Double Block and Bleed Ball Valve has Dual ball structure which evolved to replace and add the process of bolting together individual valves to make the valves in one body. it saved a lot of space and material, it is the development tendency of the valve in the future. Dual ball is a necessary requirement when maintenance is taking place down stream of the first isolation valve. The cavity can be relieved via vent or drain connections at the body. The independent upstream and downstream sealing ensure a tight shut-off at the body cavity in fully opened and closed position. This allows for verifying the tightness of the ball valve in line via the cavity.