The range and flows of manufacturing processes in the surveyed engine manufacturing factories are shown in Figure 1. Since half-finished products such as cast/forged steel parts, finished parts and equipments are purchased from other companies, only machining works such as milling of main parts and assembling works are done in-house.
The processes in engine manufacturing factories to be considered in the LCI analysis are machining, assembling and land trial, of which details are explained as follows.
* Machining
Cutting is the prime work of the machining process done in the factory. Planomirrors and horizontal boring machines are operated in machining large parts such as bed plate, column and cylinder jacket. Main machining works done in manufacturing process are turning (cylindrical turning, taper turning and boring, etc.), cutting and drilling, etc. Other main machines operated for machining are machining-centers, numerically controlled (NC) lathes and vertical lathes, etc.
* Assembling
Assembling works are roughly divided into two stages, block assembling and whole assembling. After main parts such as bed plate, column, cylinder jacket, etc. are assembled separately, marine main engines are assembled as a whole. Cranes, fork lifts, tractional carrier machines, etc. are operated for assembling works.
* Land trial
Land trial is done in three steps as follows. Engine operation time is about 12 to 25 hours, although it depends on factories.
(1) Fitting trial: The engine is preliminarily operated from no-load to full-load gradually.
(2) Tune-up trial: After cam gears and timing of fuel injection are tuned up, the engine is operated from no-load to full-load with power changed in several stages.
(3) Official land trial: The engine is operated from no-load to full-load with power changed in several stages in company with customers.
2.3 Composition of marine main engines
According to the hearing surveys, the output power of a 2-cycle diesel engine loaded on the 85,000 (DWT) tanker ranges 12,000 to 20,000 (PS). The total number of parts composing the engine seems to amount to tens of thousands. In this paper, the authors regarded that the engine is composed of about thirty main parts. Main parts composing the engine are shown in Table 2. They are classified into five categories, that is, large-sized cast iron/steel parts, small-to-medium-sized cast iron/steel parts, machine-processed parts, large-sized rolled steel parts and equipments. Their weight accounts for nearly 80 percent of the gross weight of the engine. The gross weight includes the engine body up to flanges but doesn't include the equipments which are supplied with by shipyards, such as all sorts of pumps (fuel pump, sea-water pump, lubricating oil pump, fresh water pump), cooler, fuel filter, hydraulic jack, all sorts of tanks, etc.
