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Offshore Container Terminals and Ocean Capable Barges

By Harry Valentine 2013-09-04 15:09:00

A recent presentation at the recent Ports Maritime Conference at Cape Town, South Africa suggested a future increase in offshore terminals. The recent opening of the super-port at Colombo, Sri Lanka is an example of an island-based port capable of serving as a hub for several nearby nations. Plans are underway to develop deep-sea super-ports in Eastern Canada, with discussions underway to develop a second such super-port within the same geographic region. There are prospects for offshore, deep-sea super ports to appear in many other regions of the world, to serve as vessel-to-vessel cargo transfer points.

The trans-oceanic super ships will transfer containers to/from local and short-distance coastal vessels such as tug-barges and vessels built to sail along inland waterways. Tug-barges that sail in the Gulf of Mexico use ocean-capable hulls classified as ‘unrestricted’ while ‘restricted-hulls’ predominate on vessels that sail along inland waterways. The development of offshore super-ports will require development of methods to simultaneously move multiple barges to/from the super-ports, dropping off or picking up barges at smaller local ports on inbound and outbound sailings. One method developed many years ago involved a vessel capable of carrying multiple barges.

Barge Carrier:

During the mid/late 1970’s, a Danish shipyard built a semi-submersible, twin-hull catamaran vessel capable of carrying barges laden with containers. It carried inland waterway barges across the ocean between Indian west coast ports and ports located at Muscat (Oman) and around the Persian Gulf. One version could carry barges placed laterally across its deck. However, the beam of a twin-hull barge carrier carrying barges placed transversely on its deck would preclude it from sailing upstream along many navigable rivers that will include the Mississippi, St Lawrence, Nile and several Asian and South American navigable rivers.

The development of offshore super-ports requires new thinking into how to simultaneously transport groups of multiple barges across a short oceanic distance between mainland and offshore ports so as to interline productively with super carrier ships. A twin-hull vessel carrying barges placed transversely on its deck may incur the equivalent beam of a ‘Valemax’ ship (65-metres). In service, it could serve shallow-depth ocean coastal ports while only being able to sail into the mouths of certain rivers, where it would need to off-load the barges. The volume of containers being moved may require a different design of barge ‘carrier’.

Ancient Maritime ‘Engineering’:

Many centuries ago, early maritime people developed methods by which to sail small boats on the ocean. The ancient Egyptians built flat-bottom vessels that could sail on the Red Sea, in the direction of prevailing winds. People living on Pacific islands learned to stabilize flat-bottom inland vessels (‘restricted’ hulls) such as canoes for ocean sailing, by adding a parallel section known such as an ‘outrigger’ secured to the canoe by a pair of transverse beams. They also placed 2-canoes side-by-side at a distance and lashed them to transverse beams to form a crude catamaran.

There may be scope to adapt ancient maritime engineering practice to modern inland barges built with ‘restricted’ hulls, to enhance ocean sailing capability. A retractable or removable ‘outrigger’ would stabilize such a barge when it encounters ocean waves. Connecting 2 x parallel barges placed a distance apart by pairs of transverse triangular trusses results in a twin-hull catamaran vessel able to carry containers stacked above each hull, with only a minimal structure connecting the twin hulls. A tug could tow a pair of sideways-connected barges on the ocean, probably using a triangular towing cable that connects to each bow.

Coupling Ancient Maritime Concepts:

A barge stabilized with a removable or retractable portside ‘outrigger’ may be lashed on its starboard side to a similar barge with a starboard-side outrigger’, with ‘cushions’ placed between the barge hulls. The bows of a trailing pair of barges with ‘outriggers’ may be coupled to the sterns of the leading barges, using spring-loaded cables and ‘cushions’ at the stern-bow interface. Towing by tug on the ocean requires that the barges have greater freedom to roll and pitch. On calm inland waterways, the barges would be couple directly to each other and sail minus the outriggers (or outriggers retracted).

There may be scope to develop removable or retractable sideways coupling technology to connect pairs of inland barges built with ‘restricted’ hulls side-by-side, forming twin-hull, ocean capable catamaran-type vessels. The sides, front and rear bulkheads around the cargo areas would need to be raised to prevent containers from being swamped with seawater. Multiple spring-loaded cables would couple the bow of each trailing ‘catamaran’ unit to the stern of the leading unit ahead of it, with a ‘cushions’ placed at each bow-stern interface. A triangular cable would connect the twin leading bows of barge train to the tug.

