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Technical Discussions
gops
gops
09:08 Dec-09-2009
Digital RT

If we use digital radiography in place of conventional RT will there be any improvement in POD to detect tight , underbead & transverse cracks?

    
 
 
Abbas Bombaywala
NDT Inspector
Free Lance, India, Joined Jul 2007, 91

Abbas Bombaywala

NDT Inspector
Free Lance,
India,
Joined Jul 2007
91
11:40 Dec-09-2009
Re: Digital RT
In Reply to gops at 09:08 Dec-09-2009 (Opening).

Well Gops

In Digital Radiography there are two types

No. 1 Computed Radiography

Computed radiography is a transitional technology between film and direct digital radiography. A reusable, flexible, photo stimulable phosphor (PSP) plate is loaded into a cassette and is exposed in a manner similar to traditional film radiography. The cassette is then placed in a laser reader where it is scanned and translated into a digital image. Depending on the resolution required and image size, the process of digitizing may take from one to five minutes. Once digitally captured, the image may be stored on a computer or other electronic media. Archiving is made easier and the images can be electronically distributed to others for viewing.

This Digital Radiography is used for only the purpose to eliminate use of Films, Chemical & Time of Developing, and it also has advantage of life time storage of data.
So if we talk about this digitzing process I dont think there would be any improvement in POD for any particular defect.

2. Direct Digital Radiography

A direct digital system is different from computed radiography in that it digitizes the photon radiation that passes through an object directly into an image that can be displayed on a computer monitor. Amorphous silicon, charge coupled device (CCD), and complementary metal oxide semiconductor (CMOS) are the three principle technologies used in direct digital imaging. Direct digital system images are available for viewing and analysis in seconds as compared to the minutes required in computed radiography systems. The increased processing speed is a result of the unique construction of the pixels in a direct digital system; an arrangement that also allows an image resolution that is superior to computed radiography and most film applications

In this Direct Digital Radiography yes there is a increase of POD compare to Conventional RT.

I Hope this will help u.

Regards.
Abbas Bombaywala

    
 
 
gops
gops
12:28 Dec-09-2009
Re: Digital RT
In Reply to Abbas Bombaywala at 11:40 Dec-09-2009 .

Thanks for the feedback.Which one is suitable for large diameter (42")off-shore pipeline erected through barge and whether full panoramic shot is possible with digital radiogrpahy fim holder.

    
 
 
Abbas Bombaywala
NDT Inspector
Free Lance, India, Joined Jul 2007, 91

Abbas Bombaywala

NDT Inspector
Free Lance,
India,
Joined Jul 2007
91
13:20 Dec-09-2009
Re: Digital RT
In Reply to gops at 12:28 Dec-09-2009 .

Dear Gops

I can't say which one is suitable, but obviously i would go for the technique which has better POD and gives me more Data for ECA.
For More Information u might refer this link http://www.asnt.org/publications/tnt/tnt5-2/tnt5-2fyi.htm.

For Computed Radiography u need the no of cassetes (PSP Plates) to cover your Dia of 42" for a panaromic shots. thats all u need to perform a panaromic shot.

Regards.

    
 
 
Sashidhar
Sashidhar
18:33 Dec-10-2009
Re: Digital RT
In Reply to gops at 12:28 Dec-09-2009 .

I think Computed radiography can be done on this one. Digital radiography is done in a controlled environment mostly..and for this panoramic shot it may not suit.
Computed radiography can be done easily as long as we have that number of Phosphor plates available.

    
 
 

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