Digital life cycle in offshore wind

By Eize de Vries

Digitalization has become a key wind industry trend impacting all products and processes from design phase and manufacturing stages up to lifetime service upkeep and support. We spoke with ZF Wind Power experts in Antwerp about digitalization’s main principles and benefits for optimized product performance, availability, operating lifetime, lifetime extension, and ZF Wind Power’s intelligent ‘spare parts optimization service.’  

ZF Wind Power subdivides its digitalization efforts as
an integral concept into products and production in factory environments, including
new technologies and pro-active life-cycle based analytics, said Head of
Digitalization Dr. Joris Peeters in his introduction: “Our digitalization
journey commenced already in the previous decade, rather modestly by putting
sensors in prototype gearboxes for testing purposes. This evolved into also accumulating
operational data and in making insights from these available to turbine owners/operators.”
During 2019, ZF introduced a concept focusing on advanced integral deployment
of digital technology to increase turbine output, gearbox availability and
lifetime.

He added that the latter is ZF Wind Power’s first
commercial data enabled product made available to the wind industry, but backed
by 40-year experience in gearbox innovation, gearbox reliability, studying failure
causes and their failure mechanisms. Accumulating data is thereby only one side
of the coin because dedicated experts are needed for in-depth analysis, for
building in-depth insight into such phenomena, and understanding complex
relationships linked to aging.

Examples of intelligence accumulated inside factories during
gearbox manufacturing are data on what parts have been put inside, specifics on
production dates, dimensional characteristics, and stored values like on individual
bolt-torque values. Peeters: “We further collect data during gearbox running-in
tests including measurement recordings on vibration patterns, noise and temperatures. Each gear inside
any gearbox further has its own permanent unique Data Metric Code or DMC
‘stamped in.’ In the past, all such data had to be written down and filed with inherent
higher risk of human error and data loss. Today, these values are digitally
recorded, saved and safely stored, and distributed to relevant channels within the
company and to third parties when required.”

He went on explaining that continued product design
evolution and innovation efforts together with optimal lifecycle services
together are aimed at achieving the lowest possible gearbox and wind turbine
LCOE. Data analytics is thereby in ZFWP’s vision key to reduce OPEX by increasing
output and availability, and extend gearbox and wind turbine lifetime backed by
science and experience.

“A stable first foundation pillar”

After a finished gearbox has completed all bench testing
procedures, it leaves the factory with a Digital
Birth Certificate. This documentation contains specific details of the
given gearbox’ design supplemented by ‘as-built information’ of any single unit
obtained during product development and manufacturing. Peeters: “These crucial data
represent a stable first foundation pillar for our optimized service
performance, and it serves as a functional interface between gearbox development
& manufacturing and operational phase. The second foundation pillar is called
Life Cycle Monitor. It registers and
stores gearbox performance data obtained from a standard fitted turbine Supervisory
Control and Data Acquisition (SCADA) system, and now near-standard Condition
Monitoring System (CMS).”

He continued explaining on the
combination of Digital Birth Certificate and
Life Cycle Monitor together withZF Wind Power’s long gearbox expertise
on failure modes and remedying solutions being used in Life Cycle Analytics. This advanced decision-making tool backed by
advanced statistics provides ‘remaining lifetime predictions’ and supports alert-based
service intervention recommendations, which substantially contributes to
optimal and cost-effective operation and maintenance (O&M) performance.
Peeters: “Consumed lifetime considers both gearbox design model and actual
loading per gearbox component being the two main drivers. Calculating gearbox consumed
lifetime could be compared with a passenger car’s total mileage. We use ‘comparable’ information of the Lifecycle Monitor to calculate the consumed lifetime. An
interlinked question is how far will I be able to run the car in the future,
and what possible issues could I have with it?”

This information is based on
statistics, used for calculating the chances of anything happening in the
future based on the vast amount of service intervention information made available
on ZF gearboxes. The spare parts recommendation is the outcome of both consumed
and remaining lifetime.

Key contributing factors to reliable remaining
lifetime predictions are an inventory of past failures, their specific nature
and analysis of individual failure root causes. It also considers specific impacting
factors like production batch-related issues during the manufacture of a given
gearbox model, and if these have occurred must be included in remaining
lifetime prediction calculations as well.

An interlinked topic he touched is on accumulated new
data following a specific gearbox remedying/service intervention. New
service intervention information is added to the historical service
intervention information to continuously update the service history of a
gearbox. The overall history is then used in the remaining lifetime
calculation. Such data are valuable as well for the development of
uniform gearbox upkeep standards said Peeters, and as such would fit seamlessly
into an ongoing wind industry trend for multi-brand asset service support: “Future
‘Smart Wind’ turbine upkeep concepts will be characterized by standardization and
with sharing key data the norm. However, the acceptance and resulting success
will much depend on whether independent service providers can be granted full
access to high-level data in SCADA, CMS in parallel to for instance Life Cycle Analytics.”

