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we had a mechanical torque tester and the intent was to put it into the cell and then calibrate/validate the torque vs pressure curves prior to an operation. We didn't put the tester in the cell because we needed it outside the cell to calibrate/validate new wrenches and once something goes in - it never comes back out. We then tried an operation where we took the torque tester into an airlock room where we could bring the wrenches out and test them. That wasn't optimal because we couldn't replicate the pressure drops in the cell and then...we broke the torque tester and the manufacturer hasn't made them in a while so they balked on fixing and re-certifying it. .
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Just wondering what apparatus you use to determine the torque that need to be applied?
Also what degree of accuracy is needed?
Skidmore makes some very robust and accurate tension measuring devices, this will allow you to know how many rotations from snug you need to turn a bolt to reach design tension... Often this is read as torque on a wrench when the bolt is in motion..But you know this already...
You can put witness marks on the fixed part, and another witness mark or series of witness marks on the chuck and you can know with a high degree of accuracy how much you have turned the bolt (nut)
You can probably tell I am a big fan of using ganged hydraulic jacks to tension fasteners. We have tensioned cable saddle bolts 300 feet in the air on a bridge tower.... and we had more access than you appear to have...
Interesting problem...and I will definitely be thinking of solutions