Do you dream of comfort? Do you want a warm floor in winter, and in summer - cold ceiling and walls? All this can be achieved with modern polyethylene pipes: cross-linked PEX and heat-resistant PERT. They can be installed without the help of specialists with your own hands. Read the article about how to select and install polyethylene pipes.
1. What types of pipes are there?
There are 5 main types of pipes:
Steel or galvanized (ferrous metal - an alloy of iron with carbon and other elements)
Copper (non-ferrous metal)
Metal-plastic
Polypropylene
Polyethylene (made of cross-linked polyethylene)
Each of the above types has its own purpose and is suitable for certain methods of laying pipelines and the properties of the transported medium (maximum and minimum temperature and pressure).
Today, heavy, unaesthetic metal pipes are being replaced by lightweight metal-plastic, polypropylene and polyethylene pipes. They come in different colors and do not need painting; they can be laid in any way - open, hidden or combined.
2. Purpose of cross-linked polyethylene pipes
XLPE pipes
Polyethylene pipes (PE) are used for:
- cold and hot water supply;
- low-temperature water heating (usually up to 80°-95C);
- water heated floors and walls;
- “cold panel” systems (an alternative to air conditioners that eliminates drafts and excess dust);
- cooling artificial ice skating rinks;
- soil heating in greenhouses;
- process pipelines for food and non-food liquids and gases, etc.
3. Advantages and disadvantages
Advantages:
low cost; a light weight; ease of installation; resistance to liquid freezing (if water freezes, the pipes will only stretch a little, and after thawing they will return to their previous size); absorption of noise and vibration during liquid transportation; reliability and long service life (up to 50 years or more) when used in low-temperature systems.Flaws:
low oxygen permeability of single-layer polyethylene pipes, which over a long period of time can lead to corrosion of system elements; reduced service life when used in high-temperature heating systems; instability to ultraviolet (solar) radiation when exposed for a long time.4. What are polyethylene pipes
Depending on the production technology, there are 3 main types of PE pipes:
- HDPE (polyethylene low pressure, its other common name is polyethylene high density);
- MSD (medium pressure and density polyethylene);
- LDPE (high pressure and low density polyethylene).
The following materials stand out:
- PEX (cross-linked polyethylene);
- PERT (heat resistant polyethylene).
HDPE, PSD and LDPE pipes are manufactured under different pressures, which influence the process of ethylene polymerization (combination of small gas molecules into larger macromolecules).
PEX and PERT are made from HDPE and PSD using the “cross-linking” and “adhesion” technology.
Cross-linked polyethylene is produced from high-density polyethylene by chemically or chemically cross-linking its molecules. physically with “flat” butene molecules.
During the production of heat-resistant PERT, medium-density polyethylene molecules bond with “bulk” octene.
Despite these differences, PEX and PERT materials have similar properties. Therefore, it is no coincidence that manufacturers lump them into one category (for example, you may see PEX and PERT pipes in the same section on plumbing company websites).
PEX and PERT pipes are:
- single-layer;
- multilayer.
In cross-section, multilayer pipes represent a three-layer or five-layer structure.
In a three-layer pipe, a layer of polyethylene is covered with glue, on top of which an anti-diffusion layer is applied, which prevents the penetration of oxygen and other gases into the water and thereby has an “anti-corrosion effect.” Polyvinylethylene EVOH or ethylene vinyl alcohol EVAL acts as an “oxygen barrier” that extends the service life of the system.
In a five-layer pipe, the anti-diffusion layer in the center is covered with layers of glue, on top of which layers of polyethylene are applied.
5. How to choose the pipe diameter
When choosing new pipes, pay attention to the size of the old ones. To replace it, you need to select a product of the same or slightly larger diameter.
For example, on your still existing metal pipes it is written “DN 15”: the number in this case means the internal diameter. And on modern polyethylene pipes, manufacturers indicate outside diameter and wall thickness.
To calculate the internal diameter, you need to subtract the wall thickness multiplied by two from the size of the external diameter. For example, the plastic says 20x2.0. 20 – 4 (2.0x2) = 16 mm. This means that a 20x2.0 polyethylene pipe with an internal diameter of 16 mm is suitable for replacing a DN 15 steel pipe.
Table 1. Calculation of the internal diameter of plastic pipes of the most common sizes
6. Which pipes are best to buy?
To choose quality products, pay attention to the type of material (indicated on the pipes themselves, the label or in the product description on the website).
There are two types of PERT material – Type I and II. Type 2 PERT can withstand 20% higher pressure than the previous generation, i.e. Type I.
When comparing PEX and PERT, PEX is considered more durable because it can withstand high temperatures and pressure longer.
