Why are the furnace tubes damaged in operation of coal-fired boilers?

(Question details) Specific performance:

The wall thickness of several boiler tubes was significantly reduced in a large area, the remaining wall thickness was 2.0mm, and some furnace tubes were corroded and worn out. Furnace tube wall is covered with a thick layer of uneven scale, the surface of the scale is brick red and black, scale layer is loose, and it is easy to remove the inner wall of the furnace tube, after removing, the furnace tube wall covered with a layer of corrosion pits. There is a thin layer of brick red corrosion on the outer wall of boiler tube, some of which are attached with black adhesive.

Answer: Fault reason:

1. The boiler is seriously short of water.

2. Poor water circulation and uneven combustion.

3. The unqualified quality of the boiler water and undemanding chemical supervision make the inner wall of the pipe corrode and scale, causing the pipe overheat and reduction of the strength.

4. Due to the presence of impurities and scale, the furnace tube is blocked inside, leading to bad water circulation, causing the pipe wall to overheat and causing drum and cracks.

5. The thermal strength of the furnace changes too much, and the fire raising speed is too fast or the water discharging is too early.

6. The welding quality of the boiler is unqualified, or the quality is not up to the standard, or the pipe manufacturing is defective.

7. Improper installation of boiler tube, header and water cooling wall tube or insufficient expansion allowance will affect free expansion of pipe.

Trouble shooting:

1. If damage is serious, circulating water pump power is not enough, boiler water pressure quickly reduce, in this case furnace should be emergent stopped and reduce circulating water outlet flow, in order to keep boiler water pressure, keep the induced draft fan continues to run, remove furnace flue gas and steam boiler.

2. If furnace tubes are not damaged so serious, and water lost small amount, water pressure of boiler can be kept in an normal value, and situation does not quickly going worse, in this case boiler load can be appropriately reduced, and proceed by normal boiler stop processing, but if damage keep going worse, and can't proceed by normal boiler stop, then  furnace should be emergent stopped.