Most inservice examinations are performed by nondestructive testing service providers as directed and specified in contractual documents. Most often, these documents will specify the nondestructive examination method and/or technique, the type of condition/ damage to be found, and the extent/location to be examined.
In many cases, the contract may also indicate the original code of construction for guidance. For example, if the item to be examined is a pressure vessel, the original construction code would be ASME Section VIII, which would direct the user to Section V for volumetric examinations. If the desired examination is an ultrasonic phased array technique to detect thermal fatigue cracking, the user would then be directed to Section V, Article 4.
The service provider is contractually bound to follow examination criteria developed to detect welding flaws from the fabrication process. These requirements and essential variables are used to develop the examination procedures to locate flaws influenced by bevel angles, fusion zones, volumetric location, etc. The calibration and demonstration blocks are constructed to successfully accomplish this type of examination.
Unfortunately, the inservice examination is concerned with smaller internal surface flaws that often propagate at significantly different angles than the normal orientation of welding flaws. As a result, the service provider is now utilizing a contractually required technique designed to detect fabrication flaws, which is not appropriate for the type of examination needed to accurately detect the inservice-related damage. This could easily result in undetected flaws with serious consequences.
In many instances, there may not be a contractual requirement that directs the examination provider specifically to Section V; however, for pressure technology components, there’s no alternate source that provides granular examination details from which to develop the examination procedure. In these cases, the onus lies with the service provider to have the experience and knowledge to modify the requirements in Section V to prepare an examination procedure that can accurately pivot from fabrication weld flaws to inservice-related damage mechanisms. Again, this scenario could easily result in undetected flaws with serious consequences.
Read the related article "ASME Section V Now Includes Dedicated Section for Inservice NDE."