Inspectioneering
Inspectioneering Journal

In-Service Inspections Using EMAT and MRUT

By Borja Lopez at Innerspec Technologies, Inc.. This article appears in the July/August 2015 issue of Inspectioneering Journal
This article is part 3 of a 3-part series.
Part 1 | Part 2 | Part 3

EMAT Overview

Readers were previously introduced to some of the practical advantages of EMAT Ultrasonic Testing (UT) in the March/April 2013 and July/August 2013 issues of Inspectioneering Journal. These advantages include dry inspection, an imperviousness to surface conditions, and unique wave modes such as shear waves with horizontal polarization (SH waves). In this article, I will cover the practical advantages of EMAT for in-service applications using Medium Range Ultrasonic Testing (MRUT).

As a review, EMAT, or Electro Magnetic Acoustic Transducer, is a UT technique that generates the sound in the component inspected instead of the transducer. As illustrated in Figure 1, EMAT generates ultrasonic waves into a test object using electromagnetic induction with two interacting magnetic fields. A relatively high frequency (RF) field generated by electrical coils interacts with a low frequency, or static, field generated by magnets to produce a Lorentz force in a manner similar to an electric motor. This disturbance is transferred to the lattice of the material, producing an elastic wave. In a reciprocal process, the interaction of elastic waves in the presence of a magnetic field induces currents in the receiving EMAT coil circuit.

Because the sound is generated in the part inspected instead of the transducer a liquid couplant is not required.  EMAT is a completely non-contact technique that has significant advantages for in-service applications over more conventional piezoelectric inspection techniques. More specifically, in this article, we will discuss the applications and techniques deployed when using guided waves with a MRUT system.

This content is available to registered users and subscribers

Register today to unlock this article for free.

Create your free account and get access to:

  • Unlock one premium article of your choosing per month
  • Exclusive online content, videos, and downloads
  • Insightful and actionable webinars
GET STARTED
Interested in unlimited access? VIEW OUR SUBSCRIPTION OPTIONS

Current subscribers and registered users can log in now.


Comments and Discussion

Posted by Dana Cole on October 19, 2015
I wish that this article explained or included... Log in or register to read the rest of this comment.

Posted by Cord Doss on November 2, 2015
Up to 200°C, the temperature has no noticeable... Log in or register to read the rest of this comment.

Add a Comment

Please log in or register to participate in comments and discussions.


Inspectioneering Journal

Explore over 20 years of articles written by our team of subject matter experts.

Company Directory

Find relevant products, services, and technologies.

Job Postings

Discover job opportunities that match your skillset.

Case Studies

Learn from the experience of others in the industry.

Event Calendar

Find upcoming conferences, training sessions, online events, and more.

Industry News

Stay up-to-date with the latest inspection and asset integrity management news.

Blog

Read short articles and insights authored by industry experts.

Acronyms

Commonly used asset integrity management and inspection acronyms.

Asset Intelligence Reports

Download brief primers on various asset integrity management topics.

Videos

Watch educational and informative videos directly related to your profession.

Expert Interviews

Inspectioneering's archive of interviews with industry subject matter experts.