The older we get, the faster time flies. If in childhood summer vacations seemed like a huge period of time, now the summer ends before it starts (well, you know, yes, that a third of the summer has already passed?). I always thought it was natural for growing up, but recently I realized that the reason for this perception of time is a little different. It's all about new impressions, experiences, emotions. In childhood, there are more of them, since you see many things for the first time. As we get older, we live day after day, month after month, without experiencing anything fundamentally new, and therefore our memory has nothing to cling to and the past week seems very short. But time is a very subjective concept, one and the same hour can drag on for eternity for someone, and for someone fly by in an instant. So why not lengthen your life by making your personal time longer than others?
Six months ago, time was something very fast for me. In reality, it seemed that from Friday to Friday, not seven, but a maximum of four days pass. Well, it feels like. The weekend, of course, flew by with even greater speed. But on January 1, I started experimenting with new habits, and I noticed that time began to flow more slowly. My raw February, for example, seemed like the longest month of the year to me. It's all about new emotions and experiences, I think. Ideally, of course, it would be best to travel, look at new places and meet new people, but not everyone can afford it. Well, or not everyone can decide so easily. Therefore, the easiest way to slow down the passage of time is to search for new hobbies. Something new every month. In June, you can do drawing, in July, yoga, in August, give up meat. Something new every month. Daily. After 30 days, you can abandon your new habit, or you can continue to live it if you suddenly liked it.
Another important component is the weekend. They need to be planned in advance. Going to the cinema, museum, park, exhibition. It is best to do this yourself, either with people you are really interested in, or with a person who will be appropriate in the place where you are going to go (for example, a photographer, if you are going to a photo exhibition). Visit the most unexpected places for yourself every week. There are so many of them in fact. You can just get out to some cafe, to that part of the city that you have never been to before. If you don’t be lazy and do it every week, then your time will definitely stretch out and your life will be filled with new emotions.
SP Slide XLPE pipes with a PEX-b / EVOH barrier layer are intended for use in radiator heating, water supply and water heating systems.
SP Slide XLPE pipes are manufactured at the Metzerplas plant (Israel).
SP Slide XLPE pipes with a PEX-b / EVOH barrier layer have a number of advantages.
Barrier EVOH layer prevents oxygen from entering the pipeline system. Heating and water supply elements are not subject to corrosion. The inner layer of the pipes is abrasion resistant. The ideally smooth inner surface of the wall 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 PEX-EVOH cross-linked polyethylene are distinguished by their noiselessness in use, in contrast to 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 homogeneous. It contains amorphous and "crystalline" zones. The most effective crosslinking occurs in amorphous zones, starting from a temperature of + 125 ° C.
Crosslinking also occurs in the "crystalline" zones. When cooling down, the crosslinking process continues in the finished pipes in air and accelerates to hot water. Minimum interest crosslinked molecules (crosslinking), established by the PEX-B pipe standard, is 65%.
Pipes with a low percentage of crosslinking (less than 60%) are not recommended for installation in radiator heating systems.
Outer diameter - 20 mm
Wall thickness - 2.0 mm
Coil length - 100/200 m
Scope - water heat-insulated floor
Service life - up to 50 years
Maximum working temperature - 95 о С
Working pressure - 10 bar
Oxygen diffusion per day - 0 mg / m3
Emergency mode temperature, (max 1 hour) - 100 о С
Crosslinking degree - 65-85%
Thermal conductivity coefficient - 1.2-1.4x10 -4 W / m * K
Linear elongation at a temperature of 95 ° C - 3% per 1m
Thermal conductivity coefficient - 0.32 W / m * s
Volume 1 r.m. pipes - 0.201 l
Film with "EVOH" is a random copolymer of ethylene and vinyl alcohol. It is a crystalline polymer that has a molecular structure represented by the following formula:
Films of 5 layers based on a barrier layer have excellent workability and excellent barrier properties. The key to this remarkable balance is the combination of the proper copolymerization of ethylene with vinyl alcohol, a carefully selected degree of polymerisation, and the uniquely patented manufacturing process that is used in the production of EVOH copolymers. These unique polymers are blown in a 5-layer film process and are especially suitable for food, medical, pharmaceutical, cosmetic, agricultural and industrial packaging.
