Patent ID: 7037557

Claim:
A method of preventing disbondment of a surrounding foam insulating layer in a bonded foam type pre-insulated piping system, the method comprising the steps of: providing a first and second length of insulated and jacketed pipe, each having a joining end to be joined to an end of the other length, each pipe length comprising an inner steel pipe having an interior surface and an exterior surface; spraying a layer of a thermally protective ceramic coating onto the exterior surface of the inner metal pipes; spraying an envelope of foamed insulation which surrounds the inner pipes exterior surface and envelopes the inner pipes; applying an outer protective jacket, formed of a synthetic polyolefin, which surrounds the envelope of insulation, the joining ends of adjacent pipe lengths being welded together to form fixed joints, whereby the adjacent pipe lengths provide a continuous fluid conduit for conveying high temperature fluids; wherein the thermally protective ceramic coating is applied in a predetermined thickness range which is effective to reduce the temperature of the inner metal pipes at the interface layer to below that at which disbondment of the foam insulation would occur and thereby prevent separation of the envelope of foamed insulation from the exterior surface of the inner metal pipes as the temperature of the inner metal pipes increase; and wherein the foam insulation which is used to surround the inner pipes is a high temperature polyisocyanurate foam.