What is the best material for heating pipes? Heating using various pipes
The choice of materials for heating
Many people pay great attention to the arrangement of their homes. Everyone wants to live in comfortable conditions, so major expensive repairs are being made, comfortable furniture, beautiful textiles, and expensive accessories are being purchased. But all these chores will not be a joy if the house is cold, damp and uncomfortable. Therefore, it is advisable to pay special attention to the thermal insulation of the dwelling and the installation of the heating system.
It is important to draw up a high-quality project, calculate the pressure and choose the right pipes. Manufacturers produce a wide range of elements for the hot water system. What, and what to give preference to? Let's figure it out.
Main selection criteria
Any specialist has a whole arsenal of tools that help him make right choice. Each type of pipe has both positive and negative characteristics. Therefore, given them, it is not difficult to find the optimal solution. Much also depends on knowing what heating systems exist and what engineering conditions must be met. Here is a list of basic initial data that must be taken into account when choosing pipes for heating:
- The presence of a forced or gravity heating system
- Laying method - internal or external
- Complex or simple system configuration.
- System pressure power
- Maximum water temperature
Below will be a list existing options. It will help you decide which pipes to choose.
Types of pipes and main characteristics of the source material
On sale today you can find several varieties of pipes for heating. It:
- From black metal.
- Polypropylene.
- Innovative cross-linked polyethylene materials.
- Metal-plastic products.
- copper samples.
- From stainless steel.
Ferrous metal pipes
Steel heating pipes
Until recently, this choice was the only alternative for installing a heating system. And it should not be treated as a relic of the past. In a gravity heating system operating offline, this option is the most optimal solution. And all because in this case a large diameter pipeline is needed. This material has certain advantages. He:
- Durable.
- It has a small linear expansion and high thermal conductivity.
- Resistant to high temperatures.
- Able to withstand fairly high pressure.
- The price component of the issue is democratic and very affordable.
Carbon steel withstands temperatures up to +1500 degrees Celsius. If the welding work is done with high quality, the gravity heating system will work flawlessly. What are the disadvantages of the indicated choice?
- First, the complexity of installation. For welding, special equipment is used, which can only be operated by an experienced welder. This circumstance significantly increases the cost of installation.
- Secondly, it is necessary to take into account the fact that the overall dimensions of the pipes make their installation difficult. It is possible to assemble such a system only before the start of finishing work. This process is laborious, dirty, and time consuming.
- Welding can easily damage wallpaper and flooring, so these installation features must be taken into account. If there is a need to assemble the heating system after the repair, it is better to find an alternative to ferrous metal pipes.
- Thirdly, experts do not recommend using the designated option for installing a pipeline hidden in the walls. Metal is subject to corrosion, so anything can happen.
Summarizing the advantages and disadvantages, it is easy to make a choice.
Polypropylene pipes
Polypropylene pipe for heating
Polypropylene pipes are available and have a low weight, so they will not increase the load on bearing structures. In addition, they:
- They have a smooth inner surface. It does not accumulate dangerous deposits, which often clog the pipe and make its internal section impassable.
- Manufacturers give high warranty periods and say that polypropylene pipes can last for 25 years.
- The material is resistant to low temperatures.
- He has a wonderful appearance, which harmonizes well with elements of modern interior decoration.
For the installation of elements, special equipment is used. Anyone can form a chain, for this you do not need to have special skills and abilities, and you can always rent a soldering iron. And this circumstance can also be added to the merits of the described material. And everything would be fine, but you need to take into account the disadvantages of propylene pipes:
- They don't bend. In order to make a turn, you need to use additional fittings that violate the integrity of the system.
- If there is a need to repair a single section, it will be necessary to replace the entire span from fitting to fitting. And it's also not very convenient.
- Polypropylene has a low rigidity, so sagging of the system is often observed, which leads to breakage.
- But the highest disadvantage of this choice is low heat resistance. Working temperature plastic pipes 70 degrees, so there are strict restrictions on their use.
Innovative XLPE pipes
XLPE pipes - new
This material still belongs to the novelties of prefabricated technologies. But you can already judge its advantageous characteristics:
- The material has a high density. He is resistant to high pressure and high temperatures, and also has a memory effect. If bent, it will hold its position, but will straighten out when heated again. This feature greatly simplifies wiring.
- Manufacturers claim that PEX pipe has a lifespan of 50 years.
- You can assemble the system using press fittings that do not require the use of additional professional equipment.
- The lumen of the pipe does not become clogged and remains low throughout the life of the pipeline.
- Such elements can be mounted in the wall, since they do not have a high expansion coefficient and are not afraid of corrosion.
Based on these characteristics, we can safely say that cross-linked polyethylene is.
metal-plastic
Multilayer pipe PE-Xc
The most popular choice, justified in operating conditions central heating. It successfully combines the advantages of metal and plastic. Advantageous characteristics are formed due to the design features and the multilayer structure of the material.
The inner layer is a resistant polymer that prevents precipitation. It is protected by a layer of aluminum foil. It, in turn, is covered with a layer of polymer that protects the multilayer structure from the effects of the external environment. Thanks to a special glue, all connections of the layers are very strong and ductile. As a result, the output is a product with excellent technical characteristics:
- Have a smooth inner surface
- Excellent aesthetic appearance.
