Development of Quality Assurance Method for PTT Cracking Tube for Ethylene Plant

Abstract

An ultrasonic flaw detector for newly developed cracking furnace tube for ethylene plant, named PTT, has been developed. PTT is an abbreviation for PPW Technology Tube which is internally overlaid with special combined nickel and chromium alloy by a plasma powder welding method and has features of outstanding anti-coking and anti-corrosion performance. The quality of the overlaid material, discontinuity at the weld interface and thickness of the layer, are inspected automatically by an ultrasonic search unit inserting into the tube in an immersion water tank. The defects which is equivalent to a 1.2mm flat bottom hole sensing is detected by 20MHz ultrasonic wave. The thickness of the base tube is measured with accuracy of 0.24mm by 5MHz ultrasonic wave. Furthermore, the thickness of the layer is calculated by the thickness change of the tube before and after overlaying