A probabilistic methodology for the assessment of safety from dropped loads in offshore engineering

Pipeline damage by dropped objects from crane activities is a significant h azard for offshore platform installations. In this paper a probabilistic me thodology is utilized for the estimation of the pipeline impact and rupture frequencies; this information is obtained both for the overall pipeline se ction exposed to the hazard and for a number of critical locations along th e pipeline route. The presented algorithm has been implemented in a compute r program that allows the analysis of a large number of possible drop point s and pipeline target point locations. This methodology may be used in comm on risk analysis studies for evaluating the risk for platform personnel fro m dropped objects; however, the proposed technique may also be useful for o ther applications where engineering judgment has so far been the main drivi ng criterion. In particular, two sample cases have been analyzed. The first one is the problem of selecting the best approaching route to a platform. By analyzing different route alternatives, a reduction of the impact freque ncy and therefore of the risk for the platform personnel may be achieved. T he second application deals with the selection of the location for a safety valve at the riser base. The analysis may give useful information, such as the highest impact frequency location and the rupture frequencies upstream and downstream of the valve as a function of the valve position; this info rmation, together with the transported medium inventory upstream of the val ve, may give the designer a documented and justifiable rationale for select ing the best location for the valve from a safety point of view.