- durable
- Economical.
- Deprived of static and linear expansion.
- Easily repairable.
- Installation is carried out without the use of professional equipment.
Their only drawback is their high price. A significant share of the costs falls on connecting fittings, and they also have a significant flaw - a narrowed section. This makes it difficult to cross, so this material is not recommended for use in suburban construction. In the event of freezing water, metal plastic pipes may break.
Copper analogues
Copper heating pipelines
When deciding which pipes are best used for heating, experts prefer copper systems. This is the most expensive option, but the operating conditions and technical characteristics of the metal easily compensate for this disadvantage. Only copper pipes have a wide operating temperature range.
Sometimes it happens that only these constructions can be used. If the coolant transmits water over 500 degrees, only copper can withstand the load. She is not afraid of high low temperatures. Only copper can ensure the safety of the heat conductor if the system freezes.
The same applies to water hammer. The average service life of a copper pipe is 100 years, which is several times higher than the capabilities of the materials described above. In addition, the copper tap-off system looks very vintage. Over time, it acquires a noble patina that looks great in any finish. Copper pipes have practically no drawbacks. The only negative is the high price of products.
Stainless steel pipes
Corrugated Stainless Steel Pipe
Stainless steel is the only material that can compete with copper. There are two options for sale:
- Pipes made of steel sheet with a welded seam.
- Seamless steel pipes.
It is clear that the second option is more preferable. It eliminates the possibility of damage to the product. Its cost is higher, but the service life is longer. It is not necessary to describe the characteristics of pipes made of stainless steel. They are identical to copper products. Thin-walled steel pipes will be a good alternative to copper elements.
Now you know which pipes to choose, what to give preference to during installation heating system. The main thing in this matter is not to save. It is better to fork out and save yourself from possible problems than to patch up problem areas every time and get nervous, complaining about your shortsightedness.
To answer the question, which pipes for heating are best used when installing an apartment heating system or country house, you need to substantively study their main characteristics, calculate the necessary parameters, and also imagine what type of heating system we are talking about. That is, you need to know:
- Type of heating system - with forced or gravity circulation;
- Mounting method - on the walls or inside them;
- Variety - a complex system or a simplified one;
- The system pressure to be calculated;
- Calculation temperature regime work.
The choice of pipes must be made using the data on the above points, based on the characteristics various kinds products by performing a calculation to determine the diameter of the pipes and other parameters.
The cost of the pipe itself in the system is only up to 20% of the total estimate, but the reliability of the entire system will depend on how correctly the choice of components is made.
So, what components are usually used when installing the heating system of an apartment or a country house:
- Steel, including galvanized;
- Copper;
- Stainless steel;
- Polypropylene or PVC;
- metal-plastic;
Installation of a heating system using steel pipes
Steel is a reliable and durable material, resistant to high temperatures and mechanical damage, can be used not only in an apartment and country house, but in a production room where the risk of mechanical damage is high. In addition, the use of such products makes it possible to use different diameters, unlike PVC pipes. Due to the low linear expansion, it allows the installation of the heating system without the use of compensators. The range provides great opportunities in the choice of diameter.
Country houses also have disadvantages:
- The main one is the complexity of installation, which involves the use of a welding machine and the appropriate qualifications to work with it;
- In this case, it is necessary to carry out the installation before the start of finishing work in the room in order to avoid damage to the finish;
- Experts advise not to use components made of "ferrous" metals for internal installation due to their susceptibility to corrosion. In this case, stainless or galvanized materials can be used.
For example, for a floor-standing boiler, usually used in a country house, with gravity circulation, a system of metal pipes would be preferable. Since the calculation of the ratio of price and diameter shows that this particular application of steel will be optimal. The cost of a metal-plastic, PVC or copper pipe with a diameter of 1.5 inches will be many times higher than a similar steel one.
In the case of using a wall-mounted boiler with a copper heat exchanger and forced circulation, steel pipes for heating are inappropriate. This is due to low aesthetics, as well as due to clogging of the thin heat exchanger with initial corrosion products.
If we compare the price of galvanized and stainless products with the same diameter, then the cost of ordinary steel on the market is acceptable.
As the calculation shows, it is advantageous to use steel products in places where increased strength and a large diameter are in demand. Their use in heating systems with gravity circulation and replacement of worn pipes in an apartment or a country house will be optimal (in case of replacement, it is better to use galvanized pipes).
Copper pipes - expensive, but effective
Copper products of various diameters are perfect for both a country house and an apartment due to the presence of such useful properties, how:
- Leadership in reliability and durability;
- Resistant to high temperatures;
- They are quite flexible;
- The internal surfaces are absolutely not subject to corrosion, which explains the phenomenal wear resistance of 100 years or more. In addition, this property gives the right not to calculate the diameter reduction, since this does not happen. It should be noted that PVC products have the same property.
Stainless steel in the heating system - high quality and adequate cost
Stainless corrugated pipes for heating, especially those with a large diameter, are convenient to use instead of radiators.
Stainless steel components are now the main competitors of copper in terms of cost and quality. "Stainless steel" has good thermal conductivity and has increased wear resistance.
Manufacturers offer several types of such products of various diameters.
