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IntroductionIn the report of the Committee of Union Gas in the World Congress in Nice in 1972, the issue connected with the failure intensity of the gas network was presented. Operation of Gas Supply System is inseparably linked with the occurrence of the fire and explosion risk. Failures, explosions and fires long-term statistics conducted by the gas services and organizational units of the State Fire Service indicate that despite the continuous increase of the safety level of gas supply system and number of actions taken in this regard, still many failures are recorded, which often generate serious threat for the external and the inner environment of a man, as well as create risk for human health and life. The consequences of failures, during which the release and dispersion of natural gas occurs, depend on its type, nature and causes, as well as from the efficiency of its removal.Failure frequency evaluation in the operation of gas supply subsystem should be one of the priorities of the gasworks, which should attach greater importance to assess the proper functioning of the newly designed, as well as the implemented systems [31]. With the increasing pressure from the environmentalists and stricter standards for acceptable environmental pollution and structures vulnerability in terms of its protection, it seems to be a necessity [6,24,28]. The issue connected with failure gas pipeline analysis in perspective of improper design, construction and maintenance is presented in work [11], the increased failure affected by the lack or improper conduct of repairs and modernization, also incorrect or lack of risk management program. When planning renovations or modernization of gas networks the gasworks employees should make the classification of pipelines, that means determine which sections of the network require immediate repair, and which can be repaired later [7,15,26]. For this reason, making the appropriate maintenance (repair, renovation, replacement) only after the damage of the element may be irrational, control human intervention detects and removes faults being a potential source of failure. Widely used solution become the preventive renewals, aimed at reducing the loss of utility of a given element in different environment [4,8,21]. Very important from operator perspective is the failure reason [18,20,29], as well as modernizing actions that should be taken to avoid such undesirable situations. The strategy of the preventive renewals is to establish such timing of the renewals which will enable to achieve the maximum profitability of the project, through the use of the periodic strategies involving the renewals after a certain period of element operation [5,11]. Such classification can be made, for example, on the basis of failure prediction for certain sections of the gas network, using the Monte Carlo method [30,34]. The Monte Carlo methods include all proceedings aimed at finding approximate solutions of some problems (mathematical, technical or operational) [27]. The Monte Carlo ...