2-speed Gearboxes

Great advantages and flexibility with 2-speed gearbox systems

Great advantages with a 2-speed CP-propulsion system giving optimised running conditions and considerable energy savings

An energy efficient solution

The 2-speed reduction gearbox is a fully integrated solution to provide the option for two steps of different propeller speed in a hybrid or diesel mechanical configuration. The system is ideal for vessels with variations in power requirements, such as Purse Seiners, Trawlers, AHTS, Seismic vessels, Mega Yachts and Rescue vessels.

Designed for reduced fuel consumption in low rpm conditions
Ideal for configurations requiring power generation from the main engine to the main swithchboard during operation
Ideal for hybrid configurations requiring boost, Power Take Home (PTH) and/or diesel electric running mode

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Reduced propeller rpm - reduced energy consumption

The graphs of Step1 and Step2 in the diagram show the direct effect of reducing the rpm using the 2-speed reduction gearbox.

The configuration consists of a Main Engine (ME) and a generator in PTO-condition. By designing optimum power distribution to the propeller and utilising the remaining power to the PTO, there will be full utilisation of the available power from the Main Engine.
In Step1 the Main Engine run the propeller via the main gear ratio. Simultaneously the Shaft Generator is driven via the PTO gear set. This mode is useful when the power demand for propeller is high and the electric prower production demand is low. In this condition the propeller is highly efficient provided it is optimised for this condition.
In Step2 the Main Engine run the propeller via the PTO gear that further transmit the mechanical power over the PTI gear set -via the main gear ratio to the propeller. Hence, because of the choosen PTO- and PTI- gear ratios, the propeller run at lower rpm, compared with Step1. The condition is typical when propeller power demand is in lower range, and because of the reduced propeller speed the propulsion efficiency is maintained relatively high. The Main Engine run at its nominal speed that make possible a high electric power production by the Shaft Generator.

Odd Lundberg reports about great savings with 2-speed CP-Propulsion System

The pelagic vessel Odd Lundberg, owned by the Norwegian fishing company Odd Lundberg, is designed with a strong focus on optimal working conditions, safety and comfort for the crew. “We are generally very proud of our vessel,” said Mats Lundberg, Odd Lundberg’s skipper. “The performance and the new technology means that we can save time and fuel when we are at sea, and this means more time at home with our families and friends."

The collaboration between the owner, the Karstensens shipyard and Brunvoll resulted in an effective and sustainable solution for propulsion and manoeuvring, based on the vessel's operating profile. The 2-speed propulsion system allows for operation in two speed modes, ensuring optimisation of propeller speed and energy consumption in different operating conditions, a system that has proven to provide significant savings.

"We have used step two of the system to a much greater extent than first expected. We experimented with the plant during trawling, and to our surprise we experienced that trawling by using step two and the 50-60 Hz floating frequency resulted in a fuel consumption decrease by 100-130 litres per hour. With 12-20 hours spent in that condition per day for much of the year, such savings are very positive," Mats Lundberg said.

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Design principles of a 2-speed gearbox

The 2-speed gearbox design and construction is based on the same principles as for all Brunvoll gearboxes, and benefit from a reliable high quality philosophy.

The gear housing is as standard made from high quality grey cast iron, designed with high stiffness and good vibration damping property. However, nodular cast iron is available as option (typical in high Ice class applications).

Gears are designed and manufactured with high precision and optimised for high load, low vibratory excitation and long lasting. Extensive use of sliding bearing (long lasting) for both journal bearings and thrust bearings. Clutches are of high capacity, hydraulically operated, multiple disc, oil lubricated type.

Gearbox fulfil all Class Society requirements.

The gearboxes are designed in 3D and analysed for full load to ensure excellent performance.

The Brunvoll 2-speed gearbox program

Size	Vertical Offset	Power Range kW*

ACG 680 2SP	x	2200 - 4400
ACG 750 2SP	x	2500 - 5200
ACG 850 2SP	x	3000 - 6000
ACG 980 2SP	x	3700 - 10500
ACG 1080 2SP	x	4500 - 12000

Standard range of Brunvoll 2-speed gearboxes. * The power range for each gearbox depends on selected rpm and eventual ice notation.