The big dig

A worker inspects the teeth of a 3,000-tonne open-pit rotary excavator 1571 in Weisswasser, Germany.

The giant bucket wheel excavator (BWE) is making an 18km journey to the next dig site at the neighbouring open cast mine of Nochten Reichwalde.

It will take until Aug 26 to reach its destination as it crawls along at a rate of about 6m a minute.

A BWE consists of a superstructure to which several more components are fixed. The bucket wheel from which the machines get their name is a large, round wheel with a configuration of scoops which is fixed to a boom and is capable of rotating.

Material picked up by the cutting wheel is transferred back along the boom. The primary application of BWEs is in lignite (brown coal) mining, where they are used for soft rock overburden removal in the absence of blasting.

They are useful in this capacity for their ability to continuously deliver large volumes of materials to processors, which is especially important, given the high demand for lignite.

A version of this article appeared in the print edition of The Straits Times on August 17, 2015, with the headline 'The big dig'. Print Edition | Subscribe