Furnace adapted to contain molten metal

In a furnace, which is adapted to hold molten zinc, molten aluminum, or other molten metal, a combination comprising:

• (a) an outer vessel, which has lateral and bottom walls,
• (b) a removable, seamless, vacuum-formed, ceramic-fiber, one-piece, inner vessel, which is adapted to contain the molten metal, which has lateral and bottom walls, and which is fitted into the outer vessel so as to leave sufficient clearance around the inner vessel, between the lateral walls of the inner and outer vessels, for particulate matter to be packed around the inner vessel, between the lateral walls of the inner and outer vessels, and
• (c) a mass of unbonded particulate matter, which is packed around the inner vessel, between the lateral walls of the inner and outer vessels, so as to lodge the inner vessel laterally within the outer vessel despite nonconformities between the lateral walls of the inner and outer vessels, and so as to enable the inner vessel to be lifted readily from the outer vessel,
• (d) a layer of said matter, which is packed on the bottom walls of the outer vessel, between the bottom walls of the inner and outer vessels, so as to support the inner vessel and its contents firmly despite nonconformities between the bottom walls of the inner and outer vessels, and
• (e) an electrical circuit including electrical conductors, which are imbedded within the layer of said matter on the bottom wall of the outer vessel, said matter being packed so as to be previous to the molten metal, the electrical circuit not being attached to the inner vessel, the electrical circuit being open in normal operation of the furnace, the conductors being arranged to close the electrical circuit if any of the molten metal leaks from the inner vessel, perfuses said matter, and bridges the conductors, the electrical circuit including a signalling means, which is arranged to emit a signal if the electrical circuit is closed.