The causes of boiler tube rupture

Boiler tubes are critical components in boiler systems, tasked with carrying high-temperature and high-pressure steam or water. They are typically made from seamless pipes, valued for their strength and uniformity, or ERW pipes, preferred for cost-effectiveness and precision. A tube failure—whether seamless or ERW—can seriously compromise boiler safety and may even result in severe accidents. The reasons behind boiler tube failures are complex and multifactorial, involving material selection, design, manufacturing, operation, and maintenance. Below is a systematic analysis:

1. Material-Related Factors

Defects in materials: Inclusions, pores, or cracks in steel accelerate crack propagation under extreme conditions.

Improper material selection: If the chosen steel lacks adequate heat resistance, corrosion resistance, or strength, it cannot withstand the demanding boiler environment.

Material aging: Prolonged exposure to high temperature and pressure degrades toughness, ductility, and strength, increasing the risk of fracture.

2. Design Issues

Inadequate wall thickness: If thickness is not matched to operating pressure and temperature, tubes may fail under stress.

Stress concentration: Sharp transitions or small bending radii create localized stress points where cracks initiate.

Thermal expansion neglect: Poor allowance for expansion during heating can generate excessive internal stress.

3. Manufacturing Defects

Welding flaws: Incomplete penetration, porosity, or slag inclusions weaken weld joints and trigger cracks.

Cold working damage: Residual stresses or microcracks from cold bending or drawing can worsen under heat and pressure.

Improper surface treatment: Inadequate finishing or protective coatings expose surfaces to corrosion or weaken durability.

4. Operational Problems

Overpressure or over-temperature: Exceeding design parameters accelerates creep, oxidation, and structural deterioration.

Thermal fatigue: Frequent start–stop cycles or load fluctuations cause repeated expansion and contraction, leading to fatigue cracks.

Poor water treatment: Impurities, pH imbalance, or oxygen in boiler water cause corrosion, scaling, or hydrogen embrittlement.

5. Maintenance Deficiencies

Corrosion: Lack of timely treatment results in wall thinning due to oxygen, acid, or alkali corrosion.

Scaling: Deposits from untreated water reduce heat transfer efficiency, causing localized overheating and tube rupture.

Undetected crack growth: Small cracks left unrepaired will expand until fracture occurs.

Improper upkeep: Infrequent cleaning or delayed replacement of aged components accelerates damage.

6. External Influences

Mechanical damage: Collisions, scratches, or mishandling during installation/transport can become crack initiation sites.

Environmental corrosion: Exposure to moisture, acid rain, or corrosive gases accelerates wall thinning.

Vibration and shock: External mechanical stresses induce localized fatigue and eventual rupture.

Conclusion

Boiler tube failures are rarely caused by a single factor; rather, they result from the interplay of material quality, design, manufacturing accuracy, operational discipline, and maintenance practices. A systematic approach—starting with correct material selection, precision design, strict quality control, safe operation, and timely maintenance—is essential to ensure the long-term safety and efficiency of boiler systems.