An enclosed, environmentally
conditioned area where airborne contaminants are controlled. Clean areas
are classified by a number such as 100, 10,000, 100,000, etc., in accordance
with FED-STD-209, which describes the maximum number of particles, 0.5
microns in size and larger, permitted per cubic foot of air under certain
performance and operating requirements.
Material that degrades
the intended function of an instrument or flight hardware. Contamination
is usually separated into two types, particles and non-volatile residue
to control contamination levels.
Particle with a
length-to-width ratio exceeding 10:1 and a minimum length of 100 µm.
Small quantity of
solid or liquid material with definable shape or mass.
Maximum linear dimension
or diameter of a particle.
surface requiring a specific cleanliness level to meet minimum performance
A cleaning operation
performed to achieve a level of product cleanliness as part of good
workmanship and good housekeeping practice, for example the removal
of oils, grease, oxide films, etc. Gross cleaning does not usually require
verification beyond visual appearance as observed without optical aids
other than normal corrected vision. This step precedes precision cleaning.
Cleaning of hardware
surfaces according to approved engineering methods and procedures to
meet specific criteria.
of filtered solvent directed against a surface to dislodge and rinse
of verifying MIL-STD-1246C levels by measuring molecular contamination
in a solvent washed over a surface.
An established level
of maximum allowable particulate and/or nonvolatile residue (NVR) contamination
ranging from visibly clean to specific MIL-STD-1246 levels.
of identifying contaminants by analyzing residue on a solvent soaked
swab that was wiped over a surface.
remaining after evaporation of a volatile solvent, or determined by
special purpose analytical instruments, usually in milligrams per unit
of verifying MIL-STD-1246C particle cleanliness levels by measuring
particle contamination on a tape sample that has contacted a surface.
Item to be cleaned
is exposed to heated solvent vapors that condense on the part and wash
away contaminants. (NOTE: Halogenated solvents used to vapor degrease
plastics are often outgassed or leached out later. Therefore, plastics
vapor degreased with halogenated solvents must be baked out.)
of a visibly clean surface when viewed without optical aids (except
corrected vision) as measured by a specific method. This requirement
will be accompanied by a description of the method of verification (e.g.,
when viewed from an approximate distance using oblique white light of
an approximate intensity or under normal shop lighting, etc.).
which specifies and incident light of 50 to 75 foot-candles. The surface
to be inspected shall be observed by the unaided (except for corrected
vision) eye at a distance of 2 to 5 feet.
which specifies an incident light of 50-75 foot-candles. The surface
to be inspected shall be observed by the unaided eye (except for corrected
vision at a distance of 12-24 inches).
which specifies an incident light level of 100-125 foot-candles. The
surface to be inspected shall be observed by the unaided eye (except
for corrected vision) at a distance of 6 to 18 inches.
Plus Ultraviolet Visibly clean
(as defined above)
and inspected with the aid of an ultraviolet light (black light) of
3200 to 3800 Angstrom wavelength (320 to 380 nanometers). Note:
Any evidence of fluorescence shall be cause for recleaning. If recleaning
does not reduce the fluorescence, an investigation shall be made to
determine whether the fluorescing material is contamination or the basic
material. This level requires precision cleaning methods, but no particle
Created by Alex Rousseau last
February 2, 2004 15:30