What is the reason for the cracking of the smoke pipe of the WNSL fire tube boiler?

The cracking of smoke pipe is generally caused by insufficient cooling of pipe section. This problem is mainly caused by the following three points, which need to be implemented one by one.

① The length of the pipe section protruding from the weld exceeds the standard

GB / t16508 shell and tube boiler stipulates that when the flue gas pipe is located in the area with flue gas temperature greater than 600 ℃, the length of the pipe end beyond the weld shall not be greater than 1.5mm; When used in the area where the smoke temperature is not more than 600 ℃, the length of the pipe end beyond the weld can be enlarged to 5mm.

For our products, the smoke temperature in the reburning chamber is higher than 600 ℃, and the temperature in the front smoke box is lower than 600 ℃.

② Whether the water quality is qualified

Check whether there is scaling on the boiler flue pipe wall. The scaling causes insufficient cooling of the working medium to the flue pipe, leading to cracking of the flue pipe.

③ The pre expansion of smoke pipe fails to meet the requirements

The smoke pipe shall be pre expanded before welding to eliminate the gap. If the pre expansion of the smoke tube does not meet the requirements, there is a gap between the smoke tube wall and the tube plate. After expansion and welding, there are high residual stresses and small gaps at the nozzle of the flue gas pipe. These gaps generate capillary action, suck in some boiler water, and evaporate it below the height. In this way, the free NaOH solution in the water will remain in the gap after continuous inhalation and evaporation, and this concentrated solution will cause alkali corrosion to the adjacent metal subject to high residual stress. The corrosion crack is intergranular corrosion, which develops from the inside to the outside. It is not easy to find the appearance, has no obvious plastic deformation trace, and is most dangerous. So it is easy to cause cracking and leakage at the pipe end.

The above is Jiangsu Sifang Boiler's answer to this question. If you have any questions about other boiler related issues, please consult Jiangsu Sifang Boiler's online customer service or call 0516-85871846 or 0516-85532705. Jiangsu Sifang Boiler's professional technicians will answer your questions in time.