Punjab Newsline Network
Saturday, 31 July 2010
By Jagvir Goyal
Chimney Failures: A setback to Indian Power Sector
Recent failure of tall RCC Chimneys, one after another, in India has caused a severe setback to ambitious capacity addition plans of the country!
On July 29, 2010, a part of the 275 metre high RCC Chimney being constructed for 2 X 500 MW thermal power plant at Bhusawal in Maharashtra collapsed, burying many people under the debris. The chimney was being constructed by Gammon India Limited, known to be a leading construction company of the country. The two units of this thermal power plant are scheduled to be run for trial operations in August, 2010 and December, 2010. Now the fate of one of the units is unknown. Clearance of debris, ascertaining the reasons behind chimney failure, restoration of work at chimney site and its completion may consume a lot of extra time. Above all that, the big question, whether the chimney is safe or not to serve the power unit for its designed life lurks in the minds of project authorities!
In May, 2010, a 210 m high tall RCC chimney collapsed at Parichha, near Jhansi, in UP. The chimney couldn’t withstand high wind velocities and went down over more than 40 workers, having their lunch under its shadow. The chimney was recently constructed by National Building Construction Company, NBCC, another major giant in construction sector, for a 500 MW power plant being set up by UP Power Corporation Limited. Now, the operation of the two power units to which the chimney was serving as a twin-flue chimney stands suspended for an indefinite period. Suggestions are afloat to utilize the rotor of Parichha Thermal power plant for Chanderpur Thermal power plant where also, power generation of an unit stands stopped since May 7 due to occurrence of some damage to its rotor.
In September, 2009, an RCC Chimney of a 2 X 600 MW power plant being set up by Bharat Aluminium Company limited (BALCO), a subsidiary of Sterlite Industries limited, at Korba near Raipur in Chhattisgarh state had collapsed, killing scores of workers under its debris. The incident had sent shock waves all over the world. The setting up of the 1200 MW power plant had been assigned by BALCO to Shandong Electric Power Corporation Limited, a Chinese company who had further entrusted the construction work of 275 meter high chimney to Gannon Dunkerley Company Limited.
India has already mastered the art of tall chimney construction. Many tall RCC chimneys are now dotting Indian map, a number of them constructed and completed in record short periods. The equipment is available, the materials are available, skilled manpower is available and the design modules are available. Then why all these failures, one after the other?
The design of each such chimney that fails needs to be checked thoroughly, specially against occurrence of resonance phenomenon under high velocity storm conditions. Such a phenomenon occurs when more than one chimneys are constructed in a thermal project and their frequencies are not mistuned. If the design of chimneys is found safe then clearly, lack of supervision, use of sub-standard materials in construction, non-adherence to the quality control norms and inconsistent checking procedures are behind all these failures.
Chimneys are special structures and need special attention during their construction. Their construction technique is special which requires the concrete to be specifically designed to meet certain of its requirements. During construction of chimneys, a sharp eye has to be kept on verticality, tilt and twist of chimney. One factor ignored and a chimney may come falling down!
A power unit can not be commissioned unless its chimney has been completed and is available to pass the thousands of tones of smoke at a designed height in the atmosphere. Stringent environmental pollution prevention norms have increased the minimum height of chimneys to plus 200 metres, that is more than 3 times the height of Qutab Minar. How can engineers go lax in construction of such important structures?
A plus 200 metre high twin flue chimney consumes more than 2 years for its completion. India, planning to add 100,000 MW to its power map by the year 2012, can’t afford to delay the commissioning of its power units by such a long period!
-Er.Jagvir Goyal is author, Books on Tall Chimney construction