Entering the points of sale of plumbing and sewer systems, the person feels a little confused. The range, number of manufacturers and varieties of pipes are simply amazing. But if you came in with a specific purpose to choose a high-quality pipe for installing a warm floor, the choice of materials under consideration is narrowed to a dozen. We recommend paying special attention to the five-layer cross-linked polyethylene pipe - PEX Evoh.

PEX Evoh is a specially designed type of pipes, the intended purpose of which is the installation of cooling and heating water supply variations. Metal-plastic, metal and polymer pipes made of various plastics are not able to withstand high temperatures and are subject to deformation.

The main modifications and characteristics of pipes made of cross-linked polyethylene

With the advent of the central heating system and underfloor heating in particular, there was a need for a super-strong, flexible and resistant to high temperature pipe. After all, modern heating systems maintain a stable temperature of the heated surface - about 50-70°C. This type of pipe is a combination of quality, elementary installation at a minimum market value.

Manufacturer Valtec

The Valtec PEX Evoh pipe is a molecularly cross-linked polyethylene. Pipe joints made of polyethylene have low thermal stability and are therefore not suitable for use in heating systems. Molecularly cross-linked polyethylene has cross-linked bonds, which makes it more durable, and most importantly, maximum resistant to temperatures not exceeding 90 degrees. Polyethylene crosslinking at the molecular level is based on 3 main techniques:

1. proxy method. Organic peroxides + hydroperoxides, and the maximum crosslinking is about 75%.
2. The technique of molecular silane crosslinking occurs with the help of organosilanides. The minimum degree of crosslinking is 65%.
3. The method of radiation crosslinking is performed using a stream of charged particles, with a degree of crosslinking of the order of 60%.

Cross-linking of Valtec pipelines occurs using the silane method, which is guaranteed to indicate its strength (about 70%). Also, quite important is the fact that this degree of firmware allows you to "remember" and restore the original shape of the product, which means that kinks in this pipe are not terrible. The process of restoring the original shape occurs due to internal stress resulting from heating.

The PEX Evoh cross-linked polyethylene pipe is very easy to operate and install. Without resorting to preheating, the required drainage section can be bent within a radius of five own diameters. If you need a bend of a smaller radius, preheating is required with a building hair dryer (without material breaks). When purchasing Valtec, you can be sure that you will be able to dock them with other similar components, since metal-polymer pipelines have a standard wall thickness of 16 x 2.0, which makes it possible to use much-needed fittings and couplings by pre-ordering them freely on the Rosterm website .

Pipe polymer PEX with an anti-diffusion layer from the manufacturer Valtec has a three-layer design, and the anti-diffusion layer itself is outside. Multiple studies and tests have shown that the PEX-glue-EVOH pipe is more practical and reliable than the five-layer (PEX-glue-EVOH-glue-PEX).

The fact that a three-layer plumbing system is many times more reliable than a five-layer one is explained quite simply: in a three-layer, a PEX ball is applied in one single and continuous layer, which is not the case in a five-layer one, since the same ball is interrupted by a layer of EVOH and glue. In connection with the above factors with a five-layer water pipe, there is a risk of delamination of the balls, which is possible with forced heating. There is an opinion that the EVOH layer can crumble and wear off, however, many experts refute this judgment, since the PEX layer is softer and more susceptible to external physical influences.

Underfloor heating system

The system requires separate consideration. floor heating, because in recent years, it is very popular and relevant. A lot of positive feedback about the "warm floor" piping system speaks for itself. Previously used copper tubes went into oblivion, and the PEX Evoh floor heating pipe took one of the leading roles in construction and installation work.

The anti-diffusion layer in pipes of this type is located in the core of the product, which allows you not to worry about its possible violations, and makes it possible to cover the pipeline concrete screed, marble or tiles. In the "warm floor" system, the following qualities should be noted:

1. The heat in the room is distributed evenly over the entire floor area;
2. For him, it makes no difference on what source of energy to work - it can be a liquid fuel boiler, and central heating;
3. Not harmful to human health;
4. Saving energy, which is formed due to optimal heat transfer;
5. The installed thermostat makes all processes automated;
6. Easy to install without the need for bulky equipment.

