with Mechanical Connection ARTICOUPLE & TRIOFIX
--- its multifarious advantages and utilities
The method of running barges under pushing was originated in large rivers in U.S.A. and, nowadays, this method is widely employed in many large rivers in the world. But, the history of its use as a means of open-sea transport is not so long and goes back about 30 years only and, even now, pushed barges are considered means of transport in shorter routes and not trans-ocean transport, mainly because the speed of a pusher-barge combination is unexceptionally lower than that of ordinary cargo ships and tankers of same loading and same engine power.
But, in shorter routes in which the speed and fuel cost have a comparatively lower importance, the pusher-barge combinations with lower personnel expenses exhibit their excellent advantages over conventional cargo ships.
When, for example, several barges are operated in a short route of service, such as lighterage service, the conventional rope-towing has so far been used as a common practice in most cases. But, in such a service, introduction of the pushing system, particularly mechanically connected one, can improve the operational efficiency remarkably through raising the running speed and saving the time needed for berthing, unberthing and exchanging barges, and, at the same time, the safety of operation is likewise improved. The advantage of pushing over towing can be easily understood from the comparison below.
There are two types of connection in pusher-barge combinations --- rope-connection and mechanical connection. The merits of the latter over the former are easily understood from the comparison stated below.
As may be easily understood from the above statements, the operational efficiency of pusher-barge combination, particularly mechanically connected one, is so higher than that of towing that the additional cost for introduction of pushing system can be recovered in a short time.
The 2-pin supporting articulate couplers ARTICOUPLE have been proven in their practical use to realize all the merits enumerated above.
In spite of the above-explained rationality and high efficiency, and, in addition, the good sea-worthiness realized by introduction of mechanical connection system, however, pusher-barges could not compete economically with conventional cargo ships in longer routes. The reason is the lower speed of the barge train and, if a comparative speed is desired, big fuel consumption due to enormous power requirement deteriorates the profitability remarkably.
The cause of the low speed is the large resistance due to eddies occurring in the wide clearance between two hulls which cannot be dispensed with to permit freedom of relative pitching of the articulately connected train.
The 3-pin supported rigid connection system, TRIOFIX, was introduced to give a solution to this problem. This new method of connection involves a possibility to design favourable hull forms relationship with least generation of eddies and, at the same time, to afford comfortable- ness to the crew through eliminating the heavy pitching of the pusher in waves.
Even TRIOFIX-connection cannot realize a perfect eddiless combination, but it can limit eddies so well that the speed difference may be in the order of 0.1 - 0.3 knot when the hull forms are well designed, and its introduction will open up a possibility that the routes where pusher-barge combinations are economically operable will be much elongated.
The above explanations exhibit the advantages of pusher-barge systems as means of simple cargo transport. These advantages are still partial, and there are other important advantages --- manoeuvrability and quickness in motion --- which can be exhibited at harbour works and in harbour/marine construction sites, together with time- and manpower-saving, higher safety for crew, etc.
Introduction of pusher system will bring about a remarkable improvement of efficiency through high degree of time- and manpower-saving. If a pusher is introduced into the marine construction side, other workvessels, such as floating cranes, etc., can be non-powered vessels needing no high class officers, and the time needed for preparation before their main works can be remarkably saved. In such a case, it is indispensable to standardize the coupler and the arrangement of connecting parts of all the related vessels so that a complete swappability may be maintained. It is further recommended that the pusher(s) will be arranged for conventional towing, as "pusher-tug", and, in some cases, also for pushing under rope-connection. It may even be possible to utilize the pusher as a multi-purpose service boat having other functions, such as anchor tender service, hydrographic survey, diver boat service, etc.
The couplers with friction components can adapt themselves, under control, to the change of draught of barge due to loading and unloading. This character has widely been utilized on a number of dredging barges taking sand by suction from sea bottom in 3 - 4 metres high waves.
Different from those of pure multi-step tooth-engagement principle, couplers with friction components can connect even when the pusherboat is more or less oscillating due to waves. This character may be useful in some cases in the field of offshore activities.
In the past 30 years, several types of couplers have been developed to meet multifarious types of demands from the clients. Nowadays, ARTICOUPLE and TRIOFIX can cover all probable types of needs for pusher-barge systems.
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