{HEAD ~ driving means} for rotating {TAIL ~ the tubular member}, electrode and conduits about the elongate axis of the tubular member in first and second directions having a reversible electric motor to provide a driving force and a system of gears for transferring the driving force from the electric motor to the tubular members; and 
{ HEAD ~ driving means } for rotating { TAIL ~ the tubular member } , electrode and conduits about the elongate axis of the tubular member in first and second directions having a reversible electric motor to provide a driving force and a system of gears for transferring the driving force from the electric motor to the tubular members ; and
HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH