Plastic pipes for water supply - withstand temperatures from -70°C to 110°C (min and max temperature conditions are indicated), have a blue coating. For gas supply - has a yellow or orange color.
Production of PERT pipes
The HDPE pressure pipe is made of polyethylene and has a protective layer. Manufacturers use different coatings (protection) from modified additives, minerals, light and heat stabilized compositions based on propylene and polypropylene.
Connection methods
To connect pipes made of polyethylene with increased heat resistance, the same methods are used as for cross-linked PE:
- Sliding fittings. Installation is available to a specialist of any qualification. Mainly used for small diameter pipes.
- Crimp fittings. Polyethylene fills the entire docking space, so the connection is reliable and installation is quick.
- Electrofittings. The most reliable connection method.
- Flanges. It is used for pipes of large diameter and connection of sections of critical pipelines.
Connection of pe-rt pipes with pipes made of other material (PP, PA, PB, metal) transitional removable and non-removable couplings are used.
PERT pipe installation
Installation is carried out in several ways:
- Trench method, without the use of sand backfill.
- For laying are used incl. and gentle methods.
- Different types of drilling, for example, horizontal directional.
- Trenchless laying by the methods of punctures with a pneumatic punch.
- It is possible to lay in unstable soils using the plow-rotary laying method, as well as in other soils (rocky terrain, coarse-grained, excluding boulder, crushed stone, pebble-gravel).
- Rotary excavation - backfilling.
- Restoration in a trenchless way without dismantling the old one - relining.
- During the current repair of external systems - renovation.
Graphically, this is shown in Figure 4. Layered crystalline structures are connected through amorphous polymer segments, i.e. cross chains. The probability of the formation of cross chains increases with the length of the polymer chain.
Cross-chain molecules are known to increase the stiffness of a material and improve its flex crack resistance (ESCR) or long-term creep properties by "bonding" a plurality of crystals together. The side chains exhibit stretchability and mobility and as such can absorb and dissipate energy.
Figure 4: Cross-chain molecules increase compound stiffness
Cross-chain molecules increase ESCR and stiffness by "linking" multiple crystals
Cross chains are stretchable and mobile (can absorb/dissipate energy)
The type of introduced co-monomer also affects the concentration of cross chains. As the chain length of the α-olefin com-monomer increases, the cross-chaining ability also increases. Figure 5 shows that 1-octene is more efficient than the shorter α-olefins. The reason for this is that the side chains of octene are longer and therefore more difficult for them to incorporate into the growing crystal. This leads to a higher probability of cross chain formation at the same comonomer concentration.
Figure 5 : The type of comonomer affects the likelihood of forming cross-chain molecules
When designing a molecular structure, it is important to control the concentration of the comonomer and how it is incorporated into the polymer chain. Figure 6 shows a curve showing the relationship between molecular weight and the likelihood of cross-chain formation in ethylene-octene copolymers made using Dow's patented solution polymerization technology. By controlling the incorporation of co-monomer, different polymer morphologies can be obtained leading to a different balance of properties.
By applying these ideas, a new family of DOWLEX polyethylene compounds has been developed for the production of utility pipes.
Figure 6: Influence of Molecular Weight on the Probability of Formation of Cross-Chain Molecules
These developments form the basis for a new class of polyethylene materials for high temperature applications. These compounds are defined in the ISO-1043-1® standard as PE-RT or high temperature resistant polyethylene.
PE-RT exhibits excellent long-term hydrostatic strength without the need for crosslinking. This allows pipe manufacturers to gain significant processing advantages over cross-linked PEX. As defined in the ISO 10508 standard, PERT can be used in the production of any hot water pipes.
DOWLEX Polyethylenes have been successfully used in hot water pipe manufacturing for over 20 years, with more than 1,000,000 km of pipes already installed.
For potable water pipes, it is important to comply with national requirements for products intended to come into contact with water. These requirements include taste and odor characteristics, inhibition of microbial growth, and disclosure of material composition to ensure that all additives used in the production of that material are on the "positive list".
Due to good long-term hydrostatic strength at high temperatures, combined with excellent flexibility, DOWLEX 2344E and DOWLEX 2388 are the best solution for pipes for heating and water supply.
DOWLEX PE Pipe Compounds: Worldwide Certification
- Certified as non-crosslinked in the following countries: Austria, Australia, Canada, China, Czech Republic, France, Germany, Hungary, Iran, Netherlands, Poland, Russia, Slovakia, Slovenia, Spain, Switzerland, USA
- Approved for drinking water in Austria, Denmark, France, Germany, Italy, Netherlands, France, Russia, UK, USA.
Tubing made from DOWLEX 2344E exhibits excellent long-term hydrostatic strength at elevated temperatures without the need for crosslinking. This makes this product particularly suitable for the production of hot water pipes. Approvals for this material have been issued in a number of countries, for example DOWLEX 2344E complies with the German standard DIN 16833(6) (PE-RT) and the corresponding DIN 4721 application standard.: KIWA(8) approved for all hot water pipes in the Netherlands; and in the US, this material is listed on the PPI(9) list at 180°F (approx. 82°C). DOWLEX 2344E DOWLEX 2388 are the only non-crosslinkable polyethylenes in this class. Multilayer multilayer pipes meet the requirements of ASTM1282-01A00.
Pipes made from DOWLEX 2344E are extremely flexible, making them easy to install. It is possible to apply standard PE welding technologies without the need for crosslinking. In addition, the lack of crosslinking allows high production speeds to be achieved. This advantage is important for the production of multilayer composite pipes. The high smoothness of DOWLEX tubing reduces head loss and minimizes fouling.
