Appearance on the market polymer pipes became a happy deliverance from the eternal leak. At first, many were skeptical about the new product, but soon the ranks of skeptics thinned significantly.
At the moment, few people who are planning to lay communication networks for private properties are interested in steel pipes, since in fact polymers have turned out to be disproportionately more practical to use and easy to install. But now the already extremely popular polypropylene pipes have been replaced by polyethylene heating pipes - one of the relatively recent innovations in thermal communications.
And again, healthy skepticism is heard in the discussion of the new product. After all, humanity has been familiar with polyethylene for more than a century, during which it has become truly indispensable. But everyone knows that this material is not suitable for use in heating systems. Although under normal circumstances polyethylene melts at temperatures from 80°C, the pressure in the pipe reduces this figure to 40°C, which is completely unacceptable for heating networks. However, new skeptics should take into account that over the past century many new discoveries have been made in the polymer industry, so pipe polyethylene has significantly superior characteristics to its household counterparts.
A wide range of.
Polyethylene for heating systems
The maximum operating temperature for polypropylene heating network components is 95°C required by relevant standards. It is clear that it would be difficult for ordinary polyethylene to compete in this indicator with reinforced polypropylene. However, this is not required, since polyethylene is used in heating systems new material a completely different modification, known as stitched. It sounds frivolous, bringing to mind thoughts of making innovative heating pipes in a sewing workshop. In fact, the everyday term refers to a complex technological process.
ABOUT polyethylene production A chemistry course gives every student a general idea. The popular polymer is formed by monomolecular chains that stretch to the required length. Modern technologies make it possible to achieve the formation of cross-links between molecules in addition to longitudinal ones. This happens with the participation of a catalyst due to bombardment with electron beams, heating or immersion in a liquid. As a result, there is polymer material with fundamentally different properties, used in the production of polyethylene pipes for heating and known in the original as PE-X, and in Russia called PE-S.
The result of the development so far has been a material that is resistant to aggressive influences, retaining its properties over a wide temperature range, with the following characteristics:
- high plasticity;
- mechanical and chemical resistance;
- low oxygen permeability;
- stability at temperatures from 110°С below zero to 110°С above zero;
- operating temperature maximum 95°C above zero;
- softening temperature 132°C above zero;
- operating pressure 90°C/7 bar or 70°C/11 bar.
The smooth polyethylene surface on the inside helps to maintain the cross-section unchanged throughout the entire service life, which for use in heating systems is 50 years. To avoid the development of corrosion processes on the metal components of the heating network, polyethylene pipes are produced with a protective layer that ensures a minimum of oxygen ingress. For heating networks, products are made from two layers of cross-linked polyethylene, separated by an aluminum layer that reduces thermal elongation to eliminate deformation.
Application of polyethylene pipes
In fact, polymer crosslinking technology has been widely used for three decades, but polyethylene pipes for heating began to be used only in heated floors. Produced in two-hundred-meter coils flexible tubes extremely convenient to install, since the significant length allows you to avoid unnecessary joints, which are considered weak point any communications. To seal connections, standardized fittings are made of plastic and brass, ensuring simple installation. The use of long polyethylene pipes makes it possible to extend connections above the floor level for easier access if necessary.
When installing heated floors, it is advisable to use products with an anti-diffusion coating that prevents the access of oxygen. It is inappropriate to use more expensive multilayer polyethylene pipes in this situation, since the temperature of the coolant is relatively low and the deformation is insignificant. But in heating networks operating at a higher temperature temperature conditions, you can’t do without multilayer products with a low elongation coefficient. Heating systems only open type suggest the use of polyethylene pipes that lack an anti-diffusion barrier, since oxygen penetrates inside in any case.
Installation features
The obvious advantages of polyethylene products include elasticity, which allows them to be bent at almost any angle. Cold cross-linked polyethylene retains its bend only when secured special devices, but the heated material is easily fixed in the desired position. The pipe should be heated carefully to avoid reducing its anti-diffusion properties. After fixing the required bend, it must be cooled before use. A heating system with polyethylene wiring is installed without the use of corner connecting parts, therefore it turns out to be significantly more reliable by reducing the risk of depressurization.
The memory effect is another advantage of polyethylene heating pipes. They are not afraid of bending, since the flow of hot air can quickly restore its original shape. The molecular memory of cross-linked polyethylene is also used to connect to fittings using an extender, which stretches the hole to fit onto the fitting, to which the pipe fits tightly, returning to its natural diameter. Welding when installing heating networks made of polyethylene pipes is used quite rarely, although in terms of the tightness of the heating system it is more preferable, since it provides molecular bonds in the joints.
However, when carrying out installation work, you will have to take into account the disadvantages of polyethylene products. One of them is the notorious temperature deformation, which can not be considered a disadvantage when pipes are placed openly, when elongation from heating, only partially compensated by bends, does not encounter obstacles during displacement. But the polyethylene pipeline, sewn into concrete screed, turns out to be deprived of the possibility of displacement unless placed in a protective casing of a larger diameter. An alternative to the casing can be the use of pipes with an aluminum layer for a heating system placed under concrete. Otherwise, emergency situations are likely.
But multilayer products are quite expensive, as are polyethylene heating pipes in general, including components for their installation, in comparison with other polymer analogues. This is definitely a minus. However, based on the parameters declared by the manufacturers and user reviews, it is worth recognizing that high price in this case, it fully corresponds to the class of products. Judging by the test results, a well-installed heating network with polyethylene wiring can really last for half a century, making endless leaks and associated heating interruptions a thing of the past.
Plastic heating pipes, the characteristics of which will be discussed in the publication, have firmly occupied their niche in the building materials market more than 20 years ago, and have managed to gain wide popularity. There are many varieties of them, differing in the material of manufacture and, accordingly, in their areas of application.
Some plastic pipes are primarily designed to organize the circulation of coolant from the boiler through heat exchange devices. Others, due to their flexibility and plasticity, are ideal for laying the contours of water-heated floors. And some varieties can be safely classified as universal - they are suitable for installing almost any component of the heating system.
Before considering the different types of plastic pipes and understanding, it is necessary to clearly define what requirements they must meet if they are planned to be installed in a heating system.
Criteria for choosing pipes for heating systems
Pipes for installation in a heating system must meet certain requirements, as they experience special loads associated primarily with temperature changes. In order for the heating system to be reliable and operate for a long time without the risk of accidents, it would be unwise to choose a pipe based only on ease of installation and low price.
Today, the range of pipe products on sale is quite large. They differ in dimensional parameters - diameter and wall thickness, type and quality of manufacturing material, linear expansion, flexibility, presence or absence of reinforcement, resistance to pressure and temperature loads, ultraviolet radiation, etc. But if heating pipes are selected, they must meet the following characteristics:
- The pipes must withstand the high temperatures of the coolant passing through them. According to the standards in the system central heating the coolant temperature should not exceed 70÷75 degrees, but pipes must be purchased with an operational “reserve”, that is, with characteristics calculated at least 90÷95 degrees. They must maintain their density in unforeseen extreme situations, and the plastic must not somehow react abnormally to increased heat, so as not to cause deformation of the laid contours.
- At elevated temperatures in the heating system, the pressure always increases. This means that the pipes must be guaranteed to withstand pressure loads and water hammer. This quality is especially important for pipes installed in circuits connected to a central heating system, where it is much more difficult for the home owner to control the relevant parameters.
- Heating pipes must have a perfectly smooth inner surface, which will help to avoid significant deposits of scale and dirt from low-quality coolant, which can create excessive resistance to normal fluid circulation.
