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Case study

Clean, quiet and energy-saving cargo handling

The new MultiDocker E-Power cargo handler offers considerable energy savings and reduced environmental impact, with maintained performance. This was achieved by replacing the diesel engine with an electric motor controlled by Emotron AC drives.

[10 June 2011]

Efficient cargo-handling

The Swedish company MultiDocker Cargo Handling AB designs and manufactures cargo handlers based on standard Caterpillar components. The company originates from a shipping company that started to develop solutions to improve capacity and flexibility in cargo handling onboard their ships and in ports. Today’s MultiDocker is designed to handle bulk carriers up to 9,000 dwt. It can be delivered with a maximum reach of nearly 25 metres and with a portal undercarriage with a clearance of up to 5.2 meters to allow trucks and railway wagons to pass underneath. The crane can be equipped with tools to handle various goods, such as timber, scrap, gravel and steel.

MultiDocker cargo handler

E-Power concept with electric drive

The new E-Power concept is a further development of the MultiDocker in which the conventional diesel engine has been replaced with an electric motor. This was to large extent a response to demands for more environmentally friendly solutions. Operating costs and environmental impact are greatly reduced, without compromising on performance or easy handling.

“Using an electric drive system is quite unique for this type of cargo handler and the response has been very positive“, says Per Söderpalm, Technical Manager at MultiDocker Cargo Handling. “The Swedish Energy Agency granted funds for the project, because of its positive impact on the environment through reduced carbon dioxide emissions and less oil usage.”

Energy savings of up to €40 per running hour are achieved, thanks to considerably higher efficiency. An electric motor offers an efficiency of 80-90 per cent compared to approximately 40% with a diesel engine. In addition the electric motor requires less service, reducing also the costs for spare parts and downtime. These savings pay for the higher investment cost in typically two years.

Clean, silent and energy-saving

Replacing the diesel engine also eliminates emission of noise, smoke and pollutants, with positive effects for the environment as well as the working conditions. One unique advantage is that no changes have been done to the user interface or regulators. For the driver, there is no difference between operating the cargo handler with a diesel engine or an electric motor.

An Emotron AC drive controls a 315 kW motor driving the hydraulic pump for hoisting, slewing and grabbing. The AC drive ensures optimized speed depending on the load and offers simple and precise control by regulating the motor speed. The robust construction withstands vibrations and opens up for installation inside the electric cabinet directly on the cargo handler. Liquid cooling means no air openings or fans are required. This helps protect the equipment and reduces noise levels. The technology can also be used for warming up the electronics to make it non-sensitive to low temperatures. Coated boards make the AC drive withstand the humid and salty seaside conditions.

MultiDocker electric cabinet

Cooperation led to successful development

When developing the E-Power concept, MultiDocker Cargo Handling turned to the long-time partner Svenska Lyft, a Swedish expert in hoisting technology offering complete crane solutions as well as service and retrofit projects. In this case Svenska Lyft was hired to design, install and commission the electric drive system including the motor and AC drive. Emotron assisted in calculating and dimensioning the system.