Author(s): G. Balacco; A. Castorani; A. R. Di Santo; A. F. Piccinni
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Abstract: The introduction of a bypass valve in a gravity system has also the mainly useful purpose to reduce the maximum overpressure of water hammer during the closing manoeuvres. The paper summarizes the results obtained by a dimensionless mathematical model indicating an optimal dimensional ratio between pipe, main and bypass valve diameter in order to reduce water hammer maximum overpressure. Bypass valve adopted during simulation was a Larner-Johnson ported. The dimensioning criterion individuated has a general character due to a wide range of boundary conditions used: valves closing laws and their time, several installation plans, celerity and main valve dimension. Results have demonstrated how a bypass valve can be used to reduce the maximum overpressure value. Even if the total manoeuvre time for main valve and bypass valve, could be equal to that one previewed for the main valve, however that system reduces efficaciously overpressure, particularly for the faster manoeuvres.
Year: 2009