Back to Basics: Mastering Magnetic Particle Inspection
Some companies’ nondestructive testing (NDT) methods and procedures-or lack thereof-particularly with regard to magnetic particle inspection can be disconcerting. This type of information most often comes from companies outside the aerospace industry that perform their own in-house magnetic particle inspection.
Companies will start up an internal NDT process for various reasons. For some, it is a customer requirement, while others perceive it as an internal quality check during the manufacturing process. In most cases, the companies decide to invest in the equipment, but fail to recognize the importance of getting their employees properly trained. After all, “how hard can it be?”
Another area often overlooked by these companies is the ancillary equipment necessary to properly monitor the system operation and the method process, such as light meters, shot timers and gauss meters.
A study done in 1973, titled “An Investigation in the Effectiveness of Magnetic Particle Testing,” by Lee R. Gully Jr. reported on the failure to properly apply magnetic particle inspection methods. The study estimated that the 11 companies under scrutiny detected only 47% of the discontinuities present. Ten years later, another study by D.J. Hagemaier, titled “A Critical Commentary on Magnetic Particle Inspection,” found that little had changed.
Based on observations and discussions with those in the industry, the following are concerns that stem from improper training in the magnetic particle testing method.
Not much has changed in the 36 years since the first study was accomplished in 1973. This can be attributed to the failure to receive adequate formal training to qualify operators or inspectors, as well as a basic lack of knowledge about the process and theory, the test equipment and all the quality control checks that must be implemented in order to perform an effective inspection.
The aerospace industry relies heavily on the NDT industry as a valuable tool for identifying defective parts and equipment prior to placing them into service, saving time, money and lives. However, when employed improperly by untrained individuals, it can lead to a false sense of security-“we know we have a quality product because we did our own testing”-which can lead to escapes, failures, recalls and ultimately injury or worse. Not only is it important that the operators be well-trained, it is equally important that they fully understand their equipment and the operation.