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Technical Discussions
Andre van Vuuren
Andre van Vuuren
00:45 Feb-09-2006
EMAT


Need some information
Can EMAT only be carried out on surface (i.e boiler tubes) that has a layer of magnetite? or can it be used on any surface?

Thanks
Andre


    
 
 Reply 
 
Catalin Mandache
Catalin Mandache
04:51 Feb-10-2006
Re: EMAT
EMAT testing requirements are: electrically conductive test piece – to generate the ultrasonic waves inside the material (Lorentz’ force principle) and continuous medium (no air gaps in the material) - for UT waves to propagate.
----------- Start Original Message -----------
:
: Need some information
: Can EMAT only be carried out on surface (i.e boiler tubes) that has a layer of magnetite? or can it be used on any surface?
: Thanks
: Andre
------------ End Original Message ------------




    
 
 Reply 
 
adams.peng
Student
China, Joined Sep 2004, 1

adams.peng

Student
China,
Joined Sep 2004
1
00:16 Feb-12-2006
Re: EMAT
EMAT__ElectroMagnetic Acoutic Transducers
an emat based system is a possible means for NDT.In this technique ,coils and magnets are located in close proximity to ,but not in contact with the surface of the material.
The material is not only magnetite(ferromagnet) but also metal,such as aluminium. there are tow types of EMATs: magnetostrictive and Lorentz. When the EMAT are used for ferromagnetic materals,the magnetostriction becomes important, especially in the low magnetic field region.
Because the EMAT is not necessary contact the surface of metal, you can use for any surface. but the more rough surface ,the lower efficiency of coupling.


    
 
 Reply 
 
Kim Hallqvist
Kim Hallqvist
01:18 Feb-12-2006
Re: EMAT
In general; In ferromagnetic materials it is a lot easier for EMATs to generate the ultra sonic pulse (usually a bulk shear wave). Though, have in mind that there is hard to predict the behaviour of EMATs because it varies a lot between different materials. You will both get a Lorenz-, magnetic- and magnetostictive effect when inducing the ultrasound. Both shear and longitudinal waves will occur. The problem with emat is that if the material not is ferro you have weak interaction with lorenz to generate, but to detect the Lorenz interaction is not critical mechanism.


Regards

Kim Hallqvist
NDE
Bodycote Materials Testing

----------- Start Original Message -----------
: EMAT testing requirements are: electrically conductive test piece – to generate the ultrasonic waves inside the material (Lorentz’ force principle) and continuous medium (no air gaps in the material) - for UT waves to propagate.
: :
: : Need some information
: : Can EMAT only be carried out on surface (i.e boiler tubes) that has a layer of magnetite? or can it be used on any surface?
: : Thanks
: : Andre
------------ End Original Message ------------




    
 
 Reply 
 
Ali Syed
Ali Syed
05:09 Feb-13-2006
Re: EMAT
Yes EMATs can be used on any surface. We have extensive experience in EMATs and successfully developed numerous applications on various ferromagnetic and other materials. These applications include weld testing, thickness measurement, corrosion detection, and cast inspection with materials including aluminum, carbon steel and stainless steel.

With efficient designs we can control the shear or longitudinal mode generation. Our pulse electromagnet EMAT technology provides rapid real time inspection capabilities.

We have extremely good control on optimizing the mode generation and its focusing in a 3-D environment. We have a system where we generate lamb waves (guided waves) to inspect the corrosion on pipelines and pipe-work and numerous systems with shear waves (SH waves or SV waves) to have a volumetric inspection of laser and other welds.

We have successfully generated bulk waves for cast defects and thickness measurement.

For more info, visit www.innerspec.com or e-mail temate@innerspec.com

Regards,

Ali Syed


----------- Start Original Message -----------
: In general; In ferromagnetic materials it is a lot easier for EMATs to generate the ultra sonic pulse (usually a bulk shear wave). Though, have in mind that there is hard to predict the behaviour of EMATs because it varies a lot between different materials. You will both get a Lorenz-, magnetic- and magnetostictive effect when inducing the ultrasound. Both shear and longitudinal waves will occur. The problem with emat is that if the material not is ferro you have weak interaction with lorenz to generate, but to detect the Lorenz interaction is not critical mechanism.
:
: Regards
: Kim Hallqvist
: NDE
: Bodycote Materials Testing
:
: : EMAT testing requirements are: electrically conductive test piece – to generate the ultrasonic waves inside the material (Lorentz’ force principle) and continuous medium (no air gaps in the material) - for UT waves to propagate.
: : :
: : : Need some information
: : : Can EMAT only be carried out on surface (i.e boiler tubes) that has a layer of magnetite? or can it be used on any surface?
: : : Thanks
: : : Andre
------------ End Original Message ------------




    
 
