What are the 14 causes of boiler steel pipe rupture and their prevention measures

Boiler steel pipe rupture refers to the rupture of water-cooled wall tubes, convection tubes, and economizer tubes in the heat exchange surface of a boiler during operation, caused by a combination of factors such as overheating, wear, and corrosion. This leads to leakage of high-temperature boiler water and prevents the boiler from operating normally.

Through years of theoretical accumulation and field practice, it has been found that boiler steel pipe rupture is mainly caused by fourteen reasons.

1. Poor boiler feedwater quality, lack of water treatment, or incorrect water treatment methods, including failure to perform blowdown treatment according to relevant regulations, causes scaling or corrosion on the inner wall of the boiler steel pipes. A major reason for this is that some boilers draw water from underground, which is high in hardness, sulfur, and iron content. Improper water treatment can easily lead to tube rupture, forcing a shutdown for emergency repairs and causing significant disruption to production and daily life.

2. During manufacturing, installation, and maintenance, stress concentration and decreased mechanical properties can occur at weld joints in boiler steel pipes. These critical areas of stress concentration and mechanical degradation can lead to boiler tube rupture, causing boiler failure and hindering the supply of production and domestic needs.

3. During boiler installation or maintenance, impurities may fall into the boiler steel pipes, causing blockages and impairing or completely disrupting water circulation.

4. Scale buildup on the inner walls of boiler steel pipes can create bridging, hindering water circulation.

5. Low water levels during boiler operation can also lead to poor water circulation, causing localized overheating, deformation, and even rupture of the pipelines.

6. In oil, gas, or coal boilers, improper nozzle angle adjustment during design and installation can cause overheating in some boiler pipelines.

7. Incorrect start-up and shutdown operations, exposure of boiler steel pipes to cold air, and excessively rapid or frequent thermal expansion and contraction of the boiler steel pipes can generate harmful stress.

8. Damage to the flue and combustion chamber baffles causes short-circuiting of flue gas, resulting in localized heat concentration in the boiler tubes and ultimately burning them out.

9. Corrosion-induced tube rupture and aging-related tube rupture typically occur in the economizer tubes on the tail-end heating surface. This is caused by acid corrosion due to excessively low exhaust gas or feedwater temperatures.

10. Excessively high local flue gas velocity occurs when the pitch of the boiler tubes on the heating surface and the distance between the tube banks and the furnace wall do not meet design requirements during installation and maintenance. This creates localized flue gas corridors between tube banks or between tube banks and the furnace wall, or when some boiler tubes deviate from their designated positions, causing ash accumulation and bridging on the boiler tubes on the heating surface. This leads to excessively high local flue gas velocities, increasing wear and overheating in those areas.

11. Due to careless construction, the furnace wall seals were not strictly sealed according to construction requirements, causing eddies at the leaks. This can lead to localized overheating or uneven heating of the pipelines. The leaks also increase the flue gas velocity downstream, damaging the tail heating surfaces.

12. High-temperature operation of boiler steel pipes is also a significant cause of boiler tube rupture. Overheating and over-temperature rupture occur because the mechanical properties of the boiler steel pipes decrease under excessive temperature. Under pressure, the tubes undergo plastic deformation, i.e., creep cracking, ultimately leading to rupture.

13. Environmental factors can also cause boiler steel pipe rupture. These include frequent boiler start-ups and shutdowns, drastic load changes, improper flame centering, primary and secondary air scouring of water-cooled wall tubes, and rapid cooling during shutdown. All of these factors create potential hazards for boiler steel pipe rupture.

14. Carbon dioxide or oxygen corrosion exists in the boiler heating system piping network or steam condensate piping network. When oxygen and carbon dioxide are present simultaneously in the boiler return water system, the corrosion of the system piping steel becomes more severe. Carbon dioxide makes the water slightly acidic, damaging the protective film on the pipes. As the oxygen content increases, large or small ulcers appear on the carbon steel equipment and piping of the heating system, accelerating corrosion. The result is that the return water or condensate turns yellow, red, or even soy sauce-colored, has a high iron ion content, and exhibits perforation in the steel pipes. This is the common cause of corrosion, perforation, and leakage in steam and condensate pipes. This is also why some newly built boiler carbon steel pipes have a service life of only 4-5 years.

Six Measures to Prevent Boiler Steel Pipe Bursts

To reduce and eliminate pipe bursts and ensure the needs of production and daily life, the following six measures are specifically implemented to prevent boiler steel pipe bursts:

1. Strengthen the management of water treatment and water quality monitoring, increase deoxygenation and iron removal equipment, and change from single-stage softening to two-stage softening to ensure that boiler water meets national standards, ensuring the safe and economical operation of the boiler.

2. Make full use of the maintenance time after boiler shutdown. Have an authoritative organization conduct a comprehensive internal and external inspection of the boiler to promptly identify and address any problems, ensuring healthy boiler operation.

3. Strengthen operational management, organize reasonable combustion conditions and appropriate flame centering, prevent cold air from blowing through boiler steel pipes, improve wear and corrosion prevention measures, and conduct proper blowdown.

4. After shutdown, promptly descale and clean the flue gas, and perform proper maintenance.

5. Appropriately increase the flue gas temperature (150-170 degrees Celsius recommended), balancing safety and energy conservation, eliminating energy waste, and preventing the generation of condensate at the tail end.

6. Add a high-efficiency boiler corrosion and scale inhibitor, BF-30a, to prevent scale formation on the boiler's metal surface in high-hardness water.