The poles and masts division of Infraset has supplied over 250 prestressed concrete masts to Edison Jehamo Power to increase electrical power distribution to several mines in the Rustenburg area. Delivered in 11m, 13m and 14.2m lengths, the masts are used to carry aluminium/steel reinforced conductor cabling with a system voltage rating of 33kVA.Malcolm Hair, project manager at Edison Jehamo Power, says the masts were installed in two tranches, the first in 2005 and the second in 2009. Foundation pits, two metres square, were excavated to a depth of two metres and once the masts were planted and vertically aligned, they were positioned permanently with waste-rock backfill sourced from the mines. In some instances, additional support is provided by stay rods.Product manager at Infraset’s poles and mast division, Njabulo Khumalo, comments that all the masts were manufactured with earthing bars (so no additional earth conductor is required) to protect them against lightning. He notes further that the high strength-to-weight ratio of the prestressed concrete masts is superior to most other mast materials.
"The resilience of prestressed concrete enables our masts to handle exceptionally high levels of overloading. Moreover, experience worldwide has demonstrated that during their lifetime, prestressed concrete masts are maintenance free – a major advantage. Unlike other materials, concrete suffers no loss of strength over the years and it is resistant to insects, fire, rot and corrosion.
“The masts supplied to the Rustenburg projects have a rectangular tapered I-Section design and are cast in high-strength, high-density concrete with a smooth finish. They are functional yet relatively light, and this made them convenient for Edison Jehamo Power to handle. They are also extremely difficult to vandalise and, unlike steel or timber, offer little or no incentive to vandals," says Khumalo.
Infraset’s manufacturing facilities are ISO 9002 accredited and the masts are produced in a wide range of strengths and sizes to suit most requirements in medium voltage (MV) and low voltage (LV) lines. They comply with Eskom DTC 0106 and the relevant SABS and Transnet Freight Rail specifications.