The drain or stone washing resistant to fire and the gas permeavel

摘要

PCT No. PCT/AT89/00035 Sec. 371 Date Nov. 28, 1989 Sec. 102(e) Date Nov. 28, 1989 PCT Filed Apr. 13, 1989 PCT Pub. No. WO89/09836 PCT Pub. Date Oct. 19, 1989.Refractory, gas-permeable bubbling plugs for a vessel containing a molten metal have a cold end remote from the molten metal and a hot end facing the molten metal. The hot plug end is subject to wear by the heat radiated from the molten metal to leave a remaining plug size after wear, and such plugs comprise at least one measuring probe displaying the remaining plug size. According to the invention, the measuring probe comprises a small tube having a tip extending into the plug and spaced a predetermined distance from the cold plug end, and an end section protruding from the cold plug end, a wire movably mounted within the small tube, a spring preloading the wire, a connection connecting an end of the wire to the tip of the small tube and detachable by the effect of the radiated heat, and an optical display unit attached to the wire in the protruding end section of the measuring probe tube.