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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