Surface Damages Caused by Cavitations at Hood of Howell Bunger Valve and Redesign to Avoid Them

Howell Bunger valve is hydro mechanic equipment which obtains regulation of free water stream with very high flow velocity at small opening. High flow velocity rates are the main reason for the occurrence of cavitations in the area of hood and body of the valve. The practical data refer to occurred surface damages of this type of valves are very rare in the literature. In this paper, the Howell Bunger valve installed at the dam Lisice, R. Macedonia was analyzed. The analyzed valve was produced by CMO, Tolosa, Spain. After one year exploitation period, significant surface damages occurred on the hood as a result of cavitation. This condition of the valve was the reason for redesigning the critical zones of the hood with the aim to overcome the origin of cavitations for small opening of the valve. The technical solution for redesigning of the flow domain is developed by using CFD software FLUENT. On the base of numerical results, the technical solution was implemented at the valve. The proposed redesign of the hood is confirmed by seven years of exploitation period after implementation. The proposed reconstruction and results presented in this paper can be useful for the constructors and users of this type of valves, and can be implemented in the new design of the valves and also at old installed valves.