Another main wind industry trend he observed is for today
common full service contracts up to 15 – 20 years+ with minimum availability
guarantees. De-risking such comprehensive business models requires full
lifecycle data access, including SCADA and CMS providing detailed insight in
historic performance and availability and service interventions. Currently, highest
demand in O&M is with older turbine models, where unfortunately sufficient reliable
statistical data is often not available. Modern turbines are by comparison much
better equipped with proper performance data capturing from day one.

“The biggest promise with future gearboxes development
is ongoing technology evolution of cost-effective, modular scalable product
platforms like our latest SHIFT 6k series (Insert). Such efficient integral approach
as a key advantage allows much faster data accumulation from product development
and manufacture to lifecycle upkeep, and ultimately offers huge LCOE benefits for
both onshore and offshore wind”, concluded Peeters.

Nick van Damme is Product Manager Digitalization and
part of ZF Wind Power’s team of digitalization experts based in Antwerp. He said
that turbine asset owners/operators for adequately managing drivetrain-related
O&M risks and minimizing OPEX must rely on reliable service solutions and
optimal spare parts availability for minimizing downtime and lost production
hours. For reducing additional dependency on unpredictable market conditions
including (genuine) spare parts price fluctuation risks, ZF Wind Power earlier
this year introduced a Spare Parts
Optimization Service. Van Damme: “We consider this a first exciting step
towards ensuring that the right original components are timely available at correct
locations, all instrumental preconditions in ensuring minimal turbine downtime.
Remaining lifetime is a crucial parameter for determining what components would
be required where and when.”

He added that digitalization has made these and other
information-based development processes now far more integrated, which for
instance allows much faster accumulation of more data for quicker determining
gearbox problems. The integral service package comes with O&M
documentation, including technical manuals and spare parts lists made available
online for OEM’ and ISP-related service crews alike for adequately performing
information-supported service tasks.

Gearbox clients receive the same O&M information
package online, for every gearbox type and model in their turbine fleets. This
gives field crews anywhere in the world access to the latest gearbox
information, allowing them to optimize time and cost of any remedying action
either onsite or conducted inside a workshop, said Van Damme: “Service
recommendations based on real-time data from any given turbine, enhance the transition
from reactive (act once a failure has occurred) to pro-active interventions. It
is for example possible that a turbine’s CMS gives an alert for a developing
issue in a planetary gear unit. This is then processed within the Life Cycle Analytics tool with an
alert-based recommendation.”

One possible intervention option could be to allow the
continued operation at reduced output level, for providing sufficient time to have
the right conditions in place for conducting the necessary repair/exchange activity.
He further elaborated on one out of several new ideas in progress, the further
expansion of ZF Wind Power’s Spare Parts
Optimization Service by creating extra support links towards third parties
in the wind industry. This focuses at ‘who will conduct what service action
where and when’ and the idea extends beyond today’s in-house service
organization model.

“Overall concept is still optional”

The latter as an overall
concept is still optional in today’s service agreements, but will become a
valuable contribution in fighting expected future shortages in gearbox
components including bearings. And the gearbox/turbine client will have, depending
upon service contract, a turbine specific spare parts recommendation and
availability guarantee said Van Damme in his conclusion: “The digital
technologies to implement these and many other future solutions is readily
available. Bottleneck for the entire wind industry hampering advancement pace is
having sufficient standardisation in sharing of data and finding the right
experts with the required skills for advanced statistical data analysis in time.
Therefore, ZF Wind Power invests in as much automatization as possible to keep
human effort minimal.”

ZF Friedrichshafen AG is a world-leading supplier for automotive drivelines and chassis technology, with over a century experience in power transmission technology. During 1979, ZF supplied the first kW-size gearbox to a Danish wind turbine manufacturer. Today, ZF Wind Power is a globally active gearbox manufacturing and service business with 65,000 gearboxes supplied adding up to an over 120GW installed base. The company operates manufacturing facilities in Germany, Belgium, India, and China and serves all key wind power segments. The company supplies gearboxes up to 5MW+ for onshore and 9.5MW/10MW ratings in the offshore segment.

In 2018, ZF Wind Power introduced the SHIFT 6k gearbox featuring journal bearings in most positions except for the easy-to-access planet carriers in the planetary stages, and with record 175 Nm/kg torque density. This allows a substantial reduction in gearbox mass for a given input torque. The gearbox for onshore and specific offshore application is available in ratings up to 7MW and rotor diameters in the 180m range.

MHI Vestas since 2014 applies ZFWP’s medium-speed gearboxes in its 8 – 10MW V164 offshore series and the latest V174-9.5 MW successor model. This currently most powerful gearbox with record 10,000kNm input torque. With future designs claimed further scalable for turbines of at least 15MW.

This article was previously published in the Offshore WIND magazine, issue 2, 2019.

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