Oven heating coil

The bottom heat of an oven had failed after about 8 years. Upon removal, the outer tube was found to be broken umpteen times and almost oxidized through; the insulation material was easily crumbled out. The sheathing of austenitic stainless steel contains only a thin layer of metal in the center. The heating wire consists of a Ni-based alloy with approx. 28% chromium.