抄録
Semi-closed pipeline systems are usually constructed as demand-oriented systems by installing a decompression facility with a float valve in the intermediate pressure regulating facilities and/or in the inflow works of farm ponds. A disk valve is often used as the float valve for the pressure regulating facility. However, even when the capacity of the decompression tank with the disk valve is sufficient, rotation or chattering of disk valve can occur when water is diverted at a low flow rate or when water diversion starts or stops. This can in some cases cause a strong water hammer. In this paper, a dynamic balance model is developed that describes the rotational vibration of a disk valve system balancing a float and a disk, and incorporated into the commonly used pipeline flow model in order to simulate the transients in a pipeline system with disk valve systems. A sample application of the system simulation model is made to a real pipeline system to examine critical situations that can generate chattering. The results show that a decreasing flow in stopping water diversion and even a constant flow of 20% or less of the design flow rate are prone to chattering that may cause successive water hammers or saw-toothed pressure waves. It is also demonstrated that, regardless of capacity of decompression tank, the chattering generates a water hammer.
