VALTEC, VALTEC polymer PEX-b pipe, with anti-diffusion layer EVOH, 16 (2.0). EVOH oxygen barrier layer evoh barrier layer

Pipe made of cross-linked polyethylene with an outer diameter of 16 and a wall thickness of 2 mm. Designed for indoor cold and hot water supply systems, low-temperature (up to 80 °C) heating. Operating classes according to GOST 52134-2003 - 1, 2, 3, 4, ХВ. The pipe design includes a layer of polyvinylethylene (EVOH), which prevents the diffusion of oxygen into the coolant.
Installation of PEX-EVOH polyethylene pipes is carried out using VALTEC press fittings. Estimated service life is 50 years.

The material of VALTEC PEX-EVOH polyethylene pipes is cross-linked polyethylene (PE-X). It is obtained from ordinary polyethylene high density through 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, cross-linked polyethylene pipes are characterized by low internal surface roughness, are not subject to corrosion, do not emit harmful substances into the flow in the operating temperature range, are electrically inert, do not propagate (on the contrary, absorb) noise and vibration, and withstand freezing of liquids without destruction. The estimated service life of such products is 50 years. Polyethylene pipes VALTEC PEX-EVOH are intended for engineering systems, including for heated floors, and technological installations with operating temperature up to 80 °C (at operating pressure 6 bar). It is permissible to briefly heat the transported medium to 95 °C. The pipe design includes a layer of polyvinylethylene (EVOH), which prevents the diffusion of oxygen into the coolant. PEX-EVOH pipes are installed using VALTEC press fittings. The standard size indicates outside diameter and pipe wall thickness. Delivery form: 200 m coils.

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

Cross-linked polyethylene pipeline, or PEX pipe as it is called, is practically monolithic structure, the main material of which is molecular cross-linked polyethylene. Conventional polyethylene consists of long hydrocarbon molecules that are not connected to each other in any way and is not suitable for use as the main material for heating pipelines due to its low heat resistance. Molecular cross-linked polyethylene has cross-links between the chains of hydrocarbon molecules, and therefore this material has higher strength and rigidity and, most importantly, more high durability to temperature influences.

If we talk about metal polymer pipes pipelines, then this term today includes a fairly broad class of polymer pipelines, 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 layers of the polymer. 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 with 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-impermeable layers.

Cross-linking of polyethylene determines the strength and thermal characteristics 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). Cross-linking of polyethylene can occur different ways and to varying degrees. There are three main industrial way polyethylene cross-linking:

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

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

The method of joining pipelines has virtually no effect on physical properties finished pipeline. The properties of the pipeline are mainly affected by the degree of crosslinking. As the degree of crosslinking increases, strength, heat resistance, and resistance to aggressive environments and ultraviolet rays increase. However, along with an increase in the degree of cross-linking, the fragility of the resulting pipeline increases and the flexibility decreases. If you increase the degree of crosslinking of polyethylene to 100%, then its properties will be similar to glass.

Also, crosslinking polyethylene gives the resulting pipeline a “shape memory effect.” Its essence lies in the fact that a previously deformed pipeline, after heating, restores its original shape. This property manifests itself due to the fact that during bending and deformation, molecularly bonded areas are compressed or stretched. After heating, internal stresses arise in places of deformation, due to which the original shape is restored ( rice. 1).

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

Fracture and restoration of shape after heating to 100 °C a PEX-a pipe with an anti-diffusion layer

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

Rice. 1. Restoring the shape of pipelines after deformation

On rice. 1 the restoration of pipelines with various methods of stitching after a crease is shown. With all stitching methods, the pipelines regained their original shape. Wrinkles formed on pipelines coated with an anti-diffusion layer after restoration. In these areas, the anti-diffusion layer has peeled away from the PEX layer. This defect practically does not affect the characteristics of the pipeline, since the main bearing capacity The pipeline is identified by a layer of PEX that has been completely restored. A slight peeling of the anti-diffusion layer does not significantly increase the oxygen permeability of the pipeline. A pipeline without an anti-diffusion layer becomes transparent after heating. This effect inherent in any undyed cross-linked polyethylene.

