FIFTH CANADIAN CONFERENCE ON NONDESTRUCTIVE ... - IAEA

HOW TO TEST (Continued)
- 167 -
Set aside a box of film, sufficient in quantity to last a month or two, in
a good environment such as 20 C (70 F). Label the box for test purposes
only and record the film type, brand, class, emulsion number and expiration
date. Choose a film that is the same as the film most often used. If both
Class I and II films are regularly used choose a higher speed Class I film.
When the first batch of film is about to be used up choose another batch and
check for similarity by proocessing both emulsions together.
Choose an easy, fast exposure technique. Expose a stepped wedge and, if
possible and practical, a defective part that has known flaws. Label this
part "for test purposes only". Attach appropriate penetrameters to the wedge
and part. The film holder or cassette, screens, FFD, etc. must be constant.
The essence of sensitcmetrie quality control is to give a controlled piece
of film a controlled exposure and then process it to see if the processing
is in control. Hold everything reasonably constant in order to monitor one
of the variables.
To help you get started, and everyone must have a sensitometric quality control
program, the Du Pont Company offers a Sensitometric Quality Control Kit consisting
of 50 pre-exposed NDT 55 Class I film, clearing time strips, hypo retention
solution and reference strips for sensitometry, and archival quality. There is
an instruction booklet and a copy of the Du Pont Radiographer's Reference with
technique and processing specifications. Du Pont produces this kit as an
industry service to help get everyone on QC, it is a no-profit item, and it is
intended only to get you started. You should be able to start-up your own
program within the first month.
CONCLUSION
Sensitometric quality control measures the sum total effect of processing
chemicals, time, temperature on a controlled exposure to a controlled piece
of filai. An image is measured to see if processing is in control. This is
the best method to effect quality control on Quality Control. Radiography
is a quality control tool of production, but, is it, itself, under control?
Has the quality been defined and is it consistent? Quality Control is an
economic as well as a technical tool. It is absolutely necessary today...
not twenty years frcm now.
REFERENCE READING
"Radiographic Latent Image Processing" by William E. J. McKinney, Section
Seven, ANSI Nondustructive Testing Handbook, Columbus, Ohio, 1982.
WEJM/daw