Hand Book Plastic Pipes 3
III. Characteristics of Materials mattering for sewage systems
- Concrete/Ferroconcrete has been used since ages past for sewage systems and thus profits from long experiences. Concrete is utterly solid, stable and resistant against shifting during installation. Later on, pipes may likely shift because of different pressures. Furthermore it is high temperature resistantand inflammable. On the other hand concrete has a high mass density, which makes the transport and implementing more difficult. Besides that, concrete is vulnerable towards crack initiation, aversion and thus to in- and exfiltration. Last but not least the usually very efficient and high quality surface structure is soon worn out. Comentitious materials that are in sewage systems are more vulnerable towards corrosion than others.
- Steel has high strength and can be welded. It was quite often used for coverings in sewage systems. Themor and butt are not as harmful towards steel pipes as to other materials but still it can more easily be harmed during transport than plastic for example. Steel has a low corrosion resistance and is thus laminated from inside with an additional corrosion protection.
- Thermoplastic (PP/PE) are flexible in their structure and deform in the case of pressure. These deformations happen without crack formation and are especially positive in regions of temperature variations or earthquakes. Thermoplastics have a very high corrosion resistance such as against chemical and physical factors of damage. They are easily weldable and have afterwards a high material density. On the other hand they are flammable and sensitive towards oils and fats. Their light weight may, next to numerous advantages, be problematic in terms of shifting. An unchallenged advantage of thermoplastics in the durability of 100 and more years.
- GRP is composed of strands of glass, lightweight and has good thermal insulation properties. Additionally glass fiber reinforced plastics have the ability to contain liquids with very high temperature. Their light weight is, just as for thermoplastics, a plus and a minus same time. GRP pipes have a higher impact sensitivity and thus a relatively higher crack initiation. GRP pipes are very sensitive against high pressure purification.
- Cast-iron is know for its robust chemical composition. A rust layer offers resistance against material destruction and is additionally secure because of its thick walls. Next to its weather reliability (especially UV), it has a low electronic conduction and a good breaking stress. Problematic is, that it is only partlyweldable and difficult to cut. The material is quickly destructed with aggressive waters or vagrant streams which makes them corrosion vulnerable in sewage systems. Finally cas-iron is heavy and hard to handle.