Rupture of water wall tubes in a 35T power station boiler
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This post was last edited by Amun God on 2020-4-15 at 14:58. In power station boilers that have been in operation for over a decade, the water wall tubes within 1–3 meters of the bottom of the furnace always suffer severe wear every time the boiler is shut down. Thickness measurements show that many of these water wall tubes need to be cut out and replaced with new ones. This year, while the boiler was in operation, the operators noticed a sudden change in operating conditions. After shutting down the boiler, inspections revealed that this time the water wall tube that burst was one located 35 meters above the bottom of the furnace. I would like to ask if anyone has encountered similar situations.
Reasons for the rupture of boiler water wall tubes: 1. Poor quality of boiler feed water, inadequate chemical monitoring, and failure to carry out blowdown as required, leading to scaling and corrosion inside the tubes. 2. During maintenance and installation, the pipes get clogged with debris, resulting in poor water circulation and causing overheating and pipe rupture. 3. Defects in manufacturing, substandard materials, improper pipe installation, or poor welding quality. 4. The boiler is severely underwatered. 5. Improper start-up and shutdown procedures, or prolonged operation at extremely low load levels, lead to a deterioration in the local water circulation. 6. Severe wear of the water wall tubes. Remedial measures: 1. If the water wall tubes burst and it becomes impossible to maintain the drum water level, shut down the boiler immediately while keeping the induced draft fan running. 2. If the damage is severe and the boiler’s steam pressure drops rapidly, and increasing the water supply still fails to maintain the water level, stop feeding water. 3. Once the steam in the furnace has been completely exhausted, stop the exhaust fan. 4. If the damage to the water wall tubes is minor, the water loss is not significant, the normal water level in the steam drum can be maintained, and the accident is not likely to worsen rapidly, it is possible to reduce the evaporation rate slightly to allow the plant to operate for a short period of time, while simultaneously bringing in a backup boiler for use. At the same time, the relevant supervisors should be informed, awaiting instructions to shut down the plant. If the accident continues to worsen, with increasing noise and water flow, posing a threat to adjacent pipes, the boiler must be shut down.
Issues 4, 5, and 6 mentioned above may not exist at all; in most cases there is high load, with continuous operation for 8 months. The problem here is that the explosion occurred at a height of over 30 meters above the bottom of the furnace. The incident should be treated as a major equipment accident; those involved will face fines of up to 5,000, or at the least 2,000. Alas, what can be done? ?
It is recommended to provide the type of furnace and its exact location, as well as to check the furnace tubes that are attached.
Apply a wear-resistant coating in combination with the measured wall thickness data of the water wall tubes! If there isn’t enough investment and problems arise, it’s the same everywhere when it comes to holding the grassroots level accountable.