In the drift-expanding test, a conical mandrel is pressed into a tube specimen via materials testing machine according to the tube’s inner diameter and the tube is expanded. The test is ended when the value of the expansion defined in the specifications has been reached. The test is considered passed if no cracks are detected in the tube or at the welded seam after the test.
The drift-expanding test is normally performed on tubes having an outside diameter of 150 mm and a wall thickness no greater than 10 mm. For tubes without a detectable welded seam, the drift-expanding test is used as a replacement for the tube-flattening test.