Radiant tube arrangement for high temperature, industrial heat treat furnace

A standard atmosphere furnace constructed of a steel casing formed as a cylinder with fibrous insulation attached is operated as a vacuum furnace. A plurality of radiant, fuel-fired ceramic heat tubes positioned in a centered but circumferentially spaced arrangement provides heat input to the furnace to permit it to operate at high, vacuum associated temperatures. The ceramic tubes are vacuum sealed to the furnace case by an elastomer seal/water jacket arrangement which uses an outboard clamp arrangement to establish a ceramic-to-metal contact to permit thermal cooling and prevent tube-flange movement so that the integrity of the elastomer seal can be maintained. In addition, an articulated joint connector is provided so that the tube can be supported in a pivotable manner permitting thermal movement while reducing tube stress to prolonged tube life.