Electricity utility Eskom has indicated that its full summer plan will be reviewed in light of a catastrophic failure of the 10 000 t central coal storage silo at its Majuba power plant at 13:12 on Saturday November 1.

Periods of load-shedding are also possible until the end of March 2015, owing to the need to persist with a maintenance catch-up programme during the period.

Following the catastrophic silo failure, group executive for sustainability Steve Lennon indicated that the challenge for the summer period would be “to ensure that there was sufficient generation capacity throughout the day, as we continue with our maintenance plan and focus on reducing unplanned outages”.

Lennon stressed, though, that load would be shed should it be necessary to protect the power system from total collapse. He said that Eskom was acutely aware of the economic and social costs of load-shedding and would, therefore, only “take as much as we need and as little as possible”.

It would also continue to draw on its expensive diesel-fuelled open cycle gas turbines in the Western Cape, as the economic cost of load-shedding was “ten times” that of the cost of producing power at the facilities.

The Majuba incident pushed an already constrained power system “over the edge”, which resulted in over 1 000 MW (stage two) of load being shed on November 2.

It was also likely to have consequences for the maintenance programme, as Eskom had to place all planned maintenance on hold while it dealt with the crisis.

Newly appointed CEO Tshediso Matona said that short-term measures had also been introduced to restore five of Majuba’s six units to partial load, while the sixth under went maintenance.

Mobile coal feeders had been introduced along with additional front-end loaders to shovel coal at the stockyard onto trucks that would deliver coal to conveyors that feed the units’ coal bunkers. An initial rate of 15 loads an hour was envisaged at a single feeder point, which was likely to be doubled at a later stage.

However, neither of the other two silos on site would be employed until Eskom was satisfied that they were structurally sound, with initial investigations of the central silo, which had been constructed in 1994 and visually inspected in September 2013, showing worrying signs of reinforcing-steel bar corrosion. The silo was built in 1994, was independently inspected in September 2013, and was meant to have a design life of 50 years.

Nevertheless, Eskom was viewing the collapse as an “isolated incident”, stating that the first sign of structural weakness was only detected by a conveyor maintenance crew less than an hour ahead of the collapse.

The crew, which was evacuated, detected coal falling from a crack about 30 m up on the wall of the 40 m silo’s concrete structure. The crack was detected at 12:30 on Silo 20 and the collapse, which was recorded by cameras on site, took place at 13:12.

However, trade union Solidarity disputed this, saying that Eskom had been aware of structural problems with the silo for months and accused the company of negligence. The utility denied the allegation.

In a parallel intervention, Matona reported that Eskom had appointed a recovery team, led by executive Dan Marokane, to restore full operations at Majuba over the medium term. No timeframe was given as to when the 4 110 MW would be returned to steady-state operations.