- The manufacturing material must have a minimum coefficient thermal expansion, otherwise, when exposed to high temperatures, the pipes will begin to sag or increased internal wall stress will be created in them, at which they will begin to bend.
- Polymer pipes are not exposed to aggressive environments and the occurrence of corrosive processes - this quality is ideally suited for their use in a heating system.
- Pipes must be designed for a long service life, which cannot be lower than that of other elements of the heating system.
- The coolant must circulate silently within the system, since not all homeowners enjoy the sound of rushing water. Unlike metal options polymer pipes are able to ensure movement without turbulence and sound resonance.
- An important quality for maintaining harmony in the interior is a neat appearance heating pipes.
Modern technologies for manufacturing composite materials and plastics make it possible to produce pipes that almost completely meet the criteria listed above. The most popular and often used for arranging heating system circuits are polypropylene and polyethylene pipes, manufactured in various combinations, including those with aluminum reinforcement, which are called metal-plastic.
You may be interested in information about what characteristics are guaranteed
Since the quality of heating and hot water supply system pipes depends on all materials of manufacture, various options should be considered.
Polypropylene pipes for heating system
Polypropylene (PP) has been used for quite a long time as a raw material for the manufacture of pipes, but only modern modifications of this material have made it possible to use it for products operating under conditions of high temperatures and pressure.
High-quality polypropylene pipes are ideal for heating systems, with the exception of “warm floor” circuits
Polypropylene pipes are quite resistant to various chemical compounds, but in terms of strength and heat resistance, these products differ significantly from each other. Polypropylene is divided into three types, which have their own designations:
- The first type (PP-N) has high strength and inertness to chemical influences, but is not able to withstand high temperatures. Therefore, they are used for cold water supply, drainage and ventilation systems, as well as for other needs where the material is not expected to come into contact with heated liquids.
- The second type (PP-B or PP-2) – saves everything positive traits the first type of material, but is able to withstand minimal thermal loads. For example, this material will not withstand temperatures of 85–90 degrees even for a short time. Pipes with this marking can, with a certain convention, be used in hot water supply systems or in “warm floor” systems, where the heating of the coolant does not exceed a temperature of 50 degrees.
- The third type (PPRC, PRR or PP-3) - intended for use in heating and supply systems hot water, since such polypropylene is resistant to thermal and compression loads. This material is made using technology where, during the synthesis process, ethylene molecules are built into the molecular chain of propylene, which makes products made from it more resistant and durable.
It is polypropylene PP-3 that is mainly used for the production of pipes that have various areas applications.
Pipes may vary in color scheme, but this fact, contrary to a fairly popular belief, does not in any way indicate their characteristics or special qualities, so you can choose any one that is more suitable for the design of the room.
Many manufacturers place red or blue stripes on the surface of the pipes. It’s not difficult to figure it out, since the red color clearly indicates the heat resistance of the material used to make the pipes, and the blue stripe indicates the possibility of installing them only in a cold water supply system.
However, such designations are not present on all products, so it is recommended, first of all, to pay attention to the letter markings.
The third type of pipes - PPR, in turn is divided according to several parameters. This is, first of all, the wall thickness and diameter of the products. For heating at home, standard diameters are used: 16, 20, 25, 32, 40, 50 millimeters. In addition, the designation indicates the operating pressure for which the pipe is designed. There are four of these types in terms of operating pressure: PN -10; PN -16; PN -20; PN -25.
| Type polypropylene pipes | Nominal working pressure | Scope of pipe use | |
|---|---|---|---|
| MPa | technical atmospheres (kgf/s²) | ||
| PN-10 | 1 | 10.197 | Cold water supply or heating systems with heating fluid not exceeding 45˚С |
| PN-16 | 1.6 | 16.32 | Cold and hot water supply with a temperature of no more than 60˚С. |
| PN-20 | 2 | 20.394 | Cold and hot water supply or autonomous heating systems with low level coolant pressure and guaranteed absence of water hammer |
| PN-25 | 2.5 | 25.49 | Hot water supply and heating with coolant up to 90÷95˚С, including for the central heating system. |
The specified data was obtained as a result of long-term laboratory and operational tests of all types of pipes. The material should be selected taking into account the recommended parameters, without trying to achieve some kind of “penny” savings.
The table below provides information on the standard linear parameters of polypropylene pipes various types. In this case, “Ø int” will indicate inner diameter pipe channel, and “h” is the wall thickness.
| Pipe type | PN-10 | PN-16 | PN-20 | PN-25 | ||||
|---|---|---|---|---|---|---|---|---|
| Outer diameter of PP pipe, mm | Ø int (mm) | h (mm) | Ø int (mm) | h (mm) | Ø int (mm) | h (mm) | Ø int (mm) | h (mm) |
| 16 | - | - | 11.6 | 2.2 | 10.6 | 2.7 | - | - |
| 20 | 16.2 | 1.9 | 14.4 | 2.8 | 13.2 | 3.4 | 13.2 | 3.4 |
| 25 | 20.4 | 2.3 | 18 | 3.5 | 16.6 | 4.2 | 16.6 | 4.2 |
| 32 | 26 | 3 | 23 | 4.4 | 21.2 | 5.4 | 21.2 | 3 |
| 40 | 32.6 | 3.7 | 28.8 | 5.5 | 26.6 | 6.7 | 26.6 | 3.7 |
| 50 | 40.8 | 4.6 | 36.2 | 6.9 | 33.2 | 8.4 | 33.2 | 4.6 |
| 63 | 51.4 | 5.8 | 45.6 | 8.4 | 42 | 10.5 | 42 | 5.8 |
| 75 | 61.2 | 6.9 | 54.2 | 10.3 | 50 | 12.5 | 50 | 6.9 |
| 90 | 73.6 | 8.2 | 65 | 12.3 | 60 | 15 | - | - |
| 110 | 90 | 10 | 79.6 | 15.1 | 73.2 | 18.4 | - | - |
And the following table will clearly show how long the service life of pipes can be expected, depending on their type and operating conditions - temperature and pressure of the coolant.
| Coolant temperature ˚С | Service life, years | Pipe type | |||
|---|---|---|---|---|---|
| PN-10 | PN-16 | PN-20 | PN-25 | ||
| permissible pressure (kgf/cm²) | |||||
| 20 | 10 | 13.5 | 21.7 | 21.7 | 33.9 |
| 25 | 13.2 | 21.1 | 26.4 | 33 | |
| 50 | 12.9 | 20.7 | 25.9 | 32.3 | |
| 30 | 10 | 11.7 | 18.8 | 23.5 | 9.3 |
| 25 | 11.3 | 18.1 | 22.7 | 28.3 | |
| 50 | 11.1 | 17.7 | 22.1 | 27.7 | |
| 40 | 10 | 10.1 | 16.2 | 20.3 | 25.3 |
| 25 | 9.7 | 15.6 | 19.5 | 24.3 | |
| 50 | 9.2 | 14.7 | 18.4 | 23 | |
| 50 | 10 | 13.9 | 17.3 | 23.5 | 21.7 |
| 25 | 8 | 12.8 | 16 | 20 | |
| 50 | 7.3 | 11.7 | 14.7 | 18.3 | |
| 60 | 10 | 7.2 | 11.5 | 14.4 | 18 |
| 25 | 6.1 | 9.8 | 12.3 | 15.3 | |
| 50 | 5.5 | 8.7 | 10.9 | 13.7 | |
| 70 | 10 | 5.3 | 8.5 | 10.7 | 13.3 |
| 25 | 4.5 | 7.3 | 9.1 | 11.9 | |
| 30 | 4.4 | 7 | 8.8 | 11 | |
| 50 | 4.3 | 6.8 | 8.5 | 10.7 | |
| 80 | 5 | 4.3 | 6.9 | 8.7 | 10.8 |
| 10 | 3.9 | 6.3 | 7.9 | 9.8 | |
| 25 | 3.7 | 5.9 | 7.5 | 9.2 | |
| 95 | 1 | 3.9 | 6.7 | 7.6 | 8.5 |
| 5 | 2.8 | 4.4 | 5.4 | 6.1 | |
As you can see from the presented characteristics, PN-20 pipes are acceptable for heating and hot water supply systems, taking into account temperature characteristics, but it is best to install PN-25, which are ideal for any heating system.
