Waste–to-energy plants per- form a key role in reducing the amount of waste that
goes to landfill and are critical in the
generation of power for the local grid.
However, when a generator fails it is essential that repairs are completed quickly
to get the plant back online. Sulzer was
contracted to rewind a damaged generator and managed to return it to operation
within just 30 days, minimizing the costs
associated with lost production.
For a mid-sized plant, processing over
200,000 tonnes of waste per year, keeping
downtime to a minimum is essential to
maintain efficiency. Operating a comprehensive, preventative maintenance
program is crucial to operating a cost-effective plant. However, unforeseen maintenance issues will occur; in these situations, it is the speed of response and the
quality of the repair that will determine
the success of the repair project.
A waste-to-energy plant owner in the
UK experienced an unexpected failure
of the site’s sole generator, which meant
that the heat generated by the incinerator
could no longer produce energy. Keen to
resolve the issue quickly, the maintenance
manager called in Sulzer engineers, who
arrived within two hours, to carry out an
initial inspection to determine the cause
of the failure.
The results showed that the stator had
suffered from a coil shorting to earth on
the turbine side of the winding, as well as
suspected damage to the stator core. The
plant operator had to move fast. The order
was given to remove the generator from
the site for further investigation of the
core and rotor which were not accessible
without a full dismantle.
19 MW Generator Fully
Refurbished in Just 30 Days
BY KEITH BARBIER, HEAD OF INTERNATIONAL CONTRACTS AND PROJECTS, SULZER UK
The generator is central to the entire
business, both financially and physically. The first task was to disconnect all of
the ancillary equipment and remove a
section of the building’s roof to allow a
400-tonne crane to lift the generator from
its operating plinth onto a set of skates.
This enabled its removal from the building and loading onto transport for immediate delivery to the local Sulzer Service
Center in Birmingham.
With time such a critical factor in
this project, the generator was dismantled overnight to allow the rotor, stator
and coils to be tested. Apart from the
need to rewind the stator, the tests also
showed that the rotor required further
investigation as the insulation resistance tests did not meet the acceptance
criteria of 100 MΩ.
Designing and manufacturing new
stator coils is a complex task, one that
the engineers at Sulzer have perfected
over many years. Using the latest class F
insulation materials allows for thinner
layers that can withstand greater dielec-
tric stress, higher temperatures and also
creating more space for copper within the
same slot area. This reduces the resistance
of the stator winding, which runs cooler,
allowing a small increase in output.
By using the latest CAD software, the
new coils were precisely formed to ensure
an exact fit in the stator slot, making the
installation process more efficient. The
new coils were manufactured in Sulzer’s
coil winding shop in Birmingham, UK,
which uses its in-house copper rolling
mill to enable round-the-clock coil production to meet even the tightest deadline.
Once the stator had been stripped of
the old coils, the stator core inspection revealed a damaged tooth that would need
to be repaired before the new coils could
The removal of the generat
performed quickly to allow
investigation to be comple