Usually the letters a, b or c are added to the PEX inscription, which indicates the method of cross-linking polyethylene and affects their quality. PEXa and PEXb are manufactured chemically, PEXc – physical, while the degree of crosslinking of PEXa reaches 75%, PEXb – 65%, PEXc – 60%. Testing of the latest polyethylene pipes three types of the same size at 90°C showed the advantage of PEXb.
In addition, the quality of the pipe depends on the thickness of its wall and the method of applying oxygen-impermeable layers.
Tests have shown that a three-layer pipe is more reliable than a five-layer pipe. In a three-layer pipe, the polyethylene layer is monolithic over the entire cross-section of the pipe; in a five-layer pipe, it is interrupted by an anti-diffusion layer and glue, due to which the intermolecular bonds of polyethylene are interrupted. If it is overheated with a hair dryer during bending, delamination may occur. The hardness of the EVOH layer is significantly higher than that of PEX, so if properly transported, damage and abrasion of the outer layer is unlikely.
Table 2. Comparative characteristics of PEX pipes from various manufacturers
| Manufacturer | Valtec | Pro Aqua | Rehau | Birpex | Royal Thermo | Uponor | TEBO technics | Sanha |
| Polyethylene material | PEXb, PERT type II | PERT type II, PEXa | PEXa | PEXb, PERT | PEXb, PERT type II | PEXa | PERT type II | PEXc |
| Number of layers, pcs | 1-3 | 1-5 | 1-3 | no data | 5 | 1-3 | 1-5 | 5 |
| Outer diameter, mm | 16-20 | 16-40 | 10,1-63 | 16-63 | 16-20 | 16-110 | 16-26 | 16-20 |
| Wall thickness, mm | 2 | 2,2-5,5 | 1,1-8,6 | 1,8-8,6 | 2,2 | 2-15,1 | 2-3 | 2 |
| Working pressure, bar | 6-10 | 6-10 | 8-10 | 6-10 | 10 | 6-10 | 10 | 6 |
| Maximum working temperature, °C | 80-90 | 90 | 70-95 | 80-95 | 95 | 95 | 95 | 95 |
| Manufacturer country | Italy-Russia | Germany | Germany | Russia | Russia-Italy | Finland | Türkiye | Germany |
| Service life, years | 50 | 50 | 50 | 50 | 50 | 50 | 50 | 50 |
| Manufacturer's warranty, years | 10 | 10 | 1 | 5 | 8-10 | 10 | 7 | 1 |
| Delivery method | bays | bays | bays | bays | bays | bays | bays mi | bays |
| Price per 1 linear meter, rub. | from 33 | from 26 | from 96 | from 43 | From63 | from 52 | from 68 | from 28 |
*Prices according to online sources are valid for February 2018.
To assess the applicability of pipelines to specific system pay attention to the declared operating classes of products according to GOST (and certificates of compliance with them). They will show the share of the influence of changing temperatures in summer and winter on the actual service life. Example:
Table 3. Reliability requirements for polyethylene pipes according to GOST R 52134-2003
| Operating class | T slave, °C | Time at T pa b, year | T max, °C | Time at T max, year | T avar,°C | Time at T emergency, h | Application area |
| 1 | 60 | 49 | 80 | 1 | 95 | 100 | Hot water supply (60 °C) |
| 2 | 70 | 49 | 80 | 1 | 95 | 100 | Hot water supply (70 °C) |
| 3 | 30 | 20 | Low temperature underfloor heating |
||||
| 40 | 25 | 50 | 4,5 | 65 | 100 | ||
| 4 | 20 | 2,5 | High temperature underfloor heating Low temperature heating heating devices |
||||
| 40 | 20 | 70 | 2,5 | 100 | 100 | ||
| 60 | 25 | ||||||
| 5 | 20 | 14 | High temperature heating with heating devices | ||||
| 60 | 25 | 90 | 1 | 100 | 100 | ||
| 80 | 10 | ||||||
| HV | 20 | 50 | - | - | - | - | Cold water supply |
The following notations are used in the table:
T slave - operating temperature or combination of temperatures of transported water, determined by the area of application;
T max - maximum operating temperature, the effect of which is limited in time;
T avar - emergency temperature that occurs in emergency situations in case of violation of regulatory systems.7. Installation methods
There are three main ways to install wiring:
- Hidden;
- Open;
- Combined.
7.1. Hidden
With hidden installation, the pipeline and all connections are “hidden” in special recesses - grooves. Only fittings (connectors) and elbows for connection are visible from the outside plumbing fixtures. Upon completion of the work, the surface is sealed with finishing materials.
This method protects pipes from accidental damage and preserves the aesthetic appearance of the interior. However, this same installation option complicates the process (due to gating - laying channels), increases the cost of work and is not suitable for load-bearing walls.
Concealed installation also includes pipe coating concrete screed in "warm floor" systems.
