Loadshedding again

In an impromptu press conference that took place on Sunday, the Eskom executive team said the "collapse" of one of its newest power stations, Majuba power station in Mpumalanga, has forced Eskom to cut power across the country and introduce new load-shedding schedules.

"By yesterday [Saturday] our system reserves were basically exhausted," said Steve Lennon Eskom’s sustainability group executive.

"There will be load-shedding today [Sunday] until 10pm tonight and certainly for next week. The risks are tomorrow [Monday] during peak hours six o’clock to eight o’clock [in the evening]; Wednesday six to ten o’clock [pm] and the whole of Thursday."

"Those are the risk periods," said Lennon, "and if anything happens between today and during the week, the load-shedding will change".

According to Thava Govender, Eskom generation group executive, the collapse of Majuba power station coal storage silo dropped output from 3 600MW to 600MW, causing an immediate shortage of 3 000MW.

The new group chief executive, Tshediso Matona, described it as a "significant event with major consequences". He said Eskom was very concerned about the collapse of the coal silo because "the design life of there silos is 50".

Cause of collapse
Eskom’s Majuba power station has six silos, all of which are connected to three coal conveyors – one coal conveyor for two silos. The three coal conveyors are fed from one access point. The collapse occurred at the main feeder, which cut supply from the three coal conveyors breaking the supply to the silos.

The collapse of the main access point not only cut off the supply to the coal conveyors but its debris fell on one coal convenor, cutting off access to two silos – silo three and four.

"We have now no way to get coal [directly] to the six units [silos]," said Govender, "but we have been managing to bring coal from the silo that was saved in units two and six on half load [300MW each]. That makes it 600MW, the impact is that we are 3 000MW short."

Govender said Eskom has started to use mobile feeders into the incline conveyers. He said Eskom needed 15 to 16 trucks an hour and four per minute to feed coal into the operating silos – silos one, two, five and six.

"If everything works well – in theory – then we should be alright. That’s how we’re going to replenish the stockpile," said Govender. He added, "Silos three and four are a problem because that’s where the silo collapsed, we can’t take mobile feeders to feed units three and four."

Matona said the collapse was unexpected as Majuba is one of the youngest power stations. The power station was constructed in 1994 but became fully operational in 2001. Matona said that during inspection, the findings were that the concrete structure was in good condition with some moderate cases of external physical damage and was categorised as low risk.

"Yesterday, all was running normally. At 12:30[pm] staff reported a visible crack, later followed by actual collapse. At 13:12[pm] silo 20 collapsed. No injuries reported station output immediately reduced from 3 600MW to 1 800MW and currently running at 600MW the situation has been evolving very rapidly, now sitting at 600MW," said Matona.

‘Isolated’ case
Acting group executive of technology Matshela Kaka said they were confident this [the collapse of the silo] was an isolated case. He said Eskom was concerned that the concrete was not adequate to maintain the pressure.

"We [executive team] spent the last 24hrs on sight. We are concerned by the corrosion we are seeing now which we could not have seen with the silo in operation. We are investigating why there is corrosion. Investigation should be concluded soon, our expectations is in next 3 months will be complete," said Kaka.

Eskom said the causes and costs of the collapse have not yet been determined.

Source: http://m.mg.co.za/index.php?view=article&urlid=2014-11-03-eskom-majuba-collapse-has-significant-consequences?ars=true&views=1&mobi=true&KEY=mgiupr8mjlo16jcppo5tlpa4f4#.VFcVaRlBvqA

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