The shape memory effect is very useful during installation. If a kink, compression or other deformation occurs during pipeline installation, it can be easily eliminated by heating the pipeline to a temperature of 100-120 °C. 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 forces, the pipeline fits the fitting more tightly, which increases the reliability of the connection.

Rice. 2. Connection of VALTEC PEX pipe 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 crosslinking degree range of 68-70% for VALTEC PEX-EVOH pipelines is due to the optimal balance between 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 jig - to a radius equal to three diameters. A pipeline with more than 70% stitching will have a manual bend radius of at least seven diameters. Greater bending of the pipeline with such a degree of cross-linking can only be achieved by using a construction hair dryer.

It should be noted that PEX pipelines are quite elastic and difficult to bend. After a “cold” bend, the pipe section will take its original shape. However, if you preheat the pipeline and allow it to cool in a fixed position, it will maintain this position. When the pipeline is reheated, the section 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 original shape is assumed only after heating, and in the second, immediately after removing the deforming forces and only within the limits of elastic deformation (without kinks).

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

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

The disadvantage of PEX material is that it is oxygen permeable. Water in pipelines without protection from oxygen through certain time is saturated with oxygen, which can lead to corrosion of 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 joined together with glue. It is worth noting that the EVOH layer does not completely prevent the emission of oxygen, but only reduces oxygen permeability to a value of 0.05-0.1 g/m 3 · 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-glue-EVOH-glue-PEX) pipes on the market ( rice. 4).

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

This design is designed to eliminate the possibility of damage to the EVOH layer. However, tests have shown that three-layer pipe(with an EVOH layer applied on the outside) is more reliable than a five-layer one. The increased strength of a 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 a five-layer pipe, in which the working layer of PEX is interrupted by a layer of EVOH and glue, due to which the internal transverse intermolecular bonds of polyethylene are interrupted. Also, with this design, delamination of the pipe is possible if it is overheated with a construction hairdryer during bending.

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

Pipelines made of cross-linked polyethylene are recommended for use when installing 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 rated pressure. In addition, the estimated service life of the pipeline in such a system will be reduced.

Pipeline manufacturers generally set a maximum operating temperature and pressure based on the service life of the pipeline - 50 years. When embedding and hidden gasket replacement of these pipelines can be done together with major repairs buildings or premises. More frequent replacement of embedded pipelines will entail large financial costs for alteration of building structures.

But the temperature of the coolant during system operation is different. In summer and during the transition period, the coolant temperature is lower than the calculated one. To assess the applicability of pipelines to a specific temperature conditions in conditions of changing coolant temperatures, standards define operating classes. These classes show the proportion of the influence of various temperatures from the entire fifty-year service life.

SP Slide pipes made of cross-linked polyethylene with a PEX-b/EVOH barrier layer are intended for use in radiator heating, water supply and water heated floor systems.

SP Slide pipes made of cross-linked polyethylene are produced at the Metzerplas plant (Israel).

SP Slide pipes made of cross-linked polyethylene with a PEX-b/EVOH barrier layer offer a number of advantages.

The EVOH barrier layer prevents oxygen from entering the piping system. Heating and water supply elements are not subject to corrosion. The inner layer of the pipes is abrasion resistant. Perfectly smooth inner surface walls does not contribute to the deposition of hardness salts, scale, scale, etc.

SP Slide pipes made of cross-linked polyethylene PEX-EVOH are environmentally friendly to use due to the absence of toxic and physiologically harmful emissions.

Also, SP Slide pipes made of cross-linked polyethylene PEX-EVOH are quiet in use, unlike metal ones.

The SP Slide PEX-EVOH pipe consists of three layers: cross-linked polyethylene, an outer anti-diffusion layer and an adhesive composition connecting them.

