12 January 2015
The first unit of the Medupi power station, unit six, is close to first synchronisation, according to power supplier Eskom.
The only step necessary before finally admitting steam to the turbine is to clean the boiler and associated pipework from all scale, welding residue and contaminants, which arise from construction.
It adds that “while the commissioning process towards the synchronisation is at an advanced stage, each of the remaining steps requires critical assessment of the inherent risks to both safety of people and the equipment integrity before proceeding to stage”.
Eskom has not given an official revised date for the first synchronisation of the unit; it missed the previous deadline of 24 December. “Before the end of February” has been targeted by spokesperson Andrew Etzinger. He said the 794 MW unit should be fully operational “by winter”.
It is the latest delay to the critical project, following various technical problems and labour disruptions. The original date for synchronising unit six was in 2011; this was moved to the end of 2013, then the end of 2014, and now to the beginning of 2015.
Technical issues, related to steam blow-through, have again been cited for the latest delay.
Initial cleaning is done by chemical flushing, which removes all major contaminants as well as any foreign objects. This is followed by steam blow-through: specific steam flow conditions are prescribed to achieve a minimum velocity and disturbance factors inside the various elements of the boiler. A number of steam blows have already been performed.
“While specified cleanliness levels have not been completely reached, a full technical risk analysis has been performed, which shows clearly that the consequences of admitting steam which is not quite clean enough are only slightly accelerated erosion of the high pressure or intermediate pressure turbine blades and possibly valve seats, during the first few days of operation. Thereafter, stable, reliable and predictable operating conditions will be achieved,” Eskom explains.
It will take several months for the unit to ramp up to full and stable power following its first power.
The budget for the power station has already been increased from R91.2-billion to R105-billion but a revised budget is expected in light of the improved construction processes.
Highlighting the importance of the coal-powered station coming on line as soon as possible, on 9 January Eskom again started stage one load shedding in some areas as a result of high demand and urgent maintenance being performed at certain power stations.
“We would like to appeal to customers to reduce their electricity usage as much as they can, as it will ease the pressure on the system,” the power utility said.