DMS Blackbird has a number of features that make it unique among tugs intended for operation as part of an ATB unit. In the ATB role it will push while engaged in a deep notch in the stern of its barge and connected using the well established Japanese Articouple system. This initial batch of six vessels is required for use on a number of dredging and reclamation projects in Dubai, where they will be matched with purpose built dump barges. DMS has been deeply involved for several years on a number of high profile construction projects in Dubai, working mainly under contract to the Dutch dredging and marine construction specialists Van Oord. Under their managing director Wim Crum, DMS are currently operating a fleet of 12 vessels of various types in Dubai and the Gulf region, which will rise to 20 by the end of this year.

Use of the ATB concept is growing rapidly in the USA, particularly for the transportation of petroleum products on coastal routes, but is little used in Europe with the exception of a few ATB units operating in the Baltic. With the tug engaged in the notch of the barge, using the Articouple system, it is secured by two large horizontal pins protruding from the hull of the tug in the forecastle area and engaged in a series of holes on each side of the barge notch.

This forms a positive connection that allows the tug to pitch but not roll, enabling the tug and barge to behave and handle in much the same manner as a ship, with many of the same advantages. The advantages over a conventional tug and tow include increased speed, improved fuel economy and good handling characteristics.

The Damen Pushbuster 3511 design incorporates all of the features normally found in an ATB tug, a substantial forecastle, appropriate fendering, adequate power, good manoeuvrability and a very high wheelhouse. In addition, it has the ability to carry out normal towage operations over the stern, anchor handling operations, and lifting and transportation duties on site.

Maritime Journal was invited to visit DMS Blackbird , attend the owner's trials in Europort-Rotterdam, and inspect the next two vessels in the series being fitted out in the workshops at Gorinchem. This series of tugs will be fitted out at Gorinchem by Hardinxveld staff because they are too large for the facilities at the home yard.

The first impression is that of a massive vessel. DMS Blackbird is 35.08m in length overall, with a beam of 11.6m and depth (at the sides) of 5.25m. A double chine hull form is similar to that of a large Shoalbuster, incorporating two fixed nozzles set in shallow tunnels. Internal tanks are provided for 380m3 of fuel oil and 45m3 of fresh water. A raised forecastle embodies a heavily constructed mounting for the Articouple system, which is required to accept the massive loadings involved in pushing and controlling a fully loaded barge. The bow fender and protection on the sides and stern are only required to withstand the normal contacts experienced during the initial connection and any other non ATB operations. When secured in the notch of the barge the only contact between tug and barge is via the pins of the Articouple.

The impression of size is reinforced by the massive superstructure, over four decks high and intended to give the tugmaster a view forward over the barge being pushed. From this great height, and thanks to the design of the wheelhouse, there is also an exceptional birds eye view of the afterdeck, winches, crane and rescue boat. The after deck follows the familiar Shoalbuster style, incorporating similar bulwarks, a stern roller, and a work area protected with the usual timber covering.

DMS Blackbird is powered by two Caterpillar 3516 BTA main engines, generating a total of 4,895bhp (3,650kW) at their maximum continuous rating. Power is transmitted, via Reintjes reverse-reduction gearboxes, to a pair of five blade, high performance propellers of 2,700mm diameter, rotating within high performance fixed nozzles. The steering system includes four high lift rudders, two located aft of each nozzle.

Electrical power is supplied by two auxiliary generating sets powered by Caterpillar C-9 TA diesels driving 150kVA alternators producing 230/240v at 50Hz. The main engines and auxiliaries are cooled by box coolers located amidships on either side. A spacious engine room is well laid out to simplify maintenance and has adequate forced ventilation to deal with the needs of the powerful main engines and the Middle East climate.

In spite of the vessel's ungainly appearance, on trials DMS Blackbird performed in an impressive fashion, exceeding the designer's expectations in several respects. The bollard pull achieved at maximum power was 63.4 tons and 61.8 tons at MCR. A free running speed of 11.6 knots was recorded, and the vessels manoeuvrability was outstanding thanks to the choice of four high lift rudders which have a combined area of 20 sq/m. Stability was also outstanding for such a high vessel and the designers' calculations were confirmed with a sizeable margin. Even in a tight turn at maximum power the resulting list was minimal.

Considerable emphasis has been placed on the reduction of noise and vibration and this was immediately apparent throughout the vessel. Extensive use has been made of insulated floors, ceilings and accommodation linings, which has worked well. Ambient noise in the wheelhouse is incredibly low, resulting in readings of approximately 50 decibels.

