SA179 Tension-Wound Finned Tubing

SA179 Tension-Wound Finned Tubing

Tension-wound finned tubing is widely used due to its relatively low cost. The fins are formed by winding a strip of the fin material around the tube under tension. The metal strip may be either straight (edge-wound or I-fin) or bent in the shape of the letter L (L-footed or L-fin). The latter configuration provides more contact area between the fin strip and tube surface and also helps protect the tube wall from atmosphere corrosion. Better adhesion and corrosion protection can be achieved by overlapping the “feet” of the L's (LL-fin). The strip metal is subjected to controlled deformation under tension to provide good contact between the strip and the tube wall. Collars at both ends of the tube hold the fin strip in place and maintain the tension. Nevertheless, since the fins are held in place solely by the tension in the metal strip, they can be loosened by operation at high temperatures or by temperature cycling. Therefore, this type of tubing is used for continuous services with tube-side temperatures below 400°F (below 250°F in the case of I-fin).