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454 views
00:18 Nov-14-2007

S.R.GPRABHU

Consultant, AUT specialist
FREELANCE,
India,
Joined Aug 2008
63
PHASED ARRAY EFFECTIVENESS

We paln to buy a PA equipment with 16:64 or 16:128 configurations for using in a production (GAS) platform offshore for corrosion analysis of equipments as well as thickness readings in piping. Can some one advise the PA system's effectiveness or is it worth to buy a PA system for this purpose?wHAT PROBES WE NEED TO DO CORROSION MAPPING ?Do we need TOFD scanner also?



 
06:10 Nov-14-2007

Michael Moles †2014 *1948

,
Joined

Re: PHASED ARRAY EFFECTIVENESS ----------- Start Original Message -----------
: We paln to buy a PA equipment with 16:64 or 16:128 configurations for using in a production (GAS) platform offshore for corrosion analysis of equipments as well as thickness readings in piping. Can some one advise the PA system's effectiveness or is it worth to buy a PA system for this purpose?wHAT PROBES WE NEED TO DO CORROSION MAPPING ?Do we need TOFD scanner also?
------------ End Original Message ------------

As always in phased arrays, the best probe depends on your specific application. If you are looking for large area coverage in a short time, you could use a 128 element array. The problems with this array are largely from coupling; the array is long, and maintaining coupling may be difficult. You will also need to use a wedge to minimize wear on the probe face, and for a delay line. Normally, we recommend pumping water as the couplant (an aquarium pump normally will do), since it is more difficult to get consistent coupling with smeared-on couplant. However, the ultrasonic coverage is not so good as with smaller arrays with smaller elements.

If you have a particularly rough surface, a smaller array may work better. Also, if you are looking for very small defects, e.g. pinhole corrosion, you may be better off with a smaller array, e.g. 64 elements (also with wedge/delay line) to give you a better pulse density. This assumes that the material is OK for ultrasonics, e.g. carbon steel, not some exotic material.

So, there is no simple answer, but it depends on your surface, the component for access, the speed of scanning required, and the defects. Hope this helps, and keep in touch.

As for a TOFD scanner, maybe and maybe not. It depends on your defects and component. if you want rapid area scanning, TOFD is OK, but you will probably get better and easier analysis using PA. I would try PA first.



 


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