EVOH
Product quality takes important place in production, but the packaging of this product is not inferior in importance to the intended result, namely its delivery to the end consumer. Here you need a presentable look and reliability during storage and transportation. To solve such problems in the industry of creating a film material, various types of packaging are being developed that satisfy the most tricky requirements of manufacturers. This is possible by combining multiple sequences and layers of film material.
A big breakthrough in the technology of creating different types packaging with excellent barrier properties is the use of EVOH... This material has unique qualities due to its chemical structure: a compound of polyethylene (PE) and polyvinyl alcohol (PVA). At the same time, alcohol is responsible for the barrier properties of the finished material, and polyethylene makes it susceptible to heat treatment. Since alcoholic polymers are susceptible to negative impact moisture, then polyolefins are attached to the EVOH on both sides to protect it. And when it burns, only water and CO₂ gas are released, which makes the material easy to recycle.
Also, the uniqueness of EVOH lies in its quality, which by its properties allows not only replacing such expensive materials as metal foil, sheet metal, glass, but also has a number of the following advantages:
XLPE pipe 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. Operation classes in accordance with GOST 52134-2003 - 1, 2, 3, 4, XB. The design of the pipe includes a layer of polyvinylethylene (EVOH), which prevents oxygen from diffusing into the coolant.
Installation of PEX-EVOH polyethylene pipes is carried out using VALTEC press fittings. Designed service life - 50 years.
The material of VALTEC PEX-EVOH polyethylene pipes is cross-linked polyethylene (PE-X). It is obtained from ordinary high-density polyethylene by a special treatment that 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, XLPE pipes are characterized by a low roughness of the inner surface, are not subject to corrosion, and do not emit into the stream. harmful substances within the operating temperature range, are electrically inert, do not propagate (on the contrary - absorb) noise and vibration, 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 underfloor heating, and technological installations with an operating temperature of up to 80 ° C (at an operating pressure of 6 bar). For a short time, let us heat the transported medium up to 95 ° C. The design of the pipes 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 the outer diameter and wall thickness of the pipe. Delivery form - bays of 200 m.
Today, the share of the Russian construction industry 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. Moreover, lately wide use received systems underfloor heating... The temperature and pressure of the coolant in these systems allow the use of simpler and cheaper materials. That is why on Russian market there is now a great demand for XLPE piping. This kind piping combines reliability when used in low-temperature heating systems, ease of installation and low cost.
A 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. Conventional polyethylene consists of long hydrocarbon molecules that are in no way connected to each other and is not suitable for use as the main material for heating pipelines due to its low temperature resistance. Molecularly cross-linked polyethylene is cross-linked between chains of hydrocarbon molecules, and therefore this material has a higher strength and rigidity and, most importantly, a 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 between which from ordinary 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 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 the polyethylene, the wall thickness of the pipeline and the method of applying the oxygen barrier layers.
Crosslinking of polyethylene determines the strength and thermal characteristics of the pipeline. First of all, stitching allows to achieve long-term resistance to high temperature and pressure (increases the log-proportional relaxation limit). Crosslinking of polyethylene can occur different ways and with varying degrees... There are three main industrial methods for crosslinking polyethylene:
VALTEC PEX-EVOH pipelines undergo a hollow crosslinking cycle using the silane method (PEX-b) on modern equipment, which ensures uniform crosslinking of polyethylene with a crosslinking degree of 68-70%.
The piping stitching method has practically no effect on physical properties finished pipeline. The properties of the pipeline are mainly influenced 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, as the degree of crosslinking increases, the fragility increases and the flexibility of the resulting pipeline decreases. If the degree of crosslinking of polyethylene is brought to 100%, then its properties will be similar to glass.