7.2. Open
If the pipes cannot be hidden in the wall (for example, after a recent renovation), they can be laid on the surface. This option is convenient for visual control connections and allows you to quickly clean the area or replace a component if necessary. Additional arguments in favor of the method are the ease and low cost of work.
7.3. Combined
The combined method involves laying unfinished walls on the surface, which are then covered with plasterboard boxes or false panels made of plastic, tiles or other materials.
For installation, one of two connection systems is usually used:
- sequential
- collector
At sequential system the pipe is laid from one object to another. This system is suitable for bathrooms with a minimum number of objects (bathtub, sink, washing machine).
IN collector system all control devices are located in a compact manifold, which is placed in a special cabinet. Using a collector simplifies the work process and saves money. Suitable for radiator wiring and underfloor heating.
Tips for installing polyethylene pipes
Installation tips:
Before starting work, consider how the pipes will be placed. Then, directly on the walls, floor or ceiling, use a pencil or marker to draw the lines of the future pipeline. Use the pipe connection to the faucet, radiator or manifold as a starting point.
If necessary, before hidden gasket insulate fittings with film or entire pipes with a special corrugated casing. Do not use sharp objects to unpack the coil, as they may damage the material.
Try to minimize the number of fittings that affect pressure stability. For convenience, during the installation of “warm floors” you can use special slabs or mats that facilitate installation and minimize heat loss.
If you decide not to use thermal insulation mats, use anchor brackets and 90°C rotation clamps, as the “molecular memory” of polyethylene pipes will prevent it from maintaining the specified shape.
The same memory effect will help restore the original shape of the PEX pipe in case of excessive bending and deformation: it is enough to heat it with a hair dryer to 100–120 ° C (the temperature depends on the material, it is indicated in the product data sheet).
8. What materials and tools are needed
1. Materials:
- fittings (crimp, press-on, plastic) - special connectors for branching pipes, turns, transitions to another diameter (read more about fittings below),
- fasteners - clamps, brackets, brackets, rotation locks and other elements that secure polyethylene structures to supporting surfaces (most often on walls).
So, you have decided to lay a polyethylene pipeline yourself. In addition to the pipes themselves, you will need:
2. Tools:
- pipe cutter or scissors (different manufacturers call this tool differently);
- electrical or mechanical expander;
- wrenches for crimp fittings, vices (also called a press or tension tool) - for fittings with a sliding sleeve (or press-on fittings).
9. Types of fittings
You can independently install cross-linked polyethylene pipes using three main types of fittings:
- crimp (they are also called compression or collet);
- press-fit (or fittings with a sliding sleeve);
- plastic.
The range of all types of fittings includes connectors various forms– straight (couplings), angles, angles, water sockets, tees, crosses, which can be divided into two types:
Because the compression fittings require maintenance, they are perfect for open and combined installation. For installation in walls or warm floors they are no good.
Components of a compression fitting:
- body (fitting) with ring-shaped notches;
- split ferrule;
- screw.
How to proceed:
- Cut the pipe to the required length. scissors or pipe cutter.
- Place the nut on the section first (with the thread towards the connector), then the crimp ring. The edge of the ring should protrude approximately 1 mm above the cut.
- Insert the fitting into the pipe until it stops, tighten the ring and union nut to the edge of the cut.
The connection of pipes using a sliding sleeve is permanent, so such connectors can be used for any type of pipeline laying, even hidden.
Components for the sliding sleeve:
- frame;
- sleeve.
How to proceed:
- Cut the pipe to the required length using special scissors or a pipe cutter.
- Place the sleeve on a section away from the edge (it should not fall into the expansion area of the pipe).
- Insert the expander into the pipe and increase its diameter according to the instructions.
- Remove the expander and insert the fitting body into the pipe until it stops.
- Pull the sleeve onto the fitting using a vice.
Watch video instructions:
Watch video instructions:
10. What to do if you do not plan to install pipes yourself
In the online store Santekhmontazh.rf you can buy pipes made of cross-linked polyethylene from PEXb and PERT (type 2) of the Russian-Italian brand VALTEC and the German ProAqua. They are adapted to the conditions of domestic heat and water supply systems and have a 10-year manufacturer’s warranty. ProAqua products have undergone comprehensive testing and are certified in accordance with Russian standards. VALTEC sanitary ware received the “Brand of the Year” award in the Russian Federation and is widely in demand in the country (in the Moscow region alone, more than 1,200,000 sq. m of residential space are equipped with it every year).
In addition to polyethylene pipes, you can purchase from us fittings, fasteners and tools for their installation, heat-insulating boards, manifold cabinets, blocks, etc.
We will help you select all the necessary plumbing equipment to suit your needs, and we will also quickly and professionally install it, if after reading this article you still do not dare to change or lay the pipeline system yourself. Our installation division specializes in installing engineering systems in private and apartment buildings, in non-residential buildings for various purposes.
