Bolted Joints and the Windmill Industry: Five Causes of Loose Joints

Although every engineering project requires nuts and bolts, a windmill has a very specific need for such fasteners. When a bolt comes loose in other projects there tends to be a backup plan to accommodate the fixture until the proper maintenance is conducted. A windmill, however, relies specifically on a weight balance which if disrupted can potentially cause more damage than it might cost to simply build a new one. Therefore, proper bolt installation is crucial, and there are a few known ways in which bolts can become loosened that always need to be addressed during preventative maintenance schedules.

Lack of Proper Tension to prevent Self Loosening

The very concept of a bolt is that although it screws together tightly with the tapped piece it is threaded for, an amount of tension locks the threads in place so they can't come undone. A locking washer, essentially a spring placed between the nut's head and the piece it is bolted to, is usually a good means toward providing extra tension. A gasket can also work, although it may need to be replaced over time as it becomes brittle with age. As applicable, a second nut can be used if the situation allows to provide an extra layer of protection.

Thermal Expansion and Contraction

The reason a nut and bolt situation requires such tension is because the pieces actually expand and contract throughout the year as weather changes both temperature and humidity. As the pieces expand and contract, the threads will naturally come unlocked, and continue to loosen over time.

Shock and Vibration

In addition to how the weather affects the fastener, shock and vibrations are a concern especially worthy of consideration with a project as specific as a windmill. Although considered an engineering project, a windmill is also an architectural structure, a building, and as such is subject to the Earth's movements. Even without an actual earthquake or noticeable event, the ground is moving on a geological level and the building does experience some movement through settling over the years.

Age and Decay

Age will decay nearly any man made material, and even steel nuts and bolts will experience some corrosion over time. Oiling the bolts may help stave off corrosion, but inherently makes them slick and more prone to loosening through vibration and thermal expansion. Although in most situations over the course of a lifetime bolts aren't going to be heavily affected by corrosion, but it is important to remain aware of the potential problem as excessive moisture can and will cause a bolt to corrode and loosen.

Improper Installation

There is always a final drawback to nuts and bolts, which is an undeniable factor of human error. The windmill may be designed using an assumption that everything will go as planned, but the fact is that a bolt may mot be completely tightened, or a washer may get left off during construction. The simple fix is to double check everything before putting the windmill into operation.

Conclusion

The bottom line is that nuts and bolts are reliable fasteners when used properly, but even in perfect conditions they can and do fail. The main effort to prevent problems is to use the best bolts available and hire recognized professionals to conduct the installation.