A new molecularly-oriented PVC pipe (PVC-O) - used specifically for pressure applications - has opened up exciting new opportunities for plastic pipe manufacturers around the world and in South Africa.

“Designed to be lighter, have better impact resistance and increased tensile strength when compared to standard PVC, PVC-O pipes are for the first time technically competent and commercially viable to compete in the large diameter, high pressure, bulk water, trunk main pipe market that has historically been dominated by steel and ductile iron,” explains Jan Venter, Chief Executive Officer of SAPPMA (the Southern African Plastic Pipe Manufacturers Association).

The first PVC-O pipes entered the market about 40 years ago in the United Kingdom after the shapeless structure of PVC-U was reorganised into a layered structure.  This realignment of the PVC molecules is done through a process called biaxial orientation, and greatly enhances the material properties – making it about twice as strong and ten times more impact resistant compared to traditional PVC-U material.

“PVC-O pipe offers unbeatable mechanical properties in plastic pipes, such as high impact resistance (almost unbreakable), high stiffness and fatigue resistance, an excellent behaviour with external loads, crack propagation prevention and maximum flexibility.  It is also the most eco-friendly pipe system in the world as it requires less energy to produce than conventional PVC-U and other pipe materials, as well as less energy in service than all other pipe types,” Venter says.

Thanks to the fact that the wall thickness of PVC-O pipes can be reduced by up to 50% while maintaining the same pressure as that of the traditional PVC pipes, PVC-O has a larger bore offering greater hydraulic capacity. It also offers excellent mechanical characteristics thanks to its fatigue resistance, elasticity and tensile strength.

Furthermore, PVC-O pressure pipes have a spigot and socket jointing system that enables fast, efficient and safe coupling, witnessed by nearly 1 km of 630 mm diameter pipe laid per day on a project, that must withstand a negative pressure for over 30 minutes which goes down to -0.8 bar – nearly a complete vacuum.

“During the first three decades of life of this product, there were some limitations such us standardization, manufacturing process, range of products and industrial efficiency.  These limitations have been rectified and offer numerous advantages at all stages of a project,” Venter says.

These include:

• during Design Phase: larger capacity, higher velocities, lower friction losses, lower embedded energy, lower life cycle cost and complete fitting range.
• during Construction Phase: lightweight, ease of handling, speed of construction, lower plant costs and ease of joining.
• during Ownership Phase: no cathodic protection, lower friction deterioration, service life in excess of 100 years and a “tried and trusted” asset.

Today, PVC-O pipe systems are manufactured locally by Molecor Pty Ltd, a joint venture between Sizabantu Piping Systems Pty Ltd and Molecor Canalizaciones Spain. Because it is SAPPMA’s focus to create consumer confidence within the Plastic Pipe Industry and to promote the production and the use of high quality plastic pipes and pipes systems, Venter stresses that the association is also keeping a close eye on PVC-O pipes entering the market and ensuring that they meet all quality standards.

“It is clear that there are many opportunities for large size PVC-O pipes in the medium-high pressure class. We are only starting to see the impact of PVC-O on our industry and anticipate that we will see much more research and development take place in the years to come.  Whilst manufacturers of PVC-O pipes still have to develop ways to extend their use and application value in those areas where they are not yet as strong as other materials, for example by increasing the range of products going larger to complete projects, erasing the need to combine materials and developing a rich range of fittings that can provide customers a system made of the same material, we will be watching the development of exciting new market with keen interest,” concludes Venter.

Sources:

• http://sizabantupipingsystems.com
• http://www.thinkpipesthinkpvc.com.au

Mike Smart, Genesis Consulting Imagineering SolutionsTel: (082) 555 2065Email: Mike@genesislabour.co.za