Order rush for Voith
It has been a busy few months for Voith GmbH securing two separate orders covering 18 newbuild tugs and their announcement of a new design variant of the Voith Schneider Propeller (VSP).
This month’s Tugs & Towing column reports on orders for no less than 28 new vessels for established operators in Jordan, Mexico, South Africa and The Netherlands demonstrating a confidence in market conditions and belief in the value of fleet renewal.
South African Shipyards based in Durban, have secured the country’s largest local shipbuilding contract with an order for nine new Voith Water Tractors (VWT) for Transnet National Ports Authority, construction spread over 43 months. The order is the largest in the history of Voith marine technology and the tugs will be used at several ports across South Africa.
Eight of the tugs will be identical in construction with a length overall of 31m and beam of 12.5m. They will each be propelled by two VSP 32R5/265-2 propeller units delivering a total output of 5,300kW and a bollard pull of 70 tons. The tugs will be utilised for harbour towage in the ports of Saldanha Bay, Port Elizabeth, Durban and Richard’s Bay.
The ninth vessel will be larger and more powerful at 31.7m LOA and 13.5m beam and an increased bollard pull of 100 tons from two VSP 36R6EC/285-2 units developing 7,800kW in total. This larger version will provide Transnet with a wider escort capability in ecologically sensitive coastal areas on the west coast.
Voith will also supply two turbo and two Renk couplings for each tug. An interesting feature with Voith tugs is the control systems and the eight identical tractors will feature traditional mechanical controls while the larger 100tbp version will be equipped with a Voith electronic steering system. The package also includes local training, skills development and capacity building for Transnet employees.
NINE FOR MEXICO
The second order featuring Voith technology, also involving nine tugs is for the Mexican state-owned petroleum company Pemex (Petróleos Mexicanos). The vessels are intended for operation at a number of Mexican tanker terminals including Madero, Tuxpan and Pajaritos in the Gulf of Mexico and at the terminal of Pemex Topolobampo on the Pacific coast.
The Spanish Shipyard Armon (Astilleros Armón) will provide the project with its own in-house design using VWT configuration, project management, technical advice on location and the supply of all main equipment for the tugs. They will be built at Astimar 20 shipyard which is operated by the Mexican navy (SEMAR) on the Pacific coast of Mexico.
Pemex compiled studies and held talks with other customers including the Panama Canal Authority in determining the correct choice for their requirements. The Voith Schneider technology had proved to be robust with positive effects reported both in terms of running costs and downtime, as well as handling in prevailing strong currents. During the rainy season, the oil transhipment ports located on rivers are severely affected by debris washed into the ocean from inland and the VWT’s low susceptibility to fouling from debris influenced the design choice.
The nine tractor tugs will be identical in construction with a length of 32.5m, beam of 11m and speed of 13 knots. As with the South African order, they will comprise eight tugs with the same bollard pull and one with a slightly higher power output. The eight will each be fitted out with two VSP 28R5/210-2 units producing a total power output of 3,890kW and a bollard pull of 50 tonnes. The ninth vessel will be propelled by two VSP 30R5/250-2 units developing 4,800kW in total with a bollard pull of 60 tonnes.
Voith also recently announced a new VSP aimed at the tug and offshore support vessel market. The new size 34 propeller is significantly lighter and easier to maintain, reducing service times by up to 40%.
The driver for the new model is the changing demand for tugs with a bollard pull of 80 tons and offshore support vessels with an input power of 3,000kW. The VSP 34 variant is optimised for these markets and follows consultation workshops held with customers and confirmation of the survey results with scientific documents.
A six-bladed unit has been selected by Voith, permitting higher power output with a lesser vessel draught and also resulting in reduced vibration. The VSP 34 is also designed for lighter but faster-rotating high-speed diesel engines up to 1,800rpm. Total weight of the new design is as low as 65 tons, the reduction being achieved mainly by redesigning the rotor and the kinetic mechanism used for blade adjustment. The heavy forgings used previously have been replaced by light castings, adapted to the stresses and strains of the VSP. Voith report that a 65% weight reduction of individual components within the rotor casing is possible with this change.
Significantly smaller and lighter bevel gears was a beneficial result of a change in the arrangement of the spur and bevel gearing. By changing the rotor bearing from a sliding bearing to an anti-friction bearing, the breakaway torque of the VSP could be reduced significantly. This development opens up new options for the design of the drivetrain. Further weight reductions resulted from reducing the oil quantity required for the rotor casing of the VSP by approximately 10%. An important new design feature is the second power input/output. For the first time, low-cost hybrid applications requiring tight installation space can now be positioned right at the VSP input.
By Peter Barker
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