STENA CALYPSO Oil travels fir st class with C-Max

Specialist niche markets often require new designs incorporating innovative solutions to meet the needs of the trade. One such example is Stena Bulk?s recently introduced combined product/ LPG carrier newbuilding. The second in the two-ship C-Max series, the 10,000 dwt Stena Calypso, made the short voyage from the Polish shipbuilder Stocznia Gdynia to Gothenburg, Sweden, where the naming ceremony took place in October. At the ceremony the ship owner praised the build quality and likened it to that of a Rolls Royce automobile. Stena holds an option on two further vessels at the Polish shipyard.

Chartered out on a nine-year contract to Texaco Eastern Caribbean of Barbados, this products carrier was designed along with its sister ship, Stena Caribbean, for employment in the very sensitive waters of the Caribbean archipelago. The ships form part of Stena?s wide-body project which started with the two V-Max VLCCs. The company plans to expand the project to include new designs in the near future.

Trading as short sea vessels entailing visits to small harbours with limited facilities has focused the design of the C-Max ships on installing numerous redundancy features. These 120m long wide-bodied twins have a beam of 23.8m and an exceptionally shallow draught in order to negotiate the many sandbanks and narrow channels prevalent in this area.

Meeting the stringent environmental requirements of the region has heavily influenced the design, which was undertaken by the group?s own in-house design team led by the project manager Henrik Nordhammer. In addition to a double hull configuration, the ships have been fitted with a pair of azimuthing thrusters which, together with the bow thruster, provides an exceptionally high degree of manoeuvrability enabling the vessels to turn within their own length.

The captain of Stena Calypso remarked at the naming ceremony that handling the ship was a bit like ?driving a sports car? because it is so responsive. It is reported that the vessels can be can stopped dead from full ahead in about 500m.

Classed by ABS, the vessels are manned by a relatively small crew of 13, which reflects the high degree of automation incorporated in the engine room and cargo handling systems. Both vessels are fitted with a free-fall lifeboat of the Frassmer GAR-T 6.0 type with a capacity for 18 persons and are powered by a 17.65kW diesel engine. In addition, there is a six person Frassmer FR 6.1 MOB rescue craft fitted with two 44kW outboard motors and three inflatable RFD rafts.

Propulsion system

This duo represents the first vessels built for Stena that incorporate a diesel electric propulsion system and azimuthing propellers. The prime movers consist of two Wärtsilä medium speed 6R32LND diesel engines each with an output of 2,220kW at 720 rev/min. These power two Siemens generators (type HFJ5 712-16E-OW) capable of producing 2,500 kVA each.

The two 2,200kW azimuthing propulsors are of the Rolls Royce Aquamaster type US 3001/5200 giving the vessels a service speed of 13 knots. The speed is suited to the short distances between the many ports of discharge in the Caribbean area, which makes a faster transit time pointless. The ship has been optimised for quick cargo discharges where the main savings in operational overheads can be achieved. Additionally, a 650kW Rolls Royce Kamewa bow thruster enhances the vessel?s manoeuvrability and facilitates entering and leaving port.

When evaluating a number of propulsor options for the newbuildings, the design team did consider using pods but, at the time of contracting, there were no suitable small units on the market and using one large pod would have been an expensive option.

Auxiliary generators consist of two medium speed Wärtsilä 4L20C diesels with a 630kW output at 900 rev/min and each is coupled to a 750 kVA Siemens generator. An emergency backup power supply is provided by a high speed MAN D2688TE diesel providing a power supply of 200kW at 1,800 rev/min and generating 200 kVA through a Stamford generator. This completes a very comprehensive power plant giving the vessel a wide range of redundancy features.

Siemens also provided a very sophisticated electrical power handling system which can instantly detect any dramatic variations in power supply at either end of the scale and protect the system either from overload or loss of power. This represents the state-of-the-art in power load management involving generators, transformers, frequency converters, rectifiers, inverters and uninterruptible power

supplies.

Cargo handling gear

Designed for operation in the Caribbean, these tankers are unusual in that they can carry 17 segregations of oil products cargoes in conventional tanks (one of which is used for draining cargo), with a total capacity of 12,540m3 while at the same time they have the ability to transport LPG cargoes (such as propane and butane) in two 640m3 cylindrical deck tanks. Much of the LPG equipment was supplied by Hamworthy KSE and included the tanks, all valves and instruments, a cargo heat exchanger, and two four-stage centrifugal LPG cargo pumps each with capacity of 100m3/h at 10 bars.

Additionally, the ships are fitted with a floating discharge hose of 500m length with storage drum for the unloading of LPG cargoes. Designed to load fully refrigerated LPG at -48oC, each vessel?s LPG containment system is fully pressurised so there is no need for onboard reliquefaction as LPG will be discharged at ambient temperature and corresponding pressure.

