"Risk Based maintenance (RBM)" is a method to perform reasonable maintenance. The maintenance procedures and their interval are optimized based on the "Risk" calculated by PoF (Probability of Failure) and CoF (Consequence of Failure).RBM can perform the maintenance optimized safely and economically by using the CoF factor. Also, this is suitable for the long term management of facilities because this method is based on probability theory. RBM has already been known as a general method in Oil Refinery and Chemical Industry, and has a potential to optimize a maintenance of ships or offshore facilities.
According to recent survey results, potential sites for seabed mineral resources are widely distributed in Japan's territorial waters and exclusive economic zone. Prior to full-scale, commercial development of these seabed mineral resources, it is essential to survey deposits in a highly reliable and accurate manner.
The AUV (Autonomous Underwater Vehicle) is one of the most effective platforms for such purposes, since it makes it possible to maximize the survey and analysis by positioning itself as close to the seabed as possible. In an attempt to enable high-efficiency and high-resolution seabed surveys that can contribute to the future development and exploration of mineral resources, the authors have been working on the research and development of compact and lightweight AUV systems. In this paper, we introduce our state-of-the-art cruising AUV called NMRI C-AUV #04, including the results of its sea trials and the details of its main features.
Amid growing energy consumption backed by world economic growth, global demand of liquefied petroleum gas (LPG) and the number of LPG carriers are increasing. For a stable supply of LPG, the safety of LPG carriers is important. Risk analyses using risk models, such as Event Tree, are one of the effective ways to assess the safety. However, risks estimated by these models have large uncertainty due to limits to the availability of data. Therefore, it is essential to validate the value of estimated risks through such means as comparing it with figures obtained from statistical analyses of accidents in the past.
This paper presents the results of a statistical analysis that covered accidents of LPG carriers of 100 GT or greater in the period between 1990 and 2016. To take application of the International Gas Carrier Code (IGC Code) into consideration, the authors conducted the analysis by developing three categories: ships built in or after July 1986 (IGC ships), those built before July 1986 (old ships) and the combination of the two categories.
The results have showed that in the case of IGC ships, the Potential Loss of Life (PLL) was estimated at 1.4×10-3 (fatalities/ship year). The PLL of IGC ships was clearly lower than that of old ships. In addition, the authors calculated PLLs and confidence intervals of each casualty category. We believe that these results will help verify the validity of PLLs calculated from risk models for LPG carriers.
DC generators began to be used in the 1930s and were replaced by AC generators in the 1960s. The author describes how TAIYO AC generators were developed, the background behind these developments and future issues facing such generators.
Gantry cranes for container handling (hereinafter referred to as cranes) have experienced unexpected runaways caused by wind. The purpose of this paper is to clarify the effects of wheel load and sliding velocity on the frictional characteristics of the interface between crane wheels and the rails under dry conditions, which serve as a basic information when conducting a dynamic simulation analysis and designing cranes. In our experiment, we adopted an originally developed experimental analysis system and set such characteristics as the pressing load (wheel load) of the wheel on the rail and sliding velocity based on data collected when the crane started to run away by wind. It was found that the static friction coefficient, which is essential for clarifying conditions for a crane that starts to run away, was basically constant irrespective of the scale of the wheel load. In contrast, the dynamic friction coefficient, which is crucial for analyzing the dynamic characteristics of a runaway crane, showed a decrease when the wheel load and the sliding velocity increased. In this paper, we have examined the effects of wheel load and sliding velocity on the dynamic friction coefficient from a viewpoint of plowing and adhesion theories. In addition, we have shown the ratios of the dynamic friction coefficient to the static friction coefficient that can be used as a reference when designing cranes.