The 2017 Annual OSJ Conference, Awards & Exhibition saw a number of presentations from thruster manufacturers highlighting recent developments and new products, including some unique thrusters from Wärtsilä
Wärtsilä Marine Solutions presented its new generation of retractable thrusters at the conference, of which eight examples have been supplied for Heerema’s new semi-submersible heavy-lift vessel, Sleipnir. Heerema was looking for a retractable thruster that could be maintained without drydocking. The dynamic positioning performance required of the thrusters meant a tilted shaft was required. No existing solutions met this requirement.
Accurate positioning of the vessel will be ensured by eight 5,500kW Wärtsilä underwater mountable thrusters, four of which are also retractable. Wärtsilä developed the four forward retractable thrusters specifically for this project and has given them the type indication WST-65RU. They feature a unique combination of retractable and underwater mountable functionality. The thrusters installed at the aft of the vessel are WST-65U underwater mountable thrusters. The outboard parts of both types are completely interchangeable.
The underwater demounting capability of all eight thrusters means that drydocking and the use of an underwater habitat is necessary in order to exchange the thrusters. The thrusters are equipped with Wärtsilä Oceanguard anti-pollution face type seals, which have been selected primarily because of the challenging environments in which these thrusters will operate.
Apart from maintenance/overhaul by means of underwater thruster exchange, Heerema also needed the thrusters to retract quickly, with automated retraction/deployment in less than 10 minutes. A high level of reliability and redundancy were essential as was ease of operation. The vessel has a speed of 11–12 knots with all eight thrusters in operation.
Schottel also presented its new generation of environmentally friendly thrusters at the conference. Sales manager Joachim Müller presented the EcoPeller, which is optimised for efficiency and reduced fuel consumption, Leacon sealing system and Combi Drive designs. He described Leacon as a triple sealing system and an integrated alarm. It is DNV GL Clean Design certified.
Rolls-Royce’s latest carbon fibre Azipull 65 thruster could bring benefits to the tug and anchor-handling tug/supply shipbuilding market in the form of weight savings, the UK-based company believes. The Azipull Carbon 65 (AZP C65) steerable thruster is a low drag, high efficiency propulsion system that has been developed with course stability and low noise and vibration levels as key elements of the design. Rolls-Royce says that, while the new product has been developed primarily for the superyacht market, it is also applicable to workboats, and the company is exploring opportunities in the tug and offshore vessel sectors.
Gary Nutter, executive vice president for propulsion and engines, explained, “The unique challenge for this product and application was to make it significantly lighter, whilst retaining power output. Working with new materials and developing a brand-new supply chain, we have managed to develop a unit weighing 2,800kg and delivering 2MW of power.” The propulsion unit will also require minimal maintenance, with routine preventative checks and maintenance instructions provided to operators. The shaft seals are replaceable when required, but no other major maintenance is required, the company claims.
Among recent additions to the range of thrusters on the market is Steerprop’s CRP ECO product line and the new, compact Steerprop CRP ECO LM propulsor with integrated vertical permanent magnet (PM) motor. The LM model is said to offer reduced lifetime costs, improved fuel efficiency and low vibration and underwater noise levels, while its compact construction makes installation and maintenance easier and maximises onboard comfort.
Steerprop has also recently launched a new generation of ducted azimuth propulsors with an upgraded design and improved technical features. The company claims that the new generation of Steerprop propulsors offers greater agility and endurance in a compact package, with a lighter-weight construction, cast steel housing and enhanced robustness.
The unit is designed for hydrodynamic optimisation to achieve improved free-running efficiency and fuel economy, with a more slender body, a smaller hub ratio and a new high performance HJ4-nozzle design. The HJ4-nozzle guarantees superior bollard pull and allows optimal nozzle positioning. Traditional sacrificial anodes have been replaced with a new, non-flow disturbing shape cast anode.