Le système d'adduction d'eau brute par canalisations sous pression de la région Est de toulon

Pressure-pipe raw water supply system in the area east of Toulon

Ingénieurs à la Société du Canal de Provence

Abstract

This system is designed to supply sprinkler irrigation systems covering an effective area of 8000 hectares, two drinking water purification plants, two industrial areas and an impounded reservoir. It is estimated that demand will amount to 37 million cubic metres by the year 2000, with a peak supply of 5 m³/sec to the head of the main canal. The scheme comprises a total length of about 30 kms of pressure ducting varying between 1250 mm and 450 mm in diameter, operating at pressures between 30 bars and 16 bars. Pipe pressure, duct layout and gradual growth of demand were important design factors for the scheme. Cement mortar-lined welded-steel pipes have been adopted for these high pressures. Provision is made for pressure-reducing arrangements to 3 bars at the head of the supply system and local pressure reducers on some distribution system branch lines. The following cost-saving design provisions have been made: a) Duplication of a major pipe run in ten years' time. b) Steady network flow conditions wherever high-level sites are available for building reservoirs for daily demand peak attenuation purposes. The system is automatic in operation, thus ensuring immediate availability of directly-connected network flow requirements. Steady flow for networks operating from storage is provided by a pressure reducer and stabilizer maintaining the required pressure at the head of the filling duct, irrespective of upstream supply pressure variations. This pressure corresponds to the head required to transmit the flow requirement. Reservoir inflow is controlled by a float valve. All ducts are protected by automatic flow cutoff arrangements, water hammer-limiting valve and gate operating time settings, and pressure relief valves. Operational security is ensured by feedback of significant discharge, pressure and stored water volume data to the operating centre and remote control of valves and gates to correct abnormal operation. Special attention was paid to the choice of hydraulic equipment, which was supplied by the following: a) Automatic shut-off gates, disc valves, relief valves: Neyrpic. b) Pressure reducer and stabilizer: Lezier. c) High-pressure valves: Saut du Tarn. Ducting installed to date totals 25 km in length. Further work is in active progress.