Close Proximity Radiography

[kamran]

I have some questions about Close Proximity Radiography:

Normally, I have seen firms use Se-75.

How effective it is with respect to barricading? Firms claim that a maximum of 1 to 2 metres of barricade is required.

How useful if it is for the following ranges of pipe thicknesses:

1mm to 35mm
35mm to 60 mm
60 mm and beyond

Some firms claim that Close Proximity Radiography can be done using Ir-192 as well through modifications to their Close Proximity apparatus for higher thicknesses. How effective is that?

If a project is on critical path and you have precious little time windows in which to perform radiography because of evacuation/stoppage issues and have the following sets of pipe thicknesses available for radiography...


1mm to 35mm
35mm to 60 mm
60 mm and beyond (What source? Radiography Type - Conventional or Close Proximity?)

What course of action should be adopted?

Regards,

Kamran

[ashfaqanwer]

Kamran,
What I would say is that you may use Se-75 upto 35 mm thickness but Ir-192 may only be used upto 50 mm thickness. Above 50 mm thickness you better go for Co-60.
Close proximity radiography with Se-75 and Ir-192 works but for thickness above 50 mm with Co-60, its better you compromise on construction activities to have sound results.
Barricade distances for close proximity varies with the shielding material one firm is using. Claim of 2 meters seems appropriate while using Se-75 source.

Hope this would help.