Optical communications technology for tunnel-boring machines

Belden Inc. has supplied optical communications technology from its Hirschmann brand for Herrenknecht tunnel-boring machines (TBMs) used to construct the Katzenberg rail tunnel in southern Germany. This tunnel, which is scheduled to go into operation by the end of 2012, will form part of the new high-speed link between Karlsruhe and Basel in Switzerland.

Two identical TBMs were used to cut twin 9385m holes through solid rock. Each of these machines is 230m long and weighs 2500 tons. Because the machines have special data communication requirements, an optical Profibus network incorporating Hirschmann OZD Profi 12M fibre interfaces were installed.

Wayss & Freytag Ingenieurbau was responsible for planning and implementing this network. Project Manager Roberto Piacentini explains: "The physical properties of optical cables mean that there is no electromagnetic interference, which is extremely important in view of the long transmission paths along the power cables of the tunnel boring machines."

Initially 2km long, the fibre optic cables were gradually extended to a length of 10km in order to keep up with the progress of the TBMs. Both ends of the cable were equipped with fibre interfaces to transmit the Profibus signals. On the two TBMs and in the control room at the mouth of the tunnel, the same interfaces act as a link to the local PLCs.

Piacentini says: "These fibre interfaces, which constantly monitor the signal quality, are characterised by a robust hardware design, so they always permit secure data communication despite strong vibrations, impacts and high temperatures."

Redundant, fail-safe networks can also be implemented using the fibre interfaces. However, for the Katzenberg tunnel this was deliberately avoided. Alfred Huber, project manager at Belden, explains: "Because the TBMs can operate self-sufficiently for a time using the information stored in the local control computers, a brief interruption of data connectivity to the tunnel mouth could be tolerated. This greatly simplified the cabling and made it much easier to handle."

Data protocols

The approach adopted by Wayss & Freytag Ingenieurbau for secure Profibus data transfer via fibre optic cables has proven itself in the construction of the Katzenberg tunnel in the same way as have Belden's active components. Nevertheless, there are already signs of other data protocols being used.

Product Manager Rolf-Dieter Sommer, who is responsible for Hirschmann fibre interfaces at Belden, explains: "Telephone connections between the TBMs and the control centre at the tunnel mouth are already implemented using Voice over IP. We are currently working on simultaneously and reliably transferring control signals over an Ethernet cable."

Hirschmann, a Belden Brand, manufactures Ethernet switches, wireless access points, firewall/VPN routers and network management software for harsh industrial environments. The Hirschmann brand stands for experience and expertise in the automation, power transmission and distribution, transportation and energy industries, having pioneered the development of Ethernet as a common standard for industrial control systems. Hirschmann products ensure hassle-free and secure data communication under the harshest conditions due to their ruggedised design and construction.

For more information about Hirschmann optical communications technology, please visit www.hirschmann.com or email [email protected] for product inquiries.