20 years of moving forward with PVC pipe technology | Infrastructure news

Celebrating its 20th birthday this year, Sizabantu Piping Systems has grown from a trading company to one providing the marketing and sales function for a major South African thermoplastic pipe manufacturer – Molecor.

Sizabantu is a Southern African agent for a world leader in thermoplastic (PVC-O) pipe technology, Molecor, and is a joint venture partner in a production facility with Molecor in the Richards Bay Industrial Development Zone.

Significantly, all the Sizabantu management throughout Southern Africa are qualified and highly experienced people who have been in the thermoplastic piping system industry for many years. They know quality products, customer service, product availability and commercial competitiveness are paramount in this highly competitive market.

The company currently supplies high-quality, locally manufactured, thermoplastic piping system products into the Southern African market. The maximum diameter and pressure rating of the PVC-O pipes available are substantially greater than previously available and this has enabled Sizabantu to compete in markets that were hitherto beyond the scope of previously available thermoplastic piping systems.

PVC pressure pipes

PVC pressure pipes were first used in Germany about 85 years ago. About

60 years ago, PVC pipes were introduced into South Africa but were not enthusiastically received. Today, for example, more than 95% of domestic sewerage reticulation pipes are PVC. Things have changed.

Scientists, polymer technologists and processing engineers have enabled the Allowable Design Stress (σ) for HDPE to improve from 5 MPa to 8 MPa – a substantial 60% increase. However, the increase in PVC’s strength, enabled by improved technology, is even more substantial, going from 10 MPa to 36 MPa – a incredible 260% increase.

In the 1970s, the PVC industry entered the mining services market following a successful project, led by Dr Ken Hart. A high-impact pipe PVC-HI (SANS 1283) was developed that satisfied the mining industry’s requirements and enabled PVC pipes to be used for underground services.

Following on from this work, another development project, led by Mike Osry, developed PVC-M (SANS 966-2) in the mid-1990s by adding impact modifiers, commonly CPE (chlorinated polyethylene), or rubber toughened acrylics, or a combination thereof, to the PVC material to increase its impact strength. This enabled the material to exhibit ‘tough’ characteristics that facilitated the reduction of the Design Coefficient (C) from 2 to 1.4, thereby increasing the Allowable Design Stress (σ) from 12.5 MPa to 18 MPa.

About 40 years ago, PVC-O (oriented unplasticised polyvinyl chloride – SANS 16422) was developed. The molecular orientation process results in the improvement of physical and mechanical properties of the material. In the intervening 40 years, there have been improvements in PVC-O material: from Classification 315 material initially to Classification 500 material currently – the nomenclature represents 10 times the MRS (Minimum Required Strength) of the material.

The latest PVC-O material, Classification 500, must have an MRS of not less than 50 MPa at 50 years, that with a Design Coefficient (C) of 1.4 gives a σ-value of 36 MPa – where σ = MRS/C. It is a substantial improvement, which is twice the Allowable Design Stress (σ) of PVC-M. This is made possible by improved in-line production technology, which Sizabantu Piping Systems’ Spanish technology partner Molecor excels at developing, and the company’s TOM® 500 PVC-O pipes are produced locally in Richards Bay.

Innovation – TOM® 500 PVC-O

Innovation is one of Molecor’s core values. With TOM® 500 PVC-O branded pipes, the company increased the range of PVC-O pipes from the previous limit of 315 mm OD PN16 (PN is the working pressure in bar) to 630 PN25, with the M-OR-P3136 system in 2010. Then, in 2013, to 800 PN20, with the M-OR-P3180 system. Further to 1 000 PN16 in 2020 and 1 200 PN16 with the M-OR-P5012 system in 2021. Currently, the complete range of pipe diameters is available up to PN25. These are exciting developments for the thermoplastic pipe industry that have enabled it to compete in the large-diameter, high-pressure pipe market, which was previously beyond its capability.

These innovations and the latest high-technology polymers have enabled the service life of TOM® 500 PVC-O thermoplastic pipes to be greater than 100 years – which is now the duration demanded by owners and consultants. This is more than twice the ISO protocol requirement that thermoplastic pipes’ design service life shall not be less than 50 years, which is 438 000 hours on the polymer’s Creep Rupture Regression Curve.

This property of TOM® 500 PVC-O thermoplastic pipes is one of the cornerstones of Sizabantu’s success, together with its industry expertise, customer service culture and local manufacturing facility. These attributes have also enabled Sizabantu to grow its export business into Africa, with one of its largest irrigation schemes, in Angola, an example of the success in this market. They illustrate that despite the competitive nature of the market, they are succeeding and prove an axiom of today’s world – if you are standing still, you are probably going backwards.

PVC pipe technology has improved substantially, and is continuing to improve, thereby giving the pipeline industry proven materials to use for large-diameter, high-pressure, bulk supply pipelines – a market that steel and ductile iron have dominated historically. PVC-O pipes are lightweight, have a negligible friction increase over time, do not corrode, do not require expensive cathodic protection, give labour-intensive emerging contractors equal opportunity to compete, have extremely high impact strength, low creep, low celerity and extremely low embedded energy – maybe it is the material to help save the Earth?

As government, metros, municipalities and local authorities strive to provide services to more people – with an ever-increasing demand, and limited funding – the advantages of using
TOM® 500 PVC-O thermoplastic pipes and fittings become self-evident.

The future prospects appear to be promising for the product. More than 4 km of 1 000 mm OD PN16 pipe have already been supplied and installed in Europe in 2021 and the first 1 000 mm OD pipes are expected to be supplied in South Africa in 2022. This will be another significant milestone for the South African thermoplastic pipe industry.

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