As a result of their flexible cargo carrying facilities, this duo is able to ship a comprehensive range of products to the many Caribbean islands. Representing a 60% increase in capacity over the previous ships, the two newbuildings have replaced four older vessels and offer the customers a floating pump station facility. The central loading points are Trinidad, the Virgin Islands and Cura?ao from where ChevronTexaco will supply the whole region with petroleum

products.

Many of the offloading ports have few if any shore facilities and discharge will have to be carried out via a floating hose method which includes the LPG cargo. On some of the islands the vessels have to offload several hundred metres from the beach and it is vital that no one failure in the power systems will prevent the vessels from maintaining their position keeping ability. The shallow draught of 6.5m when fully loaded gives these ships the flexibility needed to operate some of the more inaccessible

destinations.

The cargo tanks are epoxy coated and are fitted with heating coils served by deck-mounted manifold valves and 16 deepwell pumps which enable the vessels to achieve quick turnarounds in port. A comprehensive cargo fire fighting system has been installed including a dedicated sprinkler system for the LPG tanks.

Undoubtedly, Stena?s approach to the shipment of oil products is one of providing the oil industry with the highest quality of tankers at an economical cost. This was endorsed in a recent Intertanko circular, which quoted its chairman, Lars Carlsson, stating that “if the charterers were to select the better quality ships instead of stating that all approved ships are equally good, they would create a quality competition”. Carlsson does of course have a vested interest in promoting the highest standards of safety since he is also the chairman and ceo of Concordia Maritime which operates the StenaMax ships.

Power control system

One of the most innovative features onboard the two C-Max ships is the total integration of the shipboard power supply through a sophisticated system developed by Siemens. This PMA 300 power management system (PMS) together with the Siemens integrated automation system (IAS) gives the crew total control thanks to one of the most powerful programmable logic controller (PLC) systems in the market.

At the heart of the system is the first of a new generation Siemens S7-300 series PLC system to perform the PMS function by monitoring the load on the bus bar from each generator. The most important task is supplying sufficient electrical energy during all operation modes and the PLC senses in milliseconds any changes in load and can immediately correct the imbalance thus preventing damage to equipment and provide freedom from interruption.

By using standard components, standard software and modular construction, Siemens has provided a reliable connection between the PMS and the IAS through the bus system. The IAS, which is an open computer based operator system using Microsoft Windows, monitors close to 4,000 data signals and controls the pumps, fans and valve controls in addition to the cargo control for the vessel.

The tankers are also equipped with the Siemens generator power adaptation (GPA) system which is an ultra-fast responding dynamic control system that continuously limits the power consumption of the propeller according to the actual available generator capacity. The GPA is part of the electrical propulsion system and is independent of the PMS.

To facilitate the interface between the engine room and the bridge there are two operator stations in the engine control room and three on the bridge giving fast access to information and enabling quick action to be taken in the event of an alarm or incident.

New StenaMax designs on the way

Stena?s over-riding philosophy for its Max-class ships is to provide the safest and most efficient means of transportation aimed at minimising the risks to environmentally sensitive areas around the world such as Florida, Alaska and the Barrier Reef. While not every risk can be prevented, much can be done to mitigate the consequences of accidents by designing high specification ships which incorporate redundancy features, exceptional manoeuvrability, good containment facilities and integrated navigation control systems.

Having introduced the V-Max and C-Max types onto the market, Stena is currently examining other designs in the Max series, one of which will be aimed at the Baltic Sea trade. The driving force behind this design is the projected expansion of oil exports from the former Soviet Union (FSU) countries which will primarily be shipped via ports in environmentally sensitive areas such as the Baltic Sea or the Black Sea.

In the case of the Baltic, the design parameters will be dictated by the confined waterways, dense traffic, finely balanced brackish water habitat sensitive to pollution and invasive species and sensitivity to air pollution. At present the annual export of oil products from the FSU port of Primorsk is 12 million tons and this is predicted to expand dramatically to 18 million tons in 2003 and 30 million tons in 2005. In addition to Primorsk, the main loading ports are identified as Kaliningrad in Russia, Ventspils in Latvia, Bulinge in Lithuania and Gdansk in Poland. An overland oil pipeline is also being examined as an alternative means of moving the oil to Europe where a deep water terminal capable of accommodating crude and product tankers of larger size can then be used to transport the oil to the Americas.

The Stena Max concept generally aims at being able to safely lift larger quantities of oil through sensitive areas characterised by confined waterways and dense traffic. In this way fewer ships will be needed thus further improving safety in addition to reducing the cost per barrel. These proposed designs may therefore also prove ideal for export shipments from the Black Sea area where navigating through the Bosporus demands that tankers must be capable of securely navigating through the narrow strait and meet the safety and environmental concerns of the Turkish authorities.