FORECASTING REPAIR WORK ON GAS PIPELINES UNDER A CENTRALIZED SERVICE SYSTEM

The management process of the gas-main pipelines' technical state that includes different-type constituent elements and has a complex multihole and looped structure is considered. The task falls under the optimization category of the maintenance process. The study aims to optimize the preventive overhaul graph of the gas supply system that includes independent subsystems. An optimum schedule of maintenance service will be determined by selection condition of the timepoint values that provide with the quality indicators' extremum of the functioning of the process facility complex within a centralized service of gas supply system. It was suggested the technical-and-economic index, in particular the average summarized unit costs to system operation, be used as a criterion for the optimality of maintenance process. The characteristic curve obtained from conducted studies provides a way to estimate the maintenance states of the complicated gas supply system that includes different-type, geographically distributed but functionally interlinked process facilities of the gas supply system in the region of the central maintenance and repair base, they give an opportunity to plan an optimum schedule of the preventive overhaul of the gas supply system.

A Heuristic Method for Minimizing Makespan in M-Stage Hybrid Flowshop

This paper deals with a scheduling problem to minimize makespan in m-stage hybrid flowshop with unrelated parallel-machines at least one stage. Since the problem is known to be NP-hard, a two-phase heuristic algorithm is proposed to obtain a near-optimum schedule efficiently. In the first phase of the proposed algorithm, some promising schedules with an identical job-sequence to all stages are generated by applying NEH algorithm in various ways, and then search better schedules by applying some heuristic job-moving strategies to these schedules in the second phase. Numerical experiments are implemented to demonstrate that the proposed method can provide a near-optimum schedule within a reasonable computation time.