GB/T 23711.3-2019 "Test Methods for Plastic Lined Pressure Vessels—Part 3: High Temperature Resistance Test" applies to steel pressure vessels lined with plastics such as PVC-U, PE, PTFE, and PVDF. It specifies the test conditions, equipment, and evaluation criteria. The test requires the use of a high-temperature test chamber that meets the requirements, with test temperatures set between 60°C and 140°C based on material characteristics. The heating rate should be controlled at (3 ± 0.6)°C/min, combined with a Grade 1 tensile testing machine. After three high-temperature-to-room-temperature cycling tests, the sample's shape, dimensional change rate, tensile strength, and elongation at break are inspected. If no significant defects are observed and the performance meets the standards, the sample is deemed qualified, ensuring the reliability of the equipment in high-temperature environments.