Nordlock washer torque verification

[SloFlo]

Good day everyone. I would like to rquest your thoughts on Nordlock torque verificaiton.

Does anyone have experience verifying that Nordlocks are holding the initial installation preload after X amount of hours of operation? Due to the nature of the Nordlock and the cams it seems like it would be a difficult thing to do with a simple breakaway gauged torque wrench. I'm not necessarily looking for a quantitative value result, a qualitative consisten result would be fine. What are your thoughts on this?

Thanks,
SloFlo

 

[Screwman1]

Ahh yes....trying to determine remaining preload in-service with a torque check. You have pretty much answered your own question...it won't work. It doesn't work well on ordinary fasteners and Nordlock parts make it pretty much a losing battle.
I have always told people that more good joints have been screwed up after the fact with the inspectors torque wrench than have been fixed. If the joint has been designed properly and it has been assembled properly (both things that can be documented), then don't bother checking it.
The only thing that might work would be an ultrasonic bolt gage, but that has it's own set of issues.

 

[MiketheEngineer]

Pick up that 2 ton phone and call the mfg. They should know!!!!

 

[MintJulep]

Ultrasonic extinsiometer.

 

[racookpe1978]

IF the Nordlock washer/cams are aligned properly when they were tightened,
and IF the Nordlock washer/cams meet the Nordlock spec's fopr size and shape and material coatings - that is, if they are not Chinese knock-off's mimicking that company's products
and IF the Nordlock washer/cams were tightened properly to almost any preload at all (if the bolt or stud were stretched even a little bit)

then the Nordlock will stay tight. (Well, the bolt/stud will stay tight, because the Norlock will prevent "backing off" enough to rotate the nut.) But you can't "test it" conventionally unless you measured the stretch (initial and final length) of each stud/bolt.

What you could do is put a spot of paint or steel marker pen or even Locktite on the threads of the nut when they were first torqued down, and be able to prove (until disassembly) that no rotation took place since assembly.