Butterfly valves for pumping plants are designed for blocking the pumping unit penstock in the following cases:
1) At each shutdown of a hydraulic unit;
2) At repairs and inspections of the hydraulic unit water passage;
3) In case of emergency:
— at loss of voltage across thу pumping unit motor;
— at suden pressure drop in OPU (damage of oil pressure line extending from OPU to the butterfly valve penstock);
— at loss of DC voltage in control circuits.
Butterfly valves for a penstock are designed for blocking a penstock in the following cases:
— at repairs and inspections of a penstock;
— in case of emergency — to protect a penstock.