A44 type closed fully open safety valve with wrench is suitable for equipment and pipelines with working temperature ≤ 300°C air, steam, liquefied petroleum gas and other media, as an overpressure protection device. When the pressure in the equipment and pipeline exceeds the allowable value, the valve automatically opens, and then the full amount is discharged; When the pressure is reduced to the specified value, the valve closes automatically to ensure the safe operation of the equipment.