Quote:
Originally Posted by Head416
That's ^ what I was thinking. Sounds like all your problems are solved if you verify the pressure at the wrench. That has to be easier and cheaper than all the other solutions.
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Measuring the pressure at the wrench gets us close, but doesn't address the degradation of the wrench itself. We might try this just for the fun of it, though. We actually have numerous wrenches (for a variety of torquing needs). Some of them are pneumatic, some are electric and some are open-end "maxi-break" wrenches. This is just one issue.
The wrenches currently cost us about $7000 + the cost of the remote handling modifications. I'm not sure whether or not some type of solid film lube would help (or last). I've talked to the wrench vendor and they "allow" the wrenches to be used without lubrication (mostly in nuclear applications), but strongly caution about the degradation.
Significant testing was done early on to determine the torque required to ensure proper sealing. We installed a target a couple of years ago that failed its seal test right away. We went back and tightened the bolts a little bit more (who knows how much?) and the test passed, so we incorporated that torquing info into our procedure. Ever since then, the seal performance has been fine until this current target.
Bottom line, hearing all of this discussion (which I really appreciate) and thinking about ways to integrate some of these new ideas brings me back to simply ensuring that the torque we are applying is reasonably accurate. This can be by measuring the torque output of the wrenches in the cell (some sort of torque tester) or by utilizing a wrench that doesn't rely on air pressure (electric wrench). The techs seem to think the electric wrench is do-able, but we would need to modify it to enable the torque adjustment remotely.
These kinds of problems are what I deal with every day. I just got back from a demo of a video scope. The ones we have been using cost > $50k each and last about 1 hour in the radiation environment. Of course, the targets cost >$1 million each, so learning about their failure modes is important. We are going to hang one of these targets vertically from a crane and drill holes in the nose tomorrow. That is always interesting...