Deck equipment includes a large Ridderinkhof waterfall style twin-drum hydraulic towing and anchor handling winch, mounted with the lower (anchor handling) drum forward. The anchor handling drum can generate a maximum line pull of 100 tons at 5m per minute and accommodates 600m of 52mm diameter steel wire rope (SWR). For towing, the upper drum has a maximum line pull of 50 tons at 10m per minute and carries a 44mm diameter SWR towline 800m in length. The towing drum is equipped with a horizontal drum head and spooling gear that can be used automatically or manually as required. Local and remote controls enable the winch to be operated locally, at deck level, or from the wheelhouse.

A prominent feature on the afterdeck is the Heila 170-4S-L hydraulically operated deck crane with a four piece telescopic jib. The 170t/m crane is mounted on a high pedestal forming part of the usual winch fairlead and towing bits. Controls for the crane can be operated locally or by means of a portable console via a wireless link.

Other items of deck equipment include a stern roller, manually deployed tow pins and a small Bevini tugger winch with 8 tons pull. The two 375kg Pool anchors are housed in pockets in the bow in the conventional manner and handled by a five ton Ridderinkhof hydraulic windlass.

Fully air conditioned accommodation aboard DMS Blackbird can house up to 10 persons in a variety of cabins, with the Captain and Chief Engineer housed in the superstructure. Facilities include the usual well fitted galley, provision store and sanitary facilities. Accessible within the accommodation, to port and starboard in the forecastle, are the hydraulically operated mechanism for each of the Articouple pins.

The wheelhouse contains all of the usual controls and instrumentation one would expect to find on a twin screw tug of this size on a console arranged in a U configuration. A further, simplified aft control station is positioned close to the rear windows with an excellent view of the after deck. Navigational equipment includes two Furuno Far-2117 radars, a Radio Holland Sea Pilot 75 auto-pilot, a Kotter type magnetic compass and a Furuno GP 150 GPS system. The communications outfit complies with the requirements of GMDSS Area A3 and incorporates three Sailor RT 5002 VHF sets, a Furuno Navtex NAV-NX 700 and an Inmarsat C installation incorporating Single Side Band radio and satellite phone. At the forward end of the control console are four large display screens, two for radar and one for the electronic chart system. The fourth is a multi-purpose display that can also be used in conjunction with specialist dredging and survey systems provided by Van Oord. The computer systems for that facility are already in place in the electrical services spaces beneath the wheelhouse.

Once trials and equipment commissioning are fully completed DMS Blackbird will leave the Netherlands for Dubai to embark on the next stage of the trials process. This will involve integrating the tug and its barge.

The barges are being constructed in China by COSCO Dalian for Van Oord, which is funding the barges and the Articouple systems fitted aboard each Damen Pushbuster. The barges are 147m in length with a beam of 26m and maximum draft of 8m fully loaded. Each barge has a carrying capacity of 10,000dwt and incorporates hydraulically operated bottom dump doors. In order to make provision for the difference in draft of the barges, from loaded to empty, the Articouple coupling has a two stage operating system which when depressurised enables the tug to withdraw the main pins but remain in place whilst loading or discharging takes place. When the ATB is ready to sail, the system is pressurised and the pins locked in position. The entire operation can be carried out from the bridge by one man, and in an emergency the pins can be fully retracted to allow the barge to float free. When the ATB units, incorporating the Pushbuster and the new barges, enter service they will transport sea dredged sand from the Van Oord suction dredgers at sea to the various reclamation sites in Dubai. The dredgers are adapted to enable dredging to continue whilst barges are being loaded on the opposite side to the dredge pipe. When each barge is fully loaded the dredger will continue to operate, taking the dredged material into its own hopper until the next barge arrives. A continual service will thus be provided by this means to maximise the utilisation of the dredger and a constant supply of material to the reclamation site. As work progresses the dredgers are working at ever greater distances from the coast and 30 miles offshore is not unusual. Transportation is currently being carried out by Japanese built and operated tug/barge units but with certification limiting their seagoing capability.

When the Pushbuster ATB units come into service the dredging operation will be considerably more flexible. An important feature of the new tugs and their associated barges is their ability to operate at sea. The Pushbuster has been classed by Bureau Veritas with the notations; I 3/3 (E)*Tug Unrestricted Navigation MACH *AUT, UMS. Likewise the barges carry the BV special notation Tug combined type.

Wim Crum of DMS is delighted with the performance of the new Pushbuster 3511. He emphasises that development will continue throughout the completion of the first six tug/barge units. The vast amount of space onboard is a bonus and can be utilised in a number of ways, which is just one area that will be researched further. Wim Crum is convinced that this is just the beginning for a new design that has considerable scope for future development and that the evolutionary process has only just started.

By Jack Gaston