Reliability importance analysis of marine technical systems elements

Measures, which can be applicable for reliability importance analysis of components and groups of components in technical systems, have been shown. Selected qualitative measures (order of minimal cut set, numbers of occurrences i-th events in the fault tree, stream measure and Birnbaum's structural importance measure), and quantitative measures (Birnbaum's reliability importance, Vesely-Fussel's measure, The improvement potential reliability measure and Lambert's measure) have been described. Some of mathematical formulas (also approximations) have been pointed out. Estimation of selected importance values of system components (on the basis of complex technical system with multistate reliability and functional structure) has been done. As example system marine power plant system (main power plant sea water cooling system) installed on board offshore multi support vessel has been chosen. Analysis for two different operation i.e. operation during offshore project (operation with dynamic positioning of the vessel) and during sea passage, states has been performed. System for these two states has been modeled with fault tree structures. Particular importance rankings of system components have been shown in bar charts. Some conclusions of applied importance measures have been presented.