Unit 2-2 Flashcards
What is viscosity?
What has low viscosity? High?
The resistance of a fluid to flow (deform or change shape)
Liquid with low viscosity – flow easily
Water, hydraulic fluid
Liquid with high viscosity – flow slowly
Honey, oil, chocolate syrup, peanut butter
What are the ideal liquid properties for hydraulic fluid?*
Low viscosity
Stable structure in all temperatures
High flash point and fire point
High chemical stability
Define thermal characteristics
The molecular stability of a substance at various temperatures
What is flammability?
How easily a material will ignite
What is flash point?
What is fire point?
The time at which vapors become flammable and burn momentarily after coming in contact with a spark
The vapors of liquid will continue to burn for at least 5 seconds after ignition by an open flame
What is chemical stability?
What does it cause?
Ability to resist oxidation and deterioration
Oxidation causes corrosiveness
Contamination of the fluid will cause corrosion due to the added materials, i.e. water, acids
What are the three types of fluid used in aircraft?
Where can you find each?
Vegetable base fluid - vintage aircraft and automobiles
Mineral base fluids - modern aircraft
Synthetic base fluid - military and large aircraft
Describe vegetable base fluid
Mixture? Color?* Seals? Flammable?
MIL - H - 7644
Castor oil and alcohol mixture
Slightly blue or blue-green for identification
Natural rubber seals
Extremely flammable
Describe mineral base fluids
Mixture? Color?* Seals? Flammable?
MIL - H - 5606
Petroleum distillate based fluid
Red dye for identification
Synthetic rubber seals
Flammable
Describe synthetic base fluids
Mixture? Color?* Seals?* Flammable?
MIL-H-8446
Phosphate ester based fluid
Purple dye for identification
Butyl seals
Low flammability
What is the brand name for synthetic base fluid?*
Why can synthetic base fluid be a poor choice?*
Skydrol
Damaging to wiring, paint, insulation, etc
Describe rigid tubing
Solid aluminum or stainless steel tubes
Can handle high pressure
Cannot be used to connect to vibration or movable components (such as pumps or brakes)
Describe flexible hose
Specific hoses for specific fluids/pressure
Can be used to connect to vibration or movable components
Describe fittings and what pressure level each type can withstand
Aluminum for low and medium pressure
Steel for high pressure
What is an “O” ring?
What is another type of seal?
A type of seal
“O” cross section, most common type of dynamic packing
Chevron seals - (V) shaped cross section
