Modular heat insulation, manufactured as separate welded blocks of stainless corrosion-resistant steel, arranged on the pipeline outer surface. The boxes are filled with heat-insulating material and interconnected with quick-acting tension locks. The cover plates shield the block joints. A heat-insulating material being a set of minimum three corrugated or blistered shields is used. These shields are manufactured of stainless corrosion-resistant steel forming enclosed air cavities. The external lining sheets of the adjacent blocks are shorter than the blocks themselves by the size of the cover plates and are installed with a lateral ventilated gap from the external surface of the shield set. The cover plates shall have the shape of mated sections with a multilayer set of corrugated stainless corrosion-resistant steel sheets. The mated sections are quick-acting tension locks, and their cover plates have width overlapping the area of blocks' increased temperature within their joints.