The air-water separators in this study are based on the principle of the electrostatic precipitator with the positive and negative poles, which has been widely utilized to collect the dust contained in flue gas exhausted from the industrial plants such as coal fired power station.
This mechanism of separation is that the water droplets charged negative ions by corona discharge are collected on the positive pole by the Coulomb force operating between the both poles.
Two kinds of experimental separators for vertical upward flow are used, one consists of a duct with a crosssection of 52×52mm and length of 700mm made of transparent acrylic plate with two sheets of zinc plate as positive pole and copper wires of φ 0.32mm as negative pole, and the other consists of a cylinder of φ 57.2mm and maximum length of 462mm made of stainless steel as positive pole and a stainless wire of φ 1.0mm as negative pole.
The whole experimental duct is of the same material and the same sross-section as the former separator so that the atomizing condition of water from the nozzle and the behavior of water droplets can easily be observed.
Experiments were conducted at 2.2 to 4.0m/s in mean air velocity and 0 to 17kV in DC high voltage, and the fractional separation efficiency and overall efficiency were obtained, and the performances of all separators were discussed.

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A ship is equipped with many apparatuses which had the reason for the growth of vibration. Particulalry, it may give rise to the serious large vibrations due to the coupling effect of main engine and the double deck bottom. As its size is becoming larger, the natural frequencies are decreasing, it has become unavoidable that it happens to resonates under the usual running condition of the main engine. For that reason, it is important to decrease engine and hull vibration considering the coupling vibration behavior. Therefor, we tried to apply the mechanical impedance method to solve these vibration problem. However, measuring method of mechanical impedance of support points of large diesel engine has not been established until now. This paper described a new method which was suggested to measure the mechanical impedance, and showed the experimental results using the plastic model to show the effectiveness of this method.

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The bearing metal of a marine diesel engine is basically disassembled every five years as a part of a special survey. However, this disassembling and assembling works require a large amount of manpower and time. Moreover, it is also dangerous. The classification society to which the authors belong has dedicated considerable time and efforts to examining whether used oil analysis can be applied as an alternative to the aforementioned periodic survey.
This paper reports on the correlation between the used oil analysis results by ferrography and the inspection results of 2 stroke diesel bearing metal obtained at special surveys.
As a result, the authors believe that the continuous engine system oil ferrograph analysis can be effective as one form of a condition monitoring based survey.

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Greater part of Japanese domestic commercial ships install Low-speed, four-stroke trunk piston type engines as their primemovers enjoying its merits in fuel economy and maintenance cost.
Marine engines have been improved restlessly to be less fuel consumption, higher output, and availability of low quality fuels especially since world oil crisis.
Fuels supplied to ships recently have mainly been manufactured in catalysis process plant or distilled residues thined down by visbreaker-refined light oil because oil suppliers make their process fit to increasing market demands of lighter oils.
Fuels manufactured by these process have negative properties such as low ignition quality, long combustion period and low thermal stability that cause troubles in engines and auxiliary machineries.
Considering that there is close relationship between contamination of system oil and bad combustion inside engine, we studied system oil contamination and fuel quality comprehensively.
As a result of this study, we have establishied a guideline with which engineers are able to judge whether system oil contamination has been caused by bad combustion of engine or other reasons.

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Oil purifier and oil filter play a role in purifying the lubricating oil of main engines and generators in marine vessels. The filters and oils of large trunk piston engines (TPE) after use were analyzed for determining the influence of lubricants on filterability. The filter clogged contained a large amount of carbon and CaSO₄, and a small amount of CaCO₃. Carbon and CaSO₄ could be removed easily from the filter by solvents washing. On the other hand, CaCO₃, which was formed by hydrolysis of overbased detergents, could not be removed easily probably because it was in a large needle-like crystal form. In order to wash off the clogging materials containing CaCO₃, it was necessary to wash by “ultrasonic washing method”.
The CaCO₃ contained in fresh overbased detergents exists in amorphous form. However, the amorphous CaCO₃ is metastable thermodynamically and transforms to the needle-like crystal, calcite, on heating in contact with water during use. The period until the filter would be clogged depended upon the amounts of the particles that have equal to or larger than the mesh hole of the filter used. The small particles ranging from 3 to 4 μm which were made from carbon and CaSO₄ did not affect the clogging period. On the contrary, large particles from SiO₂ and CaCO₃ substantially shortened the clogging period.
In conclusion, it was shown that the most important factor of lubricant filterability was the hydrolytic stability, which controlled the formation of needle-like CaCO₃ crystale. The effects of the oxidation stability and the dispersion performance of lubricants were found to be negligible.

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According to analized the turbine and diesel plant reliability, we were able to picked up some problems to make large amount of Failure Rate or Manning Index.
1) Mainly trouble of auxiliary equipment caused by low grade fuel. The most affected equipment is the fuel purifier and also following equipment affected too,
Diesel Plant: LO purifier, Auxiliary boiler, DIG, M/E, FO filter LO filter, Incinerator. Turbine Plant: Main boiler burning equip.
2) Automatic equipment failures occurred 18 days each and need 8.5 MH. MI and FR are occupied approximately 1/3 of whole plant. These are judged ghost & unknowm reason that is about 50 to 70%.
3) Turbine plant are needed much recovery time to maintenance for cooling down the steam line, move the big mass of heavy weight and valve operate for complex construction. Mainly cause are aging, defective fitting and poor materials.
So, we should make some counter plan to reduce the Failure Rate and Mannind Index as follows.
a) To be developed fully automatic treatment system of fuel and waist oil (FWTS) to reduce a failure ratio of fuel and LO purifier, auxiliary boiler, etc.
b) To be developed Total Distributed Control System (TDCS) with back up controller to increasing continuous running of control equipment and quickly recoverling.
c) To be set the central fresh water cooling system (CCFW) to reduced a pipe corrosion and Maintenance man hours.

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