A tower of strength: Broadcast Australia’s structural inspection program

22 Jun 2011

In order to maintain the robustness of its transmission network, Broadcast Australia conducts a program of regular health-checks of all its structures countrywide.

Broadcast Australia has approximately 580 sites across the country, most of which have at least one mast or tower that are used to support an array of antennas and transmission equipment. With some of these structures up to 200m in height—such as the AM antenna at the Bald Hills facility—it is necessary for the company to conduct regular inspections to ensure they are strong, sound and fit for purpose.

To this end, the company runs a structural health-check program. This is managed by a number of office-based project managers and carried out by two inspection field teams. Broadcast Australia Structures Manager, Wesley Spark, explained that this work is a continuous operation. "We check all structures at least once within a three year window," he said. "However, we might conduct checks as frequently as annually at some key locations—if this is warranted by site conditions."

In-depth inspections

The checks require full access to all areas of the structure—including footings, climbing ladders, platforms, cable runs, earthing, supports, and even aircraft warning lights if these are present. "A full tower assessment involves climbing over the entire structure in order to properly examine all areas," said Wesley. "Only by doing this are we able to complete an inspection to the necessary standard."

This methodology can prove challenging in some instances. "Our site at Mt Bellenden Ker—Queensland's second highest mountain—is only accessible via cable car," said Wesley. "With a 100m mast on top of the 1,593m-high peak, this is certainly one job you don't want to be doing on a windy day!"

Fine-tuning the frequency

The types of problem identified by the structural health-check program vary enormously with the environment in which the structure is situated. For example, a tower located close to the coast will be more prone to salt-corrosion than one located inland. "Rust and loose feeder cables are the most common problems we tend to find," said Wesley. "We are usually able to fix these minor issues during the scheduled inspection, without the need for an additional repair visit."

The findings of each site visit are used to fine-tune the ongoing inspection program. The aim is to visit each structure at the right frequency, so that deficiencies can be addressed before they become an impediment to broadcast services. "Prevention is always preferably to re-active repairs," said Wesley. "This health-check program enables irreversible damage to be avoided, and allows the uptime of service to customers to be maximised."

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