NDTnet 1998 Aug, Vol.3 No.8

Abstract

The last ASTM Standard E94 which classified Industrial Radiography films was published in 1984. Since that time inspection contracts in the U. S. and worldwide have continued to specify "Type 1 " and "Type 2" films which no longer existed. Film manufacturers continued to classify their film using the same nomenclature.

In 1990, ASTM E07-01 started work on a revision of E94. The proposed criteria for film classification used graininess and gradient to produce an index which represented quality. In early work it was discovered that a fine grained film was possible with low contrast which produced the same index as a fine grained film with high contrast.

Table 1: WORLDWIDE FILM SYSTEM CLASSIFICATION METHODS
CEN	DRAFT ISO	ASTM
C6	T1	TYPE 3
C5	T2	TYPE 2
C4	T3	TYPE 1
C3
C2	T4	SPECIAL
C1

The draft standard was then developed so that it was possible to classify both types of film in separate groups. The first being a "Classical" film, the second a "Wide Latitude" film. The density range of the standard covered from D=2.0 to D=4.0. A radiographer would expect the contrast to be higher at D=4.0 than the contrast at D=2.0.

The combination of contrast and granularity produces a signal to noise ratio which allows for direct comparison of various films. The classes have minimum values for contrast and maximum values for graininess. The ASTM classification system employs the same parameters as the European Standard EN584-1 and ISO CD (see Table 1).

As the same basis was used for the development of these standards, their was now a method for all film manufacturers toproperly identify their films within a givensystem. This also provides an excellentmeans for the development of new film products to meet specific industry applications requirements for quality. As shown here, the method used to determine a films quality is similar in each standard, but the classification groups are not harmonized. This is unfortunate, but there is no reason that this cannot be corrected in subsequent drafts as the world moves toward a more global economy.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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