Patent ID: 8365775

Claim:
An insulated tubing assembly comprising: a first, metallic outer tubular body having an inner cylindrical surface, a second, metallic inner tubular body having an outer cylindrical surface and a layer of insulating material applied to said outer cylindrical surface, said first and second tubular bodies being substantially coaxial and forming an annulus therebetween; said first and second tubular bodies being of a type employed in oil and gas well operations, one of said first and second tubular bodies having first and second ends comprising a threaded connection; and at least one, monolithic metallic centralizing ring disposed in said annulus between said first and second tubular bodies and welded to said outer cylindrical surface of said inner tubular body, said centralizing ring comprising a ring body, said ring body including a circumferential gap whereby said ring body can be diametrically expanded for assembly onto said inner tubular body, said ring body having an annularly extending, radially outwardly facing surface and an annularly extending, radially inwardly facing substantially cylindrical surface, and a plurality of circumferentially spaced, projections extending laterally outwardly from one of said radially outwardly or radially inwardly facing surfaces, said projections being curved in both an axial and radial direction, for forming a line contact in a single radial plane transverse and passing through an axis concentric with said first and second tubular bodies, with one of said inner or outer cylindrical surfaces, depending on whether said projections are on said radially outwardly facing surface or said radially inwardly facing surface to minimize heat loss from said inner tubular member.