Big blow job – A 2500-litre tank leaves the mould at the Africa Tanks plant in Cullinan, to the east of Pretoria. The new company is able to produce tanks at far greater speed than by the roto process, with the cycle time for this size being just over 7min, only about 15% of the time required for roto moulding; the design of the container and quality of the surface finish result in an attractive container
IN ONE of the boldest steps in the local converting industry for quite some time, Africa Tanks has commenced with the blow moulding of plastic tanks up to 5000 litres at Cullinan near Pretoria.
With an estimated capex of R26-million, this is a major venture into a market which has not been tested in South Africa before. The production of large plastic tanks in Southern Africa, mainly for water storage, has up to now been the territory of rotational moulding, and many in the roto industry were fearing the arrival of blow moulding technology. But conditions in the region have changed over the past decade – specifically due to the perceived unpredictability of water supply, drought in several areas as well as the increased need for drinking water – and it appears that the roto sector, which includes several very efficient tank manufacturing operations, were unable to supply orders from some of the building/construction supply chains.
That was in fact the origin of the Africa Tanks project: Hannes Geldenhuys, co-founder of the new company, had been involved at Build-it hardware group since 1997 and, while managing orders for the chain, noticed that it could not procure a sufficient supply of water tanks from the local roto manufacturers. Build-it operates over 350 outlets around the region (in SA as well as in Lesotho, Namibia, Mozambique and Swaziland), so demand was substantial.
Geldenhuys, along with business partner and Africa Tanks co-founder Frik Mulder, assessed the situation and considered the possibility of blow moulding. Others in the sector had previously looked at the potential to blow mould tanks and the topic had been discussed at several roto trade conferences, but no-one had as yet been prepared to take the leap. The partners researched the options and then, with virtually complete secrecy, embarked on an extensive tour to China, visiting manufacturers of large blow moulding machines. The technology to blow mould large tanks is readily available in China and it likewise became clear that blow moulding tanks up to 5000-litres has become relatively common in developed countries.
They chose a system from Yankang Plastic Machinery of Qingdao, equipped to manufacture three-layer containers up to 5000 litres, enabling it to make the first 3-layer tank in South Africa. Geldenhuys and Mulder (who now resides in Perth, Australia) were impressed by the Yankang technology and also ordered the moulds from the company. Africa Tanks now has moulds for 5000, 4000 and 2500-litre tanks as well as for a 1500-litre ‘slimline’ tank for domestic installation. With some of the more popular sizes, it also has duplicate moulds. It also manufactures a ‘nestable’ tank.
HDPE is used in the blow moulding operation, as opposed to linear for roto, with another advantage for the blown option being that colour masterbatch, or other additives, can be dosed and blended at the machine, compared to roto where material needs to be milled to powder and colour and other additives/stabilizers need to be blended in a prior compounding step.
Although blow moulding technology is all new to Geldenhuys, the company’s focus is simply on supplying its customer, namely Build-it group. Technicians from Yankang assisted during the commissioning of the machine, and the Africa Tanks production team have been on a steep learning curve since. The tanks’ three-layer HD structure comprises a coloured outer layer (for the colour of choice); a mid-layer of black, to reduce light ingress; and an inner-layer of white, to allow for easier inspection of the tanks.
“The inner layer white layer of food grade material is beneficial to users in more than one way: it is suitable for use for human consumption of potable water, and allows for better visibility inside the tank, to spot any foreign objects,” said Mulder.
“It is also the first large HDPE tank with greater density than linear LLDPE, and is less porous and hence inhibits growth of any bacteria,” he added.
The system can produce a 2500-litre tank in a little over seven minutes, approximately 15% of the cycle time of a similar sized roto moulded tank. Production of the 5000-litre tanks takes about 10 minutes, once again considerably quicker than by roto moulding. A further plus is that the tanks, on exiting the mould, are already cooled to room temperature – which allows for easier handling and is a further almost unexpected advantage.
But the far faster production has presented another challenge: that of transporting the tanks to market. At optimum output, running 2500-litre tanks, the Yankang would produce about 160 tanks a day; for the 5000-litre option, it would produce 144 tanks over 24 hours, which would present a significant logistics challenge.
As a result, the machine is not yet running at full output, and the affable Geldenhuys is if anything trying to rein the wild horse in.