EMF CHANGES MADE BY COLD DRAWING AND HEATING TREATMENT IN TYPE K HEAVY-GAUGE SHEATHED THERMOCOUPLE CABLES

Introduction　　 The need to getheavy- gauge sheathed thermo-couples( d> 8mm) is unusual,but sometimeswe must use them due to certain reasons,especial-ly,measuring the surface temperature of heatingfurnace pipe and flue.Because of its thick metalclad,such heavy- gauge sheathed thermocouplescan endure long periods in high- temperature andcorrosive environment.Their lifetime are severaltimes higher than thatof common ones.They maybe widely used in oil refinery,chemical industryand power station…

EMF CHANGES MADE BY COLD DRAWING AND HEATING TREATMENT IN TYPE K HEAVY-GAUGE SHEATHED THERMOCOUPLE CABLES

The electromotive force (EMF) changes in type K heavy gauge sheathed thermocouple cables was investigated. To cope with this discrepancy owing to EMF steep reduction and understand the difference between type K heavy gauge sheathed thermocouple cables and small ones, the affects of EMF from sheath pipe, drawing times, annealing temperature, annealing time and annealing way were mainly studied and appropriately analyzed. The results show the change in the thermal EMF is related with the residual stress and crystal defects, which are imparted by cold work during manufacture. The affects of cold work can be removed by annealing. Finally, a feasible way of fabricating heavy gauge sheathed thermocouples was suggested according to practical situation.