FibreFlex® Pro: The Future of District Heating Pipes Explained

Revolutionizing District Heating:
Discover how FibreFlex® Pro by RK Infra is setting new standards in district heating infrastructure. Combining the durability of steel with the flexibility of plastic, this innovative pipe system delivers superior energy efficiency, rapid installation, and long-term performance across diverse environments.

At RK Infra, we are committed to delivering high-performance, energy-efficient solutions for modern district heating systems. FibreFlex® Pro represents the pinnacle of flexible pre-insulated pipe technology, offering the strength of steel with the versatility and efficiency of plastic. Engineered to meet the demands of contemporary heating infrastructure, FibreFlex® Pro combines robust mechanical properties, outstanding thermal insulation, and rapid installation advantages, making it an ideal choice for municipalities, energy utilities, and industrial applications.

Table of contents:
Key Features of FibreFlex® Pro
1.1 High-Performance Construction
1.2 Designed for Efficiency and Longevity
UNO vs DUO: Selecting the Right Configuration
2.1 UNO (Single Pipe)
2.2 DUO (Twin Pipe)
2.3 Configuration Comparison
What makes FibreFlex Pro Stand Out from Other Plastic Pipes?
Installation Advantages
Application Areas
System Integration and Accessories
Proven Performance in Real-World Projects
Conclusion

Key Features of FibreFlex® Pro

• High-Performance Construction
  FibreFlex® Pro features a cross-linked PE-Xa carrier pipe reinforced with high-strength aramid fiber, providing exceptional mechanical resistance while remaining lightweight and flexible. The pipe is insulated with high-performance PUR foam and protected by a durable corrugated polyethylene casing.
• Operating Temperature:
  • Up to 95 °C continuously; 115 °C peak Pressure Rating: 10 bar (standard), with a 16 bar option available (FibreFlex® Pro 16)
  • Thermal Conductivity: λ50 = 0.021 W/mK (cyclopentane-based insulation)
• Designed for Efficiency and Longevity
  FibreFlex® Pro is engineered for a minimum service life of 30 years (even 50+ years depending on projected temperature/ pressure), maintaining thermal and mechanical performance even under demanding operating cycles. Its low heat loss properties significantly enhance energy efficiency in both new and retrofit district heating networks.
• Up to 46% lower heat loss compared to conventional steel systems
• Extended coil lengths reduce the number of joints, lowering installation time and risk of leakage
• Available in UNO (single pipe) and DUO (twin pipe) configurations

Installation Efficiency
Thanks to its flexibility and long coil lengths (up to 770m for certain diameters), FibreFlex® Pro enables streamlined installation with minimal jointing. This translates into reduced trenching requirements, faster project timelines, and lower overall labour costs.

• Compatible with standard PE-Xa tools (up to DN 110)
• Utilizes press couplings: no pipe expansion required
• Pre-insulated steel press transitions available for seamless system integration
• Ideal for a Wide Range of Applications
  FibreFlex® Pro is designed to support diverse use cases across residential, commercial, and industrial sectors:
  • District heating networks in urban and suburban settings
  • Renewable energy systems, including geothermal energy, biomass and biogas
  • Industrial process heating requiring flexible and high-pressure distribution
  • Mountainous or space-constrained terrains where traditional piping is impractical
• Full-System Integration with RK Infra RK Infra provides:
  • a complete piping ecosystem, including accessories, jointing systems, and installation tools, ensuring maximum compatibility and long-term performance.
  • Our team offers technical support from planning through commissioning, enabling seamless integration into your infrastructure.
  • CLICK half-shell insulation systems for joints besides standard pre-insulated steel fittings
  • Certified components meeting ISO 9001 and OFI CERT standards
  • Pre-insulated accessories, including valves and bends, available on request

UNO vs DUO:

Selecting the Right Configuration:
FibreFlex® Pro is available in two configurations:

• UNO and DUO, to accommodate the specific thermal distribution needs of each project.

UNO (Single Pipe Configuration):

• • • The UNO version consists of a single pre-insulated carrier pipe.
    • It is typically used for:
      • Supply-only lines (e.g., from a heat source to a substation)
      • Return-only lines in systems where supply and return need to be laid separately
      • Projects where maximum layout flexibility is required

Advantages:

• Easier to route individually through tight spaces or complex layouts
• Ideal for retrofit projects or staggered trench designs 

DUO (Twin Pipe Configuration)

• The DUO version contains two carrier pipes, supply and return, pre-insulated within a single casing.
• This setup is especially beneficial in:
  • Symmetrical heating circuits
  • Long-distance heat distribution where laying two UNO pipes would double trenching costs
  • Projects seeking faster installation and reduced ground disturbance

Advantages:

• Single trench and faster installation
• Lower total heat loss due to shared insulation space
• Ideal for compact installations in urban environments

Which Should You Choose?

The decision between UNO and DUO depends on:

• Project layout constraints
• System design (centralized vs. decentralized)
• Trenching capacity and civil engineering costs
• Desired level of thermal efficiency

Our engineering team at RK Infra can assist with configuration planning based on your system's hydraulic design and site requirements.

What makes FibreFlex Pro Stand Out from Other Plastic Pipes?

While there are many plastic-based pre-insulated pipe systems on the market, FibreFlex® Pro distinguishes itself through advanced engineering, superior performance, and long-term value. Below is a breakdown of how it outperforms conventional plastic piping solutions in district heating applications.