"Pros" and "cons" of polypropylene pipes
Installation of polypropylene pipes in the heating circuit has a large number of advantages:
- The lightness of the material will allow you to deliver the pipes to the installation site yourself, without additional specialized equipment.
- Polypropylene PRR can be easily installed by welding using a special apparatus, which can be rented for a certain period of time. Having understood the simple technology of working with the device, the installation process will be completely easy and on your own.
- The material is harmless to humans, and the hot coolant does not change its chemical composition in any way.
- Special substances - stabilizers included in polypropylene, make it resistant to thermal loads and water hammer that occur in centralized system heating. Thanks to the plasticity of the material and fairly thick walls, the pipes are able to withstand even the freezing of water inside them without rupture.
- Polypropylene is able to dampen all sounds that may occur during coolant circulation within the circuit.
- All types water pipes made of this material, as well as components for them, have a very attractive price.
- A wide range of different components allows you to quickly assemble a structure of any degree of complexity.
- If high-quality material is purchased and installation is carried out correctly, the heating system will last a long time.
- Polypropylene pipes have a neat appearance and therefore do not require special decoration, cleaning or painting.
Of course, this material also has its negative sides, about which a few words also need to be said:
- Polypropylene does not protect the coolant from the penetration of oxygen from outside, which contributes to the occurrence of corrosion processes on the metal elements contour, and in autonomous system– including in boiler equipment. In addition, oxygen can promote the development aerobic bacteria, colonies and waste products of which over time can narrow the internal lumen of the pipes. This phenomenon can significantly reduce the normal circulation of the coolant.
Many manufacturers are trying to eradicate this drawback by “dressing” pipes in chemical-organic or metal oxygen barriers.
So, if a polypropylene pipe has aluminum reinforcement, which will help reduce linear deformation and serve as an oxygen barrier, on its outer side there may, for example, be the following marking:
PP-RCT – AL – PPR,
which, in essence, is the “formula” of the multi-layer structure of the product (layer markings are always indicated from internal to external):
1 – PP-RCT– modified polypropylene (random copolymer) with increased thermostatic properties;
2 – AL– aluminum reinforcement layer;
3 – PPR-- outer layer made of polypropylene.
4 – a special adhesive (glue) layer that connects all materials into a single structure.
- Another disadvantage of polypropylene is its rather large linear thermal expansion. This “minus” may appear when installing pipes in a system with a high-temperature coolant.
Elimination of the deficiency is also achieved by reinforcing the pipe, but in this case, fiberglass is often used for this purpose. The presence of this layer is indicated in the pipe “formula” or in diagrams by the letters FR or FG.
Fiberglass helps cope well with thermal expansion, but will not eliminate oxygen penetration. From this we can conclude that the best option for installation in a heating system would be pipes with an aluminum reinforcing layer. It will solve two problems at once - it will protect the coolant from the penetration of oxygen and significantly reduce thermal expansion.
For greater clarity of information about oxygen diffusion and thermal expansion for different types of multi-layer and single-layer pipes, some examples are shown in the table below:
| Types of polymer pipes | Designation (pipe “formula”) | Coefficient of linear thermal expansion, mm/m×°С | Oxygen diffusion indicators, mg/m² per day |
|---|---|---|---|
| Single layer pipes: | |||
| Made from cross-linked polyethylene. | PEX | 0.2 | 650 |
| Polypropylene | PPR | 0.17 | 900 |
| Multilayer pipes: | |||
| Made from cross-linked polyethylene with a barrier layer. | PEX-EVON-PE | 0.2 | 0.32 |
| Polypropylene, glass fiber reinforced. | PPR-FG-PPR | 0.035 | 900 |
| Polypropylene, reinforced with aluminum. | PPR-AL-PPR | 0.026 | 0 |
| Metal-plastic made from polyethylene with increased heat resistance | PERT-AL-PERT | 0.025 | 0 |
This table also contains data for polyethylene pipes, which will be discussed below.
Polypropylene is not a plastic material, that is, when installing circuits, all necessary, even small, turns, bends, etc., will have to be made from straight sections of pipe with welding of the corresponding elements. This is, in principle, easy to do, but not always convenient. And in some cases, precisely for this reason, restrictions are imposed on the use of polypropylene pipes - for example, they are not suitable for the “warm floor” circuit, since according to the rules it must be made from a single piece of pipe.
To summarize the information about polypropylene pipes, the following conclusions can be drawn:
Only a high-quality reinforcing layer made of aluminum will help get rid of all the disadvantages of polypropylene - it is in this version that PN-25 pipes are most often produced. This layer is an effective barrier to oxygen penetration and is capable of significantly reducing linear temperature expansion. The thickness of the aluminum layer in pipes of this type is 0.4÷0.7 mm.
Prices for polypropylene pipes for heating
polypropylene pipes for heating
Video: recommendations for choosing polypropylene pipes for a heating system
Installation of polypropylene pipes
The technology for installing polypropylene pipes will be discussed briefly, only so that you can clearly see that even a beginner with no experience in this work can handle it.
To carry out the work, you will need to purchase or rent a special device, without which installation will not be possible. Typically, all welding tools are placed in one work case. In the illustration presented, you can clearly see a set for welding work, which includes a special soldering iron. The working heating element of the device has holes for attaching the coupling and mandrel, through which the connecting elements and pipes will be heated before welding. The kit usually includes several pairs of feet and mandrels designed to connect pipes of different diameters. Often the kit also includes special scissors for cutting them.
In addition, you will need a tape measure - to mark the installation site and measure the required pipe sections, a pencil or marker, and you also cannot do without building level, with the help of which, if necessary, the evenness of the installation of pipes on the walls is controlled.
In order to melt polypropylene, the device heats up to high temperatures, about 270 ° C, so for safety reasons it is worth protecting your hands with gloves so as not to accidentally get serious burns.
If PN-25 or PN-20 pipes with aluminum reinforcement are used for installation, then before soldering from the extreme section of the pipe, to the penetration depth, it will be necessary to remove the top polypropylene and reinforcing layer. For this, another tool is used - a shaver. This pipe cleaning device can be hand-held or in the form of an attachment to a drill or screwdriver.
For example, we can consider welding one seam, which is carried out in the following order:
- On both sides heating element Using a soldering iron, heating pairs are screwed into special holes - mandrels and couplings of the required sizes that will correspond to the diameter of the pipes installed in the circuit.
If pipes of different diameters are used, then two or, if there is such a need and the design of the device allows, even three pairs of nozzles are screwed into the device.
- Next, the device is plugged in to warm up. The thermostat is set desired temperature, so for polypropylene, heating the soldering iron to 260÷270 degrees is considered optimal. Some soldering irons have regulators that already indicate the temperature for welding certain pipes.
- To heat the device to required temperature it will take about 10÷15 minutes, and during this time you can prepare pipe sections and the necessary profile elements (angles, taps, tees, adapters, bends, American coupling nuts, etc.) Heated and mating sections of pipes and connecting parts must be clean. If necessary, they can be wiped with an alcohol solution.
