A number of 880 prestressed concrete poles, manufactured by INFRASET Infrastructure Products, have been installed...
Prestressed concrete masts have been specified by Transnet for a capacity upgrade at Saldanha / Sishen iron ore rail link. Manufactured and delivered by Concrete Manufacturers Association (CMA) member INFRASET Infrastructure Products, the masts will carry a supplementary feeder line, which will be used to boost the supply of electrical power to the overhead track line.
The last deliveries of the masts are scheduled for December. Once the masts are planted and the new electricity feeder cable is installed, Transnet’s Saldanha / Sishen line will be able to accommodate higher volumes of rail traffic, thereby providing for anticipated increases in the tonnage of iron ore exports.
CMA director, John Cairns, says that concrete masts are the most appropriate choice for this type of application, because unlike other materials such as steel, they are entirely maintenance-free.
“Concrete masts retain their structural integrity and aesthetic appeal without the need for routine and expensive maintenance such as de-rusting and painting. As a section of the line runs adjacent to the Atlantic shoreline between Strandfontein and Saldanha, where the sea spray quickly corrodes anything made of mild steel, the inert properties of concrete are especially apt in this application. In addition, the high strength-to-weight ratio of prestressed concrete masts gives them a distinct advantage over masts manufactured from other materials,” observes Cairns.
INFRASET won the tender last year, which not only entailed the manufacture but the also delivery of the masts to site at 120m intervals.
“Delivery has presented us with a considerable logistical challenge because the line stretches some 860km,” says Kobus Burger, general manager railway products of INFRASET.
“The contract involves the road delivery of over 7,000 12m and 13m masts, each of which weigh over 2t. Our trucks are making round trips of up 1,000km, all of them on sections of rough gravel surfaces. Furthermore, we are complying with extremely high quality and safety requirements,” says Burger.
The masts are being manufactured in De Aar, Northern Cape, where there are ample supplies of good quality aggregate and cement. ISO 9002 accredited, the De Aar factory is jointly owned by INFRASET and Empowa Investments through a BEE joint venture company known as Empowa Grinaker-LTA.
Rated at 64kN the masts are being manufactured to stringent quality standards and are cast in an attractive rectangular tapered I-section design in high-strength, high-density prestressed concrete with a smooth attractive finish.
“The resilience of prestressed concrete enables it to recover from the effects of a greater degree of overload than any other type of structural material. Furthermore, unlike other materials, concrete suffers no loss of strength over the years, being resistant to insects, fire, rot and corrosion. It is interesting to note that the first concrete masts used for overhead electrification on rail lines were installed in 1999 on Transnets’ Kimberley / De Aar line and those masts still look as good today as they did then,” concludes Burger.
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