A tunnel boring machine moves deep slowly through the earth. The entire tunnelling machine is exposed to mechanical loads, dirt, moisture and sometimes high temperatures. A number of harnessed plastic energy chains are used for the energy supply for the segment lining and in material handling. They are exposed to conceivably harsh environmental conditions in a small installation space.
The tunnel boring machines from Herrenknecht AG, Schwanau-Allmannsweier are always tuned to their respective tasks and geological and hydrological conditions. In 2010, Herrenknecht was commissioned to build a tunnel boring machine (TBM) in order to build a traffic tunnel, "the Port of Miami Tunnel", in the port of Miami. This was to ease the traffic of almost 16,000 vehicles every day that clog the roads to and from the cruise and freight port in Miami. The solution: a Herrenknecht tunnel boring machine of the "earth pressure shield" type. The entire machine has a weight of 2,500 t; its length is 110 m. While all tunnel boring machines are custom-built, the one thing they all have in common is that they are usually in almost continuous operation from the day of commissioning until they breakdown, which entails high demands on load resistance, also in terms of the energy supply systems. These are needed because a whole range of different crane systems are used in the tunnel boring machine for a wide variety of tasks. These are the material handling cranes which transport for example pipes, cable drums and other workshop equipment from the utility vehicles to the respective application site. "These cranes for pipe laying, cable drums and workshop equipment play an extremely important role in the overall process," explains Dietmar Stahl, team leader for crane construction for traffic tunnelling. "They are responsible for the respective supply." For the extension of the conveyor belt, a workshop crane or conveyor material crane is subjected to the heaviest use.
All the above crane systems are equipped with two or three pre-assembled energy supply systems from igus for longitudinal and transverse travel. One is the energy chain system E4.1, which is openable from both sides and is very robust and protects the inserted cables.
Not only in material handling, but also in the erector, which is responsible for placing the tubbing, robust energy supply systems prove their strength. For the tubbing segment lining, immediately after the drilling process, the tunnel is supported permanently with the tubbings in the form of a ring to protect the shield skin. The tubbing segments are positioned on the tunnel wall by means of an erector, a remote manipulator, held mechanically or by vacuum, and then screwed. The erector's radius of action of +/-200° is achieved with energy supply systems of the E4/4 series with reverse bend radius (RBR) and installed turned 90°.
he chains of the igus E4/4 series are also characterised by high stability and torsional rigidity. They can be opened at both ends and can be equipped with various mounting brackets. Long unsupported applications, also mounted on the side, are implemented just as reliably as gliding applications. The E4/4 plastic chains prove themselves mainly in harsh environmental conditions.
In addition, pre-assembly was carried out with the most flexible from igus.
Not only the driving machine itself, but also the components in the background had to be designed precisely for the respective requirements on site, so that the tunnelling work took place within the given time frame. As described above, this applied to a large extent to the energy supply systems of the series E4.1 and E4/4, which have proven themselves in the crane systems and, above all, in the erector, directly behind the drill head, despite the huge dirt accumulation. "Durability and stability play an extremely important role," says Dietmar Stahl. "The energy chains of igus convince us in material and design. We have been working together very successfully for several years. " The Miami Mammoth project also includes the pre-assembly with the most flexible "chainflex" signal and power cables from igus. The supply from a single source with system guarantee is offered by the company under the name "readychain". Dominik Küntzler: "This is how we save a lot of assembly time, among other things. " Even if only a small amount of installation space is available, all cables are protected. The switch cabinet can be installed separately. "This gives us the flexibility we need for this complex task. “