Inspection Trends / Fall 2011 29 particular situation. It is important for the CWI or SCWI to recognize a situation in which the best NDE method for a particular set of circumstances is in use and determine if that method is indeed being employed. The certified inspector is expected to recognize the proper application of each major method. While the AWS CWI is not required to be certified in any NDE method, he or she is expected to be able to identify each method and process, and its proper application. AWS B1.10M/B1.10:2009, Guide for the Nondestructive Examination of Welds, Annex A, “Examination Method Selection Guide,” offers an excellent synopsis of the equipment needs, applications, advantages, and disadvantages of the eight most common and popular NDE methods. This will present a good review for knowledgeable individuals and perhaps broaden the knowledge base of others who may not deal with each of these NDE methods on a regular basis. Annex A begins on page 28. Lyndsey Deckard (Deckard@ pbworld.com) is quality manager of the Vehicle Division of Parsons Brinckerhoff Transit & Rail Systems, Inc. He is an AWS Senior Certified Welding Inspector, an ASQ Certified Quality Auditor, and a member of the AWS Certification Committee, Examination Question Bank Subcommittee, and Ethics Subcommittee. Examination Method Selection Guide Typical Equipment Applications Advantges Limitations Radiography (X-rays) X-ray sources (machines), Same application as Same as previous page, except High initial cost of X-ray electrical power source, same previous page. that X-ray radiography can use equipment. Not generally general equipment as used with adjustable energy levels, and considered portable. Also, gamma sources (previous page). it generally produces higher same limitations as quality radiographs than previous page. gamma sources. The process also enjoys the same advantages as previous page. Ultrasonic Pulse-echo instrument capable The method can detect most The method is most sensitive Surface condition must be of exciting a piezoelectric weld discontinuities including to planar-type discontinuities. suitable for coupling of material and generating cracks, slag inclusions, and The test results are known transducer. A liquid couplant is ultrasonic energy within a incomplete fusion. It can also immediately. The method is required. Small, thin welds may weld, and a suitable cathode be used to verify base metal portable, and most ultrasonic be difficult to inspect. ray tube scope or digital display thickness. flaw directors are battery Reference standards and a capable of displaying the operated. The method has relatively skilled operator or magnitudes of received sound high penetration capability. inspector are required. energy. Calibration standards, Method may be used when Materials with large grain liquid couplant. access to only one side of the structures may be difficult to joint is available. inspect. The method is less sensitive to rounded discontinuities. Eddy Current An instrument capable of Detection of discontinuities Equipment used with surface Relatively shallow depth of inducing electromagnetic fields on or near the surface. Alloy probes is generally examination. Many material within a weld and sensing the content and heat treatment lightweight and portable. and test variables can effect the resulting electrical currents condition may affect results. Painted or coated welds can test signal. (eddy) so induced with a be inspected. The method can suitable probe or detector. be partially or completely Calibration standards. automated for a high speed, relatively inexpensive examination. Leak Testing Leak testing requires a gas or Detection of through- Relatively cheap and easy to Requires a source of water or liquid medium, a pump to thickness discontinuities do if visual detection of leaks other medium, a means of apply a differential pressure to is possible. Special mediums disposing of the medium, and one side of a weldment and a such as helium require more the weldment may require device to contain the pressure if sophisticated equipment to cleaning after testing. the weldment is not a closed detect. However, helium leak structure. A detection testing is very sensitive. instrument if the medium penetrating the weld cannot be detected visually may also be required.
Inspection Trends - October 2011 - Fall
To see the actual publication please follow the link above