The authors have developed a new technology that enables it to use lubricating oil (LO) semi-permanently and reduces LO consumption. Also, the technology remarkably improves reliability of machines. The techonology always keeps LO clean as the kidney of animals always keeps their blood clean. It is, therefore, called kidney system. There is no oil renewal forever and it is enough to supply only a small amount of fresh oil sometimes to compensate for the lost oil. No waste oil is, therefore, generated in the kidney system. The system has been working well in about 1000 units of marine and cogeneration diesel engines and in many hydraulic machines almost without any machine troubles for many years. In the kidney system, detergent disperesant and antioxidant are not needed. Only in case fuel contains some sulphur, alkali and disperesant are needed also in the kidney system.The dispersant is used to keep the alkali dispersed in LO.In this paper, it is reported based on the field data why detergent dispersant and antioxidant are not needed and harmful in the kidney system.

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Through the past studies, it has been pointed out that the duration of free rotating period of propulsion shafting system may affect the stopping ability of the ships. However, in the studies of predicting stopping ability of the ships, more specifically in the predicting stopping distances of the ships, it is a common practice to treat the free rotating period as a certain fixed length of time, or to neglect as it is short.
It may be one of the reasons why current simplified and practical predicting methods of stopping ability sometimes show greater deviations between the prediction and the actual result.
In order to solve such problems, at this time, the duration of free rotating period have been assessed for actual data of the ships with diesel main propulsion engines to grasp current situation, the scenario of free rotating of propulsion shafting system has been considered, and based on which how the free rotating period affects the stopping ability has been considered.
In addition, possible predicting method taking essential feature of free rotating of propulsion shafting system into account based on practical and reasonable approximation has been considered, using which trail calculations have been carried out on the sample data of 132 vessels. Deviations between predictions and actual results have been improved compared with conventional method.

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Most of industrial plants such petrochemical plant, LNG plant, and power plant, usually use water for the process cooling. Especially, in a large industrial plant, a large amount of seawater is used as the cooling media, and finally discharged to sea area through a seawater discharge basin.
The seawater discharge basin has a weir to keep the sufficient backpressure of the seawater cooling system. In the seawater discharge basin, the seawater overflows the weir and falls down into the seawater flow at the downstream of weir. Then, the air is entrained into the seawater at the downstream of weir due to the waterfall flow and air bubbles with various sizes and shapes are generated in seawater.
From the viewpoint of an environmental conservation, it is often required to eliminate air bubbles contained in cooling seawater discharged from industrial plants to sea area. There is a de-aeration chamber as a technology to separate these bubbles from the discharged seawater.
To perform the optimum design of the de-aeration chamber, it is important to grasp the volume and size distribution of air bubbles generated in the seawater by the waterfall flow at the weir, and a terminal velocity of air bubbles rising in seawater.
Therefore, in this study, the terminal velocities of any bubble in swarm of air bubbles rising in stagnant seawater, were measured in the region of low void fraction.

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It is very important for realizing the automatic water quality treatment to analyze the behavior of water quality of marine turbine plant. Following the first report, which investigated the change of pH and phosphate ion concentration in boiler water, this second report studies the influence of hydrazine on the water quality of marine steam turbine plant.
In this study, the authors analyze theoretically the concentrations of chloride ion, silica and electric conductivity of boiler water, and also pH and electric conductivity of feed water. The analysis can reveal the maximum allowable concentration of residues in boiler water so that it makes possible to control the blowing-down appropriately. And the analysis shows some characteristics of boiler water quality and its treatment system which are to be helpful to marine engineers.

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