By: Ilan Solomons Taken from: Engineering News
The existing steel and asbestos cement pipe infrastructure in South Africa has undoubtedly corroded since their installation fifty years ago, warns the Southern African Plastic Pipe Manufactures Association (Sappma).
“The majority of the old water pipes were installed in the early 1960s or earlier and have undoubtedly reached the end of their effective life span. Unless urgent attention is given to the replacement and maintenance of the water infrastructure, the end result is predictable – daily bursts will occur, followed by catastrophic component failure and regular and prolonged disruptions in service delivery,” says Sappma chairperson Jan Venter.
Water distribution, waste disposal, irrigation and telecommunications all rely on pipelines to function, he points out, and, therefore, these pipelines lie at the heart of South Africa’s infrastructure and should be replaced before they fail.
According to the 2011 census results, South Africa’s population has increased from about 40.5-million people in 1996 to about 51.8-million people in 2011.
He explains that the country’s infrastructure is under pressure and threatens to collapse if municipalities do not follow the example of the eThekwini municipality, in Durban, which completed a $205-million asbestos cement (AC) pipe replacement project in June 2010. The eThekwini municipality replaced 1 750 km of ageing AC water pipe with modified polyvinyl chloride (PVC) and high-density polyethylene (HDPE) pipe.
According to Sappma, the quality and quantity of water are under severe pressure in South Africa, aggravated by rapidly increasing demand, severe pollution and huge distribution losses.
“The two main causes of water loss are corrosion and the poor joining of pipes. For this reason, old steel or asbestos pipes are being replaced with plastic pipes around the country because they do not corrode and the joints are leakproof if installed correctly,” he says.
“Although the plastic-pipe industry is rela- tively small, it is of great importance in the devel- opment and maintenance of the country’s water infrastructure,” Venter highlights.
He adds that it is also, however, one of the most demanding industries, as the products engineered by the plastic-pipes industry to transport water are required to last 100 years.
HDPE and PVC pipes are lightweight, easy to handle and easy to join. They are available in a range of sizes and pressure ratings and have low frictional resistance, with hydraulic properties that remain virtually unchanged over their life cycle, which results in low pumping costs.
The Water Research Commission completed a survey of 132 municipalities in South Africa earlier this year, which indicates that nonrevenue – water lost through leaks, incorrect metering and unauthorised consumption – averages about 37% a year.
“This amounts to a financial loss of about R7.2-billion a year. Australia, another water-scarce country, loses less than 10%. Therefore, it is possible for South Africa to curb its loss of treated water, which it simply cannot afford to continue losing so much of,” emphasises Venter.
He says, ordinarily, not many people spare a thought for the thousands of kilometres of plastic pipes that supply rural communities across Africa with clean drinking water.
Sappma member companies have been exten- sively involved in supplying water to isolated communities throughout Africa, including in South Africa, in the past five years.
“Sappma and its members regard the water market as one of our most important focus points. We are urging local governments to ensure that attention is paid to the warning signs of degrading water infrastructure by implementing a pipe-replacement project and investing in the development of the necessary technical skills required for such a project,” he asserts, adding that these skills are greatly lacking in South Africa.
Environmental Impact of Plastic Pipes
In April, Sappma released the findings of a study that aimed to investigate the environmental footprint of the manufacturing and use of plastic pipes. “To quantify and correctly assess the amount of energy used to manufacture a material or product, an embodied energy analysis is performed. This involves assessing the overall amount of energy that is needed to extract the raw material, manufacture the products and maintain them once they have been installed,” explains Venter.
Even though the material energy of ductile iron is much than that of plastics in terms of mass (MJ/kg), this is reversed when wall thickness and mass per metre are taken into consideration.
Similarly, the amount of carbon dioxide (CO2) that is emitted during the production of plastic piping is far below that of ductile iron. Thanks to its low mass, the study has shown that the cost of transporting plastic pipe is considerably less than that of equivalent steel or concrete pipes.
“It is important to consider the amount of electricity used in the pumping of fluids through pipelines,” Venter says, adding that an estimated 60% of the world’s electricity is used by electric motors, of which 20% is used for pumping.
“Because of the specific properties of plastic pipe, the walls offer limited resistance to flow and, even more importantly, the piping remains virtually unchanged throughout its operating life.”
Comparative calculations show that the increase in power or pumping cost after 50 years is only 13.6% for thermoplastic piping, compared with the 62.6% for steel piping.
Recovery and Recycling
Plastic pipes can easily be recycled and are being recycled on a relatively large scale because of the high value of the polymer used in the manufacturing process. A 2009 survey by the Plastics SA (then called Plastics Federation of South Africa) has shown that about 14 000 t of HDPE and PVC pipe was recycled at external facilities in South Africa. In-house recycling by pipe manufacturers in South Africa was estimated to be about 8 000 t, bringing the total for these two sources of recycled HDPE and PVC pipe to about 22 000 t/y.
“Plastic pipe is not wasted and, therefore, does not contribute to environmental pollution. One-hundred per cent of recycled pipe can be reused, although strict quality requirements set by Sappma allow most recycled pipe to be used only in noncritical applications,” says Venter.
He adds that, although ductile iron and steel pipes can also be recycled, the energy cost involved makes the process considerably more costly.
Venter says calculations show that the power consumption to recycle plastic pipe is about R0.09/kg, compared with R0.23/kg to R0.45/kg for steel, taking into consideration that many steel pipelines are internally lined with material that first needs to be stripped.
The results of local tests conducted by Plastics SA support the findings of the European Denkstatt Study, which analyses the environmental impact of 173 products throughout their entire life cycle. The study, Plastics’ Contribution to Climate Protection, was funded by the European plastics industry.
The study identifies plastics’ share in citizens’ carbon footprints and provides a carbon life- cycle analysis of plastics, compared with their alternatives in packaging, transportation, building and construction, and ecoproduct enablement.
Initial results indicate that while the carbon footprint of an average European consumer amount to about 14 t of CO2 for each capital city a year, only 1.3% (170 kg) comprises the use of plastic products. This data indicates that plas- tic saves 2 300-million GJ in energy every year.
“This equates to 50-million tons of crude oil – the size of 194 large oil tankers. Plastic products prevent 120-million tons of greenhouse-gas emissions a year,” Venter concludes.
Edited by: Tracy Hancock