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May–June 2022
Welcome to the The NDT Technician (TNT) newsletter! In this bimonthly email, we’ll round up the latest news and resources especially curated for the NDT inspector. Have a suggestion or feedback? Contact the editor, Jill Ross, at jross@asnt.org.  
Tips for Ultrasonic Flaw Length Measurement
Free e-Course: Introduction to NDT
Tips for Ultrasonic Flaw
Length Measurement
Does transducer diameter affect the accuracy of flaw length measurements? Read on to see how near field and beam spread can affect measurements [8 min read]. 
 
Free e-Course:
Introduction to NDT
How much do you know about NDT? Check out this free on-demand e-course from ASNT Learn, plus earn 3.0 contact hours (0.75 certification renewal point).
 
Short on Time?
Watch the Introduction to NDT video, narrated by ASNT Assistant Editor Cara Markland [37 min]. 
 
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Method Overview: What Is Liquid Penetrant Testing?
A Whole New World: Underwater NDT with ASNT Learn.
Method Overview: What Is Liquid Penetrant Testing?
How much do you know about liquid penetrant testing, one of the oldest methods of NDT? Test your knowledge by reviewing this excerpt from the second edition of Principles & Applications of Liquid Penetrant Testing [9 min read].
 
A Whole New World: Underwater NDT
Ready to dip your toe into underwater NDT? In this on-demand webinar, Josh de Monbrun explains the technologies used in underwater NDT, different paths to becoming an underwater inspector, and the future of the industry [55 min]. 
 
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NDT Report Writing: Back to Basics
Future of NDT in Infrastructure. Listen to the podcast Chat NDT with ASNT.
NDT Report Writing:
Back to Basics
The importance of writing an NDT report correctly is often underestimated, or maybe report writing was not covered during your training. Learn what you’re doing right—and what you might be doing wrong [8 min read].
 
Future of NDT in Infrastructure
Infrastructure is a national priority, with a growing need for NDT inspectors. Chat NDT with ASNT podcast host Debbie Segor, CAE, speaks with Nagesh Goel about the importance of NDT to address current and future infrastructure needs. Listen to the podcast [25 min].
 
Find Your Next Job Now
Read about how ASNT is advocating for women in NDT in the March issue of Materials Evaluation
Find Your Next Job Now
Are you having trouble finding the time to search through all of the available positions listed on the ASNT Career Center? Create job alerts to receive notifications for positions that match your criteria—sent straight to your inbox.
 
In Case You Missed It
Read about how ASNT is advocating for women in NDT in the March issue of Materials Evaluation [7 min read]
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Converting between Clock Positions, Degrees, and Metric or Imperial Measurements Using Standard Equations or Microsoft Excel
Converting between Clock Positions, Degrees, and Metric or Imperial Measurements Using Standard Equations or Microsoft Excel
Depending on the in-line pipe inspection tool used, the circumferential location of a call may be given in a clock position or degrees. This article explains the basis for conversion between clock, degrees, and physical measurement, and how Microsoft Excel® quantifies clock as a value [6 min read].
 
Tech Tip: Overview of Coil Configurations for Eddy Current Testing
There are three basic coil configurations used for eddy current testing of small-diameter tubing: (1) encircling coils or feed-through coils; (2) bobbin coils or inside diameter probes; and (3) probe coils or surface probes. 
Overview of Coil Configurations for Eddy Current Testing
Absolute and differential test-coil configurations for eddy current testing of small-diameter tubing.
The encircling-coil configuration is more common because of its ease of use and relatively high inspection speeds. 

The mechanical difficulties involved in the application of bobbin coils are considerable, particularly in the case of long lengths of very small diameter tubing. Despite this, their use may be warranted for inspection from the bore of heavy-wall tubing, duplex tubing, or heat-exchanger tubing. 

The probe coil (or surface probe) is not in general use for inspection of small-diameter tubing because of inherent mechanical problems and slow inspection speeds. Its high sensitivity to small discontinuities, however, is attractive for critical inspections.
 
In the case of the double encircling-coil system, the AC excitation is applied to the outer coil, and the voltage induced in the inner pickup coil is examined. The advantage of this arrangement is that the pickup coil may be sensitive to very short discontinuities. However, it does not appear to offer a great practical advantage over the single-coil system.

From the standpoint of interpretability, the probe-coil system is very attractive. In such a system, the probe mechanically scans the tube surface in a helical pattern. The advantage of the probe coil is its inherent ability to be definitive. Because it is a surface probe, it is not affected by changes in diameter. Changes in wall thickness are indicated by changes in the signal level. 

The difficulty with the probe-coil system is that even with a very carefully designed coil-holding mechanism, wobble of the tubing does occur, and the signal varies with the coil-to-tube spacing. These signals sometimes look like those obtained from cracks.
 
This Tech Tip is adapted from Fundamentals of Eddy Current Testing, second edition (2022), now available for purchase from the ASNT Store. This book provides a thorough examination of the basic theory and principles of eddy current testing and builds on the original book written by Donald J. Hagemaier.
 
QA Quips. The NDT Technician.
Hey, Cool Pic!
Are you out in the field performing NDT? Do you take cool photos? We have a new section in Materials Evaluation called Snapshots and are now accepting submissions. Submit your high-res photo to MEEditor@asnt.org for a chance to be featured in an upcoming issue!
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