For an underfloor heating system, there is no limit in terms of installation volumes - it can be either a small coil in the bathroom or warehouse with great square footage. To give you an idea of ​​how the installation of a warm floor looks like, we have specially prepared several photos.

A system similar to underfloor heating is increasingly being used to heat open surfaces - concert venues, sidewalks, shopping pavilions, etc. A constant positive temperature (0 - +5) will help you forget about sputum, dirt and slush. Ease of use and no need to hire an additional worker (for example, to clear snow) fully compensate for all the costs of both the material itself and its installation.

The VALTEC trademark offers PEX-EVOH polyethylene pipes made of PE-Xb cross-linked polyethylene. Outside, the anti-diffusion layer EVOH with a thickness of 50 microns is applied to the pipe. The outer and inner layers of the pipe are bonded together with Plexar PX 3216 flexible adhesive.

The VALTEC PEX-EVOH 16mm pipe is primarily intended for cold, hot water supply and heating systems. Operation classes - 1, 2, 4, 5 according to GOST 32415-2013. The design of the pipe includes an outer protective layer of ethylene vinylol (EVOH), which prevents the diffusion of oxygen into the coolant.

VALTEC PEX-EVOH

The material of VALTEC PEX-EVOH polyethylene pipes is cross-linked polyethylene (PE-X). It is obtained from ordinary high-density polyethylene by special processing, which ensures the formation of bulk bonds between linear polymer molecules. This gives the products thermal stability, mechanical strength, high elasticity, increased resistance to ultraviolet radiation. In addition, pipes made of cross-linked polyethylene are characterized by a low roughness of the inner surface, are not subject to corrosion, do not emit harmful substances into the flow in the operating temperature range, are electrically inert, do not spread (on the contrary, they absorb) noise and vibrations, withstand liquid freezing without destruction. The estimated service life of such products is 50 years. Polyethylene pipes VALTEC PEX-EVOH are designed for engineering systems, including - for a warm floor, and technological installations with working temperature up to 80 °С (at working pressure 6 bar). For a short time, the transported medium can be heated up to 95 °C. The design of the pipes includes a layer of polyvinylethylene (EVOH), which prevents the diffusion of oxygen into the coolant

Estimated service life - 50 years. Delivery form - pieces 200 m long in bays. The cost of the pipe is indicated for 1 running meter.

Technical characteristics of the Valtec polyethylene pipe:

Manufacturer: Valtec
Producing country: Italy
Pipe material type: Cross-linked polyethylene
Type of cross-linked polyethylene: Silane (PE-Xb)
Scope of the pipe: For hot, cold water supply and heating systems,
Pipe section: Round
Outside diameter: 16.0(mm)
Inner diameter: 12.0(mm)
Minimum operating temperature: 0.0(deg.)
Maximum operating temperature: 90.0(deg.)
Maximum short-term admissible temperature: 95.0(deg.)
Breaking pressure: 45.0(bar)
Bending radius using a tool (pipe bender, conductor): 80.0(mm)
Weight 1 l.m. pipes: 88.0(d)
Coefficient of thermal conductivity: 0.38(W/(m*K))
Guarantee period: 7 years)

Logistics: Supplied in 200m coils.

Buy Valtek pipe for underfloor heating in Moscow in the company Teplodoma-msk

Dear readers! Since the publication of this article, changes may have occurred in the assortment of our company, the practice of using equipment, and regulatory documents. The information offered to you is useful, but is for informational purposes only.

To date, the share of Russian construction is growing low temperature systems heating. Modern boilers and heating appliances are able to fully heat rooms with a coolant temperature of up to 80 ° C. In addition, floor heating systems have become widespread in recent years. The temperature and pressure of the coolant in these systems allow the use of simpler and cheaper materials. That is why on Russian market Now there is a great demand for pipelines made of cross-linked polyethylene. This type of pipeline combines reliability when used in low-temperature heating systems, ease of installation and low cost.

