200 Years of Plastic Pipes?

Through a long running and successful joint initiative, the Plastics Pipes Liaison Group, members of Water UK and the BPF Pipes Group have updated and published one of the fundamental building blocks to achieving a leak-free pipeline: the specification for fusion jointing of polyethylene pipes, or WIS 4-32-08: Issue 4 “Fusion jointing of polyethylene pressure pipeline systems using PE80 and PE100 materials”. 

Ensuring best practice techniques will protect the UK’s pipe network for generations to come

Background

The UK water industry, constantly striving for new solutions to technical and financial challenges, has pretty much tried every material or renovation option on the market.  This was particularly the case in the 1980s when major infrastructure renewal got underway in large volumes, using spray linings, cured in place linings, ductile iron, PVC, polyethylene, GRP and other options.  What we have seen is a maturing of this approach and standardisation to a tighter set of solutions.  Water utilities and manufacturers are confident that well designed and well installed plastic piping systems which genuinely survive in service for more than 100 years are now a real option.  

We have experience of pipes in service for more than 50 years on far inferior polymer materials to those offered today.  There is a huge body of science that is now debating not just 100 years but the potential for over 200 years in some applications like drinking water supply.  We have a pipeline system which can demonstrate its value as a reliable asset, its versatility in terms of how you get it into the ground, and the ability for rapid return to service of supply infrastructure to consumers.  

Through the collaboration of water industry and manufacturing, it has been possible to openly share knowledge of construction methods and failure modes: using these as a basis for optimising the solution to meet the need for a long-life asset.  This has led to the recent publication of WIS 4-32-08: Issue 4 “Fusion jointing of polyethylene pressure pipeline systems using PE80 and PE100 materials” which provides the opportunity for pipeline installers to follow best practice and truly deliver a long-lasting asset.

Polyethylene pipes already minimise leakage through reducing the number of joints required by supplying continuous lengths in coils.  The solution for a pipe system that will last for more than 100 years is to have a compatible jointing system that will last just as long.

Compatible – the changes to the specification allow utilities to comply with the Public Procurement Directive by aligning requirements with the European Standard for “Plastics piping systems for water supply, and for drainage and sewerage under pressure.  Polyethylene (PE)”, EN 12201. In particular, the tests used to assess the integrity of completed joints now match those used by manufacturers in type testing the products in the factory.  It is possible to measure the quality of the joint throughout the supply chain. 

Correct – “All animals are equal but some animals are more equal than others” (George Orwell, Animal Farm) and so it is with products and equipment.  By purchasing pipes and fittings which have been tested and certified to BS EN 12201 parts 1 to 3, the water industry is already giving itself the best possible chance of installing a pipeline system fit for the expected lifetime.  So it is when choosing welding equipment and welding services.  The 4th edition of WIS 4-32-08 reflects the trend to ‘fully automatic’ machines and was released to equipment manufacturers in June 2016 to allow time for updating software to match the improved processes in the specification. 

Clever – pushing together surfaces of molten polymer has great potential for a fully fused joint, or through bad alignment and insufficient pressure/time could be the weak link in the whole pipeline.  After much research work into the optimal conditions for heating and cooling, this specification includes a requirement for the pipes to be held in alignment clamps at a given interface stress for the full cooling time.  The cooling times and guidance for jointing at low temperatures have also been amended to offer improved joint performance and onsite resilience. 

Competent – with compatible and high quality products, optimised processes and welding equipment, the final piece in the jigsaw is subject to the human factor.  The updated specification seeks to clarify best practice and provides a solid foundation for the training of installers.  Plastic pipes are very much moving to standard designs for use within utility infrastructure.  They are benefiting from research and engineering which is now confidently predicting systems that can last in excess of 100 years and we can see a big picture that tells us it is worth mastering welding techniques on site to get the solutions we want.  

Collaborative - the Plastics Pipes Liaison Group are hosting a workshop on Wednesday 2nd November (at BPF House, London) to explain the improvements to WIS 4-32-08.  The commitment of the whole supply chain can together ensure that our future water supply system is built on these strong foundations. 

Author: Julia Trew 

As Standards Manager for the British Plastics Federation (BPF) Pipes Group, Julia works closely with the UK’s leading manufacturers of plastic pipes and fittings to coordinate their input into UK and international product and test standards.  A graduate of Materials Science from Bath University, she spent over 25 years at the Water Research Centre (WRc), working on a diverse range of projects and helping to develop key Codes of Practice in water and waste water pipes and sewers.  She is a Chartered Engineer and a Member of the Association for Project Management and the Institute for Materials, Minerals and Mining.