Pipe made of polyethylene with increased heat resistance PE-RT (type 2) is used in drinking and drinking water systems, hot water supply, low-temperature water (up to 80 ° C) heating, water heated floors and walls, soil heating, and also as process pipelines transporting liquids that are not aggressive to pipe materials. Operating classes according to GOST 32415-2013 - 1, 2, 4, ХВ.
The connection of VALTEC PE-RT pipes is carried out using press fittings (VTm.200, VTc.712), which are also used for connecting metal polymer pipes. For connections of the “cone” and “eurocone” standards, compression fittings VTc.4410, VTc.709 can be used. In progress installation work should follow the instructions given in technical passports to the specified fittings.
Estimated service life is 50 years. Delivery form: 200 m long sections in coils. The cost of the pipe is indicated for 1 linear meter.
VALTEC PE-RT pipe
Technical characteristics of Valtec polyethylene pipe:
Manufacturer: Valtec
Manufacturer country: Italy
Pipe material type: Polyethylene
Pipe application area: 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 permissible temperature: 90.0(deg.)
Guarantee period: 10 years)
Logistics: Supplied in 200 m coils.
Buy Valtec pe-rt pipe for heated floors in Moscow in company Teplodoma-msk
This is shown graphically in Figure 4. The layered crystalline structures are connected through amorphous polymer segments, i.e. cross chains. The likelihood of cross-chain formation increases with increasing polymer chain length.
Cross chain molecules are known to increase a material's stiffness and improve its flexural cracking resistance (ESCR) or long-term creep properties by "linking" multiple crystals together. The side chains exhibit stretchability and mobility and as such can absorb and dissipate energy.
Figure 4: Cross chain molecules increase the rigidity of the compound
Cross chain molecules increase ESCR and stiffness by "linking" multiple crystals
Cross chains are stretchable and mobile (can absorb/dissipate energy)
The type of co-monomer introduced also affects the concentration of cross-chains. As the chain length of the α-olefin co-monomer increases, the ability to form cross-chains also increases. Figure 5 shows that 1-octene is more efficient than 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 co-monomer concentration.
Figure 5 : The type of comonomer affects the likelihood of cross-chain molecules forming
When designing a molecular structure, it is important to control the concentration of the co-monomer and how it is incorporated into the polymer chain. Figure 6 shows curves depicting the relationship between molecular weight and the probability of cross-chain formation in ethylene-octene copolymers manufactured using Dow's patented solution polymerization technology. By controlling co-monomer incorporation, different polymer morphologies can be achieved, leading to different balances of properties.
By applying these ideas, a new family of DOWLEX brand polyethylene compounds was 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 the creation of a new class polyethylene materials for high temperature applications. These compounds are defined in the ISO-1043-1® standard as PE-RT or polyethylene with increased temperature resistance.
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 pipes hot water .
DOWLEX polyethylenes have been successfully used in the production of hot water pipes for over 20 years, and more than 1,000,000 km of pipes have already been installed.
For potable water supply 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, microbial growth inhibition, and disclosure of the material's composition to ensure that all additives used in the production of the material are included in the "positive list."
Thanks to good long-term hydrostatic strength at high temperatures, combined with excellent flexibility, DOWLEX 2344E and DOWLEX 2388 are the best solution for heating and water supply pipes.
DOWLEX PE compounds for pipes: worldwide certification
- Certified as non-crosslinked materials 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, the Netherlands, France, Russia, Great Britain, USA.
Pipes made from DOWLEX 2344E exhibit excellent long-term hydrostatic strength at elevated temperatures without the need for crosslinking. This makes the product particularly suitable for the production of hot water pipes. Approvals for this material have been granted in a number of countries, for example DOWLEX 2344E complies with the German standard DIN 16833(6) (PE-RT) and the corresponding application standard DIN 4721.: In the Netherlands KIWA(8) approval has been issued for all hot water pipes; and in the USA this material is listed as PPI(9) at 180°F (approx. 82°C). DOWLEX 2344E DOWLEX 2388 is the only non-crosslinkable polyethylene in this class. Multilayer metal-plastic pipes comply with the requirements of ASTM1282-01A00 standard.
Pipes made from DOWLEX 2344E are extremely flexible, making them easy to install. Standard PE welding technologies can be used without the need for crosslinking. In addition, the absence of cross-linking allows high production speeds to be achieved. This advantage is important for the production of multilayer composite pipes. The high smoothness of DOWLEX pipes reduces losses at the extruder head and leads to minimal carbon deposits.
The newest member of the DOWLEX series of polyethylene pipe compounds is DOWLEX 2388, an ethylene-octene copolymer manufactured using Dow's patented solution polymerization technology. This product designed to combine excellent long-term hydrostatic strength with excellent machinability.