Pipe cutting is done with special scissors, and the cut must be perfectly perpendicular and free of burrs.
- If used PPR pipes- AL - PPR with a reinforcing layer located close to the outer surface, then the edges of the segments must be cleaned with a shaver. To do this, the pipe is inserted into the cutting part of the tool, then it is rotated, cutting off the top layer of PPR and the reinforcing aluminum layer, otherwise strong welding of the pipe and other parts will not work. Cleaning proceeds until the end of the pipe stops in the shaver cylinder - exactly the required depth of future penetration is obtained.
However, it should be noted that aluminum-reinforced polypropylene pipes are produced that do not require stripping, since the reinforcing layer is located quite deep under top layer PPR and will not interfere with welding. This is easy to figure out even visually.
If a pipe with fiberglass reinforcement is used, then cleaning the pipe with a shaver is not required.
If the pipe is not cleaned with a shaver, then the penetration depth is measured from the edge and marked with a marker. This value is different for pipes of different diameters.
In addition, it is advisable to try in advance the relative position of the pipe section and the element connected to it. The selected position can be indicated by risks, which will only need to be combined during welding.
- When the soldering iron warms up, the indicator light will notify you of this and will turn off when the temperature required for welding is reached.
- The connecting piece is put on the mandrel all the way, and the pipe is inserted into the coupling to the end of the section from which the reinforcing layer is removed, or to a pre-set mark. Both parts must be put on at the same time to obtain even heating.
- Next, the time required for complete heating of the surfaces to be joined is calculated. After its expiration, the elements are removed from the soldering iron and quickly connected to each other, that is, the pipe is inserted into the connecting element to the depth of the heated area. At the same time, if necessary, the applied marks of the relative positions of the parts are combined.
It is impossible to rotate the connected elements after they are connected, since they are not screwed into each other, but copolymerize.
- The parts are held in the specified position until they cool completely, about 20 seconds.
The table below shows the main necessary parameters for carrying out such welding work - the depth of heating of the pipe, the time for warming up and the period required for complete polymerization of the created joint (after which it is no longer afraid of loads).
| Pipe Ø in mm | Pipe heating depth during welding, mm | Warm-up time (seconds) | Time from joining the elements to complete polymerization of the seam (minutes) |
|---|---|---|---|
| 20 | 14÷16 | 6 | 2 |
| 25 | 15÷17 | 7 | 2 |
| 32 | 16÷20 | 8 | 4 |
| 40 | 18÷22 | 12 | 4 |
| 50 | 20÷25 | 18 | 4 |
| 63 | 24÷30 | 24 | 6 |
| 75 | 26÷32 | 30 | 6 |
| 90 | 29÷35 | 40 | 8 |
In the event that the seam does not work out for some reason, or its quality raises certain doubts, the situation can only be corrected by cutting out the defective section and replacing it with another segment and connecting element. It’s better to play it safe and spend a few more minutes than to leave a suspicious node.
As can be seen from the description of installation work, they are not very difficult, and this technological operation can be learned very quickly. When purchasing pipe elements for a heating circuit, you should take them with a small reserve, and also buy a few extra, very inexpensive connecting parts - so that you can make several “training” seams.
Polyethylene-based pipes
Another group of pipes used for water supply or heating systems is made of polyethylene. Of course, this is not the material that is used to make bags or other items used for everyday household needs, but polyethylene improved by various modifications and capable of withstanding fairly high loads.
There are two main types of modified polyethylene, which is used to make such products
"Cross-linked" polyethylene
Ordinary polyethylene has a linear structure of molecules, unconnected or poorly connected to each other. This predetermines the fact that the material does not like thermal effects - it quickly begins to “float” even with slight heating. But if the molecules are “stitched”, that is, cross-links are created between them, then the picture changes dramatically - all the existing advantages of the material are preserved, and additional ones appear.
Cross-linked polyethylene pipe
"Sewn" on molecular level the material acquires a number of increased positive characteristics, which can significantly expand the scope of its use. becomes more heat-resistant, tensile strength without significant loss of elasticity. In addition, a very interesting phenomenon of “memory” arises - when heated, the material tends to quickly restore its given shape after possible deformations as a result of high mechanical loads.
The higher the level of cross-linking, that is, the greater the number of intermolecular bonds in the structural structure of the material, the stronger and better it is.
All “cross-linked” polyethylene is labeled REX, but various technological methods are used for its production.
- The highest degree of molecular “cross-linking” is the treatment of polyethylene raw materials with peroxide - with this technology the level of cross-links can be up to 85%. This type of polyethylene is marked REX, and is considered the highest quality in this line of materials. True, it is also the most expensive, since the controlled technological process of its production is quite complex. Pipes with this marking are quite suitable for the heating system.
- A simpler method of “cross-linking” is to expose polyethylene raw materials to special reagents (“grafting”) and hot water steam - in this case, the “cross-linking” parameter is only 65%. Similar material is labeled REX-b. Such polyethylene is of lower quality, since after its manufacture the “cross-linking” process does not completely stop, so over time the pipe loses its elasticity, becomes stiffer, changes its other physical characteristics, giving a kind of “shrinkage”. This phenomenon leads to leaks at the connections, which means it will require constant monitoring, and, if necessary, timely tightening. Pipes with this marking European standards are considered unsuitable for installation in systems with elevated temperatures of coolant circulating under pressure. True, many of our masters often ignore this and use them as a cheaper option.
REX-b pipes can be used for laying in a “warm floor” system, where the temperature of the coolant does not exceed 45 degrees, and there are no unnecessary connections, that is, the laid circuit must be solid throughout its entire length.
- REX-c - this type of “cross-linked” polyethylene is obtained by exposing the raw material to a flow of electrons. This method is inexpensive and quite productive - the result is good quality products that are quite suitable for use in plumbing systems Oh. But for heating at high temperatures it is better to avoid such pipes.
Polyethylene with increased heat resistance PE-RT
PE-RT is a marking of polyethylene with increased heat resistance. The change in the molecular structure of the material occurs according to completely different principles, even at the stage of synthesis of raw materials.
Pipes made from this material are well suited for heating systems, as they have the following qualities:
- can withstand high temperatures and intrasystemic pressure;
— the declared service life of these pipes is 45÷50 years;
— PE-RT pipes, unlike REX, can be welded, which makes it possible to carry out repair and restoration work even without dismantling the damaged area.
— this type of polyethylene is quite elastic and is not afraid of liquid freezing inside the pipes. After defrosting, they can operate as before without repair or reinstallation.
Prices for PE-RT pipes
PE-RT pipes
Types of polyethylene pipes
Polyethylene pipes, like polypropylene pipes, can be with or without reinforcement.
Single-layer pipes without reinforcement
As mentioned above, these PE-RT and REX pipe options are excellent for laying underfloor heating system circuits.
