fazel1;
ASME Code Case 2235-9 allows for the ultrasonic test (UT) method to be used in lieu of RT for material 1/2" or greater in thickness in boilers and pressure vessels. You have to develop a scan plan (ultrasonic beam angle, direction and volume of weld metal, etc.) and have to develop a written procedure for the UT method in accordance with Article 4 of ASME Boiler and Pressure Vessel Code, Section V.
I am not going into greater detail, you need to obtain a copy of this CC and review it. However, if you want to wait until the 2007 Edition of the ASME B&PV Code, the SG on FE and SCI on Power Boilers will be integrating this Code Case in PW-52 with a new Appendix A-280.
ASME Code Case 2235 contains an ultrasonic defect acceptance criterion based on defect height vs length vs through weld location in line with a fracture mechanics analysis. Generally only automated or phased array UT will allow the necessary proven accuracy in defect height measurement to justify its use. AUT has proved to be highly-effective for pipeline girth weld testing where the high set-up costs are offset by the speed and efficiency of the test.
In January this year ASME issued Code Case 181 for B31.3 Process Piping which appears to be identical.
