10 Nov 2014 22:11 (GMT+1)
Twin fin concept wins major maritime award
Innovative fuel-saving propulsion design earns international recognition
Many of today’s modern offshore vessels use azimuth thrusters as their preferred diesel-electric propulsion system.
Azimuth thrusters feature marine propellers in pods which can be rotated to any horizontal angle. This eliminates the need for a rudder and provides greater manoeuvrability compared with a fixed propeller and rudder system.
The downside is that azimuth thrusters can make a vessel more vulnerable, especially in tough Arctic seas and weather conditions, as a breakdown to the angle gears and other mechanical parts usually means a time-consuming and costly period in dry dock for repairs. Conventional diesel-electric or diesel mechanical propulsion with a long shaft and machinery positioned inside the hull is often seen as a more reliable alternative but the gears and electric motor occupy valuable space – and this system is difficult to retrofit on an azimuth-fitted vessel.
To overcome this issue three innovative maritime solution providers – Caterpillar Marine, Odense Maritime Technology and Scandinavian Marine Group – teamed up to develop a pioneering ‘twin fin’ design based on well-proven, robust components and tested technologies.
Their challenge was to develop a robust propulsion system which does not reduce the cargo area, is easy to maintain and has no adverse impact on vessel manoeuvring. The result of their combined endeavours and expertise is the Cat Propulsion Twin Fin System, a diesel-electric solution which helps to reduce fuel consumption and emissions while improving overall vessel performance.
The system comprises a compact electric motor and gearbox configuration connected via a short drive shaft, rotating two controllable pitch-propellers with performance-enhancing tailor-made fins attached to the hull. Major transmission parts are accessible from inside the vessel which makes maintenance easier and removes the need for repairs in dry dock. Another crucial advantage is that the ‘twin fin’ solution can be applied to new-builds, retrofits and conversions in any commercial vessel. It is now available via the global Cat dealer network.
According to propulsion solutions provider Caterpillar Marine the new system offers significant efficiency improvements across a range of key measurable performance criteria. These include increased thrust using reduced power as a result of the large propellers running at low shaft speed. Also, hydrodynamically-designed fins ensure homogenous water flow to the propellers which reduces fuel use, emissions and noise radiation. The twin fin system can be specified with tunnel thrusters, attached either to the fins or the central skeg running between them, to provide dynamic positioning capabilities.
The 3D seismic Ulstein design research vessel Polarcus Naila – owned by Dubai Multi Commodities Centre (DMCC) – was the first commercial installation of the Cat Propulsion Twin Fin System. Polarcus Naila is one of the world’s most environmentally-advanced vessels, combining leading seismic technology with high specification catalytic converters, double hull, an advanced ballast water cleaning system and now ultra-efficient diesel-electric propulsion.
Installation work took place during a six-week propulsion upgrade, which included exchanging two azimuth thrusters with the compact twin fin system, at the Damen Shipyard Group’s ship repair and conversion yard in Amsterdam. As a result of the upgrade the vessel is operating, according to its owners, “with significantly improved earnings potential”.
System developers say the twin fin solution is ideal for various marine applications including seismic research vessels where fuel savings between 30-40 per cent in bollard pull operations can be expected compared with azimuth thrusters. The twin fin technology could also suit cruise ships needing a reliable, low noise system.
“We developed the twin fin system in partnership with Odense Maritime Technology (OMT) and Scandinavian Marine Group (SMG) initially as a solution to make vessels operating in Arctic conditions less vulnerable to damage to the propulsion system,” says Mattias Hansson, senior project manager at Caterpillar Marine. “As the innovative concept has been engineered into vessels, we’ve been pleased to not only see increased reliability but improvements in fuel consumption and thrust performance as well.”
The twin fin system has now received international recognition by winning the Technical Innovation Award at the Seatrade Maritime Awards Middle East, Indian Subcontinent and Africa, Dubai at a ceremony during Dubai Maritime Week 2014. This award recognises advances in marine technology, particularly those making an exceptional contribution to the shipping industry across the Middle East, Indian subcontinent and Africa.
“When Polarcus needed to replace an inefficient propulsion system on two survey vessels, we had every confidence in twin fin,” says Jim Johnson, general manager, Caterpillar Propulsion. “What we could not know was that its benefits would be so quickly recognised across the industry. Describing the award as a magnificent accolade, he adds: “In terms of customer satisfaction, the fact that Polarcus quickly gave the go ahead to retrofit a second vessel speaks for itself.”