Influence of measures of risk prevention and mitigation on the frequencies of rupture of pipework

The paper presents a method for the quantification of the effects of measures of risk prevention or mitigation on the frequencies of rupture of pipework. Some methodologies are given in the literature to this purpose; they however assume that each plant under analysis is characterized by the same combinations of failure causes and prevention mechanisms and this assumption is not always true. The approach suggested in this paper is based on the methodology proposed by I.A.Papazoglou in 1999 for the quantification of the effects of the organizational and managerial factors. Taking advantage of such methodology the objective has been achieved through the definition of the ties between the failure causes that are the origin of incidents and the measures adopted from the company in order to prevent and/or to mitigate them. After the definition of the weights that the single failure causes can have on the incident frequencies and, on the basis of a judgement on the measures of prevention and mitigation adopted, it has been possible to proceed to the modification of the frequencies. The methodology has been applied at the most critical random events, associated to the pipework for a petrochemical plant, which have been brought back in the Safety Report of the establishment. The influence of the measures of risk prevention and mitigation on the failure causes has been discussed and defined according with the plant management