One of the major factors in successful transportation operations is the prime mover available and how it relates to the performance desired through reliability and economy of sustained operation. The automobile (including trucks and buses) is the largest form of transportation, and reached its high degree of development through mass production and its prime mover, the internal combustion engine, was the first prime mover of any type to be really mass produced in volume.
It was only natural that the diesel engine would follow the same course and today both medium and high speed diesels are mass produced for broad markets in the transportation and power generating industries.
New waterborne vehicles are placing a heavy load on their designers to provide efficient vessels for carrying the world's commerce on oceans, lakes, harbors and rivers. Some of the vessels are entirely new in concept and all of them are revolutionary even when compared to their latest predecessors. Many of the new vessels must be dual purpose or perform multi-functions. The powerplant for such a vessel must be a flexible system and its prime mover and transmission components will have to provide a total power facility. The designers and builders are facing a tremendous challenge in order to place these vessels in the operators' hands at a price that will insure the proper return on investment. To do this, they are looking to components and systems doing a similar duty in other industries. Where they find these components they are assured of a reliable proven product at the lowest possible cost.
Figure 1 illustrates the side view of a cargo-ship power unit where two 3,600 bhp diesel engines each drive through a generator into a twin-pinion, single-output reduction gear to supply 7,000 hp to a controllable-pitch propeller. Each diesel engine is mounted on a common base with its accessory module, ac-dc generator, and air clutch.
Both diesel-engine-unit common bases at the power takeoff end are supported on the common reduction-gear frame. The accessory end of the diesel units is supported by the ship's structure. The unit, as illustrated by Figure 1, is made up of a standard production diesel engine, a prefabricated engine accessory module, generator, and air clutches. The common reduction gear is of conventional design but is subject to variation in the housing configuration and reduction gear ratio to meet the ship designer's specific requirements. The diesel engine, accessory module, generator, and air clutches are volume produced and used extensively in several major industries and the marine industry.
Figure 2 follows from Figure 1 and illustrates by block diagram the total power system for a self-unloading cargo ship. A total of 14,000 shp is available for propulsion through two controllable-pitch propellers and four prime movers. When propulsion demands are reduced, in channels and harbors, one engine can be released from each propeller by deflating the air clutches. These engines can now supply electrical power from their generators to drive the bow and stern thruster motors. After the vessel is secured to the dock, all four engines are available to furnish electrical power from their generators to the ship's unloading machinery motors.
Programming of the ship's power has been kept as simple as possible without sacrificing maximum flexibility. Experience and equipment, borrowed from marine, oil drilling, locomotives, and electrical utility applications, assure this flexibility and keep the costs within practical limits. Controls consist of a central control panel, generator control cabinets for each power unit, a common motor control cabinet and an unloading control station. The central control station is a compact panel pushbutton type which can be located in either the pilothouse, engine room, or both.
The total power systems are put together from components used in several industries, thereby passing on to the user all the benefits each industry has developed. These benefits are: lowest possible first cost, proven reliability, lower installation and maintenance cost and minimum operational attendance.
The first cost of this power equipment, on a dollar-per-horsepower basis, has remained almost static for the last five years in spite of material and labor cost increases. The reasons for this are continual product refinement to take advantage of new materials, manufacturing methods, lubrication, and other technological advances.
Proven reliability and low maintenance advance together particularly when the components serve broad markets where vast field experience guides the engineers to the specific items that require further development.
Note: Mr. Ramsey presented the paper condensed here at a meeting of the Great Lakes and Great Rivers Section of The Society of Naval Architects and Marine Engineers.