Being at the front edge of a blade management strategy

Lene Hellstern

Director & Head of Engineering & Asset Integrity
This article addresses key topics that the wind farm operator or owner needs to consider to minimize blade repair expenses for their operational assets.

Historically little attention has been paid to operations strategies for blades. However, Wind farms owners now realize, that blade management strategies need more attention. With turbine and blade size increasing rapidly, the costs of maintenance and repair (or lack thereof) are even more important. Blades are no longer considered maintenance-free components, and their maintenance and repair costs need to be included in the OPEX budget. Catastrophic blade failure, transverse cracks and leading-edge issues are words that have entered our vocabulary and can, if not taken proper care of, absorb a big part of the OPEX budget for sites in operation.

This article addresses key topics that the wind farm operator or owner needs to consider to minimize blade repair expenses for their operational assets. With good planning, blade knowledge, and a solid blade management strategy, the operator can reduce the impact of a blade damage dramatically.

Why read this article?

  • Understand the importance of blade management strategies
  • Make sure you properly budget for blade maintenance and repairs
  • Understand what is needed to ensure proper preparation for blade damages

Key considerations for optimizing your blade management strategy

At some point during the lifetime of a turbine, some kind of damage to its blades is likely to occur. When this happens, the following costs need to be considered; inspection cost, repair cost, transportation and standby-costs, lost production and possible maintenance costs during downtime. The sum of these costs needs to be evaluated against the probability that the damage will propagate. If the damage you have on the blade does not affect your production, and it is not likely to propagate over the next 5 years, then it might not need to be repaired anytime soon. On the other hand, the cost of failing to repair a damaged blade in time, can end in catastrophic failure requiring blade replacement. This can be rather painful for the OPEX budget. If no blade maintenance and lost production has been budgeted, it hurts even more.

Taking into consideration that the costs for blade repair have at least tripled over the years, focusing on blades is a good investment. One of the biggest cost drivers on the blade budget is unplanned repairs. Being able to predict how the blade damage will propagate and repairing at an optimal time is valuable. The only way of preparing for this is to have a well-planned blade management strategy in place.

In the list below, the key considerations that need to be addressed in a blade management strategy are summarized along with the listed topics that prepare you for addressing damage to your blades.

1. Repairs of damage on blades : Blades are not maintenance free and many repair methods will not last the lifetime of the WTG

  • Do you know what repair methods are the best for different types of damage? It’s important to identify the best in class suppliers for different types of damages?
  • When do you need to stop and repair? Sometimes you can keep the turbine running despite a damage.
  • What do you do when the weather is preventing repair or the right kind of repair?

2. Icing on the blades : In some parts of the world there is a possibility of ice accumulating on turbine blades. This will have a negative effect on production.

  • Do you need de-icing on your blades? You need to ensure a proper de-icing system as well as a properly functioning ice detection system.
  • What does your environmental permit allow? While some permits allow operations with ice on the blades others will require you to stop production until the ice melts completely.
  • Could there be HSE issues incase of ice throw from the blades? You need to ensure proper insurance coverage in the event of damaged property or injury due to ice throw from blades.

3. Lightning : It is not uncommon that blades are hit by lightning during operation.

  • Does lightning occurred frequently where the turbines are located?
  • Are you sure the lightning receptors work and is the lightning strike detector activated?
  • How do you know if your damage is caused by lightning?
  • How are the blades insured in case of lightning damage? Are you covered merely for repair work, or associated production losses?

4. Inspection methods for the blades : In order to discover damage on the blades and minimize repairs, several methods can be used

  • How often should you inspect and which inspection method should be used? There are many different inspections methods
  • Are you informed about what inspection methods show which damage types? As visual inspections do not show everything, you need to know when to use NDT (nondestructive testing) methods.+

5. Blade condition monitoring : Blade monitoring is essential to keep the costs of blade repairs down.

  • With what frequency and with which methods should you inspect the blades?
  • Have you chosen an appropriate platform for storing pictures, scans, and reports from your blade inspections? You need a platform that supports document management of massive amounts of information for the next 25 years.
  • Does your platform allow you to transfer the documentation and data to other systems, or export work orders from the platform?

6. Manufacturing of blades : There are different kinds of blade designs, manufacturing possibilities and ways to test the blades

  • Do you know what kind of design the blade is? In any case, it is always useful to have the OEM’s as-built documentation.
  • Has the design been certified according to the latest standards? Sometimes old standards are used, and the test methods are not impressive.
  • Do you know if the OEM did a thermographic scan when the blades were manufactured? If they did so, it is valuable to have the associated documentation.
  • Do you have the factory repair reports from when the blades were originally manufactured? This can be valuable documentation in a later stage if damages occur.

7. Budgeting for blade maintenance and repair : Many operators underestimate maintenance and repair costs associated with blades

  • Have you budgeted for all relevant blade maintenance and repair costs? Typical costs are inspection costs, repair costs, transportation and standby-costs, lost production and possibly maintenance costs during downtime
  • Do you have solid assumptions on failure rates and repetitive maintenance and repair activities? Many operators underestimate the frequency of recurring damages.

8. OEM contracting : Clear contractual obligations of both owner and OEM are important

  • What is the scope of blade maintenance and repairs in your contracts with OEMs? This applies to both service contracts as well as warranties.
  • How is wear and tear described in your contracts? The definitions can have large consequences for warranty cases.
  • Are any blade inspections or blade repair work included in your service contract? If this is the case, you need to ensure that inspection methods are clearly described, as well as the extent of repair services provided by the service provider.

9. Production optimization & losses : Great value is realized by knowing how your blades contribute to production optimization

  • Which blade upgrades increase your production, and what price is worth paying for the upgrade?
  • Are you aware of the types of damage for which you can continue operations? You can avoid losing production by running the turbine during mobilization time or delaying with the repair work until a more favorable time with low winds.
  • Does your insurance cover lost production during downtime, due to blade damages? Your insurance coverage will likely be driven by the company risk profile.

There are many topics that need to be considered when developing a blade management strategy and for many owners the above are new topic. So please let us know if we can help you in any way.

Want to learn more about blade management strategy?

There are many considerations when developing a blade management strategy, and for many owners, the above are new topics. Please let us know if we can help you in any way with your blade strategy and we’ll be happy to answer your questions!

Lene Hellstern | Director & Head of Engineering & Asset Integrity | Get in touch
Leoni Christensen | Head of O&M Strategy, Concepts & OPEX | Get in touch