Cross-linked polyethylene pipeline, or, as it is called, PEX-pipe, is an almost monolithic structure, the main material of which is molecularly cross-linked polyethylene. Ordinary polyethylene consists of long hydrocarbon molecules that are not connected to each other in any way and are not suitable for use as the main material for heating pipelines due to low thermal stability. Molecularly cross-linked polyethylene has cross-links between chains of hydrocarbon molecules, and therefore this material has higher strength and rigidity, and most importantly, higher resistance to temperature effects.

If we talk about metal-polymer pipelines, then under this term today a fairly extensive class of polymer pipelines is accepted, the main difference of which from conventional pipelines is the presence of a reinforcing layer of metal, usually aluminum, foil between the inner and outer polymer layers. In this case, the same material as in PEX pipes, namely cross-linked polyethylene, can be used as the material of the inner and outer layers. Other materials can also be used - polyethylene (PE, PE-HD), polyethylene of increased temperature resistance (PE-RT), polypropylene (PP-R), etc.

While the characteristics of metal-polymer pipes often depend on the properties of the materials used and the quality of the adhesive layer, the characteristics of PEX pipes, as a rule, depend on the degree of cross-linking of polyethylene, the thickness of the pipeline wall and the method of applying oxygen barrier layers.

Polyethylene crosslinking determines the strength and thermal characteristics of the pipeline. First of all, cross-linking makes it possible to achieve long-term resistance to high temperature and pressure (increases the limit of logarithmically proportional relaxation). Polyethylene crosslinking can occur different ways and to varying degrees. There are three main industrial methods for crosslinking polyethylene:

• peroxide method (PEX-a) is chemical method crosslinking of polyethylene and consists in crosslinking with organic peroxides and hydroperoxides. The pipeline obtained by this method has a degree of crosslinking of about 75%;
• the silane method (PEX-b) is also chemical. When cross-linking this method, organosilanides are used. The minimum crosslinking factor by this method is limited to 65%;
• radiation crosslinking (PEX-c) is performed using a stream of charged particles. The crosslinking factor is about 60%.

VALTEC PEX-EVOH pipelines are hollow technological cycle cross-linking by the silane method (PEX-b) using modern equipment, which ensures uniform cross-linking of polyethylene with a cross-linking degree of 68–70%.

The method of sewing pipelines practically does not affect physical properties finished pipeline. The properties of the pipeline are mainly affected by the degree of crosslinking. With an increase in the degree of crosslinking, strength, heat resistance, resistance to aggressive media and ultraviolet rays increase. However, along with an increase in the degree of crosslinking, the brittleness increases and the flexibility of the resulting pipeline decreases. If you bring the degree of crosslinking of polyethylene to 100%, then in its properties it will be similar to glass.

Also, the crosslinking of polyethylene gives the resulting pipeline a “shape memory effect”. Its essence lies in the fact that the previously deformed pipeline after heating restores its original shape. This property manifests itself due to the fact that during bending and deformation, the molecularly-bound regions are compressed or stretched. After heating, internal stresses arise in places of deformation, due to which the original shape is restored ( rice. one).

Fracture and restoration of the shape after heating to 100 °C of the VALTEC PEX-EVOH pipe (crosslinking method - PEX-b)

Fracture and restoration of shape after heating up to 100 ° C pipes made of PEX-a with anti-diffusion layer

Fracture and restoration of the shape after heating to 100 ° C of a PEX-c pipe without an anti-diffusion layer (uncolored cross-linked polyethylene becomes transparent at high temperature)

Rice. 1. Restoring the shape of pipelines after deformation

On the rice. one the restoration of pipelines with various methods of stitching after a break is shown. With all methods of stitching, the pipelines restored their original shape. On pipelines coated with an anti-diffusion layer, folds formed after restoration. In these places, the anti-diffusion layer has delaminated from the PEX layer. This defect practically does not affect the characteristics of the pipeline, since the main bearing capacity of the pipeline is determined by the PEX layer, which has completely recovered. Slight delamination of the anti-diffusion layer slightly increases the oxygen permeability of the pipeline. A pipeline without an anti-diffusion layer becomes transparent after heating. This effect is inherent in any uncolored cross-linked polyethylene.