Single-layer pipes are more suitable for laying “warm floor” circuits
This table presents comparative characteristics the most commonly used pipes for these purposes are PE-RT pipes with a diameter of 16×2 and 20×2 mm.
| Operational and technical characteristics of single-layer PE-RT pipes without reinforcement | PE-RT 16×2 mm | PE-RT 20×2 mm |
|---|---|---|
| Pipe volume (liters/linear meter) | 0.113 | 0.201 |
| Weight (kg/linear meter) | 0.07 | 0.127 |
| Minimum bending radius - 5d (mm) | 60 | 100 |
| Coolant temperature (˚С) | 20 | 20 |
| Working pressure (bar) | 20 | 20 |
| Service life (years) | More than 50 | More than 50 |
| Temperature (˚С) | 75 | 75 |
| Working pressure (bar) | 10 | 10 |
| Service life (years) | More than 50 | More than 50 |
| Temperature (˚С) | 95 | 95 |
| Working pressure (bar) | 6 | 6 |
| Service life (years) | More than 50 | More than 50 |
| Ultimate pressure (bar) | 6 | 4.5 |
| At temperature (˚С) | 110 | 110 |
| Ultimate pressure (bar) | 11 | 10 |
| At temperature (˚С) | 90 | 90 |
| Linear elongation coefficient max at temperature 95˚С (mm/m ×˚С) | 0.18 | 0.082 |
| Thermal conductivity coefficient (W/m×°C) | 0.41 | |
| Roughness of internal surfaces (µm) | 0.125 (Class 10) | |
| Design strength of material (Mpa) | 6.3 | |
Pipes of this type can be single-layer, but this, as in the case of polypropylene, creates a risk of high oxygen diffusion through the walls. Therefore, to eliminate this drawback, some manufacturers provide a special layer - the EVON protective barrier - this is a complex copolymer made on the basis of ethylene-vinyl alcohol.
Metal-plastic pipes based on polyethylene
In most cases, metal-plastic pipes are called polyethylene products with an internal aluminum layer. These include PERT - AL - PERT, REX - AL - REX, PERT - AL - REX, or even combined option using polypropylene as the outer layer PERT - AL - PPR.
The table shows some comparative characteristics metal-plastic pipes based on cross-linked and heat-resistant polyethylene:
The aluminum layer, just as in the case of polypropylene, acts as a protective oxygen barrier and improves mechanical characteristics products, makes pipes more resistant to thermal influences, reducing their linear expansion. In addition, metal-plastic pipes hold their curved shape much better.
It is recommended to purchase metal-plastic pipes in specialized stores, where the seller can confirm the quality of the product with an appropriate certificate, and not in spontaneous markets, where prices can be attractive at a low level, but the products themselves are very often low-quality products from an unknown manufacturer that can present a lot of unpleasant “surprises.”
Do not forget that even fairly high-quality options during their operation can, over time, cause delamination between the aluminum layer and the polymer. Well, if we talk about inexpensive pipes, then delamination in them, one might say, is guaranteed - it’s only a matter of time. Such destructuring of the walls is fraught with a pipe breakthrough, and it’s not so bad if this happens on an open section of the pipeline - the most catastrophic surprise may be a leak in a closed section or finishing coat"warm floor" circuit.
Therefore, saving on any heating elements is not recommended, since if your apartment, and even more so your neighbor’s, is flooded, the costs will be many times higher.
Installation of polyethylene pipes
Installation work on the installation of heating circuits consisting of polyethylene-based pipes can be carried out in several ways - using compression, press-fit or special welded fittings.
The basic installation principles for all polyethylene pipes are the same, but some manufacturers make special connecting parts for their products that are slightly different from all others in design.
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Connection with compression threaded fittings
If you install the circuit yourself - at home, and without the use of special tools, then it is most convenient to choose metal-plastic pipes with compression threaded fittings.
The process of assembling the pipework is completely simple and consists of the following steps:
- The required length of pipe is measured and cut with special scissors or a hacksaw. The main thing is that the cut is perfectly perpendicular, even and neat, without denting the walls.
- Next, the fitting is disassembled, and a crimp nut is put on the pipes and advanced 100÷120 mm, threaded towards the joint, and then, in the same way, a cut brass ring.
- It is recommended to flare the inner surface of the pipe at the connection with the fitting, that is, slightly expand it using a manual calibrator.
- The next step is to insert the fitting into the machined end of the pipe until it stops. In this case, the rubber gasket must be in the recess (groove) intended for it.
- The split ring is moved close to the fitting, into its place, then the compression nut is moved and tightened. Work is being carried out wrenches, and do not tighten the nut too tightly. Tightening can be carried out only if necessary - during pressure testing, when applying test pressure, if signs of leakage appear.
- After this, subsequent sections of pipe are installed and secured in the same way on the other side of the fitting, tap, tee, etc. When connecting some elements to each other, as well as when transitioning to other types of pipes or to the pipes of devices, threaded connections are used.
Video: connecting a metal-plastic pipe with a compression fitting
Press fittings
Installation using press-fit fittings is a more complex process that requires special equipment to heat or tighten the fitting elements. This installation technology can be applied to both polymer and metal-plastic pipes. In this case, the special property of “cross-linked” polyethylene is used - after deformation, it returns to its original shape.
Installation of pipes using press fittings takes place approximately in the following sequence:
- The fitting is also disassembled, and then its sleeve is put on the prepared edge of the pipe and slides along it.
- Next, a special expander is inserted into the pipe. This operation is necessary to expand the installation section of the pipe to such a limit that the fitting pipe can be inserted into it. After expansion, polyethylene tends to return to its original shape, and this process becomes more active when the material is heated. The pipe tapers and fits tightly around the embossed fitting of the fitting.
- After the fitting is installed in the pipe, the sleeve must be pressed onto the fitting. For this operation you will have to apply a certain force, so a special tool is used to carry it out - a pressing machine. It can be manual or mechanical.
- Once the sleeve is in place, the assembly process is complete.
Assembly options may be different - each manufacturer has its own “tricks”. But all the time the principle remains almost the same.
Welding connection
This is a connection of PE-RT pipes using a special apparatus and special fittings. It should be noted that not all PE-RT pipes are designed for this type of connection. Therefore, when purchasing material, this nuance must be clarified with a specialist in the store.
Summing up, it would be useful to mention once again that one should not save unwisely and choose those pipes that do not correspond to the location and conditions of their operation. A momentary gain, and probably not too significant, can turn into very serious troubles and sad, and sometimes catastrophic, consequences. study at the link.
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Evgeniy AfanasyevChief Editor
Author of the publication 03.02.2016
A feeling of comfort in the home no matter what weather conditions outside the window is created thanks to proper operation heating system. Its efficiency, quality and service life directly depend on the pipes. Today, installation of heating systems is increasingly carried out using cross-linked polyethylene pipes. The properties of this material allow it to be superior to other options in many ways. However, when installing such pipes with your own hands, you need to know some nuances, which will be discussed in this article.
Product characteristics
Pipes made of ordinary polyethylene (PE) are widely used to create heating, water supply, and sewage systems.
Their main characteristics include several points.
- Frost resistance, allowing the use of polyethylene structures at temperatures down to -20 degrees. This is a great advantage, since it makes it possible to carry out any work with pipes in winter, including installing new equipment or repairing failed systems.
- Resistant to high temperatures (up to 40 degrees).
- Flexibility that prevents pipes from deforming when bent.
- Plastic. Polyethylene products can expand or contract depending on temperature without losing their shape.
In order to obtain higher pipe strength, a reliable and high-temperature resistant material called “cross-linked polyethylene” (PEX) was created.
Its main feature is the maximum operating temperature – 90 degrees. Sometimes such pipes can withstand temperatures of 100-110 degrees, maintaining normal operation for a certain time.
Other important feature cross-linked polyethylene pipes – high oxygen permeability. When installing such products, you must remember this property and use aluminum foil or a special polyvinylethylene coating to protect them.
Production methods
The technology of “cross-linking” polyethylene was invented in 1968 by the Swedish chemist Thomas Engel. In 1972, one of the Swedish companies put it into industrial production. This technology still leads the market today.
The purpose of the cross-linking process is to connect molecules into a three-dimensional network as a result of the formation of cross-links. During its course, polyethylene, the molecule of which contains hydrogen and carbon atoms, loses part of the hydrogen. Therefore, free bonds appear to connect molecular units with each other, as a result of which the molecules are tightly “stitched” together.
