Bay-Houston gets its eighth Z-Tech

The new shiphandling/escort tug sailed on 9 June to take up station at the recently commissioned LNG terminal in Cameron, Louisiana, where it will be operated by G & H Towing on behalf of the owners.

The handsome Tristan K and sister tug Hercules were designed by naval architects Robert Allan Ltd of Vancouver, with significant input from Mike Nigro, vice president of engineering at G & H Towing, and his team. The Z-Tech 7500 design builds on the international success of its smaller cousins, the popular and well-proven Z-Tech 4500, Z-Tech 6000 and Z-Tech 6500 Classes. Since their introduction to the world market only a few years ago there are now a total of 50 Z-Tech tugs operating in South-East Asia, Australia, the Middle East, in the Panama Canal and at US Navy bases in Japan and the United States.

Tristan K and its recently delivered sister tug Hercules are classed for both harbour and coastal towing, tanker escort duties, and fire fighting. The tugs were built to comply with the ABS class notation – A1 Towing Service, AMS, Escort, Fi-Fi 1 and measure 30m in length overall with a beam (moulded) of 12m and maximum draft of 5.18m. Dedicated integral tanks can accommodate 169 cu/m of fuel and 24 cu/m of fresh water.

Compared to the previous six Z-Tech 7500 tugs for the same operator, Tristan K and Hercules are equipped with a different propulsion system and towing winch. The propulsion system comprises a pair of MTU 16V4000-M70 diesel main engines, each rated 2,240 kW at 2,000 rpm to drive Rolls-Royce US 255 azimuthing propulsion units. Power is transmitted to the units via hollow in-line driveshafts, thus reducing weight and torsional vibration. Each propulsion unit incorporates a 2,800mm diameter propeller rotating in a thrust augmenting nozzle. This combination delivers a bollard pull of 73 tons ahead and a free running speed in excess of 13 knots, fully satisfying the owner’s performance specification.

The configuration of the Z-Tech 7500 class vessels is very similar to that used for the smaller tugs, sharing the unique ‘double ended’ style. Another unique feature of the new vessels is the provision of a docking skeg located forward of each propulsion unit, to reduce dry docking time and costs.

The tugs tow from a Markey electrically driven, single drum, winch model DESF-48 200HP. A line pull of 207,000 kg can be achieved at speeds of 4m/minute or 1,290 kg at 204m/minute. The single drum accommodates a 213m towline of 72 mm diameter synthetic rope.

Electrical power is provided by a pair of John Deere 6081-AMGK75 auxiliary generators, each rated 185kW.

The tugs have a full Fi-Fi 1 rating in accordance with class notation requirements. Two remotely operated monitors are located on the superstructure and supplied by two fire pumps, each rated at 5,300 gallons per minute and driven by independent diesel engines. A water spray ‘self protection’ system is also included.

Accommodation is provided for a crew of six persons, in modern, well equipped facilities.