Investigations are underway to determine why a section of the Kusile unit 1 flue gas duct (the equivalent of a chimney in a household) failed.

This is according to a media statement by Eskom, which says the duct exiting the sulphur dioxide absorber failed on the horizontal rubber expansion joint as well as the compensator (a bend to direct flue gas up the chimney and allow for thermal expansion of the chimney) while the unit was on forced shutdown for flue gas de-sulfuration recirculating pump repairs.

The power utility says the need to determine the cause of failure and to ascertain the extent of the damage, as well as the recovery scope of work.

Eskom adds that although they are uncertain at this stage, they expect the unit may remain offline for a few months. “This will become clearer over the next few weeks. Access to the area has also been restricted as part of precautionary measures.”

The power utility explains various specialist stakeholders, including the original equipment manufacturer, are in discussions to establish the best course of action to restore the plant as quickly as possible.

The failed section of the unit 1 flue gas duct (FGD) is located inside the flue chimney. “The ducts are made from steel sections welded together and surrounded by a windshield, which is made of reinforced concrete that also houses the unit 2 and unit 3 flue gas ducts,” their statement reads.

Unit 2 was off load at the time of the incident while unit 3 was generating electricity.

“Unit 4 of which the FGD duct is housed on a separate flue chimney, is currently on load generating full load to the national grid. As part of precautionary measures put in place, the return to service of unit 2 has been put on hold while unit 3 continues to run at stable load,” Eskom concludes.