Plastics based on polymers are applicable in many industry fields. The sanitary industry has taken advantage of the solutions based on the so called plastics for many years. The PP (polypropylene) water pipes and PVC (made of polyvinyl chloride) sewage pipes enjoy widespread popularity. The advantages of such materials include durability and resistance to atmospheric and chemical factors, life up to even 100 years, good insulation and acoustic properties, lower manufacturing costs or subsequent recycling possibility. Materials made of polymers are light, have smooth surfaces, do not absorb water and are easily joined by means of gluing, sealing or welding. Furthermore, owing to the addition of appropriate plasticisers, pigments, flame retardants or other fillers, the spectre of applications becomes huge.
Fig. 1. PP elbows
Also in the HVAC industry, where the resistance to corrosion and chemical factors is of decisive importance, plastics replace the high-grade steel. PVC ventilation ducts are the most common and the most frequently installed ducts. PVC is the most popular and economic choice - it is characterised by high chemical resistance, and furthermore, it can be joined by bonding.
The temperature resistance of PP (polypropylene) pipes and fittings is higher than that of PVC elements, additionally, the flame retardant PPs version and PPs-el-s version, which conducts electricity, are available. The PE elements are fit for mounting from outside because of the temperature resistance up to -50C and UV radiation resistance. Last but not least, the range of typical materials includes PVDF, which is characterised by high resistance to the impact of halogens and other oxidants, resistance to temperatures up to +120°C, UV radiation and low flammability.
Plastics are joined mainly by welding; gluing by means of special adhesives, which dissolve the bound surfaces, is possible only in the case of PVC. Several joining techniques are applied, e.g. gas welding using the welding wire. This is an ideal solution for fitters because of the reasonable price and low weight of these devices.
Fig. 2. Wegener welder for hot gas welding
Extrusion welding is a more advanced and efficient method. Owing to this advanced method, it is possible to create very thick welds during a single run - it is possible to weld the material with the thickness up to 40mm. Extrusion welders extrude the adhesive, which is applied by the welding shoes to the joined surfaces plasticised with hot gas.
On top of this, stub pipes are joined by means of butt-welding of the heating element or socket heating sleeve, however, these methods are less popular in the case of large pipe diameters which occur in ventilation.
The classic areas, where plastics are used, include:
• chemical industry,
• plating industry
• clean rooms,
• chlorine treatment rooms (e.g. swimming pool engine rooms)
Advantages of plastic ventilation systems:
• Chemical resistance
• Corrosion resistance
• Low weight of the system
• Long life of the material - investment profitability
• Tightness of the systems in connection with the joining method (welding)
• The lower frequency of maintenance - the smoothness of the surfaces is limited by the formed deposits.
Alnor offers PVC and PPs ducts and fittings, but upon a special request, we will also supply PP, PPs-el, PE and PVDF elements. A wide range of fittings is available, including: elbows ranging from 90° to 15°, 90° tees, 45° tees, reducing tees, symmetrical and asymmetrical reductions, roof outtakes, grilles and even silencers. The large number of solutions allows the construction of a complete ventilation system.