Sophisticated Celtic Explorer Delivered by Damen

Damen Shipyards Gorinchem recently completed the research vessel Celtic Explorer for the Irish Marine Institute of Dublin. This 65 m ship was constructed by Damen in partnership with the Vlissingen yard of Royal Schelde and follows two other important vessels previously delivered to Ireland, the research vessel “Celtic Voyager” and the buoy maintenance ship Granuaille. The work to be carried out by this new vessel will include a National Seabed Survey in Irish waters, perform a vital role in monitoring and recording fish stocks, oceanographic tasks, and wide range of other maritime duties. The new vessel is only the third of its kind in Europe and represents a significant milestone in Irish marine research. The vessel will be named on April 11, 2003 in Galway, Ireland.

Celtic Explorer was ordered in December 2000 to a demanding specification requiring compliance with the most stringent requirements for a vessel capable of carrying out sophisticated fishery, geological and hydrographic research and environmental sampling. The ship had to comply with Lloyds’ Register of Shipping class +100A1, Ice class 1D, IMC, UMS, SCM for a Multi-purpose Research Vessel. It was also to comply with the International Convention on Exploration of the Seas (ICES) ‘209’ report on ‘Silent Fish Surveying’. Celtic Explorer is assumably the first vessel in the world to comply with ICES 209 without any compromise in the required sound frequency range between 10 Hz and 63 kHz.

To meet these requirements special attention had to be given in design, construction, and fitting out to minimise radiated underwater noise, onboard acoustic interference, and vibration. As a ‘multi-purpose’ vessel it was necessary to ensure that equipment and resources could be changed easily from, for example, fisheries work to hydrographical survey.

The transversely framed, welded steel hull of Celtic Explorer is 65.5m in length overall with a moulded breadth of 15.0m, depth of 8.4m and design draft of 5.6m. Ice class requirements are met by reinforcing the foreship with intermediate framing and heavier shell plating. The underwater profile incorporates a bulbous bow, a smooth after body with a single propeller, and provision for bow and stern thrusters. Internal tanks are provided for 400 cu/m of fuel oil and 100 cu/m of fresh water, ballast tanks fore and aft, and a semi-passive roll reduction tank. A double bottom is incorporated between the fore and after peak bulkheads. In order to assist the deployment of scientific transducers a retractable fin keel is provided just forward of amidships. The keel is located in a totally enclosed vertical steel trunk and can be raised or lowered by means of an electrically powered winch controlled from the bridge. Work-, scientific-, and accommodation areas are located on four decks within the hull and the high, extended, forecastle. The work deck aft houses the trawl winches and equipment, deck cranes, and the open stern is fitted with a 600mm diameter stern roller, a trawl gantry and two ‘A’ frames.

At the heart of Celtic Explorer is a sophisticated ‘low noise’ diesel-electric propulsion system that has been specially developed for the vessel with the assistance of Dutch specialist Bakker Sliedrecht Elektro Industrie. A single, specially designed, ‘extremely low noise’ fixed pitch propeller of 3200mm in diameter is directly driven (without gearbox) by two direct current (DC) Indar, low speed, electric motors coupled in tandem. Each of the low noise DC motors has a maximum power rating of 1500 kW at 180 revolutions per minute which are fed and controlled by two Bakker custom build digital drives in a semi 24-pulse configuration together with two double winding transformers with an extra low-noise mode. The vessel can achieve a maximum speed of approx. 15.5 knots at 100 percent ‘maximum continuous rating’ (MCR).

