(1) Material defects of the pipe itself Under the corrosive medium and high temperature conditions, overall corrosion and local corrosion occur; the foreign matter accumulation in the pipe causes pitting corrosion.
(2) The interface between the pipe and the tube plate is made of strength welding and strength expansion. The gap or stress is formed due to the expansion and relaxation under the severe working conditions. The medium concentration in the gap is higher than the concentration of the medium on the shell side, causing crevice corrosion; In the transition zone between the unexpanded tubes, there is a large tensile stress on the inner and outer walls of the pipe, which is easy to produce stress corrosion cracking; local stress concentration occurs at the pipe and the baffle, and the gap exists, the corrosive medium is concentrated, and the joint is prone to stress corrosion.
(3) The weld seam and heat-affected zone of the shell are not prone to corrosion under high temperature and corrosive medium environment.
(4) The electrolytic potential of the material of the shell and the baffle is different. The potential of the material of the baffle is higher than that of the shell, and the medium of the shell is electrolyte, and the inner wall of the shell is electrochemically corroded.
(5) Most heat exchanger failures occur at the junction of the tube and the tubesheet. Failure of the joint may result in product failure and production reduction, environmental pollution, and even fire or explosion, resulting in forced shutdown of the unit. In recent years, the low stress damage caused by the shell-and-tube heat exchanger under the action of corrosive media has attracted great attention from domestic and foreign universities and engineers. Its seriousness is precisely because the damage occurs far below. Stress corrosion cracking is one of the types of low stress failure in the state of yield point stress. This damage often originates from tiny cracks and then penetrates deeply into the material, causing leakage or fracture. Stress corrosion damage is considered to be an extremely severe mode of failure because it occurs within the allowable stress range and occurs suddenly and without warning during use.
(2) The interface between the pipe and the tube plate is made of strength welding and strength expansion. The gap or stress is formed due to the expansion and relaxation under the severe working conditions. The medium concentration in the gap is higher than the concentration of the medium on the shell side, causing crevice corrosion; In the transition zone between the unexpanded tubes, there is a large tensile stress on the inner and outer walls of the pipe, which is easy to produce stress corrosion cracking; local stress concentration occurs at the pipe and the baffle, and the gap exists, the corrosive medium is concentrated, and the joint is prone to stress corrosion.
(3) The weld seam and heat-affected zone of the shell are not prone to corrosion under high temperature and corrosive medium environment.
(4) The electrolytic potential of the material of the shell and the baffle is different. The potential of the material of the baffle is higher than that of the shell, and the medium of the shell is electrolyte, and the inner wall of the shell is electrochemically corroded.
(5) Most heat exchanger failures occur at the junction of the tube and the tubesheet. Failure of the joint may result in product failure and production reduction, environmental pollution, and even fire or explosion, resulting in forced shutdown of the unit. In recent years, the low stress damage caused by the shell-and-tube heat exchanger under the action of corrosive media has attracted great attention from domestic and foreign universities and engineers. Its seriousness is precisely because the damage occurs far below. Stress corrosion cracking is one of the types of low stress failure in the state of yield point stress. This damage often originates from tiny cracks and then penetrates deeply into the material, causing leakage or fracture. Stress corrosion damage is considered to be an extremely severe mode of failure because it occurs within the allowable stress range and occurs suddenly and without warning during use.
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