Failure investigation of a boiler bank tube from a 77 × 2 MW coal based thermal power plant in the northwest region of India

Abstract

The failure of industrial boilers has been a prominent feature in fossil fuel fired power plants. The contri-bution of one or several factors appears to be responsible for failures, culminating in the partial or complete shutdown of the plant. The use of high sulfur and ash containing fuel, exceeding the design limit of temperature and pressure during operation, and poor maintenance are some of the factors, which have a detrimental effect on the performance of materials of construction[1-4]. Among the many forms of corrosion mechanisms operating in tube failures in different parts of the boiler, ash corrosion and galvanic corrosion were the prime failure mechanisms predominantly found in bank tubes which arise due to use of low quality feed coal as fuel and poor cleaning proc-edures, respectively [5,6]. These types of failures are manifested by the accumulation of ash deposits on the fireside, which impart excessive fireside heat input and accumulation of corrosion products on the waterside of the tube [7], which induce localized corrosion. In the present paper, a comprehensive analysis of a boiler bank tube failed in one of the captive power plant of 77 x 2 MW capacity located in the northwest region of INDIA is presented.