TENSIONING

One of the first places I would look is the operator's Standards Manual.

I asssume that you've already found the spec but, you need to know what this "tensioning" thing is all about, correct?

"Tensioning" is an advanced bolt tightening method often specified in critical applications where the known inaccuracies of the "torquing" method cannot be tolerated. The latter can be subject to bolt load inaccuracies of anywhere from 20% to 100% due to unknown friction effects. This should not be confused with torque calibration accuracies which can be as low as +/- 2% with high-quality equipment.

It must be remembered that "Torque" (ft-lb or Nm) is only a measurement of the degree of resistance felt when trying to tighten a fastener to its required load (lb or N). Thus, a "properly torqued" bolt tightened to the same torque value,may either be tight enough, too loose or, overtightened. In the real world, one CANNOT predict the effect of torque to residual bolt load. This isn't a very good situation to be in when dealing with critical applications.

The "Tensioning" method eliminates this problem because friction is not part of the equation. To wit: While the torquing method relies upon the geometry of an inclined plane to result in bolt elongation, the tensioning method directly stretches a fastener without having to turn a nut. Here's a link describing the technology:

In some cases, tensioning may not be practical (fasteners are too small, access is difficult, or, sufficient thread extension isn't available. Thus, "torquing" (either simple torquing or torque/angle) is usually the only practical alternative available. One can either guess and hope that the procedure resulted in the proper bolt load or, one can verifiy the effects of torqe by measuring the resultant elongation and then "tuning" all out-of-tolerance fasteners.

I'm not sure why both the link and the image didn't work. I'll try again...

Bolt Tensioning Basics

Let's try the image again...

Seems like the link didn't work again. Let's try this:

Bolt Tensioning Basics

Thanks, That is exactly what we want to avoid The residual bolt load by torquing (friction). ADOLFO