Advantages of PE-RT for pipe production
- Line speed > 60 m/min. without technological additives
- No loss of raw materials when starting up equipment, since the material can be recycled
- Saving time + production costs:
- Not required additional stage vulcanization
- No laboratory analysis required to determine the degree of crosslinking
- Good taste and smell characteristics
- Excellent weldability
Figure 7. Hoop Voltage Characteristics of DOWLEX 2388 SEM to ISO 9080
As can be seen in Figure 7, the regression curves of DOWLEX 2388 are very flat, resulting in high design stresses over long periods of time, especially at elevated temperatures. At a temperature of 110 °C, the destruction time, significantly exceeding one year, allows us to predict the service life of pipes at 70 °C over 50 years, at 60 °C about 100 years (using extrapolation indicators according to the ISO 9080 standard). The resulting design stress is not only comparable to cross-linked PEX, but superior.
In recent years, the underfloor water heating system has become a leader compared to radiator and other heating in private and suburban construction. Many water heated floors began to be used as the main and only heating in private country house. Not only customers, but also people who independently install such a system think about the quality of pipes and the materials from which they are made.
Which pipes are best to choose for water heated floors - review of materials and manufacturers
Basic information about pipes for both underfloor heating and other systems (heating and water supply) that you need to know - this is the pipe manufacturer and country of production. Since it doesn’t matter what material the pipe is made from, if it is not produced using technology, with savings on the quality of raw materials and quality control, such a pipe will not last long. And as with other products, a good pipe for heated floors cannot be cheap.
Basic properties and parameters of pipes used in floor and panel heating
When choosing a pipe for installation in a heated floor of a private country house or an apartment in a high-rise building, are based not only on the quality of the pipe and its possibility of application in a particular case, but also on the ease of installation. For a person who will be installing a heated floor in his home for the first time, it will be more convenient and pleasant to work with a pipe that is more flexible and holds its shape than a rigid and inflexible one, and this also needs to be taken into account, because In the future, this may affect the quality (uniformity) of the underfloor heating.
Which material is more suitable for underfloor heating pipes?
Metal-plastic pipes
Metal-plastic pipes are the first and most popular, until recently, polymer pipes for heated floors. If you look in section, such a pipe consists of two polymer layers, between which there is a layer of aluminum foil 0.2 millimeters thick or more. The most famous pipe for underfloor heating is the Henco pipe. Lately is not very popular, because... the cost of the pipe is quite high. Through the use of cross-linked PEX polyethylene and high-quality adhesive for gluing the layers.
Unlike Henco, other European manufacturers have switched to the production of metal-plastic pipes made of heat-resistant polyethylene PE-RT. The elongation of this material when heated is several times less than that of PEX cross-linked polyethylene; therefore, the reliability of such a pipe during sudden temperature fluctuations is higher. So, many Chinese manufacturers use cross-linked polyethylene, and taking into account the savings on other materials, the overall quality of the pipe turns out to be quite low, which is why there are a lot of bad reviews about delaminating pipes, cracking outer layer (affected by ultraviolet radiation).
The presence of aluminum foil in the composition of a metal-plastic pipe allows you to completely avoid the ingress of oxygen into the coolant and reduce the linear elongation by up to 5 times.
If you decide to use a metal-plastic pipe, it is better to focus on European manufacturers
- Uponor (PE-RT/AL/PE-RT) Germany
- Germany
- HENCO (PEXc/AL0.4vmm/PEXc) Belgium
- APE, STOUT (PEXb/Al/PEXb) Italy
- COMPIPE (PEXb/Al/PEXb) Russia(Use up to operating class 5)
- Valtec, Altstream, etc. Russia-China
XLPE pipes
Cross-linked polyethylene is the most popular material for underfloor heating pipes at present. We will not dwell on the description of this material, because... There’s enough information to fill an entire article, but we’ll tell you which pipe options are best to choose.
The highest percentage of crosslinking (from 75%) in the peroxide crosslinking method is PEXa pipes. The most expensive method used by European manufacturers. The silane crosslinking method of PEXb is the most common, the level of crosslinking is quite high, but for example in the USA such pipes are prohibited for use due to the presence of harmful chemical compounds. It is also believed that a PEXb pipe gains its strength properties only during operation of the pipe with coolant.
By exposing the material to charged particles, 60% cross-linked PEXc polyethylene is obtained. The product is irradiated in the solid state. The main disadvantages of the method are the heterogeneity of the material as a result, but there are also advantages - cross-linked polyethylene gains increased elasticity.
As the degree of crosslinking increases, strength, heat resistance, resistance to aggressive environments and ultraviolet rays. However, along with an increase in the degree of cross-linking, the fragility of the resulting pipeline increases and the flexibility decreases. If you increase the degree of crosslinking of polyethylene to 100%, then its properties will be similar to glass.
