Large-caliber ultrahigh-pressure-difference steam emptying valve

The utility model relates to a large-caliber ultrahigh-pressure-difference steam emptying valve. Valve comprising a valve body, a self-sealing valve seat is arranged in the valve body; a labyrinth sleeve and a pressing ring are sequentially connected to the self-sealing valve seat. The pressing ring, the labyrinth sleeve and the self-sealing valve seat are pressed in the valve body through the pressing quartered ring; the upper end of the valve body is connected with a bonnet pressing plate; a self-sealing valve cover penetrates through the valve cover pressing plate; the sealing end of the self-sealing valve cover is connected with a valve cover pressing plate through a valve cover adjusting bolt and a valve cover nut; a valve cover self-sealing ring is arranged between the sealing end and the valve body; a valve cover quartering ring is arranged on the upper side of the sealing end of the self-sealing valve cover in the valve body; a stepped valve core is arranged in the pressing ring, the labyrinth sleeve