NDT 2

[gtaw1976]

Dear all,

I am told that there is some RT technique using dual films which let us use
IR 192 source instead of CO60.
Please give me information, about the time de exposure source it's same of one film?

Kind regards.

Magalhães Julio

 

[arunmrao]

In my opinion,Ir192 is no substitute for Co60. Also increasing exposure times is not effective in detecting defects for thick section parts not covered under Ir192 source.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[weldtek]

In some cases it makes sense to use a composite set of film, but, of course it has its limitations. Review Sec V, Art 2 and in particular par T282.1 for density restrictions. It'll become clear that exposure time will have to be reduced when exposing multiple film that will be viewed compositely. Also bear in mind that Ir 192 really isn't recommended for thicknesses over 3".

 

[DiplingAndre]

I agree with arunmrao. The exposure time will be shorter because of the higher energy. But you loose sensitivity.

Multiple films is normaly used when you want to cover big difference in the wall thicknes. e.g. you have a part with 10 mm wall thickness next to 20 mm wall thickness. The you can use 2 different type of films to test the whole part with one shot.

 

[Eddycurrentguy]

Plus it's unusual for a procedure to incorporate both iridium and cobalt...seperate procedures for radiation source are required by all known codes. Not withstanding the exposure time difference, the quality of the radiation will have a marked effect on contrast, latitude, sensitivity, quality, etc. of the finished radiograph.

Iridium, Cobalt, X-Ray each has its strong and weak aspects for a given application. To quote Chief Engineer Montgomery Scott "you need to use the right tool for the right job".

 

[weldtek]

eddy,
The original poster isn't asking about combining Ir with Co. He's referring to the practice of using multiple films in a single exposure, in this case using Ir. Individually, the film density is < 2, but viewed compositely, the density will be in the range required by Code. It's also possible to do so with Co but in this case I believe the goal is to avoid using Co.

 

[Duwe6]

Not uncommon to load 3 different "speeds" of film, so that all the areas of comples castings are within the Code-required density of 2.0-4.0.

Thin areas are read using the slow film, or slow plus medium. Thick areas are read with the fast film, etc. Only applicable for RT's with widely varying thickness in the shot.