Natural gas vehicles (NGV) is now the most realistic solution to reduce the atmospheric polution and green-house effect of CO₂ produced by automobiles. NGV fuel gas cylinders are used to storage natural gas compressed to 200 bars (20MPa) and fabricated in four different types: (V1) seamless metallic cylinders, (V2) hoop-wrapped metallic liner cylinders, (V3) fully-wrapped metallic liner cylinders, and (V4) fully wrapped non-metallic liner cylinders or all-composite cylinders. This paper surveys the design tendency of fuel gas cylinders, and technological requirements in different types of fuel gas cylinders. Some topics are presented in detail on the technical measures for reduction of cost and weight and assurance of safety of NGV fuel gas cylinders.

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Risk-Based Maintenance (RBM) technique has been generated for the fossil-fired power boiler plant accumulated operating times exceeding 100, 000h. Risk is defined as a multiplication likelihood by consequence based on a semi-quantitative approach. In this paper, the procedure which includes the inventory, plant customization, and risk ranking in the RBM technique, is presented. As the result of application of RBM to a reheater system of a 600MW boiler unit, it is suggested that the technique provides the damage and structural integrity assessment according to a common basis, the optimization of inspection and maintenance program required the decision in urgency, priority, cost reduction of invested capital for maintenance, improvement of operation efficiency, and others. The RBM would be a advanced technique to improve maintenance systems based on many industrial experiences.

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