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Digitalizzazione film radiografici

DigFilm

STC srl   ha implementato un servizio di digitalizzazione film radiografici in conformità alla norma  UNI EN 14096-2  classe  DS – DB – DA

Il servizio si basa sull’utilizzo di uno speciale  scanner per radiografie in applicazioni NDT, in grado di fornire prestazioni di digitalizzazione di fascia alta.

Tutti i formati di pellicola standard possono essere digitalizzati, fino ad una larghezza di 35 cm (14 in.), senza limitazione di lunghezza in qualsiasi risoluzione compresa tra 50 micron e 500 micron. Il  digitalizzatore è in grado di gestire l’intera gamma di densità (D = 0 fino a 4,70 D) in un campo di lavoro con la sensibilità al contrasto richiesto,  in modo da soddisfare i requisiti della classe DS secondo EN 14096 -2. ( in allegato tabelle )

STC Ltd. has implemented a service of digitization of NDT radiographic films in compliance with UNI EN 14096-2 class  DS – DB – DA

The service is based on the use of a special scanner for radiographs NDT applications, capable of providing high-end digitization.

All’ standard film formats can be digitized, up to a width of 35 cm (14 in.), Without limitation of length in any resolution between 50 microns and 500 microns. The digitizer is able to handle the full range of density (D = 0 up to 4.70 D) in a working range with contrast sensitivity required, so as to meet the requirements of class DS according to EN 14096 – 2 .

Digitization quality classes

 

All radiographic  film digitization systems are subdivided into 3 quality classes DS, DB and DA

 

DS –  the enhanced  technique  which performs  the digitization  with an insignificant  reduction of signal-to-noise  ratio and spatial resolution.

Application field: digital archiving of films (digital storage).

 

DB – the enhanced technique, which permits some reduction of image quality.

Application field: digital analysis of films, original radiographic  films have to be archived.

 

DA-  the basic technique, which permits some reduction of image quality and further reduced spatial resolution.

Application field: digitalis analysis of films, original radiographic  films have to be archived.

 

Each radiographic  film digitization system for NDT applications shall be identified with all working ranges of optical densities. it shall be classified by the quality class corresponding  to Table 1 and the maximum  MTF 20% value, corresponding to EN 14096-1, which can be performed by this system.

EXAMPLE        A digitization system of class DS 4,2 (scanner class DS (see Table 1), maximum MTF 20 % = 4,2 lp/mm (see Table 2)) can be applied for archiving of radiographs taken with X-rays above 200  KeV or y-rays and can be applied for all class DB and DA digitization tasks.

 

EN 14096 -2

 

Minimum requirements for film digitization quality classes

 

  • Density range and working ranges of the film digitization system

 

 

Table 1  defines  the  minimum  density  range  of the  radiographic  digitization  system.  In  this  density  range  the digitizer shall provide  a density contrast  sensitivity DCS with DCS < 0,02  Depending  on the construction  of the digitiser, this density range can be split into several working ranges.

 

The minimum digital resolution is given for devices converting the digital value proportional  to the optical density. lf

the digital value is converted proportional to the light intensity, the digital resolution has to be increased at least by 2 additional bits

 

Table 1 -Minimum density range of the radiographic digitization system with a minimum density contrast sensitivity

 

Parameter Class DS Class DB Class DA
Density rangea  DR 0,5 to 4,5 0,5 to 4,0 0,5 to 3,5
Digital resolution in bit >12 >10 >10
Density contrast sensitivity

DCS within DR

> 0,02 > 0,02 > 0,02
a      This density range may be splitted into separated working ranges.

 

  • Minimum spatial resolution of film digitization systems

 

 

Due  to  the  energy  dependence   of  the  inherent  unsharpness   of  industrial  X-ray  film  systems   the  following parameters (see Table 2) shall be observed:

 

Table 2 – Minimum spatial resolution of film digitization systems

 

 

Energy Class DS Class DB Class DA
keV Pixel size

µm

MTF 20%

lp/mm

Pixel size

µm

MTF 20%

lp/mm

Pixel size

µm

MTF 20%

lp/mm

< 100 15 16,7 50 5 70 3,6
>100 to 200 30 8,3 70 3,6 85 3
>200 to 450

Se 75, Yb-169

60 4,2 85 3 100 2,5
Ir 192 100 2,5 125 2 150 1,7
Co 60, >1 MeV 200 1,25 250 1 250 1

 

NOTE 1    For the normal! check corresponding to EN 14096-1, the MTF 20 % value can be determined by the converging spatial resolution targets.

 

NOTE 2      Due  to possible  aliasing,  the converging spatial resolution targets can  give  less  accurate values  than MTF measurements.

 

NOTE 3      For energies lower than 70 keV the spatial resolution of the radiographic  film can be better than the scanner resolution required by the class DS 16,7. In this case the spatial resolution of  the scanner  should be adapted to the film resolution, or the original  radiographic film should be archived.

 

 

 

 

 

  • Digitization class depending on the radiographic testing class

 

 

The   standards ISO 5579,  EN 444,  EN 1435   or  EN

Radiographs taken according to these standards shall be digitized corresponding to Table  3.

 

Table 3 -Minimum digitization class depending on the radiographic testing classes A and B, if radiographs are taken on the basis of ISO 5579,EN 444, EN 1435 or EN 12681

 

wall thickness [mm]

steel

 

Class DS

 

Class DB

 

Class DA

< 5 B A
> 5 B B A

 

 

NOTE           For the detection of cracks and fine imperfections Class DB or better should be used.

 

After digitization process all required image  quality  indicators shall be visible  in the digital image as on the original radiographic film.

 

CENTRO D'ESAME e FORMAZIONE CnD



 

STC Servizi e Tecnologie dei Controlli Srl
SEDE LEGALE ED OPERATIVA

Via Golfarelli, 90/8 - 47122 Forlì (Italy)
Tel. (39) 0543 774086 - Fax (39) 0543 724182
www.controlli.it - e-mail:info@controlli.it
Capitale Sociale Euro 15.000,00 i.v.
Iscrizione CCIAA di Forlì-Cesena/P.I./C.F. 02376560401
N. REA 259927

 

STC LAB SERVICE Srl

Via Golfarelli, 90 - 47122 Forlì (Italy)
Tel. (39) 0543 774086 - Fax (39) 0543 724182
Capitale Sociale Euro 10.000,00 i.v.
Iscrizione CCIAA di Forlì-Cesena/P.I./C.F. 02362330397
N. REA FO-403523
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