‘Seychelles Paradise’ – a coastal oil/LNG tanker designed with ‘green’ credentials

Lindenau says that the Government of the Republic of Seychelles passed a directive concept to improve their maritime infrastructure and to protect their sensitive islands against oil pollution and gas accidents. The recently-delivered M/T Seychelles Paradise is part of this concept and was delivered from Lindenau Shipyard to Seychelles Petroleum  (Seypec) in October 2009.

Since 1976 Lindenau Shipyard has specialised in the design and build of double hull tankers. The yard claims to be well known for its innovative ideas for optimising economy, safety and environmental compatibility. These concepts have been developed in cooperation with German research institutes. The resulting ships have built up a global reputation, thanks to some 14 international awards. Parallel to the newbuilding activities Lindenau Shipyard has engaged in repair services for ships on their passage through the Kiel Canal.

Seypec is the national oil and gas company of the Seychelles and owns what is said to be the most modern tanker fleet in the Indian Ocean, comprising six double hull tankers, all featuring advanced technology. These ships are intended to ensure a safe and ecological domestic supply and in addition participate in the global seaborne market for oil and chemicals.

Lindenau says that as of October 2009 the global market for oil-carrying coastal tankers below 5000 dwt consisted of 3578 ships, aggregating to 8,3 million dwt. One important characteristic of this fleet segment is its generally high age profile (39% are older than 30 years) and the very high proportion of single hulls (78% of the fleet).

International regulations encouraging the use of double hull ships, and setting timescales for the phase out of single hulls (MARPOL Annex 1) are only mandatory for ships larger than 5000 dwt and generally do not affect the smaller size segment. However if tankers in the size range 600.-.5000 dwt intend to transport heavy grade oil, defined as crude or fuel oil with density > 900 kg/m³ or viscosity at 50°C > 180 mm²/s, or bitumen-tar emulsions, MARPOL A1-R.21 has required a double hull since 2008.

Seychelles Paradise was developed for the following service profile:

a. to supply the islands of Seychelles with oil and liquefied gases (LPG);
b. to supply foreign vessels with bunker fuel at the anchorage of Victoria;
c. to serve as a crew training ship for the education of officers and sea men for the national fleet.

The ship is suitable for the transport of oil and products with flashpoint < 60°C, maximum density 1,025 t/m³ and maximum filling temperature 60°C.

Six epoxy-coated cargo tanks with smooth surfaces are provided to ensure short discharge times and minimum slop residues. A double hull protects all oil cargo tanks and fuel service tanks. Four frequency-controlled screw pumps allow a discharge rate up to 600 m³/h.

Specificially for the bunker service three calibrated cargo flow meters, two oil spill recovery units, special fenders, a manifold, crane of 5 t at16m capacity, and recessed bridge wings are installed.

Furthermore a 118 m³ LPG-plant is supplied, consisting of two tanks with 7 bar working pressure, two pumps of 20m³/h and a one-grade piping system with crossover.

The ship has a redundant propulsion plant consisting of two main engines, two controllable pitch propellers and two spade rudders. An electrically-driven bow thruster is installed. This concept ensures a high level of manoeuvrability, soft power control and maximum protection against failure.

The design was optimised for good manoeuvrability, with a turning circle of about 126m recorded on sea trials. This is 40% of the IMO maximum limit. The advance distance was measured at 185m, corresponding to 64% of the IMO-limit. The yard considers these values to represent an outstanding result for a bunker ship qualified for ship-to-ship-berthing.

Seychelles Paradise is built with a high hydrostatic stability in order to allow a flexible bunker service with changing draughtsts and slack cargo tanks; to avoid roll resonance in the Seychelles sea (area 69); and to compensate the top weights of a large deckhouse and the LPG tanks.

The main dimensions are intended to provide an optimal compromise to ensure a superior speed-power-ratio at the same time as a high hydrostatic stability.

Considerable design effort was invested to achieve minimal fuel consumption with low emissions. Under trial conditions, a speed of 10.2 knots at 57% MCR was recorded, which Lindenau says represents the best of the HSVA data base for ships with equal or higher breadth (scaled to the same displacement).

During the design optimisation process the power demand for propulsion and ship’s service was reduced by about 20%, which according to the yard represents a significant reduction of fuel costs during the lifetime of the ship. The slender hull form, CFD optimisation of ship lines and shaft inclination, high propeller diameters and the power management system contributed to this result.

