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Originally Posted by john rogers
Torquing can be done by other methods besides using wrenches and multipliers. When I was in the Navy, I was involved with 5 reactor refueling operations with the older and smaller GE and Westinghouse 150MW reactors. In those cases the fuel is put in while the reactor cover is off and once all the fuel modules are in place the "lid" goes on. It has an omega seal welded around the circumference to prevent leaks and then the nuts are tightened on the studs. This was done by lubricating the nuts and studs threads with a graphite/alcohol solution, tightening the nut hand tight to a line on the vessel head. Finally a hydraulic stretcher was put over the studs (two 180 degrees apart) and the stud was stretched. If I remember correctly we used a stretch equal to 1,250,000 ft lbs of torque and I was always worried the whole machine would explode as we were on top of the lid watching the hydraulic pressure gauges and those studs would make all sorts of noises!
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BTDT.
when I worked on nuke generating plant turbines we used hydraulic stud stretchers, but we measured the stretch using ultrasound equipment that was accurate to about a thousandth.
Best part of that was that it took the coefficient of friction out of the equation. No more having to worry about the spot face or washer or thread lubricant etc.
Very accurate plus it would tell you if a crack was developing in the stud.
Bad part was, you had to remove the stud (up to 6 feet long) and machine both ends perfectly flat and parallel in order to get an accurate ultrasound reading.
