• This explainer video shows what goes on behind closed doors when Eskom repairs its boiler tube leaks.
  • Such leaks were in part to blame for the most recent bout of load shedding.
  • With over 650 km of tubing in a modern boiler, there's a lot of ground to cover.
  • Repairers need to pass through holes the size of a car wheel to access the boilers.
  • They're mainly there repair leaks caused by fly ash erosion, which is due to poor quality coal. 

This video posted on EE Publisher’s YouTube channel shows how incredibly complex Eskom’s power stations are, and why fixing a boiler is no small job.

(You can fast forward to 11:42 for the good stuff.)

While Eskom has managed to stave off load shedding so far this week, experts warn that South Africa will struggle with electricity provision for many more years to come, given a myriad of problems at the utility, including shoddy maintenance.

Boilers at coal-fired power stations are central to the electricity system, converting the chemical energy in coal to kinetic energy via steam piped to the turbo generators, where it comes electrical energy.

With over 650 kilometres of tubing involved, there's a lot of ground to cover in maintenance, or when things go wrong.

Eskom
A repairman enters a boiler. Source: YouTube

For repairers to get to a leak, the boiler needs to be shut down and cooled with force-draft fans.

The only way to repair them is for workers to enter the boilers through man holes the size of a car wheel. In some cases, good tubes need to be cut in order to access the broken ones and then re-welded. Each weld is then x-rayed as a quality check before being signed off. Gas tests need to be conducted before the boilers are switched on again.

The difficulty with boiler tube repairs is that they are hard to get at. Boilers are constructed from the top down, on site, so they can not be replaced. Modular replacement is also not possible because if heat exchangers are to be replaced as they would have to be cut out tube for tube.  

The coal burnt in South African power stations now is of poor quality, and highly abrasive ash adds to wear.

Eskom
Inside an Eskom boiler. Source: YouTube


When a boiler runs a leak, high temperature water or steam flows out at an extreme pressure. In Eskom 70% of tube failures result in a forced outage, with boiler tube failures being the leading cause in failure of generation.

Fly ash erosion is the leading cause of leaks.

Eskom
Inside an Eskom boiler. Source: YouTube

While the footage dates back to 2011, the repair process is still relevant today, says energy expert and and investigative editor at EE Publishers, Chris Yelland.  

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