Welded pipes are made by rolling with subsequent welding. They are often used, but they are less reliable than their seamless counterpart, which, having the same diameter, sells for more.
Similar stainless steel products, in addition to diameter, differ in wall thickness.
Thick-walled, taking into account the large weight, it is better not to use, especially in the heating system of a country house, in order to avoid increasing the load on the walls.
The installation of such components can only be entrusted to a qualified specialist who has the appropriate equipment, who can correctly calculate the necessary parameters and perform the installation according to the calculations.
Polypropylene pipes
The most economical option when installing a heating system will be the use of polypropylene, pvc and other polymer components. In our market, products with different diameters are represented by Rehau and Calde.
The following arguments are in favor of polypropylene:
- Light weight allows you to reduce the load on the walls, which is essential, especially for a country house;
- The smooth inner surfaces of the pipes do not allow lime scale and corrosion products to impair the functionality of the heating system and allow it to remain operational for a long period of time;
- Wear resistance - the calculation of the service life of such materials shows that they are able to function normally up to 50 years. Especially if these are pipes from Calde or Rehau;
- Polypropylene products are resistant to low temperatures, which in emergency cases will protect the system from "defrosting".
Polymer pipes for heating a country house or apartment and accessories for them are shown in the photo below:
In terms of the cost of high-quality polypropylene heating pipes, Calde products look best. But I must say that in addition to Calde, there are domestic producers.
Polypropylene and PVC products also received negative reviews:
- Such elements are not flexible enough, which forces the use of additional fittings on turns;
- Difficulty in repair - leakage will require a complete replacement;
- Low heat resistance - strong temperature changes wear out the product;
- As the calculation shows, the operating temperature for this material should not exceed 70 degrees;
- For the installation of a system of polypropylene pipes, a special apparatus is required;
- Low rigidity, which leads to sagging when the temperature drops.
In any case, if you decide to use polypropylene flexible pipes for installing a heating system for an apartment or a country house, it is better to purchase obviously high-quality material from Rehau or Kelde.
The issues of organizing a heating system in a private house or in a city apartment have always been classified as the most complex and large-scale. Literally everything is important here, and any seemingly trifle can play its role. And one of the basic requirements, if we do not take into account the installation of heat energy generation, is high-quality materials and components for the installation of the entire system.
Even 20 ÷ 25 years ago, the owners of housing did not have a special alternative - they had to use exclusively for water circuits metal pipes different diameter. This imposed a lot of inconvenience and technological difficulties - from the heavy weight of pipes and problems with organizing their transportation, to the need for special equipment for their installation and, accordingly, the ability to use it correctly, the availability of skills in working with metal. It is a different matter now - metal products have been replaced by plastic pipes for heating.
This opened up very broad horizons for independent work home craftsmen. No, of course, in order for the heating system to turn out to be of high quality, stable skills are necessary, but learning how to install any plastic pipes is much easier than performing, for example, electric arc welding. Even thread cutting steel pipe and its reliable “packing” is a much more time-consuming process than, for example, installing a compression fitting or soldering polypropylene. The equipment is not so expensive, it is easy to rent it for “ridiculous” money, and with many types of pipes, a set of wrenches is generally enough.
The article will consider several varieties of polymer pipes - from their specifications, advantages and disadvantages, to the basic technological methods of installation in the heating system.
What requirements must be met when choosing pipes for heating
The assortment of ruby products is extremely large. They differ from each other in the base material of manufacture, diameters and wall thicknesses, the absence or presence of any reinforcement, physical characteristics - flexibility, degree of linear expansion, the ability to give and maintain a given shape, resistance to temperature and pressure loads, to ultraviolet radiation and others. parameters - up to color design.
The variety of plastic pipes is very large
However, one must understand that heating is a very specific system in which all elements experience extreme or close to them loads. And any pipe, simply for reasons of economy or ease of installation, will not work here.
- Plastic pipes for heating must freely withstand the high temperatures of the coolant circulating through them. Although in modern systems the upper heating limit usually does not exceed 70 - 80 degrees, yet the "reserve" laid down by the technologists should not be less 95 °C. With such heating, the labor should not deform, lose its strength qualities (plastic should not “float” from elevated temperature).
- Where there are high temperatures, there is always high pressure. This means that plastic pipes for heating must be guaranteed possible baric loads in the system, including sharp jumps and water hammer. This is especially important for home wiring of central heating systems, where the owners cannot control the level of the supplied coolant pressure in any way.
- Pipes must have a smooth inner surface, which will not accumulate deposits of salts or scale, and which will not create increased hydraulic resistance for coolant circulation.
- Plastic pipes for heating should have the lowest possible coefficient of linear thermal expansion. Otherwise, they will simply either sag when heated, or vice versa, unnecessary internal stresses when the temperature drops.
- One of the main advantages of high-quality polymers is inertness, not susceptible to corrosion or chemical decomposition. This is especially important if not ordinary water, but certain chemical compositions are used as a coolant.
- The polymer itself does not oxidize, but it can pass oxygen from the air into the coolant. And this is very likely to eventually lead to corrosive processes on the metal surfaces of boilers, control, shut-off, mounting fittings. Modern technologies allow you to successfully deal with this phenomenon - pipes for heating can be equipped with special "oxygen barriers".
