Flexible line element with thermal insulation

Device for a flexible gas type connection of pipes, the device including a bellows, and connecting pieces joined to said bellows at opposite ends thereof, said connecting pieces being adapted to be connected to opposed ends of the pipes, and an insulation extending between the connecting pieces, wherein the insulation includes a double tubular insulating cassette of a cassette casing filled with a heat-resistant thermal insulating material, the cassette casing covering the heat-resistant thermal insulation material both on an outer and an inner side thereof, wherein the cassette extends into an interior of both connecting pieces, and means for sealing and for retaining the tubular insulating cassette is gas tight connection to the interior of said connecting pieces, and wherein said means includes a seal provided at least between the insulating cassette and at least one of the connecting pieces, said seal slidingly engaging an inner side of said at least one connecting piece.