There are different ways to produce cross-linked polyethylene. The technical characteristics of the finished pipe depend on the method. The longest, but at the same time the highest quality method is to treat polyethylene with peroxide. It gives the highest degree of cross-linking (85%). A pipe made of such material can easily withstand low and high temperatures, resists the effects of chemicals, becomes resistant to shocks and other mechanical influences, and can restore its original shape.
Another method is to irradiate the material with electrons in an electromagnetic field. This cross-linking involves irradiating the finished product with electrons.
There is also a physical cross-linking method that uses X-rays. However, such structures turn out to be rigid. They are not resistant to extreme cold and cannot return to their previous shape.
Common is chemical method silane cross-linking. It is more effective compared to physical. This produces polyethylene that is optimal in price and quality, suitable for everyday use.
A heat-resistant, strong material, pipes from which are excellent for the installation of heating systems of any type, hot and cold water supply systems, and underfloor heating equipment is obtained as a result of each production method. You just have to choose the right one required characteristics, and also remember that the higher the degree of crosslinking, the higher the price of the material.
Advantages
Pipes made of cross-linked polyethylene have a number of advantages, due to which they are most often used for installation heating systems.
- Resistant to high temperatures (up to 95 degrees). Products made from cross-linked polyethylene are capable of expanding or contracting up to certain sizes under the influence of low and high temperatures.
- Excellent mechanical strength achieved through good molecular memory of the material. It easily restores its original shape after deformation, unlike conventional polyethylene pipes.
- Corrosion resistance. Products made from cross-linked polyethylene are not afraid of corrosion either inside or outside (unlike, for example, copper). This quality allows you to avoid washing and cleaning PEX pipes, which is periodically necessary for their metal “brothers” and has a rather high cost.
- Guaranteed against the appearance of growths inside pipes. Unlike steel pipes, which after some time become covered from the inside with growths that slow down the flow rate, the internal walls of PEX pipes have a special Teflon coating and are not subject to deposits of layers. Due to the smoothness of the internal walls, the heating system always has high hydraulics.h
- Light weight material. For example, 1 m of pipe with a diameter of 16 mm weighs only 90 g. Therefore, they are convenient to transport and easy to install.
- Easy to install. PEX products can be installed according to any scheme. They allow you to make loops and any number of bends. In this case, no special welding equipment is required, since the pipes are connected without requiring soldering or gluing. Heating pipes are sold in 100 and 200 m lengths, which makes it possible to install large sections of the system without the use of fittings.
- PEX products are environmentally friendly and resistant to the growth of harmful bacteria inside them. The material is included in the environmentally friendly group, therefore it is widely used for drinking pipelines.
Flaws
Despite the huge number of advantages, cross-linked polypropylene cannot be called ideal.
It is worth considering its disadvantages.
- Brass fittings used to connect cross-linked polyethylene pipes for heating are susceptible to corrosion, so you have to pay close attention to the choice of materials for screed or plaster. It is better not to use materials that cause corrosion of the fitting, otherwise the quality of the heating system will noticeably decrease.
- Pipes made of cross-linked polyethylene are “afraid” of ultraviolet radiation. Therefore, they are more suitable for indoor use, in closed systems and communications. To use such products outdoors, a special protective casing is required.
- The price of such pipes, in contrast to the cost of metal-plastic and ordinary polyethylene, is quite high.
Therefore, before purchasing cross-linked polyethylene pipes, you must carefully study all the technical characteristics of the heating and water supply system of the room in which you plan to install them.
Work process
If special knowledge and skills are required when installing metal pipes, then this is not required when installing cross-linked polyethylene pipes. For high-quality execution The work requires only certain tools and a little effort.
Pipes made of cross-linked polyethylene are connected with fittings made of various materials: polymers, brass, bronze. It is best to use polymer fittings (for example, Rehau), since they are high quality, do not corrode and last a long time.
In general terms, the process for installing PEX pipes is as follows:
- the end of the connecting structure is expanded using a flaring tool, giving it a larger diameter;
- insert the fitting fitting there;
- Using a press, the tension sleeve is pressed in, giving the greatest strength to the connection.
This technology makes pipe connections reliable and durable. The service life of such systems corresponds to the service life of the pipes themselves.
High-quality heating of a house or apartment is the key to comfort and coziness of living. But it doesn’t depend on last resort on the quality of the created heating system. Today, for these purposes, manufacturers offer many different materials that significantly simplify installation work and increase the durability of the systems being created.
It is clear that none of the water heating systems can do without a fairly large number of pipes, and their selection should be approached with maximum responsibility. Gone are the days when steel VGP pipes were practically no alternative. The modern choice is rich. For example, cross-linked polyethylene pipes for heating are a relatively new material that has many advantages over others. However, it also has its own characteristics that should be taken into account. In order not to make mistakes when considering the question of what is suitable, during installation work and further - already during the operation of the heating system, it is necessary to have an idea about the main characteristics and capabilities of this material.
What is cross-linked polyethylene?
You should not think that ordinary, familiar polyethylene, sold in the form of, for example, film various densities, is the same material from which they are made for plumbing and heating circuits. For products that will experience considerable operational loads, cross-linked polyethylene is used. And the key word in the name is still “stitched”. Yes, the basis is the same, but the differences lie in the features of the molecular structure.
We will try to clearly explain the difference.
Ordinary polyethylene has a linear molecular structure. Long chains of linear molecules are not connected to each other. Therefore, the material is not very resistant - it is easy to break it by mechanical action, and even with not very high heating it begins to “float”.
Technological chemists tried to slightly change the molecular structure of the material, namely, to try to connect linear molecules with cross-links.
During the production of this material, molecular chains are “cross-linked”, thereby creating numerous stable cross-links. Essentially, a linear structure becomes three-dimensional. It is important that the material not only does not lose all its positive characteristics, but also acquires much greater stability. The more intermolecular bonds are created, the higher the degree of cross-linking is considered.
One of the very interesting and useful properties, acquired by polyethylene as a result of cross-linking, is a kind of “memory” of the original shape of a product made from this polymer. So, with increasing pressure, with mechanical or thermal effects on the same pipe, its deformation is quite possible. However, after the loads are normalized, removed or weakened, the material tends to restore its previously specified original shape. Agree that this is a very important advantage for a heating system.
Polyethylene pipePE-RT
An innovative development in the production of pipes has become products made from polyethylene PE-RT (polyethylene with increased heat resistance - “Polyethylene of Raised Temperature Resistance”). By and large, this type of polyethylene cannot be fully called a cross-linking product. The fact is that the initial granular raw materials from which products are made have stable intermolecular bonds, and even more branched than those of PEX.
The process of creating PE-RT became possible with the development of technology that makes it possible to control the processes of spatial formation of macromolecules. These developments make it possible to create materials whose structure will correspond to precisely specified parameters. This opens up opportunities to focus on a certain property of materials.
The abundance of intermolecular bonds makes the material resistant to internal and external loads, eliminating the appearance of cracks or breaks during strong bending. Despite aggressive influences, PE-RT, unlike PEX, always retains its thermoplasticity. Therefore, the connection of pipes of this type can be made not only using crimp fittings, but also using welding technology. This simplifies and reduces the cost of installation, and high-quality welding ensures the highest reliability of the joints, and therefore the heating system as a whole.
Considering the advantages of PE-RT, we can conclude that it is confidently displacing previously widely used PEX products from the market. These advantages include the following qualities:
- The manufacturing technology of PE-RT is much simpler, since it does not require an intermolecular cross-linking cycle. All the necessary properties to achieve the required parameters are already included in the semi-finished raw material. Interestingly, waste heat-resistant polyethylene can be recycled without losing any of the original qualities of the product.
