As the death toll in the explosion that ripped a boiler at the NTPC’s Unchahar plant in Rae Bareli two days ago climbed to 32 Friday, it emerged that barring three who were NTPC employees, the dead and injured were contract workers.
These workers included those working for firms such as Vijayawada-based Indwell, who were painting the boiler, and Kolkata-based controls and instrumentation company Powertronix, who were either working in the vicinity of the boiler or were called in to assist the process of de-choking the bottom hopper — the funnel-shaped bottom end of the boiler — by using rods to push out ash clinkers while the boiler was in operation, though running at a reduced load. Most workers were probably unaware of the dangers involved in the exercise.
NTPC Chairman and Managing Director Gurdeep Singh told reporters: “Around 80 people were affected due to this accident… 32 succumbed to injuries and 48 are under treatment.”
Sources said some 20-25 workers had been called in to assist in the the de-choking exercise when the accident happened. Usually, only 3-4 persons are present in the boiler zone. Sources said practically all these workers — either dead or injured — would be outside the safety net of an insurance policy that companies such as NTPC and Bharat Heavy Electricals Ltd (it supplied the boiler) offer to their own employees.
What seems to have precipitated the explosion was that someone opened a water channel in a bid to make it simpler to break the clinker pieces blocking the bottom opening of the ash hopper. This, sources said, could have backfired since the resultant steam would have added to the build-up of pressure in the boiler, triggering the explosion in a part called the economiser hopper which traps coarse ash and is located at a delicate joint in the boiler assembly.
In response to queries sent by The Indian Express, NTPC said only three of its employees were in the casualty list. A spokesperson for NTPC said: “Three employees (out of 80) that were affected because of this accident were NTPC employees. Remaining affected people were working as contract workers for the NTPC and the BHEL.” Don’t know if we’ll ever go back to work there: Victims of NTPC power plant blast
Asked how many of the contract workers were working for each of the two companies, the spokesperson said “it is difficult to differentiate between them and give separate figures as of now”.
According to the spokesperson, the ‘affected’ persons, who were working as contract workers at the accident site, would be eligible for compensation calculated under the Workmen’s Compensation Act, 1923 and announced by the NTPC, the Prime Minister and the UP Chief Minister.
Asked what were 80 people doing around the boiler, CMD Singh said: “There was this other work which was going on for cleaning and for painting and for cladding. These were some of the works that were going on in continuation after the COD also. It was the BHEL and their contractor was Indwell — these were the people who were working on the boiler and on the outside which is not in the operation of the boiler. But when this ash and air came out, they got affected by that. So, they were not involved in the operation at all.”
To a query if the operations team at the site decides whether it is necessary to shut the boiler or not for declogging, Singh said: “There is an operations engineer. There is a shift in-charge engineer over and above them. Then there is an operation in-charge. Then there is a GM (General Manager) and then head of the project. These are the people who would be in constant touch (with one another) and they will decide. This information does not go from the head office (in Delhi) whether to run the boiler or not… They are trained. They are experienced and they are the only competent people to decide.”
According to information gathered from multiple sources, the Unchahar 500 MW Unit No. 6 was running at a load of around 200 MW at 1536 hours Wednesday. Sources said bottom hopper de-ashing was being done by opening the manhole door at around 10 metres height on the boiler platform by an NTPC operations and maintenance team. The boiler was in manual mode of operation then.
While the workers succeeded in opening the 6-8 inch opening at the boiler bottom hopper, air rushed in from the bottom opening, with the result that pressure went up 40 times inside the boiler (from about -10mm to 350 mm in the mercury column). The resultant loss of vacuum, sources said, pushed the entire mass of unburned mass which, instead of burning in the flame chamber, went up and after crossing the superheater, exploded in a part called the economiser hopper.