The structure of polyethylene is not uniform. It contains amorphous and “crystalline” zones. Cross-linking occurs most effectively in amorphous zones, starting at a temperature of +125°C.

Cross-linking also occurs in “crystalline” zones. When cooling, the crosslinking process continues in the finished pipes in air and accelerates in hot water. The minimum percentage of cross-linked molecules (crosslinks) specified by the standard for PEX-B pipe is 65%.

Pipes with a small percentage of cross-linking (less than 60%) are not recommended for installation in radiator heating systems.

Technical characteristics of SP Slide PEX-EVOH pipe

Outer diameter - 20 mm
Wall thickness - 2.0 mm
Coil length - 100/200 m
Scope of application: water heated floor
Service life - up to 50 years
Maximum operating temperature - 95 o C
Working pressure - 10 bar
Oxygen diffusion per day - 0 mg/m3
Emergency mode temperature, (max 1 hour) - 100 o C
Crosslinking degree - 65-85%
Thermal conductivity coefficient - 1.2-1.4x10 -4 W/m*K
Linear elongation at a temperature of 95 o C - 3% per 1 m
Thermal conductivity coefficient - 0.32 W/m*s
Volume 1 l.m. pipes - 0.201 l

Today there are many solutions for heating systems on the market, however, when choosing, it is not always possible to determine which specifications are decisive and what you need to pay attention to first.

In order for the system to work for a long time and without interruptions, you should carefully study not only its components, but also the material from which they are made. Metal components of heating systems ( steel radiators, sections of steel mains, etc.) have a tendency to wear out quickly, which can be prevented by an oxygen-tight barrier of pipes in the system.

Having installed a heating system, the buyer expects it to last 10, 20, 30 years. But after some time, rust usually forms on its elements, which leads to damage, heat loss and, as a result, disruption of the entire system. The corrosion process is based on chemical reaction oxidation: the steel from which the components of the system are made corrodes due to constant contact with oxygen dissolved in water. To prevent such contact, and, consequently, premature wear of the systems, a barrier is required in the coolant pipe that can provide maximum oxygen impermeability.

Often, to prevent the diffusion of oxygen into the coolant, pipes are reinforced with fiberglass. However, fiberglass is not capable of providing high oxygen resistance, which has been confirmed by numerous tests. According to the requirements of SP 60.13330.2012 “Heating, ventilation and air conditioning”, the oxygen permeability of heating systems made of polymer pipes should be no more than 0.1 g/(m3/day). The anti-diffusion layer EVOH (a copolymer of ethylene and vinyl alcohol) allows the contact of the coolant and oxygen to be minimized. It is this that will allow the pipes to last much longer and preserve them appearance and ensure uninterrupted operation of the entire system.

Select Valtec 20 (2.0)

Price: 0 65 65 RUB 2029-12-31 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 XL POLYETHYLENE PIPES

Today, the share of low-temperature heating systems in Russian construction is growing. Modern boilers and heating devices are capable of fully heating rooms with a coolant temperature of up to 80 °C. In addition, underfloor heating systems have become widespread recently. The temperature and pressure of the coolant in these systems allow the use of simpler and cheaper materials. That is why there is now a great demand in the Russian market 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.

A cross-linked polyethylene pipeline, or PEX pipe as it is called, is an almost monolithic structure, the main material of which is molecular cross-linked polyethylene. Conventional polyethylene consists of long hydrocarbon molecules that are not connected to each other in any way and is not suitable for use as the main material for heating pipelines due to its low heat resistance. Molecular 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 influences.

If we talk about metal-polymer pipelines, then this term today covers a fairly broad class of polymer pipelines, 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 layers of the polymer. 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 with increased temperature resistance (PE-RT), polypropylene (PP-R), etc.