The biggest problem in choosing a specific manufacturer and pipe is the low quality of stitching in pipes made in China, as well as some representatives of the Russian. Another disadvantage of such pipes is the rigidity of the pipe; it does not hold its shape well and after bending it tries to take its previous shape and therefore it is more difficult to work with it than with a metal-plastic pipe, especially for an inexperienced installer.
The disadvantage of PEX material is that it is oxygen permeable. Water in pipelines without oxygen protection becomes saturated with oxygen after a certain time, which can lead to corrosion of system elements. PEX is used to reduce oxygen permeability thin layer made of polyvinylethylene (EVOH). Basic PEX layer and the EVOH layer are connected to each other with glue. It is worth noting that the EVOH layer does not completely prevent oxygen emission, but only reduces oxygen permeability to 0.05–0.1 g/m3 day, which is acceptable for heating systems. In a PEX-EVOH pipe, the anti-diffusion layer is made on the outside, i.e. The pipe has a three-layer construction: PEX-adhesive-EVOH. Five-layer (PEX-adhesive-EVOH-adhesive-PEX) pipes are also available on the market, but tests have shown that the three-layer design is more reliable. The belief that the outer layer of EVOH in a three-layer construction is susceptible to abrasion is erroneous.
Another disadvantage of PEX pipes is their large linear elongation, so such pipes are practically not used for external installation, but only for hidden ones.
One of the advantages of pipelines made of cross-linked polyethylene is the presence of a memory effect. The shape memory effect is very useful during installation. If a kink, compression or other deformation occurs during pipeline installation, it can be easily eliminated by heating the pipeline to a temperature of 100–120 °C. (However, in the passport for the Russian-Chinese Valtec pipe it is written: “If there is a “kink”, the damaged section of the pipe must be removed.”)
Wrinkles form on pipelines coated with an anti-diffusion layer after restoration. In these areas, the anti-diffusion layer peels away from the PEX layer. This defect practically does not affect the characteristics of the pipeline, since the main bearing capacity The pipeline is identified by a layer of PEX that has been completely restored. A slight peeling of the anti-diffusion layer does not significantly increase the oxygen permeability of the pipeline.
Pipelines made of cross-linked polyethylene, and especially PEXa produced in Europe, are better suited than other polymer pipes for use not only in underfloor heating, but also in radiator heating, using the hidden method.
What pipes can be found on sale:
- Germany
- UPONOR COMFORT PIPE PLUS PE-Xa EVOH Germany(use up to class 5, heated floors and radiators)
- SANEXT "Warm floor" PE-Xa Russia-Europe(use up to operating class 4)
- Russia-China(use up to operating class 4)
(use up to operating class 5) BEST CHOICE for PRICE-QUALITY
Heat-resistant polyethylene PE-RT
Very often, heat-resistant polyethylene PE-RT is called cross-linked polyethylene. But the production technology of such polyethylene is as follows. In the chemical reaction, “flat” butene is replaced by octylene (formula C8P16), which has a spatially branched structure. Subsequently, it forms side branches near the main chain, which are mutually intertwined monomer chains. They are connected to each other due to the mechanical interlacing of branches, and not due to interatomic bonds.
PE-RT pipes are mainly used for underfloor heating, where the temperature and pressure are lower than in water supply and heating systems. Although the manufacturers of PE-RT pipes, when pursuing their marketing policy, claim that the properties of their pipes are the same as those made from PEX cross-linked polyethylene. However, this is questionable since PE-RT is a conventional thermoplastic with limited overall resistance to elevated temperatures and pressures in systems with hot water, which is confirmed by hydraulic tests and subsequent practice.
A comparison of regression curves obtained by the independent Bodycoat Polymer Institute (Belgium) suggests that the durability of PE-X pipes is higher, and the regression curve, showing the loss of ability to perform work functions over time, for heat-resistant polyethylene PE-RT has a characteristic break (loss of strength during long-term operation) already at 70 °C.
BioPipe (PERT) Russia
Most affordable option with high quality
Stainless steel and copper pipes
These types of pipes are practically not used in the installation of heated floors, and the main reason is the high price. Due to polyethylene pipelines the best German manufacturers 2 times cheaper than metal pipes, and the service life is more than 50 years (in a warm floor), there is no need for such pipes. Floor installation from copper pipe more expensive and the installer of such floors must have extensive experience and qualifications.
conclusions
As with other types of equipment and materials, when choosing a specific manufacturer, we recommend choosing European manufacturers. The fact that the manufacturer is European must be determined by the barcode and the inscription “Made in...”. Many sellers offer an Italian pipe, but cannot confirm that it was made in Italy, because... The pipe is actually produced in China, and the real homeland of the brand is Russia. And of course, if the pipe is produced in Europe, then the price for such a pipe will not be the lowest, because... quality cannot be cheap. If you compare an inexpensive German pipe and an expensive Chinese one, decide for yourself how confident you are in the real characteristics and quality of the Chinese pipe, for example, in the level of cross-linking of cross-linked polyethylene.
