Digital Radiography 4

[weldtek]

One of the NDE companies we use is planning on making Digital RT available to their customers in the near future. From his comments it seems there are some benefits to the process, but, like any new process I'm sure it will take some time for it to gain acceptance. If anyone has experience with the process I'd be interested in hearing your comments.

 

[BillPSU]

I've experienced at the dentist's office. A flat sensor was placed in my mouth and then shot with x-ray. The image immediately appeared on a computer screen. There was no waiting, no film, no developer time, no other equipment. The image was in a digital format.

NDE could use the same technology but the power of the x-ray would have to increase and the size of the sensor would also have to increase. Sensor size would be my biggest concern along with the initial investment cost.

 

[metengr]

I believe digital RT is currently being reviewed under a proposed ASME Boiler and Pressure Vessel Code case. One major drawback that I have heard was the ability of being able to alter the digitized file, which the code committee folks felt could mask or alter the appearance of defects.

We have used Digital RT in the field for non-code applications - it worked well for us.

 

[ElderX]

I work in aerospace manf. and we use digital RT. There are a number of detector types available, ASe and ASi CR as well as CMOS. The choice is based on the application,operating parameters and required image parameters. While digital RT is faster and has many advantages over film. There are alos some trade offs. Film currently provides better spatial resolution but the digital methods provide more lattitude and the albility to vary the greyscale helps when there is a wide range of density(matl. thickness).

One definite advantage is in the use of real time imaging and the ability to vary the exposure geometry on the fly something you can't do with film.

I would recommend you study the pros and cons carefully and get the manufacturer of the equipment to perform RT of your inteneded products(s) using the same type of equipment you intend to purchase prior to making your decision. We are not talking about a minor investment for a system.

 

[api510]

Our company just purchased a digital x-ray system. Currently it is being registered with the state. When I get it up and running, I will post-up with results.

 

[JR97]

The ASME Code has accepted digital RT - reference Code Case 2476.

There are two levels of 'digital RT'. The first level is the use of phosphor plates which are exposed just like conventional RT film (much quicker though). Plates are painted with laser which releases light in proportion to radiation exposure. Digital readers sense the light generating the digital file. Plates are reset and can be re-used. The second level is a digitizing plate which directly 'reads' the radiation received and generates a real-time image. Drawback is the digitizing plates are rigid and cannot be bent to fit pipes, etc.

Cost of the phosphor plate system is not that bad, about $25K-50K. Cost of digitizer plate is about $125K+.

My company looked at phosphor plates for a project we didn't get so I can't provide any use feedback.

 

[lalaith]

I have been looking into digital radiography for my company as well. An associate at another company had a situation arise where a post stress film radiograph showed an indication that was not visible in the pre-stress digital radigraph. The NDE company has told this associate that cracks cannot be detected in chrome welds with digital radiography. The NDE company has not explained why digital radiography will pick up cracks in all material except chrome. I have talked to about 4 other NDE companies that do digital radiography and all of them have said that portable digital RT using phospor plates will not detect cracks. Does anyone have any additional information about digital radiography for weld integrity in a field situation.

 

[metengr]

The term digital RT can be misused or incorrectly labeled. The radiography that uses phosphor plates is called CR or computed radiography. In comparison, real time radiography is called digital radiography. EPRI is working on making digital RT field portable.

 

[rorschach]

BillPSU, in the digital radiography systems I've seen, the x-ray power is greatly reduced due to the much higher sensitivity of the sensor compared with conventional film, by about an order of magnitude. That is one of the reasons why dentists and doctors are moving to that so heavily (that and the fact that the conventional film suppliers are getting out of the biz, the two market forces tend to reinforce each other.)

 

[0707]

Digital Rx is being used from long time ago for medical purposes. Digital Rx on industry was introduced about 10 years ago.

“Just as with any conventional X-ray, the inspected item is placed between the X-ray source and the imager, which in this case is an a-Si digital flat panel detector. The X-ray source is fired, energizing the digital flat panel detector. Once the image is captured and read out, it is immediately displayed on the computer monitor, and ready for a wide range of image enhancements, extreme zooms (up to 800 percent) and Window levelling, to make full use of the wide dynamic range presented by this technology.”

On small drain lines and insulated pipes in HF Alky unit we start a digital inspecting programme with good results the main advantage is that we obtain a thickness profile image of pipe section which is good to decide the need for pipe replacement. An advantage with this method is that we don’t need to uninsulate lines the other advantage is that the a-Si flat panel detector imager can withstand several shoots and the obtained image can be stored and treated through a computer software programme.

For more information go to

http://www.vidisco.com/faq/ndt.php

Luis