Cross-linking of polyethylene 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 logarithmic-proportional relaxation). Cross-linking of polyethylene can occur in various ways and to varying degrees. There are three main industrial methods for cross-linking polyethylene:

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

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

The method of stitching pipelines has virtually no effect on the physical properties of the finished pipeline. The properties of the pipeline are mainly affected by the degree of crosslinking. As the degree of crosslinking increases, strength, heat resistance, and resistance to aggressive environments and ultraviolet rays increase. However, along with an increase in the degree of cross-linking, the fragility of the resulting pipeline increases and the flexibility decreases. If you increase the degree of crosslinking of polyethylene to 100%, then its properties will be similar to glass.

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

Fracture and restoration of shape after heating a PEX pipe to 100 °Ca with anti-diffusion layer

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

Rice. 1. Restoring the shape of pipelines after deformation

On rice. 1 the restoration of pipelines with various methods of stitching after a crease is shown. With all stitching methods, the pipelines regained their original shape. Wrinkles formed on pipelines coated with an anti-diffusion layer after restoration. In these areas, the anti-diffusion layer has peeled away from the PEX layer. This defect has virtually no effect on the characteristics of the pipeline, since the main load-bearing capacity of the pipeline is determined by the PEX layer, which has been completely restored. A slight peeling of the anti-diffusion layer does not significantly increase the oxygen permeability of the pipeline. A pipeline without an anti-diffusion layer becomes transparent after heating. This effect is inherent in any undyed cross-linked polyethylene.

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 crosslinking 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 bent at room temperature to a radius equal to five pipe diameters ( rice. 3), and when using a pipe bender or jig - to a radius equal to three diameters. A pipeline with more than 70% stitching will have a manual bend radius of at least seven diameters. Greater bending of the pipeline with such a degree of cross-linking can only be achieved by using a construction hair dryer.

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

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

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

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

This design is designed to eliminate the possibility of damage to the EVOH layer. However, tests have shown that a three-layer pipe (with a layer of EVOH applied on the outside) is more reliable than a five-layer pipe. The increased strength of a 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 a five-layer pipe, in which the working layer of PEX is interrupted by a layer of EVOH and glue, due to which the internal transverse intermolecular bonds of polyethylene are interrupted. Also, with this design, delamination of the pipe is possible if it is overheated with a construction hairdryer during bending.

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

But the temperature of the coolant during system operation is different. In summer and during the transition period, the coolant temperature is lower than the calculated one. To assess the applicability of pipelines to a certain temperature regime under conditions of changing coolant temperature, standards define operating classes. These classes show the proportion of the influence of various temperatures from the entire fifty-year service life.

On rice. 5 a graph is presented showing the duration of the influence of various temperatures on the pipeline during 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 class of operation of a given pipeline, indicated in the pipe passport. PEX pipelines presented on the Russian market are suitable for service classes 1, 2, 3, 4 and ХВ.

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

Due to its excellent gas barrier properties, EVOH Small is primarily used as a functional barrier in food packaging. By retaining oxygen and moisture, this layer preserves the taste and quality of food. Even in cases where the food is more stable or specially processed, e.g. baby milk The layer's barrier properties are used to protect sensitive vitamin content

Resistance to industrial chemicals

EVOH resists oils and chemicals, making it particularly suitable for packaging organic solvents, agricultural pesticides and all types of oils, while retaining all the benefits of plastics. The resulting 5-layer film with a barrier layer provides safe use with solvents and other chemicals while protecting their integrity.

Process efficiency

The presence of this layer leads to a reduction in production costs and packaging waste.
Plastic barrier films can be designed for aseptic filling, thereby reducing energy consumption during processing. Lightweight barrier-layer designs allow you to transport more goods instead of unnecessary heavy packaging. Inexpensive, but functional design packaging helps remove quality products to new markets.

The benefit of superior gas barrier properties is that less raw material (eg plastic) can be used without loss of performance. As a result, the packaging is lighter in weight and free of harmful chemicals environment. In addition, waste containing the barrier layer can be recovered and recycled.