- Pipes must be durable - heating is always installed for a very long time, and the operational resources of the pipe should not be lower than that of other elements of the system.
- Not all residents will be pleased with the constant sound of water running under pressure. Therefore, another requirement for heating pipes is their "low noise". The smooth inner surface of the channel should ensure smooth, without turbulence, movement of the liquid, and the material of the walls should effectively muffle possible sounds without resonating.
- And, of course, since a significant part of the heating system is usually in plain sight, pipes with their appearance should not introduce a “destructive effect” into the interior of the premises. In other words, they should be, if not beautiful, then at least very neat.
Modern technologies for the manufacture of plastics and composite materials make it possible to create products that almost completely meet all these requirements, to a greater or lesser extent. Today, various plastic pipes are widely used in the arrangement of heating systems, but polypropylene and polyethylene pipes, in various combinations and designs, are most widely used.
Polypropylene pipes
General concepts about the material
Polypropylene (PP) has been used as a raw material for pipe products for a long time. But it was only possible to use it at high temperatures and high pressure by creating modern modifications of this material.
So, all polypropylene products are distinguished by a pronounced chemical inertness - they can be used for pumping even very aggressive compounds. But according to the criteria of strength and thermal stability quite large "scatter" is possible:
- The initial wide popularity of this material was brought by homopolypropylene (there are different designations - for example, "type 1" or PP-H). PP-N pipes are high-strength, chemically inert, but they cannot withstand high temperatures. Their typical use is cold water supply, drainage systems, ventilation ducts, technological production complexes not related to the heating of liquids.
- Type 2 polypropylene, or a block copolymer of polypropylene (PP-2 or PP-B) - while retaining all the advantages of its predecessor, has more significant ability to withstand thermal stress. However, extreme temperatures, in the region of 80 - 90 ° FROM he will not endure even a short time. The scope of PP-B pipes is, in principle, the same as that of PP-N. It can be used in supply systems hot water with a limited heating threshold, in "warm floor" systems, where temperatures should not exceed 45 - 50 ° C.
- Significantly expanded the scope of polypropylene, the development of technology for creating so-called "random copolymer» . During the synthesis of this material, fragments of an ethylene molecule are introduced into the molecular chain of propylene, which dramatically changes the performance of products for the better.
Type 3 static polypropylene, PP-3, PP-R, or PPRC, is just the right material for pipes subjected to both compression and thermal stress. Not at all without worsening the chemical inertness and environmental friendliness of the material, such modernization dramatically increases elasticity, viscosity, resistance to elevated temperatures.
PP-R polypropylene has become one of the main materials for the production of pipes for various purposes. It is used as in pure form, and creating multilayer structures.
Pipes can vary in color - they can be white, grayish with varying degrees of saturation, green or in shades of blue, etc. By the way, this does not at all speak of their particular features; rather, the desire of some leading manufacturers to somehow highlight their products plays a role here.
An exception may be black pipes - this color is usually given to products that are highly resistant to ultraviolet rays. And yet - pipes for sewerage or drainage systems are usually given an orange color. One when installing heating, neither black nor orange pipes will meet, so consider them No there is no need.
The longitudinal colored strip on the pipe will say more. Everything is simple and clear here - the blue strip indicates the possibility of using it exclusively in the cold water supply system, and the red one indicates the increased heat resistance of the pipe. By the way, the stripes are not applied to all products - it is better to pay attention to the markings.
The fact is that PP-R pipes differ in several ways. The first, of course, what attention is drawn to is the outer diameter and wall thickness of the pipe. The standard diameters that are used when creating home heating systems are 16, 20, 25, 32, 40, with a maximum of 50 mm. As a rule, larger pipes for use in the heating system of a private house are simply not needed - there are no such significant volumes of coolant pumping. However, the diameter itself is a parameter that does not say much, and it cannot be considered in isolation from the indicator of the type of pipe, in the name of which the value of the nominal working pressure is indicated hydraulic system. In total, four such types have been identified - from РN -10 to РN -25. Features and scope - in the attached table:
Type of polypropylene pipe | Rated working pressure | Scope of use of pipes | |
---|---|---|---|
MPa | technical atmospheres (kgf/cm²) | ||
PN 10 | 1.0 | 10.197 | Cold water supply, as an exception - heated floors with a heating level of up to 45 ° C |
PN 16 | 1.6 | 16.32 | Cold and hot water supply with water temperature up to 60°С |
PN 20 | 2.0 | 20.394 | Cold and hot water supply, heating systems with a low level of coolant pressure (autonomous systems) |
PN 25 | 2.5 | 25.49 | Hot water supply and all types of heating systems, including central ones (with heat carrier temperature up to 95 °C) |
The scope of application is not indicated from scratch - this is the result of research, during which not only the limiting capabilities of pipes were studied, but also the duration of their trouble-free operation in such extreme conditions.
Temperature (°C) | Service life (years) | Pipe type | |||
---|---|---|---|---|---|
PN 10 | PN 16 | PN 20 | PN 25 | ||
Permissible overpressure, 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 | 8.67 | 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 can be seen from the above data, only pipes of the PN-20 type (with reservations) are suitable for use in heating systems, but the optimal solution is PN-25.
