All-reefer container vessels enter service

The largest capacity all-reefer container ships in the world have been delivered to Dole Fresh Fruit from HDW, Germany.

Two examples of a new class of open top all-reefer container ship with a capacity of about 1,000 FEU containers, or 2,000 TEU, have been handed over to Dole Fresh Fruit International Ltd by Howaldtswerke-Deutsche Werft AG (HDW) Germany. The ships, Dole Chile, and Dole Colombia, were commissioned in November and December respectively, and will be used mainly for transporting bananas from Costa Rica to the East coast of the USA..

This capacity corresponds to a refrigerated space of approximately 2 million cubic feet, making them currently the largest cold-storage ships in the world. Conventional cold-storage ships have a maximum capacity of about 800,000 ft3. Rapid loading and unloading is ensured by two shipboard Liebherr gantry cranes, each with a carrying power of 40t SWL.

The experience obtained by HDW in developing and building the series of six open-top container vessels for the Norasia shipping company (the first ship was delivered in 1993) had shown that the forecast advantages in comparison to conventional container ships have been fully realised in practice, says the yard. These include a faster turnaround time, resulting in less time spent in harbour, and less damage incurred during transport.

The advantage of reducing the time spent in harbour was particularly important for Dole because the two ships have to visit several harbours in South/Central/North America in the course of a round trip and precise schedules have to be met. Furthermore, the open ship configuration offers considerable advantages with respect to heat disposal from the cargo hold.

Ship design

Particular demands were made on the design dictated by its proposed use, and its planned field of operations.

For example, the average weight of the fully loaded reefer containers is 25t, which is quite high in relation to conventional container ships, and makes for relatively high total carrying capacity. In terms of stability, the ship is designed to carry up to 30t containers right up to the top (11th) tier.

As both draught and length are limiting factors in some harbours, the resulting design has a relatively wide beam of 32.4m. A further reason is that as FEU reefer containers are to be carried, and the greater beam allows for better use of available space.

In addition, more containers in the hold means a lower centre of gravity for the cargo. This was advantageous because it offsets the raised centre of gravity of the empty vessel resulting from the two onboard gantry cranes, says the yard.

The vessels have seven open top container bays located in four holds to accommodate either TEUs or FEUs extending from the tank top to a level of 11 tiers high, of which four are above deck level. The holds have sufficient width to take 11 FEU containers athwartships. In addition, there is room for 11 wide x 7-high 40-45ft containers in another open top hold immediately forward of the accommodation block, over the main engine. The only hold to have hatch covers is sited at the bow, with room for two rows of 11 FEU containers across, and a maximum of eight tiers under the covers, plus a further three tiers on top. Forward of this area is a full width weather shield, extending to the bow, similar in design to those fitted to the Norasia vessels, and high enough to protect the exposed containers from spray.

Cargo loading and unloading

Loading and unloading is performed using two Liebherr electro-hydraulic gantry cranes which run on tracks on the deck. Each consists of a central carrying crossbeam on two supports with a travelling trolley lifting system. The crossbeam is provided with swing-out extensions on both sides. These extensions enable the crane trolley to move out on a fixed support 10m over the side of the ship on each side.

The lifting system reduces the risk of the load swinging by means of two double winches and four-point suspension of the roller bracket.

The bracket is suspended from four lifting cables and provides an alternate frame for various kinds of mechanical or fully automatic hoisting apparatus, including TEU and FEU/45ft container spreaders.

The gantry is driven along a rack-and-pinion track located port and starboard on the deck. Additional guidance wheels on the crane tracks ensure precise steering and control. Carrying capacity of each crane is 40t (under the roller bracket), and 32.5t (under the spreader). Maximum lifting height is 30m.