Importance

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Abstract

Two outer steel pipes (16 and 16A) are each lined by corrosion resistant lining pipes (18 and 18A) of compressible plastics material which stop short of the ends (20, 20A) of the outer pipes to leave an annular recess or counterbore (24 and 24A) at each of those ends. A tubular bridging-member (2) of ductile, plastically deformable, corrosion resistant material, for example brass or stainless steel has two tubular end portions (4 and 6) extending in opposite directions from an intermediate tubular portion (8) having an outer diameter greater than that of the end portions (4 and 6) and an inner diameter greater than that of the said end portions. The end portions (4 and 6) are encircled by ribs (12). Initially the outer diameter of the end portions (4, 6) is less than that of the inner diameter of the lining pipes (18, 18A). Thus each lined pipe (16, 16A) can be fitted over the respective end portions (4 and 6) with the intermediate portion (8) occupying the combined counterbore (24, 24A). A tool applied internally, radially expands the end portions (4 and 6) to compress the plastics lining pipes (18, 18A) against the outer pipes (16, 16A) by an amount in the range of 8% to 30% of the wall thickness of the lining pipes. Then adjacent ends (20, 20A) of the outer pipes are welded together at 28. The outer surface of the intermediate portion (8) can carry heat insulation material. The bridging-member (2) preserves the integrity of the internal corrosion resistance across the joint between the outer pipes.

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First Claim