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). At Mibec we can supply a wide range of pre-insulated pipe products from leading district heating pipe manufacturers like Rehau, or our own Mibec DHP pipe. In this short article we look at the installation and whole-life cost benefits of using polymer pipes like cross-linked polyethylene (PEXa) for district heating projects.
When planning a district heating project the specifier will often have a choice of going down the steel pipe or flexible plastic pipe route. Traditionally 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 however, despite lacking the very high operating temperature of steel pipes, are starting to become very popular due to their improved flow characteristics and superb insulation performance allowing for lower temperatures to be used at the heat source – improving energy efficiency across the system.
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 coils (up to 250 metres) 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 required. 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. Going down the plastic pre-insulated pipe route will limit the number of fittings required which saves on time, costs and reduces the likelihood of any future leaks. 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 the advantage of single long pieces, pre-insulated pipes are also much lighter weight than steel alternatives (and therefore easier to move and handle on site), plus they are much easier to cut (needing only a normal hand saw). Also, because the pipes have such good flexibility it is also much easier to make the building connections; there will be fewer issues with lining up the various fittings because the installer has that extra degree of movement with the pipes to make final adjustments, saving time and hassle on site.
Plastic pre-insulated pipes also have the benefit of being more corrosion resistant than steel pipes. This has two advantages, firstly there is a reduced chance of leaks once in service, and plastic pipes have a longer service life. 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 fantastic benefit when considering 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 whole life costs. At Mibec, 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 district heating solution to meet your needs. Please feel free to email or call our support department on 01948 661639 where one of our trained advisers will be happy to help you.