If we draw conclusions about the materials for underfloor heating pipes, then our experts arrange the materials in the following order, starting with the best:
- Cross-linked PEXa polyethylene with anti-diffusion layer
- Metal-plastic with an inner layer of PE-RT
- Cross-linked polyethylene PEXb,c
- Heat-resistant polyethylene PE-RT
Pipe Thermotech Thermosystem®(old name Thermotech >MIDI< Composite) является модернизированным вариантом труб PE-RT, полностью изготовленной из материала Dowlex 2344 (тип 1) и 2388 (тип 2) (PE-RT, trademark Dowlex is owned by DOW Chemical Corp.) with a large number bonds between molecules, with an oxygen barrier (EVOH) hidden inside the pipe between layers of polyethylene. Because All layers are polymers, then as a result of sequential connection of layers, a pipe is formed as a single whole, stable under conditions of temperature and pressure fluctuations, with a small linear elongation, resistant to mechanical stress.
Let's decipher the abbreviation PE-RT - PolyEthylene of Raised Temperature resistance - polyethylene of increased temperature resistance - the secret lies in large quantities carbon bonds in molecules. The side chains of the linear Standard Polyethylene (PE) molecule are formed by a combination of butene molecules. Two carbon atoms are used to connect the main chains to each other, so the probability of intertwining is low. The side chains of the linear PE-RT polyethylene molecule increase the number of connecting Carbon atoms to 6, while the degree of intertwining is much higher. If the source material for PEX - Polyethylene, with the same monomer content, is not “cross-linked”, then it will provide much less strength under prolonged exposure to pressure.
Warm floor pipe Thermotech Thermosystem®– has an anti-diffusion layer OXYDEX (EVOH polyethylene), which prevents the penetration of oxygen and an anti-creaking layer, which form a single whole with the pipe.
Anti-diffusion layer OXYDEХ: During the production of pipes, a thin layer of modified polyethylene, 0.1 mm thick, is applied to the surface of the “main” PE-RT pipe. This is followed by the same layer of EVOH (ethyl vinyl hydroxide) plastic. Previously, this anti-diffusion layer was applied on the outside of the pipe. Over time, some manufacturers and Thermotech pipes, incl. They began to apply another protective layer of polyethylene on it.
New polymer pipes from Thermotech - ThermoSystem pipes made of PE-RT type II polyethylene - are more flexible and more reliable compared to the old ThermoSystem pipes (12, 17 and 20 mm) due to the placement of an anti-diffusion layer on the inner surface of the pipe with a protective layer polyethylene. The oxygen barrier is protected from mechanical damage by the entire thickness of the pipe wall
The EVOH layer acts as a diffusion barrier for oxygen, and the polyethylene layer increases the adhesion between the pipe and the diffusion barrier. The barrier is tightly glued to the pipe, making bends of small radii possible without the formation of folds. Oxygen-tightness of pipes Thermotech complies with the DIN 4726 standard (Deutsches Institut fur Normung), and is less than 0.1 g/m2. for 24 hours at 40 °C. OXYDEX layer in pipes Thermotech reliably protected from mechanical damage protective layer polyethylene. The melting point of the anti-diffusion layer is 180° C. These properties allow the use of such pipes at operating temperatures of the carrier up to 95°, and in short-term modes – up to 110° C, that is, mainly in hot water supply and heating systems, heated floors.
Oxygen penetrating the system does not cause any harm to the pipes themselves, it only reacts with the metal parts of the system, causing accelerated corrosion of heating boilers, pumps, radiators, shut-off and control valves and other metal equipment. This process is especially accelerated when using pipes in systems with elevated temperature, i.e. in heating systems (especially radiator systems). Unfortunately, SNiP does not have an acceptable value for oxygen penetration in systems made of plastic pipes. Therefore, in reality, pipes without a diffusion layer are often used, which after 5 years leads to the failure of the steel elements of the system. To prevent this from happening, it is necessary to use only pipes in heating systems that meet the requirements of the German standard DIN 4726. It should be noted that today only a few companies can offer pipes that meet the requirements of this standard.
This pipe can withstand high pressure. The lifespan of PERT pipes is determined by nomograms depending on the temperature and pressure of the working medium (as well as all other polymer pipes). According to Russian certification, PE-RT pipes are classified as type “t” (heavy), i.e. withstanding pressure of 20 kgf/cm2.
