Officials in India say the the death toll from the November 1 explosion at an NTPC thermal plant in Unchahar has risen to 43, with seven more deaths reported in the past week. Dozens of workers at the plant were injured when flue gases and steam were released from a 500-MW coal-fired unit at the plant during a maintenance operation. Several workers remain hospitalized, many with severe burns, according to local officials, who late November 10 said at least eight of the injured are in “very critical” condition.
India’s Power Ministry has a committee investigating the explosion at the Feroze Gandhi Unchahar Thermal Power Station in Uttar Pradesh state. The blast occurred in Unit 6 of the plant, a unit which was commissioned in March and had been operating on a trial basis since September. The six-unit, 1,550-MW Gandhi plant supplies electricity to nine states—Uttar Pradesh, Haryana, Himachal Pradesh, Jammu and Kashmir, Punjab, Rajasthan, Chandigarh, Delhi, and Uttarakhand—and employs about 870 workers.
Investigators have questioned whether a rush to put the new 500-MW unit into service at the plant may have contributed to the accident. According to ThePrint, an India news organization, a delay in beginning construction of the unit pushed NTPC to complete construction in 26 months, down from the 40 months originally scheduled after the project was announced in 2013. The new unit was synchronized to the grid on March 31 of this year, and began commercial power generation on September 30.
R.K. Sinha, NTPC group general manager for the Unchahar plant, told ThePrint “there was no pressure in running the unit … the trial was done in August and commercial production started in September. I know that the plant tripped on the day of accident and the alarm rang also. But the actual cause of explosion will be known only after inquiry.”
Experts with knowledge of the plant have raised questions about whether the plant was ready to be placed into service. Shailendra Dubey, chairman of the All India Power Engineers Federation, told local media a thermal plant usually begins commercial generation two months after synchronization to the grid, and said the six-month gap between synchronization on March 31 and commercial startup in September shows “the plant was incomplete” when it was initially synchronized.
NTPC has admitted a commercial operation declaration (COD), the formal regulatory approval for the plant, was provided by the Central Electricity Authority before the plant was ready for service. V.K. Singh, a coal handling plant manager for NTPC at a plant in Kanti, Bihar, and also president of the Association of Power Executives (APEX), said “The ash handling system and the dry ash evacuation system [at Unchahar] were not complete, and it must be investigated how the COD was given for an incomplete plant.”
Investigators say there were 311 workers in Unit 6 at the plant at the time of the explosion, and have wondered why so many were in the area when only a handful would have been required for the maintenance work.
A government investigative panel was created November 6 by order of the Power Ministry, under a provision of the country’s Electricity Act 2003. It is led by P.D. Siwal, a thermal power expert from the Central Electricity Authority (CEA). The Power Ministry said it wants a report from the committee within the next month. The agency also asked the committee to “fix responsibility for lapses, if any,” and “to suggest remedial measures to avoid recurrence of such incidents in future.”
NTPC, the nation’s largest utility, has its own group investigating the accident, led by S.K. Roy, the company’s executive director of operations. The National Human Rights Commission has issued a notice to the government of Uttar Pradesh, asking for a “detailed report” on the incident from the chief secretary by mid-December.
An investigative group from the Uttar Pradesh labor department on November 3 said “gross negligence” on the part of NTPC led to the blast, although that charge has been challenged by government officials as premature.
NTPC officials involved in the investigation have said the accident occurred as workers were trying to remove bottom ash from beneath the furnace in the boiler unit. Pressure inside the affected unit allegedly shot up to 70 times its normal level in just a few minutes, and an emergency shut-off mechanism apparently failed to work. The pressure caused a section of economizer ductwork to fail, resulting in the explosion that released gas and steam onto the workers.
India’s NDTV on November 3 said NTPC officials have admitted that engineers were aware of the ash problem and were trying to clean the unit without shutting it down.
Jagmohan Singh, deputy director of the labor department, on November 3 told the Hindustan Times his group “found the formation and accumulation of clinker [residue from burned coal] in the boiler duct and the lack of its poking as the main reason for the explosion.”
Other utilities in India also are reviewing safety measures at their plants in the wake of the blast. The Karnataka Power Corporation Ltd. (KPCL) on November 7 said it has established two committees to review and audit safety measures at its coal-fired power plants. KPCL operates three thermal plants: a 1,720-MW facility in Raichur, a 1,700-MW plant in Ballari, and a 1,600-MW generating station in Yeramaras.
KPCL said senior engineers at the plants have been told to review safety practices across the facilities and submit updated operating procedures by the first week of December.
Asian News International on its Facebook page posted a video taken by a worker using a mobile phone.
The death toll is among the highest from a power-plant accident in recent years. An explosion at a hydropower station in Siberia in 2009 killed 75 people, and there were 74 deaths reported in November 2016 from the collapse of a platform at a coal-fired power plant under construction in China. Officials said it is the worst industrial accident in India since 45 people were killed by the collapse of a chimney being built at Bharat Aluminum Co.’s Korba thermal plant project in 2009.
—Darrell Proctor is a POWER associate editor (@DarrellProctor1, @POWERmagazine).