Natural World ‘Engineering’:

While modern versions of ancient maritime engineering could enable inland barges and barge trains to sail on the ocean, there may be scope to borrow other precedents from the ancient and natural worlds of ocean ‘engineering’. The puffer fish is able to inflate with seawater and courtesy of its tough skin and natural built-in ‘control valves’, increases is physical volume to protect itself from predators. Modern design and manufacturing technology can develop seawater inflatable puffer fish ‘cushions’ that may be placed at bow-stern interface areas of coupled barges, also between the sides of barges.

Factory-made puffer fish ‘cushions’ would include air or oil chambers to provide buoyancy and be pumped with seawater after being placed in the bow-stern interfaces of coupled barges to provide the role of cartilage. The combination of spring-loaded towing cables and puffer fish ‘cushions’ would cushion the impact of barges (included versions stabilized by outriggers) bumping into each other while being towed across ocean waves, preventing damage to the barges and the cargo. Modern factories may produce tubular or sea serpent versions of puffer fish ‘cushions’ that may be placed between the sides of single or multiple barges.

Pumped Sea Serpent:

A giant seawater-pumped sea serpent would include oil or air chambers for buoyancy and provide lateral cushioning between barges stabilized by outriggers as they sail across oceanic conditions. An inflatable sea serpent may be built to the length of multiple barges to provide lateral cushioning along an entire barge train. The design may also include a central towing cable, with branch cables to link to each successive pair of towed barges in the train. Restraining cables connecting the pumped sea serpent and barge sterns would assist bow-stern ‘cushions’ in minimizing longitudinal impact loads caused by ocean waves.

Pumped hydraulic pressure within the serpent would provide flexibility to sail through ocean waves and semi-rigidity to cushion lateral and longitudinal movements that wave conditions would impose on the barges. The semi-rigidity of the pumped sea serpent and puffer fish ‘cushions’ would allow some relative pitch, roll and yaw between barges during ocean towing. When the barge train arrives at the mouth of an inland waterway, the pumped sea serpent, puffer fish ‘cushions would be deflated of seawater and outriggers and lateral coupling technology removed or retracted to allow barges to be directly coupled into a river train.

Making the Serpent:

Manufacturers of automotive tires would be able to modify their production machinery to fabricate inflatable sea serpents of equivalent diameter as commercial automotive tires. Industrial knitting mills are able to knit tubular structures from threads of nylon, fiberglass and other fibers that may form the basis of an inflatable sea serpent. The knitted tube would provide tensile strength to withstand high internal hydraulic pressure while a thick-walled sealant of rubber or silicon would prevent leakage and provide an extended service life. An inner reinforced tube may hold either oil or compressed air for buoyancy. 

Barges with Unrestricted Hulls:

While barges built with ‘unrestricted’ hulls may sail on the ocean, the volume of containers arriving and leaving offshore super-ports would require that such vessels sail in a train. While a tug pushes and navigates a leading barge, it may simultaneously tow a second barge. The use of a V-notch stern that matches the bow of a trailing barge would allow the placement of seawater-inflatable cushions at the bow-stern interface, with towing cables connecting between them. A triangular towing cable behind the tug may place towing cables along the sides of the towed barges.

The cable arrangement may provide equal pulling power near the bow of each successive barge in the tow, allowing a single tug to simultaneously push and navigate a single leading barge while pulling a short train of 2 or 3-barges. Such a barge train connecting at a super-port may move one barge each to/from 2 to 4-local smaller seaports on a single voyage. Such operation may become possible across:

Gulf of Mexico

Caribbean Sea

Bay of Bengal

Arabian Sea

South China Sea

Black Sea

Mediterranean Sea

Baltic Sea

North Sea

Gulf of St Lawrence.

Conclusions:

Super-size trans-oceanic ships will interline at offshore, deep-water seaports with smaller local coastal vessels and vessels that sail along inland waterways. There will be need to improve ocean sailing capability of inland waterway vessels that may sail in trains between rivers and offshore super-ports. Future improvements to ocean tug-barge technology will need to allow a single tug to simultaneously move multiple barges built with ‘unrestricted’ hulls between local ports and offshore super-ports. The innovative thinking of maritime engineers and naval architects will need to enhance the operational efficiency of small local vessels that will sail to/from offshore super-ports.

Harry Valentine is a frequent contributor to the MarEx e-Newsletter. He can be reached at harrycv@hotmail.com for comments and/or questions. Also feel free to leave comments below.

The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.