When installing typical hot water heating systems, it is impossible to do without water pipes. Modern requirements for heating equipment force us to carefully choose the products that are suitable for these purposes. Cross-linked polyethylene for heating is a good option when choosing a material that can replace outdated steel water supply pipelines.
Types of pipes by the method of cross-linking polyethylene
Crosslinked polyethylene (SP) is a synthetic material that has a modified network structure. Its molecules additionally adhere to each other by side bonds that are absent in a conventional polymer. The crosslinking effect gives the material additional strength, while simultaneously reducing the thermal ductility.
Stitching technologies
Stitching of polyethylene materials is organized using one of the following technologies:
- peroxide method;
- chemical method;
- physical option.
In the first case, hydrogen peroxide is used as a reagent. The process takes place at a temperature of 200 degrees, due to which the crosslinking is more uniform.
The chemical (or silane) method is characterized by the fact that polyethylene of the required quality is made with the addition of water, silane and special catalysts. This method is considered the most common in production practice, although the percentage of stitching is only 65-70 units.
The physical or radiation method is understood as driving a polyethylene mass through an accelerator, in which it is exposed to X-ray and gamma radiation. Free atoms of the same elements take part in this process, forming new bonds. The degree of crosslinking achieved in this case is 60%.
Comparison of properties
XLPE has an ordered structure that resembles the crystal lattice of solids. Moreover, in each specific case, the finished product acquires original properties. The most uniform crosslinking is obtained with the peroxide method, which is considered unproductive and expensive. This approach is also completely inapplicable in the production of multilayer pipes. The silane method achieves a high production rate of not very flexible products, and the use of the radiation method guarantees the simplicity of manufacturing products from cheap raw materials. The choice of a suitable material in this case depends on the features of the use of pipe products.
Specifications
Pipes made of cross-linked polyethylene, in addition to the declared high strength index, have properties that determine their technical parameters. Crosslinking of molecules allows the melting point of this material to be increased. Its modified samples have the following heat resistance indicators:
- the softening limit is 150 degrees;
- the melting limit is 200 degrees;
- such polyethylene begins to burn only when it reaches 400 degrees.
With the crosslinking of the plastic material, its strength increases, but at the same time the elongation at break rate decreases. It almost does not react to abrupt changes in environmental parameters, while exhibiting similarities with metals.In terms of resistance to chemical reagents, it is also not inferior to them, and even surpasses in resistance to deformation. The main characteristics of cross-linked polyethylene include:
- structure density reaching 940 kg / m³;
- operating temperature range from 0 to +95 ° С;
- resistance to mechanical stress (shock loads) at temperatures up to -50 ºС;
- thermal conductivity;
- flexibility factor;
- tensile at break index (from 350 to 800%);
- life time.
The service life of the joint venture is from 10 to 50 years, depending on the temperature in the pipes.
Advantages and disadvantages
The advantages of polyethylene pipes made using PEX and PE-RT technologies include:
- temperature resistance (frost resistance), especially pronounced in PE-RT pipes;
- high strength indicators, due to which these products are not susceptible to external destructive influences and internal stresses;
- plasticity of the material, allowing their use on complex laying routes with many turns;
- immunity to corrosion, as well as aggressive inclusions in the coolant, and environmental friendliness.
Smooth walls inside the pipe channel provide minimal hydraulic resistance to the moving heat carrier, due to which the likelihood of deposits is minimal. Some of these advantages are fully manifested when comparing the joint venture with metal-plastic, from which pipes for floor systems are also made. The latter does not withstand the freezing of the coolant and poorly restores its shape. Otherwise, these two competing types are equally good for arranging warm floor coverings. The disadvantages of the joint venture include the impossibility of bending them along the radius above the limiting value and the complexity of the design of the turning zones, since the joints in these places have to be securely fixed.
Applications
The versatile properties of SP, including resistance to destructive effects and temperatures, determine the areas where this material is most often used. For example, the Uponor pipe is ideal for heating domestic premises. However, it is often used for the following purposes:
- production of pressure pipes for cold and hot water supply;
- use as elements of industrial heating structures;
- application in consumer drinking water supply systems.
The high-quality Uponor heating pipe, obtained by the cross-linking method, can be used in the arrangement of warm floor structures, as well as in air conditioning systems for domestic and office premises.
Principles and nuances of pipe installation
Competent installation of polyethylene pipes is possible only if the following rules are observed:
- pipes from the joint venture are mounted so as to prevent the possibility of freezing;
- for the arrangement of pipelines of heating systems or FWH, a material is selected that is suitable for water heating of floors;
- the choice of the method for connecting pipes from the joint venture depends on the diameter of the blanks used.
- fittings are used for pipes with a diameter of up to 32 mm, and for large sizes they are mounted by welding.
The procedure for laying JV pipes is based on the principle of using compression fittings. If necessary, these connectors are easily dismantled and, after replacing the gaskets, are put back in place. For the installation of such a fitting, two adjustable wrenches will be required; with small diameters of the workpieces, they can do it with a conventional tool.
Operating tips
When products based on the JV are put into operation, their throughput increases markedly. This is due to the peculiarity of the material used, which has the property of gradually expanding. When the service life is reached, the diameter of such pipes increases by about 3%.
Another factor affecting the increase in the volume of fluid pumping is a change in the structure of the pipe material, after which the surface acquires additional plasticity. This helps to reduce the resistance to the movement of the water carrier and to accelerate its movement. Taking these factors into account when operating pipes will allow you to avoid troubles in the form of leaks at the joints.
