DOUBLE WALLED TUBING AND PROCESS FOR PRODUCING SAME

摘要

Double walled tubing, a method and apparatus for producing the same are disclosed. First and second metal tubes of substantially identical diameters are selected. One end of the second tube is expanded, and the first tube is pushed into the second tube. By mounting the first tube on a mandrel having a mandrel ball with an outer diameter which approximates the inner diameter of the first tube, any creases in the first tube caused by the insertion will be removed by the mandrel ball upon withdrawing the mandrel from the first tube.