The shape memory effect is very useful in editing. If during the installation of the pipeline a fracture, squeezing or other deformation is formed, then it is easily eliminated by heating the pipeline to a temperature of 100-120 ° C. In addition, when connecting a PEX pipeline to a fitting, deformations also occur in the grooves of the fitting ( rice. 2). When the coolant is supplied and the pipeline is heated, restoring forces arise in these places. Due to these efforts, the pipeline fits the fitting more tightly, which increases the reliability of the connection.

Rice. 2. PEX pipe connection VALTEC with press fitting

Rice. 3. Bending a PEX pipe with a diameter of 20 mm to a radius of 100 mm

The choice of the polyethylene cross-link degree range of 68–70% for VALTEC PEX-EVOH pipelines is due to the optimal ratio of the strength characteristics of the pipeline and its flexibility. For example, a VALTEC PEX pipe can be manually room temperature bend to a radius equal to five pipe diameters ( rice. 3), and when using a pipe bender or conductor - to a radius equal to three diameters. A pipeline with more than 70% crosslinking will have a manual bend radius of at least seven diameters. Greater bending of the pipeline with such a degree of crosslinking can only be achieved using a building hair dryer.

Select Valtec 20 (2.0)

Price: 0 65 65 RUB

Main Diameter: 16

Nominal pressure: PN 10

Item Type: Pipe

Brand: VALTEC

Manufacturer_: Valtek S.r.l.

Country of origin: CHINA

Warranty period: 7 years

Products webpage: www.valtec.ru

Weight: 0.093 kg

VALTEC PEX-EVOH PIPES

Today, the share of low-temperature heating systems in Russian construction is growing. Modern boilers and heating devices are able to fully heat rooms with a coolant temperature of up to 80 ° C. In addition, floor heating systems have become widespread in recent years. The temperature and pressure of the coolant in these systems allow the use of simpler and cheaper materials. That is why in the Russian market there is now a great demand for pipelines made of cross-linked polyethylene. This type of pipeline combines reliability when used in low-temperature heating systems, ease of installation and low cost.

Cross-linked polyethylene pipeline, or, as it is called, PEX-pipe, is an almost monolithic structure, the main material of which is molecularly cross-linked polyethylene. Ordinary polyethylene consists of long hydrocarbon molecules that are not connected to each other in any way and are not suitable for use as the main material for heating pipelines due to low thermal stability. Molecularly cross-linked polyethylene has cross-links between chains of hydrocarbon molecules, and therefore this material has higher strength and rigidity and, most importantly, higher resistance to temperature effects.

If we talk about metal-polymer pipelines, then under this term today a fairly extensive class of polymer pipelines is accepted, the main difference of which from conventional pipelines is the presence of a reinforcing layer of metal, usually aluminum, foil between the inner and outer polymer layers. In this case, the same material as in PEX pipes, namely cross-linked polyethylene, can be used as the material of the inner and outer layers. Other materials can also be used - polyethylene (PE, PE-HD), polyethylene of increased temperature resistance (PE-RT), polypropylene (PP-R), etc.

While the characteristics of metal-polymer pipes often depend on the properties of the materials used and the quality of the adhesive layer, the characteristics of PEX pipes, as a rule, depend on the degree of cross-linking of polyethylene, the thickness of the pipeline wall and the method of applying oxygen barrier layers.