For the main engines a NOx emission of 5.6 g/kWh was measured, amounting to 56% of the actual IMO Tier 1 limit. Lindenau says that this means the emission targets under IMO Tier 2, which will become mandatory for newbuildings constructed on or after 2011, are fulfilled with a reserve of 28%. For the genset engines a NOx emission of 8.9 g/kWh was measured, which is 85% of the actual IMO Tier 1limit.

For Seychelles Paradise the periods of roll (< 7,6 s), pitch (5,6 s) and heave (5,1 s) were calculated from typical loading cases and found to have at least 15% margin to the most probable wave periods according to global statistics. Roll damping is assisted by large bilge keels and high GM values, meaning that the yard expects excessive heave or pitch motions to be highly unlikely.

The demands of a bunker service with flexible cargo tank fillings means a high longitudinal strength is required. The issued permissible bending moment is 62 % above the minimum classification requirement (hogging, sea condition) and the permissible shear force exceeds the minimum requirement set by class society G by some 87%. These values provide a comfortable margin, allowing flexible service with various stop-overs for discharge of small quantities of oil during a round trip.

Lindenau considers that for a training ship, minimum noise and vibration levels are important. Resiliently mounted main and auxiliary engines, propellers with low pressure pulses (load = 120 kW/m²) and an optimised design all help to achieve this target. In 75% of the accommodation rooms the measured sound pressure levels were at least 5 dB(A) lower than the limits according to IMO resolution A 468 (XII).

Integrated computer systems for cargo handling and monitoring, engine control, power management and navigation are provided, and are included in the crew training programme to minimise the risk of human error.

The electric load balance was tailored to simultaneous operation of four cargo pumps at full load with two genset aggregates running and a surplus of about 15%. Furthermore a stand-by generator of equal size and an air-cooled harbour/emergency genset of 75 kVA are installed.

During long-term measurements during the delivery voyage an average electrical power demand of 75 kW was measured, which is about 30% less than predicted for at-sea use.

 Accommodation is provided for up to 15 persons in eight rooms with individual sanitary compartments. A catering area including mess room, galley, and provision storage, and a combined office/dispensary are located at poop deck level. A single-duct air-conditioning plant and a separate AC cabinet for the engine switchboard room is installed.

The machinery installation includes two Volvo Penta main engines, type D16 MH (each rated for 473 kW @ 1500 rpm) with box coolers, two gear boxes with 1:5.93 reduction ratio, two CP propellers of 2,0m diameter, three gensets MAN D2876 LXE 301, 400kVA  @ 1500 rpm, one harbour/emergency genset Cummins 6BT 5.9-D(M) rated 75 kVA @ 1500 rpm, two ballast pumps of 100 m³/h, main  and emergency fire pumps, an MGO separator, a freshwater generator and a sewage treatment plant.

The cargo system includes four frequency-controlled screw pumps of 150 m³/h @ 8.5 bar, three manifolds (2 x DN 150, 1 x DN 200), stainless steel pipes, remote operated valves for discharge- and drop lines, a radar ullage system, filling alarms, high-velocity PV valves and portable tank washing machines.

For fire fighting, a foam plant with three monitors, a waterspray system and a powder extinguishing plant for the LPG-area are installed.

The ship is classed by Germanischer Lloyd to + 100 A5 RSA (50) Product Tanker, equipped for the carriage of oil products in bulk, equipped for the carriage of liquefied petrol gas in bulk, + MC AUT

Acording to the yard, Seychelles Paradise was subject to an extensive optimisation process during the design phase resulting in a comfortable excess of many contract requirements. Lindenau adds that the unique qualities of the ship with regard to cargo flexibility, redundancy, manoeuvrability, fuel-saving, safety and ecology were created in a trustful teamwork between the yard, Seypec and the German research institutes. The result is claimed to be a trend-setting pilot project for the safe, ecological and economical transport of oil and gas, which Lindenau believes will probably be copied for domestic services elsewhere.

Principal particulars

Length overall: 67,8m
Breadth: 13.2m
Depth: 5.2m
Draught max: 4.2m
Deadweight dwt.1785t
Trial speed @ 100% MCR: 11,6 knots
Oil cargo volume: 1700m³
LPG volume (100%): 118m³
Tonnage (London): 1545 gt
Main engines: 2 x 473kW @ 1500 rpm
Gensets:  (3 x 400 + 1 x 75) kVA @ 1500 rpm
Propellers: 2 x CPP, dia 2.0m, 253 rpm
Bow thruster (el. driven): 150kW
Cargo pump capacity: 4 x 150m³/h at 8,5 bar

For general arrangement diagram, click here.