We have had our share of issues with threaded drill stems, we also have a coker set which still uses hexagonal single piece drill stems which have thier own unique issues. Largely the threaded stems are trouble free if you pay attention to them and perform periodic inspection of the joint transitions. We also utilize a number of interlocks which reduce the shock loading on the assemblies, and are currently looking at the autoswitching tools which has been successful in elliminating strain on the stem due to coke falls. We also have to continually slow turn our rotary joints as they freeze up when the temperatures approach -40C. I’d be most willing to share any insites you have on the topic.
