Bolted Connections in Solar Installations: Vibration

In addition to the threat of relaxation described previously, vibration is another way in which bolted connection in solar installations can be compromised.

In tightened fasteners, frictional resistance develops between the bolt and nut threads and between the bolt head and the nut against the joined material. If this resistance is reduced, even for a microsecond, tensile stress in the bolt will cause the mating threads to loosen. Locking mechanisms can be employed to resist loosening.

To prevent loosening caused by vibration, consider taking the following steps:

• The best way to clamp the joined material sufficiently that the frictional resistance exceeds any applied shear force that will occur in service. Properly preload the bolt.

• Adjusting joint geometry to provide a mechanical restraint.

• Use jam nuts, slotted nuts with a cotter pin.

• Use anaerobic adhesives to cement threads together.

• Use self-locking fasteners such as locknuts, nylon thread patches or pellets, or wedge-lock type washers.

If you have any questions about how to prevent loosening due to vibration in a solar fastener connection, don’t hesitate to contact us for additional help.