Advantages and disadvantages of polypropylene pipes
The use of polypropylene pipes has a number of advantages:
- The lightness of the material itself predetermines the absence of great difficulties in transportation, delivery of pipes to the place of work - neither specialized equipment nor lifting mechanisms are boring.
- Polypropylene belongs to thermoplastic polymers and is easy to weld. Installation of PP-R pipes , although and requires special equipment, but is still very uncomplicated. Anyone can learn the necessary skills literally "on the go". And the equipment can usually be rented for a very reasonable price for the right time. The process itself from boiling is very fast, and installation of the entire system should not take much time.
- The material is completely harmless - it does not change the chemical composition of the coolant circulating in the circuit.
- The stabilizers included in the PP-R allow the plastic to perfectly tolerate temperature and compression surges. Moreover, even the freezing of water in the pipe will not end with a rupture of its wall - the necessary elasticity of polypropylene will help.
- Exactly what is needed for the heating system is the low thermal conductivity of pipes, especially compared to metal ones. This means that minimizing absolutely unnecessary losses during the transfer of thermal energy from the boiler to heat exchange devices (radiators or convectors). So, depending on the length of the contours, the savings can be serious - from 10 to 20%.
- Polypropylene perfectly dampens all noises or vibrations created by the flow of the coolant through the pipes.
- The material can be safely classified as the most economical - at the cost of the pipes themselves and all the necessary components, from fittings to stop valves. And the range of various elements for mounting the most complex structures is very wide.
- With the purchase of high-quality material and competent installation work, it will be possible to calculate the service life of the system in tens of years.
- The pipe itself does not require any additional measures to decorate it - a smooth, pleasant color allows you to fit the open sections of the pipelines of the heating system into almost any interior.
Do such pipes have serious drawbacks? Unfortunately yes :
- The first of them, and probably even the most important, which is often completely unnecessarily ignored - polypropylene does not become an obstacle to the practically free penetration of oxygen molecules from the air into the flowing coolant.
Perhaps it will seem absolutely insignificant a minus in water supply or sewage systems, but only for some types of radiators or boilers, this property becomes a very serious drawback - this causes active corrosion of metal components (steel, cast iron, aluminum). In addition, some systems are very picky about the chemical composition of the coolant, and "extra" oxygen plus oxidation products can disrupt it. In addition, the penetration of oxygen is an impetus for the development colonies of aerobic bacteria are capable of significantly narrowing the gap of t rub by the products of their vital activity, thereby violating the parameters of the normal circulation of the coolant.
Manufacturers are struggling with this drawback by installing special chemical-organic or metal anti-oxygen barriers. As an example, the figure reproduces a diagram of one of their types of pipe. This, by the way, will help us along the way to deal with the symbol of multilayer pipes (shown by the red ellipse and arrow ).
In this case, the role of the oxygen barrier is performed by a layer of aluminum foil, usually overlap welded so that there are no uncovered areas.
On the outer surface of the pipe - designation: PP-RCT/ AL / PPR. This is the layered structure:
1 - modified inner layer random copolymer polypropylene with increased thermostatic qualities - PP-RCT.
2 - aluminum layer - AL.
3 - the outer layer of their PPR polypropylene.
- The second serious drawback of polypropylene pipes is a rather large linear thermal expansion. It is clear that for heating systems, where they operate with very large temperature amplitudes, this becomes extremely important.
The elimination of this drawback is achieved in exactly the same way - by laying an additional layer.
This may be a layer of fiberglass (in the diagrams and in the legend, it has the abbreviation FG or FR). However, this solution is one-sided, as it helps to cope with thermal expansion, but does not allow to deal with oxygen diffusion. For hot water systems - quite an acceptable option, but for heating - clearly not enough.
And you don’t need to invent anything special - a high-quality aluminum layer makes it possible to solve both problems at once.
To add clarity to this issue, here is a table that summarizes the data on thermal expansion and oxygen diffusion for different types of single-layer and multilayer pipes.
(It should be noted that the table shows the parameters and polyethylene pipes, the features of which will be discussed in the corresponding section of the publication.)
Types of polymer pipes | Accepted designation | Thermal expansion coefficient, 10 ¯⁴/°C | Oxygen diffusion indicators, mg/m² × day |
---|---|---|---|
Single layer pipes | |||
XLPE pipes | PEX | 2 | 650 |
Polypropylene pipes | PPR | 1.8 | 900 |
Multilayer composite pipes | |||
XLPE pipes with barrier layer | PEX-EVON-PE | 2 | 0.32 |
Polypropylene pipes reinforced with fiberglass | PPR-FG-PPR | 0.35 | 900 |
Polypropylene pipes reinforced with aluminum | PPR-Al-PPR | 0.26 | 0 |
Pipes from metal-plastic from polyethylene of the increased heat resistance | PERT-Al-PERT | 0.25 | 0 |
If someone finds the language of tabular numbers not entirely clear, then he can look at the diagram - the same parameters are more clearly indicated there.
A brief summary of the qualities of polypropylene pipes:
- From the point of view of ease of installation, durability of use in extreme conditions, in terms of solidity of the structure, pipes with fiberglass reinforcement have an advantage. For example, there are simply no cases in history of such a pipe exfoliating. Almost all pipes of the PN-20 class are made using this technology. It is quite possible to use them in a heating system if the efficiency of the system does not imply a serious dependence on the level of oxygen diffusion.
