Abstract: A hermetic expansion joint for use between conduits lined with refractory material and a tuyere stock for blast furnaces utilizing a plurality of such expansion joints. The expansion joints include a bellows coaxial with and connected to the exterior of the conduits to be coupled and, located within the bellows, a shielding tube and a protective layer of compressible refractory material. The compressible refractory layer is positioned within the shielding tube and bridges the joint between the conduits.

Abstract: A hermetic expansion joint employing an external bellows and means positioned within the bellows for limiting the relative axial displacements of the conduits being joined in both compression and tension. The expansion joint device has, located within the annular chamber defined by the bellows, a layer of compressible refractory material which bridges the joint between the conduits and a shielding tube which envelopes the compressible refractory material. The expansion joint device is further provided, on oppositely disposed fittings which connect the bellows to the conduits, with means for limiting the axial width of the joint.