Precast concrete products company Rocla earlier this year supplied precast concrete inverted culverts, lids and bases to use as cooling channels to the R2.24-billion, 100 MW natural-gas-fired Gigawatt power station, near Ressano Garcia, in Mozambique.
Rocla received the order, valued at about R800 000, from construction company WBHO Construction in March. Subsequent deliveries took place over a few weeks as the precast products became available.
Rocla supplied 70 culverts measuring 2 100 cm × 1 800 cm, 50 culverts measuring 900 cm × 900 cm and 50 bases measuring 900 cm × 1 220 cm, as well as lids for all the culverts.
Civils construction on the power station started in 2014 and the station is expected to be fully operational by the end of 2015.
The redesign to manufacture the reinforced culverts and lids led to a longer lead time, as Rocla’s technical engineers had to ensure that quality and technical specifications were met prior to sending the products to the client.
Rocla sales consultant David Cooper tells Engineering News that the company had to redesign the culverts to make them suitable for inverted use and with extra load-carrying capabilities. This also involved redesigning the culvert lids to suit the modified culverts, which had additional reinforcing.
Further, owing to the culverts being used upside down, 123 shear links were inserted into each of the culverts, as well as additional links that are not common in standard culverts. This ensured that the required strength was obtained so that the culverts could be used in the cooling channels at the power station. “Despite these design challenges, we supplied the first batch of culverts just three weeks from [the time] the customer sent the design specifications,” says Cooper.
He adds that the culverts supplied to the Mozambique project were actually overspecified for channelling cooling-tower water, resulting in their being hassle- and maintenance-free, with a typical life span of more than 50 years.
Cooper tells Engineering News this is the first time Rocla has supplied culverts for application in cooling channels at a power station, though the project is testament to the versatility of Rocla’s precast products and engineering capabilities, as well as the various applications in which the culverts can be used.
He says that, “as a direct result of this order”, Rocla has received an enquiry from another large contractor involved in the project for culverts to be used in another project, but on a smaller scale.
“It was a major benefit to have the manufacturing facility in Nelspruit, from where the products were easily transported by road to Mozambique,” says Cooper.
Rocla manufactures and supplies precast concrete products such as culverts, piping, poles, manholes, retaining walls, sewer pipes and other infrastructure-related technologies. Rocla is part of the Infrastructure Specialist Group (ISG), which also includes Technicrete ISG and Ocon Brick.