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On reflection: Plan maintenance with care or it could backfire

WORLDWIDE: Preventive maintenance is important for wind-farm operation, but do it too often or fail to plan it through properly, and it could do more harm than good.

(pic: Alamy)
(pic: Alamy)

The evolution of wind energy has been a fast one. As a result, the operations and maintenance (O&M) market has had to become competitive quickly, but is now a game changer in its own right.

The servicing landscape has changed enormously in recent years. With a decrease in new wind-turbine orders, many original equipment manufacturers have started to turn O&M into a serious revenue stream. The increase in the number of wind farms coming out of warranty has also led to many independent service providers entering the market.

Utilities are reaching a critical mass of installed base and, consequently, the focus is also turning more to the service business. In-house maintenance is becoming more and more common for wind-farm owners and operators, adopting strategies based on reducing wrench time (time in the turbine); scheduling maintenance during low wind periods; and developing an effective supply chain, particularly for spare parts.

Preventive maintenance

Preventive maintenance is almost always the best long-term strategy. Such planned maintenance, which includes adjustments, cleaning, lubrication, repairs and replacements, is set to improve equipment life by preventing excess depreciation and impairment.

While many may think "the more the better", this is not always true, because even scheduled maintenance has its own science and optimal points. Instead, it may be safer to follow the basic rule from the Hippocratic oath: "Primun non nocere" or, above all, do no harm.

This principle was first applied to operational strategies during World War II by Conrad Hal Waddington, a British developmental biologist working with the Royal Air Force. He was investigating the cause of a high number of aircraft regularly being out of action, either being maintained, awaiting maintenance or awaiting spare parts. The view held at that time was that the more preventive maintenance was performed, the fewer problems the aircraft would have.

The Waddington effect

Waddington started with the theory that all unscheduled downtime should be a random phenomenon. He plotted all these downtime events in relation to the last preventive maintenance, expecting there to be no relationship. But he discovered a pattern, where unscheduled downtime increased immediately after maintenance.

So after these preventative maintenance procedures, the aircraft were actually less reliable for a while - disturbed by the mechanics for maintenance, the systems required further maintenance to repair. Waddington recommended a reduction in scheduled maintenance, and downtime reduced. This is now known as the Waddington effect, and the principle can be applied elsewhere.

Before taking any action on an operating turbine, we need to be sure that our actions at least will not damage the system or its performance. Therefore, the less invasive the preventive maintenance is, the better the outcome, according to the Waddington effect. Also, there is always a possibility that the new part installed is defective, with a good part being removed in favour of a bad one.

As the Waddington effect shows, more is not always better from a performance point of view. And look to deep operational knowledge and consider the basic principle of "above all, do no harm".

Jordi Torres is a PHD engineer who leads wind O&M operations across northern Europe. He writes a blog at jtorresbutet.wordpress.com

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