Phenomenon:
--- Slight crack, welding pore leakage. Hiss of steam. And the feedwater flow would be increased slightly.
--- If serious, there would be a clear sound of explosions and jet. The furnace negative pressure would be changed to be positive and the feedwater flow would be bigger than the steam flow.
Reasons:
--- The boiler water or the feedwater quality is not in compliance with the standard for a long time. The local thermal resistance increased and because of the scale formation inside of the tubes.
--- There would be local overheating caused by the bad water recycle.
--- Pipes are not qualified, the welding quality is bad or the wall outside is of severe corrosion.
Treatment:
--- When the waterwall damage is not serious:
1. Add up the feedwater amount and maintain the drum water level. According to the specific conditions, it could operate with low load or stop the boiler according to the normal operating procedures/
2. If the combustion is not stabilized, the oil should be injected for combustion-supporting.
--- When the waterwall damage is serious, and the normal water level can not be maintained.
1. Emergency shutdown. And stop feeding water to the boiler.
2. Maintain the operation of the induced draft fan, and exhaust the boiler steam. If the lowering rate of bed temperature exceeds the allowed value, stop the induced draft fan.
3. After shutdown, remove the bed material as soon as possible.
4. Other operations should be carried out according to the normal shutdown operations.