Hydraulic braking and damping attachment for valves - eliminates water hammer initiated by feed-water changeover valves using piston with restricted bore

摘要

The equipment is mounted on top of the valve and its spindle is coupled to that of the valve. It comprises a double-acting hydraulic cylinder. When the piston and valve are in the upper position and are actuated downwards, fluid is forced from the lower chamber into a drilling in the spindle, through a throttle tube and out through another hole in the spindle into the upper chamber, the pressure difference across the throttle tube producing constant speed movement. After a predetermined travel, the port is closed and entry is via drillings in the piston from which the fluid flows through a second throttle tube before reaching the first, thus reducing the valve closing velocity. An alternative simpler design utilises a single throttle tube.