APPARAT FOR TINING AV FROSNE ROER

摘要

An electric pipe thawing apparatus for thawing frozen water pipes by passing electric current therethrough incorporates various safety feature rendering the apparatus fail-safe in operation. The apparatus includes an A.C. generator from which can be obtained through a step-down transformer arrangement various voltage levels, from 12 volts upwards, for applying low voltage high current power to the pipe to be thawed. One important safety feature prevents the application of a higher voltage to the pipe unless at a lower voltage level, for example, 20 volts, it has been established by measurement that the current flow in the pipe is above a predetermined level and consequently the circuit through the pipe is a good one. If the circuit is not good, when the operator switches to a higher voltage level a danger signal is illuminated. An automatic tripping feature can be built into the apparatus to interrupt the application of power to the pipe should a higher voltage be applied to a pipe heating circuit which is not a good one as determined by the current flow at the lower voltage.