As the UK looks to transition away from fossil fuels, district heat networks are being increasingly recognised as the ideal solution to supplying energy efficient heat and hot water. Recent schemes such as the £338 million Heat Network Transformation Programme highlight the clear role that these heating systems will play in achieving the Government’s low-carbon ambitions.
In the past, heat networks have been allied to gas boilers or combined heat and power installations, with heat generated by way of these systems. Today, district heating benefits from the growth in low carbon heat sources, with heat pumps and waste heat systems some of the most popular alternatives.
With this technology evidently here to stay, it’s important to address some of the lingering questions surrounding these systems. Namely, what kind of district heating pipework should be used for an installation?
While opting for pipework that is thermally insulated with PUR foam should be key to minimising heat losses, underground heating pipes come in a variety of formats, so understanding the distinctions is critical.
Steel has traditionally been the material of choice for underground pre-insulated pipe. Thanks to years of use in the sector, its benefits are well known. As the most commonly used district heating pipe, steel solutions are available in very large sizes and can withstand high operating temperatures of over 90°C.
However, they are not without their limitations. The installation of steel pipework necessitates the use of welding, which draws up a series of challenges. Primarily, workers must be specially trained to undertake any steel pipe welding, while the use of an open flame naturally presents a health and safety risk.
Additionally, this jointing process can often prove lengthy, especially when compared to alternative installation methods. More joints are needed on steel networks due to the requirement for expansion loops in the ground, in turn necessitating more pre-fabricated elbows and hence, welds.
Finally, perhaps the most well-known potential downside of steel pipe is corrosion. If the installation is not performed to a high standard, there can be water ingress at the joint. This groundwater may reach the steel carrier pipe and corrode it over time, which may lead to pipe failures, leaving end users without heating and water.
Here, contractors should consider the benefits of polymer pre-insulated pipework over steel for their district heating system. Polymer solutions have many advantages over steel, especially as flow temperatures of new district heating networks are coming down.
While it may be true that steel pipe is available in larger sizes, polymer heat networks require fewer custom articles as the tees make use of standard items. Polymer pipe is also available in long coils, reducing the number of joints needed, allowing for savings on installation time and materials.
Here, opting for pre-insulated flexible pipe such as REHAU’s RAUTHERMEX can provide contractors with an even greater sense of flexibility on site, meaning obstacles or other utilities buried in the ground can be easily avoided. Polypropylene (PP-R) pipes are also ideal for large heat network spines of 160mm to 315mm, creating a fully polymer pipeline heating system.
What’s more, pre-insulated PE-Xa pipework can be installed without need for welding, instead making use of the bespoke Everloc jointing system. This facilitates a quick and easy installation for either a mechanical or civil contractor.
Lastly, unlike steel, polymer pipework has excellent corrosion resistance, even after years of extensive use. This gives the contractor confidence that their district heating project will be future-proofed against wear and tear, mitigating the need for potentially costly repairs later on.