Abstract: A long-distance heating conduit comprising one or more tubes conveying the heating medium, which tubes are supported in the conduit by support means consisting of an insulating material resistant to compression and surrounded by a heat-insulating material also resistant to compression and enclosed by cover foils having holes, the size and shape of which are dimensioned in such a manner that water substantially cannot penetrate, but that they are permeable to gases and vapors.

Abstract: A method of pickling metallic material particularly for the continuous treatment of material in strip or wire form and especially such material consisting of stainless steel, wherein the material after annealing is subjected in a first step to the chemical attack of a first aqueous solution which is heated to a temperature above room temperature, preferably to between 55.degree. - 60.degree. C, and which contains HF in contents of from 7 to 25%, or which contains HF in the contents mentioned above and H.sub.2 SO.sub.4 over 2%, or which contains HF in the contents mentioned above the NaCl up to 10%, but especially from 0.5 to 2.5%; or which contains HF in the contents mentioned above and H.sub.2 SO.sub.4 in the contents mentioned above and NaCl in the contents mentioned above, and in a second step the material is subjected to the chemical attack of a second aqueous solution heated to a temperature above room temperature, preferably to between 55.degree. - 60.degree. C, and containing HF and HNO.sub.3.

Abstract: A long-distance heating conduit comprising one or more tubes conveying the heating medium, which tubes are supported in the conduit by support means consisting of an insulating material resistant to compression and surrounded by a heat-insulating material also resistant to compression and enclosed by cover foils having holes, the size and shape of which are dimensioned in such a manner that water substantially cannot penetrate, but that they are permeable to gases and vapors.