- Only the PN-25 pipe, which is produced exclusively with aluminum reinforcement, will help to completely get rid of all the shortcomings of polypropylene. This layer is both a reliable oxygen barrier and greatly reduces the linear expansion of the pipe. The aluminum layer reaches a thickness of 0.4 to 0.7 mm in them, which also makes it possible to reliably, if necessary, hold the curvilinear configuration given to the pipe.
Video: what polypropylene pipes are intended for what
Installation of polypropylene pipes
The editing technology will be given in an overview, only so that the reader has a firm opinion that this is a technological operation that is quite accessible to him, and there is nothing to be afraid of.
We also do not address the issues of planning installation and carrying out calculations - these problems are considered in the relevant publications of our portal,. Here - only the "basics" of welding.
For installation, it will be necessary to purchase or rent special equipment for some time. Very often, everything is collected in a single case, for maximum convenience. In the photo you can see the complete set of such a set:
On the “suitcase” is the welding machine itself (soldering iron), with a power cord, power and indication keys, and a temperature controller. The “xiphoid” cast body of the heating element is clearly visible, with three holes in this case, allowing you to place three working heating pairs at the same time different diameter- coupling and mandrel. These pairs are clearly visible below, right next to the case. They are fastened with a screw connection - both the screws themselves and the hex key must be included.
Very good if included there will be special scissors for cutting the desired sections of pipes.
The tape measure is useful for marking, the level is for the correct placement of pipes horizontally or vertically during installation, they are not in their “regular” place.
Finally, gloves, which, by the way, many do not use in vain, since getting a burn on the skin of the hands when working with a soldering iron is as easy as shelling pears.
If PN-20 or PN-25 pipes with an aluminum reinforcing layer are used, then, most likely, another special tool will be required - a shaver that allows you to remove the foil layer to the required depth of penetration before soldering. The tool can be manual or in the form of a nozzle on a drill (screwdriver).
Shaver - manual and nozzle on a drill
The installation process itself is carried out in the following order (for example, one seam):
On the heating plane of the welding machine (soldering iron), heating pairs - couplings and mandrels of those diameters that will be involved in the installation work. For example, having three possible positions, you can prepare pairs of 32, 25 and 20 mm.
The soldering iron stops on a support and joins in an electric network for heating. The desired heating temperature is set on the thermostat. When working with polypropylene pipes, the optimum temperature is about 260 ° FROM. Sometimes temperature regulators are marked with marks corresponding to the diameters of the pipes being welded.
While the welding machine is warming up (it will take 10 - 15 minutes), you need to prepare the parts for connection. A pair of mating elements is always a pipe section (even if it's the shortest one) and some profile detail - from the simplest couplings to taps, valves, adapters, tees, bends, etc. The mating parts of the parts should not have places of severe contamination, oiling - otherwise, cleaning and degreasing should be carried out, for example, with an alcohol wipe.
The pipe must be cut strictly perpendicular to the axis - this is easy to do with special scissors. No burrs should remain.
Since we are considering pipes in the context of a heating system, this will most likely be a reinforced version. So, there are two options for preparatory work.
If the pipe type is PP-R / AL / PP-R (in one or another specific variation), then the end of the pipe to be welded must be processed with a shaver. The pipe is inserted into the cutting part of the device. Turning the shaver, either manually or with a drill, will allow the installed blades to remove the top layer of PP-R and the layer of aluminum foil, otherwise the penetration with mutual diffusion and copolymerization of polypropylene will not work.
A properly configured shaver will remove the desired layer to the required depth and length of the pipe section - here special control is not required.
When using a pipe with fiberglass reinforcement shaver is not required. Just from the end of the pipe, a transverse mark of the penetration depth is made with a marker. The specific value depends on the diameter of the pipe.
(There is another option - when the pipe has aluminum reinforcement, but this layer is placed deep and does not interfere with welding. A typical example is the DIZAYN OXY-PLUS pipe, when working with which the stripping process becomes unnecessary. When buying pipes, this point must be clarified immediately ).
Below is a table that shows the main parameters for welding with polypropylene pipes.
pipe Ø (mm) | Depth of heating during welding (mm) | Heating time (s) | Time from joining parts to complete polymerization of the weld (min) |
---|---|---|---|
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 | 24h30 | 24 | 6 |
75 | 26 ÷ 32 | 30 | 6 |
90 | 29 ÷ 35 | 40 | 8 |
The soldering iron has already warmed up - this should be signaled by an indicator light, which, like you iron, turns off when the desired temperature is reached. Matching parts are put on the heating pair from both sides - the pipe section is pushed up to the mark or until the end of the section processed by the shaver into the coupling, and the figured part is put on with its hole on the mandrel until it stops. It is necessary to try to carry out this operation, if possible, almost simultaneously, so that the required uniform heating is ensured.
Then, the warm-up time is counted - it is indicated in the table. Immediately after its expiration, both parts are simultaneously removed from the heating elements.
Further, without any pause, the parts are combined - the heated section of the pipe is inserted into the hole of the curly element with the necessary force. Depth - to the mark made earlier or, which, in principle, is the same - to the full depth of the heated area. When combining, you need to make sure that it passes coaxially, without distortions. It is not allowed to rotate the parts around the axis when they are combined - for an accurate fit, it is better to indicate in advance, before the start of heating, the necessary position of their relative position with the corresponding risks.
