-17 Ch 6 Aircraft System Decontamination Flashcards
How many methods of decontamination of hydraulic systems are utilized?
5
What are the 5 methods of decontaminating aircraft hydraulic systems?
Air bleeding, recirculation cleaning, purifying, flushing, purging
What is Air bleeding?
Is a service operation in which entrapped air is allowed to escape from the closed hydraulic system.
Entrapped air in a closed hydraulic system, pressurized above ___ becomes compressed into solution. It will not be released from the fluid until pressure is removed and the air is allowed to be out-gassed. For example, actuating a reservoir bleed valve during engine start or opening the bleed valve to the atmosphere in the jenny reservoir.
50 psi
What is an effective mean for measuring the air in your system?
“Reservoir sink” check
What is the recirculation cleaning decontamination process?
A system cleaned powered from a clean external power source and cycled so as to produce a maximum interchange of fluid between the powered system and the SE used to power it. Decontamination is accomplished by circulating the contaminated fluid through the hydraulic filters in the aircraft system and in portable hydraulic test stands.
What’s a key factor in recirculation cleaning?
is the utilization of high-efficiency 3-micron (absolute) filter elements.
What is recirculation cleaning effective for?
Is effective in removing hard particulate matter and air contamination from hydraulic fluid that is otherwise serviceable, it must be recognized that the filters are
not capable of removing water, other foreign fluids, or dissolved solids.
What is the Purifying?
Is the process of removing particulate, air, water, and volatile contaminants from the hydraulic fluid without altering the physical or chemical properties.
What does the Purifying process look like?
Contaminated fluid going to the purifier tower is first filtered by a 25-micron (absolute) filter. The vacuum applied to the
tower removes air, water, and chlorinated solvents from the contaminated fluid. As the fluid comes out of the tower, it is filtered through a 3-micron (absolute)
filter to remove solid particles. This cycle is repeated until a desired level of cleanliness is attained.
What is the flushing process?
Is a method in which contaminated system fluid is removed to the maximum extent practicable and then discarded. It is a draining process that is accomplished by powering the aircraft system with a
portable hydraulic test stand and allowing the contaminated return line fluid from the aircraft to flow overboard into a suitable receptacle for disposal. Filtered fluid
from the portable hydraulic test stand is used to displace contaminated fluid in the system and to replenish it with clean serviceable fluid.
What is the purging process?
Is a process where the aircraft hydraulic system is drained to the maximum extent practicable and the removed fluid discarded. A suitable cleaning agent is
then introduced into the hydraulic system and circulated as effectively as possible to dislodge or dissolve the contaminating substances. The cleaning operation is followed by complete removal of
the cleaning agent and its replacement with new hydraulic fluid.
When should only purging be done?
Purging of aircraft hydraulic systems shall be performed only upon recommendation from, and under the direct supervision of the Fleet Support Team (FST) and to select the required cleaning agents, provide detailed cleaning procedures, and perform test upon completion of purging to ensure satisfactory removal of all cleaning agents.
Purging operations shall be accomplished at?
Fleet Readiness Center (FRC).
*Organizational and Intermediate Maintenance Activities (OMA and IMA) are not authorized to perform system purging.
How is a method of decontamination be
selected?
Will be according to the type of contamination observed. Recirculation cleaning is usually the most effective of the available decontamination methods.
