Some of the largest vessels worldwide are using the power of Eaton’s hydraulic pumps for MAN Diesel & Turbo engines. The main special feature of these two-stroke Diesel engines is that they run without a camshaft. Instead, the fuel injection and the exhaust valves are electro-hydraulically controlled in the MAN ME-generation engines, where the axial piston pumps from Eaton Hydrokraft are the hydraulic heart of the system.
The innovative operating mode of the MAN Diesel & Turbo “intelligent” marine engines with full electronic control, means that fuel can be injected continuously and variably as required. Injection pressure and period is fully variable as well as timing of the exhaust valve. Hence injection volume and timing can be adapted perfectly to the operating conditions and the speed of the vessel. The result is significantly reduced energy consumption and emissions.
In view of the large dimensions of these huge machines, every per cent of saving is valuable: The 26 m long engine block has a weight of more than 2,300 tons. The piston stroke is 3 m, and the bore is nearly 1 m. The power output of the 12 cylinder amounts to a massive 72,000 kW, and the maximum torque is as high as 6,700,000 Nm. Considering this data, the power unit is one of the world's largest Diesel engines.
Thanks to the continuously variable injection and valve timing, the new electro-hydraulically controlled Diesel engines are much more fuel efficient and environmentally friendly as they produce much less noxious emissions. So this new technology also helps to ensure the compliance with emission laws.
The largest intelligent MAN marine Diesel engines use Eaton PVWS-500 swashplate pumps with an overall hydraulic power output of up to 2.5 MW. The pumps are driven by the crankshaft from the main engine via a chain drive and gearbox. These supply the fuel injection and exhaust valve actuators with hydraulic energy.
The product portfolio for this application includes axial piston pumps with displacement sizes of 130, 180, 250, 360 and 500 cm3, as well as complete electric motor driven pump packages.
Eaton has done extensive development work to meet the requirements of MAN Diesel & Turbo through the adaptation of these pumps for use with the MAN Diesel engines. Jens NØrby Hansen, R&D engineer at MAN Diesel & Turbo: "Often well-proven standard products have to be re-designed to fulfil our specifications, which are very demanding. In this case, our co-operation with Eaton has led to a new series of PVWS swashplate pumps that have been designed specifically for our electronically-controlled engines." For Markus Meitinger, project engineer at Eaton Hydrokraft, the co-development with MAN Diesel & Turbo is a good example: “This project demonstrates Eaton's expertise to develop tailor-made solutions for customer-specific applications.” Even after the start of production a continuous product improvement takes place, such as for example the introduction of a wear-free swash plate position sensor or the implementation of a more robust proportional valve for electrohydraulic pump control.
What’s more after the commissioning stage of the Hydrokraft pumps the Eaton support does not stop. In every port globally, experienced Eaton service engineers are available to ensure the smooth operation of the ships.
Eaton’s Hydrokraft pumps are also used in industrial applications where high efficiency and reliability are needed. At the facility in Wehrheim, Germany, the Hydraulic machines, especially the axial piston pumps and motors in the range from 66 cc up to 750 cc are developed and manufactured.
For this application, Eaton has initially increased the operating time of the pumps to 32,000 hours. This is necessary because the engines operate 24/7 and a major overhaul of the vessels is only scheduled once every five years. Through continuous product improvement, for example the introduction of the heavy-duty swash plate bearing, this customer requirement has been fully met. The extensive experience of more than 400 units in the field, with over 40,000 trouble-free operating hours, confirms the robustness and reliability of the Eaton Hydrokraft products.
The efficiency of the pumps has also been improved, states Markus Meitinger: "Regarding the high power output of the hydraulic system and the permanent operation under full load, even minor optimizations result in significant energy savings.
Because the vessel's propeller is directly connected to the engine´s crankshaft, the direction of rotation of the engine has to be reversed for running astern. Therefore the Eaton pumps had to also learn to run in reverse whilst being operated in an open circuit. Hence a new valve plate had to be designed to enable backward rotation. Thanks to extensive CFD simulations at the University of Dresden, Germany, and numerous tests at Eaton's labs, this requirement could be met without any loss in efficiency. In order to prevent cavitation, which could occur due to pulling effects of the adjacent oil volume, an additional check valve block was implemented which creates a shortcut to the pump inlet before the outlet pressure is too low. As a result, the Hydrokraft pumps are able to operate in two quadrants even when running in an open circuit.