The reliability index gives concrete evaluation value to improve the quality on the design side. On the other hand, the maintainability index gives a key for judgment of work load and to find crew's optimum number to the operator. However, the index for evaluating the ship operational efficiency is few so far.
Availability index is one of the evaluating value for the ship operational efficiency. But if this index is applied to the marine plant, value of each equipment is very similar, because the each equipment MTTR is very short compare with the MTBF. The hazard index, which is proposed for the first time in this paper. Serious failure is a malfunction caused by the operation trouble like a stoppage and/or slow down of main engine. The cases of serious failure per 1000 hours is the serious failure rate. The hazard index is defined as the result of multiplying the effect hour per case [min/case] by the serious failure rate [cases/1000 hrs] . The effect hour means the operation delayed-hour due to trouble, which gives a serious effect on the operation performance. The hazard index is considered to be very appropriate for evaluating the ship operational efficiency. Because, the hazard index is a value of disable operation hour [minute] which is occurred during the operation for the 1000 hours, the size of this value is evaluation index of the ship's safety. This paper introdeces the reliability analysis on the serious failure situations which is the result of investigate on the statistical database.
The data had been collected from 1982/3 to 1997/3 and this involved 186 diesel vessels and 27 turbine vessels. Total failure cases of Diesel Plant was 97131. And Steam Turbine Plant failure cases was 9269. As a result of evaluation value for the turbine plant by using the hazard index, the degree of operation hazard is 60 percent compared with diesel plant. The number of failures of equipment with alarm system is smaller than that of equipment without alarm by 10 to 20 percent. The operational efficiency can be expressed numerically by adopting the hazard index. And, present tendency shows the reliability index and safety index is strongly affected by man-hour, and it is clear that maintenance man-hour as well as the failure rate should be decreased.
View full abstract