The connected parts are held with a slight effort in this position for about 20 seconds. The node must then completely polymerize– the time required for this is also indicated in the table.
If for some reason the weld turned out to be unsuccessful, then the only way to correct the situation is to immediately cut out the defective or even doubtful section in order to weld in a new one, taking into account the mistake made. At the installation stage, perform the following operation not difficult at all, but when the system is launched, there may be serious difficulties in carrying out repairs.
So, welding a polypropylene pipe is not such a complicated process that it cannot be learned in the most short term. This is another big plus of this type of pipe.
Video: lesson on welding (soldering) polypropylene pipes
Polyethylene pipes
The second extensive group of polymer pipes for heating (quite often structurally intersecting with the first, polypropylene) are products based on seemingly familiar polyethylene.
Let's make a reservation right away - we will certainly not talk about those varieties of polyethylene that are used for the manufacture of a wide variety of household products - with all the advantages of this plastic, it is still not stable enough, especially in high-temperature conditions. Ordinary polyethylene "technical" pipes will not be considered either, since they will not find a place in heating either. We will talk about modified types of polyethylene.
Cross-linked polyethylene
If we consider the molecular model of conventional polyethylene, we can not fail to notice the pronounced linear structure of "chains", which are practically not connected by interatomic bonds to each other. But if you try to create such connections artificially, or, as they say, “sew” linear molecules with jumpers, create not a flat, but their spatial structure.
This problem has been solved by chemists. At the same time, polyethylene did not lose at all in its positive qualities, and at the same time acquired a whole "bouquet" of remarkable performance characteristics. So, the material turned out to be plastic, elastic, its strength properties to break increased. In addition, polyethylene "gained memory" - a unique property to strive to return to the once given shape after deformation from certain types of loads. Agree that it is for pipe products that this quality is generally irreplaceable.
The higher the degree of crosslinking (the greater the number of intermolecular bonds) - the better the material is obtained. Cross-linked polyethylene has the general marking PEX, and it is obtained by various technological methods.
- One of the highest degrees of cross-linking is obtained by processing the initial polyethylene raw material with peroxide (the number of cross-links reaches 85%). Such material is marked PEX-a, it is probably the highest quality in its line, but also the most expensive due to the complexity of the technological production process.
Pipes made on the basis of PEX-a, of course, of the appropriate class, are quite suitable for use in heating systems.
- A simpler and cheaper option for crosslinking is exposure to water vapor in the course of obtaining the desired polymer. The result is PEX-b polyethylene. Unfortunately, this technology did not lead to a qualitative improvement in the resulting product - the percentage of crosslinking is lower, no more than 65%, but even this is not the main thing. The synthesis itself is practically not amenable to fine regulation, and it is almost impossible to guarantee the uniform declared characteristics of the material. Moreover, even in the PEX-b pipes already installed in the system, it is impossible to completely stop the process of further crosslinking - it continues all the time, although, of course, at a very slow pace. However, the pipe changes over time physical properties, becomes more rigid, gives a certain shrinkage. As a result, connections on fittings sometimes leak and require tightening, and multilayer pipes using PEX-b do not differ in structural stability (they can delaminate). Characteristically, European standards do not allow the use of pipes based on PEX-b in systems with high temperatures and fluid pressure, including heating willows.
It is possible to use PEX-b in heating only, probably, in a single-layer version, in a “warm floor” system, where the heating does not exceed 45 degrees, and the circuit is solid, without any joints, that is, it begins and ends directly on the collector - here it will be possible to inspect fitting connections and carry out their regular tightening as necessary.
- PEX-c cross-linked polyethylene is produced by processing raw materials with a directed electron flow. The method is quite inexpensive, productive, and allows obtaining material of acceptable quality, although inferior to more advanced analogues. PEX-c pipes may well be used in plumbing systems, but their resource, apparently, will not be enough for heating.
There are some other specific crosslinking technologies, but they have not received much distribution.
High temperature resistant polyethylene RE-RT
Research on its modification was not limited to the production of cross-linked polyethylene PEX. Literally a revolutionary innovation was the technology that allows you to control the spatial construction of polymer molecules, and makes it possible to immediately put the necessary performance qualities into the created material.
The molecular structure of PE-RT is even more complex
One of the products of this technology was polyethylene PE-RT (an abbreviation of the long English name, meaning polyethylene with increased heat resistance).
The special structure of the molecular lattice with very frequent branched bonds gives the plastic a number of additional useful qualities. Pipes based on PE-RT are excellent for heating systems - as if they were created for them:
- The durability of pipes is about 40 - 50 years.
- The material, unlike PEX, has pronounced thermoplastic properties, that is, it can be welded. And this dramatically improves the performance and safety of heating systems.
- The material is not afraid of even prolonged frosts, and after thawing the pipes it fully retains its qualities.
- The maintainability of systems with PE-RT pipes is much higher than with any other.
