Polypropylene pipes for heating

Polypropylene pipes for heating the technical characteristics of which can vary among themselves, in the modern market are presented in a very wide range. Their popularity is high, and the tendency to its constant growth is traced. Such a demand is explained by the convenience of installation and the breadth of the possibility of their use: depending on the type they are used from the usual installation of the water pipe to the creation of heating circuits. Of course, they do not have the express flexibility of metal-plastic pipes, but if necessary, they can be given a smooth bend.

There are many varieties of polypropylene pipes, and each of them has its own sphere of application. In order to understand which type is most suitable for the heating circuit, it is necessary to become more familiar with their structure and technical characteristics.

Criteria for selecting polypropylene pipes for heating

The heating system will last as long as possible without interruption and repair, iffor it will find the right accessories to meet a number of specific requirements.

are suitable. All elements and components of the heating system for quite even regular operation are experiencing quite serious loads. This is, of course, very high temperature drops, pressure jumps, which are aggravated also by aggressive chemical influences of a poor-quality coolant, especially if the home( apartment) system is connected to central heating.

Polypropylene pipes - the material is rather ambiguous, and is presented in sales in a variety of types, differing between the wall thickness, the presence or absence of reinforcement, the quality of the material, resistance to temperature and pressure, ultraviolet, linear expansion characteristics. Therefore, in order to update the heating circuit, it is necessary to know very precisely what qualities the pipe material must possess.

For installation in a heating system it is necessary to choose polypropylene pipes that meet the following basic characteristics:

• Since the standard temperature of the heating medium in the central heating system is usually 70 ÷ 75 degrees, but sometimes it can be even larger, the pipes for it need to be chosen with such a calculation,so that their heat resistance has a certain margin, up to 90 ÷ 95 degrees of heating. Pipes should not be deformed, bend, "float" during high-temperature heating, their thermal expansion should not go beyond certain limits.

heating circuit

• In addition to elevated temperatures, uncontrolled pressure jumps and water hammering occur in the central heating system. Especially they are probable in the period of test measures before the start of the heating season. Hence the conclusion - the pipes must withstand the high pressure of the bar.
• The material from which the pipes are made must be inert to corrosive substances that may be present in the coolant composition. Walls should not be corroded, and polypropylene fully has these advantages, so it is excellent for heating systems.
• In order to achieve a normal circulation of the coolant along the contour, without the creation of mud plugs in it, the internal surfaces of the pipes must have an ideal smoothness and keep it in its original state for as long as possible. Unlike metal pipes, polypropylene will not be corroded by any of the known types of corrosion, and on their inner walls there will be unevenness, in which dirt and lime scale usually accumulate.
• The coefficient of thermal expansion of the pipe material for the heating system should be minimal, otherwise, when heated on long straight sections of the pipe, they will begin to sag.
• The service life of the pipes must be at least not less than the service life for which other elements of the heating system are designed.
• It would seem that an unimportant characteristic, but it should also be borne in mind. When moving the coolant through the pipes, if they have an uneven internal surface, noise can be created, seemingly unnoticeable at first, but gradually causing irritation. Polypropylene is able to provide a virtually noiseless circulation of the liquid, in contrast to the metal, since in the polymer pipes there are no strong vortices, and hence resonant sounds.
• The contour of polypropylene pipes is always more aesthetic than metallic, and does not require periodic staining.

Timely polypropylene pipes are produced using modern technologies for the production of plastic and composite materials, and additional equipment of some varieties by reinforcement makes them ideally suited for heating systems. Thus, polypropylene pipes for systems in contact with hot water are made in multi-layered versions with a reinforcing layer, which significantly reduces the temperature expansion and makes the walls more durable.

Since the duration of accident-free operation and the quality of polypropylene pipes for heating and hot water systems directly depends on the composition of the materials from which they are produced, one should consider their various options.

Varieties of polypropylene pipes

Polypropylene( accepted international designation - PP has been used for a long time for the production of pipes as a base material, however, only the development of modern technologies allowed to obtain such products that can be used for hot water supply and heating systems. Polypropylene has a marked inertness to the chemical effect of a possible liquid coolant environment, however, in terms of heat resistance and strength, various types can

For example, pipes from this material are divided into three main types, having their designations:

• PP-N - is the first type of polypropylene pipes inert to chemical effects, but unstableto high temperatures, so they are designed for cold water, sewerage, drainage systems, ventilation and for other applications where higher temperatures are not expected. Very often this kind of pipe is prevalent for industrial process lines, since it has a high resistance to increased internal pressure.

