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Discussion Forums - The Hendrix Group
HomeHomeDiscussionsDiscussionsOil Refinery Co...Oil Refinery Co...Real time/profile radiographyReal time/profile radiography
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9/27/2006 9:00 AM
 
Dear memebers, In one of the unit the ,Transfer line between reactor to column (FCCU)got thinned out and leaked at the T-Joint weld portion due to ertosion and the same was clamped.Is there any on-line method to assess the healthiness of remaining portion of the line?. Line operating temperature is 420 Deg.C Operating pressure is : 2.5 kg/sq.cm Line size is 24" (P11 Material). Will gamma ray scanning/real time radiography can be done to check the remaining wall thiness at the eroded portion? OR Any other mehod is available?Kindly share your experience. regards,
 
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9/28/2006 9:00 AM
 
Digital Rx could be an option for your case %E2%80%9CJust 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.%E2%80%9D An advantage with this method is that we don%E2%80™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.
 
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9/29/2006 9:00 AM
 
Thanks luis.Can we check the remaining wall thickess or eroded portion by the above method?What should be distance between the source to object and object to monitor.Any temperature limitation is there for the above method?Have you taken any picture using this method? regards, krish
 
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9/29/2006 9:00 AM
 
We have done some lot of checks with digital radiography thickness measurements in lines up to 6%E2%80%9D diameter with very accurate results. For a 24%E2%80%9D diameter line it can poses some limitations because of the dimension of the digital flat panel detector. The work can be done either with gamma ray. Any way, with traditional radiography/gammagraphy you can have some good indications results about your tube wear. In this case you have to put your radiation fount on the diameter direction of the pipe, as long as possible from it to get the less divergence. You put your Rx film in a flat position normal to your fount and touching the pipe insulation. Your exposition time will be dependent on your curies isotope number and the distance of it from the Rx film. I suppose Profile radiography can only be done up to 18%E2%80%9D. Get an advice from your local NDT operator I am sure he will help you. luis
 
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9/30/2006 9:00 AM
 
You will need some form of comparator with a known measurable dimension such as a slot which allows for the calculation of the magnification caused by the exposure geometry. The Rinky Tee is commercially available. After exposure and development the wall thickness is calculated by multiplying the ratio of the pipewall and comparator images as they are measured on the radiograph by the known dimension of the slot. If using film produce as sharp an image as economically possible (low film and subject unsharpness) and make the task of taking accurate measurements from the radiograph as easy as possible. Generally this method is useful for pipes up to 12" diameter. Cheers Nigel
 
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