I. Necessity and Basic Process for Flange Inspection
Flanges are critical connecting components in piping systems. Their sealing and stability directly impact equipment safety. Daily inspections should follow the following process:
1. Visual Inspection: Observe the flange for any visible deformation, cracks, or corrosion.
2. Functional Testing: Verify sealing performance through a pressure test (typically at 1.5 times the design pressure, as per ASME B16.5).
3. Recording and Analysis: Compare inspection data with historical records to identify potential risks.
II. Detailed Explanation of Core Inspection Items
1. Sealing Surface Inspection
- Scratches and Dents: Any depth exceeding 0.1mm (according to GB/T 9124) requires repair or replacement.
- Flatness: Inspect with a ruler; the gap should be less than 0.05mm/m.
2. Bolt and Nut Condition
- Tightening Torque: Requires compliance with standard values (e.g., M20 bolts are typically 250-300 N·m, refer to ISO 16047).
- Rust and Loosening: Apply anti-rust grease regularly and check the threads for integrity.
3. Gasket Condition
- Material Compatibility: Select based on the temperature and pressure of the medium (e.g., asbestos gaskets have a temperature resistance of ≤260°C, while spiral wound gaskets can reach 800°C).
- Signs of Aging: Replace if hardening, cracking, or compression deformation exceeding 10% occurs.
4. Corrosion and Protection
- Wall Thickness Measurement: Ultrasonic testing of remaining wall thickness. Corrosion exceeding 20% of the original thickness is considered unacceptable (API 570 standard).
- Coating Inspection: Epoxy coating damage exceeding 5% requires re-coating.
III. Inspection Points for Special Operating Conditions
1. High-Temperature Environments: Focus on inspecting bolt stress relaxation caused by thermal expansion. Monthly re-tightening is recommended.
2. Vibration areas: Increase inspection frequency to weekly, and pay attention to bolt anti-loosening measures (such as double nuts or thread sealants).