The new 90MW Kawerau Geothermal Steam Power Station has many Kiwi-made design features, but it’s the huge, shiny, separator towers that dominate the orderly nest of pipes and structures in the ‘yard’ of the power plant.
They include the second largest steam separator in the world – designed and built here in New Zealand by Robt Stone, a company that started in New Plymouth and is now a business of Tenix Alliance. The company was commissioned by Kawerau’s builders, Sumitomo Corporation to design, fabricate and deliver three steam separators and four steam strainers to the project. The $2 million dollar contract involved an estimated 15,000 man hours and 180 tonnes of steel. Parts were sourced from Asia and Australia with fabrication in New Plymouth.
One separator is where low pressure steam is flashed off at around 2 bar from the brine in the separators and the steam used to drive the low pressure end of the turbine. The largest separator, weighing 75 tonnes and standing 21 metres high, is where the high pressure steam is separated from the brine. In places, this separator is 38mm thick, capable of withstanding pressure of around 26 bar.
It took three days to transport the separator from New Plymouth to Kawerau, a slow journey on Multi-Trans heavy haulage equipment that had to negotiate the Cobham Bridge on State Highway 3 over the Whanganui River. The vehicles weighed five tonnes more than the legal capacity of the bridge – a problem overcome by increasing the number of axles and spreading the load.
Contractor Vol.33 No.3 April 2009
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