EMAT–TECHNOLOGY AND EQUIPMENT FOR AUTOMATIC
NONCONTACT ULTRASONIC INSPECTION OF ROLLED METAL AND
A.V. Kirikov, Technical Manager of the JSC “Nordinkraft Company” (Cherepovets, 162611, Vologda reg.,
Russia; Chief Designer of Automated Nondestructive Inspection Systems, 3 rd
class expert in acoustic inspection methods.
Corresponding Author Contact:
Email: email@example.com, Internet: www.nordinkraft.com/Paper presented at the 8th ECNDT, Barcelona, June 2002
Design features and unique performance attributes of installations for automatic noncontact
ultrasonic testing of rolled metal and sections, tube strip and pipes are described.
The engineers and experts of the “Nordinkraft” Company” have designed and put into broad
industrial operation the complex of automatic noncontact ultrasonic testing facilities intended
for inspection of rolled metal and sections, tube strip and pipes of different diameter for
different purposes. The equipment is represented by the families of the certfied systems
“SEVER”, “VOLNA” and “MAJACK”.
The technology behind all of the above mentioned systems is the Electro Magnetic Acoustic
Transducers (EMAT) application.
EMATs are devices designed for noncontact excitation and receipt of ultrasonic waves. They
function in non-liquid environments and have huge advantages over conventional piezoelectric
They are also appropriate for severe climatic conditions and guarantee the reliable high-speed
inspection of metallurgical products that can have both very high and very low (as much as –50 ° C
and even lower) temperatures.
Tested products do not rust because they are not moistened. EMATs allow to excite and selectively
receive types of ultrasonic waves unobtainable when using a PET.
Untill recently, installations using EMATs had relatively low sensitivity. This prevented them from
The situation has fundamentally changed with the development of modern methods and facilities of
received signal processing. The “Nordinkraft” Company” installations have excellent sensitivity that,
in some cases, cannot be obtained when using conventional systems.
With a variety of inspection tasks and test objects, all the Company’s diagnostic equipment is based
on the unified physical, ideological and metrological foundation.
Let as take as an example a description of one of the latest works of the Company - installations
“Sever –6-08” for automatic noncontact ultrasonic testing of flat/sheet products.
The “Sever 6-08” unit is a new, certified generation series of equipment. It solves a broad range of
technological and flaw detection problems and fulfills the highest contemporary standards and
The new “Sever 6-08” unit is a multichannel system for the non-contact, completely automatic and
high-performance ultrasonic testing of sheet and strip metal.
Up to 600 (!) independent electromagnetic-acoustic transducers (EMAT) with surface adaptation
function activates the sending and receiving of ultrasonic waves in a direction strictly
perpendicular to the test object surface and guarantees it’s dense scanning..The construction of the new “Sever” is designed so that the customer determines the structure of
the diagnostic complex. From “cubes”—systems and parts, and “bricks”—the functions, the
customer is equipped with the means (along with technical support from the specialists of the
Nordinkraft Company) to design the necessary and adequate configuration for the acquired system,
optimal from both the technical and economic perspectives.
This capacity for configuration, as well as the price and size/volume of our equipment, are
determined by the following base characteristics:
- the required density of the testing;
- number of channels;
- width of the test object (TO);
- the set of applied methods;
- the set of additional features;
- the range of possible temperatures of TO.
The range of active frequencies of the flaw detection apparatus is significantly expanded (up to 10
MHz). It determined the high sensitiveness and resolution of the unit. The minimum thickness of
the test object now stands at 3 millimeters when using echo methods. Moreover, signals are
received separately from rolled metal with a thickness of 1.4 millimeters, which is practically
unattainable when using combined piezoelectric transducers. The system of automatic, dynamic
strobe tuning, individual for every channel (transducer), allows for the complete compensation of
the varying thickness of rolled metal and reveals stratification located at a depth of only 0.2 mm
from any of its surfaces.
For the first time, all modern algorithms for the processing of received signals are being applied.
This, together with the traditional coherency processing applied in all Nordinkraft Company
systems, have permitted us to completely remove all specific requirements for “noisy” power
supply voltages. The interference protection of electrical equipment and automatic systems
significantly increases similar indices of the ultrasonic control complexes we are familiar with.
