Failure Analysis and Performance Assessment of Tubular Air Heater at PLTU South Sumatra V

Abstract

Tubular air heater has a design operational lifespan limit. This lifespan limit, if not monitored and controlled, can accelerate any damage. Tubular air heater damage will result in tube failures that affect the boiler heat transfer system and emission control. This research aims to find out the root cause of tube failure. This research analyses the physical failure mechanism related to the material: chemical composition test, hardness test, tensile test, metallography examination, SEM-EDX examination, and x-ray diffraction analysis. The failure mode analysis concluded that the tubes were attacked by sulphuric acid condensation due to the air heater tubes temperature drops below the sulphuric acid dew point temperature. The existing tubes material is Corten Steel, which has good atmospheric resistance but low in the acidic environment. One thousand two hundred tubes replaced with ND Steel, the ideal steel for sulphuric acid-resistant and 3,986 tubes used carbon steel. There is no air heater performance degradation after tubes replacement, indicated after two weeks outages at high load. The leakage significantly decreases from 64% to approximately 19%.