Underground pre-insulated pipes are used in district heating schemes to connect the various buildings on the site to a centralised heat source. The pre-insulated pipes are designed to maintain the water temperature when in transit (avoiding heat losses to improve energy efficiency). When planning a district heating project the designer will often have a choice between specifying steel or polymer pipes such as cross linked polyethylene (PEXa). Historically district heating schemes in the UK have used steel pipework to meet the high operational temperatures that are needed to compensate for their heat losses over large distances. Plastic pipes are now starting to become very popular due to their improved flow characteristics and superb insulation performance compared to steel pipes allowing for lower temperatures to be used at the heat source – improving energy efficiency across the system. Nowadays it is possible to specify some very large projects in plastic, recently REHAU, one of our key partners supplied 80km of RAUTHERMEX to the bioenergy village of Lathen in Germany of 11,000 residents. In this short article we look at some of the cost and other advantages of using polymer pipes.
Plastic pre-insulated pipes are extremely flexible and lightweight allowing for rapid installation and the ability to easily navigate over or around obstacles (such as trees and existing buildings) on site. Due to the flexibility of the pipe they are supplied in long coils allowing for easy transport, delivery and storage on site. The pipe is also easy to handle; the installers can roll out the pipe straight into the pre-prepared trench directly from the coil (either by hand for smaller sizes or using a de-coiler). The ability to keep the pipe in a single long flexible piece has many advantages in terms of limiting the number of joints and connections required compared to steel which saves on time, costs and reduces the likelihood of any future leaks. The cost savings can also be very significant, a recent case study presented by consultants 3D Technical Design Ltd at one of REHAU district heating workshops, showed savings of 45% (totalling over £251,000 on a project of 120 dwellings) by switching to polymer from steel with efficiencies spread across jointing costs, civils, prelims, pipe laying costs and commissioning.
A reduction in joints will also mean less pipe cutting and less fittings to individually insulate to maintain the heat loss performance. In addition to fewer joints due to single long pieces, plastic pre-insulated pipes are also much lighter weight than steel alternatives (and therefore easier to move and handle on site). They are also very easy to cut (needing only a normal hand saw) and because the pipes have such a high degree of flexibility it easy to make the building connections – the installer will have a high degree of movement with the pipes for aliment and making any final adjustments thereby reducing time and hassle on site. Steel systems don’t have this sort of flexibility and therefore will require many more connections to be made on site to join the pieces together and get them to line up accurately.
Plastic pre-insulated pipes also have the benefit of being more corrosion resistant which means a longer service life and the ability to offer increased warranties when compared to steel insulated pipe. All of this means that plastic pre-insulated pipes will require less maintenance, have a reliable performance level over time, and will need replacing less often. This is a superb benefit for designers and building owners when considering the environmental impact and whole-life costing for a project.
As can be seen, plastic pipes have some great benefits for district heating projects in terms of planning, installation, maintenance and project costs. At Mibec we offer a wide range of plastic pre-insulated pipes from leading pipe manufacturers like Rehau, or our own Mibec DHP pipe. Pipes are available in a wide range of sizes and options are available for both heating water and potable hot water. We offer a full free of charge specification service covering the whole of the UK, designed to support architects, specifiers or contractors, helping you to select the right pre-insulated solution to form a full system to meet your needs. Please feel free to email or call our support department on 0330 053 880 (local call rate) where one of our trained advisers will be happy to help you.