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Sequence control chart for aircraft system decontamination

Aviation Structural Mechanic (H&S) 3&2 - How airplanes are built and how to maintain them
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extreme cases, to purge it. Refer to table 4-3. The table contains information to help you select an appropriate decontamination method. The table refers to chemical analysis and particle counting, as well as to the normally performed patch testing and visual tests. You may request chemical analysis and actual particle counts of fluid samples from the NADEP materials engineering laboratories. You may use these test results to select a decontamination method. CONTAMINATION CONTROL SEQUENCE System decontamination is one operation of a contamination control sequence that includes hydraulic fluid sampling and analysis. Decon- tamination is performed when the results of sampling and analysis indicate an unacceptable contamination level. Then, additional testing determines when an acceptable level is reached. There are many operations required during the contamination control sequence, and these operations interact during the sequence. Figure 4-7 is a basic contamination control sequence chart for aircraft system decontamination. It is a guide for decon- taminating all naval aircraft and portable hydraulic test stands. The procedures outlined in the chart reflect basic requirements of periodic maintenance, Table 4-3.—Aircraft Decontamination Requirements TEST METHOD ABNORMAL INDICATION **DECONTAMINATION METHOD REQUIRED Visual Inspection Free Water—standing or droplets Flush Dissolved Water—pinkish fluid, not clear Flush Gelatinous Substances Flush Visible Gross Particulate Matter Flush Oxidation—dark fluid, not clear Flush Patch Test Excessive Particulate-exceeds Class 5 SE Recirculation Water Droplets or Stains Flush Fibers SE Recirculation Gross Particulate Matter—extreme Flush contamination from component failure or external sources Particle Count Excessive Particulate Matter—exceeds Class 5 SE Recirculation Chemical Analysis (Depot) Viscosity—out of limit (*) centistokes @ 100ºF Flush Flash Point—less than 180°F Flush Water—in excess of(*) ppm Flush Neutralization—in excess of 0.8 mg KOH/g Flush (acid) Chlorinated Solvents—exceeds (*) ppm Flush (*) Acceptable limits to be determined by the cognizant engineering activity. ** Fluid purifiers may be used instead of flushing when purifying equipment is available. 4-18







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