Metal over-sheathed electrical resistance heater for welding

摘要

The well heater comprises a tubular metal oversheath encasing both a number of metal surfaced heating strands and another metal surfaced strand. The metal surfaced strands are parallel to each other and the oversheath, and the oversheath is compressed radially inward to establish metal-to-metal contact between it and the strands within an assembly which is spoolable and is impermeable throughout its length. The heating strands include a number of electrically conductive cores capable of resistive heating and surrounded by solid insulation contained within a metal sheath are positioned and interconnected in an arrangement providing a combination of electrical resistance per unit length of the well heater such that the heater is capable of generating heat at different rates along different portions of its length. - Electric current is supplied to the heating strands. Two heating elements are arranged end-to-end and electrically connected in series.