For the guide to improve the ship propulsion system reliability, MESJ Boiler Committeecollected the failure data occurred in 15 turbine ships launched about 1972, 1973 under the helpof those ship's owners. According to the analysis of those data, this report presents the statisticaland physical characteristics of serious failures troubled above turbine ships. As for the statistical characteristics, mean failure time is 9.6 hours which is shortened with the comparison of 10.45, 15.6hours of the ships launched about 1966, 1967. MTBF is 3717 hours, which is longer than 1547 and 1200 hours of those ships launched about 1966, 1967 and about 1969, respectively.Therefore mean availability is fairly improved to 0.9975. The 56% of the total failures has occurredin the boiler systems, being most responsible for the propulsion system reliability. The turbinesystems have a minor responsibility for the failure occurrence, but their mean failure time is thelongest of 22 hours. As for the physical characteristics, the leakage failure is most important, whichoccurred in any equipment of the propulsion system. Among the equipments composing the boilersystem mechanical failures of GAH and leakage failures of FWC should be paid attention. GAH and FWC failures are apt to break down the total propulsion system. The turbine system were troubled mainly by the failures due to the defects of lubricating equipments and due to the vibration eventsof components.

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It is well known tendency that the demands to keep the best safety and availability of a plant and for minimizing of maintenance work and cost.
As one solution to meet these demands, a condition based monitoring and diagnosis system will be put to use.
A steam power plant is consists of several thermo-flow subsystems excluding the rotating part and they have relatively slow dynamic responses. Even though the measurement can be carried out by the conventional sensors applicable to the process control system, the location and the degree of abnormal cannot detect directly with them.
In such kind of subsystem, a particular abnormality is often indicated by changes in several measurable parameters. Then the diagnosis shall be carried out by means of a discrimination software.
It is necessary to maintain the requirements for above mentioned discrimination among the possible cause of abnormalities and for making available instruction of the abnormal condition, the software of diagnosis shall have a quantitative manner. However the quantitative processing of the measured parameters may lead some erroneous results owing to their numerical errors. We have to evaluate the measurement repeatabilities and accuracies and to consider an appropriate countermeasures in the diagnosis system.
This paper reports the following items based upon our research and development.
General concept and effectiveness evaluation of plant diagnosis.
Outline of diagnosis for steam power plant esp. thermo-flow subsystem.
Detailed and practical explanation of diagnosis for thermo-flow subsystem.
Instrumentation and output of diagnosis system.

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For a high speed or large-sized ships, the pressure and temperature of main boiler's steam are going up. Therefore, it needs to study the permissible limit of heat flux for the natural circulation boiler.
By the way, as you know, the hydrodynamic instability in natural circulation boiler will occur under some conditions. We imagine that the hydrodynamic instability prescribes the permissible limit of heat flux for the boiler. Consequently, we perform the experiments and theoretical analysis to get informations about the condition of the flow oscillations.
Our analytical model is based on Terano's linear approximation which treats of the dynamic behavior of a one-through boiler. We extended his method to the small perturbation of pressure drop of two phase flow. The mathematical representation of the pressure drop is shown in this report and we discuss about some author's frictional coefficient concerning to the threshold of instability for a boiling channel.
Then, we show there are two analytical results about parallel boiling channels, one is from loop instability and the other is from parallel channel instability respectively. In all case, the threshold of instability for parallel channels is lower than that of the loop.

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The fluidized-bed combustion chamber for marine boilers burns fuel oil under heeling and rolling conditions. The performance of the fluidized bed was studied with three experimental fluidized beds. One test bed was stationary and 150mm in diameter. Another was 500mm×150mm in size and was sit on a heeling and rolling rig. Using the two beds, cold tests without firing were carried out to see the behaviour of the fluidized bed. The other was also stationary and 150mm in diameter. Fuel oil was burnt in this bed under various operating conditions.
Under cold condition, the stationary test confirmed the relation of bed height to pressure drop in bed and the stabilization effect of the immersed tubes. The heeling and rolling test cleared that heeling had some effects on the pressure drop distribution in bed but the effect of rolling on the pressure drop distribution was insignificant. The effect of heeling and rolling on the bed behaviour was studied for variable heeling angle and variable frequency.
With the oil fired test bed, various parameters including the temperature distribution in bed, the heat transfer rate to immersed tubes, reduction rate of NO_x emission by the two-stage combustion method, desulfurization performance with lime stone and so forth were measured and analyzed.

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This report is based on the research materials discussed and put together by the Machinery Plant Committee Group 3.
Recently heavy fuel oil for naval use has been changed for more and more high viscosity. According to this transition, problems due to solidification in fuel oil piping system have been taken up and investigated. In this paper countermeasures to solidification adopted on shipping are described, and heat calculation methods as to steam tracing are given full particulars.

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