• PP-B is the second type of polypropylene pipes, which has all the same advantages of PP-H, but besides it has the ability to withstand low-amplitude temperature loads. Therefore, they can be installed on separate main sections of the "warm floor" systems. And also in the circuits of hot water supply, provided that the water or coolant does not heat above 50 degrees.

However, the main scope of PP-B is different. Most often, such pipes go to sewage systems, since the material from which they are made, has a sufficient degree of toughness and heat resistance for this region.

• PPRC, PPR or PP-3 are fully suitable for heating systems. This is the most perfect type of pipe used in hot water and heating systems, that is, where temperatures can exceed 50 degrees and is presentprobability of increased compression loads. Increased heat resistance and mechanical strength is achieved due to special production technologies, in which ethylene molecules are introduced into the molecular lattice of propylene during the synthesis.

PPR - pipes, which are most widely used in domestic conditions, since they have a pronounced resistance to internal pressure and to temperature differences.

Polypropylene pipes( PPR) used in domestic conditions, in turn, are divided into several types, depending on the resistance to pressure loads: PN-25;PN-20;PN-16;PN-10.Their main characteristics are given in the table:

Type of polypropylene pipes	Nominal working pressure	Scope of use of pipes
MPa	technical atmospheres( kgf / s²)
PN -10	1	10.21	Provision for a "warm floor" contour,not higher than 45 ˚С, or cold water supply. This type of pipe is designed for pressure in the system no more than 1 MPa. It is the most affordable due to its rather low performance.
PN -16	1.6	16.32	Cold and hot water supply with a temperature of not more than 60 ° C and a pressure of not more than 1.6 MPa.
PN -20	2	20.40	Cold and hot water supply in an autonomous system with a low level of pressure and no water hammer. The temperature of the coolant for this type of product should not exceed 80 ° C, and the pressure should be 2.0 MPa.
PN-25	2.5	25.49	Hot water supply and heating with a coolant up to 90 ÷ 95 ° C, including in the central heating system. The pressure for which they are calculated is 2.5 MPa.

Each type of pipe is produced in a fairly wide range of diameters, internal and external: on which the thickness of the

Outer diameter, mm	PN -10	PN -16	PN -20	PN -25
Internal Ø, mm	Thickness of the wall, mm	Internal Ø, mm	Thickness of the wall, mm	Internal Ø, mm	thickness walls mm	inner Ø, mm	thickness walls 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	-	-

Naturally, the diameters and wall thicknesses directly affect the durability of pipes to the temperatures andpressure, which, in principle, predeterminesand the duration of their possible operation under various conditions:

Coolant temperature ˚С	Service life, years	Pipe type
PN-10	PN-16	PN -20	PN -25
Permissible pressure rise( 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

The data presented in tablesThis is the result of long test runs of pipes in different conditions, whiche even theoretically can arise in the process of their operation, so it is worthwhile to take them into service in the process of selecting the necessary material.

Polypropylene pipes can be of different colors, but when choosing them, one should not pay special attention to them( perhaps only from an aesthetic point of view), since the exterior color does not determine the characteristics of the products and does not affect their quality.

Some red or blue stripes can be applied to the surface of some pipes - it serves as a certain signaling device for a specific type of purpose. So, the blue color is applied to the pipes of cold water supply, and red indicates the ability of products to withstand elevated temperatures in the DHW system or the heating circuit.

. In addition to the color strips, pipes are marked with lettering, which indicates the characteristics and purpose of them for installation in certain water supply or heating systems, and it is also necessary to pay attention to it. The value of the marking values ​​corresponds to the information given in the tables.

As can be seen from the presented characteristics, the PN-20 products are ideally suited for the heating system, but PN-25 pipes, which have a strong resistance to high temperatures and pressure, even with a good margin, will be an ideal option.

Reinforced Polypropylene Pipes

Due to the fact that pure polypropylene itself does not show strong resistance to elevated temperatures and significantly expands upon heating, reinforcement is used for pipes used in systems where contact with hot water is intended. To strengthen these products, several materials are used - aluminum foil, fiberglass or composite mixture.

• The reinforcement of the polypropylene pipe can be done with a layer of one-piece or perforated aluminum foil having a thickness of 0.1-0.7 mm, which is placed between the layers of the base material and fixed with a layer of special glue.

The characteristics of the adhesive used in the production of pipes will also depend on their longevity, since in poor quality products, walls can break down, where moisture inevitably penetrates, which will negatively affect the overall strength of the pipe, significantly reducing the life of the pipe.

