In line with the national standard gb/t17906-1999 "hydraulic demolition tools General technical conditions", Expansion force 30-45kn, expansion distance of 620mm; at 80% rated operating pressure, the expander completes from the closed position to the maximum opening, then returns to the original position and 50 consecutive cycles, after which the action should be normal , no leakage and abnormal phenomenon, the edge should be no curl, blade phenomenon.