19 MW Generator
Fully Refurbished
In Just 30 Days
aste–to-energy plants
perform 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.
W
This enabled its removal from the building
and loading onto transport for immediate
delivery to the local Sulzer Service Center
in Birmingham.
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. 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.
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. 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 dielectric
stress, higher temperatures and also
creating more space for copper within the
same slot area. This reduces the re sistance
of the stator winding, which runs cooler,
allowing a small increase in output.
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. Meeting the tightest deadline
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.
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.
Comprehensive investigations 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 be installed. The damaged slot
section was machined out to allow the
installation of an epoxy glass block G11,
which was machined to restore the
stator slot profile to the correct
dimensions.
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. Keith Barbier, Head of
International Contracts
and Projects at Sulzer UK,
comments: "The re-build
process is a very skilled
and time consuming
task because precision
74
PECM Issue 27
Sulzer is the leading worldwide,
independent service provider for large
rotating equipment. With technically
advanced and innovative service and
maintenance support solutions, Sulzer
provides a turnkey service that provides
its customers with the peace of mind to
focus on their core operations.
www.sulzer.com