Titanium heating tubes subjected to long-term high temperature and stable internal pressure will produce time-dependent slow irreversible creep deformation. The pipe wall is continuously stretched and thinned, partial pipe diameter bulges and expands. When the residual wall thickness can no longer bear the medium pressure, the pipeline undergoes sudden ductile rupture and medium ejection. Creep damage accumulates gradually in long-term continuous operation with no obvious early warning features, belonging to high-risk delayed failure for titanium pressure-bearing heating pipelines under high-temperature working conditions.
1. High-Temperature Creep Damage Mechanism
Titanium alloy maintains stable elastic deformation under pressure at normal temperature. When the operating temperature rises above the critical creep temperature, dislocation sliding and grain boundary migration occur inside the titanium matrix under constant tensile stress from internal medium pressure. Even if external load remains unchanged, the pipe wall will keep stretching and thinning over time. Areas with insufficient wall thickness or structural defects bulge preferentially, and stress concentration further speeds up the creep rate. As the effective bearing section continuously shrinks, the material ultimate strength fails to resist internal pressure, leading to instantaneous pipe burst. Different from thermal fatigue crack expansion caused by cyclic temperature fluctuation, creep deformation is a permanent slow deformation driven by constant temperature and static load.
2. Typical Positions Prone to Titanium Pipe Creep Burst
Thin-walled pipe sections with insufficient design safety thickness margin;
Blocked pipeline segments with poor medium circulation resulting in local heat accumulation and overtemperature;
Welded joints and heat-affected zones with uneven metallographic structure and weakened creep resistance;
Cold-bent elbows and shaped pipe fittings bearing both internal pressure and bending additional stress;
Rigidly locked fixed pipe sections where thermal stress cannot be released and superimposes tensile load.
3. Key Factors Accelerating Creep Failure
Long-term operating temperature exceeding the maximum allowable creep temperature of titanium material;
System working pressure persistently exceeding the design rated pressure without pressure limiting protection;
Internal scaling and sediment blockage leading to poor heat transfer and local abnormal overheating;
Surface indentation, scratches and processing dimensional deviation reducing the effective bearing wall thickness;
Cold forming residual tensile stress not eliminated by stress relief heat treatment.
4. Full-Link Preventive Control Technical Measures
① Configure temperature and pressure interlock protection
Set upper limit alarm and automatic interlock shutdown to forbid overpressure and overtemperature operation.
② Strictly inspect incoming material wall thickness
Screen out pipes with out-of-tolerance thickness to guarantee original pressure-bearing allowance.
③ Establish periodic pipeline cleaning mechanism
Remove internal scale and deposits to eliminate flow blockage and local heat accumulation.
④ Implement stress relief annealing for bent and welded parts
Eliminate forming residual stress and lower the total tensile load on the pipe body.
⑤ Carry out regular ultrasonic thickness inspection and appearance inspection
Monitor wall thickness attenuation and bulging deformation, replace components before reaching safety threshold.
5. Prevention Effect Comparison Table
表格
| Operation & Maintenance Mode | Creep Burst Risk | Application Suggestion |
|---|---|---|
| Long-term over-limit temperature and pressure + no regular thickness detection | Gradual bulging and sudden rupture during long-term running | Adjust working conditions immediately and organize overall thickness inspection |
| Operation within design parameters + regular descaling + periodic thickness testing | Effectively slow down creep deformation development | Standard specification for long-term high-temperature titanium pipeline operation |
| Post-processing stress relief + real-time parameter monitoring + scheduled pipe replacement | Extremely low creep burst hidden danger | Key high-temperature pressure heating equipment preferred scheme |
Conclusion
Creep burst failure of titanium heating tubes originates from slow plastic deformation of titanium matrix under sustained high temperature and static pressure, which causes progressive wall thinning and structural instability. The core prevention ideas are restricting operating parameters within design range, ensuring adequate wall thickness allowance, eliminating local overheating conditions, removing residual forming stress and dynamically monitoring thickness loss. Comprehensive management of equipment operation, processing technology and routine detection can effectively avoid major safety accidents caused by creep rupture of titanium heating pipelines.
