A $US9.2 billion ($A9.96 billion) expansion of Fortescue Metals' iron ore operations in the Pilbara is complete.

The company’s Kings Valley project at the Solomon Hub, to be officially opened on Friday, will lift Fortescue’s production capacity to 155 million tonnes per year.

Since major expansion plans were announced in 2010, Fortescue has constructed the Solomon Hub, one of the largest iron ore developments in the world, expanded its Christmas Creek mine, and extended its port and rail facilities