In addition, the pipes differ in the area of ​​the reinforcement layer.

So, the aluminum layer can be located in the immediate vicinity of the outer surface of the pipe or be closer to the middle of the thickness of the walls.

wall In addition to the fact that the aluminum layer significantly reduces the temperature expansion of polypropylene pipes, it contributes to protecting the coolant from ingress of oxygen into it from the ambient air, since the polymer itself does not possess such qualities.

wall. If there are pipes with no such protection in the autonomous heating system, corrosion processes on the metal elements of the circuit, including in the boiler structure, can be activated with a constant penetration of oxygen into the coolant( diffusion effect).Oxygen also contributes to the appearance of aerobic bacteria, which eventually multiply, clogging the internal space of pipes with the products of vital activity, which will significantly slow the circulation of the coolant.

Many manufacturers of polypropylene pipes, trying to get rid of these drawbacks, use metal or chemico-organic interlayers.

If there are aluminum layers in the pipes, PP-RCT-AL-PPR marking is placed on their surface, indicating that several materials are used in this product:

-PP-RCT is a random copolymer or modified polypropylene with high thermostaticqualities;

- AL - reinforcing aluminum layer;

- PPR - outer polypropylene layer;

- adhesive layers.

• Another option for reinforcement, which suppresses thermal linear expansion, is glass fiber, which is laid between two layers of polypropylene. However, this reinforcing material is not capable of protecting the coolant from the penetration of oxygen into it.

If the pipe is reinforced with a layer of fiberglass, the letter designation PPR-GF-PPR and PPR-FR-PPR is set on its surface. As can be seen from the marking, a pipe of this type consists of three layers - outer and inner propylene( PPR) and medium-fiberglass( GF).Fiberglass can be located only in the middle between the layers of polypropylene.

The same can be said for the composite material, which consists of fiberglass mixed with propylene. If you look at the internal structure of the pipe in a section, you can see that its walls are monolithic, only differ in color. The effect of their wholeness is created due to reliable adhesion of the layers, which prevents their separation.

The table below provides information on the specific features of single-layer and multilayer polypropylene pipes in terms of temperature linear expansion and the degree of oxygen diffusion:

Types of polypropylene pipes	Designation	Coefficient of thermal expansion, m × 10⁻⁴ / ˚С	Oxygen diffusion indices, mg /m² per day
Single-layer pipes:
PPR	1.8	900
Multilayer pipes:
Polypropylene, fiber reinforced.	PPR-GF-PPR	0.35	900
Polypropylene, reinforced with aluminum.	PPR-AL-PPR	0.26	0

From what has been said above, one can draw a logical conclusion that the best option for the heating system will be PN-25 pipes made using a reinforcing layer of a solid aluminum sheet. Such a design has a minimal linear expansion and maximum laziness for oxygen diffusion.

Installation of pipes from polypropylene

To perform the heating circuit installation, not only polypropylene tubes of the optimum type are required, but also various connecting elements - corners, tees, bushings, holders, adapters, threaded fittings and other parts. All these accessories are purchased simultaneously with the pipes and are selected to them by the external diameter, according to the developed circuit of the heating circuit.

In addition, a special welding machine with the attachments necessary to mount pipes of different diameters is required. Such a device is expensive, so if you do not plan on doing such a job in the future, you can rent it for a few days.

This photo shows a set consisting of a soldering iron and all necessary attachments and additional elements. On the heating xiphon part, small holes are clearly visible for the installation of working elements - mandrel and couplings, with which the pieces of pipes and connecting parts will be heated before bonding. A set of tools often also includes special scissors( cutter), which will help to cope with cutting pipes of different diameters without problems.

In addition to this kit, you need to prepare measuring instruments - roulette, building level, brand. You may need a building hair dryer, with which, if necessary, it will be possible to give the individual sections of the pipe a smooth curvilinear shape.

For work it is necessary to have at hand protective protective gloves, because when working with a soldering iron or a hair dryer that heats up to very high temperatures, you can get a very serious burn.

To prepare for welding of pipes with aluminum reinforcement, a special tool - shaver - will be needed. It can be in the form of a nozzle on a screwdriver or manual.

To understand how the installation process takes place, you need to look at it in a concrete example step by step.

• The contour is installed in accordance with a pre-drawn up scheme-drawing.

