Abstract
Siphon piping has been improved for the decreasing of construction costs. Although the examination by model piping is carried out about siphon formation, there are a few experimental reports using the actual pumpimg system. In this report, siphon formation which used the vertical mixed flow pump with discharge bore size 1,500mm was examined, and it turns out that the starting flow velocity of siphon formation is smaller than 1 m/s usually said. This is based on the increasing of the pump capacity by the delivery of the air remained in siphon piping. Moreover, the prediction of the air discharge time in a pipe showed that an air discharge model based on the flow pattern was a key factor.
