An insulated tube system, including an inner tube and an outer tube, each of the inner and outer tube including a corrugated wall having ridges and valleys arranged one after the other in the axial direction of the inner and outer tubes, and wherein the outer tube is arranged around and at a distance from the inner tube whereby a gap is formed between the inner tube and the outer tube, a thermally insulating layer arranged in the gap, the thermally insulating layer including a plurality of radial through-openings, each extending through the thermally insulating layer in a radial direction in the gap, and a plurality of radially flexible spacers, each spacer being arranged between the inner tube and the outer tube, each spacer including a top portion configured to contact the outer tube, the top portion having an axial extension along the axial direction of the inner and outer tubes, the axial extension being at least equal to the pitch of the corrugation of the outer tube, each spacer being configured to be compressed radially in response to a force exerted on the spacer by the outer tube, wherein each spacer is arranged in a through-opening in the thermally insulating layer.

The present invention provides a sheet-like thermal insulating material (flame barrier insulating laminate) that is shapable into a three-dimensional and has excellent handling properties, and a thermal insulating structure with a three-dimensional shape made from the laminate. The flame barrier insulating laminate comprises at least one flame barrier insulating layer and one prepreg layer. The flame barrier insulating layer is made of a sheet having a thickness of 0.1 to 3.0 mm, in which inorganic fibers with a heat resistance temperature of 1000 C. or higher are entangled in a random direction. The prepreg layer is a prepreg sheet in which an inorganic fiber base fabric is impregnated with a semi-cured thermosetting resin. The thermosetting resin of the prepreg layer in the flame barrier insulating laminate is fully cured, resulting in a flame barrier insulating structure with a desired shape.