The multilayer pipes, also called PAP, are used to do the supply both in cold and hot water. It is commonly used in heating systems, plumbing installations and underfloor heating. It is about a system integrated of pipes in cross-linked polyethylene, of combined construction between metal and thermoplastic, also known like hybrid.
With the pass of the years they have been surpassed in the use to the traditional iron and galvanized copper pipes. This type of pipes is more economical and simpler to install; these pipes are much more resistant to the corrosion and besides, they support the effect of many chemical products. Its transportation and its handling are simpler and more economical than in the case of the old pipes, due to its light is also lesser. Besides, they are flexible and they have poor resistance to the pass of the fluids.
The multilayer pipes are composed of these four layers:
- Cross-linked Polyethylene (PE-X). It is the one that enters into contact with the liquid; therefore, it is the first layer. It is a type of polyethylene that supports temperatures up to the 95º C and a pressure of up to 4 bars.
- Aliminium Layer (AL). It can be welded to the rest of the layers by laser or by butt welding so that it has the same thickness in the whole pipe. Some manufacturers do the butt welding what gives it much more resistance and quality.
- External Protective Polyethylene (PE) Layer. Its function is to uniformity and joins to the whole pipe. It can also have the type of polyethylene known as PE-RT, an improved polyethylene at the temperature which is capable of supporting a temperature of up to 30 ºC.
- Between each layer, the pipe has two intermediate adhesive layers, which help to join to the rest of all.
One of the great advantages of the multilayer pipes is that, inside them, they have a heart of aluminium which makes that the dilatation is not so large, something that will occur in the case we would use plastic instead. Aluminium supports high temperatures without getting deformed.
One of the types of the most used pipes due to the advantages it offers is the PPR, which is used in most of the projects of improvements in the supply of water for the dwellings. The reason is that it is about an optimal material for the cold and hot water system, the engineering of water purification, the underground heating systems for wooden floors and other type of jobs. Its uses suppose a thermal insulation and important saving of energy.
The PPR (‘polypropylene random copolymers’) consists of thermoplastic resins achieved by the polymerization of the propylene, with links of ethylene introduced in the polymer chain. It doesn’t corrode and support high temperatures without bending. In concrete, the temperature of water transmitted by the pipes can reach the 95 °C.
Some of its uses in the networks of cold and hot drinking water pipes, both for residential buildings like commercial buildings, the PPR pipes are used in these other specific uses:
- Heating systems.
- Installations of compressed air and other industrial applications.
- Cooled water networks in air conditioned systems.
- Usage systems of rainwater and installations in swimming pools.
- Transportation of chemical-industrial products.