Barges are old workhorses in maritime trade and commerce, especially in the domain of domestic supplies. They often act as ancillary support to mainstream commercial vessels participating in intercontinental freight transport. Though most barges are designed to operate in shallow waters like inland routes, rivers, or coastal zones, many sail in deeper waters, too, according to Marine Insight.
Design and Construction
Hopper barges are usually simple in design and construction, with totally bluffer forms, often with straight, sharp edges and almost no curvature.
The most defining characteristic of these barges is the large central cargo space that acts like a bucket for large cargo quantities. This region is known as the hopper. The extent of the hopper tanks defines the carrying capacity of hopper barges.
Hopper barges have a double hull configuration. That is, the boundaries of the cargo spaces are separated from the outer hull shell plating by a certain margin, and the internal region between these two layers is either void spaces or ballast tankage like the design philosophy followed in all modern large conventional cargo carriers like bulkers or tankers.
The distribution of ballast tankage also caters to the stability criteria of hopper barges, as these vessels need to withstand hydrostatic and hydrodynamic disturbances, along with other external effects, during transport and stay upright during loading and unloading operations.
For hopper barges operating in shallow water regions, the draft is a significant issue as during full-load conditions when the hopper spaces are loaded with heavy cargo with low center of gravity locations (from dredging deposits to sludges to heavy cargo like stones or earth), there is often an increased risk of grounding.
Understanding The Classification
Based on the size, capacity, and design, the barge can be:
- single hopper or having one hold where the cargo contents are dumped
- multiple hoppers or holds where cargo can be segregated and placed.
From a propulsion point of view, hopper barges can be either:
- Self-propelled
- Dumb
Dumb barges are usually towed or assisted by other means such as tugs. Self-propelled ones are powered by diesel engines and motors but do not have any requirements for speed. The rated propulsive power of the hopper barges is sufficient to propel them at the maximum design payload of the vessel.
Though, from the design point of view, hopper barges are just box-like structures as mentioned above, they may sometimes differ from each other in terms of the presence of a rake.
- No rake barges are just like dumb boxes with no design characteristics.
- Single-raked barges have only one rake in the way of either bow or stern.
- Double-raked barges are those having rakes in the way of both bow and stern.
Hopper barges have another form of categorization in terms of being:
- Open
- Closed
Open hopper barges are those uncovered types where the cargo is simply dumped on the hoppers or holds akin to loading bulk loose cargo in goods rail carriages or trucks. In open barges, the cargo quantity may often exceed the level of the top deck (and the hatch coaming) and appear as heaps.
Loading and Unloading
Loading and unloading of cargo is very important for hopper barges. These processes in the hoppers can be done through various processes like conveyors, excavators, grabs, and sometimes, using deck equipment like cranes and winches.
However, the discharging of cargo in some hopper barges is done through a unique system. The hull itself splits open at the bottom and releases the contents directly to the sea.
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Source: Marine Insight
