and we can not only improve the availability, but also reduce ship's
expenses, if daytime watch by engineers is good enough to keep the engine running with
higher technology like ship's with engineers on duty just for daytime. This status is
expressed by the points 2 and 3 of curve 2-3. Even if service parts are enough in number
with less maintenance crew, they can not maintain the ship sufficiently because of
manpower. Then, workers will have to be hired to maintain and repair ship while the ship
anchors at port. In this case, it is better for us to keep repair parts in port. The
steamship company has experienced this method through the operation of modernized ship. We
must evaluate the influence of items of repair parts and their quantities upon the ship's
availability.
FIG.1 Minimal allowable availability and maximum allowable cost.
It is important how to mix availability and balance of investment, and
levels of support, operation and management. It could be a policy of a maritime power to
find out the optimal mix of them. It is expedient to reduce labor of ship by the shore
support enough to do maintenance works, resulting in specializing in ships maneuvering. On
the other way, it is expedient to strengthen a crew's burden while we lower the shore
support level so that we can keep higher maintenance and operation capability of the ship.
A ship regime modernization committee (Japan) presented fourth
recommendation in June, 1992. Thus, steamship companies in Japan are now operating
modernized ships of fourth kind. These are called as ship of practical use, ship for
foreign trainee effectuation, ships for floating maintenance. Container ships and bulk
carriers have been operated with 11 ship's crew and 4〜7 maintenance workers.
Past records of maintenance and repair were investigated which has the
headquarters in Singapore. Item cost of repair parts was shown in FIG.1. This repair shop
has purchased 230 pieces of parts by 49,450 dollars, and these are necessary parts for the
repair business. The average price is 215 dollars, with a maximum value 4,421 dollars and
minimum value 1 dollar. FIG. 2 shows that 50% of the gross expenditure to purchase parts
is occupied by the most expensive parts of 13 items with their average price 2,115
dollars. The second group of next 10% was composed of 8 pieces of parts with average price
of 625 dollars. The cheapest 10% group of parts was composed of 120 parts with average
price of 37 dollars. The MTBF of individual parts is unknown. Whichever on board or on
land service parts are stored, the investment in inventory and its interest rate can not
be disregard(Miki, 1995).
FIG.2 cumulative total of service parts purchased
Note: Abscissa shows parts number (230 piece in all), and vertical
axis: cumulative value purchased (dollars).
With regard to ship maintenance and repair, the following program has
to be made.
(1)When and which maintenance works are conducted? Which of crew takes
care of the works? What kind of tools are used? Scheduling is made with maximum use of
human resource and equipment cm board. Longer program of OBM works are made say about 3〜6
months before dry docking. As docking becomes nearer, the short-term OBM schedule must be
detailed about a week before. Long term schedule are fixed considering the volume of
maintenance work for the period. Short-term schedule are made in detailed program such as
operation sequence, workers, machinery and tools required, etc. As a case study for this
research, the logbook during dry docking of training ship, the Tokai University Maru II,
when one of the authors took office as ship master, was analyzed especially that when the
number of dock workers increases, how much time in dry dock can be reduced?