Polyethylene crosslinking determines the strength and thermal characteristics of the pipeline. First of all, cross-linking makes it possible to achieve long-term resistance to high temperature and pressure (increases the limit of logarithmically proportional relaxation). Crosslinking of polyethylene can occur in various ways and to varying degrees. There are three main industrial methods for crosslinking polyethylene:

• The peroxide method (PEX-a) is a chemical method for crosslinking polyethylene and consists of crosslinking with organic peroxides and hydroperoxides. The pipeline obtained by this method has a degree of crosslinking of about 75%;
• the silane method (PEX-b) is also chemical. When cross-linking this method, organosilanides are used. The minimum crosslinking factor by this method is limited to 65%;
• radiation crosslinking (PEX-c) is performed using a stream of charged particles. The crosslinking factor is about 60%.

Pipelines VALTEC PEX-EVOH undergo a complete technological cycle of cross-linking by the silane method (PEX-b) on modern equipment, due to which uniform cross-linking of polyethylene with a cross-linking degree of 68-70% is ensured.

The method of sewing pipelines practically does not affect the physical properties of the finished pipeline. The properties of the pipeline are mainly affected by the degree of crosslinking. With an increase in the degree of crosslinking, strength, heat resistance, resistance to aggressive media and ultraviolet rays increase. However, along with an increase in the degree of crosslinking, the brittleness increases and the flexibility of the resulting pipeline decreases. If you bring the degree of crosslinking of polyethylene to 100%, then in its properties it will be similar to glass.

Also, the crosslinking of polyethylene gives the resulting pipeline a “shape memory effect”. Its essence lies in the fact that the previously deformed pipeline after heating restores its original shape. This property manifests itself due to the fact that during bending and deformation, the molecularly-bound regions are compressed or stretched. After heating, internal stresses arise in places of deformation, due to which the original shape is restored ( rice. one).

Fracture and restoration of the shape after heating to 100 ° C of the VALTEC PEX-EVOH pipe (crosslinking method - PEX-b)

Fracture and restoration of shape after heating up to 100 ° C pipes made of PEX-a with anti-diffusion layer

Fracture and restoration of the shape after heating to 100 ° C of a PEX-c pipe without an anti-diffusion layer (uncolored cross-linked polyethylene becomes transparent at high temperature)

Rice. 1. Restoring the shape of pipelines after deformation

On the rice. one the restoration of pipelines with various methods of stitching after a break is shown. With all methods of stitching, the pipelines restored their original shape. On pipelines coated with an anti-diffusion layer, folds formed after restoration. In these places, the anti-diffusion layer has delaminated from the PEX layer. This defect practically does not affect the characteristics of the pipeline, since the main bearing capacity of the pipeline is determined by the PEX layer, which has completely recovered. Slight delamination of the anti-diffusion layer slightly increases the oxygen permeability of the pipeline. A pipeline without an anti-diffusion layer becomes transparent after heating. This effect is inherent in any uncolored cross-linked polyethylene.

The shape memory effect is very useful in editing. If during the installation of the pipeline a fracture, squeezing or other deformation is formed, then it is easily eliminated by heating the pipeline to a temperature of 100-120 ° C. In addition, when connecting a PEX pipeline to a fitting, deformations also occur in the grooves of the fitting ( rice. 2). When the coolant is supplied and the pipeline is heated, restoring forces arise in these places. Due to these efforts, the pipeline fits the fitting more tightly, which increases the reliability of the connection.

Rice. 2. PEX pipe connection VALTEC with press fitting

Rice. 3. Bending a PEX pipe with a diameter of 20 mm to a radius of 100 mm

The choice of the range of polyethylene crosslinking degree of 68-70% for VALTEC PEX-EVOH pipelines is due to the optimal ratio of the strength characteristics of the pipeline and its flexibility. For example, a VALTEC PEX pipe can be manually bent at room temperature to a radius equal to five pipe diameters ( rice. 3), and when using a pipe bender or conductor - to a radius equal to three diameters. A pipeline with more than 70% crosslinking will have a manual bend radius of at least seven diameters. Greater bending of the pipeline with such a degree of crosslinking can only be achieved using a building hair dryer.

