Failure Analysis of an Aqua Tubular Boiler Tube

摘要

In general, boilers are subjected to aggressive environmental conditions and, for this reason, there is a real necessity of controlling some parameters such as quality of input water, amount and types of addition agents used in the water, and operational conditions of the equipment (pressure and temperature). The lack of control of these and other parameters can cause loss of performance of the boiler by higher amount of fuel consumption, loss of efficiency, or even rupture of components, causing severe accidents. This study has as purpose the failure analysis in a pipe of the lateral wall of a boiler, known as aqua tubular, of an aircraft carrier flat top boat during a test in sea. The material of the pipes, according to preliminary information, is ASTM 192 steel, which is adequate for this kind of application. Through microstructural analysis in important regions for the study of this failure and earlier information about equipment operation, the cause of rupture of the pipe, which was changed only 50 h before the accident, was analyzed. It was observed that incrustations, corrosion pits in the walls of the pipe, and high temperatures together with microstructural changes were the probable causes of the pipe rupture. It can also be concluded that the analyzed failure had no relation with the quality of the material or the fabrication process of the component.