SUPPORTING SHELLS MADE OF METAL FOR COVERING THERMAL INSULATING MATERIAL MADE OF THERMOPLASTIC OR ELASTOMERIC FOAM IN THE FORM OF PIPES, TUBES, OR CYLINDRICAL SLEEVES WHICH CAN BE OPENED AND CLOSED ALONG A LONGITUDINAL SLOT, WITH OR WITHOUT SUPPORT SEGMENT INSERTS MADE OF RIGID FOAM; PIPE SUPPORTING ELEMENT CONSISTING OF A SUPPORTING SHELL MADE OF METAL