What are the specific steps for the second inspection of ceramic linings?

I. Preparatory and Safety Confirmation Steps: Wear 350℃ thickened heat-insulating gloves and use a high-temperature insulating voltage tester to confirm that the high-voltage power to the hot runner heating circuit is disconnected, leaving only the temperature measurement circuit powered. Clean all flammable debris from the inspection area. Connect a dry compressed air source (moisture content ≤0.01%). Pre-install the high-temperature sealing fixture connector at the nozzle flow channel interface. Start the hot runner temperature control system and heat the nozzle to its rated operating temperature of 320℃ at a safe heating rate of 50℃/h. Maintain this temperature for 2 hours to ensure uniform temperature and complete thermal expansion. II. High-Temperature Sealing Test Steps: Connect a high-precision digital pressure gauge (accuracy 0.001MPa). Introduce 0.5MPa of dry compressed air into the flow channel and close the inlet valve to begin the pressure holding time. Maintain the pressure for 30 minutes. Throughout the process, scan the nozzle surface with an infrared thermal imager. If any abnormal temperature drop occurs, this is a leak point. Immediately stop the test and inspect for gaps. Verify the pressure gauge data. A pressure drop ≤ 0.01 MPa within 30 minutes indicates a satisfactory seal. Record the test data and release any remaining pressure in the flow channel. III. Thermal Shock Stability Test Procedure: Turn off the hot runner heating system and allow the nozzle to cool naturally and slowly to room temperature in a dust-free environment. Avoid sudden cooling with air or water. After cooling, insert a high-definition industrial endoscope into the flow channel and scan the inner wall of the ceramic liner throughout the entire process, confirming the absence of dark lines, chipping, cracks, or misalignment defects. Repeat the "heat to 300℃ → naturally cool to room temperature → endoscope re-inspection" procedure, completing a total of 3 full thermal shock cycles. Record the temperature change curve using a digital temperature controller recorder throughout the process. IV. Operating Condition Matching Verification Procedure: Restart the hot runner and heat it to the rated operating temperature. Using a calibrated Husky K-type coupler probe, measure the actual temperature of the ceramic liner area point by point. Verify the temperature controller display data, confirming that the deviation between the measured temperature and the displayed value is ≤ ±0.3℃, with no localized overheating points and no temperature data fluctuations or drift. Using a dial indicator bracket and a high-precision micrometer, re-measure the key mating dimensions of the nozzle, confirming that the ceramic liner has no axial displacement or deformation, and the coaxiality deviation remains ≤ 0.02mm. V. Final Reset Procedure Use a lint-free cloth dampened with anhydrous ethanol to clean any residual oil and impurities from the nozzle joint surfaces, and evenly apply a thin layer of high-temperature resistant fluorine passivation grease. Replace the nozzle with a brand new perfluoroether rubber seal ring, and reinstall the nozzle onto the hot runner manifold plate, confirming that all connections are secure. Compile all test data to form a complete second inspection and acceptance record, and archive it in the hot runner equipment maintenance log.