The blast at NTPC’s Unchahar power plant, in which the death toll rose to 30 on Thursday, may have been caused by the malfunctioning of boiler fans meant to maintain pressure inside the boiler.
Experts said this possibly led to a sudden surge in the pressure inside, almost 40 times more than normal, causing the boiler to explode.The National Disaster Response Force stepped up the evacuation of workers; by evening, 59 were reported to have suffered grievous injuries.
There were approximately 100 workers around the boiler when disaster struck. As per NTPC’s estimates, about 85 people in all were scalded.
Five critically injured workers, including two AGMs of NTPC, Mishri Ram and Prabhat Srivastava, were airlifted to a hospital in Gurgaon. NTPC regional executive director (north), Virendra Singh Rathi, said the department of energy had also approached the ministry of defence to provide aircraft to speed up movement. By late Thursday evening, seven more injured were shifted to Delhi.
Rathi confirmed that the committee to investigate the cause of the blast would probe the possibility of improper functioning of fans. He told that while one fan pumps air into the furnace, the other sucks the air out.
Rathi explained, “There should be a fine balance in the air movement inside the boiler for proper pressure. In case of any imbalance, the system trips and fans start reducing the pressure. In this case it does not seem to have happened.
We are waiting for the final inquiry report.” NTPC’s initial inquiry found that the ash duct evacuating the bottom ash too was not functioning properly. A huge piece of coagulated ash, or clinkers, appears to have bounced in the furnace, causing imbalance in the combustion and subsequently the pressure.
The 500-MW sixth unit of the 1550-MW plant was commissioned in March this year.