Likewise, cross-linking of polyethylene gives the resulting pipeline a "shape memory effect". Its essence lies in the fact that a pre-deformed pipeline, after heating, restores its original shape. This property is manifested due to the fact that, during bending and deformation, the molecularly bound areas are compressed or stretched. After heating, in places of deformation, internal stresses arise, due to which the original form is restored ( rice. 1).
Fracture and restoration of the shape after heating up to 100 ° C of the VALTEC PEX-EVOH pipe (stitching method - PEX-b)
Break and shape recovery after heating up to 100 ° С of PEX-a pipe with an anti-diffusion layer
Fracture and restoration of shape after heating up to 100 ° С pipes made of PEX-c without an anti-diffusion layer (unpainted cross-linked polyethylene becomes transparent at high temperatures)
Rice. 1. Restoring the shape of pipelines after deformation
On rice. 1 shows the restoration of pipelines with various methods of stitching after a crease. With all the methods of cross-linking, the pipelines have regained their original shape. Wrinkles have formed on pipelines covered with an anti-diffusion layer after restoration. In these places, the anti-diffusion layer peeled off 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. Insignificant detachment of the anti-diffusion layer insignificantly increases the oxygen permeability of the pipeline. A pipeline without an anti-diffusion layer becomes transparent after heating. This effect is inherent in any unpainted XLPE.
Shape memory is very useful for editing. If during the installation of the pipeline a break, squeezing or other deformation is formed, then it can be easily eliminated by warming up 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 warms up, 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. 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 range of the degree of polyethylene crosslinking 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 by a radius equal to five pipe diameters ( rice. 3), and when using a pipe bender or conductor - by a radius equal to three diameters. Piping with more than 70% crosslinking will have a manual bend radius of at least seven diameters. A greater bend of the pipeline with this 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 section will return to its original shape. However, if you preheat the pipeline and allow it to cool in a fixed position, then it will retain this position. When the pipeline is reheated, the segment will return to its original state due to the shape memory effect.
Shape memory should not be confused with elastic deformation. In the first case, the original shape is accepted only after heating, and in the second, immediately after the removal of deforming forces and only within the elastic deformation (without kinks).
VALEC PEX-EVOH pipelines can be embedded in building construction with or without a cover. 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 pressure of the coolant 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 the use of standard press fittings available for metal-polymer pipelines for pipeline installation.
The disadvantage of PEX is that it is permeable to oxygen. Water in pipelines without oxygen protection through certain time 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 base PEX layer and the EVOH layer are bonded together with glue. 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 / m 3 · day, which is acceptable for heating systems.
In the VALTEC PEX-EVOH pipe, the anti-diffusion layer is made from the outside, i.e. the pipe has a three-layer construction: PEX-glue-EVOH. There are also five-layer (PEX-glue-EVOH-glue-PEX) pipes on the market ( rice. 4).
Rice. 4. Construction of five- and three-layer PEX 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 an EVOH layer 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 the five-layer, in which the working PEX layer is interrupted by the EVOH layer and glue, which interrupts the internal cross-molecular bonds of the polyethylene. Also, with this design, pipe delamination is possible when it overheats. construction hairdryer during bending.
It is a misconception that the outer layer of EVOH in a 3-layer construction is prone to abrasion. The hardness of the EVOH layer is significantly higher than that of the PEX layer, so if properly handled, damage to the outer layer is unlikely.
It is recommended to use cross-linked polyethylene pipelines when installing low-temperature heating systems. The use of PEX pipes 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 design life of the pipeline in such a system will be reduced.
Pipeline manufacturers generally set maximum operating temperatures and pressures based on a pipeline's service life of 50 years. When embedding and hidden laying, the replacement of these pipelines can be done in conjunction with overhaul buildings or premises. More frequent replacement of embedded pipelines will result in large financial expenses for alteration of building structures.
But the temperature of the coolant during the operation of the system is different. In summer and during the transition period, the coolant temperature is below the calculated one. To assess the applicability of pipelines to a specific temperature regime under conditions of changing temperature of the coolant, the standards define the classes of operation. These classes show the shares of influence different temperatures from only fifty years of operation.