A single ‘high-lift’ ice class rudder is controlled by an electro-hydraulic steering system powered by two hydraulic pumps. Two thrusters are also an important part of the propulsion system. An ‘Elliot Gill’ jet powered by a 720 kW electric motor is installed in the bow and delivers a maximum omni-directional thrust of 6.2 tonnes. A transverse tunnel thruster in the stern, located beneath the main propeller shaft, has a controllable pitch propeller and is powered by a 400kW motor. Power generation for the propulsion system and ship’s main electrical supply is provided by three Wärtsilä diesel engines coupled to Indar generators. Two Wärtsilä 9L20 powered generators produce1620 kW each and a Wärtsilä 6L20 drives a 1080 kW generator, all at 690 volts. Two transformers are used to provide 400 and 230 volt supplies. The electrical system incorporates a sophisticated distribution system that includes a ‘black-out prevention system’ and provides redundancy for all major supplies. An additional emergency generator, powered by a Caterpillar 3306 diesel engine rated at 125 kW, delivers 155 kVA. Special attention has been paid to the mounting of the three main generators, to minimise noise and vibration, and the main drive motors and generation equipment are located in separate engine rooms divided by a watertight bulkhead.

Hydraulic power aboard Celtic Explorer is supplied by a common high-pressure system utilising electrically driven pumps to serve the main winches and miscellaneous deck equipment. Other equipment, such as deck cranes, have their own discrete power-packs. In order to reduce the noise output for the main high-pressure system the hydraulic winch motors are fitted with acoustic attenuators and all pumps and pipe-work utilise resilient mountings.

Celtic Explorer is fitted with a comprehensive array of winches and deck equipment enabling the vessel to handle a wide range of fisheries research equipment and nets, towed hydrographic sensors, and also to carry out other marine tasks over the stern. A total of eleven winches are installed on the vessel. Fishing operations are controlled by a sophisticated trawl winch and handling system, with ‘auto-trawl’ displays and controls on the bridge. Two 30 tonnes split trawl winches located on the main work deck are each fitted with 3500m of wire and have a maximum line pull of 30 tonnes at 78m/min. A pair of 12 tonnes ‘Gilson’ winches are located at bridge deck level. Three net drum winches are provided, two rated at 35 tonnes line pull and one at 45 tonnes is fitted for towing purposes and incorporates a constant tensioning system. The trawl gantry operates in conjunction with a 5.6 tonnes net-sounding winch accommodating 3200m of 11mm diameter wire. A CTD winch with a 6 tonnes line pull contains 6000m of wire and the 4 tonnes ‘Hydrographic winch 2000m of wire.

Three hydraulically operated deck cranes are provided, one with a lifting capacity of 120 tonnes/m and two of 15 tonnes/m one of the latter is mounted on the foredeck. The cranes can also be radio controlled if required. The two stern mounted ‘A’ frames have lifting capacities of 25 and 10 tonnes, both at a working radius of 3m. A lifting frame with a ‘T’ configuration can lift 10 tonnes and is located on the starboard side of the main work deck. The vessel’s anchoring equipment comprises two ‘high holding power’ anchors handled by an electro-hydraulic windlass located under cover, within the forecastle. Warping heads are incorporated for mooring and the windlass drive is fitted with a tension control device. A single, vertical capstan with a 5 tonnes pull is provided aft. Scientific and Survey equipment Among the wide range of equipment installed aboard Celtic Explorer is an ‘Acoustic Doppler Current profiler with a 75 kHz transducer, and Simrad Kongsberg multi-beam echo sounders capable of mapping the seafloor. A Thermosalinograph is carried along with CTD and a Rosette sampler. The vessel is fitted with a ‘Motion Reference Unit’ and extensive metrological equipment. Accommodation Fully air conditioned accommodation is provided for 31 persons, 12 crew and 19 scientists. The facilities for scientific staff onboard include four well-equipped laboratories for chemistry, wet fish research, water sampling and dry procedures. A purpose designed IT room is included and a dedicated scientist’s office and meeting room. Provision is made to accommodate additional scientific equipment contained in laboratory containers on deck. Navigational and communications equipment The Celtic Explorer is fitted out with navigational and communications equipment to a high standard, with an installation contracted out to Irish specialists Barry Electronics. The installation includes hydrographic survey equipment, and other scientific equipment with inputs and sensors accessible via a Local Area Network computer system throughout the scientific and control areas around the ship. The communications equipment fitted complies with the requirements of GMDSS Area 3.