The measuring module of the Sever 6-08 device can contain one, two or three EMAT lines from
each side of the test object for, respectively:
linear scanning with a step of 27 or 35 mm
100% (solid) scanning
solid scanning with a 50% overlap
A system of selvage zones testing, included in the standard outfitting of the unit, realizes the
automatic tracking of the edges of the sheets or strips and solid scanning at a width of up to 200
For the first time in the history of flaw detection, the “SEVER -6-08-2” allows for the
simultaneous control of all six certified and known methods:
- echo method;
- echo-through method;
- shade method;
- mirror-shade method;
- repeated-shade method;
- repeated mirror-shade method.
The unit demonstrates an extremely high sensitivity. Echo and echo-through methods reveal
defects that are equivalent to a flat-bottomed drilling with a diameter of 1.0 to 1.5 mm..This would seem to represent one of the best levels of sensitivity achieved in the line of automatic
control today. It significantly surpasses the requirements of contemporary standards.
The given sensitivity is automatically maintained at an equal level in all channels.
Separately - for selvage zones and for base metal.
“Sever 6-08-2” does not “notice” slag, oil and other pollutants, does not damage the external
appearance of the product (it does not rust since no water is used).
Permissible range of temperatures of the rolled metal from –50 C° to 300 C° for the standard
version and up to +650 C° for the special version.
The moderate width of the measuring module—about two meters—allows easy adaptation of the
system to the on-line process. The mounting of the system in existing rollways is not connected
with major reconstruction and does not require major capital investment. Usually not more than a
week is required for outfitting the line.
In addition to basic, traditional problems the system permits the user to:
- measure the thickness of the material in an automatic mode across its entire width with a
precision of 0.05 mm;
- discover in the course of the testing and to display on a flaw diagram the zone where the test
object exceeds the acceptable boundaries;
- measure the thickness and geometry of the rolled metal;
- determine in the current mechanical characteristics of the metal (according to their correlation
with anisotropy of the speed of orthogonal-polarized transverse waves;
- determine the type of revealed defects (to distinguish the surface defects from the inner
- determine unfavorably-oriented defects (vertical cracks for example);
- to perform thorough self-diagnosis;
- to supervise the testing process;
- to transfer to the factory’s net all information about the process and the results of the testing
with indication of the mass, geometrical, mechanical and other characteristics of the test
material, as well as information about the idling and breakdowns of technical equipment, even
that which is not part of the unit;
- to transfer all the above to the remote user via the Internet.
All processes of adjustment and calibration are completely automatic. They are carried out by the
Calculating control complex: the heart of the unit. The interface, based entirely on experience in
traditions of the previous series, has become even more “friendly.” The management of this whole
complex organism becomes a possible and pleasant activity within an hour of the user’s first
acquaintance with it.
The carefully thought-out system of interactive instruction has allowed the user’s initial
qualification requirements to be significantly lowered.
It is obvious that the “Sever 6-08” is the embodiment of the most modern achievements and
Since 1990 the “Nordinkraft” Company” put into industrial operation at Metallurgical works over
30 systems of automatic noncontact ultrasonic testing including ones with EMATs.
In particular, at Volzhsky Pipe Plant 8 installations for automatic ultrasonic testing of rolled metal
and pipes are put into industrial operation for today. 6 of them are equiped with EMATs.
Installation “Volga” for automatic ultrasonic testing of welding seams allows both EMA-transducers
and conventional, piezoelectric, transducers use. Comparative analysis found out.significant advantage of EMATs, including on sensitivity to real defects, reliability, testing validity
and reproducibility of it’s results.
Installations’ operation during 1999 – 2000 years was inspected by specialists of International
Caspian Pipe Consortium within the period of performing it’s order.
Two automatic installations for automatic ultrasonic testing of rolled metal with the use of EMATs
have been sucessfully operated for 6 years at JSC “Severstal”.
Two analogues units are put into industrial operation at JSC "Magnitogorsky Metallurgical
In Magnitogorsk as well as in Donetsk and Stary Oskol units for pipe shells testing with the use of
EMATs are efficiently operated.
Reports on scientific activity and practice of the “Nordinkraft” Company” in the field of designing
and putting into industrial operation of US tesing installations with EMATs have been repeatedly
published in particularized editions, reported on all-Russian and international conferences on NDT.
We are sure that for EMAT- technologuies is the future of automatic ultrasinoc defectoscopy.