Page 37 - Energize March 2021

TECHNICAL

other mills included combinations of items that could be manufactured quickly in combination systems for which the design modifications
with off-the-shelf equipment, and long manufacturing lead-time items that needed to be cast. were done, or due to other plant systems
Tests on Medupi Unit 3 indicated positive results for all mill modifications, and the – of which there are many – on which no
implementation of the items with short manufacturing and procurement lead-times were modifications were done. Eskom says that
rolled out. Manufacturing of the mill items with long manufacturing lead-times were although the availability of the systems on
started immediately after the rollout decision and will be rolled out during upcoming unit which design modifications were done did
and mill outages. improve, this improvement was negated
A year after the project started, there is still a significant amount of modification work to by unforeseen once-off events in other
be done on all the remaining five units at Medupi. These include the manufacturing of long unrelated sub-systems.
lead-time items on the mills, the gas air heater operational modifications, and the boiler low Furthermore, Eskom explains that
load modifications. No work has yet commenced on the design modifications of the six units the EAF of Unit 3 was pushed down by
at Kusile. increased planned outages after the
Considering the Medupi Unit 3 performance figures shown in Figure 2, there does not shutdown due to extra-ordinary planned
appear to be that much difference in energy availability factor (EAF) before and after the maintenance in preparation for performance
design modifications. However, a careful analysis of the EAF for the past 50 weeks since the verification tests of the modifications done.
10-week shutdown in early 2020 indicates an average EAF of 75%, which is an improvement “Typically, you would need a longer period
of the EAF of below 70% before the modifications. to evaluate performance, in order to even
However, the week-on-week EAF for Medupi Unit 3 is still erratic, with ongoing high out the impact of such unforeseen events”,
levels of planned (PCLF) and unplanned (UCLF) outages, and certainly not what one would says Eskom.
expect from a properly functioning, relatively new, base-supply unit that underwent a major However, Eskom has acknowledged
10-week rework outage a year earlier. One may expect the average EAF in such a case to that performance of the pulse jet fabric
be more like 85% to 90%, which is still below the 92% “use requirement specification” filter plant after the rework has been
target set for the units. disappointing. The lifetime of the fabric
Eskom indicates that this continuing sub-par performance can either be due to sub- filter bags before replacement has only
increased from nine months to thirteen
months, instead of the 36 months expected
in the “use requirement specification”.
What has become clear, though, is
that there is still a long way to go before
the Medupi and Kusile coal-fired power
stations will operate at the level of
performance originally intended. Indeed, it
is becoming apparent that this performance
will likely never be achieved.
The direct costs of the efforts to
improve the performance of Medupi and
Kusile, the indirect costs of their poor
performance on lost production and lost
sales, and the cost to the economy due to
load shedding, is truly enormous and still to
be calculated. n

Send your comments to
Figure 2: Medupi Unit 3 performance before and after the design modifications. (Source: Eskom) rogerl@nowmedia.co.za

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