Introduction
Reduced radiation exposure times and high resolution characterize digital radiography testing (RT) techniques. The changes are so remarkable that they have resulted in groundbreaking RT functions over the last 15-20 years. Some applications are new, while other RT inspections performed sporadically when using film are now performed more frequently using digital detector array (DDA). DDA allows us to conduct more efficient inspections using fewer consumables (less film and chemicals). This article will examine and use images to illustrate some common DDA applications, such as:
- Raised flange face inspections of NPS 4 and under flanges,
- ASME code-compliant weld quality DDA RT of as-fabricated pressure piping using bendable panels,
- Close proximity radiography is becoming even closer proximity, and
- Material loss estimations (MLE) – a pit depth measuring tool.
Raised Flange Face Inspections of NPS 4 and Under Flanges
Corrosion loss on the raised face of flanges can reduce their sealing effectiveness. It can also impact the reliability and safety of the pressure system. For example, a customer tried different ultrasonic testing techniques to identify flange face defects (losses) in NPS 4 and smaller flanges. However, they were unsuccessful because of the small size and unfavorable geometry of the faces. Consequently, they initiated a blind study of 13 staged sets of flanges to evaluate if DDA RT could identify the material losses of the small flange faces. Each set of flanges bolted together had one side with known defects while the other was free of wear and damage. Based on the DDA examinations, the sides with defects were clearly distinguished from those without. Also, a rating system for slight, moderate, and severe defects was developed. With the technique proven in a controlled environment, it had to be adapted to a field environment. After a few days of setup and panel adjustments, the variances, such as radiation scatter and equipment alignment, were controlled and the panel settings were optimized. The flanges in question were identified in the field, and the customer confirmed the DDA RT findings.
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