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March 14, 2017
The Truth Behind Composite Inspection Methods

Posted by: Casey Whalen

“Are your composites inspectable?”

It’s a question we hear a lot, which leads us to believe that there may be confusion in the market about whether or not every composite pipe repair solution can be inspected using common methods. Because today’s inspection standards regarding composites can be vague, and pipe infrastructure owners are typically referred to the repair system supplier for inspection, it’s reasonable that an understanding of composite repair materials and testing methods is not where it should be.

To answer the question though, yes, all Milliken Infrastructure Pipe Wrap composites are inspectable. In fact, there are inspection methods for just about any composite repair system that’s on the market today, with six methods that are used more widely than others.

Each method has its advantages and disadvantages, of course, but what is most important is to know that there are inspection methods for almost any situation. In a series of upcoming articles, we’ll discuss the following non-destructive testing (NDT) methods and delve into their effectiveness on today’s most common composite repair systems:

  • Phased Array: This form of ultrasonic NDT uses dozens of independently pulsing transducers that can be swept at a variety of angles to locate defects. This method can be used to inspect both the bond line and in the pipe wall.
  • Guided Wave: Another form of ultrasonic testing, the guided wave method can detect, characterize and visually present delamination defects in a composite structure.
  • Pulse Eddy Current: This NDT method, based upon Faraday’s Law of Magnetic Induction, is an electromagnetic testing method that measures the strength of eddy currents to detect defects in conductive materials. This method can be used to inspect the underlying pipe wall through the composite.
  • Digital Radiography: Also known as X-ray, this method uses penetrating radiation to inspect delamination and disbonding within the materials being tested. This method can find defects in both the composite and in the pipe wall.
  • Microwave: This method is used to detect defects such as delamination and gouges in nonmetallic materials, making it possible to view surface defects of steel pipe underneath a composite repair.
  • Thermography: By detecting the change in thermal activity within a material, thermography can find defects by creating a heat map of the surface of a stressed object. This method can find defects within the composite.

Though it’s elementary, it’s important to understand what each of these methods is testing for. Yes, they’re looking for defects, but there are several levels at which the defects can occur. Beginning with the pipe wall and working outward, defects or damages can exist in three main areas: in the substrate – in this case in the repaired area itself; the bond line between the substrate and the composite and finally within the composite repair itself.

Smart Pigs, or inline inspection (ILI) systems, are certainly the most widely recognized method of pipeline inspection but even where these may not get the desired composite repair inspection results 100 percent of the time, there are still a number of viable inspection alternatives. As ASME PCC-2 has little to say about composite inspection, with only a mention of a tap test, it’s important to know what the more sophisticated methods are, and more importantly, that you don’t need to base your purchase of a composite repair solution on sly marketing that suggests only specific composites are inspectable.  

To keep up with the conversation and to make sure you don’t miss our upcoming articles in this series, be sure to subscribe to Milliken Infrastructure’s RSS feed or sign-up to get updates via E-mail.

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Category: Pipe Wrap

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