The mechanical pressure gauge of self pressurized liquid nitrogen container is used to read the standard working pressure of liquid nitrogen container 005mpa, the maximum working pressure of 0.09mpa, the opening pressure of primary safety valve of 0.099 MPa, and the opening pressure of secondary safety valve of 0.15Mpa; the standard of pressure vessel is that the working pressure exceeds 0.1MPa, so the self pressurized liquid nitrogen container is not a pressure vessel.