Keep it Spinning Safely: Maintenance Tips for Small Wind Turbines

If you have a wind turbine or windpump, it needs routine maintenance to keep spinning. Treated right, wind turbines will provide reliable and safe operation. Here are a few tips to make sure your turbine serves you well.

As with all equipment, it is important to read the owner’s manual which will include a detailed list of maintenance items particular to your turbine. For long life and safe operation of the turbine, the manufacturer’s guidelines should be followed. Please note that this blog is a simplified “generic checklist” which is not a replacement for the specific manufacturer’s recommendations.

In general, maintenance activities fall into the following main groups:

Foundation & Stabilization

Cracks in a cement foundation start small, but can quickly become a big problem for a number of reasons.  First, cracks will hold water in them which can freeze on a cold night. As water freezes, it expands, creating a bigger, deeper, and more problematic crack. If the crack goes far enough, the steel rebar inside the concrete foundation could be exposed to water and air, causing it to rust and weakening the foundation. A damaged foundation can be a very expensive repair.

For small cracks, a simple coat of cement sealer is often enough to fix the problem and keep water out. Larger cracks may need to be ground out and filled with fresh cement before applying a seal coat.

Long and deep cracks may have already compromised the foundation’s integrity; if there is a crack running along an interior corner of the foundation or slightly excessive turbine sway, it’s time to get a professional opinion.

Many turbines are stabilized using guy wires. Make sure there are no loose bolts, rusty spots, frayed wires, or other problems. A broken cable is not common, but should it happen, the loss of your turbine is very likely.

Bolts

A potential failure point of small wind turbines are the bolts holding it together and holding the turbine to the top of the tower. These bolts are exposed to the elements, carry high loads with lots of vibration, and are difficult to access and service which can result in their not being inspected as regularly as they should.

The manufacturer usually specifies critical bolts to check and re-torque and specifies torque values. It’s important to note that when re-torquing bolts, rust or other debris can cause false torque readings, as can lubrication where it was not intended. Rusty bolts should be cleaned with a wire brush if necessary. In addition, it is a good practice to replace the bolts holding the turbine to the tower every few years, especially in areas of high turbulence or if they become excessively rusted.

During a regular maintenance inspection, bolts on the tower should also be inspected, as should welds.

Blades

Blades are perhaps the most critical component of a wind turbine and need to be inspected carefully at regular intervals, along with other aerodynamic control surfaces (such as a furling tail, for example).

The leading edge of the blades gets a lot of abuse because of bugs, rain, hail, and dust in the air. These should be visually checked for erosion, and repaired if necessary. Aftermarket skins can provide extra-durable protection to the leading edge if the turbine is in an area with a lot of bugs or dust.

Any cracks in the blade should be considered very serious. A crack under load could quickly fail during high wind and cause catastrophic damage to the wind turbine, tower, and surrounding buildings.

Blade accessories such as vortex generators are often knocked loose by ice, birds, or adhesive failure, and can be replaced by cleaning the spot and gluing another in place.

Broken blades can be replaced or repaired, depending on the extent of the damage.

Lubrication

All moving parts of the turbine need lubrication. The types and typical service intervals are usually specified in the owner’s manual. In general, bearings need to be greased, and gearboxes (if present) need an oil change. If the turbine has been operating for a few years, it is also a good practice to send a sample of the gearbox oil and/or bearing grease for analysis to a laboratory; this step could give advanced warning of a gearbox failure. Even if not sending out a sample, inspect the oil and grease for metallic flakes, which could indicate a broken gear or bearing.

Electrical Connections and Components

The electrical components of a small wind turbine vary in type and complexity, depending on the type of installation and location. For example, a 100 kW grid-tied wind turbine likely has a small transformer. A small 10 kW off-grid wind turbine may be connected to a charge controller and battery bank. A tiny 2 kW wind turbine may be connected directly to a load such as a water pump. In each case, the maintenance requirements differ.

When working on the electrical system, remember to securely lock the turbine from rotating (apply the brake) and disconnect from any external voltage source.

In addition to the power handling components, the wind turbine is likely to have a controller unit which should be inspected for any signs of damage. A controller which is working well but running at an abnormally high temperature or with hot spots may be in danger of imminent failure. Electrical failures can lead to fire and/or loss of the entire wind turbine.

Cables should be anchored securely and not allowed to flap in the wind. All cables and insulation should be checked for wear and replaced if any wear is present.

Inside the turbine, connections should be checked to make sure they are clean and tight. Any rotating connections such as the slip rings should be checked, and the brushes replaced if excessively worn.

At every point of the turbine, ground connections should be inspected.  These can become corroded and lose their conductivity, increasing the chance of damage due to lightning.

Paint & Protection

Paint may be a thin layer of color, but it is also the turbine’s last defense against corrosion and wear. Check the paint for cracks or chips, and touch up as necessary. Re-painting the blades is not generally recommended unless necessitated due to repairs; any cracks on the blades or structural components may be more than superficial and should be investigated.

Bolts and other components may be protected by a layer of grease or a protective covering. These should be checked and re-greased or repaired if necessary. Depending on local regulations, the turbine may be required to display aviation lights (blinking red lights). Cable conduit and grommets need to be checked to be sure they are not damaged.

Gearbox Boroscope Inspection

Small wind turbines have a reputation for being well-built and robust. Gearbox failures are infrequent when compared with large turbines however, the quality of build varies widely across manufacturers. A good practice would be to inspect the interior of the gearbox using a boroscope after five years of operation. This visual check could reveal surprising problems such as a partially broken gear tooth or excessive bearing wear, which may not be noticeable during operation.

When to Call for Help

If during the inspection something doesn’t seem right, call an expert.  They will be able to accurately assess and perhaps even repair any damage.

If maintaining the turbine is a problem, professional technicians are specially trained and able to safely climb the tower and service the wind turbine. Many technicians offer maintenance agreements which will ensure that the service will follow or exceed the manufacturer’s recommendations.

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© 2019 The Hartford Steam Boiler Inspection and Insurance Company. All rights reserved. This article is for informational purposes only and is not intended to convey or constitute legal advice. HSB makes no warranties or representations as to the accuracy or completeness of the content herein. Under no circumstances shall HSB or any party involved in creating or delivering this article be liable to you for any loss or damage that results from the use of the information contained herein. Except as otherwise expressly permitted by HSB in writing, no portion of this article may be reproduced, copied, or distributed in any way. This article does not modify or invalidate any of the provisions, exclusions, terms or conditions of the applicable policy and endorsements. For specific terms and conditions, please refer to the applicable endorsement form.

Linkesh Diwan

Linkesh Diwan is a Sr. Engineer in HSB's Technical Due Diligence division.

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