1. Check the installation direction: Ensure the flange face (toothed or smooth) is flush against the surface of the connected component, facing inwards, with the threaded end facing outwards.
If the flange face faces outwards, the anti-loosening function will fail, potentially causing crushing or loosening.
2. Verify tightening quality:
Diagonal re-inspection: Check if tightening is done in a diagonal or star-shaped sequence to avoid flange misalignment.
Torque sampling: Use a torque wrench to randomly check key bolts, ensuring the design preload is reached and the value is stable without backflow.
Exposed thread length: After tightening, at least two complete threads should be exposed on the bolt. Too short, and it may not be fully engaged; too long, and it will affect safety and protection.
3. Assess Sealing and Leakage Risks
In pressure systems, conduct a pneumatic or hydrostatic test, pressurizing to 1.15 times (pneumatic) or 1.5 times (hydrostatic) the working pressure and holding for 30 minutes.
Apply soapy water to flange connections, bolt roots, and gasket edges, observing for continuous bubbling. Bubbling indicates a leak; depressurize, retighten, or replace the gasket.
4. Visual and Structural Integrity Inspection
Check that the flange faces are fully fitted, without gaps or warping.
Zergled flanges should have slight indentations, indicating effective engagement and anti-loosening.
Inspect nuts and bolts for deformation, cracks, or stripped threads.
5. Supplementary Inspections for Special Operating Conditions
High-Temperature/High-Pressure Systems: Perform hot tightening after equipment has warmed up to compensate for preload loss due to thermal expansion and contraction.
Vibration environment: After running for a period of time, re-inspect whether the nuts are loose, and add locking washers or apply adhesive to prevent loosening if necessary.
