 On 1st November 2017, the NTPC had its biggest accident ever when a boiler furnace exploded at the Unchahar thermal power plant in Uttar Pradesh. The death toll from the explosion has risen to 37 while more than 80 people have been seriously injured. Sources say that unit number 6 of the plant where the boiler exploded was put under commercial operations hurriedly on 30th of September 2017 when even the trial operations were not over. It is alleged that the hurry was because the Prime Minister was supposed to inaugurate the unit on 9th November. The question is how could this boiler explode when both the BHEL which built the unit and the NTPC are familiar with these units for the past 40 years or more. Let us look at the sequence of events leading to the blast as pieced together by news click from various sources. This is a boiler and this is the bottom ash handling system from where the non-combustible residue is released as hot ash. According to sources, there was a problem of clinkering taking place in the boiler. Clinkering is when the ash becomes solidified almost like blocks of cement. The clinkers choked the bottom ash hopper leading to a huge buildup of ash inside the boiler. As a result, the pressure inside the furnace started increasing. So, the NTPC officials tried to bring down the load. At the same time, they attempted to remove the clinkers manually by inserting steel rods through the manhole doors and the bottom ash hopper, a process known as double poke. It is crucial to note here that at this point, it appears the NTPC officials bypassed the boiler protection by disabling the master fuel relay trip which cuts off fuel supply when the pressure gets very high because they wanted the boiler to keep running. As a result of the double poke, huge mass of clinkers fell down creating unstable conditions inside the boiler because of large pressure fluctuations. This led to the water walls being cracked and unburned coal particles got carried over to the rear pass of the furnace. In the rear pass, the unburned coal particles caught fire leading to an explosion in the economizer. Hot flue gas, ash and steam came out of the economizer area causing extensive burns to the 300 odd people who were working in the vicinity of the boiler. Why was the boiler protection bypassed? Why were there so many workers around the furnace? Is it because work on the unit was still pending, as sources say? Why was the unit put under commercial operations when it was not yet ready? Only the NTPC has the answers.