The THERMOTECH brand produces 5-layer unreinforced pipes for heating and water supply systems:
- Thermotech Thermosystem PE-RT I diameters 8x1, 12x2 mm, 17x2 mm, 26x3 mm
- Thermotech MultiPipe PE-RT II diameters 16x2, 26x3,
- Thermotech Thermosystem PE-RT II diameter 20x2, 32x3 mm
Advantages of Thermotech pipe
Thermotech = reliable + easy to install + inexpensive!
Extreme flexibility and strength without the use of a crosslinker. The secret lies in the large number of carbon bonds in the molecules. To understand the difference, answer the question: what kind of shoes do you prefer to buy - with edging sewn to the sole (analogous to molecular cross-linking of polyethylene) or with a glued sole (analogous to chemical cross-linking of polyethylene or glued plastics)?
The service life of the pipe is over 50 years. It requires virtually no maintenance during operation, which further facilitates the work of public utilities.
Able to withstand high pressures and temperatures. The service life of PERT pipes is determined by nomograms (see appendix) depending on the temperature and pressure of the working medium. According to Russian certification, PE-RT pipes are classified as type “t” (heavy), i.e. withstand pressure 20 kgf/cm2
Polyethylene pipes are 5–7 times lighter than steel pipes. Pipes are produced seamlessly in standard coils 12 * 2.0 mm (1000 m), 16 * 2.0 mm (750 m), 20 * 2.0 mm (650 m), 25 * 2.3 mm (350 m), 32 *3.0 mm (50 m). This significantly reduces transportation costs and makes the work of installers easier.
The temperature linear expansion of PE-RT pipes is several times less than that of standard PEX pipes. When the temperature changes by 50°C, the linear elongation of PE-RT pipes is only 0.3%, and when the temperature changes by 90°C – 0.7%. When cooled, the pipe completely returns to its original shape.
Joining polyethylene pipes is much cheaper, simpler and takes less time. The pipes are connected using brass compression fittings and takes seconds. The entire installer's tool consists of pruning shears and a wrench. Therefore, even a non-specialist can change or install the plumbing himself.
No squeaking in underfloor water heating systems.
Due to the low surface roughness (0.125 microns), the pipes are not subject to overgrowing, therefore require virtually no maintenance during operation and are silent at almost any flow rate.
Frost-resistant and able to withstand several freeze-thaw cycles (for example, water).
It has high maintainability. Multiple joining and undocking of the fitting is allowed, while the pipe at the joint retains its properties.
Can be used for transportation food products, aggressive liquids and gases.
Fully meet the requirements of modern industry for the aesthetics of work and operation of pipelines.
Warranty periods: shelf life 3 years, service life 7 years.
The pipe is resistant to chemicals and mechanical wear.
Foreign certification.
The pipe was tested at SKZ (Suddeutsches Kunststoff Zentrum). According to SKZ tests, the service life of PERT pipe is 490 years with a safety factor of 2.5.
According to the TUV (Technisher Uberwaschungs – veren Bayern) conclusion, a pipe with an OXYDEX layer is not subject to oxygen diffusion (does not allow air to pass through).
The production has an international quality certificate ISO 9002.
Russian certification.
GOSSTROY OF RUSSIA No. 0130837*. Application in heating systems.
HYGIENE CERTIFICATES. According to test results at Polymertest LLC, the service life of the MIDI pipe is more than 100 years, depending on operating conditions.
ROSTSTANDARD. Application in DHW systems, HVS.
Certified for heating systems with operating coolant temperatures up to 95°, at peaks up to 110° C (no worse than any other polymer pipes), pressure up to 20 kgf/cm2 (!).
Pipes Thermotech Thermosystem® are manufactured in Germany by the HPG concern to order from Thermotech (Sweden).
DEVELOPER and MANUFACTURER of PE-RT compound Dowlex 2344 - "The Dow Chemical Company"
Materials and articles from "The Dow Chemical Company" in attachments:
- PE-RT, new class polyethylene for hot water pipes
- PE-RT, a new class of polyethylenes for industrial pipes
How do pipes for heated floors behave when negative temperatures?We do not object to the use of pipes in low temperature environments. Moreover, well-known facilities with PE-RT pipes have been operated without problems for years in arenas with artificial ice in Europe.
PERT pipes maintain high strength even at temperatures down to -40°C.
The DOWLEX 2344E material, compared to other polymers, has a higher thermal conductivity at negative temperatures (2-3 times higher), which means the power of refrigeration units can be reduced.
In Thermotech pipes inner surface- mirror-like, they have a very low roughness (0.125 microns, class 10), this is less than that of PEX pipes and significantly less than that of any metal-plastic pipes. The point is that in metal plastic pipes The main load is borne by the aluminum layer and therefore the polymer layers in such pipes worse quality than in plastic pipes. Reducing hydraulic losses in Thermotech pipes will reduce the power of circulation pumps.
*****************
A lot of objects have been made. For a very long time there were no competitive offers at all! No complaints.
Differences between pipes >>>