Most likely, over time, the pipes PE-RT push, and even completely replace PEX. If we take a comparison of multilayer pipes practically identical in structural structure, then the gain is clearly in favor of PE-RT:
Types of pipes based on polyethylene
Pipes without metal reinforcement
They have already been briefly mentioned. This is the case with both PEX and PE-RT - a good option for laying underfloor heating contours. The elasticity of such pipes is high, therefore, it allows the contour loops to be located close enough. Pipes are easy to lay, and their large length in bays allows you to lay a contour of any allowable length without any joints.
And again, one can note a clear gain in terms of performance characteristics PE-RT polyethylene. The table below shows the main parameters of such pipes using the example of the two most common diameters - 16 and 20 mm.
Technical and operational indicators | PERT 16×2mm | PERT 20 × 2 mm |
---|---|---|
Pipe volume (liters / linear m) | 0.113 | 0.201 |
Weight (kg/rm) | 0,07 | 0.127 |
Minimum bending radius - 5d (mm) | 60 | 100 |
Temperature (°C) | 20 | 20 |
Working pressure (bar) | 20 | 20 |
Service life (years) | more than 50 | more than 50 |
Temperature (°C) | 75 | 75 |
Working pressure (bar) | 10 | 10 |
Service life (years) | more than 50 | more than 50 |
Temperature (°C) | 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 factor max at t=95°С (1/°С), PE-RT pipe | 1.8 E-4 | 8.2 E-5 |
Thermal conductivity coefficient (W/K m) | 0.41 | |
Internal surface roughness (µm) | 0.125 (Class 10) | |
Estimated material strength (MPa) | 6.3 |
The pipe can be completely uniform throughout its thickness. However, as we remember, this is not entirely good for heating systems in terms of free oxygen diffusion. To eliminate this drawback, a special technology is used - the placement of a special EVON oxygen barrier. it name is also an abbreviation, indicating the chemical composition of the interlayer: it is successfully used both in pipes made of cross-linked polyethylene PEX, and in the case of PE-RT.
Metal-plastic pipes based on polyethylene
What is commonly called "metal-plastic" in the vast majority of cases is a multilayer pipe, in which certain types of cross-linked or heat-resistant polyethylene are used with an aluminum layer between them. The options here can be different: PEX - AL - PEX, PE-RT - AL - PE-RT, PE-RT - AL - PEX, or even using an outer polypropylene layer - PE-RT - AL - PPR.
"Metaloplast" can also be in different versions
As we remember, the aluminum layer, as in the case of polypropylene, dramatically improves the mechanical characteristics of the pipe, reduces its linear expansion when heated, and becomes an insurmountable obstacle to oxygen diffusion.
With metal-plastic pipes, when purchasing them, special care is needed. Even with the highest quality material, it is impossible to fully guarantee the absence of delaminations between the polymer and aluminum - all even in a significant difference in the exponential thermal conductivity and thermal expansion. In inexpensive pipes of low quality (and, alas, there are an extremely large number of such pipes on spontaneous markets), on the contrary, stratification is guaranteed with a probability close to 100%. BUT this is the straight path to a serious accident with very unpleasant consequences, especially in the heating system, and the worst thing is if the pipe breaks through the underfloor heating circuit under the concrete screed.
Therefore, no “penny savings” - only high-quality pipes from well-known manufacturers should be purchased for the heating system, the originality of which the seller must confirm with the appropriate certificate.
Installation of pipes based on polyethylene
Installation of polyethylene-based pipes can be carried out in several ways, depending on the configuration of a particular product with certain connecting fittings. So, the main methods are connection using compression fittings, press fittings or special welded fittings.
Some well-known companies produce kitsmounting connectors, which suitable exclusively for pipes of our own production. They may have specific installation features that are somewhat different from others. Nonetheless , basic principles yet remain the same.
1. At home, without the use of special tools, it is most convenient to install metal-plastic pipes on compression threaded fittings.
The installation process is simple:
- The pipe is cut with special scissors, strictly perpendicular to the axis. You should get a smooth, neat edge.
- The fitting is disassembled. A compression nut is put on the cut section of the pipe (threaded towards the joint), and then a split brass ring.
- It is advisable to roll the inner surface of the pipe at the junction with the fitting a little outward, expand it, for example, using a manual calibrator.
The order of work is something like this:
- The fitting sleeve is first put on the pipe to be connected.
- And the processed cut off end of a pipe the special expander is entered. With its help, the body of the pipe expands so that it can fit freely enough on the fitting pipe. Almost immediately, the "memory" of polyethylene is turned on, and it begins to return to its original position. This process is always activated when the temperature rises.
- After the pipe is put on per fitting, per fitting sleeve is pressed in. It requires a large and directed effort, so you can not do without a special tool - a presser. Manual or with some kind of drive.
- After the sleeve is in place, the process of assembling the assembly is completed.
This process is very well shown in the video.
Video: installation of polyethylene pipes with a press fitting
By the way, the options may be somewhat different - for example, a fixed compression sleeve is already installed on the fitting. After installing the pipe, both are crimped from the outside with a special tool.
Video: several mounting options metal-plastic pipes
And finally, we can mention the welded joint using a special welding machine for PE-RT pipes. The technology for producing welds differs little from that used for PP-R - they simply use different heating and polymerization parameters. Truth, in a similar way connections are not suitable for all types of PE-RT pipes - this must be clarified immediately - when buying them.