number of films in x-ray test

Type and number of film depends on the image quality required and the geometric exposure technique. These are mentioned in job specification / code of the product.

( shall be considered the source, film , exposure arrangement, material thickness ).

You can have only one film for central exposure ( with minimum 3 or 4 IQI equaly spaced around the weld ), or minimum two films for eliptical exposure of thin pipe and small diameter or minimum 3 films for double wall exposure.

As general rule the number of exposures ( films ) will be increased if the density of the film at the center is varying with more than ...% ( see code ) than at the edges and if the image sensitivity (IQI) at the edge of the interpretable area is less than required.

crstn is correct. As to the actual standards we use ASTM-1742-08 here in the USA. I believe the British Standard is BS ISO 4993-2009 for steel pipe radiography. We require 1.5 to 4.0 density in areas of interest and use a 2-2t quality level. For circular cross sections a minimum of 2 shots taken 90 degrees apart but 3 taken 60 degrees apart is better. For larger pipe diameters especially at the weld areas single wall shots are preferred and as many as necessary to insure complete circumferential coverage of the weld area and keeping the film as close to 90 degrees to the source as possible.

thaks for your answer ,

yes you correct,and crstn but you know the x-ray test price by film/$ so for example ,

i have 4 " pipe ,8mm thick, and the radiographic technic is double wall single image ,the density is 1.5 t0 4 acceptable the problem is the number of shoots

is it 3 (each 120 degree) or 4 films (each 90 degree) according to standard ???

can you please send me the ASTM-1742-08

regards

You are failing the Geometry Quiz. Once you go past 180 degrees you are only shooting the same area from a different side and that would be a terrible waste of money. You really only need 2 shots for a 4" pipe diameter roughly 5/16" thick wall (8mm). Your first shot using a 5/8"(16mm) penny, shooting for a 2.0-2.5 density at the 5/8", should give you the coverage for all but the 2 side walls. The next shot @90 degrees will take care of those two areas while the rotation puts the previous viewable area into the side wall perspective.

You might even be able to get away with one shot for the size and wall thickness that you describe by shooting for a 1" (25mm) penny at 2.0 density. This should make the side walls readable and the top and bottom areas would be less than 4.0 density at 5/8(16mm) and would therefore also be readable. You could have your lab do one each way and decide depending on the outcome.

I reviewed ASTM 1742 this AM and it specifically states (A2.2.5.2) that for a 3 1/2" diameter and above pipe use Double Wall Exposure, Single Wall Acceptance shots where "only the weld closest to the film shall be viewed for acceptance".

If you are not covered by ASTM but by another then you should use the corresponding paragraph in that Standard and depending on the service and conditions you would have to decide what to follow.

yes you right,

thanks i find in asme sec 5 ar 2that

Double-Wall Viewing .

For materials and for welds in components 31⁄2 in. (89 mm) or less in nominal outside diameter,

and for dia more than 31⁄2 inch three film minimum at 120 degree should be taken

regards

More about this, you can use only one film if you are going to use panoramic exposure technique ( i.e Pipe lines) and you can use two films (90º) for Elliptical exposure technique (i.e.Small bore socket and butt welds).

See ASME V Art.2