Palermo goes for PE
One of the largest water supply projects in Europe is currently underway in Palermo, Sicily, using Georg Fischer Wavin's new PE 100 system. Report by Friedhelm Keller, product manager for water supply systems at Georg Fischer Wavin.
An ever growing population, an old water distribution system and deficient natural springs led to dramatic water supply crises in Palermo at the end of the 1980s, particularly in summer months.
The rapid growth of the population, which had doubled in 50 years, was only one of the factors which had to be considered. The network was nearly 100 years old and water loss was occurring at a rate of about 45-50%. Plus the area is in an earthquake zone and natural springs are not a reliable raw water source.
There were only three water reservoirs, fed by artificial lakes, each with a volume capacity of 36,000m3. Drinking water obtained from surface water did not last long in the hot summer months with low rainfall. For months on end, running water was only available every two days for two to three hours at a time. Under these conditions, life became difficult for the millions of people who live in the Sicilian capital.
On the basis of the situation analysis, it was felt that the following demands would be placed on the network components of a new water supply system:
- The population will continue to grow, so the system had to be laid out to provide adequate capacity for the next 50 years;
- Constant supervision had to be possible for all the important parameters such as volume of water supplied, volume of water used, quality of water in the reservoir and in the distribution network;
- Overall capacity should be sufficient to provide 430l/person/day. Actual consumption is currently around 270l/person/day;
- The materials selected had to guarantee that corrosion would not occur;
- Mechanical couplings could not be used because of the risk of earthquake damage, hardening of elastomer seals after about 10-12 years, and penetration of hazardous materials from contaminated ground;
- And a service life of at least 50 years had to be guaranteed
Because the water crisis had such a strong influence on all aspects of public and social life in Palermo, the EU leant its support to the project. This meant that all products and services used on the network were tested to the appropriate EU standards.
Four materials were evaluated for their suitability: steel, cast iron, PVC and PE 100. The two metal materials have obvious disadvantages: they are prone to corrosion, electrolytic corrosion, saline water in the ground and have high maintenance costs.
PVC does not have the flexibility of polyethylene which means it does not meet the safety requirements for an earthquake zone.
PE, and particularly the new PE 100, was clearly the material of choice for the Palermo network.
- PE 100 can be fused and requires no mechanical connections;
- The joints, which are all welded, provide a leak-free network;
- PE 100 is 100% corrosion-resistant and guarantees a maintenance free piping system
To install the PE piping system the following fusion techniques were used:
- Butt fusion;
- And flange connections in accessible shafts
The following fittings and valves were used:
- Electrofusion sockets;
- Electrofusion, corrosion-free pressure tapping valves, all plastic, with 360o adjustable outlet spigots. The connection direction can be adjusted as required without any additional fittings;
- Sectional valves: cast iron gate valves and gate junctions, but only in accessible gate shafts;
- Electrofusion PE/brass adapters, where the brass part could be turned and positioned before fusion with the fitting. This improves installation handling considerably.