FIELD: insulation of pipe lines. SUBSTANCE: envelope includes radially slotted tubular member made from mineral fibers oriented in planes perpendicular to longitudinal axis of tubular member; sheet material is secured to external surface of tubular member by means of adhesive; envelope embraces pipe lines; before fitting the envelope on pipe line, it is subjected to alternate compression and tension in axial direction in area where tubular envelope should insulate bend of pipe line. EFFECT: enhanced efficiency of insulation of bent sections of pipe lines. 6 cl, 3 dwg
