The sixth unit of Eskom’s Medupi power station is going to be commissioned and connected to the grid, despite tests showing that it is not working as it should.
This is yet another alarming development at Medupi, which has been feted by Eskom as the solution to South Africa’s power woes, but which is already two years late and R40-billion over budget.
Each of the six units at Medupi will provide 800 MW of power, boosting the 40 000 MW national grid by 12%.
But the problem at Unit 6 is that excessive dirt has been found in the steam which is being blown out of the boilers installed by Mitsubishi-Hitachi.
Roman Crookes, Eskom’s managing director on the 900ha construction site in Limpopo, said that blow-through tests — in which the steam quality and velocity is tested — had been expected to take two weeks.
But Crookes said these tests had been going for almost two months now, and the steam was not yet at the standard the unit was designed to use.
In addition to the excessive dirt particles, the steam isn’t coming out of the boiler fast enough to meet Alstom’s specifications.
In its contract with Eskom, Alstom stipulated that for the turbines to spin as required, the steam must reach a velocity of 200m/second, considerably faster than the current 182m/second.
According to Crookes, this is actually a good thing since it will slow down the speed at which the dirt particles leave the boiler and hit the massive spinning blades. The lower velocity would not “compromise the machine”.
However, senior engineers at Medupi, who spoke on condition they wouldn’t be named, said last month that the dirt and velocity problems were more serious than Crookes was making out. The turbine “will be destroyed”, one said.
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