PE-RT (Polyethylene of Raised Temperature resistance) pipe is a medium-density polyethylene pipe produced using a special molecular design and synthesis process. By copolymerization ethylene with octene and controlling the number and distribution of side chains, a unique molecular structure is achieved, enhancing the heat resistance of the pipe.
PE-RT pipes can withstand temperatures up to 60°C, thanks to the presence of short octene side chains that prevent the polyethylene molecules from crystallizing into a single sheet.
This structure maintains the pipe’s flexibility, high thermal conductivity, and chemical inertness while improving its pressure resistance, making it suitable for long-term hot water transport below 60°C. Additionally, PE-RT pipes retain excellent low-temperature flexibility,impact resistance, and are environmentally friendly, being non-toxic, odorless, and recyclable. They can also be joined using heat fusion, simplifying installation and maintenance.
Differences Between PE-RT and PE-RT Type II Pipes
1. Raw Materials:
○ PE-RT pipes are made by copolymerization medium-density (MDPE) or linear low-density polyethylene (LLDPE) with octene.
○ PE-RT Type II pipes are made by copolymerization high-density polyethylene (HDPE) with hexene or butene.
2. Molecular Density:
○ PE-RT Type II pipes have a molecular density between 0.942 and 0.96, which is higher than that of standard PE-RT pipes (density below 0.942). This higher density results in greater hardness.
3. A common on-site method to differentiate the two types involves heat fusion welding.
Under the same temperature and heating time, PE-RT Type II pipes will have smaller,harder weld beads compared to standard PE-RT pipes, which have larger, softer weld beads.
4. Pressure and Heat Resistance:
○ PE-RT pipes are highly susceptible to creep at temperatures around 70°C,making them unsuitable for high-temperature systems. They are best used for low-temperature hot water systems below 60°C.
○ PE-RT Type II pipes offer greater pressure and temperature resistance,suitable for hot water systems operating between 70°C and 95°C. Their performance remains stable even under high temperatures.
5. Application:
○ PE-RT pipes are typically used in small-diameter underfloor heating systems and other low-temperature applications, such as DN16, DN20, and DN25 piping.
○ PE-RT Type II pipes, with their superior resistance to temperature, pressure,and corrosion, are used in urban heating, hot spring water transport, hotels,hospitals, schools, airports, chemical plants, oil and gas industries, and renewable energy systems.
Characteristics of PE-RT Pipes
● Lightweight and easy to transport and install.
● Excellent flexibility, allowing for coiling and bending, which reduces the need for fittings and lowers installation costs.
● Stress relaxation at bends, preventing “spring back” and facilitating easier installation.
● Low friction loss, providing 30% greater fluid transport capacity compared to metal pipes of the same diameter.
● Superior low-temperature resistance, allowing construction even in winter without needing to preheat the pipe.
● High chemical resistance, non-corrosive, and long-lasting.
● Suitable for use in environments with a working temperature of 70°C and a pressure of 0.4 MPa, with a service life of over 50 years.
● Free of toxic additives, with smooth inner walls that resist scaling and bacterial growth, making them safe for drinking water.
● Impact resistance is five times higher than that of PVC-U pipes.
● Excellent heat and pressure resistance, with reliable, leak-proof connections through heat fusion or mechanical joining.
● Environmentally friendly, with recyclable materials.
● Can be used safely under high-temperature conditions for over 50 years.
● Outstanding resistance to frost and impact, making them ideal for winter construction.
● Non-toxic, odorless, and suitable for safe drinking water applications.
● Available in coil form for flexible use.
● Recyclable heat fusion materials offer environmental benefits.Special Features of PE-RT Pipes
1. Durability: PE-RT Type II pipes have significantly better heat and pressure resistance compared to standard PE-RT pipes, ensuring a longer service life.
2. Flexibility: PE-RT pipes are highly flexible, making them easy to bend and ideal for underfloor heating installations.
3. Safety and Convenience: The unique properties of PE-RT Type II pipes ensure safer connections and easier repairs.
4. Environmental Benefits: Both types of PE-RT pipes are environmentally friendly.PE-RT Pipe Heat Fusion Welding ProcessFor heat fusion socket welding, follow these key steps:
1. Control the welding machine temperature: Set the temperature between 240-260°C.
2. Speed: Ensure quick and precise insertion of the pipe and fitting into the mold at the moment of extraction from the welding machine.For larger diameter PE-RT pipes, a butt fusion process is recommended:
1. Fix the pipe: Secure the pipe and fitting in the welding machine, ensuring they are aligned on the same plane.
2. Plan the pipe ends: Clean and plane the ends before heating.
3. Heat and weld: Preheat the machine to 210-220°C, then heat the pipe ends. The melting time depends on the wall thickness. After heating, apply pressure to join the ends and hold until they cool.
4. Inspect the weld: After cooling, inspect the weld for uniformity and strength.
Choosing the Right Pressure Rating
When the water temperature is between 50-70°C, use S5 class 1.25 MPa series pipes and fittings. For temperatures between 70-85°C, S4 class 1.6 MPa pipes are recommended.
For diameters between DN20-110, use heat fusion socket welding, and for DN110-500, use butt fusion welding.
Electrofusion Welding in PE-RT Pipe Networks
Electrofusion welding is complex and requires skilled operators to avoid issues like cold welding or leaks, which could compromise safety. Due to its complexity and cost, it is generally used only in special situations where traditional welding methods are impractical.
For summary, PE-RT pipes, made from a special medium-density polyethylene, offer excellent flexibility, heat resistance, and durability, making them ideal for hot water systems below 60°C. They are environmentally friendly, recyclable, and maintain their performance even in low temperatures.
PE-RT Type II pipes, with higher density and better pressure and heat resistance, are suitable for more demanding applications, such as urban heating and industrial hot water systems. Both types of pipes can be easily installed using heat fusion welding, ensuring reliable, leak-proof connections.
