Wind turbines defective parts warranty

Lately I’ve been spending some time trying to learn something more about quality. Although I see that there is no consensus on the business effectiveness of some of these technique I’ve decided to take a certification (ASQ Six Sigma Green Belt) to have a first-hand experience.

One of the first concept I’ve learnt is the difference between defect and defective. This is the standard definition in the wind industry:

“Defect” is defined as a non-conformity, a failure to comply with the Technical Specifications, a flaw in design, manufacturing, workmanship or damage.

“Defective” is defined as a part that has one or more defects and fail due to it.

The key concept here is that in principle it is possible to have one or more defect on a component without having safety or operational problems.

Wind turbines warranties (and presumably other similar equipment) usually are based in the concept of defective – that is, of failure of the component to operate correctly.

The logic is that a failure is usually a black or white concept: either the gearbox is working or it is broken.

However, seen from the perspective of the customer, this definition is not reassuring: a component could have a defect that, even if it’s not preventing the turbine to work, is making it underperforming, unreliable, deteriorating quicker than usual, etc.

Basically the concern of the customer is that the turbine seller will simply “try to keep the turbine alive” until the defect warranty expire (usually after 2 years). Afterwards, it will become a problem of the customer.

For this reason the clause with the definition of defect and defective is usually extensively negotiated. Some possible wording, from the least to the most favourable to the customer, are:

1. Defective is a part that fails due to a defect
2. Defective is a part that has a defect that could reasonably cause adverse effects on production or safety
3. Defective is a part that doesn’t match the Technical Specifications
4. Defective is a part that contain a defect

Obviously the last one is very onerous for the company who has to mantain the turbine, while the second can offer a reasonable level of protection to both parties.