 ] that were applied in risk analysis. After adopting two independent protection layers, the risk level of shock and noise decreased from 3 to 2.…”

“…The standard cloud model is usually determined by the golden section method [ 41 , 42 ]. Fourth, the quantitative effect of the uncertainty transformation on the assessment result of the cloud model is further analysed, and the dangerous indicator is analysed by PHA–LOPA [ 31 – 33 ] and the bow-tie model [ 35 – 38 ]. Fifth, corresponding safety measures should be adopted to promote the safe production of the petrochemical enterprise.…”

“…However, the cloud model cannot directly supply the control measures, and it should be combined with other safety assessment methods. Preliminary hazard analysis–layer of protection analysis (PHA–LOPA) [ 31 – 33 ] can identify the initiating event that leads to the accident in advance, determine the cause, risk level and consequence, and prevent the accident or reduce the risk level of the initiating event using an independent protection layer. After the critical indicators are identified by the cloud model, PHA–LOPA is suitable for reducing the risk level of critical indicators.…”