http://www.engineeringnews.co.za/article/new-machinery-expected-to-improve-quality-of-butt-welds-for-plastic-pipe-industry-2012-06-15

New machinery to improve quality of butt welds

Published 15 Jun 12
The Installation and Fabrication Plastic Pipe Association (Ifpa) and its parent body, the Southern African Plastic Pipe Manufacturers Association (Sappma), have made a bend testing machine available to Plastics SA for training and testing purposes.

The machine will be housed at the Plastics SA (previously the Plastics Federation of South Africa) head office in Midrand, Gauteng.

Bend testing, which was developed in Germany, is a quick and effective way of determining the quality of the fusion of butt welds.

Sappma CEO Jan Venter says the bend testing machine is used for the quality assurance of butt welds done by contractors, as well as those done during training sessions hosted by Plastics SA.

“We have identified a significant need for experienced butt welders in the plastics industry and it has become difficult to find staff with the right qualifications, training and experience to provide butt welding of a high standard.

“The trend towards using high-density polyethylene (HDPE) in the pipes industry has also increased the need for specialists in the field of butt welding, as most HDPE pipe joints are done by way of butt welds,” he says.

He adds that a well-engineered pipe system is dependent on good design and high pipe quality, as well as minimum standards at the downstream end, which includes looking at the quality of fabricated fittings and pipeline installations.

“Sappma realised the benefit it would unlock for the plastic pipe industry if it were to make available a bend tester that could practically test and judge the quality of butt welding on HDPE and polyvinyl chloride pipes,” says Venter.

He adds that the availability of the machine to do testing and training for this specialised field is a huge step forward for the plastic pipes industry and its reputation.

“Not only does Plastics SA offer its students practical, hands-on training on the bend tester, it also makes an operator available should any of Sappma’s members wish to perform their own tests,” he says.

The concept of a bend tester for welds is simple: a narrow strip is cut from the welded joint longitudinally with the pipe. The strip of material is prepared to a determined shape and finish. The finished sample is then inserted into the machine and bent at a specific rate into a U-shape.

No cracks should appear at the weld area during the process. The purpose is to ensure the plastic material of the two pipes is properly fused and that the weld and the heat-affected zone have appropriate mechanical properties.

Usually, bend tests are designed so that the outer surface of the specimen is stretched to a ductility level that approximates the minimum per cent elongation required in a tensile test.

When defects exist in materials that are strained to these limits, the materials tear locally. When tearing exceeds a specific limit, the specimen fails.

“The plastic piping business is a strategic industry and hardware needs to be reliable for extended periods. Long-term product and installation quality is, there- fore, fundamental.

“By making this investment in the future of the plastic pipes industry, we are confident that we will see a marked improve- ment in the quality of butt welds and, therefore, in pipe installations, in general, in the months to come,” says Venter.

He notes that the bend tester machine and the Plastics SA training facility will also benefit the welding industry.

“This facility will play an important role in ensuring that more skilled and quali- fied welders are available to the welding industry. This is important, as the trained staff will be able to produce quality work, ensuring that the pipes are used correctly, which also enhances the quality of the pipes,” states Venter.

This is in accordance with Sappma’s and Ifpa’s plans to uplift the welding industry.

“The welding industry is in a reason- able state, but Ifpa and Sappma are endeavouring to uplift the industry even further. Our projects are dedicated to this cause. We also offer the welding industry peace of mind when dealing with our members and their products,” he says.

He emphasises the importance of plastic pipes in the implementation of infrastructure in South Africa.

“We are committed to the upliftment of both the plastic pipes and the welding industries and their standards. We aim to bring the welded joints of HDPE pipes to a high standard, as this is an important element in the infrastructure of the country.”