Abstract: A flowing pressurised gas is heated by being conveyed through a gap (18) between two concentric tubes (16, 17) in a pressure vessel (11, 12, 13). The inner tube (17) is heated by radiant heat from inside and the tube is kept open towards the flow path of the gas in the pressure vessel so that pressure equalisation is obtained between the inside and outside of the inner tube without the tube being part of the flow path of the gas.

Abstract: In continuous casting of steel, the flow out of the tap hole (11) in the tundish (10) is controlled by a stopper rod that is rotatable so as to give the molten steel a swirling motion. This rotation reduces the risk of deposits in the tap hole and in the discharge tube (12). A non-rotatable sleeve around the stopper rod (16) extends through the slag layer (18) and into the molten steel (17). Protective gas is supplied to the gap between the stopper rod (16) and the sleeve (30) to prevent air from being drawn through the gap and into the molten steel.