Engine Titanium Consortium - Center for Nondestructive Evaluation ...

Assessment of Cleanliness on Inspectability: A major concern for the inspector is the cleanliness of
the part to be inspected and the impact that surface condition will have on detectability, with the
question often being asked, “How clean is clean?” Some effort has been undertaken to provide
guidance in this area in the most recent version of SAS 2647. An engineering study will be
performed to assess the utility of these metrics through on-site evaluation at airline shops using
field run hardware. LCF blocks will be used to establish a baseline and for comparison across test
sites. A matrix will be generated that establishes the effectiveness of various cleaning methods in
removing general classes of typical contaminants. It is expected that various operational
conditions, types of cleaner equipment/systems, cleaner type, cleaner concentration, process
parameters, and alloy types will be considered. Appropriate data will be gathered on the field
systems used in the study such as chemical concentration of the cleaning solutions, temperature,
etc to allow comparison between systems and to approved process parameters. Guidance on the
effect of cleanliness on penetrant inspectability will be provided in the form of a cleanliness matrix
that summarizes cleaning process effectivity for various contaminants.
Assessment of the Effect of Cleaning Method on Inspectability: Given a definition of the required
cleanliness from the effort above, an engineering study to arrive at the effect of cleaning methods
on detectability will be performed using LCF blocks. Potential cleaning methods to be considered
include
♦ aqueous degreasers
♦ ultrasonic cleaners
♦ plastic media blast
♦ water jet blast
♦ solvent cleaners
♦ etching processes (local only)
♦ chemical cleaners for both Ti and Ni
♦ vapor degreasers
Local etching of FOD and other local anomalies to remove smeared metal and improve crack
detectability is a common practice. An evaluation to define optimal local etching practices will be
performed. Parameters within the global cleaning process which may need to be considered
consist of degree of agitation, time spent in tanks, degree of concentration and post-clean,
particulate size and content, pressure, etc. The effect of cleaning methods on background, wetting
characteristics, residual stress, and crack detectability will be assessed. A matrix will be generated
which establishes the detectability as a function of the selected cleaning processes and provided as
a final product of the study.
Assessment of the Drying Method on Inspectability: Once the part is appropriately cleaned, it is
essential that all fluids be removed from any rejectable defects such that penetrant solution can
easily enter the flaw. Definition and adherence to appropriate drying times and temperatures is
critical to the overall effectiveness of the FPI process. An engineering study will be performed to
establish the optimal drying process parameters. Potential drying methods to be considered
Quarterly Report – January 1, 2002 –March 31, 2002
print date/time: 6/6/2002 - 8:39 AM – Page 79