The newest member of the DOWLEX family of polyethylene pipe compounds is DOWLEX 2388, an ethylene-octene copolymer manufactured using Dow's patented solution polymerization technology. This product is designed to combine excellent long-term hydrostatic strength with excellent machinability.
Benefits of PE-RT for pipe production
- Line speed > 60 m/min. without technological additives
- No loss of raw materials during start-up of the equipment, since the material can be recycled
- Saving time + production costs:
- No additional vulcanization step required
- No laboratory analysis required to determine degree of crosslinking
- Good taste and smell characteristics
- Excellent weldability
Figure 7 DOWLEX 2388 Ring Voltage Characteristics, Scanning Electron Microscope according to ISO 9080
As can be seen from Figure 7, the DOWLEX 2388 regression curves are very "sloping", resulting in high design stresses over long periods, especially at elevated temperatures. At a temperature of 110 °C, the failure time, which is much longer than one year, makes it possible to predict the service life of pipes at 70 °C over 50 years, at 60 °C about 100 years (using extrapolation indicators according to ISO 9080). The resulting design stress is not only comparable to cross-linked PEX, but exceeds it.
PE-RT is a modern and versatile polymeric material, characterized by a large margin of safety and high resistance to temperature effects. Type 2 PE-RT pipes can be used for heating, cold and hot water supply. They are also widely used to protect power supply and communication cables. Compared with other types of polyethylene pipes, PE-RT type 2 products have the following advantages:
Widest operating temperature range. Permissible constant temperature of the heat carrier is 95°С. At the same time, flexibility is maintained at sub-zero temperatures, down to -50°C, which eliminates the formation of cracks during storage and transportation in winter. When water freezes inside, pipes are also not damaged; after defrosting, they retain their original shape.
Corrosion and chemical resistance. PE-RT pipes are not affected by hard water and can withstand acidic and alkaline environments. There are no deposits on the walls of polyethylene pipes that reduce the throughput.
Flexibility and elasticity. Pipes of small diameters are suitable for hidden wiring and allow concreting. PE-RT pipes with a diameter of up to 110 mm inclusive can be supplied in coils, which allows such a pipe to be laid using a trenchless method, as well as inside old metal pipelines without dismantling them.
High working pressure. For pipes with sufficient wall thickness, the nominal working pressure is 16 atmospheres at a medium temperature up to 95°C. Thin-walled pipes are designed for constant pressure up to 10 atmospheres.
Fast installation. The length of the segment in the bay allows you to do without intermediate connections. It also reduces the amount of waste.
Low thermal conductivity minimizes heat loss in heating networks.
Reliable connection. PE-RT pipes can be welded in the same way as any other polyethylene pipes - butt-welded or with electrofusion fittings.
Using PE-RT pipes for cable laying
Type II PE-RT pipes are often used for cable installation. In this case, both standard pipes and pipes specially designed for this purpose with an additional protective layer can be used.
Manufacturers offer several options for pipes designed for laying power, telecommunications and signal cables, as well as fiber optic lines. For example, the company "Tehstroy" produces a series of pipes TEHSTROY TR (temperature resistant) made of polyethylene with increased heat resistance. High resistance to temperature fluctuations allows laying a pipe at any depth, including above the depth of soil freezing. Operating temperature ranges from -20°C to +95°C.
The TEHSTROY TR series includes single-layer pipes with a nominal outer diameter Dn and pipes with an additional protective layer, sold under the brand name Techstroy TR-1 Prosafe. The protective sheath, made of thermoplastic polymer, may be red or green. Both types of pipes are available in diameters from 16 to 630 mm, which allows you to choose the optimal size for both mains and single signal and communication lines.
The use of pipes with a protective layer makes it possible to lay pipelines directly into the ground, as well as along the bottom of reservoirs with or without penetration into the ground. The use of the HDD method often makes it possible to reduce laying costs, since it does not require excavation and greatly reduces the number of joints.
PE-RT pipe (type 2) is used in systems for drinking and drinking purposes, hot water supply, low-temperature water (up to 80 ° C) heating, water heated floors and walls, soil heating, as well as technological pipelines , transporting liquids that are not aggressive to pipe materials. Operating classes according to GOST 32415-2013 - 1, 2, 4, XB.
VALTEC PE-RT pipes are connected using press fittings (VTm.200, VTc.712), which are also used to connect metal-polymer pipes. Compression fittings VTc.4410, VTc.709 can be used for connections of "cone" and "Eurocone" standards. During the installation work, you should be guided by the instructions given in the technical data sheets for the specified fittings.
Estimated service life - 50 years. Delivery form - pieces 200 m long in bays. The cost of the pipe is indicated for 1 running meter.
Pipe VALTEC PE-RT
Technical characteristics of the Valtec polyethylene pipe:
Manufacturer: Valtec
Producing country: Italy
Pipe material type: Polyethylene
Scope of the pipe: For hot, cold water supply and heating systems
Pipe section: Round
Outside diameter: 16.0(mm)
Inner diameter: 12.0(mm)
Pipe wall thickness: 2.0(mm)
Maximum operating temperature: 80.0(deg.)
Maximum short-term admissible temperature: 90.0(deg.)
Guarantee period: 10 years)
Logistics: Supplied in 200m coils.
Buy Valtec pe-rt pipe for underfloor heating in Moscow in the company Teplodoma-msk