Phenomenon:
--- There would be sound of steam spray, and the feedwater flow would be larger than the steam flow.
--- Steam negative pressure decreases or it changes to be positive. The overheated steam pressure decreased.
Reason:
--- Scale fouling of boiler inner wall. Or the heat transfer worsened because of the clogging of the pipe debris.
--- The outer wall of pipe corrosion or the high-temperature corrosion.
--- The steam temperature or the wall temperature is not in compliance with the standard for a long time.
--- Pipe quality is not qualified. Welding quality is not good or the ash blowing is not proper.
Treatment:
--- If the pipe bursting is not serious, it is allowed to operate for some time. But decrease the load appropriately and prepare for shutdown.
--- Serious pipe bursting.
1. The induced draft fan should be kept to be operated, and control the lowering rate of bed temperature not exceeds the rating.
2. Add small amount of water and maintain the normal water level.
3. Other operations should be carried out according to the normal shutdown procedures.