POWER GENERATION
turbine. Di erent tools can be attached to
the robotic arm (pictured above) for visual
inspection, laser scanning, conductivity
testing, surface cleaning, drainage hole
cleaning, sanding, and lling.
“Technicians who would otherwise
hang hundreds of metres in the air
manually working on each turbine blade,
where safety concerns and weather
limit operations, can now operate these
inspection and maintenance services from
the safety of a van, with controls that are
as easy to use as a kid’s gaming console,”
says Janis Putrams, CEO of Aerones.
CONDITION MONITORING
Access challenges make condition
monitoring particularly important in wind
turbines. The potential for signi cant
downtime in wind turbine gearboxes
makes these the prime candidates.
Insurers often require all roller bearings
in the drivetrain to be replaced after ve
years, unless condition monitoring is
being carried out.
The speci c requirements of wind
turbines often mean that standard
methods of condition monitoring
don’t apply, such as those covered in
ISO 10816-3 (Mechanical Vibration
— Evaluation Of Machine Vibration
By Measurements On Non-Rotating
Parts — Part 3: Industrial machines with
nominal power above 15 KW and nominal
speeds between 120rpm-15,000rpm
when measured in situ). Vibration of the
tower and nacelle caused by wind ow
disturbances, resonances within these
structures, and potentially also sea swell
for o shore wind turbines may alter
the time behaviour and spectra of the
vibration signals compared to those of
other industrial structures. However,
special standards have been created
to deal with wind turbines, such as ISO
10816-21: 2015, which covers horizontal
axis wind turbines with a gearbox. (A
second standard is also planned, ISO
10816-22, for direct drive wind turbines).
ISO 10816-21 recommends zones
for evaluating vibration at continuous
load operation. For the aerodynamicallyexcited
vibration of the nacelle and tower
with frequencies between 0.1 Hz and 10
Hz, vibrations should be measured over
a 10-minute period. Typical measuring
positions are in the nacelle at the main
frame close to the rotor main bearing,
on the structure above the tower ange,
and in the rear end of the nacelle on one
side of the generator or main frame.
Measurements of acceleration or
velocity should be made along the rotor
shaft axis and in the radial directions.
Gearboxes and generators, with
characteristic vibration with frequencies
from 10 Hz to more than 1,000 Hz, can
be measured using shorter evaluation
periods of around one minute. All
vibration measurements should
be measured in the axial and radial
directions. For rotor bearings with
three-point suspension, measurements
should be taken on the housing of the
front bearing. Where two separate rotor
bearings are present, measurements
should be taken on both housings.
Gearbox measurements should be
made on the housing close to the input
shaft bearing and output shaft bearing.
Generator vibration is either measured
on the housing for integrated gearboxgenerator
designs or on the bearing
housings for elastically-coupled designs.
Although access to wind turbines
can make maintenance challenging,
a combination of remote condition
monitoring and automation can enable
cost-e ective operation. These trends
are expected to continue, driving down
the cost of renewable energy.
Real savings expected from virtual reality
A data-rich digital twin has been created of O shore
Renewable Energy (ORE) Catapult’s Levenmouth
Demonstration Turbine. The software simulation, called
R2S, enables personnel to remotely visit sites and easily
access technical and operational data.
Lorna Bennet, mechanical engineer with ORE Catapult,
said: “We believe that R2S’s technology could revolutionise
o shore wind O&M. The digital twin has proven to be a
unique solution enabling technicians and interdisciplinary
teams to view the turbine’s inner workings and all pieces
of equipment anywhere, at any time. This has enabled
remote inspection of the turbine, boosting the planning of
operations and
reducing the
need to go o shore. It has
also changed the ways individuals are working – generating
signi cant time and nancial savings.”
Laura Fairley, market development manager at engineering
consultancy project partner James Fisher Asset Information
Services added: “With o shore turbines getting bigger and
more powerful, operations and maintenance costs have
escalated. R2S has proven to be an e ective planning tool.”
JF AIS is now looking to work with Vattenfall on the
European O shore Wind Demonstration Centre in Scotland.
74 www.operationsengineer.org.uk Autumn 2020
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