Flange sealing failure mainly stems from aging, compression creep, medium erosion and thermal cycle fatigue of the gasket between flange pairs. The sealing cushion gradually loses elasticity and compression resilience, the pre-tightening compression gap opens up, and process medium penetrates the flange joint to form external leakage. In serious cases, bolt tension fails due to gasket thinning, the flange face separates significantly, and massive medium spraying occurs, forcing system shutdown. This failure is extremely common at pipeline disassembled connection points and equipment inlet-outlet joints, being a frequent maintenance trouble point of heating pipeline systems.
1. Gasket Deterioration and Leakage Mechanism
After bolts are tightened, the gasket is squeezed to fill tiny gaps between two flange sealing faces and block fluid permeation channels. Under long-term high temperature, the gasket material undergoes irreversible creep deformation, permanent thinning and cannot rebound after pressure release. Thermal expansion and contraction cycles make the bolt pre-tightening force continuously decrease. Meanwhile, corrosive medium infiltrates the edge of the gasket, causing material swelling, dissolution and pulverization damage. The sealing interface loses effective compression seal, and pressure-driven medium overflows outward along the flange clearance. Flange surface scratches, deformation and warpage will further destroy the closed sealing belt and accelerate leakage expansion.
2. Typical Positions Prone to Flange Sealing Failure
Equipment inlet and outlet flanges and pipeline sectional butt flanges requiring regular disassembly;
Flange joints in high-temperature and temperature alternating sections with large thermal stress;
Flange connections adjacent to pumps and compressors suffering long-term mechanical vibration;
Flange faces exposed to corrosive steam and condensate with continuous medium erosion;
Large-diameter flanges with uneven bolt tightening force leading to partial pressure loss.
3. Core Factors Accelerating Gasket Failure
Mismatch between gasket material and working temperature & medium corrosion resistance;
Uneven bolt fastening torque resulting in local insufficient compression of the sealing ring;
Long-term creep aging without periodic replacement of vulnerable sealing parts;
Flange sealing surface scratches, pits and bending deformation damaging the gasket;
Thermal stress and vibration continuously attenuating bolt preload without secondary tightening.
4. Full-Link Prevention and Control Technical Measures
① Select gasket materials matching temperature and medium conditions
Adopt flexible graphite, PTFE composite or metal wound gaskets suitable for high temperature and corrosion.
② Implement cross symmetrical torque bolt tightening
Tighten bolts diagonally in several passes with torque wrench to ensure uniform compression.
③ Formulate fixed cycle gasket replacement maintenance plan
Mandatorily renew sealing gaskets during system major overhaul to avoid aging failure.
④ Protect flange sealing surfaces during disassembly and assembly
Prevent scratches and impact damage; repair deformed flange faces by machining when necessary.
⑤ Perform secondary torque reinforcement after initial heating startup
Compensate pre-tightening force lost from initial thermal shrinkage and gasket creep.
5. Prevention Effect Comparison Table
表格
| Installation & Maintenance Mode | Flange Leakage Risk | Application Suggestion |
|---|---|---|
| Random tightening + ordinary rubber gasket + no regular replacement | Short-term aging leakage and flange gap spraying | Replace with suitable gasket and standardize torque fastening immediately |
| Torque cross fastening + matched sealing material + periodic replacement | Effectively avoid flange interface leakage | Standard construction and maintenance specification |
| Metal spiral wound gasket + dual reinforcement + anti-loose bolt measures | Extremely low sealing failure risk | High temperature, vibration and corrosive environment preferred scheme |
Conclusion
Flange gasket sealing failure of 316 stainless steel heating tubes is caused by material creep aging, medium erosion, uneven compression and thermal vibration leading to loss of sealing compression. The core control methods are selecting compatible sealing materials, standardizing symmetrical torque assembly, protecting flange sealing surfaces, arranging regular replacement and supplementing pre-tightening force after temperature rise. Strict management of installation process and overhaul maintenance can eliminate production shutdown and safety risks brought by flange leakage of heating pipelines.
