Effects analysis of forced cooling rate on microstructure, tensile strength and hardness of superheater tube in pulverized coal boiler

The duration of down time for planned and unplanned outages have potential impact to decrease the availability of power generation. Therefore, the duration of downtime is expected to be as short as possible. According to Pareto Loss Output Data of FTP-1 Power Plant at 2016-2017, boiler leakage still be the top ten problems that often happens. Cooling process in boiler maintenance play an important role related to downtime duration. In addition to natural cooling, boiler forced cooling can be used to minimize the downtime. This research is conducted by modeling and simulation the rate of boiler cooling using CFD software. Cooling time simulation obtained from the modeling result. The superheater material was heated using laboratory Ash furnace up to 540°C and cooled using temperature controlled afterwards, according to the modeling results. Furthermore, microstructural analysis, tensile strength and hardness testing were carried out. The result shows that the cooling rate is higher with the use of forced cooling than natural cooling. The microstructure results show the effect of natural cooling and forced cooling with 20% and 40% FD fan resulting in ferrite and pearlite microstructure with grain size 3.37 µm for natural cooling and 3.89 µm and 4.22 for forced cooling with FD Fan 20% and 40%. Effect of boiler cooling on hardness and toughness criteria (tensile strength and elongation) decreases as the cooling rate increases when forced cooling applied.