Spoornet is developing techniques for reducing theft of copper cabling, in particular overhead line equipment on electrified routes. Conventional techniques, such as surveillance equipment and security patrols, were ruled out as prohibitively expensive to protect the 9000route-km electrified network.
Instead, OHLE engineers have investigated ways of reducing the scrap value of the copper wire. One technique tried was applying a thin layer of aluminium to the wire surface using a plasma-spraying process. Adding as little as 0·15% aluminium by volume has a drastic effect on the copper if stolen and melted for reuse, reducing the alloy’s conductivity by over a quarter. This makes it useless, and therefore worthless too, yet is cheap to apply (R4 per metre). The technique’s main drawback is low speed of application, which necessitates line closure while a works train applies the aluminium.
A second technique being evaluated uses small amounts of bismuth (0·05% by weight), which greatly increases brittleness when in alloy with copper, again making the stolen copper worthless. It is planned to punch a series of holes into the copper wire, and insert bismuth capsules into some of them. This would be within the conductor’s wear depth, so that at the end of its useable life it can be recycled - the bismuth contaminant having worn away.
Spoornet
Johannesburg, South Africa
Reader Enquiry Number 137