- The durability of PE-RT pipes is estimated at 50 years or more.
- This type of pipe, due to its plasticity and strength, is able to withstand several freezing cycles along with the coolant, without losing its original qualities and depressurizing the heating system.
- PE-RT pipes can be repaired, which is impossible for PEX analogues.
- Due to its structure, the material perfectly absorbs the sound of coolant flowing through it. In addition, due to their plasticity, they do not produce squeaks in the system, which is sometimes the problem with PEX pipes.
PE-RT is used both for the production of metal-plastic pipes and those made only from this polymer.
Both the metal-plastic version and pipes made of PE-RT polyethylene have higher technical and operational characteristics than their PEX counterparts.
Many PE-RT pipes, if they do not have an aluminum layer, are equipped with special oxygen barriers. Manufacturers use their own developments as this layer, for example EVON or OXYDEX.
As an example, we can give a table with the main technical and operational characteristics of PERT-AL-PERT pipes from the rather popular COMPIPE production brand:
| Name of parameters | Indicators | |||
|---|---|---|---|---|
| Outer diameter, mm | 16 | 20 | 26 | 32 |
| Wall thickness, mm | 2 | 2 | 3 | 3 |
| Coil length, m | 200 | 100 | 50 | 50 |
| Pipe weight (g/linear m) | 113 | 149 | 264 | 331 |
| Pipe cavity volume (l/linear m) | 0.113 | 0.201 | 0.314 | 0.531 |
| Minimum bending radius, mm | 45 | 60 | 95 | 125 |
| Outer layer (material) | PE-RT (polyethylene with increased heat resistance) | |||
| Inner layer (material) | PE-RT (polyethylene with increased heat resistance) | |||
| Aluminum layer connection method | TIG butt welding | |||
| Operating temperature, ˚С | 70 | |||
| Maximum temperature, ˚С | 95 | |||
| Maximum pressure, bar | 10 | |||
| Linear expansion coefficient, (К⁻¹) | 2.3×10⁻⁵ | |||
Prices for PE-RT pipes
PE-RT pipes
Methods for connecting polyethylene and metal-plastic pipes
To connect pipes made of cross-linked polyethylene, special fittings are used, and the installation itself is carried out using the compression method (crimping) or using diffuse welding technology. Fittings can be polymer or metal (brass or bronze). Polymer fittings are well combined with pipes made entirely of PEX or PE-RT polyethylene.
Such connections have already proven their high reliability, and therefore are quite suitable for the operating conditions of heating systems. Of course, it is necessary to choose pipes and fittings from the same manufacturer, since only such a combination will guarantee the quality of installation.
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So, there are several connection methods.
One of the simplest and fastest installation methods is the option with a sliding sleeve. The whole process consists of three steps:
1 - Place a crimp sleeve on the pipe and move it away from the edge by about 100 mm. Then, the pipe cavity at the edge is slightly expanded with a special expander. This is necessary so that the fitting can easily fit into it.
2 - Next, the fitting is inserted into the expanded channel of the pipe until it stops. Since cross-linked polyethylene will tend to return to its original shape after the expansion process, it will press tightly against the material of the connecting part.
3 - At the final stage, the sleeve that was put on earlier is shifted, closing the created connection. This way, the polyethylene will be tightly clamped between the fitting and the sleeve. Shifting the sleeve requires considerable effort, so it is done with a special tool.
Another option, already mentioned above, is suitable for connections of both pipes made only from polyethylene and metal-plastic ones. This method includes approximately the same stages of work, but at the end of the process, the sleeve moved to the edge of the pipe is crimped with special pliers.
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PERT-AL-PERT pipes can be connected using a fitting and a ferrule nut:
- On metal pipe The union nut is put on first, then the ferrule.
- Then, after slightly flaring the edge, a metal fitting is inserted into the pipe until it stops, which often has rubber sealing rings, but may also be without them.
- The next step is to first slide the ferrule ring onto the edge of the pipe, and then the nut on top of it.
- The nut is screwed tightly onto the thread of the fitting.
This connection method does not require special tools- just have a wrench or wrench on hand. However, according to experts, such pipe connecting units are not highly reliable. A leak may appear immediately after starting the heating circuit or after a short period of time. In any case, it is not recommended to leave such joints without visual inspection.
Another installation method is diffusion welding, which can only be used to connect PERT-based pipes. Of course, special fittings must be available for such installation.
This work is complicated by the need for a special welding machine. If it is possible to rent such a device, it is quite possible to install the system yourself. In general, the process is very similar to welding polypropylene pipes and is usually mastered very quickly even by beginners.
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Advantages and disadvantages of cross-linked polyethylene pipes
To summarize the above, it makes sense to highlight the advantages and disadvantages of PEX and PE-RT polyethylene pipes.
So to benefits pipes made of cross-linked polyethylene when used in heating systems include the following factors:
Resistance to high temperatures, and this is especially pronounced in PE-RT pipes.
- Excellent strength characteristics - the pipes are resistant to external mechanical influences and internal baric loads.
- The elasticity of the material allows the use of pipes in complex laying patterns with many turns under a small radius.
- Even after serious deformations, the pipe tends to restore its shape.
- Inert to corrosion, as well as aggressive components of the coolant.
- The ideal smoothness of the inner walls does not create significant hydraulic resistance to the coolant circulating through the pipes. In addition, the likelihood of insoluble deposits on the internal walls is almost completely eliminated, even if low-quality coolant is used.
- The light weight of the pipes and the large length in coils speeds up and simplifies installation work on laying long circuits.
- High reliability of connections.
- The environmental friendliness of the material allows them to be used for installation in a water supply system, from which water is used for drinking and cooking.
- Pipes on open areas do not require periodic painting - they are quite “pretty” in themselves.
However, in order to have a complete understanding of pipes made of this material, it is necessary to highlight them flaws , since they are also available:
- Both PEX and PE-RT pipes have relatively low UV resistance. Therefore, it is better to use them on closed areas(the same contours of the “warm floor” or wiring hidden in the walls).
- The cost of quality pipes complete with the necessary press fittings can be quite impressive! In addition, one cannot discount the need for a special installation tool, and the skills to work with it.
- Great care should be taken when using cross-linked polyethylene pipes in a heating system connected to a central heating system. In any case, it is better to check the acceptable operating parameters several times and compare them with possible operating modes of the system, about which you need to obtain information in advance from local utilities.
You may be interested in information about what is involved in a heating system
A few words about brands and prices
The issue of the cost of purchased pipes is always important. But it should not be decided solely from the standpoint of maximum cost savings, to the detriment of quality. Therefore, the main thing we can advise is to choose materials from truly reputable manufacturers in order to “bite your elbows” due to problems that begin during installation or, worse, already during operation of the system.
Pipes produced by well-known European companies have earned a good reputation. These include “Rehau”, “Henco”, “Uponor”, “Kermi”, “Oventrop” and others. Some domestic firms are also trying to keep up with them, but for now, professionals still prioritize imported products.
