An igus energy chain system has recently been designed into the largest capacity rail traverse in the UK. Built by heavy rail lifting manufacturer Mechan Ltd, the traverser moves freight locomotives between eight lines at the Port of Felixstowe's new North Rail Terminal. With its pivotal role within the Port's rail network, the traverser's reliability is paramount, while its environment presents a number of challenges.
The traverser has a capacity of 170 tonnes, weighs 90 tonnes and measures 30m in length. It runs on eight wheels, six of which are powered each with a 15kW electric motor; the entire motor set being fed by a 200A 415V 3-phase power supply. The traverser also has an on-board PLC (programmable logic controller) based system that monitors the status of the traverser's sensors and activates lights and signals accordingly. It can also activate wheelstops, which prevent a locomotive overrunning the traverser's rail track.
Power to the motors is not controlled directly by the controller. Instead, the PLC transmits data via a Profibus field bus to a ground-based control and switching unit, which acts on the Profibus data to switch power to the electric motors. Therefore, the motors' power cables, the Profibus data cable and an Emergency Stop cable must be routed between the moving traverser and fixed ground station. This requires a cabling installation that can reliably withstand repeated flexing during continuous 24/7 operation in a challenging outdoor environment.
During the initial design phase, a cable reeling drum was considered. Martin Berry, Mechan's Engineering Director, explains: "Felixstowe wanted an extremely reliable product; a reeling drum would have involved sliding contacts and this is not good for communication signals." After deciding that energy chains offered the secure and reliable comms network needed, Mechan turned to cable carrier specialist igus. Mechan took advantage of the project-oriented design, build and installation capability of igus to obtain a complete, installed energy chain system - and igus certainly had to call on their specialist experience and expertise to overcome the challenges presented. At 30m, the energy chain's size was no problem, as igus has previously installed chains of up to 615m. Instead, the issues related to the environment, and to some practical aspects of the installation.
The environment was a concern because of several environmental factors. As Felixstowe is a marine port, its rainfall has a high salt content and is corrosive, while protection from wind-borne debris was also necessary; freedom of movement could be impeded by a build-up of debris. Also, in winter, freezing temperatures and ice are encountered and the robust design of the system allows this to be overcome.
The installation challenge was that the concrete bed for the traverser rails had protruding plinths at 8m intervals, preventing any cable trough being laid directly along the length of the main bed - yet a suitable trough would need 2m fixing centres to allow a fast and robust installation. Installing an I-beam to provide mounting points was also not an option as this would have interfered with the traverser travel path.
igus' project team's response comprised a customised FLIZZ covered trough system. The FLIZZ is manufactured from stainless steel to provide corrosion resistance, and contains an E4 gliding e-chain. This energy chain carries a set of chainflex power and data cables with special properties to survive many flex cycles, high speeds and accelerations while offering EMC safety and compliance with relevant standards.
The complete system, including the FLIZZ, E4.1 e-chain and chainflex cables, was installed by igus into the traverser. Steelwork comprising unistruts and braces was designed, manufactured and used by igus to mount the system to the concrete while clearing the plinths.
Mr Berry concludes: "This project's success has been due to both igus' project capabilities and its products. These challenges were highly project specific, yet overcome very effectively. An acceptance test was passed in which 100 moves were made without issue. The energy chain is proving to be a more robust and compact solution than festoons or reeling drums, and the igus product has been perfectly matched to the traverser's environment."
To learn more about energy chain systems from igus please visit www.igus.co.uk.