3 Essential Features Your NDT System Needs To Get the Job Done

By Dirk Steiner / October 21, 2014
Too much of the wrong data from your non-destructive test (NDT) system can be overwhelming, and incomplete data can sabotage your test strategy and negatively impact production. Some Computed Tomography (CT) machines can examine samples using different imaging techniques, so how you can select the right CT system features to generate better image results for your specific application? Here, we examine different imaging features that work best for different application tasks. 

1. Laminography
Let’s start with Laminography. In this type of X-ray testing, the CT system produces images of object slices using a linear translation of the object relative to the tube-detector system. If digital radiography cannot create a “good enough” image for your need, then Laminography may create better results. This is typically used when large samples can’t be rotated at least 180 degrees inside the CT system and a high resolution image is required. Laminography eliminates the need for the sample to rotate. Instead, it penetrates in different angles and the image is processed by a special algorithm. The result is not 100% comparable with CT, as the information in the slice is also influenced by features outside the so called “focus plane”.

2. Helical Computed Tomography
Another technical feature available is Helical CT (sometimes mistakenly called spiral cone beam Computed Tomography). This way of CT scanning has two aspects. First, it can generate a single, seamless 3D dataset for “long” objects, such as a pencil-shaped object. And second, it creates better images when a normal cone beam CT would generate some blur at high wide cone beam angles. Rotation of either the sample or the X-ray source and array of detectors is required. This method can produce high quality images rather quickly if the CT system’s software is efficient in processing the mathematical measurement data.

3. Scan Mode
A nice feature of a CT imaging system is the ability to run different imaging scan modes. On a state-of-the-art, industrial CT system, different modes allow you to select different acquisition modes. Some systems may only support “stop-and-go.” This is where the turntable stops to rotate for every projection, whereas others also allow a continuous motion. This is much faster and can still create very nice results if implemented correctly. On low end systems, the turntable will just rotate and images from the detector will be captured, assuming the turntable turns at a certain constant speed. Better systems can synchronize the detector with the turntable position.

Lots of CT systems tout sophisticated technical features, but keep in mind your purchase of a CT system will be deemed a success based on whether or not it works for your specific needs. When it comes to selecting the right NDT CT system for your application, sure, a picture is worth a thousand words. Just make sure your picture is saying the right things about your production sample.

NDT-computed tomography guide