Electrically Powered RTGs Catching on Worldwide
Claus Burger, Global Market Manager Container Handling Conductix-Wampfler

Several thousands of tons of CO2 have been saved in ports worldwide in recent years. This has been achieved primarily by the conversion of the indispensable rubber-tired gantry cranes (RTGs) from diesel to electric power. For years, cranes have been a major cost driver and a burden on the CO2 balance for port operators. They often represent half of the total fuel consumption of a port and have a significant environmental impact. New RTGs are, therefore, often fully electrically powered and equipped with the associated technologies during manufacturing. Conductix-Wampfler has several solution variants for RTG electrification both for the conversion of diesel-powered RTGs as well as for installation in new E-RTGs on the market. “Drive-In L” technology even comes entirely without pneumatic or hydraulic components.

According to Claus Burger, Global Market Manager Container Handling, Conductix-Wampfler, the conversion of RTGs from diesel to electric power results in savings of up to 95 per cent of diesel consumption. During normal operation, E-RTGs no longer need the diesel engine, only using it when driving from one container lane to the next or into the maintenance area. This pays off, says Burger: “If you compare diesel costs to the projected electricity costs for RTGs opposite, the savings that can be achieved by conversion become obvious. The conversion costs pay for themselves after a short time.” In addition, avoiding diesel operations reduces maintenance and operating costs by up to 70 per cent and the CO2 emissions and noise pollution in the port area decrease.

There have been enough arguments to have caused a re-evaluation. Today, not only older RTGs are being converted worldwide, but also new cranes are also being designed from the outset with the appropriate components for an E-RTG system. But which technologies are the most appropriate for which requirements?

Different Solutions for Each Individual Application Area
Conductix-Wampfler offers various systems for the electrification of RTGs for terminal operators. For example, electrification can be done using motor driven cable reels or via conductor rails with plug-in or drive-in systems. With drive-in systems the connection between the RTG and the conductor rail is established automatically, doing away with the manual plugging and unplugging of plug-in systems. The Drive-In L (linear) system is a fully electrically powered system without any pneumatic or hydraulic components.

Electrification with Motor Driven Cable Reels
A motor-driven cable reel is installed to provide an RTG with electrical power. “Since each RTG is a different system and acts independently, Conductix-Wampfler offers basically two technical solutions,” says Burger. Both applications are precisely tailored to the individual processes in the ports where they are used.

On one hand, Conductix-Wampfler provides modular motor driven cable reels with a permanent magnetic coupler, which are plug-&-play systems consisting of interchangeable electrical and mechanical components. On the other hand, terminal operators can take advantage of a permanently controlled motor driven cable-reel system with several control units, either in the form of hardware with pre-programmed sequences or a software program that can be integrated into existing PLC controls. In such cases, built-in video cameras and optical sensors control the movements of the RTG.

“Conductix-Wampfler systems cover both low- and medium-voltage applications,” says Burger. A glass-fiber core and transmitter can be integrated into the drum or cable. “One or more container blocks in the same lane can be supplied with the same motor driven cable-reel system,” adds Burger.

Conductor Rail Systems
The conductor rails are attached to a steel structure set on a concrete base. Depending on the port operator, this can be floor-mounted or embedded in the terminal floor. The conductor rail can be installed at different heights, which increases flexibility. The electrical energy is taken from the conductor rails by a current-collector trolley that moves back and forth along the steel structure. A cable with a plug connector provides a direct connection between the current-collector trolley and the RTG. “As safety aspects play a crucial role in ports, we use guided contacts that ensure that the power supply at the plug is interrupted when the connection is not activated,” says Burger. Two connectors are mounted on the RTG, one on each side, to guarantee the required flexibility of the RTG. Limit switches are installed on the current-collector trolley to prevent the crane from leaving the block in electric mode.

Drive-In System Extension for Container Cranes
In the case of the plug-in solution with conductor rails, the RTG has to be unplugged and then plugged in when moving between container lanes. Conversion to an E-RTG with the drive-in system makes this manual step obsolete, because the Conductix-Wampfler system extension dispenses with the manual plugging-in of the RTG to the current-collector trolley of the conductor-rail system. Instead, the current-collector trolley automatically connects into the guide rails of the steel structure and the current collectors are securely guided into the conductor rails when the RTG crane drives into a lane. This drive-in solution saves time and energy, thus increasing the efficiency of a terminal while also reducing the environmental impact.

The drive-in system is already tried and tested in use: since 2009, E-RTGs fitted with drive-in equipment have been plying the 32 container aisles of the Shekou Container Terminal in China. “With the electrification of RTGs we wanted to fulfill our responsibility to the environment,” stresses David Wan, Deputy General Manager & COO of the Shekou Container Terminal. But that’s not all: the port facility regularly experiences high wind speeds. “It is not unusual for us to have eight typhoons in a year,” says Wan. This is why the Chinese were looking for a solution that not only saves fuel and CO2, but that also reduces the number of hazardous tasks for employees, such as those related to energized cables.

The new Drive-In L Solution
Conductix-Wampfler has further optimised the drive-in solution in the meantime since its first installation in 2009. The new Drive-In L system has an extremely compact design, requiring absolutely no pneumatic or hydraulic components and is currently the lightest on the market. This means it can be used with any RTG type, even with those, which have where there is little room for additional components. The first RTGs equipped with Drive-In L are being used in the United States, among other places. In Savannah, Georgia, this technology feeds four RTGs at the Garden City Terminal over lengths of 165 meters each.

With its compact design, the Drive-In L solution can easily be fitted to both sides of the RTG, regardless of the position of a diesel engine or generator, which currently makes it the most flexible solution of its kind on the market. The time it takes for the RTG to drive in or out of the Drive-In L system is less than 20 seconds. A short entry zone also makes it possible to operate the RTG electrically right from the first row. In addition, it guarantees the compensation of tolerances caused by driving the RTG into the container block, or by raising and lowering it. The sequence with “Drive-In L” is fully automatic and is controlled exclusively from the cabin of the RTG. This means that ground personnel are no longer required when moving between blocks, which has the advantage of making work in the terminal safer.

Potential for Future
Conductix-Wampfler recently undertook several major orders for the electrification of RTGs in China, Turkey, USA, India, Columbia, Togo and Ecuador. There are now more than 1200 Conductix-Wampfler E-RTG systems in use worldwide. The demand for drive-in conversion kits has also increased significantly in Europe. As the demand for E-RTG technologies increases, the costs for terminal operators and the overall environmental impact are both decreasing. Thanks to E-RTG technology, there have been worldwide savings of more than 71 million Euros, and more than 51 million kg of CO2 emissions have been prevented.

“The advantages of electrically powered RTGs are obvious. We therefore assume that in the future diesel-powered cranes will only be used in the future where an electrical power supply is not technically feasible,” says Burger with states convincingly. With the innovative Drive-In L system, Conductix-Wampfler has paved the way and emphasized its own pioneering role in this future market.