Fretting wear penetration failure refers to tiny relative reciprocating sliding occurring between titanium pipe body and pipe clamps, fixed supports, hanging brackets under pipeline vibration, medium pressure pulsation and thermal expansion displacement. The contact surface is repeatedly extruded and rubbed with micro-amplitude motion. The dense titanium dioxide passive film is continuously scratched and peeled off. Fresh metal matrix is exposed and immediately oxidized to form hard abrasive oxide debris. These particles aggravate abrasive cutting, gradually forming concave pitting pits at contact positions. As wear deepens along the pipe wall thickness direction, through-hole leakage finally appears. This failure mostly happens on fixed support positions of long-distance overhead titanium heating pipelines.
1. Passive Film Destruction and Cyclic Abrasion Mechanism
Titanium relies on the surface compact oxide film to achieve anti-corrosion performance, yet the oxide layer is thin and brittle. Under micro slip between two fastened contact surfaces, friction shear force tears the passive layer in tiny areas. Newly exposed titanium rapidly reacts with oxygen to produce titanium oxide wear particles. Hard particles are clamped between fitting surfaces, turning simple friction into three-body abrasive wear. Pitting damage keeps expanding in depth with long-term vibration cycles. Different from large-range flow scouring abrasion, fretting wear only concentrates on narrow contact lines or points, featuring localized pit-type thinning rather than uniform material loss.
2. Typical Positions Prone to Fretting Damage
Contact positions between pipeline outer wall and rigid pipe clamps, hoop fasteners and fixed supports;
Lap joint surfaces of multi-section combined brackets and titanium pipe outer skin;
Flange backing ring and bolt pressing areas with slight displacement under thermal deformation;
Overhead long straight pipes with obvious vibration during pump frequent startup and shutdown;
Buried pipeline sections where backfill soil compaction causes local squeezing and micro displacement.
3. Core Inducing Factors Accelerating Fretting Failure
Direct rigid contact between metal support and titanium pipe without any buffer isolation layer;
Pipeline fixing mode adopts fully rigid locking constraints with no reserved displacement allowance for thermal expansion;
Pump outlet lacks damping measures, and system pressure fluctuation triggers continuous pipeline resonance vibration;
Brackets are installed too densely, forming multiple fixed constraint points to amplify local extrusion stress;
External wind load and equipment operation vibration induce long-term tiny relative slip at supporting points.
4. Full-Link Prevention and Control Technical Measures
① Add non-metallic damping isolation gaskets between titanium pipe and all metal supports
Separate rigid contact fundamentally to eliminate fretting friction conditions.
② Adopt sliding support and spring damping bracket structure instead of fully fixed locking installation
Reserve displacement space for thermal expansion to avoid forced micro slippage.
③ Install pulsation dampers and vibration reduction components at pump inlet and outlet
Suppress system fluid excitation vibration source to reduce pipeline overall shaking.
④ Optimize bracket layout spacing to avoid over-constraint and stress concentration on single support point
Disperse pipeline load to multiple supporting positions evenly.
⑤ Regularly detach key support clamps to inspect outer wall pitting condition and replace aging gaskets
Repair early wear pits before perforation leakage occurs.
5. Prevention Effect Comparison Table
表格
| Installation & Vibration Control Mode | Fretting Perforation Risk | Application Suggestion |
|---|---|---|
| Rigid direct contact + full fixed locking + no vibration reduction | Deep pitting penetration leakage appears after long-term vibration operation | Add isolation cushion and transform fixed supports into movable damping type |
| Isolation buffer protection + reserved expansion displacement + front-end vibration suppression | Effectively cut off passive film abrasion and three-body particle wear | Standard installation specification for overhead titanium heating pipeline support system |
| Surface hardening anti-wear treatment + online vibration real-time monitoring + regular disassembly inspection | Extremely low contact point perforation and medium leakage hidden danger | Preferred scheme for outdoor long-span overhead chemical anti-corrosion heating pipe network projects |
Conclusion
Titanium heating tube fretting wear failure originates from micro reciprocating slip at pipeline supporting contact parts, which repeatedly destroys the protective passive film and forms abrasive particles leading to progressive pitting penetration. Core prevention methods include laying isolation gaskets to avoid direct rigid contact, using movable damping supports to adapt thermal deformation, eliminating system vibration excitation sources, optimizing support layout and conducting periodic disassembly inspection of vulnerable positions. Whole-process closed-loop management of pipeline support design, on-site installation construction and routine equipment maintenance can prevent leakage accidents and pipeline failure caused by fretting wear of titanium heating tubes.