 Reply 
 
Dan MacLauchlan
Dan MacLauchlan
09:03 Feb-16-2006
Re: EMAT
----------- Start Original Message -----------
:
: Need some information
: Can EMAT only be carried out on surface (i.e boiler tubes) that has a layer of magnetite? or can it be used on any surface?
: Thanks
: Andre
------------ End Original Message ------------

EMAT based systems have been developed that operate on boilers tubes covered with magnetite scale and boilers tubes that are free of scale. The magnetite provides enhanced signal generation and reception for EMATs. A nice discussion of this is on Panasonics website, http://www.panametrics-ndt.com/ndt/ndt_technology/emat_transducers.html.
Magntite scale on in service boiler tubes is highly variable. The ability to get a useable signal can be hit and miss.

EMAT based thickness gages have also been developed that operates on tubes that are free of scale. One EMAT based thickness gage can be scanned along the boiler tube, recording wall thickness measurements automatically. A discussion of this thickness gage can be found at:http://www.babcock.com/pgg/tt/pdf/BR-1693.pdf
Boiler tube inspections using this thickness gage are offered by Acuren, http://www.canspec.com/rockwood/inspection.htm


    
 
 Reply 
 
Borja Lopez
Director
Innerspec Technologies, USA, Joined Jun 2002, 36

Borja Lopez

Director
Innerspec Technologies,
USA,
Joined Jun 2002
36
00:59 Feb-18-2006
Re: EMAT
EMATs can be used with magnetic and non-magnetic metals.

For thickness measurement, Innerspec Technologies has a portable unit that works on both magnetic (with or without rust) and non-magnetic materials. Innerspec also manufactures the FST-Gage in exclusivity for Babcock & Wilcox.

For more details on EMAT technology and applications visit www.innerspec.com



    
 
 Reply 
 
Joe Buckley
Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT, United Kingdom, Joined Oct 1999, 522

Joe Buckley

Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT,
United Kingdom,
Joined Oct 1999
522
09:54 Feb-18-2006
Re: EMAT
The point that 'may not be obvious unless you already know it' here is that 'standard' EMATS, i.e those that will work on conventional Flaw detectors, DO require the magnetite layer. Other types of EMAT's can work on almost any metal, but they tend to require specialised instrumentation to drive them. In particular they tend to require much higher drive current than standard tranducers.

The other point (which has been good for us) is that not all flaw detectors are equal with Boiler tube EMAT's, They do represent a fairly unusual load, and some handle it better than others.

Joe


----------- Start Original Message -----------
: EMATs can be used with magnetic and non-magnetic metals.
: For thickness measurement, Innerspec Technologies has a portable unit that works on both magnetic (with or without rust) and non-magnetic materials. Innerspec also manufactures the FST-Gage in exclusivity for Babcock & Wilcox.
: For more details on EMAT technology and applications visit www.innerspec.com
------------ End Original Message ------------




    
 
 Reply 
 
Mark potter
Mark potter
04:23 Feb-20-2006
Re: EMAT
----------- Start Original Message -----------
: The point that 'may not be obvious unless you already know it' here is that 'standard' EMATS, i.e those that will work on conventional Flaw detectors, DO require the magnetite layer. Other types of EMAT's can work on almost any metal, but they tend to require specialised instrumentation to drive them. ------------ End Original Message ------------

In some cases (for example non oxide coated boiler tubes) its not the strength of the pulse from the flaw detector that stops you from just plugging an EMAT into a flaw detector and getting a signal, but the "ringing" of the inductive coil of the EMAT. It is possible to get an "adaptor" that sits between EMAT and flaw detector to seperate out the ringing from the acoustic signal, if you dont want to shell out for a dedicated EMAT system.

Mark.




    
 
 Reply 
 
Massimo Gori
R & D,
CESI, Italy, Joined Mar 2006, 3

Massimo Gori

R & D,
CESI,
Italy,
Joined Mar 2006
3
04:48 Mar-06-2006
Re: EMAT
----------- Start Original Message -----------
:
: Need some information
: Can EMAT only be carried out on surface (i.e boiler tubes) that has a layer of magnetite? or can it be used on any surface?
: Thanks
: Andre
------------ End Original Message ------------
EMAT can be used on aged boiler tubes to measure thickness. The oxide layer improves the sensitivity, scale is tolerated.For tube thickness 3.5-5 mm accuracy of wall thickness evaluation of is in the range 0.1-0.2 mm even with outer oxide up to 0.8-1.0 mm; the oxide contribution shall be evaluated when measuring the remanent wall thickness. In the presence of oxide you will be able to detect signals with EMAT connected to standard UT units. You will need a dedicated send/receive unit to work on both aged (oxided) and clean / new tube walls.
Bye
Massimo



    
 
 Reply 
 

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