Case Study | Kenwood Nexedge Digital Radio System For Aluminium Smelter

At the foot of Ben Nevis in the Highlands is the last remaining aluminium smelter in the United Kingdom. The smelter is owned and operated by Rio Tinto Alcan, part of the Rio Tinto Group. Producing aluminium ingots is an industrial process which is both hazardous and power intensive. Due to the vast quantities of electricity being consumed the only way of being sustainable is to utilise hydro electricity.

Behind the smelter is a 70MW hydroelectric power plant which is fed by a scheme built in three phases between the early 1920’s and the mid 1940’s. It harnesses a number of major rivers including the Mashie, Pattack, Spean and Spey. From the Spey water flows into Laggan and then on into Treig, some 30 miles away from the plant. Finally, a 15 mile, 15 feet diameter tunnel runs from Loch Treig and emerges on the side of Ben Nevis into a 240ft deep surge chamber some 600 ft. above the smelter, which is connected via 5 large diameter steel pipes.

The safe operation and maintenance of the hydro scheme and aluminium smelter creates some unique challenges. With strict health and safety being the number one priority in and around the plant and as well as ensuring good on site radio communications the system requires flexibility and must be easily configurable and support a range of applications required by RTA.

RTA is also responsible for the maintenance of the civil engineering works which includes regular inspections of the conduit at regularly spaced intakes. Brabourne Communications Ltd [BL] were tasked with proposing a system that provided reliable on site communications and which would include telephone interconnect facilities to reduce the amount of mobile phone usage on site, lone worker, man down and other safety features were also required.

The wide area solution needed to include the use of range extending portable repeaters, automatic vehicle tracking, SCADA and CCTV applications. As the maintenance engineers are sometimes in very remote areas a reliable lone worker and man down system had to be incorporated. After an exhaustive analysis the Kenwood Nexedge system was shown to be the most appropriate solution as both an digital and analogue platform were needed, and Kenwood have available a range of applications which fitted the customers requirements at a low cost.

For the smelter a Nexedge digital trunk network provides voice communications and will allow RTA to reconfigure via the system manager as the network grows [a second site is to be installed at another hydro power scheme at Kinlochleven]. The wide area network operates as a conventional analogue system and makes use of 3 high sites between Fort William and Spey. This solution provides the bearer for the SCADA and CCTV images from the intakes. A microwave link completes the connection to the smelter from the Fort William high site. Common terminal equipment for both analogue/digital and conventional/trunked systems makes it simple to use and maintain. Seamless migration between different elements of the system makes training simpler and eliminates confusion for users. The system will also significantly reduce the costs of inspecting the pipeline intakes and enhance the safety of RTA employees.

Phase 2 of the project will see the installation of the outstation equipment at each intake. This will comprise converted shipping containers which will house the power plant and associated equipment. Once installed the water levels and flow rates at each intake can be monitored remotely whilst the CCTV will provide on demand images of the intake to assess the need for a maintenance visit. It is also planned to incorporate the BL Fire Alarm Warning System [FAWS] onto the trunk system thus providing a fully networked fire alarm system with the additional benefit of displaying fire panel messages direct to portable radios, allowing staff to instantly manage any incident that arises.

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