Pre-tensioned fasteners

[AETX]

It seems the RCSC part 7 asks for the pre tensioned bolts such as Turn of The Nut method to have a sample bolts pre-tested prior installation of the rest of the bolts. Is there anyone familiar with this requirement? Not sure if I am reading this part correctly.

My understanding is that the installation of the turn of the nut method inspection consists of two steps. One is the pre install test of the sample bolts using a calibrated wrench. And the second step the inspector verifies the installed bolts at the connection assembly. Is my understanding correct?

What options is there if bolts are installed but the first step has not been done (the pre install test of the sample bolts is not performed and supplier doesn’t have bolts from the same lot)

Thank you in advance for your help.

 

[3DDave]

Begging? If that's what it says (I don't have a copy/access to that document) the first part is what calibrates the second, so if the first part isn't done, neither is the second. This is fairly typical in using that method, though the calibrated wrench is odd - torque has a higher variability in results than turn-of-fastener. Putting a load cell in the stack or measuring the fastener stretch would be my first choice to improve repeatability.

That said, since turn-of-wrench essentially produces elongation, and stress is proportional to elongation, then if the material is close in elastic modulus then at least the stress in the fastener will be the same regardless of lot. Similarly surface finish and lubrication don't alter the amount of extension based on the number of turns, so that variability is inconsequential.

What is exactly being tested for in that section of the document? Is it just a conversion from using a torque wrench to using turn of fastener as an analog?

 

[r6155]

@ AerchE
This concept is like a welder qualification before welding any component.

@ 3DDave
See

http://www.boltcouncil.org/files/2020RCSCSpecification.pdf

Regards

 

[sbisteel]

When things go off the rails, take a look at section 10 (arbitration) in the RCSC spec.