TWO industrial gear units from SEW-EURODRIVE's X-Series are providing reliable power to a Tobies gantry crane used for container handling at the port of Germersheim, located on the Rhine River in Germany.
The 126m-long, 680ton gantry crane manufactured by Tobies Förder-und Krananlagen can transport loads of up to 65tons, and therefore requires solid, powerful drives for its hoist.
The drive unit consists of two AC 690V motors with two X3FS250.B coupled industrial gear units manufactured by SEW-EURODRIVE. These allow the hoist to operate at speeds of up to 80m.min. Both drive units for the vertical motion are synchronised using an electrical shaft.
For this purpose, encoders mounted on the motor shaft and on the gear unit's output axis measure the number of revolutions. Both measured values are monitored in the frequency inverter's controller.
When deviations in the encoder values are measured, it is assumed that the machinery has broken down. If this occurs, emergency disk brakes with a powerful holding torque of over 100kNm are activated.
These hydraulic brakes are released as soon as the crane is supplied with current. In case of a power failure, they apply immediately. The brake unit can also be released manually.
When it comes to safety, Tobies prides itself as one of the pioneers in the field of crane construction. The Speyer-based company's philosophy is to supply their customers a solid end product with sufficient reserves.
Each of the motors on the drive unit for vertical motion has 315kW of power. Each of the two gear units has a nominal power of 477kW and a nominal torque of 175kNm.
After a certain number of operating hours, maintenance is performed on the large gear units at prescribed intervals. The oil level is checked, and if there are signs of wear, the gear oil or oil seal is replaced. The gear unit is connected with the winding drum via a pin coupling, which was pre-installed by SEW-EURODRIVE.
The doors of a container that is mounted on a truck must always be located at the back. However, when they are unloaded from the ship, they are often in the wrong position. In that case, the containers must be turned. The entire machine cabin can be turned 280 degrees to allow trucks and trains to load properly.
This is the reason why it is mounted onto a movable, rotating assembly. Tobies selected SEW-EURODRIVE for more than just drive units for vertical motion. The motors used for the two drives on the rotating assembly are K107 bevel-helical gear motors, with a nominal power of 7.5kW, are also monitored in two ways.
The motors have reinforced insulation and are equipped with strip heaters, a temperature sensor and a brake. The complete drive technology system on the crane represents a valuable investment.
The 690V power cable runs along a trailing cable installation. A high voltage level was chosen to keep currents from being too high and so that the cable would not be overly thick. The cables were laid on cable racks in the crane's crosstie bars, which can be reached from the inside at all times. The gantry crane's trolley runs along the train tracks and can reach a maximum speed of 100m.min.
For the travel drives, Tobies used 24 SEW KT127 bevel-helical gear motors, each of which has 22kW of power. Four of the drives were equipped with an EV1C encoder. The encoders measure the distance and angle of the gantry crane's movement. The measured values are then processed in the inverter control.
The energy is transferred by cable to the trolley bridge and then sent via hanging cable to the E-container, which is located above the machine room. The machine room contains the control cabinets, where supplies for the cabin and trolley are stored.
Other components that are needed to operate the motor include the brake rectifier, the stator heating, the accelerator coil, and the holding coil. When the outside temperature drops to 5°C or lower, the machines are heated from the inside.
Additional drives from SEW-EURODRIVE allow for trolley travel by the machine cabin and E-container on the gantry crane (towards water or land). In this case, four KT127 bevel-helical motors with 37kW of power were used, two of which were also equipped with the EV1C encoder. The travel drive and the trolley drive feature a hollow shaft with patented TorqLOC hollow-shaft mounting system from SEW-EURODRIVE.
This non-positive clamping joint has an excellent tolerance range and can also be disassembled easily. This makes it an easy-to-service alternative to traditional connection methods, such as keys or shrink disks.
The trolley travelling winch can reach a maximum speed of 150m/min. The electric cables are laid as a trailing cable installation on the crane boom. All of the cables glide over plastic rollers, allowing for quiet operation. Rubber expanders are used to keep an equal spacing between the anchorage points. In the unlikely event that the expanders break, emergency release cords made of steel prevent the cables from being affected.
The crane operator sits in a cabin underneath the machine room, which provides the best vantage point to see what's happening on the ground below. The loading yard is well-lit at night. As the container stacks grow in size during loading and unloading, they can sometimes obstruct the view of adjacent containers.
To solve this problem, the crane operator can move the cabin back and forth to get a better view of the containers. The travel drive that is used in the cabin is a decentralised gear motor with an integrated frequency inverter from SEW-EURODRIVE's Movimot series.
The hoists / gripper that are used to handle ISO-standardised containers are called spreaders in the port terminal business. These are telescoping frames, which can be adjusted to the length of the container. A spreader has four journals, which engage the four upper corner fittings of the container and are locked using a positive connection (twist locks.)
This powerful gripper is suspended from a pulley block with eight steel cables, located underneath the machine room. The load is weighed at the anchorage point. A tension load cell is used to ensure that the container crane's maximum load of 65 tons is not exceeded.
The average total weight for 20foot containers is 24tons or less, and 30tons or less for 40foot containers. The spreaders that are used are also suitable for twin operation, which allows for simultaneous handling of two 20foot containers. Twin operation speeds up the loading and unloading of ships.
Compared to the gantry crane's driving operations, the positioning the containers is time consuming. It also puts a heavy strain on the drive motors, as a result of short high voltage pulses of up to 2,5kV occurring. Special preventive measures using inverter output filters (voltage peak limiters) were required to provide reliable prevention against overvoltage in the motor cables.
Tobies and SEW-EURODRIVE have worked together for four years.
Managing Director Andreas Tobies is very satisfied with his drive supplier: "SEW-EURODRIVE is very flexible with regard to our specifications. If anything unexpected occurs, their first priority is finding a solution for the problem. The bureaucratic aspects are taken care of later."
This sentiment is echoed by SEW-EURODRIVE sales engineer Jürgen Holzer. "We have had a solid collaboration with Tobies, one which is founded on mutual trust and a cooperative partnership. The Tobies company can rely on their drive manufacturer in every respect."