Effect of the Oxide Scale on Tube Boiler Remaining Life of a 600 MW Coal Power Plant

Boilers are the main system for converting combustion energy from coal into steam energy in power plants. The boiler is mainly composed of tubing in which water steam circulates to absorb heat from the combustion. Superheaters and reheaters are the tubings for increasing the quality of steam before entering the turbine and thus working at high temperatures and generally in the creep regime of the materials. In the present work, a study on the effect of the internal tube oxide layer on the remaining life of the tube is presented by using the secondary superheater tube (SSH) as the model case. The investigation began with analyzing non-destructive testing data, followed by sampling and laboratory analysis. The next step is to simulate the prediction of the remaining life due to the oxide layer. The thickness of the oxide layer grows about 300–900 µm. Tubes that only experience thinning, their life can exceed 200,000 h of operation. Still, if there is a combination of thinning and overheating due to oxide, the tube life will be 93% shorter. The probability of failure will be greater, around 97% if the boiler tube experiences thinning and material degradation. The results obtained can be applied as consideration for decision making in the life cycle boiler area for superheater and can then be used as a guideline for operation and maintenance in the world of power plants in maintaining reliability and controlling the life of the boiler tube.