as the ceramics based preferably silica based micro pore thermal insulators such as are described in the above cited patent it is understood that the thermal insulator may be slightly or substantially warped when implementing the flutings it is understood that the fluting geometries may vary illustratively the width w of as fluting 5 may be between 1 mm and 10 cm when the cross section of the fluting is constant and the distance d between two consecutive flutings may be approximately between one fourth the diameter of the fluted shell and triple this diameter in a particular illustrative embodiment the pipeline 1 may consist of an inner shell 3 which is 12 7 mm thick and has an outside diameter of 273 mm and of an outer shell 2 which is 6 35 mm thick and has an outside diameter of 324 mm thus bounding an annular space 7 which is 19 mm wide before fluting shaping takes place and wherein is mounted a micro porous insulator illustratively 15 mm thick allowing flutings 10 mm deep and 4 mm wide at their bottom and spaced by about 30 cm from each other in this embodiment the bottoms 6 advantageously compress the insulating material in such a design.