GB/T 23711.8-2019 "Test Methods for Plastic-Lined Pressure Vessels - Part 8: High Resistance Test" specifies the principles, equipment, procedures, and result evaluation for high resistance testing of pressure vessels with steel shells lined with plastics such as PVC-U, PE, and PTFE. It applies to high resistance testing of relevant types of pressure vessels. The test must be conducted in an environment of (20±3)°C, using a high-insulation resistance measuring instrument compliant with JJG690-2003 with an accuracy not lower than 5.0 grade. The positive terminal of the instrument is clamped to the metal shell of the vessel, and the negative terminal is immersed in clean water inside the vessel. After stabilization, the resistance value is read, and the average of two measurements is taken. By comparing this value with the specified minimum resistance, the presence of conductive defects such as leaks in the lining is determined, ensuring the insulation performance of the equipment.