Flange sealing failure primarily originates from gasket creep deformation, medium erosion, aging deterioration and fatigue damage under alternating temperature and pressure. The sealing gasket permanently loses rebound elasticity, the bolt pre-tightening force declines gradually, and gaps emerge between flange sealing faces, resulting in outward leakage of process medium. In severe cases, bolt tension fails due to excessive gasket thinning, flange separation and large-area medium ejection, forcing emergency shutdown of the whole system. Such defects frequently occur at pipeline segmented joints and equipment inlet and outlet connecting flanges, ranking among the most frequent maintenance faults of heating pipeline systems.
1. Deterioration and Leakage Mechanism of Gaskets
After diagonal bolt tightening, the gasket is compressed to fill micro gaps between two flange sealing surfaces and block fluid penetration channels. Under long-term high-temperature working conditions, the gasket material produces irreversible creep thinning and cannot rebound after stress relief. Periodic thermal expansion and contraction reduce bolt fastening force continuously. Meanwhile, corrosive medium invades the gasket edge, causing swelling, dissolution and pulverization of the sealing material. Once the effective compression seal fails, pressured medium overflows along flange clearances. Scratches, pits and warpage deformation on flange surfaces will destroy the complete sealing belt and accelerate leakage expansion. Unlike weld leakage caused by inherent processing defects, this failure belongs to performance degradation of wearing sealing parts during service.
2. Typical Positions Susceptible to Flange Sealing Failure
Equipment inlet/outlet flanges and pipeline butt flanges requiring periodic disassembly and overhaul;
Flange joints in high-temperature alternating temperature zones with remarkable thermal stress variation;
Flange connections adjacent to pumps and compressors enduring persistent mechanical vibration;
Flange surfaces exposed to acid mist, condensate and corrosive volatile gas erosion;
Large-diameter flanges with uneven bolt tightening torque leading to local insufficient compression.
3. Core Inducing Factors Accelerating Gasket Failure
Gasket material mismatches operating temperature and medium corrosion resistance;
Non-standard one-pass bolt tightening without diagonal symmetrical torque control;
Long-term operation without scheduled replacement of aging and fatigued gaskets;
Flange sealing surfaces scratched, dented or deformed during disassembly and assembly;
No secondary torque reinforcement after initial heating startup to compensate stress relaxation.
4. Full-Process Prevention and Control Technical Measures
① Select gaskets matched with working conditions
Adopt metal wound gaskets, flexible graphite or PTFE composite gaskets resistant to high temperature and corrosion.
② Implement multi-pass diagonal cross tightening with torque wrench
Ensure uniform compression on the whole sealing ring to avoid local pressure deficiency.
③ Formulate fixed overhaul replacement cycle for vulnerable gaskets
Mandatorily renew all flange gaskets during system major maintenance.
④ Protect flange sealing faces strictly during disassembly
Repair or machine flat deformed flange surfaces to guarantee intact sealing contact surfaces.
⑤ Carry out secondary torque fastening after temperature rise
Make up for pre-tightening force lost from gasket creep and thermal shrinkage.
5. Prevention Effect Comparison Table
表格
| Installation & Maintenance Mode | Flange Leakage Risk | Application Suggestion |
|---|---|---|
| Random tightening + ordinary rubber gasket + no regular replacement | Rapid aging leakage and flange medium spraying | Replace qualified gaskets and re-tighten according to torque specification immediately |
| Torque cross fastening + matched sealing material + periodic renewal | Effectively avoid flange interface leakage | Standard construction and maintenance specification |
| Metal spiral wound gasket + double torque reinforcement + anti-loose bolts | Minimal sealing failure risk | Preferred plan for high-temperature, vibration and corrosive environments |
Conclusion
Flange gasket sealing failure of 316 stainless steel heating tubes results from gasket creep aging, medium corrosion, uneven compression and thermal vibration leading to loss of sealing compression. Core control methods include selecting compatible sealing materials, standardizing torque assembly technology, protecting flange sealing surfaces, arranging periodic replacement and supplementing pre-tightening force after heating. Strict management of installation procedures and overhaul maintenance can eliminate production interruption and safety hazards caused by flange leakage of heating pipelines.
