Boiler Fans Might Have Caused The Blast Of Boiler Pipe At NTPC

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.

According to Rathi, the pressure inside the boiler, which should be maintained at barely five mm water columns (mmwc), shot up by over 40 times to around 250 mmwc. “That opened up what is called the economiser hopper, installed on one side of the boiler. Soon, hot flue gases started emanating and hit the workers who were working in that area,” he said.

In Lucknow, Union power minister R K Singh, who visited the plant, said the three member probe committee, which is to submit its report within 30 days, would look into all aspects — design, installation and maintenance — which could have caused the blast. Rae Bareli witnessed hectic VIP movement with Congress vice-president Rahul Gandhi leading the pack. He flew to his mother Sonia’s parliamentary constituency early on Thursday to meet the victims. Soon, Union minister Singh and UP energy minister Shrikant Sharma, too, reached the site and then the NTPC hospital to oversee the rescue and enquire about what caused the disaster. Sources said BHEL, which provided the boiler to NTPC, may also come under ambit of the inquiry.

The 500-MW sixth unit of the 1550-MW plant was commissioned in March this year.