Heat insulator for pipe lines

A heat insulator for pipe lines with an outer periphery and used for transporting low-temperature fluids, said insulator comprising in combination:

• a plurality of longitudinally divided hollow heat-insulating units assembled to tightly cover the outer periphery of said pipe lines, each heat-insulating unit including:
• a heat-insulating panel element made of a rigid foamed synthetic resin with an outer periphery and having a shape of circular cross section to fit the outer periphery of said pipe lines:
• a stress-absorbing sheet overlaid on the outer periphery of the rigid foamed synthetic resin and integrally combined with the foamed synthetic resin of said heat-insulating panel element and being capable of absorbing stress caused by shrinkage of said heat-insulating panel element at low temperature to prevent any dimensional difference therewith;
• an outermost thin metal plate placed on the outer surface of said stress-absorbing sheet and integrally combined therewith to prevent any dimensional difference between the integrally combined sheet and the outermost thin metal plate against external compression caused by supercooled fluid passing through the pipe lines;
• and
• means for holding together adjacent heat-insulating units combining two kinds of heat-insulating materials for higher and lower temperatures as joint sealer.