All 460 people who have worked on the major $134 million upgrade of the three-decade-old sinter plant to date could have been excused for holding their breath after such a tightly scheduled dismantling and construction project.

But at 11pm last Monday the main strand came back online seamlessly.

A constant stream of sinter was being produced by 4am on Tuesday and, to the credit of manager Jim Fresh and his workforce, the refurbished plant made very little noise.

Not only had he and his team been able to increase the capacity of the giant sinter-making plant, they had also made it more environmentally efficient.

"The process is pretty efficient really because you recycle everything," Mr Fresh said, and that includes material from the blast furnaces.

Mr Fresh said everyone involved should be proud of the work which was severely hampered by a long period of wet weather during the month-long shutdown.

And although he is preparing to return home to Pittsburgh after four years in Wollongong, other capital investment work at the sinter plant and nearby conveyor sequence continues.

A new junction tower is being rebuilt for the conveyor sequence which will help the sinter plant reach its target capacity of 6.6 million tonnes.

It is expected to be completed by late September.

Work is also progressing on the installation of a fourth fan for the rotary cooling system.

Mr Fresh said one of the three waste gas precipitators, which cleans dust from the off-gas produced by the combustion process used to cook metallurgical material, was still under construction.

"But it is making good quality sinter," he said. "The start-up curve was very steep. We are already feeding sinter to No 6 blast furnace. The final handover from construction was pretty smooth.

"The evidence we have to date is the quality of the work has been very high. The operators and maintenance people are pleased. We have increased that plants capacity but we have also improved the efficiency of the environmental dust collection units."