It should be noted that PEX pipelines are quite elastic and difficult to bend. After a "cold" bend, the pipe segment will take its original shape. However, if the pipeline is preheated and allowed to cool in a fixed position, it will retain this position. When the pipeline is reheated, the segment will return to its original state due to the shape memory effect.

The shape memory effect should not be confused with elastic deformation. In the first case, the initial shape is taken only after heating, and in the second, immediately after the removal of the deforming forces and only within the limits of elastic deformation (without kinks).

VALEC PEX-EVOH pipelines can be embedded in building construction both with and without casing. When embedding PEX-EVOH pipes in a casing, it is possible to replace small sections of pipelines without opening the floor.

The wall thickness of the pipeline directly affects the maximum coolant pressure that the pipeline can withstand. VALTEC PEX-EVOH pipes are manufactured with the same wall thickness as metal-polymer pipelines - 16 x 2.0, 20 x 2.0 mm. This allows you to use for the installation of the pipeline standard press fittings, produced for metal-polymer pipelines.

The disadvantage of PEX material is that it is oxygen permeable. Water in pipelines without protection from oxygen becomes saturated with oxygen after a certain time, which can lead to corrosion of the system elements. To reduce the oxygen permeability of PEX, a thin layer of polyvinylethylene (EVOH) is used. The PEX base layer and the EVOH layer are glued together. It should be noted that the EVOH layer does not completely prevent oxygen emission, but only reduces oxygen permeability to a value of 0.05-0.1 g/m3 day, which is acceptable for heating systems.

In the VALTEC PEX-EVOH pipe, the anti-diffusion layer is made on the outside, i.e. the pipe has a three-layer structure: PEX-adhesive-EVOH. There are also five-layer (PEX-adhesive-EVOH-adhesive-PEX) pipes on the market (rice. 4).

Rice. 4. Design of five- and three-layerPEX- pipes with anti-diffusion layer

This design is designed to prevent damage to the EVOH layer. However, tests have shown that a three-layer pipe (with an EVOH layer on the outside) is more reliable than a five-layer one. The increased strength of the three-layer pipe is due to the fact that the PEX layer is monolithic over the entire cross section of the pipe, in contrast to the five-layer pipe, in which the working PEX layer is interrupted by the EVOH layer and glue, which breaks the internal cross-linking intermolecular polyethylene bonds. Also, with this design, it is possible to bundle the pipe when it is overheated by a building hair dryer during bending.

The notion that the outer layer of EVOH in a three-layer construction is subject to abrasion is erroneous. The hardness of the EVOH layer is significantly higher than that of the PEX layer, so damage to the outer layer is unlikely if handled properly.

Pipelines made of cross-linked polyethylene are recommended for use in the construction of low-temperature heating systems. The use of PEX piping for high temperature heating systems is not prohibited. But here it should be noted that in this case the permissible maximum pressure of the pipeline will be much lower than the passport one. In addition, the estimated service life of the pipeline in such a system will be reduced.

Pipeline manufacturers generally set the maximum operating temperature and pressure based on the service life of the pipeline - 50 years. With monolithic and hidden laying, the replacement of these pipelines can be carried out in conjunction with a major overhaul of the building or premises. More frequent replacement of monolithic pipelines will entail large financial costs for the alteration of building structures.

But the temperature of the coolant during the operation of the system is different. In summer and during the transitional period, the coolant temperature is lower than the calculated one. To assess the applicability of pipelines to a specific temperature regime in conditions of changing temperature of the coolant, the operating classes are determined by the standards. These classes show shares of influence different temperatures from only fifty summer term operation.

On the rice. 5 a graph is presented showing the duration of the influence of various temperatures on the pipeline in the fourth class of operation (low-temperature radiator heating)

Rice. 5

Therefore, when determining the type of pipeline, one should be guided by the permissible operating class of this pipeline, indicated in the pipe passport. PEX pipelines on the Russian market are suitable for service classes 1, 2, 3, 4 and XB.

Thus, due to its reliability and low cost, XLPE pipelines have become increasingly used in the construction of low-temperature heating systems and water supply systems.