Written by Kerryn Caulfield, Executive Director, Composites Australia Inc.
The factory was purpose built in 2010 following the Victorian Bushfires Royal Commission (2010) recommendation for the creation and implementation of technologies in electricity transmission and distribution that reduce bushfire risk. The concept was to blend chemistry, engineering and materials with legacy technology from the US to solve the environmental hazard of timber utility poles. The poles are light, fire proof, non-conductive, and well suited for installation in rough and environmentally sensitive terrain, including by helicopter. Now there are more than 25,000 Dulhunty Titan poles installed in the electricity distributions systems of Australia, French Polynesia and New Zealand.
Dulhunty produce utility poles, branded as Titan Poles for marine environments, sub stations, tennis courts, rural and suburban street power, and lighting and rural fencing, all with unique engineered properties. For example ‘Communication Poles,’ are hollow, steel free and non-conductive. They are both fire proof and engineered to ensure a high stiffness to reduce the risk of antenna movement in high wind conditions.
Equally, marine poles – which are also lightweight, steel free, and resistant to corrosion – can be mechanically driven into prepared holes with smaller barges and lifting gear than other pile types. Made without the harmful chemicals used to conserve timber poles, Titan poles safeguard the environments within which they are installed. The poles are hollow so cables and wires can be internally run through the pole, improving electrical safety and security.
While the Dulhunty factory was commissioned under the encouragement of the Victorian government, initial commercial interest came from Electricite de Tahiti (EDT), which operates Tahiti’s public energy service for the main island, as well as the surrounding islands in French Polynesia. EDT recognised the properties of Dulhunty’s technology as a solution to the issues brought about by its unique environment.
Islands have double the number of invasive species of termites that continents do, with islands in the South Pacific the most invaded geographical region. As well as the termites that eat both hard and soft wood, Tahiti’s acidic soil causes in-ground decay of timber poles. Transport and access is also problematic, as apart from a fertile coastal plain, the terrain of Tahiti is jagged and mountainous having been formed by volcanic activity from its two ancient volcanoes – Tahiti Nui and Tahiti Iti.
Phil Scott, General Manager of Dulhunty since 2011 says, “We’ve now manufactured and installed thousands of poles ranging in length from 9 metres to 18 metres and strengths from 3kN to 24kN, covering almost the entire Island of Tahiti, many of which have valiantly survived tropical storms and cyclones.”
On the home front, product and material acceptance of the Titan technology took much longer than expected. Phil explains, “For good reason, asset managers are risk-averse and hesitant to specify alternative products. But this has led to some unconventional proof-of-concept testing including whether structural integrity would be affected by a whipper snipper or the corrosive effects of long term exposure to dog urine. We even had to test whether possums or koalas could grip the poles. It’s taken over 300 tests over many years for the product to be accepted but now we are developing plans to increase our manufacturing footprint to keep up with the demand.”
As with all new composites technologies, price also played a part in the push back from asset managers. “We’re at least a third more expensive than timber poles. And it’s taken just as long for acceptance that the extra cost of each pole is more than compensated by reduced installation, monitoring and whole-of-life costs,” lamented Phil.
Dulhunty technology is based on a polymer modified cement using a Metakaolin which is a dehydroxylated form of the clay mineral kaolinite, sometimes known as China clay or kaolin and used in porcelain manufacture. It is used for high performance, high strength and lightweight structural concretes. Dehydroxylisation is a kiln process carried out between 500°C and 800°C in which kaolin is transformed to metakaolin. This material has strong pozzolanic (cementing) properties when added to cement, the particle size being much smaller than cement particles. Where metakaolin is used as a filler in high strength concrete applications it is considered to have twice the reactivity of most other pozzolans. Mixed with Portland cement, it produces a concrete mix with superior engineering properties which include increased durability, compressive and flexural strength and resistance to acid and chemical attack as well as reduced permeability, efflorescence and shrinkage.
Each pole is manufactured by feeding the concrete slurry and rovings onto a vertical rotationally oscillating mandrel. The slurry mix is added uniformly from a bath as the glass fibre filaments are applied in accordance with a preset design program, until the desired wall thickness and reinforcement lay for the specified pole performance is reached. The fibreglass adds strength and flexibility which is engineered into the winding pattern, and acts as a conveyor system for the cement. Upon completion the pole is wrapped in a protective plastic coating for 24 hours, until the rapid first cure is complete, following which the mandrel and the protective coating are removed.
“Technically, concrete never stops curing. These minerals cure the concrete continuously which makes its chemical structure grow denser and stronger over time. This creates a much stronger, more durable concrete that actually gets better with age. The continuous fibreglass rovings provide tensile strength and corrects the poles when deflected and allow production of required combination of properties,” advised Phil.
The Dulhunty Titan utility poles are unique in that they can be designed to meet specific customer needs for durability and strength while complying with ‘AS/NZS 4676 Structural design requirements. Utility poles are characteristically specified to carry 5kN, 8kN, 16kN and up to 24kN. Unlike timber poles, strength, deflection and the location of the deflection can be engineered through capitalising on winding patterns and material properties for wind conditions, pole spacing and component loads – be they crossarms, satellites and safety features.
Uniquely, a whole of life RFID (Radio Frequency IDentification) is implanted into the pole during production. The RFID is itself insulated by the materials and protected from weather and fire ensuring ongoing identification is maintained for the pole life. It captures pole-specific information and event related data including exposure to weather or vehicle strike related events. A pole’s complete life cycles, as well as those of the assets located on and in the pole are recorded for asset management purposes. Geospatial technology can locate individual poles within a network and evidence of inspection can be demonstrated by reading the RFID and downloading to computer.
Dulhunty Titan poles are available in the desired kN rating in lengths of 7.2 metres to 12.5 metres as a single piece and 14 metres-18 metres are supplied preassembled as a two piece pole.