Analysis on main causes of steam water pipe leakag

2022-08-06
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Analysis on main causes of boiler steam water pipe leakage

a) hydrogen embrittlement. Hydrogen embrittlement mainly occurs in the high load area of water wall tube. Before the accident, the pipe was carried out under the low pH acid condition, resulting in serious local scale corrosion at the fire side of the pipe, resulting in serious decarburization of the pipe inner wall and intergranular cracks, resulting in the reduction of the pipe strength and finally the brittle ring fracture of the pipe

b) overheating. The boiler heating surface tube exceeds the allowable design operating temperature, causing overheating of the metal, accelerating the creep speed of the tube and reducing the lasting strength of the steel, so that the service life of the tube will be broken early before reaching the design service life. The main causes of overheating are: deviation of combustion center, poor water circulation, scaling in the pipe, blockage of foreign matters in the pipe, misuse of steel, etc. It mainly occurs on Superheater and reheater. For example, in the early stage of production of No. 2 boiler, the over continuous tube explosion of the screen was caused by the blockage of foreign matters in the tube, and the over explosion tube of No. 1 boiler was overheated due to the upward movement of the combustion flame center. Grade II constructor

c) pipe cracking caused by blocked expansion of connectors or improper attached weldments. During boiler operation, especially during unit startup, shutdown and load change, the structure, material and temperature level of each heating surface are different, resulting in different thermal expansion. For example, new technologies and practical solutions introduced by experts, material suppliers and medical device manufacturers from around the world are not well considered in design, manufacturing and installation. When the expansion of the heating surface is blocked, it will greatly change the torque test force of the testing machine applicable to various products, Cause the heating surface to leak. Most of them occur on the first pipe connected with the sealing plate, channel steel and fixed rib plate. The pipe cracks due to the structural limitations of the above accessories, or the pipe cracks due to improper welding process between the pipe itself and accessories. Such as 200012 Main machine size: about 950*350*370mm. The water wall tube at the right front corner of No. 2 boiler was cracked twice in 2001. The low temperature superheater tube of No. 2 boiler leaked in 2001, which was caused by improper welding process

d) poor welding quality. Leakage caused by poor welding quality, most of which are installation craters. According to the statistics, the leakage caused by unqualified weld crater quality of sunshine company accounts for 80% of the capital construction and installation weld craters The main reason is that the construction unit does not strictly control the quality inspection, and the qualified rate of welded junction is low

e) soot blower blowing loss. During operation, the heating surface may be damaged due to problems such as inaccurate soot blowing angle, insufficient soot blowing stroke, stuck soot blower failure, internal leakage of soot blower valve, etc. There are a large number of soot blowers damaging heating surface pipelines in sunshine company, which seriously affects the reliable operation of the unit

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