Our flexible and rigid pipes for local heating and district heating

Explore our range of district heating pipes and remote heating pipes in this overview, along with other cutting-edge products for the expansion of pioneering energy supply systems.

For some, the initial question might be: how does district heating actually work? District heating is a form of heat supply that provides buildings with space heating and hot water. The thermal energy comes from so-called heat centres, where it is generated using various processes; for example, by burning waste and biomass. Waste heat, waste water as well as surface and ground water are also potential energy sources. Furthermore, solar district heating is becoming increasingly popular – huge collector fields now supply entire urban areas.

Thermally insulated pipe systems transport the thermal energy from the plant or power station to the customer. Hot water flows through these pipes and acts as the transport medium. The underground pipe systems, together with the heat centre (at least one, but depending on the demand and capacity, possibly multiple centres) form a district heating network.

When we talk about “local heating” or a “local heating network”, we are usually referring to a smaller heat supply system with pipelines that cover shorter distances. By contrast, if the pipelines stretch for around five kilometres or further, the system is usually referred to as a district heating network.

But back to the cycle: at the building, a heat exchanger converts the incoming thermal energy into heating energy. This process is essential since it allows the heat to be utilised for heating and hot water inside the building. Heating pipes then distribute the heat to the individual rooms. Once all the thermal energy has been consumed, special return pipes transport the cooled water back to the heat centre.

The next question that arises relates to the rapid pace of development in recent years: why are more and more municipalities and cities promoting the expansion of district heating networks? And what makes this form of energy supply so attractive to consumers? District heating offers many advantages: firstly, this supply model delivers carbon-neutral energy. But that’s not all. The thermal energy is always generated nearby, or at least within the local region. The heating plants are usually no more than 20 kilometres from the point of use. As the networks are manageable and operated by regional providers, customers benefit from a high level of supply security.

District heating is also economical and efficient in operation – suitable for traditional radiators as well as underfloor heating systems. This heating model is also a very space-efficient alternative: the heat exchanger is compact and takes up very little space compared to other heating systems. Additionally, there is no need for extra tanks or storage systems – only heating pipes are required. Because the heat arrives on demand via the underground pipes, the consumer doesn’t need to worry about anything else. Regular fuel procurement is no longer necessary, saving the consumer time and inconvenience. And because the domestic appliances require very little maintenance, district heating customers benefit from the lowest financial outlay compared to most other heating systems. For all these reasons, a growing number of cities and municipalities are developing or expanding district heating networks. Because the demand is there, and it’s high.

For local and district heating networks, we sell flexible and rigid pipe systems as well as a leakage monitoring device. Depending on the project-specific requirements, each pipe solution has its own unique strengths. Not least because rigid systems offer different advantages compared to flexible ones. The latter are usually made of plastic and can be easily adapted to the course of the trenches. Thanks to an extensive range of special moulded parts and accessories, even curved installations are possible with rigid pipe systems – although this remains more labour-intensive. In the early days, when district heating began to slowly establish itself as an alternative on the market, only rigid long-distance pipes were laid to transport the heating medium. At that time, however, far fewer components were available, which limited the freedom of planning.

However, rigid pipe systems have caught up considerably since then. On the other hand, flexible pipe systems made of PE (polyethylene) are increasingly achieving better values in terms of insulation performance – which doesn’t mean that rigid models are far behind in this regard. Quite the opposite: we use PUR (polyurethane) as thermal insulation in our district and local heating pipes. This type of insulation is extremely effective and perfectly complements the strengths of pure stainless steel pipes. Furthermore, in terms of connection technology, the two types of pipe are now also on a par. We establish connections within each system through various methods such as welding, pressing, plugging, pushing or clamping, using different apparatus like sleeves, screws, and flanges. When making a final choice as to the most suitable pipe system, factors such as the connection technology and accessories are less important – the main focus should be on the respective product properties.

When it comes to applications in the low-temperature operating range up to 95°C (fluctuating), our CALPEX PUR-KING product is number one. This innovative product achieves the best values worldwide in thermal conductivity measurements. Its lambda value is just 0.0199 watts per metre and Kelvin. Independent and accredited institutes have confirmed our claims about these almost negligible heat losses – ensuring guaranteed energy efficiency. Additionally, our patented CALPEX PUR-KING is self-compensating and suitable for continuous installation.

With FLEXSTAR, we offer a pipe system specifically for the local heating sector and for connections to heat pumps, whereby the focus is on maximum flexibility. At the same time, this pipe is sturdy, enables highly efficient pump operation and is thermally insulated with PUR insulation.

We highly recommend our CASAFLEX pipe system as a multifunctional district heating pipe. By “multifunctional” we mean self-compensating, self-venting, self-cleaning – naturally, it is also thermally insulated and continuous. CASAFLEX is designed for operating temperatures up to 160°C (fluctuating) (max. 180°C temporarily), operating pressures up to 16/25 bar and is used both as a main pipe and for building connections. Depending on requirements, the pipe system can be equipped with a single internal carrier pipe or a double pipe.

The last flexible pipe system in our line-up is our FLEXWELL DISTRICT HEATING CABLE. Although it can be laid flexibly, it is a double-walled steel casing pipe system. Both the carrier pipe and the exterior pipe are made of stainless steel. The design allows high temperature and pressure loads – in case of an overload, optional monitoring wires signal potential micro-damage. FLEXWELL is typically used in deep trenches as well as in higher-lying soil, i.e. directly below the surface. This pipe system can be installed underground using horizontal drilling methods, eliminating the need to excavate trenches.

Our rigid pipe systems include PREMANT, SPIRAMANT and the classic steel casing pipe system manufactured by our subsidiary ISOBRUGG. PREMANT is a thermally insulated system with a robust and corrosion-resistant plastic casing pipe. It also has a monitoring option. Because it is used as both a main or distribution line in district heating networks and for transporting temperature-sensitive fluids, PREMANT is considered a genuine universal solution within our product family. SPIRAMANT is also thermally insulated – designed to withstand high temperatures, it features a flame-retardant folded spiral steel casing pipe that protects the environment during the transport of thermally insulated liquids. SPIRAMANT can be installed either as an above-ground pipeline or inside buildings. Our steel casing pipe system is also suitable for high temperatures, but unlike SPIRAMANT it is double-walled and compatible with a flexible range of media. This pipe system can conduct not only liquids but also condensate, steam and gases. For this reason, it is recommended not only for district heating but also for industrial applications and process heat systems.

What distinguishes local heating pipes from district heating pipes? What are the crucial factors for each pipe system? As mentioned earlier, both terms refer to the same basic principle of thermal energy supply. Therefore, the distance between the heat centre and the point of consumption determines whether it is – strictly speaking – a local or district heating network. At the same time, the transport route is a key criterion to consider when expanding the network, especially when choosing the right pipeline system. In this context, the question arises: which pipe system fulfils the terrain requirements and is best suited for the planned distances within the heating network? Since the function of local and district heating pipes is essentially the same – transferring thermal energy via a medium – this is the only major difference between the requirement profiles for local and district heating pipes. A district heating pipe is usually longer, whereas a local heating pipe is cut shorter. The length measurement, in turn, influences the material properties, specifically the trade-off between stability and flexibility.

To give you the choice, we offer a flexible pipe system, FLEXSTAR, and a rigid system, PREMANT, which are specially designed for local heating networks. It is not possible to give a generalised answer with regard to the best choice of local heating pipe. A final recommendation can only be made after weighing up all the relevant factors in each individual case.