Abstract: Pipes used for carrying hot fluids such as steam and process liquids and gases, often above 212.degree. F., and pipes for carrying cold fluids such as for refrigeration and air conditioning systems, are usually insulated where they extend for any appreciable distance in areas of different temperatures, for reducing heat transfers. Such pipes are used in central heating and cooling distribution systems for cities, schools, universities, prisons, military bases, in industrial processing plants, and the like, whether installed above ground or underground. Polyisocyanurate and similar foamed insulation materials including polyurethane are better insulators than those now commonly used, such as foamglass, fiberglass, mineral wool, and calcium silicate; polyisocyanurate has a very low K factor and is stable at up to 400.degree. F. for sustained temperatures and up to 450.degree. F. peak temperatures.

Abstract: A method of making insulated pipe joints in the field. The method includes the steps of providing a rigid shroud which is larger than the fitting from fitting end to fitting end, welding a first pipe length to a first end of the fitting, moving the shroud over the fitting to project the second end of the fitting beyond the second end of the shroud, welding the second pipe length to the second end of the fitting, centering the shroud on the fitting, enclosing the gaps between the fitting shroud and the shrouds of the pipe lengths by mold members, pouring a foamable insulation into the space between the fitting and fitting shroud and into the gaps, setting the insulation, removing the molds to expose the gap areas, and thereafter applying a protective coating to the gaps which coating overlaps the fitting shroud and the pipe length shrouds.

Abstract: Insulated jacketed conduit units sealed in end to end relation by expansion couplings are insulated, sealed and spaced at the coupling zones with protective combined spacer and sleeve rings or washers which surround the coupled ends of the conduits, are bottomed on and squeezed between the insulation of adjacent units to position the conduit ends for expansion and contraction without breaking the seal therebetween and seat on adjacent ends of the jackets to protect the insulation. The combined spacer and sleeve rings or washers can be molded to have a relatively soft compressible inner washer portion and a tough stiffer sleeve portion with resilient sealing lips in the open ends thereof for sealingly engaging the jackets.