The table below shows several pipe options that are well suited for installing a “warm floor” system. Prices are average, and in different regions they may differ from those shown - this is easy to check on the spot.
| Manufacturing company and pipe model | Brief technical specifications | Coil length | Price per linear meter |
|---|---|---|---|
| Uponor PEXа evalPEX Q&E 16 x 2.0 | Diameter 16 mm. Cross-linked polyethylene PE-Ha, wall 2 mm, t max - up to 95 degrees, (short-term heating up to 110) | 50 – 240 m | 130 rub. |
| Uponor PEXа evalPEX Q&E 20 x 2.0, | Diameter 20 mm. Cross-linked polyethylene PE-Ha, wall 2 mm, t max - up to 95 degrees, (short-term heating up to 110) | 50 – 120 m | 150 rub. |
| REHAU "Rautitan stabil" | Diameter 16 mm. Metal plastic, PE-Xc/AI/PE wall 2.6 mm | 100 m | 175 rub. |
| REHAU "Rautitan stabil" | Diameter 20 mm. Metal-plastic, PE-Xа–AL–PE wall 2.9 mm | 100 m | 200 rub. |
| REHAU "Rautitan flex" | Diameter 16 mm. Cross-linked polyethylene RAU-PE-Xa, wall 2.2 mm | 100 m | 190 rub. |
| REHAU "Rautitan Pink" | Diameter 16 mm. Cross-linked polyethylene RAU-PE-Xa, wall 2.2 mm, t swing - up to 90 degrees | 120 m | 150 rub. |
| Contour PERT D 16 red | Diameter 16 mm. Monolayer PERT pipe Russian production., t max – up to 90 degrees, pressure – up to 6 bar. | 200 m | 55 rub. |
| BioPipe PERT 16x2.0 | Diameter 16 mm. | 240 m | 50 rub. |
| Thermotech MultiPipe PE-RT II, 16*2 mm | Diameter 16 mm. Five Layer PERT Pipe with Diffusion Barrier | 240 m | 150 rub. |
The presented selection deliberately does not show pipes of the lowest price category, as well as products that are questionable or not at all famous manufacturers. The reasons are probably clear - the author simply does not have the moral right to recommend such material for installing a heating system that is designed to last for several decades of operation.
3.3
Impeccable operation of the heating system is the key to a comfortable and cozy stay for household members indoors in any weather. Modern materials and the technologies used in the installation of heating systems make their operation long and efficient. The main element of any heating system is the pipes that connect all elements and communications. The choice of pipes should be approached very responsibly, since the service life of all equipment and its serviceability depend on it.
IN Lately The heating and water supply system is installed using polyethylene pipes. This material has properties that give it a great advantage over other analogues. However, during the operation and installation of heating made of cross-linked polyethylene, some technical features this material, which you should learn about in more detail.
Features of polyethylene pipes
Conventional polyethylene pipes, designated PE, are used for installation of heating, sewer and water supply systems, including drinking water supply. Pipes made of this material have some features, among which are the following:
- Resistance to sub-zero temperatures. Operation and maintenance of polyethylene systems is allowed at -20 degrees. This is important when carrying out any production work in winter, including the installation of new equipment and repair of failed areas.
- Flexibility and plasticity. These properties make it possible to avoid pipe deformation not only when bending. Flexible heating pipes made of cross-linked polyethylene are capable of expanding when the working medium freezes and contracting when it thaws. In this case, the product takes its previous shape.
- Use of polyethylene pipes at a working environment temperature of no more than 40 0 C.
The last feature can be called a disadvantage, but progress in scientific and technical directions helps solve the problem. Thanks to this, special pipes made of cross-linked polyethylene were designed, which can be used in water supply and heating systems with coolant temperatures up to 90 0 C. The new material is designated PEX.
Characteristics of cross-linked polyethylene pipes
To obtain a material with higher strength characteristics, polyethylene was processed under high pressure. As a result, the polyethylene molecules formed stronger cross-links.
To obtain a kind of “stitching” the following methods were used:
- Polyethylene was placed in an electromagnetic field and irradiated with electrons.
- The material was treated with peroxide.
- Polyethylene was treated with nitrogen compounds.
The result of each method was durable and thermally stable polyethylene, which is quite suitable for use in individual and central heating systems, radiator and panel type, in hot and cold supply systems. cold water, as well as for the “warm floor” and “snow melt” systems. Polyethylene pipes obtained as a result of treatment with peroxides are of higher quality.
To operate cross-linked polyethylene pipes, certain requirements must be met:
- The maximum operating temperature is no more than 90 0 C. However, in extreme cases, products made of cross-linked polyethylene can operate for a certain time at temperatures up to 100 degrees.
- The working pressure in the system cannot be more than 10 bar, provided that the coolant is heated to 90 degrees, or 25 bar when the working environment is heated to no more than 25 degrees.
One of the features of cross-linked polyethylene is its high oxygen permeability. This property is a disadvantage of the material, as it limits its use in its pure form, especially in heating systems. closed type. To eliminate this drawback, cross-linked polyethylene is reinforced with a layer of aluminum foil or protected with a special polyvinylethylene coating.
Connection of polyethylene heating pipes
To connect pipes made of cross-linked polyethylene, fittings are used, for the manufacture of which we used various materials, including polymers, brass and bronze. Polymer fittings are characterized by high quality and sufficient for a long time show themselves only with the best side. That is why the products are very popular among consumers.
The fitting process for cross-linked polyethylene pipes is as follows:
- Using a flaring tool, the end of the connecting pipe is given a larger diameter, spreading it apart.
- The fitting fitting is placed into the resulting hole.
- Using a press, the tension sleeve is fixed to the pipe. This makes the connection stronger.
Application of such technological process increases the service life of the connection and increases its strength. In this case, the operational period of the connection completely coincides with the service life of cross-linked polyethylene pipes. If necessary, you can insulate heating pipes with appropriate material.
Advantages of polyethylene pipes for heating
Pipes made of cross-linked polyethylene have a large number of advantages, thanks to which they stand out from the general group of pipes used for the installation of heating systems. Among the particularly significant advantages are the following:
- High temperature resistance and excellent strength characteristics. Unlike polypropylene and conventional polyethylene heating pipes, the new material will not change its shape when exposed to high temperatures.
- Resistance to the formation of corrosion spots. Compared to copper products, cross-linked polyethylene pipes are not subject to corrosion. Moreover, this process does not occur either inside the structure of the material or on the surface.
- No build-up inside the pipes. The internal walls of PEX pipes are not covered with layers after transportation of any aggressive environment. This differs from most steel pipes, which after a certain period of time become less productive due to a decrease in flow velocity.
- Restoring the previous form. Many pipes lose their shape as a result of certain mechanical stress. However, cross-linked polyethylene pipes can expand or contract to certain parameters under the influence of low temperature or mechanical stress.
- Low weight. The light weight of the material makes it more convenient to transport cross-linked polyethylene pipes and facilitates the installation process.
- Easy installation and great possibilities. PEX pipes can be laid in any pattern, including the formation of a loop or a large number of bends. Connection using fittings simplifies the installation process, as it eliminates the need to use welding equipment, soldering and gluing.
- Environmental Safety . Cross-linked polyethylene belongs to the group of environmentally friendly materials, so PEX pipes can be used to transport clean drinking water.
However, such pipes cannot be called completely flawless due to the presence of some shortcomings.
Flaws
Firstly, when connecting cross-linked polyethylene pipes for heating using brass fittings, the list of materials used for screed or plaster is limited. It is better to exclude those that can cause corrosion of the fitting, so as not to reduce the quality of the system.
Secondly, cross-linked polyethylene pipes are characterized by low resistance to ultraviolet radiation, so it is better to use them in closed systems and communications.
Third, it is recommended that PEX pipes be used in systems that have pressure and temperature ratings that meet the pipe thresholds. When choosing cross-linked polyethylene pipes, you should carefully study the technical characteristics common system and features of the residential premises where it is planned to install a heating system from the specified material.
The practical use of cross-linked polyethylene for heating shows that the material fully complies with the parameters and conditions modern systems, which function flawlessly on Russian territory.