Research On Risk Assessment Of Collision Accidents On Tankers

The statistical results show that collision accidents rank higher among ship accidents and are viewed as a critical threat to water transportation safety.Tankers,especially those carrying low flash point liquid cargoes may,compared with other ship types,due to the characteristics of the cargoes carried,ignite and explode when accidental(e.g.collision)leakage occurs,thus endangering the ship structural safety and rendering it difficult for crew to escape.In view of the serious consequences of "SC" and "LQ 1" accidents,each of which resulted in total casualties among the crew,this thesis carries out a risk assessment of collision accidents on tankers.Based on the identification of the main causal factors leading to the collision of tankers and the consequence scenarios with high casualty potential,this paper verifies the effectiveness of the personnel escape route protection measures for providing more escape opportunities for the survivors.In this paper,tanker collision risk assessment method is established using FSA approach as the research framework,and combining BN,ETA and numerical simulation method.Firstly,21 risk factors are extracted from the perspectives of human factor,ship,environment and management,and a table of causal factors of tankers collision is established based on the investigation report of tankers collision in combination with expert evaluation and literature review.Secondly,the BN model and ETA method are used to analyze the causes and consequences of domestic tankers collisions respectively,to identify the main causal factors leading to tankers collisions and the consequence scenarios with high casualty potential,to measure the risk level of tankers collisions,and to propose corresponding risk control measures from both preventive and mitigating perspectives.Thirdly,a questionnaire is designed for expert evaluation and Z-number theory and triangular fuzzy numbers are combined to resolve ambiguity of evaluation results and hesitation of experts.Finally,for the "SC" ship accident with high casualty potential scenario identified by ETA method,numerical simulation is used to restore the fire accident scenario and validate the effectiveness of the proposed measures for personnel escape route protection.BN results demonstrate that negligent look-out,incorrect estimation of collision risks,uncoordinated collision avoidance actions,crew incompetence and adverse weather and sea conditions are among the main causal factors of tankers collision derived from reverse reasoning.Accidents scenario numbered C4.11(i.e.,fire and sinking of a tanker after a collision resulting in cargo leakage)are classified as a scenario with high casualty potential by ETA analysis.In addition,both the risk matrix(accident probability of 2.19E-03,hence RI of4.54)and FN curve methods indicate that the risk level of domestic tankers collision accidents is in the ALARP region,and therefore measures should be taken to reduce the risk to the lowest possible level.From the perspective of mitigating the severity of the consequences,the protection measures for personnel escape routes are proposed.The numerical simulation results show that the temperature of sprinkler No.1 rises sharply to about 170°C at 82 s after the fire,and after activating the water curtain,the temperature is reduced to room temperature by 90 s,which verifies the cooling effect of the water curtain and proves the feasibility of the measure in terms of conceptual design.This thesis implements the causal factor ranking with the help of BN model;identifies the consequence scenarios with high casualties by ETA method;uses Z-number theory to deal with the hesitation of experts and the ambiguity of evaluation information;and verifies the effectiveness of personnel escape route protection measures by using numerical simulation.The results show that the method of this thesis can be used in small-sample ship accident risk assessment scenarios that need to be evaluated by experts,providing a new method and idea for restoring accident scenarios and demonstrating the effectiveness of risk control measures.