Wineglass Tank a Towering Achievement

Location:	Sydney, NSW
Country:	Australia
Construction Date:	December 2005
Products Used:	AS/NZS 3678 - 250 XLERPLATE®

A 'wineglass' steel water tank in Sydney has taken the art of elevated water storage to a new level with a 3.2 megalitre tank, a capacity previously unseen in Sydney. Established tank manufacturer Saunders International has built the tank at Quakers Hill in Sydney's west to serve some 15,000 households in stage two of the vast Rouse Hill development.

The tank joins three smaller units of the same general configuration, each of 1.5 megalitres, which Saunders had built to serve the 20,000-lot first stage of the estate.

The new tank stands 42 metres high with a diameter of 21.4 metres, and incorporates more than 300 tonnes of steel. Project leader Robert Patterson said the major challenge with this tank was the tightly restricted site that prevented the use of large cranes. For this reason the large tank was fabricated at ground level around its central core and then jacked up, whereas the smaller tanks had been built separately on the ground and craned into position. Although the jacking concept is not new, Robert Patterson believes the scale of the exercise sets it apart from other such jobs.

Saunders designed the wineglass profile in response to the functional requirements of the project. Given a specification for maximum and minimum operating water levels and total capacity, the simple combination of a cylindrical main tank on a conical base met all the requirements. According to Robert Patterson, the in-house designers are very pleased with their achievement, which involved finite element analysis to optimise the design.

Fabrication, too, was a major achievement. The tank is fabricated from 290 tonnes of BlueScope Steel AS3678-250 XLERPLATE®*. Gauge varies according to function, with 28mm and 25mm plate in the vertical stem, and 32 mm at the base of the cone, decreasing to 16mm at the outer edge. The vertical sides of the bowl are 8mm thick. Reinforcements account for a further 22 tonnes of steel in a variety of sections.

The tank was constructed on contract to Abigroup Contractors Pty Ltd, which is responsible for the estate's overall reticulation including a pump station to service the new reservoir and trunk mains to the area. Construction was completed ahead of schedule in 13 weeks.

The biggest challenge was in the fine tolerances required to ensure the conical transition section fitted properly around the stem, where a collar was fabricated in place to connect with the conical profile of the tank.

Careful attention in both design and fabrication ensured a clearance of just 3 mm despite the large scale of the exercise, jacking a 120-tonne tank 25 metres up a stem measuring six metres in diameter. Completing the tank is a steel roof, with access available through the central core. Although the large tank is purely for potable water, the three earlier tanks were part of an innovative water management system that enabled both potable and recycled water to be used within the Rouse Hill Development.

* From 1 August 2002, BlueScope Steel Plate Products are known as XLERPLATE®