GB/T 23711.4-2019 "Test Methods for Plastic Lined Pressure Vessels—Part 4: Negative Pressure Resistance Test" specifies the requirements for the negative pressure resistance test of steel pressure vessels lined with plastics, which is applicable to the performance testing of relevant types of equipment. The core instruments for the test include vacuum pumps such as rotary vane and Roots types that meet the requirements, as well as vacuum gauges with a measurement range of -0.1 MPa to 0 MPa and an accuracy not lower than 2.5 grade. Temperature controllers may also be equipped to meet the needs of special temperature tests. Before the test, a spark test must be passed. Subsequently, the vessel is evacuated to the specified negative pressure value and held under pressure. The liner is observed through a sight glass for deformation or cracking, and the negative pressure resistance of the equipment is determined based on the combined results of subsequent spark tests.