Abstract: In a method of making a fibrous thermally insulating layer of coherent structure, a quantity of fibers is treated with a binder, whereby prior to or during the treatment with the binder, fibers are formed into a quantity of particles each having a substantially rounded periphery and consisting of a number of short fibers and the particles treated with the binder are conveyed by means of a gas as conveying medium via an inlet piece 11, 13 to within a container 3, the particles being blocked by an outlet piece 8 for the container, the outlet piece 8 being formed with gas outlet apertures 10.The particles are formed by vigorously agitating a number of flakes in a vessel, each flake consisting of arbitrarily arranged short fibers, and simultaneously applying pulsating forces to at least part of the volume of flakes, so that the flakes are converted into particles having a substantially rounded periphery and having a higher density than that of the flakes.

Abstract: Heat-insulating pipe element of a pipe for conveying flue gases comprising a metal outer tube, a metal inner tube fitted co-axially in the outer tube by fixing means in a substantially immovable relation to the outer tube and a heat-insulating material being provided in the space between the tubes, whereby the fixing means comprises at least one elongate connecting element which is provided in longitudinal direction between the tubes and of which the extremities are connected with the respective end parts of the outer tube of which the central part is connected with the central part of the inner tube, and whereby the fixing means also comprises the insulating material, in the form of a continuous insulating layer, having a coherent, fibrous resilient structure.