Several aerospace components were cleaned to precision cleanliness levels and
recontaminated with typical shop and cleanroom contaminants including machining
lubricants, perfluorinated lubricants, and dust. These components included
several thrust and ball bearings, several simulated mechanism gears, propellant
tubing (0.5 and 0.75 inch diameter (12.5 and 19.0 mm respectively)), and several
pieces of a simulated propellant management device with faying surfaces and a
tightly meshed screen cloth (325 by 2300 mesh per linear inch).
These components were then cleaned using the following process:
1. Preclean in aqueous cleaner (ultrasonic) maintained at 130º to 150ºF for
10 to 20 minutes.
2. Rinse using filtered deionized water for 10 minutes. Spray and ultrasonic
water rinse were used on separate sets of test samples.
3. Gaseous nitrogen purge for 1 to 2 minutes or until water is no longer
visible on surfaces.
4. Obtain NVR rinse samples for particulate, NVR, and water content
analysis.
5. Isopropyl alcohol spray for 10 to 20 minutes followed by gaseous nitrogen
purge.
6. Obtain NVR rinse sample for contamination (molecular and particulate)
analysis.
Some mechanical agitation and brushing was required for components lubricated
with the perfluorinated Braycote 601 lubricant.
A second set of propellant management screen device test samples were also
cleaned using CFC 113 for baseline comparisons. This process entailed ultrasonic
cleaning in CFC 113 (10 minutes) followed by a CFC 113 spray rinse and GN2
dry.
The above samples were visually examined for evidence of aqueous cleaner
residue, corrosion, or other visual phenomena. Surface chemical analysis was
also performed on the propellant management device screen cloth for evidence of
potentially deleterious chemicals. These chemicals could interfere with the
"wickability" of the screen and prevent propellant from entering the channel
sections of the device.
