Crane manufacturer Condra is fulfilling several orders for a range of unusually large overhead cranes for mines in South Africa and beyond – in Zambia and Namibia.

The company introduced additional shifts to complete the order for the cranes, which are being manufactured at its Johannesburg factory.

Three of the cranes feature box girders that are more than 30 m long.

“On the floor currently are two 50 t cranes with spans of 34 m, and a third, high-lift, 5 t crane with a 35 m span. Condra is simultaneously completing manufacture of a further four 50 t cranes with spans of around 20 m,” a Condra spokesperson said in a statement sent to Engineering News & Mining Weekly.

All six of the 50 t cranes are for a mine in Zambia, while the 5 t crane is destined for a mine in Namibia.

According to Condra, the 34 m and 35 m spans present unusual manufacturing challenges owing to girder dimensions.

Besides length, box girders for these spans stand two metres high and just under one metre wide.

“These are very big, very long, very heavy fabrications to manage. Manufacture involves intricate welding and very careful jigging to incorporate the correct camber to counter girders’ natural tendency to sag under load.”

Workflow Planning

The spokesperson further pointed out that girders of this length are delicate to manoeuvre on the shop floor, requiring resource and workflow planning. 

“End-carriage design has been important to ensure crane longevity, because the wheels must accommodate continuously changing stresses imposed by the girders as they flex under different loads,” he said.

Condra’s design team paid particular attention to both camber and end-carriage design to ensure durability, the spokesperson said in the statement.

In addition, Condra is manufacturing three single- girder overhead cranes, two portal cranes and a jib crane for Namibian mines.

“The company behind these orders is an engineering and project management consultancy with representation worldwide. “This company has additionally ordered 18 electric hoists of between 2 t and 25 t capacity and four chain blocks,” the Condra spokesperson added, noting that Condra and the consultancy have an association going back many years.

In South Africa’s Northern Cape province, Condra is currently commissioning two cranes at Gamsberg Phase Two, where the same consultancy contributed to metallurgy and process plant design.

“These, too, are big machines: one a 40/5 t crane with a 22 m span, [while] the other is an 80/20 t machine with an 18 m span.”

Gamsberg Phase Two is an expansion of the open-cast zinc mine to double yearly ore output from four-million to eight- million tonnes.

“Besides the cranes undergoing commissioning, Condra has completed delivery of two other cranes to Gamsberg Phase Two, for installation as the structural steelwork progresses.”

Condra expects to receive further orders from Southern and East Africa, notably Tanzania and Mozambique, where a marketing drive is currently under way.