Investigation on Industrial Boiler Tube Failures in Steel Manufacturing Company in South Africa

Department of Mechanical and Industrial Engineering Technology, University of Johannesburg, Johannesburg, South Africa

Abstract

This study analyses recurring boiler tube failures at Company X, a steel manufacturing plant heavily dependent on steam for critical operations such as power generation, ironmaking, coke-making, steelmaking, water purification, and cold rolling. The plant runs four boilers fuelled by coke oven gas, blast furnace gas, and natural gas, but frequent stoppages have raised operational concerns. Failures observed include overheating, corrosion, oxygen pitting, scale formation, and tube cracking. Key contributing factors are identified as boiler feedwater quality, fuel composition, and the advanced age of the boiler tubes. Feedwater chemistry plays a major role in reliability and efficiency; deviations in parameters such as pH, conductivity, silica, hardness, iron, sulphates, and chlorides accelerate tube damage through scaling and pitting. Fuel quality also impacts performance, as coke oven and blast furnace gases contain corrosive compounds, particularly sulphur, which deposit soot on tube surfaces and increase external corrosion, requiring regular soot blowing. Aging is another critical factor. The boilers, installed in 1962, have exceeded their typical 23-year design life, operating for over 61 years without re-tubing. This raises concerns about tube wall thinning below the 2.6 mm minimum design limit. Overall, the study highlights how deteriorating feedwater quality, corrosive fuel gases, and tube aging collectively drive persistent failures at Company X.