In accordance with the drawing and conducted "on-site" test measurements, with the help of special scissors cut lengths of the required length. In addition, all connecting elements - cranes, bends, tees and other curly details - are prepared and laid out. If necessary, the areas that will heat up, for better adhesion of the material, it is necessary to degrease - rub it with alcohol.

• On both sides of the working part of the soldering device pairs of heating elements are installed - couplings and mandrels, having dimensions corresponding to the diameter of the selected pipes. In the soldering iron, as a rule, holes are provided for heating two or even three pairs of elements, so if pipes of different diameters are to be used in the circuit, appropriate nozzles can be immediately installed.

• Further, the soldering iron is switched on for heating, the required temperature is set on its thermostat - the optimal temperature for polypropylene is 260 ÷ 265 degrees. Some devices are already equipped with regulators, which indicate the temperature for welding pipes made of certain materials.
• When the unit reaches the desired temperature, the heating indicator lamp should turn off.
• If the circuit is to be mounted from a pipe PN-2о and PN-25, which has aluminum reinforcement, the edges must be stripped from the upper thin layer of polypropylene and foil.

shaver. The stripping is carried out at a distance from the edge, which will be equal to the depth of the penetration. Usually the shaver is designed for this mounting length. The pipe is inserted into the cutting part of the shaver, then it turns, gradually removing the layer of polypropylene and aluminum. As a result, a cleaned area is obtained, which exactly corresponds to the assembly length for soldering, and the required diameter.

For pipes that do not have reinforcement, or reinforced with fiberglass or composite composition, such stripping is not required. On them the marker should only note the depth of the penetration.

The table below shows the basic parameters for welding polypropylene pipes:

Outer pipe diameter in mm	Welding depth of the pipe during welding, mm	Warm-up time of mating parts, seconds	Time from joining of elements to full polymerization of the joint, 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

• It is recommended to immediately determine exactly the relative position of the parts. To facilitate further work, it is possible to put a corresponding longitudinal mark by the marker - at the final assembly it will only be necessary to combine the marks.
• When the soldering iron is completely warmed up, the prepared pipe section is inserted into the sleeve( to the depth of the stripped area or to the marked depth of the penetration), and one of the connecting parts is put on the mandrel up to the stop. Elements should be warmed evenly.

Therefore, the time specified in the table above is always noted. At the end of this time, the elements are quickly removed from the soldering iron and perfectly perfectly interconnected - the pipe is inserted into the connecting part to the depth of preheating and held in this position for approximately 15-20 seconds, until the junction of the junction.

• The joints can not be rotated relative to each other, as they must be copolymerized rather than screwed into each other.
• Sometimes, the contour is mounted on blocks that are assembled on a table, and then connected together at the installation site of the heating system.

• heating circuit. The work needs to be done very carefully, since if the connection does not work out, it can be corrected only by cutting out the pipe section and installing a new node. Therefore, before starting the installation of the circuit, it is worth to practice, "to fill the hand" - for this it is recommended to purchase a few extra couplings or corners.
• If any junction is suspect, then it's better not to risk, but to re-do it - the fittings are inexpensive, and with an incompletely mounted system, the replacement of one node of complexities should not be presented.

The main reasons to choose the polypropylene pipes

for the heating circuit. The reasons, which are essentially the advantages of polypropylene pipes, are as follows:

• Polypropylene has a low mass, which simplifies its delivery to the work site and the installation itself - no need for anyspecial appliances or equipment.
• With the necessary tools, polypropylene pipes are easy to assemble, and welding techniques can be learned very quickly. .
• The material of production is absolutely harmless for residential premises, since it does not change its chemical composition even under strong heating and does not emit toxic fumes into the air.
• Thanks to the stabilizers included in the composition of polypropylene, the pipes are resistant to water hammer and thermal loads, and even freezing of water inside without breaking.
• Smooth inner walls of the pipes contribute to a uniform, without turbulence and no noise, circulation of the coolant.
• Both pipes and accessories to them are distinguished by low price. And a wide range of accessories allows you to install a circuit of any complexity.

• . A circuit made of quality pipes, with proper installation, will last at least 20 -30 years.
• The aesthetic look of the pipes makes it possible not to spoil the interior, and the contour itself usually does not require painting or additional decoration.

So, polypropylene pipes with reinforcing aluminum layer are perfect for heating circuits of autonomous and central system. In addition, the installation of this material is simple enough and feasible even for people who have no experience in such work. After several trainings, the assembly of individual components, the assembly process and the entire circuit can be done on its own.

Video: useful information on the choice of polypropylene pipes and accessories