Failure analysis on converter cooling system blocking of wind turbine

•The blockage failure of the converter cooling system of the wind turbine has been analyzed.•The radiator channel of the cooling system has been corroded, and the corrosion product blocked the coolant outlet of the radiator plate.•The radiator channel has corroded by the fluorine solution, and the pitting corrosion and inter-granular corrosion occurred.•The fluorine-containing material comes from the sealant, which dissolves into the cooling liquid to form a corrosive solution, and causes corrosion to the radiator channel.•The incompatibility between the coolant and the sealant is the root cause of corrosion and blockage of the radiator. This paper analyzed the blockage failure of the cooling system of a wind turbine. The cooling system was designed to cool the converter. During the trial operation, abnormally high temperatures occurred in several cooling systems. Meanwhile, the hoses of aluminum radiators in these cooling systems were blocked or burst. In order to analyze this failure, composition of the blockage, physical and chemical indicators of the coolant, composition of the radiator surface, and the composition of sealants were tested. Thereafter, the failure mechanism based on the test results was discussed. The results showed that the substances that cause the blockage of the cooling system are Al, Al(OH)3, and Al2(OH)2.76F3·24H2O, which are all corrosion and oxidation products of the radiator. Improper selection of coolant and sealant is the root cause of this blockage failure. Finally, this paper proposes solutions to similar problems.