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Technical Discussions
Simon
Director
PET Aviation Systems P Ltd, India, Joined Jul 2003, 20

Simon

Director
PET Aviation Systems P Ltd,
India,
Joined Jul 2003
20
08:46 Mar-31-2007
Corrosion Mapping by Phased Array

It is possible to do corrosion mapping by Phased Array method. Guide me if someone has already done this.

Thanks in advance

Simon


 
 Reply 
 
Godfrey Hands
Consultant,
PRI Nadcap, United Kingdom, Joined Nov 1998, 306

Godfrey Hands

Consultant,
PRI Nadcap,
United Kingdom,
Joined Nov 1998
306
08:18 Apr-01-2007
Re: Corrosion Mapping by Phased Array
----------- Start Original Message -----------
: It is possible to do corrosion mapping by Phased Array method. Guide me if someone has already done this.
: Thanks in advance
: Simon
------------ End Original Message ------------

Dear Simon,
True "Phased Array" is a technique where the sound beam is steered by separately "firing" each of the elements in an array. This is not so useful for corrosion mapping.
A "Paintbrush" array is more useful. This is a long array of elements which are either individually fired or all simultaneously, and the coverage is then in effect the same as a long narrow transducer, but with much better resolution, because each element can have its response plotted. This is more suited to corrosion mapping.

However NDT Consultants Ltd have a new instrument for corrosion mapping. This is a combination of a single element probe with a device which permits this hand-held probe to become part of a 'C' Scan system.

I presented this at NDE2006 in December. As this was in Secunderabad / Hyderabad, you may have visited and seen the system.
We are represented in India by FerroChem from Pune.

Hope this helps. Please email for a brochure if you need one.

Regards,

Godfrey Hands



 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1300

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1300
03:21 Apr-01-2007
Re: Corrosion Mapping by Phased Array
Godfrey:
It is true that corrosion mapping can be done using a "Paintbrush Probe" operated as a sequenced array. And such a probe may allow all the elements be fired simultaneously. If fired simultaneously however, you may find that resolution can be compromised.

But I beg to differ as to the concepts relating to phased array. Your statement that ""Phased Array" is a technique where the sound beam is steered by separately "firing" each of the elements in an array"...is a common misconception that seems to be held by many in NDT. The steering of the beam is commonly referred to as Sectorial scanning and is merely one of the methods that Phased arrays are used.
It is also very common to use phased arrays' "Electronic Scanning" capability. This is where a fixed focal law is stepped from one group of elements to an adjacent group. The step size can be varied to adjust the resolution. This can be used with both angled beams (like a manual raster scan of a weld without the need to physically move the probe), or it could just as easily be applied to a zero degree focal law (focused or unfocused or both) and the corrosion mapping function is accomplished.

There are now several suppliers of phased array instruments and all have descriptions of corrosion mapping as part of their capabilities.

You can also do a search of "phased array corrosion mapping" on NDT.net and find several articles describing the use of depth encoded C-scans (and associated Bscans)for composite materials and metals. As well, there is a module for the ONDT Omniscan portable phased array unit that provides for an eddy current array for corrosion mapping on aluminium.

Regards
Ed


----------- Start Original Message -----------
: : It is possible to do corrosion mapping by Phased Array method. Guide me if someone has already done this.
: : Thanks in advance
: : Simon
: Dear Simon,
: True "Phased Array" is a technique where the sound beam is steered by separately "firing" each of the elements in an array. This is not so useful for corrosion mapping.
: A "Paintbrush" array is more useful. This is a long array of elements which are either individually fired or all simultaneously, and the coverage is then in effect the same as a long narrow transducer, but with much better resolution, because each element can have its response plotted. This is more suited to corrosion mapping.
: However NDT Consultants Ltd have a new instrument for corrosion mapping. This is a combination of a single element probe with a device which permits this hand-held probe to become part of a 'C' Scan system.
: I presented this at NDE2006 in December. As this was in Secunderabad / Hyderabad, you may have visited and seen the system.
: We are represented in India by FerroChem from Pune.
: Hope this helps. Please email for a brochure if you need one.
: Regards,
: Godfrey Hands
------------ End Original Message ------------




 
 Reply 
 
Bill Blanshan
Bill Blanshan
01:38 Apr-06-2007
Re: Corrosion Mapping by Phased Array
You can do corrosion mapping with Phased Array, in fact it is the future of the technique. The advantage of using phased array is that you can control the focal point and when using a wide froot print probe such as a 5L64 or 5L128, you can scan a wide area with a detectability of a 1/16" diameter pititing (MIC). Scan coverage can be achieved in a short amount of time. The down side is that the phased array system has to be close to the scanner, unless you use an Amdata phased array system which can use a 100' adaptor cable. When scanning vessels and piping with this technique, my experience is to use a track because it is better to scan in a circumferential direction.

Best Regards,
Bill Blanshan
ASNT UT Level III
www.autsolutions.net


 
 Reply 
 

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