• Reinforced Hybrid Structure
  Most plastic pipes rely solely on the strength of their polymer material. FibreFlex® Pro goes further by incorporating a PE-Xa carrier pipe reinforced with aramid fibre, the same high-performance material used in aerospace and protective gear. This reinforcement significantly enhances its resistance to internal pressure and thermal expansion. Benefit: Higher pressure rating (up to 16 bar), minimal elongation, and dimensional stability at elevated temperatures.
• Higher Operating Temperatures
  Standard plastic pipes typically have a lower thermal threshold.
  • FibreFlex® Pro is designed for: 95 °C continuous operation 115 °C peak temperatures
    This enables its use in medium- to high-temperature district heating networks, including biomass and CHP applications, where conventional plastic systems would degrade over time.
• Exceptional Thermal Insulation Thanks to its cyclopentane-blown PUR foam insulation, FibreFlex® Pro achieves a thermal conductivity of 0.021 W/mK, among the lowest in its class. Many plastic alternatives use less efficient insulation materials, resulting in higher heat loss. Benefit: Reduced operational energy consumption and lower lifecycle costs.
• Longer Coil Lengths, Fewer Joints FibreFlex® Pro is delivered in coils of up to 770 m, depending on diameter, far exceeding the jointing intervals of traditional plastic or steel pipes. Fewer joints translate directly to:
  • Lower installation time
  • Reduced risk of leakage
  • Decreased maintenance over the pipe’s lifespan
• Certified Lifespan and Performance
  Whereas many plastic pipes are tested under ideal conditions, FibreFlex® Pro is certified for a 30-year lifespan under real-world thermal cycles, validated by European third-party testing bodies. Standards compliance: ISO 9001, OFI CERT, DIN 8077/78 and EN ISO 15874
• Installation Compatibility
  Unlike some plastic systems that require specialized tools or expansion techniques, FibreFlex® Pro: Is compatible with standard PE-Xa tools (up to DN 110)
• Uses mechanical or press couplings, eliminating the need for hot works or specialized fusion welding

Installation Advantages

• One of the key strengths of FibreFlex® Pro is its efficiency during installation, which directly translates to lower project timelines and reduced total cost of ownership. Flexible Coils up to 770 m: Long continuous pipe runs minimize the need for connections, reducing both labour costs and potential points of failure.
• Minimal Trenching Required: The flexibility of the pipe allows it to follow the natural contours of the terrain, reducing the need for extensive excavation.
• Tool Compatibility: FibreFlex® Pro is compatible with standard PE-Xa tooling up to DN 110, eliminating the need for specialized or costly equipment.
• No Hot Works Required: Mechanical and press couplings enable quick and secure connections, enhancing site safety and efficiency.
• Fast Joint Insulation: Our CLICK half-shell system enables rapid joint insulation, speeding up installation in all weather conditions.

Application Areas

FibreFlex® Pro is engineered for versatility and durability, making it suitable for a wide range of district heating and thermal distribution systems, including:

• Municipal District Heating: Ideal for new developments or retrofitting aging networks in urban and suburban areas.
• Renewable Energy Systems: Optimized for use with biomass, biogas, geothermal, and combined heat and power (CHP) systems.
• Industrial Heat Networks: Handles the pressure and temperature demands of large-scale industrial operations.
• Rural or Mountainous Terrain: High flexibility and lightweight design make FibreFlex® Pro particularly effective in difficult-to-access or uneven topography.
• Campus and Facility Heating: Universities, hospitals, and large commercial complexes benefit from the system’s efficiency and low maintenance requirements.

System Integration and Accessories RK Infra offers a complete piping solution, with all necessary accessories and support systems to ensure full compatibility and long-term system integrity:

• Press Couplings: Secure and tool-compatible for all standard installations.
• Steel Press Transitions: Pre-insulated and ready-welded for connecting FibreFlex® Pro to metal-based systems.
• CLICK Insulation Shells: Quick-to-install joint insulation, improving on-site productivity and ensuring consistent thermal performance.
• Valves, Bends, and End Caps: All components meet industry certifications and are designed for long-term operation in buried environments. Our technical team can assist with complete system planning, hydraulic calculations, and thermal loss estimations to support a successful installation.

Proven Performance in Real-World Projects

FibreFlex® Pro is already trusted across Europe and beyond, with installations that highlight its technical and operational advantages: In a recent 4 km district heating project, FibreFlex® Pro delivered:

• 46% lower heat loss than a comparable steel system
• 80% fewer joints, significantly reducing installation time and future maintenance needs
• Successfully deployed in residential developments, industrial parks, and renewable energy plants, including alpine regions where temperature fluctuations and difficult terrain present unique challenges.

These outcomes confirm FibreFlex® Pro’s capability to perform under real-world conditions and demonstrate its reliability in both centralised and decentralised networks.

Conclusion

FibreFlex® Pro by RK Infra offers a technically advanced, future-ready solution for district heating infrastructure. With its reinforced hybrid construction, exceptional thermal performance, and rapid installation benefits, it outperforms both traditional plastic and steel systems. Whether for urban networks, industrial facilities, or renewable energy integration, FibreFlex® Pro provides the durability, flexibility, and efficiency required for modern energy distribution. For technical data sheets, case studies, or project-specific consultations, contact our team or explore our product range on the RK Infra website.