Local specialist Group Five Mining and Industrial completed a contract for the civil works and pipe racks for Sasol’s 15th air-separation unit (ASU) in April, having started on site in October 2002. By December 2002 the company had completed the bulk excavations for the entire plant and, by early 2003, foundations for the coldbox area and the construction of clean stormwater drains for all areas was complete.

The ASU will be the largest in the world and will implement new technology, which aims at reducing costs and improving production. Group Five was contracted to Air Liquide, a company that has gained inter-national experience in the installation and use of the new technology.

Group Five Mining and Industrial MD Peter Keenan says a number of challenges faced his team, not the least of which was the extent of the plant to be constructed. “This was especially true of the section that houses the ASU’s main compressor and booster air compressor, which is the lar- gest compressor of its kind to be installed for such an application.

“The foundation for the compressor is of particular importance and the degree of accuracy in laying it was notably higher than the other foundations because of the size of the compressor,” Keenan says.

He adds that the monolithic pour of 750 m3 of concrete into the compressor area was completed in February, followed by the completion of the main pipe rack and filter structures, the water wash-tower area, the air-purification area and chiller tower foundation in March. Another challenge facing the Group Five team was that void formers had to be installed between the ground and the foundations to allow for movement of the ground. “The void formers were difficult to work with due to the thickness of the foundations. They are designed to degrade over time, creating a gap between the expansive ground and the foundations,” explains Keenan.

He adds that having maintained a steady four-star Nosa safety rating over a period of years on various Sasol contracts, Group Five is familiar with the stringent safety requirements, which it maintained through the ASU contract.