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Re: number of exposure

Posted by: uli mletzko (PID_130), E-mail: mletzko@mpa.uni-stuttgart.de, on November 27, 2003 at 12:30 :

In Reply to: Re: number of exposure posted by : Uli Mletzko , E-mail: mletzko@mpa.uni-stuttgart.de, on November 27, 2003 at 12:26 :

----------- Start Original Message -----------
: : I am wondering if there is a formula that can be used for determining the number of exposures for a pipe that is going to be bombed with double wall single view techniqe. It seems to me that for smaller pipes and thick schedual pipes the geometrical unsharpness can be out of range at the end of the film when they are shot in 3 exposures. But is there a right hand rule, commen practice or some kind of formula to determine how man poses that is needed for shooting a pipe.
: : I would appriciate all the help
: : Regards
: You can find information on this subject e.g. in European Standard EN 1435, Non-destructive testing of welds - Radiographic testing of welded joints.
: There are several diagrammes in that standard, where you can directly find the numbers of exposures, depending on wall thickness, outer diameter and film-focus distance. In class A (standard quality) an increase of penetrated wall thickness from film center to film end of 10 percent is accepted, in class B (special quality) 20 percent. In addition, you have to follow a second rule, concerning the maximum allowed density difference (Delta D <= 1.5 in that standard) between film end and film center. This could force you to a larger number of expositions.
: Regards
: Uli Mletzko
: NDT group, MPA, Univerity of Stuttgart, Germany
------------ End Original Message ------------

Sorry, in the hurry I made an almost unexcusable typing error.
Of course Class A is 20 percent, and class B is 10 percent.

Regards
Uli Mletzko

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----------- Start Original Message ----------- : : : I am wondering if there is a formula that can be used for determining the number of exposures for a pipe that is going to be bombed with double wall single view techniqe. It seems to me that for smaller pipes and thick schedual pipes the geometrical unsharpness can be out of range at the end of the film when they are shot in 3 exposures. But is there a right hand rule, commen practice or some kind of formula to determine how man poses that is needed for shooting a pipe. : : : I would appriciate all the help : : : Regards : : You can find information on this subject e.g. in European Standard EN 1435, Non-destructive testing of welds - Radiographic testing of welded joints. : : There are several diagrammes in that standard, where you can directly find the numbers of exposures, depending on wall thickness, outer diameter and film-focus distance. In class A (standard quality) an increase of penetrated wall thickness from film center to film end of 10 percent is accepted, in class B (special quality) 20 percent. In addition, you have to follow a second rule, concerning the maximum allowed density difference (Delta D <= 1.5 in that standard) between film end and film center. This could force you to a larger number of expositions. : : Regards : : Uli Mletzko : : NDT group, MPA, Univerity of Stuttgart, Germany : Sorry, in the hurry I made an almost unexcusable typing error. : Of course Class A is 20 percent, and class B is 10 percent. : Regards : Uli Mletzko ------------ End Original Message ------------

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