Systems 3 Hydraulics

  1. State Pascals Law
    Pressure applied is distributed equally to all areas of a non compressible fluid.

    Strictly speaking only true if nothing moves
  2. Pressure force equation
    Image Upload 1

    Force = Pressure x Area
  3. Work equation
    Work = MAD

    Work = Force x Distance
  4. what is a key quality of hydraulic fluid
    Incompressible through it's entire range of approved operating pressures.

    Any work done compressing the fluid is wasted
  5. Mineral or Petroleum based fluids show what characteristics
    • Red in Colour
    • Smell like penetrating Oil
    • Used with Synthetic rubber, leather, or metal seals
    • Disadvantage is flammability!
    • Corrosive to natural rubber
    • DTD 585 UK
    • MIL-H-5606 USA
  6. Vegetable based Fluid
    • Caster Oil & Alcohol
    • Older types of A/C
    • Smells like alcohol
    • Coloured Blue
    • Used with Natural rubber seals
    • Disadvantage is flamability
  7. Synthetic fluids
    • Used in high performance A/C 
    • High Temp Range -55 +105
    • SkyDrol 500B and LD
    • Purple in Colour
    • fire resistant
    • seals are Silicon, flourocarbon, or butyl
    • Attacks PVC and wire insulation
    • systems must be sealed due to water and atmospheric contaminants
  8. What is the name of the pipe that stands proud in the Reservoir so fluid will stop feeding the power pump in the event of a leak but still leave fluid for the hand pump
  9. What pressure are pressurized systems?

    Why are they pressurized?

    How are they pressurized?
    typically 10psi, up to 30psi in high demand high alt situations

    stops cavitation and in low pressure environments

    From bleed air from engine compressor
  10. Spur Gear pumps are for what volume and pressures
    Medium fluid volume

    up to approx 1500psi
  11. Name the 2 types of constant displacement pumps
    Vane type

    Spur Gear
  12. Variable displacement pumps are used for what type of system

    What does this system need?
    Constant Pressure, live line systems

    Bypass valve to prevent over-pressurizing if pump fails to stop delivering when it should
  13. What is the common type of variable displacement pump?
    Axial swash plate pump.
  14. What is a variable pump said to be doing when it is delivering no fluid
    State if idling
  15. When will a hand pump be used?
    • in emergency situations
    • to allow ground servicing without engine runup, such as
    • pressure joints and lines can be tested
    • cargo doors etc opened

    Pump is normally double acting
  16. Purpose of Cut out valve
    In a constant pressure system, to return fluid to the reservoir when the required line pressure is achieved
  17. what does a short interval of a cut out valve indicate?
    A possible leak in the system

    Or if the accumulator gas pressure is too high it wont store much fluid and so it is exhausted quickly and cuts in the valve again.
  18. What does a "too low" gas pressure in an accumulator cause?
    No longer serves its function of "dampening" the system, so gets a knocking noise "Hammering"
  19. Purpose of a thermal relief valve
    To relive high pressure caused by thermal expansion in a trapped part of the system (between a non-return valve and a piston for example)

    Operates at higher pressures than normal pressure relief valves in the system
  20. where is the shut off valve in the system
    Between Reservoir and pump

    for ground servicing, and to isolate in the event of an engine fire.
  21. Purpose and uses of Hydraulic Fuse
    To stop fluid loss downstream when a leak occurs. Operate when pressure drop across the fuse exceeds a limit.

    • Braking
    • Flaps
    • Thrust reverse
Card Set
Systems 3 Hydraulics