Vibration loosening of fasteners

[tothepoint]

Anyone with proven devices or methods for preventing vibration loosening of fasteners? The flanged connections I work with are subject to extreme vibration, and I'm looking for tips for preventing the nuts from loosening. These fasteners must be re-torqued periodically for PM and inspection, so I can't spot weld the nuts to the flanges. Any tips/ideas?

 

[hacksaw]

if your shaking the nuts loose then you need to solve the vibration problem...first

 

[MadMango]

You might want to read the following thread, as this has been discussed there with some good advice.

thread725-57042

Wanna Tip? faq731-376
"Probable impossibilities are to be preferred to improbable possibilities."

 

[aybee]

Loctite, Nylock nuts,castle nuts with pins see which works best then stick with it

 

[martinwhelan]

Aybee seems to have the solution. Other things to consider are tab washers or tack welding of the nut and/or bolt. Remember to tack weld the washer also. This is used in GT exhaust cladding but some people do not like it as it creates a stress concentration in items that may be subject to fatigue. Special anti-vibration disc spring washers are available - make sure you get the ones that are specially made for this purpose and have multiple serrations for biting into mating nut e.g. to DIN 6796. You might also consider looking at your gaskets instead of your fasteners as some resilience there would help with the loosening problem.

 

[Hippo41]

I recently came across some paired washers that solved this problem. The website is

http://www.nord-lock.com.

A simple idea that seemed very effective.

Lester Milton
NBC Group Ltd, Telford, Shropshire, UK

 

[CLarson]

In the aerospace world, all fasteners are safety wired or cabled. Requires drilling a small hole in the nut or bolt and wiring in such a way as to completly prevent loosening.

 

[Sparweb]

Those Nord-Lock washers seem great for non-fatigue joints. In a fatigue sensitive joint I would be very, wary of using a washer that deliberately damages the base material. I would expect it to about double the stress concentration factor!


STF

 

[cim94sm3]

We have solved many "fatigue sensitive joints" using Nord-Lock washers, since they actually keep the preload in the joint at its initially level.

The damage you get in the base material is pure impression marks, no scratching like one-piece serrated washers. When tightening it slides on the head of the bolt and when undoing the joint it slides on the cam faces (between the pair of washers). In addition, the serrations on Nord-Lockâ washers are shaped as fish scale for minimum damage of mating material.

This is a high tech locking system, which uses geometry to lock!